Reinterpreting the correlation between cycling stability of Ni-rich layered oxide cathode and the charging cut-off voltage in Li-ion batteries

Conventional view is that increasing the charging cut-off voltage will reduce the cycle life of LiNi0.8Co0.1Mn0.1O2 (NCM811) due to the intensification of electrode-electrolyte interface reaction, which strongly depends on the interface chemistry. However, we found the different trend when NCM811 is cycled in TLE electrolyte (ternary fluorinated lithium salts electrolyte). Specifically, the higher charging cut-off voltage applied, the better cycling stability obtained with 1000 cycles at 4.5 V/4.7 V, while 500 cycles at 4.3 V (capacity retention > 80 %). Herein, we revisit the correlation between cycling stability and charging cut-off voltage and have found that the cycling stability of NCM811 is more strongly related to interface chemistry. Charging at 4.5/4.7 V in TLE electrolyte, the content of inorganic components in cathode-electrolyte-interphase (CEI) and anode-electrolyte-interphase (AEI) are much higher than that obtained at 4.3 V due to the energy levels of the frontier molecular orbital of lithium salts, which is more resistant to oxidation and has higher mechanical strength to suppress the particle cracks. More importantly, the inorganic rich interface can prevent the crossover reaction between cathode and anode. This work clarifies the significance of interface chemistry to achieve high-voltage stability, and provides a valuable electrolyte formula for commercial application of high-performance Ni-rich layered oxide cathode at high-voltage.