Дисертації з теми "LiMn204"
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1
Hjelm, Anna-Karin. "Kinetic investigation of LiMn2O4 for rechargeable lithium batteries." Doctoral thesis, KTH, Chemical Engineering and Technology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3429.
Анотація:
This thesis is concerned with kinetic characterisation of theinsertion compound LiMn2O4, which is used as positive electrodematerial in rechargeable lithium batteries. Three different typesof electrode configurations have been investigated, namely singleparticles, thin films and composite electrodes. Differentelectrochemical techniques, i.e. linear sweep voltammetry (LSV),electrochemical impedance spectroscopy (EIS), potential step, andgalvanostatic experiments were applied under various experimentalconditions. The majority of the experimental data were analysedby relevant mathematical models used for describing the reactionsteps of insertion compounds.
It was concluded that a model based on interfacialcharge-transfer, solid-phase diffusion and an external iR-dropcould be fairly well fitted to LSV data measured on a singleelectrode system over a narrow range of sweep rates. However, itwas also found that the fitted parameter values vary greatly withthe characteristic length and the sweep rate. This indicates thatthe physical description used is too simple for explaining theelectrochemical responses measured over a large range of chargeand discharge rates.
EIS was found to be a well-suited technique for separatingtime constants for different physical processes in the insertionand extraction reaction. It was demonstrated that the impedanceresponse is strongly dependent on the current collector used.According to the literature, reasonable values of theexchange-current density and solid-phase diffusion coefficientwere determined for various states-of-discharge, temperatures andelectrolyte compositions. Experiments were carried out in bothliquid and gel electrolytes. A method which improves thedistinction between the time constants related to thematerials intrinsic properties and possible porous effectsis presented. The method was applied to composite electrodes.This method utilises, in addition to the impedance responsemeasured in front of the electrode, also the impedance measuredat the backside of the electrode.
Finally, the kinetics of a composite electrode was alsoinvestigated by in situ X-ray diffraction (in situ XRD) incombination with galvanostatic and potentiostatic experiments. Noevidence of lithium concentration gradients could be observedfrom XRD data, even at the highest rate applied (i.e. ~6C), thusexcluding solid-phase diffusion and also phase-boundary movement,as described by Ficks law, as the ratelimiting step.
Key words:linear sweep voltammetry, electrochemicalimpedance spectroscopy, potential step, in situ X-raydiffraction, microelectrodes, electrode kinetics, LiMn2O4cathode, rechargeable lithium batteries
2
Hlongwa, Ntuthuko Wonderboy. "Thermochemical Storage and Lithium Ion Capacitors Efficiency of Manganese-Graphene Framework." University of the Western Cape, 2018. http://hdl.handle.net/11394/6458.
Анотація:
Philosophiae Doctor - PhD (Chemistry)Lithium ion capacitors are new and promising class of energy storage devices formed from a combination of lithium-ion battery electrode materials with those of supercapacitors. They exhibit better electrochemical properties in terms of energy and power densities than the above mentioned storage systems. In this work, lithium manganese oxide spinel (LiMn2O4; LMO) and lithium manganese phosphate (LiMnPO4; LMP) as well as their respective nickel-doped graphenised derivatives (G-LMNO and G-LMNP) were synthesized and each cathode material used to fabricate lithium ion capacitors in an electrochemical assembly that utilised activated carbon (AC) as the negative electrode and lithium sulphate electrolyte in a two-electrode system. The synthetic protocol for the preparation of the materials followed a simple solvothermal route with subsequent calcination at 500 - 800 ?C. The morphological, structural and electrochemical properties of the as prepared materials were thoroughly investigated through various characterisation techniques involving High resolution scanning electron microscopy (HRSEM), High resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), Small-angle X-ray scattering (SAXS), Electrochemical impedance spectroscopy (EIS), Cyclic voltammetry (CV) and Galvanostatic charge/discharge.
2021-12-31
3
Fujita, Miho, Takashi Hibino, Takayuki Hattori, and Mitsuru Sano. "Improved LiMn2O4/Graphite Li-Ion Cells at 55°C." The Electrochemical Society, 2007. http://hdl.handle.net/2237/18460.
4
Eriksson, Tom. "LiMn2O4 as a Li-ion Battery Cathode. From Bulk to Electrolyte Interface." Doctoral thesis, Uppsala universitet, Institutionen för materialkemi, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1397.
Анотація:
LiMn2O4 is ideal as a high-capacity Li-ion battery cathode material by virtue of its low toxicity, low cost, and the high natural abundance of Mn. Surface related reactions and bulk kinetics have been the major focus of this work. The main techniques exploited have been: electrochemical cycling, X-ray diffraction, X-ray photoelectron spectroscopy, infrared spectroscopy and thermal analysis. Interface formation between the LiMn2O4 cathode and carbonate-based electrolytes has been followed under different pre-treatment conditions. The variables have been: number of charge/discharge cycles, storage time, potential, electrolyte salt and temperature. The formation of the surface layer was found not to be governed by electrochemical cycling. The species precipitating on the surface of the cathodes at ambient temperature have been determined to comprise a mixture of organic and inorganic compounds: LiF, LixPFy (or LixBFy, depending on the electrolyte salt used), LixPOyFz (or LixBOyFz) and poly(oxyethylene). Additional compounds were found at elevated temperatures: phosphorous oxides (or boron oxides) and polycarbonates. A model has been presented for the formation of these surface species at elevated temperatures. The cathode surface structure was found to change towards a lithium-rich and Mn3+-rich compound under self-discharge. The reduction of LiMn2O4, in addition to the high operating potential, induces oxidation of the electrolyte at the cathode surface. A novel in situ electrochemical/structural set-up has facilitated a study of the kinetics in the LiMn2O4 electrode. The results eliminate solid-phase diffusion as the rate-limiting factor in electrochemical cycling. The electrode preparation method used results in good utilisation of the electrode, even at high discharge rates.
5
Esaki, Shogo. "Cycle performance improvement of LiMn2O4 cathode material for lithium ion battery by formation of “Nano Inclusion”." Kyoto University, 2016. http://hdl.handle.net/2433/215650.
Анотація:
著作権、出典、利用制限の表示を出版社より求められている。Kyoto University (京都大学)
0048
新制・課程博士
博士(エネルギー科学)
甲第19824号
エネ博第330号
新制||エネ||66(附属図書館)
32860
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)准教授 高井 茂臣, 教授 萩原 理加, 教授 佐川 尚
学位規則第4条第1項該当
6
Silva, João Pedro da. "Síntese assistida por microondas de LiMn2O4, caracterização e testes como catodo para dispositivos de armazenamento de energia." Universidade Federal de São Carlos, 2011. https://repositorio.ufscar.br/handle/ufscar/6492.
Анотація:
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Previous issue date: 2011-03-02Universidade Federal de Sao Carlos
Lithium manganese oxide - LiMn2O4 - was produced by a microwaveassited solid state reaction. Solid mixtures containing LiOH.H2O and -MnO2 (synthesized electrolytically) underwent microwave irradiation for 3, 4 and 5 min. The obtained material was characterized by X-ray diffraction (XRD), scanning electron microscopy and cyclic voltammetry. Conductivity measurements and charge / discharge tests were carried out with the mixture: 85% LiMn2O4 / 10% carbon black / 5% PVDF. XRD analyses showed that LiMn2O4 was obtained in a single phase of cubic structure belonging to the space group Fd3m in only 3 min of microwave irradiation. This short time for the LiMn2O4 synthesis represents an energy saving greater than 90% when compared with the time employed in the traditional method of synthesis. SEM micrographs showed morphological changes and particle size increase when the microwave irradiation time was increased. The mixture (85% LiMn2O4 / 10% carbon black / 5% PVDF) presented electronic conductivity similar to that of a semiconductor (σ ~ 10-1 S m-1), which is adequate for using as cathode in lithium ion battery. Charge and discharge tests showed good electrochemical stability for all the oxides synthesized at different times, evidenced by a small decrease (12 to 17%) of their specific capacities during 30 cycles of charge and discharge. The oxide produced at 3 min of microwave irradiation presented the highest charge supply (77 93 mA h g-1) at an elevated discharge rate (C/1), besides a highly uniform morphology and the lowest particle size (~1 μm).
Óxido de manganês litiado - LiMn2O4 - foi produzido por uma rota de síntese diferenciada, a síntese de estado sólido assistida por microondas. Misturas sólidas contendo LiOH.H2O e -MnO2, sintetizado eletroliticamente, foram irradiadas por microondas durante 3, 4 e 5 min. O material obtido foi caracterizado por difratometria de raios-X (DRX), microscopia eletrônica de varredura (MEV) e voltametria cíclica. Também foram realizadas medidas de condutividade e testes de carga e descarga com a mistura: 85% LiMn2O4 / 10% negro de acetileno / 5% PVDF. As análises de DRX indicaram que LiMn2O4 foi obtido com estrutura cúbica pertencente ao grupo espacial Fd3m em apenas 3 min de irradiação de microondas. O reduzido tempo de síntese do espinélio representa uma economia energética superior a 90%, quando comparado com o tempo empregado no método tradicional de síntese. As micrografias de MEV mostraram alterações de morfologia, bem como aumento no tamanho de partícula conforme é aumentado o tempo de irradiação por microondas. A condutividade eletrônica da mistura (85% LiMn2O4 / 10% negro de acetileno / 5% PVDF) é da ordem daquela de um material semicondutor (σ ~ 10-1 S m-1), adequada para sua utilização como catodo em bateria de íons lítio. Os testes de carga e descarga mostraram que os óxidos obtidos a diferentes tempos apresentam boa estabilidade eletroquímica, com queda de capacidade específica durante 30 ciclos de carga e descarga variando de 12 a 17%. Entretanto, o LiMn2O4 produzido a 3 min por irradiação de microondas apresentou o maior fornecimento de carga (77 93 mA h g-1) quando os óxidos foram testados a uma elevada taxa de descarga (C/1). Além disso, este material destacou-se por apresentar uniformidade morfológica e o menor tamanho de partícula (~1 μm).
7
Rudisch, Christian. "Nuclear Magnetic Resonance on Selected Lithium Based Compounds." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-130485.
Анотація:
This thesis presents the NMR measurements on the single crystals LiMnPO4 and Li0.9FeAs. Therefore, the thesis is divided into two separated sections. The first part reports on the competitive next generation cathode material LiMnPO4 with a stable reversible capacity up to 145 mAh/g and a rather flat discharge voltage curve at 4.1 V. For the basic understanding of the material the magnetic properties have been investigated by a Li and P NMR study in the paramagnetic and antiferromagnetic phase. LiMnPO4 shows a strong anisotropy of the dipolar hyperfine coupling due to the strong local magnetic moments at the Mn site. The corresponding dipole tensor of the Li- and P-nuclei is fully determined by orientation and temperature dependent NMR experiments and compared to the calculated values from crystal structure data. Deviations of the experimentally determined values from the theoretical ones are discussed in terms of Mn disorder which could have an impact on the mobility of the Li ions. The disorder is corroborated by diffuse x-ray diffraction experiments which indicate a shift of the heavy elements in the lattice, namely the Mn atoms. Furthermore, the spin arrangement in the relative strong field of 7.0494 T in the antiferromagnetic state is understood by the NMR measurements. In order to obtain parameters of the Li ion diffusion in LiMnPO4 measurements of the spin lattice relaxation rate were performed. Due to the strong dipolar coupling between the Li-nuclei and the magnetic moments at the Mn site it is difficult to extract parameters which can characterize the diffusive behavior of the Li ions.
