Structural prediction and multilayer Li+ storage in two-dimensional VC2 carbide studied by first-principles calculations

Abstract

VC₂, a new two-dimensional transition metal carbide containing C₂ dimers, was predicted by the swarm-intelligent global-structure search method. The structural properties and Li⁺ storage ability of VC₂ monolayers and stacked VC₂ multilayers were systematically investigated by first-principles calculations, and the high structural stability and electronic conductivity of the materials suggested promising Li⁺ storage properties. VC₂ monolayers showed a theoretical capacity of 1073 mA h g⁻¹ based on multilayer Li⁺ adsorption, while stacked VC₂ showed an even larger theoretical capacity of 1430 mA h g⁻¹. Intercalated Li⁺ formed ordered arrangements between VC₂ layers, retaining a well-ordered layered structure. Li⁺ near the VC₂ layer formed ionic bonds with the host material, while Li in middle layers formed metallic Li–Li bonds. All Li⁺ was stored in the interlayer space with low diffusion barriers, which demonstrated high rate capability of the material for lithium ion batteries. Remarkably, the predicted VC₂ carbide achieved more than 1000 mA h g⁻¹ capacity irrespective of being in monolayer or stacked layer structures, which rendered them very convenient for practical material preparation and battery applications.