Construction of oxygen vacancy-enriched manganese dioxide via liquid metal reduction for enhanced electrochemical performance

Abstract

As a typical supercapacitor electrode material, manganese dioxide (MnO₂) faces application challenges due to its inferior conductivity and specific capacitance, which falls significantly below its theoretical capacity. Herein, a novel method is proposed utilizing the reducibility of gallium-based liquid metal to modulate the oxygen vacancies of MnO₂ under mild ambient conditions. The introduction of oxygen vacancies can effectively enhance the conductivity of MnO₂ and create more electrochemical active sites, leading to improved charge storage capabilities. A specific capacitance of 327F g⁻¹ is achieved at a current density of 1 A g⁻¹ for oxygen vacancy-enriched MnO₂ (24-MnO_x), which is approximately 6 times that of pristine MnO₂ (0-MnO_x). The symmetric supercapacitor device assembled from 24-MnO_x exhibits an energy density of 24 Wh kg⁻¹ at a power density of 600 W kg⁻¹. Density Functional Theory (DFT) simulations reveal that the introduction of oxygen vacancies enhances the electrical conductivity of 24-MnO_x, and significantly promotes the diffusion of K⁺, leading to enhanced electrochemical performance. These results indicate that the reducibility of liquid metal can effectively modulate the oxygen vacancy concentration in MnO₂, providing new insights for designing high-performance supercapacitor electrode materials.