Red phosphorus nanoparticles embedded in porous N-doped carbon nanofibers as high-performance anode for sodium-ion batteries

In this paper, red phosphorus nanoparticles (~ 97.7 nm, 51 wt% content) homogeneously embedded in porous nitrogen-doped carbon nanofibers (denoted as P@C) are prepared using a feasible electrospinning technique for the first time. Meanwhile, red P@C with the character of free-standing membrane is directly used as binder- and current collector-free anode for sodium-ion batteries, exhibiting a highly reversible three-electron transfer reaction (3Na+ + P + 3e- ↔ Na3P) with excellent rate capability (1308 mA h g-1 at 200 mA g-1 in comparison of 343 mA h g-1 at 10,000 mA g-1) and remarkable cyclic stability (~ 81% capacity retention after 1000 cycles). Furthermore, a soft package Na-ion full battery with red P@C anode and Na3V2(PO4)2F3/C cathode is assembled, displaying a high operation voltage of ~ 3.65 V and an outstanding energy density of 161.8 W h kg-1 for the whole battery. This is owing to the distinctive structure of very small amorphous phosphorus nanoparticles uniformly confined in porous N-doped carbon nanofibers, which can effectively facilitate the electronic/ionic transportation and retard the active materials pulverization/fracture caused by volume fluctuation upon prolonged cycling. The simple and scalable synthesis route as well as the promising electrochemical performance shed new insights into the quest for high energy and long life phosphorus-based Na-storage anode materials.