High-Voltage Fluoride-Free Electrolytes for Ni-Rich Cathodes Offering Superior Water Resistance

To enhance the range of electric vehicles (EVs), high-nickel (Ni) layered oxide cathode materials are increasingly favored in power battery design. However, Ni-rich cathodes face significant challenges regarding cycling stability, particularly in humid conditions, where their lifespan deteriorates rapidly. Herein, we present a sustainable high-voltage fluoride-free electrolyte (HVFFE) that is compatible with LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes operating at a cutoff voltage of 4.4 V and exhibiting superior water resistance. The fluoride-free nature of this electrolyte prevents the formation of hydrofluoric acid (HF) upon exposure to moisture, which commonly degrades Ni-rich cathodes. The HVFFE facilitates the formation of a robust cathode-electrolyte interphase (CEI) enriched with sulfur, boron, oxygen, and nitrogen (S/B/O/N), effectively stabilizing the cathode structure and minimizing active material degradation. Electrochemical testing reveals that even with the addition of 1000 ppm of water, this electrolyte enables Li-NCM811 cells to maintain a capacity of over 100 mAh g–1 at a 10 C discharge rate and supports stable cycling for more than 500 cycles at 2 C, with 94.7% capacity retention. More importantly, a high-loading Li-NCM811 full cell using HVFFE with 1000 ppm of H2O maintained stability over 200 cycles, achieving an average Coulombic efficiency of 99.61%.