Fe2P nanoparticles-doped carbon nanofibers with enhanced electrons transfer capability as a self-supporting anode for potassium-ion battery

Carbonaceous materials with various structures and morphologies have been widely investigated as anode for potassium-ion batteries (PIBs), owing to their low cost, non-toxicity, environmental-benignity, etc. Among them, carbon nanofibers (CNFs) synthesized by electrospinning technique usually exhibit higher flexibility, thus they can be directly used as a self-supporting electrode. Accordingly, the overall electrochemical performance is obviously improved, and the batteries assembly procedure is also greatly simplified. However, intrinsic electronic conductivity of CNFs cannot sufficiently meet fast charging/discharging requirements at high current densities. Herein, iron phosphide nanoparticles-doped CNFs (Fe 2 P-CNFs) are well fabricated by electrospinning, phosphorylation, and carbonization route. The resulting Fe 2 P-CNFs, their internal Fe 2 P nanoparticles with high electronic conductivity (3.3 × 10 −1 S cm −1 , Fe 2 P single crystal) can accelerate electrons transfer, and simultaneously create numerous defects for K-ions storage. Besides, amorphous features of CNFs can provide adequate sites/voids to accommodate more K-ions. Based on this, when Fe 2 P-CNFs are used as a self-supporting anode for PIBs, they deliver excellent reversible capacity (379.2 mAh g   −   1 ), high-rate capability, and ultra-long cycle lifespan (179.6 mAh g   −   1 over 2000 cycles at 2000 mA g   −   1 ). Therefore, this work demonstrates the unique merits of Fe 2 P doping for improving conductivity, which may help exploit other carbon materials with high performance.