The second section reports on the AC/DC susceptibility and NMR/NQR studies on Li deficit samples labeled as Li0.9FeAs. LiFeAs belongs to the family of the superconducting Pnictides which are discovered in 2008 by H. Hosono et al. In recent studies the stoichiometric compound reveals triplet superconductivity below Tc ∼ 18 K which demands ferromagnetic coupling of the electrons in the Cooper pairs. In Li0.9FeAs the Li deficit acts like hole doping which suppresses the superconductivity. Then ferromagnetism can arise which is very interesting because of the vicinity to the triplet superconductivity. With the microscopic methods NMR/NQR on the Li and As nuclei, it was investigated where the ferromagnetism can be located in Li0.9FeAs. Recent susceptibility, ESR and µSR studies reveal an internal field due to the ferromagnetism. In contrast, the internal field could not be used to perform zero field NMR measurements. Possible reasons for this discrepancy are discussed. In addition, the automatic insitu AC susceptibility technique by using the NMR radio frequency circuit has been tested by a reference compound Co2TiGa which shows itinerant ferromagnetism. Similar curves are observed for Li0.9FeAs which indicate the existence of itinerant magnetic moments in Li0.9FeAs. Furthermore, in order to determine the size of the dipolar contribution from the magnetic moments of the Fe the dipolar hyperfine coupling tensor was calculated from the crystal structure data. The comparison of the experimental and calculated hyperfine coupling elements reveals transferred hyperfine fields in LiFeAs.
8
Ibarra, Palos Alejandro. "Nouveaux composés d'insertion du lithium : spinelles dérivés de LiMn2O4, oxydes de manganèse et borates de fer amorphes ; étude fondamentale et applications électrochimiques." Université Joseph Fourier (Grenoble), 2002. http://www.theses.fr/2002GRE10006.
9
Kaibara, Patrícia Silvestre de Oliveira. "Preparação e caracterização de compósitos de polipirrol (LiMn2O2)/ fibra de carbono para catodos em baterias secundárias." Universidade Federal de São Carlos, 2003. https://repositorio.ufscar.br/handle/ufscar/6585.
Анотація:
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Previous issue date: 2003-08-19Universidade Federal de Minas Gerais
Composites of polypyrrol (Ppy) and LiMn2O4 were synthesized chronoamperometrically at 0.8 V (vs. ECS) in 0.1 mol.L-1 LiClO4 /acetonitrile (2% H2O added) electrolyte containing 0.1 mol.L-1 of the pyrrol monomer, on carbon fiber (CF) substrates. The optimum concentration of the oxide in the electrolyte was found as 0.12 g.L-1. Both the previous ultrassonic dispersion of the oxide and the electrolyte mechanic stirring during the synthesis led to the best composite properties. For comparison, other composites were also prepared: Ppy/CF; Ppy(PSS)/CF and Ppy(PSS)/LiMn2O4/CF. Electrochemical stability tests were performed by cyclic voltammetry for all composites, in the electrosynthesis electrolyte without the monomer and water as well as in 0.1 mol.L-1 LiClO4 / propilene carbonate. The morphology, coupled with elemental analysis, and the electrical properties of all composites were obtained, respectively, by SEM/EDS and impedance spectroscopy. The discharge capacity obtained for the Ppy/LiMn2O4/CF composite was 80 mA.h.g-1, about 100% higher than the one for the Ppy/CF composite. The capacity value found for Ppy(PSS)/CF was similar, but the charge/discharge runs presented a slow profile to reach the maximum steady value, which is not interesting for cathode in rechargeable batteries. On the other hand, the Ppy(PSS)/LiMn2O4/CF composite showed the smaller capacity value. Therefore, among all the analyzed composites, the one containing Ppy and LiMn2O4 presented the best performance to be used as cathodes in lithium ion batteries.
Compósitos de polipirrol (Ppy) e LiMn2O4 foram sintetizados cronoamperometricamente a 0,8 V (vs. ECS) em solução de LiClO4 0,1 mol.L-1 / acetonitrila e 2% de H2O, contendo 0,1 mol.L-1 do monômero pirrol, em substratos de fibra de carbono (FC). Determinou-se que a concentração ótima de óxido no eletrólito de eletrossíntese foi de 0,12 g.L-1. Uma prévia agitação ultrassônica do óxido no eletrólito, somada à agitação mecânica do mesmo durante a eletrossíntese favoreceu a dispersão do óxido e conseqüentemente a qualidade do depósito. Outros compósitos foram eletrossintetizados para comparação: Ppy somente; Ppy e poliânion PSS (poliestirenossulfonato de sódio); e um último, contendo Li1,05Mn2O4 além dos dois polímeros. Testes de estabilidade eletroquímica foram realizados via sucessivos ciclos de voltametria cíclica para todos os filmes no eletrólito de eletrossíntese, na ausência do monômero e água, e também em LiClO4 0,1 mol.L-1 / carbonato de propileno. A caracterização morfológica dos compósitos foi realizada através da microscopia eletrônica de varredura, concomitantemente à análise de elementos através da espectroscopia de energia dispersiva; a caracterização elétrica foi realizada por espectroscopia de impedância eletroquímica. A capacidade de descarga obtida para o compósito contendo Ppy e Li1,05Mn2O4 foi 80 mA.h.g-1, cerca de 100 % maior que a do filme de Ppy somente. O valor da capacidade para o compósito contendo Ppy e PSS foi semelhante ao do primeiro, entretanto foram necessários o dobro do número de ciclos de carga/descarga para que se definisse um valor constante de capacidade não sendo, portanto, um comportamento interessante para catodos de baterias; já a capacidade obtida para o compósito contendo Ppy, Li1,05Mn2O4 e PSS foi inferior às anteriores, não havendo a estimada contribuição dos dois dopantes juntos na matriz polimérica. Sendo assim, o compósito Ppy/Li1,05Mn2O4/FC foi o que apresentou as melhores características para uma bateria de íons lítio, indicando que os sítios do óxido mantiveram-se acessíveis para a intercalação dos íons lítio e o polímero funcionou como material ativo e rede condutora para o óxido semicondutor.
10
Luchkin, Sergey Yurevich. "Local probing of Li+ diffusion and concentration in Li-ion battery materials by scanning probe microscopy." Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/14825.
Анотація:
Doutoramento em Ciência e Engenharia de MateriaisThis thesis presents the results of Scanning Probe Microscopy (SPM) study of Li-ion battery active materials. The measurements have been performed on LiMn2O4 cathodes and graphite anodes extracted from commercial Li batteries at different states of charge and health. The study has been focused on measurements of Li spatial distribution and transport properties in the active electrode materials. Special attention has been paid to influence of fatigue caused by high C rate cycling on Li spatial distribution and local diffusion coefficient. Electrochemical Strain Microscopy (ESM) has been used to access Li transport properties at the nanoscale in LiMn2O4 cathodes. Kelvin Probe Force Microscopy (KPFM) has been used to examine Li spatial distribution in graphite anodes. ESM has been implemented and used in a single frequency mode out of the contact resonance for the first time. Signal-to-noise ratio analysis has been performed for a number of single- and multi-frequency modes used in ESM. The analysis allowed to establish criteria for a proper cantilever choice and an experimental setup for the optimized detection of surface displacements via lock-in amplifier. Transport properties of Li+ mobile ions in fresh and fatigued LiMn2O4 battery cathodes have been studied at the nanoscale via ESM using time-and voltage spectroscopies. Both Vegard and non-Vegard contributions to ESM signal have been identified in electrochemical hysteresis loops obtained on the fresh and fatigued samples. In fresh cathodes the Vegard contribution dominates the signal, while in fatigued samples different shape of hysteresis loops indicates additional contributions. Non-uniform spatial distribution of the electrochemical loop opening in LiMn2O4 particles studied in the fatigued samples indicates stronger variation of Li diffusion coefficients in fatigued samples’ as compared to the fresh one. Time spectroscopy measurements have revealed suppressed local Li diffusivity in fatigued samples by more than two orders of magnitude as compared to the fresh one. We attributed such reduction of the diffusion coefficient to the accumulation of point defects induced by high C-rate cycling and accompanied structural instability. This mechanism can be specifically important for high C-rate cycling. Li spatial distribution in fresh and fatigued graphite cathodes has been accessed via KPFM using a 2-pass amplitude modulation mode. Core-shell and mosaic surface potential structures have been observed on the fatigued and fresh anodes, respectively. The observed surface potential distributions have been attributed to the apparent Li concentration profiles in graphite. The core-shell potential distribution has been attributed to the remnant Li ions stacked in graphite particles causing irreversible capacity loss. The mosaic potential distribution has been attributed to inactive Li inside graphite at the starting stage of cycling. The results corroborate the “radial” model used to explain the specific capacity fading mechanism at high C rate cycling in Li-ion batteries.
Esta tese apresenta os resultados do estudo de Scanning Probe Microscopia (SPM) de materiais de baterias de ions de litio. As medidas foram executadas na cátodos de LiMn2O4 e ânodos de grafite extraidos de bateriais de litio comerciais em diferentes estados de carga e fadiga. O estudo concentrou-se na medição da distribuição de Li e propriedades de transporte dos materiais de eletrodo ativo. Especial atencao tem sido dada a influencia do ciclo de fadiga da elevada taxa C na distribuicao especial dos ions de Li e coeficiente de difusao. Microscopia de tensão eletroquímica (ESM) tem sido usada para acessar Li transporte propriedades em nanoescala em cátodos de LiMn2O4. Microscopia de força de sonda Kelvin (KPFM) tem sido usada para acessar a distribuição espacial de Li em anodos de grafite. ESM foi implementada e usada em um modo de única freqüência de ressonância o contato pela primeira vez. Análise de relação sinal-ruído foi feito para um número de monomodo e multimodo usados no ESM. A análise permite estabelecer critérios para um cantilever e uma instalação experimental para a detecção mais sensível de deslocamentos superficiais. Propriedades da mobilidade dos ions de lition em catodos de bateria LiMn2O4 frescos e fatigados foram estudados em nanoescala via ESM, espectroscopia de tempo e espectroscopia de tensão de transporte. Contribuições como sinal Vegard e non-Vegard ESM foram identificadas em ciclos de histerese eletroquímica obtidos em amostras frescas e fatigadas. Em cátodos frescos o sinal Vegard dominante, enquanto em amostras envelhecidas, a diferente ciclo de histerese indica contribuições adicionais. Distribuição espacial não-uniforme do ciclo aberto eletroquímico em partículas de LiMn2O4 foram estudadas nas amostras fatigadas indicando mais forte variação do coeficiente de difusão de Li das amostras fatigadas em microescala em comparação com a outra amostra. Medições de espectroscopia de tempo revelaram a ausencia de difusidade local em amostras fatigadas por mais de duas ordens de magnitude em comparação com a outra. Atribui-se tal redução do coeficiente de difusão o acúmulo de defeitos de ponto induzida pelo Ciclo de elevada taxa C e acompanhadas de instabilidade estrutural. Este mecanismo pode ser especialmente importante para ciclo de elevada taxa C. Distribuição espacial de Li em cátodos amostras fresca e fatigada grafite foi analisaa via KPFM no modo de modulação de amplitude 2-pass. Estruturas de superfícies potenciais core-shell e mosaico têm sido observadas em ânodos fatigados e frescos, respectivamente. As distribuições de superfícies potenciais observadas foram atribuídas para os perfis de concentração Li aparentes em grafite. Distribuição potencial core-shell tem sido atribuída para o ions remanescentes de Li empilhados em partículas de grafite, causando perda irreversível de capacidade. A distribuição de potencial de mosaico tem sido atribuída a Li inativo dentro do grafite na fase inicial do ciclo. Os resultados corroboram o modelo "radial" usado para explicar o mecanismo de desvanecimento de capacidade específica a alta taxa de C em baterias de íon-lítio.
