Enhanced ion diffusion induced by structural transition of Li-modified borophosphene

Density functional theory (DFT) calculations have been carried out to investigate the performance of borophosphene in lithium-ion batteries. Our study has revealed the following: (1) the Dirac cone in the electronic structure demonstrates the metallic nature of borophosphene, implying the enhanced electronic conductivity of the anode electrodes; (2) borophosphene shows high adsorption of Li ions with binding energies in the range of -0.6 to -1.1 eV; (3) the theoretical storage capacity is significantly high, up to 1282.7 mA h g-1, and more interestingly, a structural transition is observed in the host borophosphene at a high density of Li ions; (4) at low concentrations, graphene-like borophosphene shows isotropic diffusion of Li atoms with a barrier around 0.5 eV, while at high density, the phosphorene-like borophosphene exhibits a reduced barrier in the range of 0.12-0.14 eV along the zigzag direction, suggesting strong promotion of Li-ion transportation; (5) meanwhile, owing to the structural transition, phosphorene-like borophosphene exhibits highly anisotropic migration of Li ions along the zigzag and armchair directions. These new findings present the great advantages of borophosphene as an anode material in lithium-ion batteries.