Superior Rate Mesoporous Carbon Sphere Array Composite via Intercalation and Conversion Coupling Mechanisms for Potassium-Ion Capacitors

Carbonaceous materials have been usually adopted as the anode for high energy density potassium-ion hybrid capacitors (KICs) owing to their low voltage plateau, high conductivity, and excellent electrochemical compatibility. The improvements of their specific capacity and sluggish intercalation mechanism are still challenges to further boost the energy density of KICs while maintaining high power density and long cycle life. Herein, a N-doped mesoporous carbon sphere array composite is developed by a dual-templates method. The N-doped carbon sphere array with interpenetrated macro- and meso-pores facilitates the fast electron transport and rapid K+ diffusion. The uniformly introduced Co3O4 nanoparticles (NPs) confined in the array enable a kinetically boosted conversion reaction for excess and fast K+ storage. The partially oxidized Co NPs can efficiently enhance the conductivity of the entire composite. By introducing this optimized conversion capacity from encapsulated Co3O4 NPs, the composite with intercalation and conversion coupling mechanisms displays superior capacity and cycle life. The assembled KICs exhibit high energy/power densities (148 Wh kg(-1)/124 W kg(-1)) and great cycling performance (94% after 5000 cycles, 0.5 A g(-1)). This promising strategy demonstrates an example for carbonaceous composite anode with synergistic K+ storage hybrid mechanism toward high performance KICs.