11
Le, Cras Frédéric. "Oxydes Li-Mn-O pour accumulateurs au lithium : synthèses nouvelles, aspects structuraux et électrochimiques." Phd thesis, Université Joseph Fourier (Grenoble), 1996. http://tel.archives-ouvertes.fr/tel-00530193.
Анотація:
Ce mémoire décrit la synthèse, la caractérisation – notamment thermogravimétrique et structurale – et les propriétés d'intercalation électrochimique du lithium de plusieurs types d'oxydes de manganèse. On décrit tout d'abord la préparation d'une 'ramsdellite synthétique', à faible taux de défauts structuraux de type rutile. Les oxydes de manganèse lamellaires (phyllomanganates) ont donné lieu à une nouvelle voie de synthèse du phyllomanganate de lithium par une succession de réactions topotactiques (échanges d'ions) à basse température. Sa stabilité thermique et ses propriétés d'intercalation sont examinées en comparaison avec celles du composé de sodium. La majeure partie de ce mémoire est consacrée aux spinelles Li1+xMn2–xO4, qui sont des matériaux d'électrode positive prometteurs pour les accumulateurs au lithium. Ce travail montre la faisabilité de synthèses à basse température à partir de béta-MnO2 (procédé breveté), et l'existence d'une corrélation entre température de synthèse et composition de la phase spinelle. L'intercalation du lithium est étudiée en électrolyte solide et liquide pour plusieurs compositions. L'emploi d'une cellule électrochimique in situ dans un diffractomètre de rayons X a permis de mettre en évidence le caractère biphasé de l'intercalation, même pour des spinelles de Li:Mn = 0.69. Les performances électrochimiques de spinelles substituées au magnésium et à l'aluminium sont également examinées. L'étude thermogravimétrique des spinelles Li–Mn–O a permis de mettre en évidence des réactions réversibles avec dégagement d'oxygène. Des affinements structuraux à partir de diagrammes de diffraction neutronique mettent en évidence des réactions différentes en fonction de la température d'équilibre, avec apparition de lacunes d'oxygène dans un échantillon trempé à 925°C. Enfin, un nouveau composé appelé "phase m", de formule Li0.25MnO2, a été obtenu à 150°C. Sa caractérisation structurale aux rayons X et par diffraction électronique montre qu'il s'agit d'une phase nouvelle monoclinique avec une sous-structure pseudo-hexagonale proéminente.
12
Malatji, Kemeridge Tumelo. "Computer simulation studies of spinel LiMn2O4 and spinel LiNiXMn2-XO4 (0≤x≤2)." Thesis, 2019. http://hdl.handle.net/10386/3348.
Анотація:
Thesis (Ph.D. (Physics)) -- University of Limpopo, 2019LiMn2O4 spinel (LMO) is a promising cathode material for secondary lithium-ion batteries which, despite its high average voltage of lithium intercalation, suffers crystal symmetry lowering due to the Jahn-Teller active six-fold Mn3+ cations. Although Ni has been proposed as a suitable substitutional dopant to improve the energy density of LiMn2O4 and enhance the average lithium intercalation voltage, the thermodynamics of Ni incorporation and its effect on the electrochemical properties of this spinel are not fully understood. Firstly, structural, electronic and mechanical properties of spinel LiMn2O4 and LiNixMn2-xO4 have been calculated out using density functional theory employing the pseudo-potential plane-wave approach within the generalised gradient approximation, together with Virtual Cluster Approximation. The structural properties included equilibrium lattice parameters; electronic properties cover both total and partial density of states and mechanical properties investigated elastic properties of all systems. Secondly, the pressure variation of several properties was investigated, from 0 GPa to 50 GPa. Nickel concentration was changed and the systems LiNi0.25Mn1.75O4, LiNi0.5Mn1.5O4 LiNi0.75Mn1.25O4 and LiNi0.875Mn1.125O4 were studied. Calculated lattice parameters for LiMn2O4 and LiNi0.5Mn1.5O4 systems are consistent with the available experimental and literature results. The average Mn(Ni)-O bond length for all systems was found to be 1.9 Å. The bond lengths decreased with an increase in nickel content, except for LiNi0.75Mn1.25O4, which gave the same results as LiNi0.25Mn1.75O4. Generally, analysis of electronic properties predicted the nature of bonding for both pure and doped systems with partial density of states showing the contribution of each metal in our systems. All systems are shown to be metallic as it has been previously observed for pure spinel LiMn2O4, and mechanical properties, as deduced from elastic properties, depicted their stabilities. Furthermore, the cluster expansion formalism was used to investigate the nickel doped LiMn2O4 phase stabilities. The method determines stable multi-component crystal structures and ranks metastable structures by the enthalpy of formation while iv maintaining the predictive power and accuracy of first-principles density functional methods. The ground-state phase diagram with occupancy of Mn 0.81 and Ni 0.31 generated various structures with different concentrations and symmetries. The findings predict that all nickel doped LMO structures on the ground state line are most likely stable. Relevant structures (Li4Ni8O16, Li12MnNi17O48, Li4Mn6Ni2O16, Li4Mn7NiO16 and Li4Mn8O16) were selected on the basis of how well they weighed the cross-validation (CV) score of 1.1 meV, which is a statistical way of describing how good the cluster expansion is at predicting the energy of each stable structure. Although the structures have different symmetries and space groups they were further investigated by calculating the mechanical and vibrational properties, where the elastic constants and phonon vibrations indicated that the structures are stable in accordance with stability conditions of mechanical properties and phonon dispersions. Lastly, a computer program that identifies different site occupancy configurations for any structure with arbitrary supercell size, space group or composition was employed to investigate voltage profiles for LiNixMn2-xO4. The density functional theory calculations, with a Hubbard Hamiltonian (DFT+U), was used to study the thermodynamics of mixing for Li(Mn1-xNix)2O4 solid solution. The results suggested that LiMn1.5Ni0.5O4 is the most stable composition from room temperature up to at least 1000K, which is in excellent agreement with experiments. It was also found that the configurational entropy is much lower than the maximum entropy at 1000K, indicating that higher temperatures are required to reach a fully disordered solid solution. The maximum average lithium intercalation voltage of 4.8 eV was calculated for the LiMn1.5Ni0.5O4 composition which correlates very well with the experimental value. The temperature has a negligible effect on the Li intercalation voltage of the most stable composition. The approach presented here shows that moderate Ni doping of the LiMn2O4 leads to a substantial change in the average voltage of lithium intercalation, suggesting an attractive route for tuning the cathode properties of this spinel.
National Research Foundation (NRF)
13
Chen, Yi-Shiang, and 陳宜祥. "Lithiated ionomer binder modified LiMn2O4 Cathode." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/237287.
Анотація:
碩士逢甲大學
材料科學所
100
Perfluorosulfonic acid (Nafion) solution as a polymer binder for lithium ion batteries has been investigated. Lithiated Nafion (Li+Nafion) ionomer have been used to replace the commercial adhesive PVdF. The Li+Nafion solution have been formed by a lithium ion exchange procedure to be the lithium-contained intelligent binder. The Li+Nafion solution is characterized by Fourier transform infrared spectroscopy. Powder cathodes fabricated by mixing LiMn2O4 powder, carbon black and binders have been investigated. The cathodes with conventional PVDF and Li+Nafion are tested and compared separately. These LiMn2O4 electrodes are characterized using Scanning electron microscopy, Energy dispersive spectrometer, X-ray diffraction, Raman spectroscopy. The electrochemical performances are measured by cyclic voltammetry and charge-discharge cycle tests. In the long term cycling tests, Li+Nafion electrodes show a stable cycle stability as well as PVdF electrodes. The results reveal that the capacities of Li+Nafion-type LiMn2O4 electrode show an better high-rate capacity 70 mAh/g than PVDF-type LiMn2O4 electrode (45 mAh/g) at 10 C. The enhanced high-rate performance of Li+Nafion-type LiMn2O4 electrode is attributed to the intelligent binder with Li-ion conductivity. The charge transfer resistances of the LiMn2O4 electrodes decreases 41 % due to the increased lithium ion concentration around the surface of the active materials by the Li+Nafion ionomer binder.
14
Wang, Chun-Chieh, and 王俊傑. "A microstructure analysis of pressureless sintered LiMn2O4 spinel." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/49226378925625960665.
Анотація:
碩士國立中山大學
材料科學研究所
92
The spinel structure of LiMn2O4 powders react with the 1 mole Li2CO3 and 4 mole MnO2 powders by solid-state reaction at 800 oC, and then sintered at 1300 oC to become ceramics specimen. There are accompany phase transformation and non-stoichiometric composition during the cooling process. In X-ray diffraction analysis, the sintered specimen contains principal Li-deficiency Li1-XMn2O4 composition and minor of second phases LiMnO2 and Mn3O4. Lattice parameters also distorted by John-Teller effect. In electron microscopy observation, there are lamellae grains and defects in the specimen, such as twins, dislocations and stacking faults. In TEM analysis, tetragonal-LiMn2O4 structure has lamellae domains, and reflection twinning. However, this study for cubic-LiMn2O4 structure found that edge dislocations with Burger vector of 1/2<110> slip on {110} plane, and mixed(45o) dislocation with Burger vector of 1/2<100> slip on {100} plane.
15
Tshwane, David Magolego. "Computer simulation studies of MnO2 and LiMn2O4 nanotube." Thesis, 2016. http://hdl.handle.net/10386/1788.
Анотація:
Thesis (MSc. (Physics)) -- University of Limpopo, 2016Nanostructured materials are attractive candidates for efficient electrochemical energy storage devices because of their unique physicochemical properties. Introducing nanotube systems as electrode materials represents one of the most attractive strategies that could dramatically enhance the battery performance. Nanostructured manganese based oxides are considered as ideal electrode materials for energy storage devices such as high energy and high power lithium-ion batteries. In this study, computer simulation strategies were used to generate various structures of MnO2 and spinel LiMn2O4 nanotubes; where Miller index, diameter and symmetry are considered as variables. The effect of these variables on nanotube generation was investigated. MnO2 and spinel LiMn2O4 nanotubes were generated using MedeA® software. Lower Miller indices, namely; {001}, {100}, {110} and {111} with diameter ranging from 5Å30Å were investigated for both systems. There are two ways that a nanotube structures could be wrapped along different directions, i.e., a_around_b or b_around_a. It was observed that wrapping direction has an effect on the geometrical structure of the nanotube. MnO2 nanotube generated from {110} revealed that nanotube wrapped along b_around_a gave a close-packed structure compared to its counterpart nanotube wrapped a_around_b. Diameter represents an important structural parameter of nanotubes; however, precise control of nanotube diameter over a wide range of materials is yet to be demonstrated. In this study, it was found that as the diameter of the nanotube is changed, parameters such as cross-sectional area and bond length change as well. The average bond distance of the nanotubes is less than that of MnO2 and LiMn2O4 bulk structure. Molecular dynamics simulation is further used to investigate the structure of MnO2 and LiMn2O4 nanotubes and the effect of temperature on the generated systems. Molecular graphical images used for the atomic positions for the nanotubes were investigated. The nanotube structures are described using radial distribution functions and XRD patterns. The calculated XRD patterns are in good agreement with the experiments, thus validating the generated structural models for the nanotubes. The resulting models conform to pyrolusite polymorph of MnO2 and LiMn2O4, featuring octahedrally coordinated manganese atoms. It was established that the variables have a direct control on nanotube morphology and the stability of generated nanotube model depends on surface morphology and termination.
National Research Foundation (NRF) and Centre for High Performance Computing (CHPC) of CSIR
16
Liu, Ming-Cheng, and 劉明錚. "Development of the positive electrode material by LiMn2O4 Series." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/85604943135207524976.
