碳酸乙烯酯
电解质
碳酸二甲酯
介电谱
碳酸盐
石墨
钝化
化学
材料科学
化学工程
无机化学
电化学
分析化学(期刊)
电极
色谱法
纳米技术
有机化学
催化作用
物理化学
图层(电子)
工程类
作者
Lin Ma,Stephen Glazier,R. Petibon,Jian Xia,Jeremy M. Peters,Q. Liu,J. P. Allen,Renny Doig,J. R. Dahn
出处
期刊:Journal of The Electrochemical Society
[The Electrochemical Society]
日期:2016-11-17
卷期号:164 (1): A5008-A5018
被引量:114
摘要
Li[Ni0.42Mn0.42Co0.16]O2 (NMC442)/graphite pouch cells demonstrate superb performance at high voltage when ethylene carbonate (EC)-free electrolytes, using a solvent mixture that is >95% ethyl methyl carbonate (EMC) and between 2 and 5% of an "enabler", are used. The "enablers", required to passivate graphite during formation, can be vinylene carbonate (VC), methylene-ethylene carbonate (MEC), fluoroethylene carbonate (FEC) or difluoro ethylene carbonate (DiFEC), among others. In order to optimize the amount of "enabler" added to EMC, gas chromatography coupled with mass spectrometry (GC-MS) was used to track the consumption of "enabler" during the formation step. Storage tests, electrochemical impedance spectroscopy (EIS), ultrahigh precision coulometry (UHPC), long-term cycling, differential voltage analysis and isothermal microcalorimetry were used to determine the optimum amount of enabler to add to the cells. It was found that the graphite negative electrode cannot be fully passivated when the amount of "enabler" is too low resulting in gas production and capacity fade. Using excess "enabler" can cause large impedance and gas production in most cases. The choice of "enabler" also impacts cell performance. A solvent blend of 5% FEC with 95% EMC (by weight) provides the best combination of properties in NMC442/graphite cells operated to 4.4 V. It is our opinion that the experiments and their interpretation presented here represent a primer for the design of EC-free electrolytes.
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