Two-dimensional Si3C enables high specific capacity as promising novel anode material for Li/Na/K-ion batteries
Previous combined theoretical and simulation analyses show that the anode material with similar electronic structure of graphene but with larger lattice parameters usually shows higher theoretical specific capacity for Li/Na/K-ion batteries. Now therefore, a density functional theory (DFT) calculation is applied to evaluate the working performances of two-dimensional Si3C monolayer, which has larger bond lengths than graphene, as the anode material of Li/Na/K-ion batteries. The negative adsorption energies of Li/Na/K atoms on the surface of Si3C monolayer avoid the appearance of dendrite. With the intercalation of Li/Na/K atoms, the Si3C monolayer exhibits a puckered structure instead of its initial planar structure, which contributes to further lowering the diffusion energy barrier of Li/Na/K atoms. The theoretical specific capacities for Li, Na and K-ion batteries are estimated to be as high as 1394, 1115 and 836 mAh g-1, corresponding to the stoichiometry of Li5Si3C, Na4Si3C and K3Si3C, respectively. The average open circuit voltages (OCV) for the Li/Na/K-ion batteries are 0.58 V, 0.50 V and 0.71 V, respectively. The density of states (DOS) calculation shows that the Si3C monolayer is semimetallic and the electronic conductivity is further enhanced with the intercalation of alkali metal atoms. The maximum variation of lattice parameters of Si3C monolayer during the whole atom intercalation process is only 3.54% and the structural integrity is well preserved. All the desirable properties manifest that the Si3C monolayer is a promising anode material for Li/Na/K-ion batteries. It also suggests that the silicene doped by moderate carbon or some other elements is a potential anode material for alkali metal-based batteries.