Borophene-Based Three-Dimensional Porous Structures as Anode Materials for Alkali Metal-Ion Batteries with Ultrahigh Capacity

The development of renewable and clean energy technologies requires the design of efficient materials for a wide variety of electrochemical applications. Using density functional theory, we design two metallic borophene-based three-dimensional (3D) porous structures (termed 3D-beta(12)-borophene and 3D-B7P2), which are found to be dynamically, thermally, and mechanically stable. The metallicity is dominated by the B p(x)-orbitals. The regularly distributed channels with low mass density and the intrinsic metallicity make 3D-beta(12)-borophene (3D-B7P2) promising for anode materials with ultrahigh capacities of 1653 (1363), 1239 (993), and 619 (681) mA h g(-1), low migration energy barriers of 0.55 (0.23), 0.25 (0.13), and 0.23(0.05) eV, small volume changes of 4.5 (6.3), 9.1 (6.9), and 7.4 (8.6)%, and appropriate average open-circuit voltages of 0.55 (0.52), 0.20 (0.31), and 0.27(0.24) V for Li-, Na-, and K-ions, respectively.