Hydrangea-like δ-MnO2 anchored on GNS as a high-performance supercapacitor electrode material

Abstract

Manganese dioxide is attractive for energy storage but still needs to be combined with highly conductive materials to improve its electrochemical properties. In this paper, δ-MnO₂/GNS composites with three-dimensional structures were synthesized by anchoring hydrangea-like δ-MnO₂ on graphene substrates. Physicochemical analysis shows that δ-MnO₂ is uniformly anchored on the graphene surface, and adjacent hydrangea-like δ-MnO₂ self-assembles to build a three-dimensional conductive network, and this special structure not only provides abundant surface active sites but also more fast channels for electron transport during electrochemical reactions. The optimized composite (δ-MnO₂/GNS-1.8) exhibited excellent electrochemical performance with a high specific capacitance of 326.6 F g⁻¹ at a current density of 0.2 A g⁻¹ and a cycling performance of 97.1%. Asymmetric supercapacitors assembled with δ-MnO₂/GNS and activated carbon (AC) exhibited energy densities up to 42.2 W h kg⁻¹ at a power density of 196.8 W kg⁻¹. Hydrangea-like δ-MnO₂ anchored on GNS has great potential for application as a high-performance supercapacitor electrode material.