General synthesis of yolk-shelled Fe Q @Carbon (Q = S, Se, P) film for high performance anode of sodium-ion batteries

Sodium-ion batteries (SIBs) have attracted widespread attention because of the economic benefit of low-cost and abundance of sodium resources. Iron-based electrodes (sulfide, selenide and phosphide) that operate through conversion mechanism have shown huge potential for excellent sodium-ion storage. However, the problems related with serious volume expansion and lack of general synthesis methods of iron-based materials shorten the cycle life and hindered their application in SIBs. Herein, a general synthetic strategy of electrospinning process was developed to achieve the yolk-shelled FexQy@C (Q = S, Se and P) film for binder-free anode of high-performance SIBs. Such method has more precursor materials to choose from and is highly scalable. More importantly, the designed electrodes have a unique yolk-shell structure and a three-dimensional conductive network. When applied as a binder-free anode of SIBs, all three samples exhibit outstanding sodium storage performance (FeS2@C-40: remaining 280 mAh g−1 after 400 cycles at 1 A g−1, Fe7Se8@C-40: remaining 186.5 mAh g−1 after 200 cycles at 0.1 A g−1 and FeP4@C-40: remaining 205 mAh g−1 after 1000 cycles at 0.5 A g−1). Therefore, the scalability and universality of this general synthetic strategy can open up a new direction for the exploration of high-energy density and flexible electrode materials.