Hollow N-doped carbon nanofibers provide superior potassium-storage performance.

Potassium-ion batteries (PIBs) are attractive as an alternative to lithium-ion batteries in emerging energy storage devices. However, a big challenge is to design advanced anode materials with fast charge/discharge and extended lifespan. Herein, a series of hollow N-doped carbon nanofibers (HNCNFs) were derived from polyaniline. As an anode for PIBs, HNCNFs exhibit an ultra-high rate capability of 139.7 mA h g -1 at 30 A g -1 and an ultra-long cycling life of 188.4 mA h g -1 at 1 A g -1 after 4000 cycles. These prominent performances can be ascribed to: (i) the enlarged interlayer spacing, which accommodates more K + and larger (de)potassiation strain without fracture; (ii) the interconnected hollow nanofibers, which shorten ion diffusion distance and provide enough space to buffer volume change and sufficient electrolyte diffusion paths to ensure enhanced reaction efficiency of active materials; and (iii) high-content pyridinic/pyrrolic N-doping, which improves electrical conductivity, creates more active sites and enhances surface pseudocapacitive behavior, benefiting rapid K + diffusion. This study provides a facile and cost-effective strategy to fabricate high-performance PIB anode materials on a large scale.