Insight into the interaction between Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode and BF4−-introducing electrolyte at 4.5 V high voltage

Owing to the high specific capacity and high voltage, Ni-rich (LiNi0.8Co0.1Mn0.1O2, LNCM811) cathode has been considered as one of the most promising candidate cathode materials for next generation lithium ion batteries, whereas severe capacity fading greatly hinders its practical application. Notably, the compatibility of Ni-rich materials with LiBF4-containing electrolyte has not yet been realized. Herein, 1 M LiPF6-based electrolyte with introducing 2 M LiBF4 is proposed to dramatically improve the cyclic stability of high voltage LNCM811/Li half-cell. Addition of high concentrated LiBF4 improves the moisture stability of electrolyte, which hinders the generation of harmful by-product HF, resulting in improved interfacial stability of LNCM811. Lithium plating/stripping reaction of Li/Li symmetric cell confirms that the enhanced cyclic stability is ascribed to the improved interfacial stability of LNCM811 instead of lithium electrode. Morphology and composition characterization results reveal that LiBF4 participates in the CEI film-forming reaction, resulting in suppressed oxidation of electrolyte and interfacial structural destruction of LNCM811.