Анотація:
碩士吳鳳科技大學
光機電暨材料研究所
99
The thesis with Li2CO3 and Mn3O4 through the solid-state reaction makes positive electrode material for lithium battery spinel - LiMn2O4. According to past literature, under the solid-state reaction, sintering temperature for LiMn2O4 was at about 800℃-900℃ which is the best temperature. The experiment carries out sintering at temperature of 820℃, 825℃, 830℃, 840℃, 850℃, 860℃, 870℃, 875℃ and 900℃ separately. Positive electrode materials under these sintering temperatures are made to fabricate battery. At normal temperature, 850℃ shows the highest initial discharge capacity at 105.19mAh/g (theoretically at 148 mAh/g). The result of experiment demonstrates that the best sintering temperature is at 850℃. Under the condition of 850℃, various contents for extra amount of lithium (1.02 mole-1.1 mole) are fabricated and range of working voltage is released. It is found a further increase of initial capacity to 140.51mAh/g. At the later phase of experiment, various moles of Ni from 0.1, 0.3, 0.5, 0.7 to 0.9 are separately mixed to make LiNiXMn2-XO4 to vary initial charge-discharge capacity and circulation. From the experiment result, it is known that mixing too much Ni leads to a structure of impurity LixNi1-xO2. Such impurity shows no reaction when being added to lithium-ion battery which affects charge-discharge and circulation of material. Mixing 0.5mole of Ni has better circulation. Consumption of 15 circulations is 0.53% which is much less than purity LiMn2O4 (15.68% of consumption). LiNi0.5Mn1.5O4 mixed with 0.5mole of Ni further extends circulation and usage.
17
Wang, Shu Hui, and 王淑慧. "Preparation and Characteristics Study of LiMn2O4 / Polyimide Hybrid Film." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/07827113690258296745.
Анотація:
碩士國立交通大學
材料科學與工程系
89
Two series of metal containing poly(amic acid)s, precusors of LiMn2O4 / Polyimide hybrid films, were derived from pure PAAs and Li and Mn acetylacetone. The pure PAAs were prepared with ODPA (4,4- oxydiphthalic anhydride) and ODA (4,4''-diaminodiphenylether), or ODPA and p-BAPB (1,3-bis(4-aminophenoxy)benzene). The metal-containing PAAs were converted to LiMn2O4 / Polyimide hybrid films by step thermal imidization: at 100℃, 200℃,and 250℃each for 1hr, and 300℃ for 6hr or 10hr . In these conditions, LiMn2O4 could successfully be sintered in polyimides at low temperatures in one process. The LiMn2O4 / Polyimide hybrid films were characterized with the X-ray diffraction spectrum (XRD). In the two series of the hybrid films, IR figures showed the intensities of Mn-O vibration bands(615, 515 cm-1) enhanced with increasing process temperature, process time, and Li and Mn acetylacetone contents. It represented the hybrid films having more crystalline LiMn2O4 phase under these conditions. TGA profiles showed Tds decreased with increasing process time and metal acetylacetone contents. The results might be related to the metal oxide catalyzing the oxidative degradation reaction and decreasing the thermal stability of hybrid films. Conductivities of the hybrid films could be up to ~10-11 Ω-1 cm-1, which were 1~3 orders higher than that of pure polyimide. SEM pictures of the hybrid films cross sections showed the metal oxide sizes increase with increasing metal acetylacetone contents, but they were smaller than that with the solid state method.
18
Cho, Yung-Da, and 卓永達. "Nanocrystalline LiMn2O4 Derived by HMTA-Assisted Solution Combustion Synthesi." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/59968018874729829648.
Анотація:
碩士國立中央大學
化學工程與材料工程研究所
92
This dissertation covers the synthesis and lithium-intercalating properties of LiMn2O4 prepared by a combustion process with ammonium nitrate as a porogenic agent and Hexamethylenetetraamine (HMTA) as a fuel. The synthesis parameters, temperature and duration of calcination and lithium stoichiometry, as well as metal ion：fuel mole ratio, were optimized in order to obtain products with the best electrochemical activity. The phase transitions of the products were investigated by thermogravimetric and differential thermal analyses, Structural properties of the products were investigated by X-ray diffraction, surface morphology by scanning electron microscopy and transmission electron microscopy, and surface area by the BET method. Lithium intercalation properties were studied by galvanostatic charge-discharge studies for different rate windows. The various redox regions and phase changes occurring during the charge-discharge processes were studied by cyclic voltammetry. The precursors for the synthesis of LiMn2O4 were metal nitrates dissolved in an aqueous solution of ammonium nitrate and HMTA in various mole ratios of total metal ion to fuel and the products were obtained by calcination at different temperatures and times. The optimal synthesis conditions were found to be 10h calcination at 700°C with lithium stoichiometry and mole ratio of total metal ion to fuel at 1.00. At a 0.1 C rate between 3.0 and 4.3 V, the product gave a first-cycle discharge capacity of 113 mAh/g, which faded to 88 mAh/g in the 200th cycle, with charge retention of 80%. The weight loss that occurs in the range from room temperature to about 120°C is ascribed to superficial water loss, as well as water loss from the hydration of manganese nitrate tetrahydrate, which begins to decompose at temperatures above 100°C. The sharp endotherm at 255°C is due to the melting of LiNO3. The main decomposition and product formation begin around 300°C. All the diffractograms show patterns corresponding to the cubic spinel structure in the Fd3m space group, suggesting that LiMn2O4 was formed during the initial decomposition of the mixture at 500°C itself. The particles were crystalline and had an average particle size of 10 ~ 40 nm, and a BET surface area of about 3.0361 m2/g. The good electrochemical behavior of the product was attributed to the nanocrystalline LiMn2O4 cathode particles by a modified solution combustion process.
19
Liao, Hung-Chi, and 廖宏奇. "Surface Modification on Charge-Discharge Capacity of LiMn2O4 Electrode Material." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/15222930699720890605.
Анотація:
碩士國立成功大學
材料科學及工程學系碩博士班
93
Spinel phase LiMn2O4 has been considered to replace LiCoO2 cathode material for lithium-ion rechargeable batteres because of its lower cost, high energy density and lower toxicity. The purpose of this study is to enhance the capacity by using the Pechini process and decrease the capacity fading effectively by surface modification of LiMn2O4 cathode material. Using Pechini process through the continuous stove heat treatment has been developed to synthesize LiMn2O4 powders. For the purpose to acquire completely LiMn2O4 powders, a post heat treatment should be performed. The powders (LMO800) with post heat treatment have superior discharge capacity. Through analyzing by XRD and manganese valence titration, it could be found that an increase in the crystallinity of the LiMn2O4 powders and manganese average valence of powders close to 3.5 after post heat treatment. The initial discharge capacity may be related to the crystallinity of the powders and manganese valence. In this study, the surface of LiMn2O4 (LMO800) was covered with lithium nickel manganese oxide prepared by the Pechini process. After 50 cycles at 25℃, the bare LiMn2O4 showed 88% of the initial discharge capacity and surface-modified LiMn2O4 showed 95% of the initial discharge capacity. After 50 cycles at 55℃, the bare LiMn2O4 showed only 70% of the initial discharge capacity and surface-modified LiMn2O4 showed 94% of the initial discharge capacity. Thus, electrochemical performance of the LiMn2O4 can be improved by the surface modification with Li-Ni-ion. This action improves cyclability for lithium battery performance and reduces capacity fades of LiMn2O4 at elevated temperatures. Through analyzing by ICP, XPS and EDS, it can be explained by suppression of Mn dissolution in the electrolyte.
20
Hong-Wei, Chan. "Surface Modification of LiMn2O4 Cathode Material in Li-ion Secondary Battery." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0016-1303200709465750.
21
Sung, Wei-Cheng, and 宋煒晟. "Synthesis And Electrochemical Characterizations Of Nanostructured LiMn2O4 For Lithium-Ion Battery." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/34577928761433815295.
Анотація:
碩士輔仁大學
化學系
98
Porous (P-) and dense (D-) nano-structured lithium manganese oxide (LiMn2O4) powders have been synthesized by carbonate and hydroxide co-precipitation, respectively. Electrochemical testing results at room temperature showed that discharge capacities of P-LiMn2O4 are 121 and 55 mAh g-1 at discharging rates of 0.1 and 10C, respectively. The corresponding values for D-LiMn2O4 are 119 and 38 mAh g-1. EIS analysis showed that the Li-ion diffusion coefficient of P-LiMn2O4 electrode film (9.0x10-13 cm2 s-1) is much higher than that of D-LiMn2O4 electrode film (3.0x10-13 cm2 s-1), which was attributed to the higher surface area and shorter path for Li-ion diffusion in the P-LiMn2O4. The Re+Rct of D-LiMn2O4 (19.4Ω) at 4.20V is little lower than that of P-Li Mn2O4 (24.4Ω) due to better electric-connection between primary particles. These observations reveal that the porous nanostructure of P-LiMn2O4 improved the high-rate performance, which could be predominated by Li-ion diffusion.
22
Chiang, Hao-yang, and 江皓洋. "High rate performances of plasma assisted sol-gel synthesized LiMn2O4 cathodes." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/87798340554478100035.
Анотація:
碩士逢甲大學
材料與製造工程所
99
Nano-crystalline LiMn2O4 thin films have been synthesized by the sol-gel process at low temperature (350 ℃). The low temperature prepared films are treated by a DC pulsed oxygen plasma. The LiMn2O4 thin films have been tested as cathodes for lithium batteries. The plasma treated films show unexpected high rate stability. They are able to sustain significant high current charge-discharge cycles, and show high Coulomb efficiency. After 110 continuous cycles in various ranges between 0.2-45 C, the final Charge-discharge cycle at 0.2 C can still retain 95 % of initial capacity. The 10 C-rate capacity is 65 % of 0.2 C-rate, which satisfies the requirement of electric vehicles. In addition, the low synthesis temperature saves thermal budget and can be applied on glass or polymer substrates. The stable high rate performances can be attributed to the formation of a dense sub-surface microstructure that induced by the plasma irradiation. The formation of the sub-surface microstructure results in the more uniform current distribution on the film surface, which decreases the interface charge transfer resistances as measured by the electrochemical impedance spectra. Keyword: LiMn2O4, high C-rate, oxygen plasma, lithium battery
23
Chiang, Ming-Hsing, and 江明興. "Transmission electron microscopic analysis of LiMn2O4 cathodes for thin film batteries." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/11793988473985651554.
Анотація:
碩士逢甲大學
材料與製造工程所
96
Recently portable electronic products have seen in the 3C major stores, such as: mobile phones, notebook computers, and digital cameras and so on, their sizes become smaller and smaller, and the weight is lighter and lighter, so the products in carrying on have increased substantially. Because the lithium ion batteries have high energy density and good performance of the cycle, they were widely used in various electronic products as power supply. In order to the trend of the products that can be carried , the designs of a new generation of batteries need to fit in with the principles about light , thin, and short. Therefore, making the thin film lithium ion batteries will become an inevitable trend. At present, the major cathode materials of the lithium ion batteries are LiCoO2, LiNiO2, and LiMn2O4, and LiMnO4. Due to the low-cost and the high safety so it has become the most potential cathode material, but the cathode material of LiMn2O4 still has some problems about making to need to be overcome. In addition, the solid-state thin film lithium batterie size has been reduced to sub-micron; therefore, the film batteries in the analysis of the various materials produce a lot of difficulties, so it must find an effective analytic way to LiMn2O4 cathode material get the best improvement in making. This study in the semiconductor analysis found an effective analysis methods of the film battery that using the focus ion beam (FIB) and transmission electron microscope (TEM) succeeds in analyzing LiMn2O4 cathode material properties and using the results of the material analysis to confront the electrical testing results succeed in founding the important impact of LiMn2O4 thin lithium batteries made.
