Capacitance and voltage matching between MnO₂ nanoflake cathode and Fe₂O₃ nanoparticle anode for high-performance asymmetric micro-supercapacitors

Planar micro-supercapacitors show great potential as the energy storage unit in miniaturized electronic devices. Asymmetric structures have been widely investigated in micro-supercapacitors, and carbon-based materials are commonly applied in the electrodes. To integrate different metal oxides in both electrodes in micro-supercapacitors, the critical challenge is the pairing of different faradic metal oxides. Herein, we propose a strategy of matching the voltage and capacitance of two faradic materials that are fully integrated into one high-performance asymmetric micro-supercapacitor by a facile and controllable fabrication process. The fabricated micro-supercapacitors employ MnO₂ as the positive active material and Fe₂O₃ as the negative active material, respectively. The planar asymmetric micro-supercapacitors possess a high capacitance of 60 F·cm^-3, a high energy density of 12 mW·h·cm^-3, and a broad operation voltage range up to 1.2 V.