锂电池中固体电解质界面研究进展

Research Progress of Solid Electrolyte Interphase in Lithium Batteries

锂离子电池在电子产品和电动汽车等领域已得到广泛应用,同时具有更高比能量的锂离子电池和锂金属电池也在不断研发中。电极界面的研究在推动电池的研发和产业化过程中发挥重要作用,因为电池在首次充放电过程中电解液组分在电极/电解质界面上发生氧化/还原反应并形成离子导通、电子绝缘性质的界面膜,界面膜对于维持电极结构的完整性、保障锂离子快速迁移和防止电解液持续分解十分关键,因此其稳定性与电池的循环性能和使用寿命密切相关。本文综述了固体电解质界面(SEI)的研究进展,首先介绍了SEI在初次充放电阶段对电位的依赖性,讨论SEI的形成机理,具体分析了影响SEI形成的两个关键因素,即电极表面的离子特性吸附和电解液体相的溶剂化组成和结构;其次,梳理总结了界面的结构与化学组成研究进展,及锂离子在界面中可能的传导机制;此外还简要概述了影响界面膜的因素和调控界面膜的策略;最后对SEI在未来的研究方向进行了展望。

Since their commercialization in 1991, lithium-ion batteries(LIBs), one of the greatest inventions in history, have profoundly reshaped lifestyles owing to their high energy density, long lifespan, and reliable and safe operation. The ever-increasing use of portable electronics, electric vehicles, and large-scale energy storage has consistently promoted the development of LIBs with higher energy density, reliable and safe operation, faster charging, and lower cost. To meet these stringent requirements, researchers have developed advanced electrode materials and electrolytes, wherein the electrode materials play a key role in improving the energy density of the battery and electrolytes play an important role in enhancing the cycling stability of batteries. In addition, further improvements in the current LIBs and reviving lithium metal batteries have received intensive interest. The electrode/electrolyte interface is formed on the electrode surface during the initial charging/discharging stage, whose ionic conductivity and electronic insulation ensure rapid transport of lithium ions and isolating the unsolicited side reactions caused by electrons, respectively. In a working battery, the stability or properties of the interface play a crucial role in maintaining the integrity of the electrode structure, thereby stabilizing the cycling performance and prolonging the service lifespan to meet the sustainable energy demand for the public. Generally, the interface formed on the anode and cathode is called the solid electrolyte interphase(SEI) and cathode electrolyte interphase(CEI) respectively, and SEI and CEI are collectively known as the electrode electrolyte interphase. Research on SEI has made remarkable progress;however, the structure, component, and accurate regulation strategy of SEI are still at the initial stage due to the stability and complexity of SEI and the limited research methods at the nanoscale. To improve the performance and lifespan of working batteries, the formation, evolution, and modification of the interface should be paid particular attention. Herein, the latest researches focused on the SEI are reviewed, including the formation mechanism, which discusses two key factors affecting the formation of the electrode/electrolyte film, i.e., the ion characteristic adsorption on the electrode surface and the solvated coordinate structure, evolution, and description that contains the interface layer structure, wherein the mosaic model and the layered structure are the two mainstream views of the SEI structure, and the chemical composition of SEI as well as the possible conduction mechanism of lithium ions, including desolvation and subsequent diffusion across the polycrystalline SEI. The regulation strategies of the interface layer are discussed in detail, and the future prospects of SEI are presented.