Multi-heteroatom-doped dual carbon-confined Fe3O4 nanospheres as high-capacity and long-life anode materials for lithium/sodium ion batteries

The lithium/sodium-ion storage properties of transition metal oxides often undergo startling volume variation and poor electrical conductivity. Herein, N, P and S doped dual carbon-confined Fe3O4 nanospheres (Fe3O4@C@G) are prepared by the multi-heteroatom-doped dual carbon-confined strategy. The first carbon layer results from multi-heteroatom-containing polymer derived N, P and S doped carbon to form Fe3O4@doped carbon core-shell nanostructure. And the second carbon layer results from the further encapsulated reduced graphene oxide (rGO) to form Fe3O4@doped carbon@graphene 3D architecture (Fe3O4@C@G). As expected, the resulting Fe3O4@C@G can be served as the universal anode materials towards lithium/sodium-ion batteries (LIBs/SIBs). Interestingly, Fe3O4@C@G delivers higher reversible capacity of 919 mAh g-1 at 0.1 A g-1 for LIBs. As for SIBs, Fe3O4@C@G also shows a high reversible capacity of 180 mAh g-1 after 600 cycles at 0.1 A g-1. Furthermore, the electrochemical reaction kinetics in LIBs/SIBs are investigated and Li+ full cells are also assembled to demonstrate its practical application.