Abstract
Lithium‐ion batteries (LIBs) employing high‐nickel layered oxide cathodes are regarded as highly promising candidates for high energy density. However, operating Ni‐rich cathodes at elevated cut‐off voltage accelerates electrolyte decomposition and irreversible structural deterioration. To address these obstacles, we developed a bifunctional LiPF
6
‐based carbonate electrolyte which strategically incorporates trimethoxyboroxine (TMBO) and 1,3,6‐hexanetricarbonitrile (HTCN) additives to concurrently stabilize the cathode–electrolyte interphase (CEI) and the bulk electrolyte. The designed electrolyte preferentially oxidizes to form a robust CEI enriched in LiF and B─O species, effectively isolating the cathode from direct contact with the electrolyte and suppressing transition metals dissolution. In addition, the stability of electrolyte is improved by suppressing electrolyte decomposition and HF generation, thereby mitigating cathode structural degradation. Consequently, the designed electrolyte enables exceptional long‐term cycling stability, the Li//NCM811 cell with a high mass loading of 12 mg cm
−2
retain 80.5% of its initial capacity after 200 cycles at 4.6 V. Furthermore, the Ah‐level NCM811//Si–C pouch cell achieves long‐term cycling over 400 cycles with a capacity retention of 82.2% at 4.5 V. This work provides an effective approach to electrolyte optimization for high‐voltage LIBs and offers important guidance for the design of multifunctional additives.