Unlocking colossal storage capacity and energy density of two-dimensional biphenylene oxide for Li-, Na-, and K-ion batteries

Abstract Carbon-based two-dimensional (2D) materials are promising as anode materials in metal-ion batteries due to their large surface area, low cost, and high stability. Using the first-principles calculations, we propose novel 2D biphenylene oxide as an excellent anode material for metal-ion batteries with the maximum storage capacity among 2D materials. Our calculations show that biphenylene oxide, analogous to graphene oxide, is thermodynamically, mechanically, and dynamically stable. The adsorption of an oxygen atom on the biphenylene sheet induces a metal-to-semiconductor transition. The biphenylene oxide (BO-C 6 O) exhibits an indirect band gap of 1.14 eV (1.83 eV) using PBE (HSE06) functional. The biphenylene oxide holds more metal atoms than pristine biphenylene. Our findings reveal high storage capacities of 1826 mAh/g (Li), 1065 mAh/g (Na), and 913 mAh/g (K), along with energy densities of 4218 mWh/g (Li), 1991 mWh/g (Na), and 1570 mWh/g (K), significantly higher than graphene oxide and other 2D materials. Additionally, the biphenylene oxide has low metal diffusion barriers of 0.19 eV (Li), 0.34 eV (Na), and 0.07 eV (K) and moderate open-circuit voltages of 0.73 V (Li), 0.84 V (Na), and 1.21 V (K). Minimal volume change of 0.93% occurs in the case of Li and a moderate volume change of 3.74% in the case Na, which further reflect the excellent cyclic stability of biphenylene oxide. These findings confirm the superiority of biphenylene oxide as an anode material among the 2D material family. Our study offers valuable insights for experimentalists to synthesize and hold great potential in metal-ion battery applications.