Energy storage performance of Vn+1Cn monolayer as electrode material studied by first-principles calculations

Two-dimensional transition metal carbides are expected to be potential negative electrode materials, due to high conductivity, large cation storage capabilities, and unique mechanical properties. In this work, theoretical analysis of Li atom storage capacity and diffusion behavior of the Vn+1Cn monolayer are investigated. It is predicted that the V3C2 and V4C3 monolayers can be synthesized through selective etching of Al layers of the corresponding V3AlC2 and V4AlC3 phases. The Vn+1Cn monolayer is found to be of metallic character with a high total density of states at the Fermi level. Moreover, Vn+1Cn surfaces can be adsorbed by lithium with a low diffusion barrier and high storage capabilities compared with other carbon-based materials. To enhance performance, the surface functionalization should be avoided in the practical synthetic experiments. The above study results provide insight into the energy storage performance of the Vn+1Cn monolayer, and predict that the not yet synthesized V3C2 and V4C3 monolayers are promising candidates for electrode materials.