A High‐Humidity–Tolerant Electrolyte for High‐Voltage Lithium–Metal Batteries

ABSTRACT Lithium–metal batteries (LMBs) paired with high‐voltage cathodes hold considerable commercial promise. Their practical deployment, however, remains hindered by persistent challenges such as electrolyte decomposition at high voltages (>4.4 V vs. Li/Li ⁺ ), lithium dendrite growth, and interfacial instability. Furthermore, the pronounced hygroscopicity of advanced electrolytes imposes stringent drying requirements during manufacturing, increasing complexity, and cost and thereby obstructing scalable, cost‐effective production. Herein, we develop a humidity‐tolerant, high‐voltage electrolyte by incorporating perfluorooctyltriethoxysilane (PFOTS) as a co‐solvent into fluorinated carbonates. The weak solvation of PFOTS with Li ⁺ forms a molecular hydrophobic shield, enabling efficient water scavenging and suppressing LiPF ₆ hydrolysis. PFOTS also preferentially decomposes to form a robust electrode–electrolyte interphase. Consequently, Li/LiNi _0.8 Co _0.1 Mn _0.1 O ₂ cells achieves 90% capacity retention after 600 cycles at 4.4 V and 87% after 400 cycles at 4.7 V. Remarkably, with 0.5 vol% added water (corresponding to a dew point of 15°C), the cell maintains 80% retention after 150 cycles. This unique electrolyte system not only significantly enhances the high‐voltage performance of LMBs, but also alleviates the stringent humidity control requirements during manufacturing.