Highly nitrogen doped carbon nanofibers with superior rate capability and cyclability for potassium ion batteries

Potassium-ion batteries are a promising alternative to lithium-ion batteries. However, it is challenging to achieve fast charging/discharging and long cycle life with the current electrode materials because of the sluggish potassiation kinetics. Here we report a soft carbon anode, namely highly nitrogen-doped carbon nanofibers, with superior rate capability and cyclability. The anode delivers reversible capacities of 248 mAh g(-1) at 25 mA g(-1) and 101 mAh g(-1) at 20 A g(-1), and retains 146 mAh g(-1) at 2 A g(-1) after 4000 cycles. Surface-dominated K-storage is verified by quantitative kinetics analysis and theoretical investigation. A full cell coupling the anode and Prussian blue cathode delivers a reversible capacity of 195 mAh g(-1) at 0.2 A g(-1). Considering the cost-effectiveness and material sustainability, our work may shed some light on searching for K-storage materials with high performance.