Metallic 3D porous borophosphene: A high rate-capacity and ultra-stable anode material for alkali metal ion batteries

Abstract

2D borophosphene (B2P2) is a promising next-generation metal ion battery (MIB) anode material, because of the high capacity and low open-circuit-voltage (OCV). Nevertheless, its electrochemical kinetics and cyclability are severely impeded by poor hopping dynamics, small pore size and low mechanical stiffness. In this work, using first principles computations, we design a novel porous 3D boron-based material (named 3D-B2P2) using the corresponding 2D borophosphene nanosheet as a building block. Our computational results show that the resulting 3D-B2P2 has highly dynamical, thermal and mechanical stability. Different from the semi-metallic borophosphene, 3D-B2P2 exhibits intrinsically high metallicity and low mass density (1.20 g/cm3). Its maximum Young's modulus (227.97 GPa) far exceeds that of borophosphere (145.53 GPa), showing a moderate mechanical stiffness. More importantly, due to the uniformly distributed pores and strong affinity towards metal ions, 3D-B2P2 anode achieves high reversible capacities of 691.30, 904.00 and 691.30 mA h/g, suitable OCVs of 1.00, 0.56 and 0.59 V, small volume changes of 2.25%, 6.00% and 8.11%, and low diffusion barriers of 0.25, 0.10 and 0.04 eV for lithium/sodium/potassium ion batteries. All the results indicate that 3D-B2P2 is an appealing anode material for advanced MIBs.