Vertically-aligned graphene@MnO nanosheets as binder-free high-performance electrochemical pseudocapacitor electrodes

Abstract

Highly efficient energy storage systems are in great demand for power source applications ranging from wearable electronics to hybrid electric vehicles. Graphene-based hybrid structure capacitors are ideal candidates for manufacturing these systems. Herein, we present the design and fabrication of heterostructured composites made of vertically aligned graphene nanosheets (VAGN) and MnO nanoparticles. Electrodes with various MnO mass contents were obtained by depositing nanosized MnO particles onto VAGN under different hydrothermal conditions. The VAGN served as an excellent backbone and electron collector, enhancing the specific capacitance of the VAGN/MnO electrode (37 wt% MnO) to 790 F g⁻¹ at a scan rate of 2 mV s⁻¹. The electrodes also showed high specific capacitance (381 F g⁻¹) with high active material loading content (80 wt% MnO), and outstanding cycling stability (80% retention after 4000 cycles at 10 A g⁻¹). These excellent electrochemical performances result from the particular three-dimensional structure of VAGN, which offers convenient access for electrolyte cations participating in the redox reaction of MnO. These composites show enormous potential for use in energy management applications.