基于微米合金负极的锂离子电解液的设计及界面机理研究

以Si、Al等为代表的合金负极具有容量高、电位适宜等优点，被认为是新一代锂离子电池的最佳负极材料之一。但由于与目前的碳酸乙烯酯（EC）基电解液不匹配，此类微米合金负极的电化学性能难以满足锂离子电池的应用要求。为此，结合申请人的前期工作积累，本项目提出开发适用于微米合金负极的新型电解液的策略以解决其循环寿命短、库伦效率低等限制其应用的关键问题。系统考察2-甲基四氢呋喃等新型电解液体系中电解液组成对合金负极脱嵌锂行为的影响，综合运用先进结构和界面表征方法结合第一性原理分子动力学理论计算深入分析合金负极与新型电解液体系的界面反应过程和固体电解质界面层（SEI）成分组成、微观结构等。阐明界面反应机理、SEI组成和结构对合金负极性能影响的作用机制，探索出改善微米合金负极电化学性能的全新途径。本项目的实施有助于推进微米合金负极在高能量密度锂离子电池方面的实用化进程，具有重要的科学意义和应用前景。

The alloy anode, such as Si, Al, etc. is regarded as one of the most promising Li-ion battery anodes due to the high capacity and favorable potential. However, because of the incompatibility between the micro-sized alloy anodes and EC-based carbonate electrolytes, the cycling performance and Coulombic efficiency cannot suffice to support the Li-ion batteries upon long-term cycling. To overcome these critical issues, based on our earlier work, in this project we propose to design novel electrolytes to cater to electrochemical features of the alloy anodes, in which the influence of the solvents (such as 2-Methyltetrahydrofuran), salts, and concentrations on the lithiation/delithiation of the alloy anodes will be systematically investigated. The interphasial chemistries, solid electrolyte interphase (SEI) compositions and the microstructures between the alloy anodes and the novel electrolytes will be intensively explored by using advanced structural and interphasial characterizations, density functional theory (DFT) and molecular dynamic (MD) calculations. The interactions between the electrochemical performance of the alloy anode and the interphasial microstructures and SEI compositions will be clarified. It is believed that the implementation of the proposal would greatly promote the practical applications of the micro-sized alloy anodes in the high energy Li ion batteries, which is of extensive interest to a broad audience working on energy storage technologies as well as electrochemistry in general.