3-(Trifluoromethyl)benzoylacetonitrile: A multi-functional safe electrolyte additive for LiNi0.8Co0.1Mn0.1O2 cathode of high voltage lithium-ion battery

Abstract

The high nickel layered oxide cathode LiNi0.8Co0.1Mn0.1O2 (NCM811) is widely used in new energy power and equipment due to its high density and low cost. However, the NCM811 cathode is prone to structural rupture, dissolution of transition metal ions, and damage to the electrode/electrolyte interface under high voltage, causing degradation of battery performance and safety issues. In this paper, 3-(Trifluoromethyl)benzoylacetonitrile (3-TBL) was selected as a film-forming flame-retardant additive for the NCM811 cathode of the high-voltage lithium-ion battery, and the synergistic effect with lithium difluoro(oxalato)borate enhanced the battery cycle and safety performance. The results show that: 3-TBL is oxidized preferentially more than carbonate solvent to form a stable and dense cathode-electrolyte interface film, which effectively prevents the continuous oxidative decomposition of the electrolyte and enhances the rate of cycling and overcharge resistance of the Li/NCM811 cells under high pressure. Furthermore, the 3-TBL modified electrolyte can also delay the thermal decomposition temperature of the commercial electrolyte and improve its flame retardant properties. Kinetic analysis showed that the additive increased the activation energy required for the thermal decomposition reaction of electrolyte and NCM811 cathode mixture. Therefore, the additives 3-TBL improve the intrinsic safety of the electrolyte and electrolyte interface, providing a feasible idea for the development of high energy density and high safety electrolytes.