24
Lo, Shao-hua, and 羅劭華. "Low temperature synthesized LiMn2O4 cathode for solid-state lithium polymer batteries." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/32gwnx.
Анотація:
碩士逢甲大學
材料科學所
100
SPEEK (Sulfonated poly ether ether ketone) has beem used as solid state electrolyte of all solid state polymer lithium ion batteries, and LiClO4 is added to enhance the ion concentraition. A novel plasma treatment technique has been applied on LiMn2O4 cathode materials, to reduce the interface resistance between cathode and electrolyte. The interface behavior is between cathode and electrolyte are characterized by using X-ray diffraction (XRD)、scanning electron microscopy (SEM)、energy dispersive spectrometer (EDS) and Raman spectrometer(Raman). The charge transfer resistant between cathode and electrolyte is analyzed by electrochemical impedance spectroscopy (EIS). All solid-state polymer lithium ion batteries have been fabricated using LiClO4 contented SPEEK electrolyte and plasma treated LiMn2O4 cathode. The electrochemical characteristics are investigated by cyclic voltammetry and charge-discharge cycle tests. The results show that the capacities of cells are increased by adding appropriate amount of LiClO4 into SPEEK, and the charge transfer resistance decreases with oxygen plasma treatment time. The best performance of the all solid state polymer lithium ion battery is 52 μAh/cm2 with the commercial TiO2 anode.
25
Wu, Shang-En, and 吳尚恩. "Mechanism for the synthesis of LiMn2O4 cathode material using citrate route." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/5bmye3.
Анотація:
碩士國立成功大學
材料科學及工程學系碩博士班
90
Modified citrate routes were used to prepare nanocrystalline spinel lithium manganese oxides LiMn2O4 as the cathode materials for lithium ion batteries. Adjusting the pH of precursor solutions containing citric acid (CA), ethylene glycol (EG), and lithium and manganese ions makes the formation of LiMn2O4 much easier, which in turn improves the electrochemical performance of the resultant LiMn2O4 powders. To understand the effect of pH on the interactions between cations and CA, C13 NMR and Raman spectra were used to characterize the precursor solution. The spectra have shown that CA coordinated only to manganese ions in the Li/Mn/CA/EG solution, and lithium ions didn’t cause any effect on CA. With the adjustment of pH, the interactions between CA and manganese ions changed monotonically.
26
Lin, Fang-Ju, and 林芳如. "Characterization of LiMn2O4/LiClO4/Cu for Lithium-Ion Thin-Film Battery." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/09136877685321897331.
Анотація:
碩士國立中興大學
材料科學與工程學系所
98
Using copper (Cu) substitute for replacing conventional metallic Li, thin-film lithium-ion batteries LiMn2O4/LiClO4/Cu were prepared of. They were further characterized by X-ray diffraction (XRD), FE-SEM, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and charge-discharge cyclic tests. The LiMn2O4 film surface morphology was uniform by FESEM observations. XPS analysis showed that lithium content on the copper foil the first cycle charging was 8.3%. The CV measurement showed oxidation peaks at 2.59, 2.85, 3.34 and 3.60 V, and reduction peaks at 3.15, 2.15 and 1.21 V. The first discharge capacity was 40mAh/g and degraded to 17mAh/g at 20th cycle at current density 10μA/cm2. Compared with Li metal anode, Cu was oxidized into CuO by LiClO4 strong oxidizer (Cu+ClO4→CuO+ClO3 ). During the charging, the reduction of Li+ was partially replaced by the reduction of Cu (CuO+2Li++2e-→Cu+Li2O ), therefore, resulting in the loss of capacity. Selecting a metal anode which will not be oxidized by the electrolyte could improve the reversible capacity.
27
Chan, Hong-Wei, and 詹宏偉. "Surface Modification of LiMn2O4 Cathode Material in Li-ion Secondary Battery." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/46774962150453670583.
Анотація:
博士國立清華大學
材料科學工程學系
95
The surface-modified cathode material in Li-ion battery was synthesized to decrease the side reactions at the interface between the cathode electrode and electrolyte. Among all cathode materials, LiMn2O4 exhibits lower cost, acceptable environmental characteristics and better safety property than other cathode materials. The research focus is aimed to reduce the capacity fading and to enhance the electrochemical performance of spinel LiMn2O4, particularly at high C rate. In this study, the microstructure and electrochemical property in the surface-modified LiMn2O4 were examined and probed. The Li2O-2B2O3 (LBO)-coated LiMn2O4 and LiCuxMn2-xO4-coated LiMn2O4 were synthesized by either solid-state method or chemical solution method. From the cross section view of LiCuxMn2-xO4-coated LiMn2O4 and LBO-coated LiMn2O4 observed with FE-SEM, it was demonstrated that the lager particles consisted of many smaller ones in the sub-micrometer range. It was argued that LiCuxMn2-xO4-coated LiMn2O4 and LBO-coated LiMn2O4 exhibited two distinct types of surface modification on the basis of the detailed analysis of HRTEM. In addition, the location of Cu in spinel LiCuxMn2-xO4-coated LiMn2O4 was at 16d site revealed by HRTEM. In addition, the electrochemical behavior was examined by using two-electrode coin cells. First of all, the capacity fading can be reduced by the technique of surface modification. The 0.4 wt％ LBO-coated km110 powder retained 93％ of its original discharge capacity after 10 cycles. Furthermore, the capacity fading of 0.3 wt％ LBO-coated Li1+xMn2O4 cathode material was 7％ after 20 cycles, showing much better cycleability than the un-coated one of 15％. The resistance of the LBO-coated Li1+xMn2O4 was also smaller than the un-coated one, indicating that the side reaction at the interface between the cathode and electrode could be diminished. Besides, for the LiCuxMn2-xO4-coated LiMn2O4, the fading rate of LiMn2O4 at 0.2 C was reduced 2.25％ after 10 cycles by surface modification. At higher C rate of 0.5 C, the decrease of fading rate was more obvious at 5.16％ after 25 cycles. The phase transformation of both base LiMn2O4 and LiCuxMn2-xO4-coated LiMn2O4 during charging at 0.1 C, 0.5 C and 1C rate from 3 V to 4.5 V was confirmed by the in situ synchrotron X-ray diffractometer (in situ XRD). The plateau potential difference between the base LiMn2O4 and LiCuxMn2-xO4-coated LiMn2O4 composite was 50 mV. The decrease of the plateau can be related to the fact that the kinetics of the LiCuxMn2-xO4-coated LiMn2O4 composite cathode material was faster than that of the uncoated material. The XANES of Cu and Mn K-edge spectrum for LiCuxMn2-xO4-coated LiMn2O4 showed that the valence of Cu and Mn was close to Cu2+ and Mn4+, respectively. Furthermore, the oxidation state of Mn was reversibly increased and decreased during charge. The EXAFS was further revealed that the trend of the variation for the bonding length of Mn-O and Mn-M (M=Mn or Cu) was in agreement with the oxidation state of Mn, which was decreased with Li deintercalation, while increased with Li intercalation during cycling. On the basis of the in situ XAS data, it was evidenced that Mn transferred toward Mn4+ to minimize the Jahn-Teller distortion by the technique of surface modification, and thus the better electrochemical property was achieved.
28
Huang, Chiou-Ping, and 黃秋萍. "Studies on Surface Modification of LiMn2O4 Cathode Materials by Cobalt Compound." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/29115922665457726998.
Анотація:
碩士國立臺灣科技大學
化學工程系
89
The purpose of this study is to enhance the capacity and decrease the capacity fading effectively by surface modification of LiMn2O4 cathode material. Commercial LiMn2O4 is chosen as the core cathode material for surface modification. To modify the surface, first LiMn2O4 powder is added to the solution of K3[Fe(CN)6]. During stirring the K3[Fe(CN)6] is chemisorbed on the surface of the LiMn2O4. Then, Co(NO3)2 is added to the above solution to form potassium-cobalt-cyanide complex on the surface of the LiMn2O4 powder. The cobalt is diffused deeply into the LiMn2O4 particle with increasing sintering temperature. The amount of cobalt presented on the surface of the LiMn2O4 powder is analyzed by ESCA and the overall composition is evaluated by ICP-AES measurements. It is found that the cobalt content on the surface is more than in the structure. From SEM measurements the sintering phenomena between the grains are observed after the heat-treatment. It thus results in improving the cohesion of grains of the commercial LiMn2O4 and hence the structure is stable even at high charging rate. When the cobalt compound modified LiMn2O4 powder is heat-treated at 500oC, a crystal-like LiCoxMn2-xO4 solid solution is formed. However, when the heat-treatment temperature is raised to 800oC, the cohesion between grains is improved and a film-like LiCoxMn2-xO4 solid solution is formed. DSC experiments are performed on the bare as well as 6 mol% Co coated commercial LiMn2O4 powder heat-treated at 500oC in air. The results show that the bare powder undergoes Jahn-Teller distortion. Hence, the thermal stability of the coated powder is better than the bare powder. Cyclic voltammetric experiments are carried out for the samples of commercial powder and coated LiMn2O4 powder sintered at 500℃ and 800℃ in air atmosphere. The results show that the redox peaks are symmetric and well-separated. This means that the reversibility is good for both bare and coated LiMn2O4 powder. During cycle life test, the capacity fading of the bare LiMn2O4 powder is decreased after heat-treatment. The battery performance of the crystal-like LiCoxMn2-xO4 solid solution, formed after heat-treatment at 500oC in air, is increased due to the prevention of manganese dissolution in to the electrolyte. A film-like LiCoxMn2-xO4 solid solution is formed when the cobalt compound coated LiMn2O4 is heat-treated at 800oC. Due to deep diffusion of cobalt into the LiMn2O4 particles at 800℃, the capacity of this film-like solid solution decreases significantly. To understand the structural changes after cycle life test, some XRD measurements have been carried out. If the capacity fading is serious, some changes in the relative intensities of the (400) and (311) peaks can be observed. If there is disordering in the grains due to exchange of anions, the relative peak intensity of the (400) peak would be higher than the (311) peak. However, in 6 mole% cobalt compound coated LiMn2O4 material, heat-treated at 500oC in air, these peak intensity changes are not observed significantly. This means that the coated LiMn2O4 material is more stable than that of bare material during cycling. The thermal stability of the coated material at elevated temperature is also better than the bare material.
29
Liu, Yu-Tsung, and 劉于琮. "Ethylene Carbonate Adsorption and Decomposition on LiMn2O4 (100) Surface: A DFT Study." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/82269539426417885374.
Анотація:
碩士國立臺灣科技大學
化學工程系
102
A need for improved and efficient energy storage technology is pragmatic for the sustainable development of our society. With this respect, the development of electrochemical energy storage technologies, such as lithium ion batteries, will play a grand role in the advancement of alternative renewable energy sources. Such battery technologies employ redox reactions with intercalation reactions in crystalline metal oxides, where lithium ions act as charge carriers to produce efficient and high power energy storage options. Therefore, a comprehensive understanding of the important processes occurring in lithium ion battery by using either computational or experimental approach will help to develop batteries with better performance. The adsorption and decomposition mechanism of electrolyte on the cathode surface is one of the governing factors which control the stability, capacity and cyclic life. In this thesis, first principles calculations are used to study the adsorption and surface catalyzed decomposition mechanisms of ethylene carbonate on the (100) surface of fully discharged LiMn2O4. Six different adsorption configuration of EC on LiMn2O4 (100) surface was found by using GGA+U approximation. The adsorption strength and electronic properties of each site was then discussed by using density of states (DOS), projected density of states (PDOS) and electron density difference (EDD). Moreover, the initial decomposition mechanisms of EC on LiMn2O4 (100) surface is investigated by examining the minimum energy path between these two minima using the climbing image nudged elastic band reaction-pathway sampling scheme. In all sites, an electron transfer from the surface to the adsorbate was observed resulting in weakening and subsequent breaking of C-O bond and formation of open chain radical. Even though adsorption and decomposition reaction can occur on the (100) surface of LiMn2O4, for all configurations studied, the results show that the generation of gas is highly unlikely to occur at normal condition. In order to investigate the catalytic effect of the surface on the EC decomposition reaction, DFT calculations for the gas phase molecular decomposition of EC are performed and discussed in detail. In general, this work aims to give an insight about the initial stages in surface catalyzed electrolyte decomposition reactions on spinel cathode structure.
