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

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 LiPF6 and LiNO3 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, PF6 - and NO3 - , 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 LiǁLiNi0.85 Co0.10 Al0.05 O2 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.