Ultrafast and durable Li/Na storage by an iron selenide anode using an elastic hierarchical structure

In this work, FeSe nanoparticles were encapsulated into a polycystic carbon matrix (FeSe/C) followed by graphene coating (GF@FeSe/C) via a facile strategy, resulting in a hierarchical framework with porous and elastic characteristics. This unique structure could release the ruinous stress induced by dramatic volume change and guarantee structural integrity during cycling. Furthermore, ultrafine FeSe particles and the conductive network carbon matrix ensured rapid electron/ion transfer capability and considerable surface active sites, facilitating fast charging/discharging reactions. Therefore, GF@FeSe/C demonstrated outstanding rate performance and cycling stability that 241 mA h g−1 was obtained under 30 A g−1, and 356 mA h g−1 remained over 600 cycles at 5 A g−1 (for Li-storage). Meanwhile, a rate capacity of 217 mA h g−1 was delivered at 10 A g−1, and the capacity retention was almost 100% during 900 cycles at 1 A g−1 (for Na-storage).