B₅N₃ as a potential high-capacity electrode material for calcium ion batteries

Calcium ion batteries (CIBs) are considered as promising candidates for the next-generation large-scale energy storage technologies, due to the abundant resources and bivalent properties of calcium. Herein, based on first principles calculations, we systematically explore the performance of B₅N₃ as an electrode material for chargeable CIBs. Specifically, the adsorption of the Ca atom effectively reduces the band gap of B₅N₃, leading to good electrical conductivity. Additionally, the B₅N₃ monolayer can achieve an effective double-layered adsorption of Ca atoms on both sides of the monolayer surface, thus exhibiting an ultra-high theoretical capacity of 4463 mA h g^-1 (Ca) compared with the capacities of Na (2231 mA h g^-1), Li (1116 mA h g^-1) and K (558 mA h g^-1). The high capacity is attributed to the multiple empty electron orbitals of the constituent elements of B₅N₃ and low distance mismatch which can exhibit excellent adsorption properties for multivalent atoms. Furthermore, the low diffusion energy barriers and satisfactory thermal stability ensure the reliability of B₅N₃ as a CIB electrode material. Our work not only develops an excellent candidate for the electrode materials of CIBs, but may also inspire the rational design and synthesis of electrode materials towards high-performance CIBs.