An Interfacial Mechanism of Chelate-Borate Electrolyte Additives in Ni-Rich LiNi0.8Mn0.1Co0.1O2 Cathodes

The Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) material is considered one of the most potential cathode materials because of its high capacity, high voltage, and high lithium-ion (Li+) diffusion coefficient. However, the oxidation and decomposition of electrolytes at high potential lead to the failure of NMC811. Herein, lithium bis(oxalate) (LiBOB) and lithium difluoro(oxalato)borate (LiODFB) electrolyte additives are introduced to inhibit side reactions on the surface of the material. Results reveal that BxOy can be introduced into the passive cathode–electrolyte interphase (CEI) film by the oxidative decomposition of LiBOB and LiODFB additives, which not only develops the diffusion of Li+ but also helps suppress the dissolution of transition-metal (TM) ions. In addition, compared with LiBOB additives, the CEI film formed by LiODFB preferential decomposition is thin, uniform, and dense and contains more inorganic substances, which reduces the decomposition of the electrolyte, optimizes the composition of the CEI film, and reduces the resistance of Li+ transport. This finding is expected to be useful for the development of electrolyte additives with potential use for promoting the formation of good CEI film.