Pre-activation strategy of α-MnO2 electrode to construct high-performance asymmetric sodium-ion supercapacitors

Aqueous asymmetric sodium-ion supercapacitors (ASSCs) with high energy density assembled from all-inorganic materials are expected to provide high-efficiency power sources for intelligent electric vehicles and off-grid systems. However, it is still challenging to fabricate high-performance positive materials by a simple method and rationally assemble ASSCs to meet the demand of ultralong cycle life and high energy/power density. Here, a simple pre-activation strategy was introduced into the α-MnO 2 electrode with a microcrystalline nanosheet structure to improve the Na-storage performance. The sodium-ions concentration was optimized by tuning charge-discharge parameters. Impressively, the pre-activated electrode achieved superior capacitance retention after 10,000 cycles, high volumetric capacitance of 377 F cm −3 and low charge transfer resistance of 5.9 Ω. Based on the facile operability of the proposed pre-activation strategy, it can be expected to be easily ported to other Li/K/Zn-storage, providing a novel avenue for the exploration of positive electrode materials with outstanding electrochemical behaviors. A novel ASSC was fabricated by matching α-MnO 2 //WO 3 electrodes, exhibiting wide voltage of 2.0 V, high energy/power density (0.965 W h cm −3 /65.2 W cm −3 ) and ultralong cycle life. This work proposes a simple strategy to develop high-performance positive materials and assemble ASSC with high energy/power density and long-term stable operation.