高浓度电解液对电极/电解液界面的影响

Effects of concentrated electrolytes on the electrode/electrolyte interface

高浓度电解液作为目前提高锂离子电池能量密度的重要途径,因其具有与低浓度电解液不同的特性而对锂离子电池电极/电解液界面的结构、化学组成及稳定性有着非常重要的调控作用,从而在改善电池体系的安全、循环稳定以及高倍率等电化学综合性能方面有广阔的应用前景。本文主要综述了相对于低浓度电解液,高浓度电解液在近几年的应用中所体现的特殊优势,发现高浓度电解液在拓宽电解液电化学稳定窗口、抑制铝集流体腐蚀和防止石墨剥离等提高电解质与电极相容性方面取得了理想的效果。本文重点分析了高浓度电解液锂盐浓度对电极/电解液界面的影响机理,其中包括锂盐浓度的增加对锂盐阴离子在双电层中占位,锂盐阴离子与溶剂、锂离子之间形成的溶剂化结构以及对界面膜的结构和化学组成的改变,最终形成了薄而致密的界面膜。本文介绍了现有新型表征技术在高浓度电解液中特殊溶剂化结构和电极/电解液界面成膜过程中的应用,最后对高浓度电解液未来的发展和研究方向进行了展望。

As an important way to improve the energy density of lithium-ion batteries is to utilize concentrated electrolytes. Concentrated electrolytes are able to regulate the structure, chemical composition, and stability of the interface between electrolytes and electrodes in lithium-ion batteries because of their differences from low-concentration electrolytes. The features of concentrated electrolytes have a potential broad application in improving the comprehensive electrochemical performance of batteries including the safety, cycle stability, and discharge rate. The special advantages of concentrated electrolytes compared with low-concentration electrolytes in recent years were reviewed in this article. It was found that concentrated electrolytes had the ability to widen the electrochemical stability window of electrolytes, inhibit the corrosion of aluminum current collectors,prevent graphite stripping, and other markers of improved compatibility between electrolytes and electrodes. We focused on the mechanism analysis of concentrated electrolytes on the electrode/electrolyte interface with increased lithium salt concentration, including the occupation of lithium salt anions in the electric double layer and solvated structures formed from lithium salt anions, solvents, and lithium ions. The structural and chemical composition of the interface film was also analyzed, along with its ability to form a thin and dense interface film. The application of new characterization techniques to the special solvation structure generated in the film formation process of concentrated electrolytes at the electrode/electrolyte interface were introduced, and the future development and research direction of concentrated electrolytes were also discussed.