Nitrogen and Phosphorus Dual-Doped Graphene Aerogel Confined Monodisperse Iron Phosphide Nanodots as an Ultrafast and Long-Term Cycling Anode Material for Sodium-Ion Batteries

Transition metal phosphides have recently gained much interest as anodes for sodium-ion batteries (SIBs). However, their intrinsic volume change during Na ion uptake/release leads to poor cycling stability and limited rate performance. To solve this problem, a unique hybrid architecture of iron phosphide nanodots bound on 3D phosphorus-doped graphitic nitrogen-rich graphene (FeP/NPG) is obtained from the phosphidation of NH2-rich reduced graphene oxide (rGO) decorated Fe2O3. Mono-dispersed FeP nanodots integrating with 3D NPG networks and high content of graphitic N not only induce fast Na ion/electron transfer kinetic and excellent structural stability during long-term cycling, but also they enhance the capacitive contribution. These features of FeP/NPG result in high-performance sodium storage. A high reversible capacity of 613 mAh g(-1) is achieved at 50 mA g(-1). Also, an excellent rate capability of 422 and 349 mAh g(-1) is observed at 1 and 3 A g(-1), respectively. More importantly, an ultrastable capacity of 378 mAh g(-1) at 1 A g(-1) can be obtained upon long-term cycling. It shall be possible to extend this strategy for fabricating other transition metal phosphide based anodes for advanced SIBs.