"Water-in-Salt" Electrolyte Suppressed MnVOPO·2HO Cathode Dissolution for Stable High-Voltage Platform and Cycling Performance for Aqueous Zinc Metal Battery.

Vanadium-based materials have the advantages of abundant valence states and stable structures, having great application potential as cathode materials in metal-ion batteries. However, their low voltage and vanadium dissolution in traditional water-based electrolytes greatly limit their application and development in aqueous zinc metal batteries (AZMBs). Herein, phosphate- and vanadium-based cathode materials (MnVOPO·2HO) with stacked layers and few defects were prepared via a condensation reflux method and then combined with a high-concentration electrolyte (21 m LiTFSI + 1 M Zn(CFSO)) to address these limitations. The specific capacity and cycle stability accompanying the stable high voltage of 1.39 V were significantly enhanced compared with those for the traditional electrolyte of 3 M Zn(CFSO), benefiting from the suppressed vanadium dissolution. The cathode materials of MnVOPO·2HO achieved a high specific capacity of 152 mAh g at 0.2 A g, with a retention rate of 86% after 100 cycles for AZMBs. A high energy density of 211.78 Wh kg was also achieved. This strategy could illuminate the significance of electrolyte modification and provide potential high-voltage cathode materials for AZMBs and other rechargeable batteries.