30
Yen, Chih-jung, and 顏志榮. "Studies on the SEI Formed between Spinel LiMn2O4 and EC/DEC Electrolyte." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/91697974183604215061.
Анотація:
碩士大同大學
材料工程學系(所)
94
Spinel LiMn2O4 was prepared via electrostatic spray deposition (ESD) method and followed by heat-treatment at various temperatures for various durations. The compositions, crystalline and morphology of the electrodes were investigated with ICP, XRD and SEM. The electrochemical properties of thus prepared electrodes were studied by capacity retention studies. These kind of electrode do not contain any binder or conductive. They are good for solid-electrolyte interface (SEI) studies. In this study, FTIR was used to investigate the SEI formed. It is found that Li2CO3 forms on the spinel electrode before cycling. However, no significant change on the electrode film was found by the image obtained by hard X-ray. The Li2CO3 disappeared as the coin cell was charged to 4.1 V. Compounds containing Li2CO3 and (－(CO)OO(CO)－) functional group appeared as the coin cell was discharged to 3.7 V. After that, Compounds containing Li2CO3 and (－(CO)OO(CO)－) functional group appeared/disappeared periodically as the cells discharged/charged to 3.7 V and 4.1 V, respectively.
31
吳孟哲. "Optical studies of LiFePO4 and LiMnPO4 nanoparticles." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/36081074697155188208.
Анотація:
碩士國立臺灣師範大學
物理學系
102
We present x-ray powder diffraction, Raman-scattering, and spectroscopic ellipsometry measurements of LiMPO4 (M = Fe, Mn) nanoparticles. Our goal is to explore the influence of finite-size effects on the lattice dynamics and electronic structures in these materials by optical spectroscopy. At room temperature, x-ray powder diffraction data show that the lattice constants of nanoparticles are slightly larger than those of bulk samples. Raman-scattering spectra of LiFePO4 and LiMnPO4 nanoparticles show eleven and seven phonon modes. The phonon modes are observed at about 145 cm-1, 158 cm-1, 197 cm-1, 444 cm-1, 584 cm-1, 630 cm-1, 658 cm-1, 950 cm-1, 996 cm-1, 1068 cm-1, and 1140 cm-1 for LiFePO4 nanoparticles. Similarly, the phonon modes appear at about 93 cm-1, 142 cm-1, 437 cm-1, 585 cm-1, 948 cm-1, 1005 cm-1, and 1066 cm-1 for LiMnPO4 nanoparticles. They are red shifted in frequency by 1 ~ 2 cm-1 compared with that of bulk counterpart. This slight redshift observed in the Raman phonon modes of nanoparticles can be attributed to the combination effect of strain induced by amorphous layer and v phonon confinement. Furthermore, with decreasing temperature, no anomaly of phonon parameters was observed near the antiferromagnetic ordering temperature in both LiFePO4 single crystal and nanoparticles. Additionally, the frequencies of Raman phonon modes in Li0.5FePO4 and LiFePO4 nanoparticles are close, however, their intensities differ. The absorption spectra determined from spectroscopic ellipsometry analysis of LiFePO4 and LiMnPO4 show several absorption bands in the spectral range from 3.8 to 6.4 eV. Their assignments are based on the predictions of first-principles calculations. Finally, the values of direct band gap of LiFePO4 single crystal and nanoparticles are estimated to be about 3.80 ± 0.1 eV and 3.45 ± 0.1 eV. The 3.75 ± 0.1 eV and 4.80 ± 0.1 eV band gap are obtained for LiMnPO4 bulk and nanoparticles.
32
Ou-yang, En-shih, and 歐陽恩仕. "Electronic Conduction and Electrochemistry of Ti4+ doped LiMn2O4 with or without Ball Milling." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/87959710690485205848.
Анотація:
碩士國立成功大學
資源工程學系碩博士班
95
This syudy disscused conductivity and electochemical properties of LiMn2O4. According to the reference, the resistivity of material has a suddenly arise about 280K in the cooling temperature process. However, this phenomenon will disappear with the increacing of Ti4+ substitution and the trend of resistivity will increase after reducing Analysed the the charge transfer resistance and diffusion coefficient of LiMn2O4 which after annealing and deal with ball milling by EIS. And we can observe there is quite different between each other. As the increacing of Ti4+ substitution, the study shows that charge transfer resistance didn’t have an obvious change. However, the trend of the diffusion coefficient of lithium ion is opposite to the room temperature resistivity.
33
Guo, Ren-Zheng, and 郭仁政. "Performance studies of LiMn2O4 spinel and LiFePO4 cathode materials for Lithium-ion Batteries." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/09838873956572490215.
Анотація:
碩士義守大學
生物技術與化學工程研究所
92
There are two parts in this research. The first part is to study the cycle performance of LiMn2O4 spinel cathode material in different electrolytes by the pouch cells. To study capacity fade of LiMn2O4 spinel cathode material in different electrolytes by Cyclic Voltammetry (CV) scan experiments. To study Mn+2 dissolution in different electrolytes from LiMn2O4 spinel cathode material by Rotating Ring-Disk Electrode (RRDE) collection experiments. LiMn2O4 spinel cathode material in 1M LiPF6 + EC/DMC (1:1) electrolyte exhibited good cycle performance in pouch cells and good overcharge /overdischarge cycle performance in RRDE The second part is to prepare LiFePO4 cathode material by sol-gel synthesis and precipitation synthesis. To analyze LiFePO4 cathode material by XRD、SEM、TG. LiFePO4 cathode material coated with about 10wt.％ white sugar and analyze electrochemical properties by CV. Finally, the conductivity of LiFePO4 increased with 10wt.％ white sugar.
34
Hon, Yi-Ming, та 洪逸明. "Synthesis and Electrochemical Properties of LiMn2O4±δ Cathodic Materials for Lithium-Ion Battery". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/01149587427501355253.
Анотація:
博士國立成功大學
材料科學及工程學系
89
The spinel LiMn2O4±δ is a very promising cathodic material with economical and environmental advantages as compared with layered compounds such as LiCoO2 and LiNiO2. From the point of view of starting materials, price and toxicity, the LiMn2O4±δspinel has a considerable advantage. In this study, the LiMn2O4±δpowders with single-phase, stoichiometry, nano-particle and high specific surface area was synthesized by tartaric acid and citric acid gel process. The structures of lithium manganese tartrate and lithium manganese citrate precursors were investigated by FT-IR and NMR. The synthesis mechanism of LiMn2O4±δ was studied by TG/DSC and XRD. The poor bonding between lithium and manganese ions with tartaric acid was shown by the FT-IR analysis when lithium nitrate and/or manganese nitrate were used as sources. Since, Li2MnO3 and Mn2O3 impurity compounds were formed in addition to lithium manganese oxides when nitrate salts were used as the sources. When acetate salts were used as sources for the lithium and manganese ions, single-phase LiMn2O4±δwas obtained. The results of FT-IR, 7Li and 13C-NMR measurements revealed that lithium ion bonds with carboxylic acid ligand and the O-H stretching modes of tartaric acid but manganese ion only bonds with carboxylic acid. Lithium and manganese ions were trapped homogeneously in atomic scale throughout the precursor. Such a structure eliminated the need for long-range diffusion during the formation of lithium manganese oxides. Polycrystalline nano-LiMn2O4±δ spinel powder was synthesized by tartaric acid gel process and developed without any detectable minor phase at 300℃. The MAS 7Li-NMR spectra for LiMn2O4±δ calcined from 300 to 800℃ are considered as two spinning side bands. The Knight shifts of LiMn2O4±δ are situated around ~520, 560 ppm, respectively. In our MAS 7Li-NMR spectra, the chemical shift at ~520 ppm is conformed to the lithium ion occupation at 8a position. The chemical shift at ~560 ppm indicates the lithium ion still occupying at 8a position in LiMn2O4±δ but having different distances to neighboring manganese and oxide ions. The Mn3+ is more stable than Mn4+ at high temperature, since the average valence of manganese decreased with increasing synthesis temperature and resulted in an increase of the lattice parameter with calcination temperatures increase. The samples calcined at 300℃ having higher average valence of manganese of 3.63 exhibit low initial capacity. During charge process, the Mn3+ must release one electron and be oxidized to Mn4+. Lithium manganese oxide with Mn valence greater than 3.5 will have less Mn3+ ions for discharge reaction. On the other hand, sample calcined at 500℃ shows an initial capacity of 117 mAh/g due to manganese valence close to 3.5. For the sample calcined at 800℃, it shows low average valence of manganese and low initial capacity because the average valence of manganese is far below 3.5 under this circumstance. LiMn2O4±δ tends to transforms from cubic to tetragonal structure due to the well-known Jahn-Teller distortion. In lithium manganese citrate precursor, the lithium and manganese ions only bonded with carboxylic acid ligand, not bonded with O-H stretching modes of citric acid. A small amount of γ-Mn3O4 was formed at low temperature, but it disappeared as calcinations time increased. The lattice parameter of single-phase LiMn2O4±δ increased with calcinations temperature increasing, however, the average valence of manganese decreased. The LiMn2O4±δ calcined at 300℃ with average valence of 3.69 exhibited excellent cycle life. The one calcined at 800℃ had the maximum capacity of 105 mAh/g with average manganese valence of 3.52.
35
Ramogayana, Brian. "Lithium manganese oxide (LiMn2O4) spinel surfaces and their interaction with the electrolyte content." Thesis, 2020. http://hdl.handle.net/10386/3415.
Анотація:
Thesis (M.Sc. (Physics)) -- University of Limpopo, 2020.This dissertation presents the results of the ab-initio based computational studies of spinel lithium manganese oxide (LiMn2O4) bulk, surfaces, and the adsorption of an organic electrolyte, ethylene carbonate. The spinel LiMn2O4 is one of the most promising cathode materials for Lithium-ion batteries because of its affordability, nontoxicity, and improved safety compared to commercially used LiCoO2. However, it also suffers from the irreversible capacity due to the electrolyte-cathode interactions which lead to manganese (Mn) dissolution. Using the spin-polarized density functional theory calculations with on site Coulomb interactions and long-range dispersion corrections [DFT+U−D3−(BJ)], we investigated the bulk properties, surface stability and surface reactivity towards the ethylene carbonate (EC) during charge/discharge processes. Firstly, we explored the structural, electronic, and vibrational bulk properties of the spinel LiMn2O4. It was found that the bulk structure is a stable face-centred cubic structure with a bandgap of 0.041 eV and pseudo-gap at the Fermi level indicating electronic stability. Calculated elastic constants show that the structure is mechanically stable since they obey the mechanical stability criteria. The plotted phonon curves show no imaginary vibrations, indicating vibrational stability. To study the charge/discharge surfaces, we modelled the fully lithiated and the partially delithiated slabs and studied their stability. For the fully lithiated slabs, Li-terminated (001) surface was found to be the most stable facet, which agrees with the reported experimental and theoretical data. However, upon surface delithiation, the surface energies increase, and eventually (111) surface becomes the most stable slab as shown by the reduction of the plane in the particle morphologies. Finally, we explored the surface reactivity towards the ethylene carbonate during charge/discharge processes. The ethylene carbonate adsorption on the fully lithiated and partly delithiated facets turn to enhance the stability of (111) surface. Besides the strong interaction with the (111) surfaces, a negligible charge transfer was calculated, and it was attributed by a large charge rearrangement that takes place within the surfactant upon adsorption. The wavenumbers of the C=O stretching showed a red shifting concerning the isolated EC molecule
36
Lin, Yong-Mao. "Preparation and Analysis of ZrO2-coated LiMn2O4 as Cathode for Li-ion Secondary Batteries." 2004. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2906200413381600.
