Trimethoxyboroxine as an electrolyte additive to enhance the 4.5 V cycling performance of a Ni-rich layered oxide cathode

Ni-rich layered oxides are attractive cathode materials for advanced lithium-ion batteries (LIBs) due to their high energy density. However, their large-scale application is seriously hindered by their interfacial instability, especially at a high cut-off potential. Here, we demonstrate that trimethoxyboroxine (TMOBX) is an effective film forming additive to address the interfacial instability of LiNi0.8Co0.1Mn0.1O2 (NCM811) material at a high cut-off voltage of 4.5 V. We find that TMOBX decomposes before carbonate solvent and forms a thin cathode electrolyte interphase (CEI) layer on the surface of the NCM811 material. This TMOBX-formed CEI significantly suppresses electrolyte decomposition at a high potential and inhibits the dissolution of transition metals from NCM811 during cycling. In addition, electron-deficient borate compounds coordinate with anions (PF6-, F-, etc.) and H2O in the battery, further improving the battery's stability. As a result, adding 1.0 wt% of TMOBX boosts the capacity retention of a Li||NCM811 cell from 68.72% to 86.60% after 200 cycles at 0.5C in the range of 2.8-4.5 V.