Crystal Surface and State of Charge Dependencies of Electrolyte Decomposition on LiMn2O4 Cathode
Crystal Surface and State of Charge Dependencies of Electrolyte Decomposition on LiMn2O4 Cathode
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DOI：
10.1149/2.009408jes
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发表时间：
2014-01-01
影响因子：
3.9
通讯作者：
Siegel, Donald J.
中科院分区：
文献类型：
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作者：
Kumar, Nitin;Leung, Kevin;Siegel, Donald J.
采用第一性原理计算研究了碳酸乙烯（EC）在锂离子电池（LIB）正极候选材料LiMn2O4 (LMO)（111）表面的初始分解反应。由于最近有关于LMO晶体形态对电池可循环性和界面膜稳定性影响的实验，界面反应的理论研究尤为及时[j - s]。Kim， K. Kim， W. Cho， W. H. Shin， R. Kanno， J. W. Choi, Nano Lett。生态学报，12,6358-6365（2012）。我们发现EC的降解是一个两步反应。第一步是速率决定反应，从EC中提取一个质子并转移到表面。第二步涉及质子抽离EC的开环，它的势垒更小。这两种反应都对模型电极的锂含量（即电荷状态）敏感。当阴极高电荷时，抽氢降解EC成为可行的反应途径。将其与LMO（100）表面的预测结果进行了比较，并根据本文预测的反应驱动力对LMO上纳米厚界面层的生长进行了推测，尽管LMO的操作势相对较小。(C) 2014电化学学会。版权所有。
First principles calculations are used to study the initial decomposition reactions of ethylene carbonate (EC) on the (111) surface of LiMn2O4 (LMO), a candidate for Li ion battery (LIB) cathode. Theoretical studies of interfacial reactions are particularly timely due to recent experiments on the effect of LMO crystal morphology on battery cyclability and interfacial film stability [J.-S. Kim, K. Kim, W. Cho, W. H. Shin, R. Kanno, and J. W. Choi, Nano Lett., 12, 6358-6365 (2012)]. We find that EC degradation is a two-step reaction. The first step is the rate determining reaction where a proton is abstracted from EC and transferred to the surface. The second step involves ring opening of the proton abstracted EC which turns out to have a smaller barrier. Both of these reactions are sensitive to the Li content, i.e. state of charge, of the model electrode. EC degradation via H-abstraction becomes a feasible reaction route when the cathode becomes more highly charged. Comparison with predictions on the (100) surface of LMO is discussed, and speculation on the growth of nanometer-thick interfacial layer on LMO despite its relatively modest operating potential are made in light of the reaction driving forces predicted in this work. (C) 2014 The Electrochemical Society. All rights reserved.