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 MnO 2 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 MnO 2 by introducing tunable defects within their interior structure. Herein, the fast electrochemical activation process of δ-MnO 2 nanosheets grown on flexible carbon cloth (CC) was achieved through Zn 2+ intercalation. The Zn 2+ intercalated δ-MnO 2 (A-MnO 2 ) 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-MnO 2 /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 MnO 2 /CC electrode. Moreover, the asymmetric supercapacitor based on A-MnO 2 /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 MnO 2 -based supercapacitor electrodes with high mass loading.