37
LIN, BO-CHUN, and 林博淳. "The Comparative Analysis for Physical and Electrochemical Properties of LiMn2O4 and LiAl0.1Mn1.9O4 Thin Films." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/jqdntk.
38
Lin, Yong-Mao, and 林永茂. "Preparation and Analysis of ZrO2-coated LiMn2O4 as Cathode for Li-ion Secondary Batteries." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/70953299853986382690.
Анотація:
碩士國立臺灣大學
化學工程學研究所
92
Two synthetic routes including sol-gel process and fluidized-bed chemical vapor deposition (FBCVD) process were introduced to the preparation of ZrO2-coated LiMn2O4 as cathode materials for lithium ion secondary batteries. X-ray diffraction (XRD) spectra from the ZrO2-coated LiMn2O4 indicated that ZrO2 exist as amorphous phase. The morphology of ZrO2-coated samples were observed by scanning electron microscope (SEM) and transmission electron microscope (TEM), which revealed that the zirconium oxide attached smoothly onto the surface of LiMn2O4. The surface-modified LiMn2O4 samples showed much better capacity retention than the unmodified LiMn2O4 cathode at both room temperature and 55℃. The improved cycle life performance could be due to a suppression of the Jahn-Teller distortion which took place at low voltage during cycling.
39
Wang, Chih-Shian, and 王智憲. "Effect of Post-treatment on Charge-discharge Capacity of Spray-drying LiMn2O4 Electrode Material." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/48739571461090113868.
Анотація:
碩士國立成功大學
材料科學及工程學系碩博士班
92
A spray-drying method has been developed to synthesize ultrafine LiMn2O4 powders. For the purpose to acquire completely spinel LiMn2O4 powders, a post heat treatment, calcination, should be performed. In this study, parameters of heat treatment including atmospheres, holding temperature and time were controlled to obtain the powders with superior discharge capacity. The cyclic discharge tests were performed at a 0.3C rate between 3.0V and 4.3V. Through analyzing by XRD and BET, it could be found that the lattice constant was enlarged and the surface area was reduced with increasing holding temperature and holding time. The effect of holding time was tremendous. The recommended optimal parameters are calcining at 700℃ for 5h. The samples thus produced exhibit an initial discharge capacity of 125mAh/g and the capacity retention of 95% after 15 cycles. To reduce oxygen deficiency while calcination at high temperatures, parts of the powders were calcined under flowing oxygen circumstance at 900℃. It can be found that calcinations with oxygen can raise the initial discharge capacity, however, capacity fading after cyclic discharge can not be improved.
40
Su, Hsiang-Ju, and 蘇湘茹. "Effect of surfactant on the electrochemical properties of LiMn2O4 cathode material for Lithium-ion battery." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/7y5dcm.
Анотація:
碩士國立臺北科技大學
材料及資源工程系研究所
100
The purpose of this reserch will try to fabricate the LiMn2O4 with ordered spinel structure. The three block copolymer surfactant(P123)was employ as the structure agents for synthesizing the high specific surface area in LiMn2O4 through the solid state reaction method. The LiCH3COO‧2H2O and Mn(CH3COO)2‧4H2O are as the precursors for the inorganic part of cathode (LiMn2O4). Discuss the different content of surfactant with the structure of the powder particle size, specific surface area, while the material specific surface area will affect the moist results of the electrolyte and cathode material, so affecting the actual reaction area and discharging efficiency. That investigating the affection between specific surface area and electrical attributes. According to XRD patterns, the solid state reaction method synthesis of LiMn2O4 is a single spinel phase. By BET analysis results indicated that adding a surfactant doesn’t affect the original spinel structure. In the SEM observations, after different surfactants are added in LiMn2O4, that become various formation of micelles and micelles contribute to the increase of specific capacity. By this reserch, specific surface area in 0.4 ~ 1.2 m2/g compared with the capacitance can effectively enhance the efficiency and high current efficiency of discharge is closer to the lower current discharge. And the specific capacity can up to 84.6 mAh/g, in accordance with different concentrations of P123 surfactant 1.42M that the Li+ ion diffusion coefficient is 6.23x10-12 cm2 s-1, and specific surface area of 1.18 m2/g. Under the different rates of charging and discharging, the higher will close to lower. However compared with different concentrations of F127 surfactant 3.43M of the Li+ ion diffusion coefficient of 1.37x10-11 cm2s-1 is the best, the specific surface area of 0.70 m2/g. Although the maximum specific capacity, but higher than in the high-current discharge easy recession. The experimental results show that the better to add P123 surfactant 1.42M because the high current efficiency of discharge is closer to the lower current discharge.
41
Chung, Han-Yang, and 鍾瀚揚. "Conduction and Electrochemistry Mechanism of Al3+ and Ni2+ doped LiMn2O4 with or without Ball Milling." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/10651976423228485918.
Анотація:
碩士國立成功大學
材料科學及工程學系碩博士班
93
Decreasing of the temperature causes the phenomenon which the resisitity arise suddenly near temperature 280K. That is the manganese spinel undergoes a phase transition between high -temperature cubic and low temperature orthorhombic phase. Substitution of manganese cause disappearance of the phase transition characteristic of a stoichiometric spinel and affects the conduction mechanism of the material. The powder with ball milling has different electrochemical properties from it with annealing. The material LiMn2O4 doped with Ni2+ or Al3+ ion also shows the different electrochemical properties.
42
Chen, Chen-Chung, and 陳振崇. "Modification and Characterization of LiMn2O4 Cathode Thin Films and Powders for Lithium Ion Secondary Batteries." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/71533111264889809064.
Анотація:
博士逢甲大學
材料科學所
98
Among all cathode materials, LiMn2O4 exhibits high energy density, lower cost, acceptable environmental characteristics and better safety property than the others. The researches on spinel LiMn2O4 often focused on the prevention of the capacity fading and enhancement of the electrochemical performance, particularly under deep discharge (below 3 V) and elevated temperature operation (>55 oC). In this study, a novel plasma treatment technique has been developed and applied on LiMn2O4 cathode materials. The microstructure and electrochemical performances of the plasma treated LiMn2O4 cathode materials were analyzed and compared. Firstly, the plasma treatment was used to treat high temperature annealed (600 oC) LiMn2O4 thin films. LiMn2O4 thin films were studied because they are free of conducting additions and binders. They are therefore good platforms for scientific studied. They are also useful for thin film batteries or microbatteries. Under optimal plasma conditions, it was observed that a dense, smooth and nanocrystalline sub-surface microstructure was formed on the original LiMn2O4 thin film. The plasma treated LiMn2O4 thin films exhibited enhanced electrochemical performances even under harsh conditions, such as over-discharge and elevated temperature (60 oC) cycles. It makes these plasma-treated LiMn2O4 thin film cathodes potential candidates for high-temperature (>60 oC) secondary batteries. In addition, most of the crystalline cathode materials can only be obtained by high temperature annealing (600~750 oC). The requirement of high annealing temperature limits the choice of substrates and the compatibility with other devices especially when the cathodes are used for micro batteries or thin film batteries. Therefore, the goal in second part of the thesis is to study the effects of plasma treatments on lower temperature annealed (400 oC) LiMn2O4 thin films. The results showed that a slight disordered lattice structure was formed at the sub-surface of the lower temperature annealed LiMn2O4 thin films, as indicated by the Raman spectra. With suitable plasma parameters, the 3.0-4.5 V capacity was ~ 110 mAh/g, which was comparable with the high temperature annealed films. For films cycled under over-discharge voltage range (4.5 – 2.0 V), the electrochemical stability can be maintained. It has been demonstrated that the plasma treatment can improve the electrochemical performance of the lower temperature annealed LiMn2O4 thin films. From first and second parts of this thesis, it has been indicated that the sub-surface (10 - 100 nm) microstructures may also play a certain role, though they have yet to be characterized. Thus, in order to resolve the microstructures at the sub-surface, the specimens were prepared by focused ion beam (FIB), and the sub-surface microstructures have been successfully analyzed on a transmission electron microscope (HRTEM) in third part of this thesis. The variation of the sub-surface microstructure was identified and correlated to the electrochemical performances of the LiMn2O4 thin films. The materials and electrochemical results revealed that the improved performances can be attributed to the dense structures and fine grains in the sub-surface, induced by the plasma treatments. In the fourth part, the study is to clarify the relationship between thin film annealing temperatures and plasma parameters. The microstructural evolution of the low and high temperature annealed films under plasma treatments can be interpreted by the atomic relation model and re-sputtering model. With the optimal parameters of plasma treatment and thermal annealing, a dense sub-surface microstructure with nanocrystalline (~10 nm) features can be obtained without changing their overall crystal structures. The films with such sub-surface microstructure show much lower capacity fading in over-discharge (below 3 V) and elevated temperature cycles (60 oC) than the untreated films. The results can be obtained for both the 400 oC and 600 oC annealed films. Finally, the plasma treatments tested on pure LiMn2O4 thin films were applied on conventional power electrodes. Since the amounts of active materials in conventional power electrodes are much greater, the higher energy dc pulsed plasma was used. The powder electrodes studied were composed of LiMn2O4 powders, conducting carbon, and PVDF binders. The results showed that though the samples were treated with higher energy plasma source, the temperature is lower than 140 oC. The plasma treatment remained a low temperature modification process. Because of the lower melting temperature of the PVDF binders, it was observed that a F-contented layer covered the surface of the plasma treated LiMn2O4 powder electrode, due to the reflow of PVDF and re-sputtering of LiMn2O4 and carbon black. The resulted morphology was cross-necked and smooth. In the electrochemical tests, the samples with proper plasma treating time exhibited better electrochemical performances, and the discharge capacity with a discharge current of 2 C was ~ 128 mAh/g. Furthermore, the treatment can improve the cycling stability of these samples in the previously mentioned harsh conditions. The results showed that the plasma treatment works on the powder-type LiMn2O4 cathodes as well as the thin film ones.
43
Chen, Chen-Chung, and 陳振崇. "The study of the surface modified LiMn2O4 cathode material prepared by ultra fast sol-gel method." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/51386827028101626644.
Анотація:
碩士逢甲大學
材料科學所
93
The enormous growth in portable electronic devices such as cellular phones and notebook computer has led to increasing demand for compact lightweight micro-batteries with high energy density and long cyclic life. Lithium secondary batteries have satisfied this demand to a greater degree than other rechargeable battery systems. This research uses LixMn2-yO4 as cathode materials prepared by sol-gel method. Through cathode materials annealed at different parameter of procedure in air, then it can improve the disadvantage of the cathode materials, LixMn2-yO4. Moreover, it also uses air annealing heat treatment to develop high capacity high operating discharge voltage cathode materials, and increases electric conductivity of thin film effectively. The results show that LixMn2-yO4 thin films at 600℃-10 min annealing in air could have spinel structure, two high stable plateau of discharge voltage（3.9 and 4.1V）. And the final total discharge capacity of the films at 600℃-10min could reach 110mA/g, higher than at another annealing temperature. Furthermore, surface modified layer could effectively protect LixMn2-yO4 thin films to the dissolution of manganese during the charge-discharge period. Then, they promoted the electrochemical properties of the films.
