Flexible borophosphene monolayer: A potential Dirac anode for high-performance non-lithium ion batteries

Highlights: • B₂P₂ possesses semimetal nature, moderate Young's modulus and excellent mechanical flexibility. • B₂P₂ exhibits low ion diffusion barriers and open circuit voltage. • The theoretical capacities of B₂P₂ in Na, K and Ca-ion batteries are 1282.34, 854.89, 1282.34 mA h/g, respectively. • B₂P₂ is a promising Dirac anode to achieve high-performance Na, K and Ca-ion batteries. Non-lithium ion batteries (NLIBs) have received great interest in the next generation renewable energy storage due to their intrinsic safety and low cost; nonetheless, searching for a high-performance anode still remains a great challenge. Herein, using first principles calculations, we have evaluated the feasibility of recently developed borophosphene (B₂P₂) as a Dirac anode of NLIBs. Our results demonstrate that Na, K, Ca could form stable adsorption on the B₂P₂ along with the adsorption energy of −1.27 – −0.36 eV. The B₂P₂ exhibits a semimetal characteristic, ensuing excellent conductivity for the rapid electron transport. Moreover, diffusion barriers of Na, K and Ca are 0.10, 0.07 and 0.33 eV, respectively, indicative of high ion mobility. The specific capacities in Na, K and Ca-ion batteries are up to 1282.34, 854.89 and 1282.34 mA h/g, which are significantly larger than that of commercial electrode. Furthermore, B₂P₂ could withstand large ultimate strain (>16%) and shows a good mechanical flexibility, which are of great benefit to accommodate its volumetric expansion and contraction during cycling. Given its high electrical conductivity, large adsorption energy, high specific capacity, fast ion diffusion and excellent mechanical property, B₂P₂ is a potential anode to achieve advanced Na, K and Ca-ion batteries.