First-Principle Study of a ZnS/Graphene Heterostructure as a Promising Anode Material for Lithium-Ion Batteries

Properties of ZnS/graphene, such as formation energy of the Li adatom, activation energy for Li diffusion, pseudocapacity-like storage, and density of state (DOS), render ZnS/graphene a suitable anode material for a rechargeable lithium-ion battery. Lithium storage sites, migration paths, electronic conductivity, and storage sequence of lithium ions are clarified. Lithium ions preferentially embed the ZnS/graphene heterostructure interface and the surface of ZnS and then intercalate into the bulk phase of ZnS. In the ZnS bulk, Li ions diffuse by the T–O–T path, and the activation energy diseases with volume expanded. LiS₄ and ZnS₂ are produced with ZnS lithiation, besides Li_xZn and Li₂S. Moreover, it is proven that the capacity of ZnS/graphene more than the sum of ZnS and graphene originates from the interfacial lithium storage via the pseudocapacity-like storage mechanism. Therefore, further increasing the contact area between ZnS and graphene could promote the capacity by reducing the ZnS particle size.