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 (approximate to 98.9%) for 450 cycles at 0.5 mA cm(-2). The as-assembled Li parallel to LiNi0.85Co0.10Al0.05O2 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.

Automated summary

This study proposed a dual-salt electrolyte with LiPF6 and LiNO3 to stabilize high-voltage LMBs, improving Li plating/stripping kinetics with a unique Li+ solvation and forming a uniform solid electrolyte interface (SEI) layer. The electrolyte system enabled large Li deposits with high Coulombic efficiency and excellent lifespan in full batteries at 4.3 V.