Interfacial Design on Graphene-Hematite Heterostructures for Enhancing Adsorption and Diffusion towards Superior Lithium Storage.

Hematite (α-FeO) is a promising electrode material for cost-effective lithium-ion batteries (LIBs), and the coupling with graphene to form Gr/α-FeO heterostructures can make full use of the merits of each individual component, thus promoting the lithium storage properties. However, the influences of the termination of α-FeO on the interfacial structure and electrochemical performance have rarely studied. In this work, three typical Gr/α-FeO interfacial systems, namely, single Fe-terminated (Fe-O-Fe-R), double Fe-terminated (Fe-Fe-O-R), and O-terminated (O-Fe-Fe-R) structures, were fully investigated through first-principle calculation. The results demonstrated that the Gr/Fe-O-Fe-R system possessed good structural stability, high adsorption ability, low volume expansion, as well as a minor diffusion barrier along the interface. Meanwhile, investigations on active heteroatoms (e.g., B, N, O, S, and P) used to modify Gr were further conducted to critically analyze interfacial structure and Li storage behavior. It was demonstrated that structural stability and interfacial capability were promoted. Furthermore, N-doped Gr/Fe-O-Fe-R changed the diffusion pathway and made it easy to achieve free diffusion for the Li atom and to shorten the diffusion pathway.