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Academic literature on the topic 'Anode Li'
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Dissertations / Theses on the topic "Anode Li"
1
Cen, Yinjie. "Si/C Nanocomposites for Li-ion Battery Anode." Digital WPI, 2017. https://digitalcommons.wpi.edu/etd-dissertations/468.
Full textAbstract:
The demand for high performance Lithium-ion batteries (LIBs) is increasing due to widespread use of portable devices and electric vehicles. Silicon (Si) is one of the most attractive candidate anode materials for the next generation LIBs because of its high theoretical capacity (3,578 mAh/g) and low operation potential (~0.4 V vs Li+/Li). However, the high volume change (>300%) during Lithium ion insertion/extraction leads to poor cycle life. The goal of this work is to improve the electrochemical performance of Si/C composite anode in LIBs. Two strategies have been employed: to explore spatial arrangement in micro-sized Si and to use Si/graphene nanocomposites. A unique branched microsized Si with carbon coating was made and demonstrated promising electrochemical performance with a high active material loading ratio of 2 mg/cm2, large initial discharge capacity of 3,153 mAh/g and good capacity retention of 1,133 mAh/g at the 100th cycle at 1/4C current rate. Exploring the spatial structure of microsized Si with its advantages of low cost, easy dispersion, and immediate compatibility with the prevailing electrode manufacturing technology, may indicate a practical approach for high energy density, large-scale Si anode manufacturing. For Si/Graphene nanocomposites, the impact of particle size, surface treatment and graphene quality were investigated. It was found that the electrochemical performance of Si/Graphene anode was improved by surface treatment and use of graphene with large surface area and high defect density. The 100 nm Si/Graphene nanocomposites presented the initial capacity of 2,737 mAh/g and good cycling performance with a capacity of 1,563 mAh/g after 100 cycles at 1/2C current rate. The findings provided helpful insights for design of different types of graphene nanocomposite anodes.
2
Gullbrekken, Øystein. "Thermal characterisation of anode materials for Li-ion batteries." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19224.
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Coin cells with lithium and graphite electrodes were assembled using different combinations of graphite material and electrolyte. Specifically, three commercially available graphite materials and five electrolyte compositions were studied. The cells were discharge-charge cycled with varying parameters in order to determine the performance of the graphite materials and electrolytes. Particularly, a temperature chamber was employed to cycle some cells at temperatures between 0 and 40°C to find the significance of the electrolyte composition and graphite material on the cell performance at these temperatures. The cycled cells were disassembled and samples from the graphite electrode soaked with electrolyte were prepared for thermal analysis, specifically differential scanning calorimetry (DSC). The thermal stability of the graphite electrodes and the influence from the graphite and electrolyte properties and the cycling parameters were analysed. In order to facilitate the interpretation of the results from discharge-charge cycling at different temperatures, DSC analysis from -80 to +50°C was performed on the pure electrolytes.Confirming previous studies, it was found that both the thermal stability and cycling performance were highly influenced by the properties of a solid electrolyte interphase (SEI), situated between the graphite surface and the electrolyte and formed during cycling. The three graphites were good substrates for stable SEI formation, exhibited by high thermal stability after being cycled at room temperature. After cycling with a temperature program, subjecting the cells to temperatures between 0 and 40°C, the thermal stability was generally reduced. This was attributed to increased SEI formation. The properties of both the electrolyte and graphite influenced the SEI and consequent thermal stability, though in different ways.The cell capacity was considerably reduced upon cycling at lower temperatures, such as 10 and 0°C. The results indicate that the electrolyte properties, particularly the viscosity and resulting conductivity, played the most important role in determining the cell performance. Low viscosity electrolyte components should be utilised, maintaining the electrolyte conductivity even at reduced temperatures. The graphite properties did not influence the cell performance at the temperatures studied. Advice is given on which electrolyte components should be avoided to build Li-ion cells performing acceptably at temperatures from 0 to 40°C.
