Tailoring electrolyte enables high-voltage Ni-rich NCM cathode against aggressive cathode chemistries for Li-ion batteries

Abstract

The LiNi0.8Co0.1Mn0.1O2 (Ni-rich NCM) cathode materials suffer from electrochemical performance degradation upon cycling due to detrimental cathode interface reactions and irreversible surface phase transition when operating at a high voltage (≥4.5 V). Herein, a traditional carbonate electrolyte with lithium difluoro(oxalato)borate (LiDFOB) and tris(trimethylsilyl)phosphate (TMSP) as dual additives that can preferentially oxidize and decompose to form a stable F, B and Si-rich cathode-electrolyte interphase (CEI) that effectively inhibits continual electrolyte decomposition, transition metal dissolves, surface phase transition and gas generation. In addition, TMSP also removes trace H2O/HF in the electrolyte to increase the electrolyte stability. Owing to the synergistic effect of LiDFOB and TMSP, the Li/LiNi0.8Co0.1Mn0.1O2 half cells exhibit the capacity retention 76.3% after 500 cycles at a super high voltage of 4.7 V, the graphite/LiNi0.8Co0.1Mn0.1O2 full cells exhibit high capacity retention of 82.8% after 500 cycles at 4.5 V, and Li/LiNi0.8Co0.1Mn0.1O2 pouch cells exhibit high capacity retention 94% after 200 cycles at 4.5 V. This work is expected to provide an effective electrolyte optimizing strategy compatible with high energy density lithium-ion battery manufacturing systems.