Asymmetric supercapacitors with high energy densities

Abstract

The low energy densities of supercapacitors (SCs) are generally limited by the used anodes. To develop SCs with high energy densities, Fe³⁺ modified V₂O₅@GQDs (m-V₂O₅@GQDs) and ZIF-67-derived nanoporous carbon loaded with Mn₃O₄ (C/N-Mn₃O₄) were synthesized. After their detailed characterization using electron microscopy, X-ray methods and electrochemical techniques, they were further utilized as the anode and the cathode, respectively, to construct asymmetric supercapacitors (ASCs). The as-synthesized m-V₂O₅@GQDs improve the poor conductivity of V₂O₅, contributing greatly to a specific capacitance of 761 F g⁻¹ at a current density of 2 A g⁻¹. With application of a cell voltage of 2 V, an energy density of up to 99.4 W h kg⁻¹ is achieved at a power density of 1000 W kg⁻¹. Such ASCs also exhibit outstanding cycling performance (95% of initial capacitance even after 10 000 charging/discharging cycles). This study thus provides a new way to design and construct ASCs with high energy densities.