3
FUGATTINI, Silvio. "Binder-free porous germanium anode for Li-ion batteries." Doctoral thesis, Università degli studi di Ferrara, 2019. http://hdl.handle.net/11392/2488081.
Full textAbstract:
To develop high energy density lithium ion batteries, the use of new electrode
materials is required. Germanium is among the possible alternatives to the most
commonly used anode, graphite (372 mAh/g), thanks to its four-times higher
theoretical gravimetric capacity (1600 mAh/g).
Here is presented a two-step method to produce a binder-free porous germanium
anode, depositing the semiconductor on metallic substrates by means of Plasma
Enhanced Chemical Vapour Deposition (PECVD) and subsequently performing
an electrochemical etching with hydrofluoric acid to create a porous structure.
The Ge-based electrode attained a capacity of 1250 mAh/g at a current rate of
1C (1C=1600 mA/g) and retained a stable capacity above 1100 mAh/g for more
than 1000 cycles tested at different C-rates up to 5C.
Both deposition and etching techniques are scalable for industrial production,
whose fields of application could be aerospace or medical applications, due to the
high cost of germanium as a raw material.<br>Per sviluppare batterie agli ioni di litio ad alta densità energetica, è necessario
l’utilizzo di nuovi materiali elettrodici. Il germanio è una delle possibili alternative
all’anodo più comunemente impiegato, la grafite (372 mAh/g), grazie alla sua
capacità gravimetrica teorica quattro volte maggiore (1600 mAh/g).
In questo lavoro viene presentato un processo in due fasi per realizzare un anodo
in germanio poroso privo di legante (binder), realizzando film di semiconduttore
su substrati metallici mediante deposizione chimica da fase vapore assisitita da
plasma (PECVD) ed effettuando successivamente un attacco elettrochimico con
acido fluoridrico per creare una struttura porosa.
L’elettrodo in germanio poroso ha raggiunto una capacità di 1250 mAh/g ad
una velocità di carica/scarica pari ad 1C (1C = 1600 mA/g) mantenendo, inoltre,
una capacità stabilmente superiore a 1100 mAh/g per più di 1000 cicli a diversi
C-rate fino a 5C.
Sia la tecnica di deposizione che quella di attacco chimico sono scalabili per
la produzione industriale, i cui possibili campi di applicazione sono il settore
aerospaziale o medico, a causa dell’elevato costo del germanio come materia prima.
4
Janíček, Zdeněk. "Stabilita katodového materiálu pro LI-ion akumulátory." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-220974.
Full textAbstract:
This diploma thesis focuses on study of positive electrode materials for Li-Ion batteries. Our aim are intercalation materials whose are really perspective materials whose are widely used in this case. The theoretical part of my thesis focus on basic study of Li-ion batteries and their parameters. We studied charging and discharging processes. AFM and SEM were used as additional techniques for study LiCoO2 a Li0,975K0,025CoO2. We tested lifetime and stability of electrode as a perspective material for electrode for Li-ion batteries.
5
Buiel, Edward. "Lithium insertion in hard carbon anode materials for Li-ion batteries." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0013/NQ36573.pdf.
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6
Mayo, Martin. "Ab initio anode materials discovery for Li- and Na-ion batteries." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/270545.
