Doping-Induced Static Activation of MnO₂ Cathodes for Aqueous Zn-Ion Batteries

Abstract

Electrochemical activation has been confirmed to be a powerful strategy to improve the Zn2+ storage activity of MnO2-based cathodes. A pivotal challenge of electrochemical activation is the poor cycling stability of activated cathodes upon Zn2+ (de)intercalation due to the dissolution of active materials in the electrolyte, the structural degeneration of pristine cathode materials, and the complicated dynamic electrochemical process. In this study, we report a novel doping-induced static activation method to induce the formation of active Zn3V2O7(OH)2·2H2O (ZVO) on the surface of a highly V-doped MnO2 (VMO) cathode by simply placing the cathode in an aqueous ZnSO4 electrolyte for 10 days. Our method not only significantly improves the Zn2+ storage activity of the pristine VMO cathode but also successfully tackles these problems of electrochemical activation. The activated cathode (VMO/ZVO) delivers a significantly increased initial capacity of 262 mA h g–1 and a high capacity retention of 99% after 100 cycles based on a H+/Zn2+ synergetic pseudocapacitive mechanism. The proposed static activation strategy holds great potential in the fabrication of high-activity cathodes for aqueous Zn-ion batteries.