Enhanced Oxygen Vacancies of δ-MnO2 Nanosheets on Carbon Cloth via Fast Zn2+ Intercalation for Supercapacitor Electrodes with High Mass Loading

The practical application of MnO2 as electrode material for a supercapacitor is restricted by intrinsically lower electron and ion migration kinetics, especially at commercially available high mass loading. Electrochemical activation holds great promise in improving the electrochemical performance of MnO2 by introducing tunable defects within their interior structure. Herein, the fast electrochemical activation process of δ-MnO2 nanosheets grown on flexible carbon cloth (CC) was achieved through Zn2+ intercalation. The Zn2+ intercalated δ-MnO2 (A-MnO2) showed enhanced oxygen vacancies and increased specific surface area, which can bring reduced adsorption energy for Na+ ions and improved contact of electrode materials and electrolyte as well as accelerated charge transport, resulting in improved capacitive performance even at a high mass loading. The obtained A-MnO2/CC electrode delivered a high specific capacitance of 3240 mF cm–2 (202.5 F g–1 at a high mass loading of 16 mg cm–2) under the current density of 5 mA cm–2, which was 2.4 times higher than that of the pristine MnO2/CC electrode. Moreover, the asymmetric supercapacitor based on A-MnO2/CC with a high mass loading achieved an energy density of 0.36 mWh cm–2 at a power density of 5 mW cm–2. The fast electrochemical activation strategy through cation intercalation opens a promising way for boosting the capacitive performance of advanced nanostructured MnO2-based supercapacitor electrodes with high mass loading.