Redox-active engineered holey reduced graphene oxide films for K+ storage

Abstract

Abstract Graphene film is promising candidate as free-standing electrodes for potassium-ion batteries (KIBs) owing to its intrinsic nature of mechanical strength and high electrical conductivity. However, its performance is usually restricted by the tightly stacked structure and sluggish insertion/deinsertion K storage mechanism. Herein, a redox-active engineered holey reduced graphene oxide (HRGO) film anode was prepared by using the carboxylic acid functionalized polystyrene (PS-COOH) spheres as the template. The holey ion diffusion network channels and the oxygen functional groups can be optimized during the PS-COOH spheres decomposition process, which largely promote the enhancement of electrochemical performance because the oxygen functional groups can serve as the surface-redox sites increasing surface-driven reactions and holey channels provide more ion-accessible area for K-ion storage. Moreover, the reduction degree of graphene oxide also be simply tuned by changing the annealing temperature, which can improve the K+ bulk intercalation reaction. As a result, the optimized HRGO-900 (HRGO sample obtained at 900 °C) films exhibits a superior areal capacity (0.80 mAh cm-2 at 0.1 mA cm-2). The electrode design and construction strategies can be effectively applied in other 2D materials, which exhibits practical applications in energy storage devices.