Hybrid Electrolyte with Dual‐Anion‐Aggregated Solvation Sheath for Stabilizing High‐Voltage Lithium‐Metal Batteries

Abstract Lithium (Li)‐metal batteries (LMBs) with high‐voltage cathodes and limited Li‐metal anodes are crucial to realizing high‐energy storage. However, functional electrolytes that are compatible with both high‐voltage cathodes and Li anodes are required for their developments. In this study, the use of a moderate‐concentration LiPF 6 and LiNO 3 dual‐salt electrolyte composed of ester and ether co‐solvents (fluoroethylene carbonate/dimethoxyethane, FEC/DME), which forms a unique Li + solvation with aggregated dual anions, that is, PF 6 − and NO 3 − , is proposed to stabilize high‐voltage LMBs. Mechanistic studies reveal that such a solvation sheath improves the Li plating/stripping kinetics and induces the generation of a solid electrolyte interphase (SEI) layer with gradient heterostructure and high Young's modulus on the anode, and a thin and robust cathode electrolyte interface (CEI) film. Therefore, this novel electrolyte enables colossal Li deposits with a high Coulombic efficiency (≈98.9%) for 450 cycles at 0.5 mA cm −2 . The as‐assembled LiǁLiNi 0.85 Co 0.10 Al 0.05 O 2 full batteries deliver an excellent lifespan and capacity retention at 4.3 V with a rigid negative‐to‐positive capacity ratio. This electrolyte system with a dual‐anion‐aggregated solvation structure provides insights into the interfacial chemistries through solvation regulation for high‐voltage LMBs.