Ultrafine design of carbon whisker array @ hollow carbon sphere anode for superior K-storage

Even though bottom-up strategy has been successfully developed to construct nanocarbon materials from molecule blocks for energy storage applications, elaborate structure manipulation via a facile and scalable method remains a big challenge. Herein, a facile free-radical C–C coupling-based bottom-up strategy was proposed to controllably construct carbon whisker array @ hollow carbon sphere (CWA@HCS) anode from the molecule block of hexabromobenzene (HBB) for superior K-storage. The novel CWA@HCS anode was easily achieved via the controllable catalysis of C–C coupling reaction on the surface of commercial metallic Cu particles. The optimized CWA@HCS anode delivered a high reversible K-storage capacity of 367.6 mAh/g at 50 mA/g, excellent rate capability (155.5 mAh/g at 1000 mA/g), and excellent long-term cycle performance (182.5 mAh/g maintained after 700 cycles at 500 mA/g). In addition, the full cell assembled from CWA@HCS electrode showed excellent cycle performance and rate performance. These excellent K-storage properties should be attributed to the surface capacitive-dominated K-storage mechanism guaranteed by the three-dimensional (3D) array structure. This study provides a basic reference for the design of advanced nanocarbon materials as well as anode materials for potassium ion batteries.