Dual-carbon coupled three-dimensional superstructures with dominant mesopores targeting fast potassium-ion storage

Abstract

Carbon materials with three-dimensional (3D) superstructure are a promising anode for potassium-ion batteries (PIBs) because of its rich micropores and defects. However, plenty of micropores often need more time to make electrolyte fully infiltrate, and their irreversible trapping effect will inevitably cause the loss of active K-ions upon cycling. Besides, excessive defects easily arouse poor conductivity because the absence of continuous graphite domains. Hence, dual-carbon coupled 3D superstructure is constructed by pyrolyzing the mixture of zeolitic imidazolate framework and polyvinylpyrrolidone (ZIF8@PVP). Since the preferential decomposition of external PVP, the micropores in ZIF8-derived carbon are effectively inhibited while keeping considerable mesopores, thus substantially shortening ions diffusion distance. Moreover, the decomposition and shrinkage of ZIF8 particles in return prompt the PVP-derived carbon to create more defects, which favors the adsorption storage of K-ions. Not only that, the metallic Zn can catalyze the formation of continuous graphite domains, endowing fast electron migration rate. Accordingly, the optimized product not only delivers an excellent rate (188.2 mAh g−1 at 2 A g−1) and cyclability (over 1800 cycles) in K-half cells, but presents a high energy density (181.5 Wh kg−1) in potassium-ion hybrid capacitors.