Theoretical studies of SiC van der Waals heterostructures as anodes of Li-ion batteries

Abstract

By using density functional theory (DFT), the potential of two dimensional SiC, SiC with Stone-Wales defect (SW-SiC) and their van der Waals heterostructures with graphene (SiC/graphene and SW-SiC/graphene) as anode materials have been investigated, including corresponding geometry structural changes, electronic structures, Li+ diffusion property and related electrochemical properties during charging. Comparing with SiC monolayer, SW-SiC possesses better electric conductivity as well as the Li adsorption properties. By introduction of graphene, SiC/graphene and SW-SiC/graphene heterostructures present excellent electronic conductivity, lower anode voltage and higher specific capacity for the introduction of build-in electric field. Their maximum theoretical capacity both could reach as high as 1229.91 mAh/g, three times more than that of graphite (370 mAh/g), along with a small change of interlayer spacing. The lithiation open-circuit voltage ranges of those heterostructures are also appropriate to be used as anode materials. Besides, the calculated diffusion barriers of Li ions in the interlayer of SiC/graphene and SW-SiC/graphene heterostructures are comparable to those of several graphene heterostructures and are lower than that for SW-SiC. This research illustrated that the deployment of heterojunction in electrode materials can greatly improve the electrochemical performance and endow experimental synthesis with new perspective.