Conductive Robust Interfaces with Fluoro‐Borate Based Electrolyte Additive for 4.6 V Well‐Cycled LiNi_0.90Co_0.06Mn_0.04O₂||Li Batteries

Abstract

Owing to the outstanding comprehensive properties of high energy density, excellent cycling ability, and reasonable cost, Ni‐rich layered oxides (NCM) are the most promising cathode for lithium‐ion batteries (LIBs). To further enhance the specific capacity of Ni‐rich layered oxides, it is necessary to increase the cut‐off voltage to a higher level. However, a higher cut‐off voltage can lead to substantial structural changes and trigger interface side reactions, presenting significant challenges for practical applications (cycle life and safety). Herein, to solve above issues, tris(hexafluoroisopropyl)borate (TFPB) is introduced as a high voltage electrolyte additive for LiNi0.90Co0.06Mn0.04O2 cathode. Based on detail in situ/ex situ characterization, this study proves that TFPB forms a protective solid‐state interphase (SEI) layer on the Li‐anode. Additionally, derivatives of TFPB are easily oxidatively decomposed to create a dense cathode electrolyte interphase (CEI) film on the cathode. This CEI film effectively prevents the continuous oxidation of the electrolyte and mitigates the adverse effects of HF on the battery. Benefit from the protective SEI and CEI layer, the LiNi0.90Co0.06Mn0.04O2||Li battery with a TFPB‐containing electrolyte maintains an unprecedented level of performance, with a capacity retention of 89.1% after 100 cycles under the ultrahigh cut‐off voltage of 4.6 V (vs Li/Li+).