Electrolyte Sustaining 4.5 V Li||NCM811 Batteries Cycled at 80°C

LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NCM811)‐based lithium metal batteries (LMBs) are widely regarded as promising candidates for next‐generation high‐energy‐density systems. However, under high‐temperature and high‐voltage conditions, severe interfacial side reactions between the electrolyte and electrodes are inevitably triggered, substantially impeding the practical development of LMBs. Herein, a mechanically and thermally robust LiF/LiB x O y ‐rich CEI on NCM811 via synergistic regulation of a LiBF 4 /LiDFOB dual‐salt electrolyte and a functional boron‐containing additive 2,4,6‐tris(3,4,5‐trifluorophenyl)boroxin (TTFPB) is rationally constructed. The LiBF 4 /LiDFOB dual‐salt system enhances electrolyte thermal and oxidative stability, while TTFPB reconstructs the Li + solvation structure by selectively excluding DFOB − from the primary solvation sheath and enriching BF 4 − coordination, thereby inducing an anion‐rich solvation structure. Meanwhile, TTFPB/DFOB − species preferentially decompose at the cathode interphase, generating a uniform and mechanically robust LiF/LiB x O y ‐rich CEI. This stabilized interphase effectively suppresses continuous electrolyte decomposition and mitigates transition‐metals ions (TMs) dissolution, also alleviates cathode phase transitions. Consequently, Li||NCM811 batteries with this electrolyte deliver 80.70% capacity retention after 350 cycles at 4.5 V. Notably, even under extreme operating conditions at 4.5 V and 80°C, the batteries retain 87.50% of their initial capacity after 100 cycles.