44
Huang, Ming-Ren, and 黃明仁. "Structural Modifications and Capacity Fading of LiMn2O4 Cathode during Charge-Discharge of Secondary Lithium Ion Batteries." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/11347201698228305320.
Анотація:
博士國立中山大學
材料科學研究所
92
Abstract A vast majority of the studies devoted to Lithium manganese oxide deals with their electrochemical characteristics in lithium batteries. The main project of this study is to realize the structure evolution upon electrochemical cycling. The phase transformations under the charge and discharge testing are an interesting project. Nitrate or oxide precursor calcined at 800°C can produce single phase stoichiometric LiMn2O4. The hypo-stoichiometric compositions (xLi2O×4MnO, x < 1) synthesized by Li-poor situation contain LiMn2O4 and Mn2O3. The hyper- stoichiometric compositions (xLi2O×4MnO, x > 1) synthesized by Li-rich situation contain non-stoichiometric spinel LixMn2O4 (such as Li4Mn5O12 or Li2Mn4O9) and Li2MnO3. The lattice parameter of LiMn2O4 increases slightly with increase of the lithium content at x < 1 (0.823 ~ 0.824 nm), but decreases sharply for x = 1.0 ~ 1.8 (0.824 to 0.817 nm). Differential thermal analysis showed at temperature higher than 935ºC, rocksalt phase (with tetragonal symmetry), Mn3O4 will be produced. Above 1045ºC, the crystallite phases contain cubic LiMn2O3 spinel, tetragonal Mn3O4 and orthorhombic symmetry LiMnO2. After high temperature annealing (> 935ºC), the residual phase is lithium-deficient structure, Mn3O4. Apparent facets with {111}, {011}, and {001} (and {113}) planes are usually observed. The LiMn2O4 crystallite appears to be a truncated cubo-octahedron. The lowest surface energy gsv for LiMn2O4 spinel is located at the {111} planes. Lamellae domain and twinned structure are usually observed in LiMn2O4 particles. The occurrence of domain boundary and twin plane are {111} mostly. Forbidden reflections {200}, {420} in the initial powder and 1/2{311} and 1/3{422} superlattice reflections occurred after charging and discharging test reveal LiMn2O4 structure is a violation of space group. [311]/[111] peak ratio in the XRD traces is increase after electrochemical cycling. Fraction of inverse phase increased upon electrochemical cycling. The results for structure evolution under charging and discharging test can be divided into two parts for reversible and irreversible. First, unit cell of cubic spinel contracted upon charging and returned to original after discharging. The lattice constant varies back and forth between 0.824 nm to 0.814 nm for cycle between 3.3 and 4.3 V. LiMn2O4 transits to Li4Mn5O12 and l-MnO2 after fully charging to 4.3 V, which then recovers to cubic spinel LixMnyO4 after discharging to 3.3 V. The structure variations in the cycle of changing and discharging are LiMn2O4 – (Li4Mn5O12 + l-MnO2) – LixMnyO4. And metastable circular or rectangle LiMn2O4 particles observed in the surface can be extracted and inserted Li+ ion upon charging and discharging test. This process is reversible. Second, (1) tetragonal, rhombohedral and triclinic distorted within cubic spinel particles; (2) nanoscale regions of highly disordered lattices observed; (3) amorphous film observed in the powder particle surface; (4) crystalline phase Mn2O3 increased; (5) structure collapse inside the particle and the domain boundary; (6) inverse spinel structure. The structure of LixMn2O4 had distorted upon electrochemical cycling. These results are irreversible.
45
Lin, Chih-Hao, and 林志豪. "Effect on conductivity and electrochemistry of the addition of Al(III) and Ni(II) ion to LiMn2O4." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/06679447527401998295.
Анотація:
碩士國立成功大學
材料科學及工程學系碩博士班
91
The addition of Al(III) and Ni(II) ions and ball mill treatment of the cathode materials- LiMn2O4 powder show crucial effects on conductivity(charge transfer resistance, in contrary.), cycle test and related electrochemical properties of lithium-ion batteries application. Conductivity shows an increase by adding Al(III) ion to LiMn2O4 powder(without ball mill treatment) while the Ni(II) or both of them(Al(III), Ni(II) at once )make a decrease, respectively. The addition of both Al(III) and Ni(II) ions also show the better performance in cycle test and lower the Jahn-Teller effect which would cause instability in structure of cathode material. Ball mill treatment(24hrs) on LiMn2O4 powder make the particle size from 1~2μm to 40~80nm (obtained by XRD) and improve the conductivity dramatically that have mentioned above. XRD data also show that increase the quantity in both Al(III) and Ni(II) ions in LiMn2O4 powder will accompany with a decrease in lattice constant in LiAlxNiyMn(2-x-y)O4 crystal.
46
Wu, Qi-Hui [Verfasser]. "Photoelectron spectroscopy of intercalation phases : Na and Li in V2O5 thin films and LiMn2O4 / Qi-Hui Wu." 2003. http://d-nb.info/968071562/34.
47
Pai-FenCheng and 鄭百棻. "The Structural Characteristics and the High Current Rate Charge-Discharge Mechanism of Si/Fe-coated LiMn2O4 Powder Systems." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/4xqvvy.
48
"Post-Combustion Electrochemical Capture and Release of CO2 and Deformation and Bulk Stress Evolution in LiMn2O4 Intercalation Compounds." Doctoral diss., 2016. http://hdl.handle.net/2286/R.I.40212.
Анотація:
abstract: This investigation is divided into two portions linked together by the momentous reaches of electrochemistry science, principles influencing everyday phenomena as well as innovative research in the field of energy transformation. The first portion explores the strategies for flue gas carbon dioxide capture and release using electrochemical means. The main focus is in the role thiolates play as reversible strong nucleophiles with the ability to capture CO2 and form thiocarbonates. Carbon dioxide in this form is transported and separated from thiocarbonate through electrochemical oxidation to complete the release portion of this catch-and-release approach. Two testing design systems play a fundamental role in achieving an efficient CO2 catch and release process and were purposely build and adapted for this work. A maximum faradaic efficiency of seventeen percent was attained in the first membrane tests whose analysis is presented in this work. An efficiency close to thirty percent was attained with the membrane cell in recent experiments but have not been included in this manuscript.
The second portion of this manuscript studies bulk stress evolution resulting from insertion/extraction of lithium in/from a lithium manganese oxide spinel cathode structure. A cantilever-based testing system uses a sophisticated, high resolution capacitive technique capable of measuring beam deflections of the cathode in the subnanometer scale. Tensile stresses of up to 1.2 MPa are reported during delithiation along with compressive stresses of 1.0 MPa during lithiation. An analysis of irreversible charge loss is attributed to surface passivation phenomena with its associated stresses of formation following patterns of tensile stress evolution.Dissertation/Thesis
Doctoral Dissertation Materials Science and Engineering 2016
49
Kai-YuanYang and 楊凱元. "The crystallization and the charge-discharge mechanism of high-low temperatures for Al/Ga-coated LiMn2O4 powder systems." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/61394176892442537674.
Анотація:
碩士國立成功大學
材料科學及工程學系碩博士班
101
Li ion secondary battery is a potential battery due to its high working voltage, high energy density, and good cycling life. LiMn2O4 is one of the most promising cathode materials due to its low cost, easy to synthesize, and environmentally friendly comparing with other mainstream cathode materials. The structure and capacity of LiMn2O4 ¬operated in a high-temperature (55oC) deteriorates seriously. In this study, Ga and Al coating LiMn2O4 were synthesized by two-stage process of surface modification. This study furthermore utilizes analysis methods such as the X-Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectrometer (XPS), Transmission Electron Microscope (TEM), and Auger Electron Spectroscopy (AES) to obtain surface crystallization, valence changes of Mn ions, powder morphology, lattice structures and their characteristics. From the results of battery testing and the Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), it was found that the coating modified layer of LiMn2-x-yAlxGayO4 at 55oC enhanced the capacities and cycling stability at various current rate, and effectively inhibit the dissolution of Mn ions. In addition, the Electrochemical Impedance Spectroscopy (EIS), a four-point probe and Conductometer were used to clarify the influences of temperature on the LiMn2O4 electrode. The results were confirmed that the conductivities of the electrode and the electrolyte would affect the capacities. It was found that the conductivity and capacities of electrodes decreased with decreasing the temperature. Notably, compared with the coating modified layer of LiMn2-xAlxO4, the coating modified layer of LiMn2-x-yAlxGayO4 could relax the deterioration of LiMn2O4 at low temperatures. The deintercalation/intercalation of Li ions of Al/Ga-coated surface was easier, that is suitable for application at low-temperature environment.
50
Shih, Fu-Yun, and 石富勻. "Effect of Chitosan Addition on Deposition and Electrochemical Behaviors of Thin-Film LiMn2O4 Cathodes by Sol-Gel Method." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/36908244052470887032.
Анотація:
博士國立成功大學
材料科學及工程學系碩博士班
94
Sol-gel method is one of the methods which were widely employed to fabricate thin films, due to low cost, simple processing and ease of controlling the composition stoichiometry and desired microstructure. However, the quality of the deposited LiMn2O4 films was highly dependent on the nature of the precursor solution. For example, the poor wettability between the precursor solution and substrate resulted in a inhomogenous film. Thus, in this study, a natural biomaterial, chitosan, was used as an additive. It was found that the addition of chiotsan can not only stabilize the lithium/manganese acetates-containing ethanol solution with no formation of precipitates for at least 10 months, but also be beneficial to the formation of a single-phase LiMn2O4 film. This is attributed to the chelating between chitosan and Li+/Mn2+ ions. Moreover, the electrochemical tests also showed that the LiMn2O4 film deposited from the chitosan-added precursor solution exhibits a higher discharge capacity of 134 mAh/g at 1C and a better rate performance (86.4% of the discharge capacity at 1C can be maintained when the discharge rate increases from 1C up to 8C) in comparison with one from the chitosan-free solution. On the other hand, dense LiMn2O4 films deposited on a Pt-coated silicon substrate were obtained by annealing the deposited Li-Mn-O-chitosan films under a two-stage heat-treatment procedure. It was demonstrated that the preheat-treatment at 300℃plays an important role in the densification of LiMn2O4 films. This is due to the inhibition of forming pores and the formation of the nano-sized LiMn2O4 crystallites. And a postheat-treatment at a higher temperature (≧400℃) in the second stage will lead to the crystal growth of LiMn2O4 nanocrystallites and the formation of a dense LiMn2O4 film. Furthermore, the electrochemical performance of the LiMn2O4 films deposited from the chitosan-added precursor solution was dependent on the annealing temperatures. The LiMn2O4 film calcined at 700℃ for 1 h showed the highest Li-ion diffusion coefficient, 1.55×10-12 cm2/s among all calcined films. It is due to the larger interistial space and better crystal perfection of LiMn2O4 film calcined at 700℃. Thus, the 700℃-calcined LiMn2O4 film exhibited the best rate performance in comparison with the ones calcined at other temperatures. The effect of the addition of chitosan or PVP in the precursor solution on the deposition and electrochemical properties of LiMn2O4 films was also studied. Due to the adequate viscosity of the chitosan-added precursor solution, the films deposited from the chitosan-added precursor solution showed a higher deposition rate than ones from the PVP-added solution under the same coating parameters. And the charge-discharge tests indicate that the addition of chitosan or PVP in the precursor solution shows little difference on the electrochemical properties of the resultant LiMn2O4 films. Owing to the low thermal decomposition temperature of both chitosan and PVP (about 300℃), a heat-treatment of 700℃ would result in the complete removal of chitosan or PVP in the prepared films. Thus, these LiMn2O4 films prepared from either the chitosan- or PVP-added precursor solutions exhibit no discernible difference in the electrochemical behaviors.