Full textAbstract:
This thesis uses first principles techniques, mainly the ab initio random structure searching method (AIRSS), to study anode materials for lithium- and sodium- ion batteries (LIBs and NIBs, respectively). Initial work relates to a theoretical structure prediction study of the lithium and sodium phosphide systems in the context of phosphorus anodes as candidates for LIBs and NIBs. The work reveals new Li-P and Na-P phases, some of which can be used to better interpret previous experimental results. By combining AIRSS searches with a high-throughput screening search from structures in the Inorganic Crystal Structure Database (ICSD), regions in the phase diagram are correlated to different ionic motifs and NMR chemical shielding is predicted from first principles. An electronic structure analysis of the Li-P and Na-P compounds is performed and its implication on the anode performance is discussed. The study is concluded by exploring the addition of aluminium dopants to the Li-P compounds to improve the electronic conductivity of the system. The following work deals with a study of tin anodes for NIBs. The structure prediction study yields a variety of new phases; of particular interest is a new NaSn$_2$ phase predicted by AIRSS. This phase plays a crucial role in understanding the alloying mechanism of high-capacity tin anodes, work which was done in collaboration with experimental colleagues. Our predicted theoretical voltages give excellent agreement with the experimental electrochemical cycling curve. First principles molecular dynamics is used to propose an amorphous Na$_1$Sn$_1$ model which, in addition to the newly derived NaSn$_2$ phase, provides help in revealing the electrochemical processes. In the subsequent work, we study Li-Sn and Li-Sb intermetallics in the context of alloy anodes for LIBs. A rich phase diagram of Li-Sn is present, exhibiting a variety of new phases. The calculated voltages show excellent agreement with previously reported cycling measurements and a consistent structural evolution of Li-Sn phases as Li concentration increases is revealed. The study concluded by calculating NMR parameters on the hexagonal- and cubic-Li$_3$Sb phases which shed light on the interpretation of reported experimental data. We conclude with a structure prediction study of the pseudobinary Li-FeS$_2$ system, where FeS$_2$ is considered as a potential high-capacity electrochemical energy storage system. Our first principles calculations of intermediate structures help to elucidate the mechanism of charge storage observed by our experimental collaborators via $\textit{in operando}$ studies.
7
Hapuarachchi, Sashini Neushika Sue. "Fabrication and characterization of silicon based electrodes for Li-ion batteries." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/207430/1/Sashini_Hapuarachchi_Thesis.pdf.
Full textAbstract:
This thesis presents the synthesis and characterization of silicon electrodes to address critical challenges in development of high capacity Li-ion batteries. Failure mechanisms of silicon electrodes are investigated at different material length scales and effective strategies are proposed to overcome them, which will benefit in developing high performance next-generation rechargeable Li-ion batteries.
8
Vallachira, Warriam Sasikumar Pradeep. "Study of Silicon Oxycarbide(SiOC) as Anode Materials for Li-ion Batteries." Doctoral thesis, Università degli studi di Trento, 2013. https://hdl.handle.net/11572/368129.
Full textAbstract:
The principal object of this thesis is the investigation of silicon oxycarbide (SiOC) ceramics as anode material for Li-ion batteries. The investigated materials are prepared by cross linking commercial polymer siloxanes via hydrosylilation reactions or hybrid alkoxide precursors via sol-gel. The cross linked polymer networks are then converted in to ceramic materials by a pyrolysis process in controlled argon atmosphere at 800-1300 °C.
In details the influence of carbon content on lithium storage properties is addressed for SiOC with the same O/Si atomic ratio of about 1. Detailed structural characterization studies are performed using complementary techniques which aim correlating the electrochemical behavior with the microstructure of the SiOC anodes. Results suggest that SiOC anodes behave as a composite material consisting of a disordered silicon oxycarbide phase having a very high first insertion capacity of ca 1300 mAh g-1 and a free C phase. However, the charge irreversibly trapped into the amorphous silicon oxycarbide network is also high. In consequence the maximum reversible lithium storage capacity of 650 mAh g-1 is measured on high-C content SiOCs with the ratio between amorphous silicon oxycarbide and the free C phase of ï ¾ 1:1. The high carbon content SiOC shows also an excellent cycling stability and performance at high charging/discharging rate with the stable capacity at 2C rate being around 200 mAh g-1.
Increasing the pyrolysis temperature has an opposite effect on the low-C and high-C materials: for the latter one the reversible capacity decreases following a known trend while the former shows an increase of
xi
the reversible capacity which has never been observed before for similar materials.
