摘要/Abstract

三元层状氧化物{Li[Ni_xCo_yM_z]O₂（0 < x，y，z < 1，M＝Mn，缩写NMC；M＝Al，缩写NCA）}具有能量密度高、循环性能好、价格适中等优异的综合性能，是目前锂离子电池（LIBs）中最具应用前景的一类正极材料.随着纯电动汽车（EVs）及混合电动汽车（HEVs）的快速发展，人们对LIBs的能量密度、循环寿命以及安全性要求不断提高.然而，在传统电解液体系中，三元正极材料在高电压、高温下会发生剧烈的结构变化和界面副反应，给实际应用带来巨大挑战，尤其是高镍三元材料的循环寿命和安全性.其中，开发适配的电解液添加剂是提高锂离子电池电化学性能最经济有效的方法之一.从物质本征结构出发，综述了近5年来包括碳酸亚乙烯酯（VC）、氟代物、新型锂盐、含P、含B、含S、腈类等及其复合物作为电解液添加剂在NMC及NCA正极材料中的应用及作用机理，并进行总结与展望.
关键词: 锂离子电池, NMC及NCA三元材料, 电解液添加剂, 作用机理
Ternary layered oxides {Li[Ni_xCo_yM_z]O₂ (0 < x, y, z < 1, M=Mn, NMC; M=Al, NCA)} are one of the most promising cathode materials of lithium-ion batteries (LIBs). However, in the traditional electrolyte system, they will undergo dramatic structural changes and interface side reactions at high potential and high temperature, which will bring great challenges to their practical application, especially for their cycle life and safety. Developing appropriate electrolyte additive is one of the most economical and effective methods to improve the electrochemical performance of LIBs. Based on the intrinsic structure of material, electrolyte additives used for NMC and NCA ternary cathode and their reaction mechanism in the past 5 years are reviewed in this paper, which include vinylene carbonate (VC), fluoro-compounds, new lithium salts, P-based, B-based, S-based, nitrile, others and combinative additives. Among them, VC becomes a kind of universal additive, which can improve the efficiency and cycle life at low voltage and normal temperature. Fluoro-compounds have been developed from mono substituted such as Fluorinated ethylene carbonate (FEC) to multi-fluorine substituted, which can improve the stability of electrode/electrolyte interface under high voltage. New lithium salt additives are mainly used to improve the film forming performance under high voltage and high temperature, such as Lithium bis(fluorosulfonyl)imide (LiFSI), Lithium difluorophosphate (LiDFP). P-contained additives[such as Tris(trimethylsilyl) phosphite (TMSPi)] are mainly to improve the stability of anode-electrolyte interface, and it has obvious synergistic effect when they combined with additives such as VC. B-contained additives are mainly used to improve the dissociation degree and stability of lithium salt, such as Tris(trimethylsilyl)borate (TMSB). S-contained additives are mainly used to improve the ionic conductivity and stability of anode SEI film, such as Prop-1-ene-1,3-sultone (PES). Nitriles are benefited from the strong electron withdrawing effect of -CN, which can improve the stability of the electrode/electrolyte interface at high voltage. Other types of additives are some heterocyclic compounds having film forming ability and various silanes which can eliminate HF and H₂O. Combinative addi-tives are developed from VC based composite to PES and PBF (pyridine boron trifluoride) system, which can endure even harsher conditions.
Key words: lithium-ion battery, NMC and NCA ternary material, electrolyte additives, mechanism


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