EC和PC基溶剂化锂离子单电子还原机理的理论研究  

Mechanisms of EC and PC Solvated Li^+ in Li-ion Battery Electrolytes

作　　者：杨奇[1] 胡娜[1] 戴崟 吴阳[1] 

机构地区：[1]辽宁大学化学院,沈阳110036

出　　处：《化学通报》2014年第8期795-803,共9页Chemistry

基　　金：国家自然科学基金项目(21373104);辽宁省自然科学基金项目(20102088);辽宁省教育厅基金项目(L2011006)资助

摘　　要：锂离子电池电解液中溶剂化锂离子的还原反应对研究碳负极与电解液相界面相互作用、预测SEI膜形成机理至关重要。本文通过密度泛函方法(DFT)对EC和PC基电解液溶剂化锂离子得电子前后的结构信息、AIM、轨道等进行深入分析,利用过渡态和IRC理论研究EC和PC基电解液单电子还原反应历程。计算表明,PC溶剂化的Li+体系更加稳定,容易插入碳层使其粉化,EC溶剂化的Li+则更易得到电子,发生单电子还原反应。通过探讨Li+(EC)n和Li+(PC)n(n=1~4)还原反应历程中电子结构的变化,推测EC和PC单电子还原形成阴离子自由基的新历程。该历程能够更加合理地解释有机电解液在碳负极表面结合电子形成SEI膜的过程,为电解液的设计和选取提供理论基础。The single-electron reductive mechanism of solvated Li＋ in Li-icn battery （LIB） electrolytes is significant for understanding the interaction between the electrolyte and the graphite anode and the formation mechanism of the solid electrolyte interface （SEI） film. The density functional theory （DFT） calculations have been performed for the reduction reaction of solvents widely used in LIBs electrolytes, ethylene carbonate （ EC ） and propylene carbonate （ PC）, at the level of B3LYP/6-31 ＋ G （ d, p）. The electronic characteristics, atoms in molecules （AIM）, orbital analyses, and one-electron reductive decompositions of EC and PC are also investigated. The results indicate that the PC-based electrolyte has a stronger interaction with Li ~ ~han EC does, and the PC prefers to intercalate with Li＋ into the graphite layers which always cause exfoliation of graphite. On the other hand, the EC- based electrolyte is preferable to undergo a fast ring-opening decomposition via a 3-solvated Li ＋ intermediate. The analysis on the HOMO orbital suggests a new reduction mechanism of EC and PC solvated Li＋ , which is used to illustrate the fundamental difference between EC and PC in the behavior of the SEI film formation.

关 键 词：锂离子电池 溶剂化作用 单电子还原机制 密度泛函理论 轨道分析 

分 类 号：O641[理学—物理化学] TM912[理学—化学]