The influence of pyrolysis atmosphere on lithium storage capacity is investigated as well. It is found that pyrolysis in Ar/H2 mixtures, compared to the treatment under pure Ar, results into a decrease of the concentration of C dangling bonds as revealed by electron spin resonance (ESR) measurements. The sample prepared under Ar/H2 mixture shows an excellent cycling stability with an increase in the specific capacity of about 150 mAh g-1 compared to its analogues pyrolysed in pure argon atmosphere.
In order to study the role of porosity towards the lithium storage properties, a comparison of dense and porous materials obtained using same starting precursors is made. Porous SiOC ceramics are prepared by HF etching of the SiOC ceramics. HF etching removes a part of the amorphous silica phase from SiOC nanostructure leaving a porous structure. Porous ceramics with surface areas up to 640 m2 g-1 is obtained. The electrochemical charging/discharging results indicate that the porosity can help to increase the lithium storage capacity and it also leads to an enhanced cycling stability.
This work demonstrates clearly that silicon oxycarbide (SiOC) ceramics present excellent electrochemical properties to be applied as a promising anode material for lithium storage applications.
9
Vallachira, Warriam Sasikumar Pradeep Pradeep. "Study of Silicon Oxycarbide(SiOC) as Anode Materials for Li-ion Batteries." Doctoral thesis, University of Trento, 2013. http://eprints-phd.biblio.unitn.it/1112/1/PhD_Thesis_Vallachira_Pradeep.pdf.
Full textAbstract:
The principal object of this thesis is the investigation of silicon oxycarbide (SiOC) ceramics as anode material for Li-ion batteries. The investigated materials are prepared by cross linking commercial polymer siloxanes via hydrosylilation reactions or hybrid alkoxide precursors via sol-gel. The cross linked polymer networks are then converted in to ceramic materials by a pyrolysis process in controlled argon atmosphere at 800-1300 °C.
In details the influence of carbon content on lithium storage properties is addressed for SiOC with the same O/Si atomic ratio of about 1. Detailed structural characterization studies are performed using complementary techniques which aim correlating the electrochemical behavior with the microstructure of the SiOC anodes. Results suggest that SiOC anodes behave as a composite material consisting of a disordered silicon oxycarbide phase having a very high first insertion capacity of ca 1300 mAh g-1 and a free C phase. However, the charge irreversibly trapped into the amorphous silicon oxycarbide network is also high. In consequence the maximum reversible lithium storage capacity of 650 mAh g-1 is measured on high-C content SiOCs with the ratio between amorphous silicon oxycarbide and the free C phase of 1:1. The high carbon content SiOC shows also an excellent cycling stability and performance at high charging/discharging rate with the stable capacity at 2C rate being around 200 mAh g-1.
Increasing the pyrolysis temperature has an opposite effect on the low-C and high-C materials: for the latter one the reversible capacity decreases following a known trend while the former shows an increase of
xi
the reversible capacity which has never been observed before for similar materials.
The influence of pyrolysis atmosphere on lithium storage capacity is investigated as well. It is found that pyrolysis in Ar/H2 mixtures, compared to the treatment under pure Ar, results into a decrease of the concentration of C dangling bonds as revealed by electron spin resonance (ESR) measurements. The sample prepared under Ar/H2 mixture shows an excellent cycling stability with an increase in the specific capacity of about 150 mAh g-1 compared to its analogues pyrolysed in pure argon atmosphere.
In order to study the role of porosity towards the lithium storage properties, a comparison of dense and porous materials obtained using same starting precursors is made. Porous SiOC ceramics are prepared by HF etching of the SiOC ceramics. HF etching removes a part of the amorphous silica phase from SiOC nanostructure leaving a porous structure. Porous ceramics with surface areas up to 640 m2 g-1 is obtained. The electrochemical charging/discharging results indicate that the porosity can help to increase the lithium storage capacity and it also leads to an enhanced cycling stability.
This work demonstrates clearly that silicon oxycarbide (SiOC) ceramics present excellent electrochemical properties to be applied as a promising anode material for lithium storage applications.
10
VERSACI, DANIELE. "Materials for high energy Li-ion and post Li-ion batteries." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2896992.
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