Benzoic Anhydride as a Bifunctional Electrolyte Additive for Hydrogen Fluoride Capture and Robust Film Construction over High‐Voltage Li‐Ion Batteries

Abstract High‐voltage LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811)‐based Li‐ion batteries (LIBs) with enhanced performance can be achieved by properly tailoring the electrolyte systems. Benzoic anhydride (BA) was proposed here as a promising bifunctional electrolyte additive that can not only construct a robust cathode‐electrolyte interface (CEI) film on the electrode surface but also capture HF/H 2 O in the electrolyte effectively. Compared to the cell without the BA additive, the capacity of Li/NCM811 half‐cell with 1.0 wt % BA was increased from 128.5 to 149.6 mAh g −1 after 200 cycles at 1 C between 3.0 and 4.3 V. Even at a higher cut‐off voltage of 4.5 V, the BA‐containing Li/NCM811 half‐cell delivered a capacity retention of 69 % after 200 cycles, much higher than that of the half‐cell without the additive (56 %). Both theoretical calculation and experimental results verified that the BA additive could be preferentially oxidized to form a stable interface film with high conductivity that protected the NCM811 cathode and suppressed the decomposition of the electrolyte.