Electrospinned free-standing FeP@NPC film for flexible sodium ion batteries with remarkable cycling stability

Abstract Flexible and wearable portable electronic devices have attracted increasing interest as a promising technology for the growing flexible electrochemical energy storage, which however require excellent mechanical property, fast electrochemical kinetics and good structural stability of the electrode. To-date the reports about flexible sodium ion batteries are still rare owing to the lack of proper electrodes. Herein, we report a new binder-free anode material of electrospinned free-standing FeP@NPC film with FeP nanoparticles wrapped in 3D interconnected N, P -codoped carbon fiber for high-performance sodium ion storage. The unique structure design offers various structural advantages: the growth of FeP nanoparticle is confined by the PAN nanofiber during the synthesis, and agglomeration of FeP is alleviated; the 3D connected carbon fiber network serves as electron/ion transport pathway to accelerate the reaction kinetics and meanwhile accommodates the volume expansion of FeP during the sodiation/disodiation process. A high reversible capacity of 557 mA h g-1 and remarkable cycling life of 1000 cycles are achieved. This research paves a novel strategy to construct the phosphides-based high-performance anode for the potential application in flexible energy storage devices.