A DFT prediction of two-dimensional MB (M = V, Nb, and Ta) monolayers as excellent anode materials for lithium-ion batteries

Transition metal borides (MBenes) have recently drawn great attention due to their excellent electrochemical performance as anode materials for lithium-ion batteries (LIBs). Using the structural search code and first-principles calculations, we identify a group of the MB 3 monolayers (M = V, Nb and Ta) consisting of multiple MB 4 units interpenetrating with each other. The MB 3 monolayers with non-chemically active surfaces are stable and have metal-like conduction. As the anode materials for Li-ion storage, the low diffusion barrier, high theoretical capacity, and suitable average open circuit voltage indicate that the MB 3 monolayers have excellent electrochemical performance, due to the B 3 chain exposed on the surface improving the Li atoms' direct adsorption. In addition, the adsorbed Li-ions are in an ordered hierarchical arrangement and the substrate structure remains intact at room temperature, which ensures excellent cycling performance. This work provides a novel idea for designing high-performance anode materials for LIBs. The boron-exposed MB 3 monolayers (M = V, Nb and Ta) formed by interpenetrating MB 4 units have high Li-ion capacities.