Two-Dimensional Penta-BN2 with High Specific Capacity for Li-Ion Batteries.

Searching for high-performance electrode materials is one of the most effective ways to improve the energy density of current lithium-ion batteries. Using first-principles calculations, we reveal that pentagonal BN2 (Penta-BN2) can serve as a compelling anode material for lithium-ion batteries. Penta-BN2 harbors intrinsic metallic nature before and after lithiation, showing excellent electrical conductivity. Significantly, the fully lithiated phase of Penta-BN2 is Li3BN2, corresponding to an ultra-high theoretical capacity of 2071 mAh g-1, superior to the capacity of most of the previously reported two-dimensional candidates. Meanwhile, the open-circuit voltage and diffusion barrier height of Penta-BN2 are found to be fascinatingly low. Moreover, in light of its small Young's modulus and robust lattice toward lithiation, Penta-BN2 can accommodate volume changes during the charging-discharging processes, remarkably beneficial for fabricating flexible electrodes.