An aqueous symmetric supercapacitor based on Mn3O4 nanorods-graphene composites with 2 V-high voltage and enhanced energy density

Abstract

Symmetric supercapacitors are often thought to obtain only a narrow voltage range in aqueous electrolytes due to the low thermodynamic electrochemical window of water (1.23 V). Herein, we built a novel symmetric supercapacitor based on Mn3O4@RGO//Mn3O4@RGO (reduced graphene oxide), which maintains a high stable working voltage of 2 V in 1 M Na2SO4 aqueous electrolyte. Increasing the working voltage of the symmetric supercapacitor from 1.0 to 2.0 V can significantly improve the energy storage of the supercapacitor by more than 20 times. Moreover, the symmetric supercapacitor operating at the 2.0 V high voltage can deliver a remarkably high energy density of 42.2 Wh kg−1 at a power density of 500.0 W kg−1 and excellent cycling stability. This work is expected to bring an effective strategy to improve the electrochemical energy storage of metal oxide supercapacitor in aqueous electrolytes.