Metal-ion battery anode based on boron nanotubes: DFT calculations

In this work, an ab initio study of a triangulated boron nanotube as an anode material for lithium-ion and sodium-ion batteries was performed for the first time. In the work, two boron nanotubes of “armchair” type (21, 0) and “zigzag” type (14, 0) were considered. The parameters such as Li / Na adsorption energy, electrical conductivity, specific capacitance, diffusion barriers and open-circuit voltage in a boron nanotube were calculated for varying Li / Na concentration upon three charge / discharge cycles. The study revealed that: a) Li / Na atoms are strongly bonded to the atomic structure of boron nanotube and their adsorption energy does not exceed the cohesive energy for bulk Li / Na; b) the energy barrier for Li / Na diffusion in the boron nanotube is 26.2 meV for Li and 17.0 meV for Na; c) the specific capacitance of a boron nanotube is 619.8 mAhg−1 at an average open circuit voltage of 0.70 V (relative to Li / Li+) and 0.66 V (relative to Na / Na+); d) calculation of electrical conductivity showed an increase in the resistance of the boron nanotube after three charge / discharge cycles up to 931 Ohm for Li and 632 Ohm for Na; e) after three charge / discharge cycles, the total energy of the boron nanotube reduced by 273 meV (Li) and 364 meV (Na) indicating an improvement in the equilibrium state after cycling. Analysis of the results confirms that triangulated boron nanotube is a very promising anode material for lithium-ion and sodium-ion batteries.