N-doped hollow carbon nanofibers anchored hierarchical FeP nanosheets as high-performance anode for potassium-ion batteries

Abstract

Potassium-ion batteries (PIBs) are emerging as appealing technologies for energy storage applications due to the highly abundant potassium resource in nature and low cost of potassium. Iron phosphide (FeP) have been widely investigated as anode materials for PIBs, owing to its high theoretical specific capacity and the plentiful of its primitive materials (P and Fe). However, the practical application of FeP materials in PIBs suffers from serious capacity fading due to the large volume expansion caused by the intercalation/deintercalation of potassium ions. Here, hierarchical FeP nanosheets internally wired by N-doped hollow carbon nanofibers (N–CNF@FeP) is rationally designed and synthesized via a combination of hydrothermal route and phosphidation treatment. In such a unique nanoarchitecture, hierarchical FeP nanosheets are homogeneously anchored on the hollow carbon nanofibers with nitrogen-rich and porous properties. This unique designed structure not only improve the electronic conductivity and structural stability of the hybrid composite but also facilitates the transport of electrons and K-ions. When applied as potassium ion battery, N–CNF@FeP composite manifests remarkably reversible capacities, ultra-long cycle life, as well as superior rate performances for potassium storage process. Moreover, at a current density of 0.1 A g−1, N–CNF@FeP composite delivers a high capacity of 210 mAh g−1 after 1000 cycles.