锂离子电池电解液SEI成膜添加剂的研究进展

稳定的固体电解质界面（SEI）是提高锂离子电池电化学性能的关键，用电解液添加剂是改善锂离子电池性能最经济有效的方法之一。本文综述了近五年间包括不饱和酯化合物、含硫化合物、锂盐、无机化合物等作为电解液成膜添加剂在锂离子电池中的研究进展和作用机理，对它们的优缺点进行了评价，最后进行了总结和展望。未来成膜类添加剂的研究思路应该为：（1）应以有机物种为主，能够形成弹性模量小的SEI膜，便于适应阳极材料产生的膨胀行为。（2）添加剂要尽量保证形成的SEI膜与石墨等阳极材料产生良好的黏结，因此添加剂形成的聚合物的聚合度不能太小。（3）在没有性能极其优秀的成膜添加剂出现之前，添加剂的分子结构可以在现有的添加剂的基础上进行结构的优化或者官能团的设计。（4）重点攻关当前添加剂的应用的问题，提高添加剂的合成技术，降低合成成本。

Review of SEI film forming additives for electrolyte of lithium ion battery

A stable solid electrolyte interface (SEI) is the key to improving the electrochemical performance of the lithium-ion battery. Electrolyte additives are one of the most economical and effective methods to improve the performance of the lithium-ion battery. The existence of additives significantly improves the recyclability and service life of lithium-ion batteries, so it has been widely studied by researchers. This paper evaluates the research progress and action mechanism of unsaturated ester compounds, sulfur compounds, lithium salts and inorganic compounds as electrolyte film-forming additives in lithium-ion batteries in recent five years, evaluates their advantages and disadvantages and finally combines them with prospects. The future development trend of film-forming additives is proposed: (1) It is a general trend to use multiple additives or design new additives with multiple functional groups to make up for the shortcomings of a single additive in some aspects and facilitate the complementarity of functional advantages. (2) Quantum chemical calculation is an efficient method to screen film-forming additives, which is helpful to understand the action mechanism between additives and electrodes and speed up the research and development efficiency. (3) The characterization method of the SEI membrane needs to be further improved. To further study the action mechanism of additives, the in-situ analysis method can be considered in the future characterization process. The main ideas for developing film-forming additives in the future include: (1) The additives shall be mainly organic species, which can form SEI film with small elastic modulus, to adapt to the expansion behavior of anode materials. (2) The additive should try to ensure that the formed SEI film and graphite and other anode materials have good adhesion, so the polymerization degree of the polymer formed by the additive should not be too small. (3) Before there is no film-forming additive with excellent performance, the molecular structure of the additive should be similar to the current film-forming additive as far as possible, to facilitate industrial production. (4) Focus on the application of current additives, improve the synthesis technology of additives, reduce the synthesis cost, facilitate large-scale use, and benefit society.