Applied Surface Science, Vol.441, 356-363, 2018
How to boost the sluggish lithium-ion hopping dynamic in borophene?
In light of low atomic mass, three types of experimentally synthetized borophene including beta(12), chi(3) and striped t-sheet have been predicted to be promising anode materials for lithium-ion batteries (LIBs) with extremely high capacity. However, the rate performances of beta(12) and chi(3) are quite poor with high diffusion barrier of 0.66-0.81 eV on beta(12) and 0.60-0.85 eV on chi(3) in contrast with that in t -sheet (typically <0.1 eV). Isolation oft-sheet from their blend remains a fundamental challenge in the field of nanotechnology and a mechanistic understanding and control over the hopping dynamic of Li' therein are thus of extremely important to facilitate the development of borophene-based anode material, but still lacking. In this work, we performed a comprehensive theoretical investigation on the adsorptions and migrations of Li+ on perfect and defective beta(12) and chi(3) based on density functional theory. We determined a new kind of vacancy in beta(12) that modulates the adsorption and boosts the diffusion of Li+ nearby remarkably. With the aid of charge doping, we uncover a general mechanism (charge-concentration mechanism) involved with the celebrated bonding theory of borophene, where the hopping barrier of Li+ on beta(12) could be reduced to be 0.06 eV, rationalizing the boosting Li+ hopping as a result of electron deficiency in vacant borophene. By extending our calculations to H functionalized borophene and Ag supported borophene, we further confirm the validity of the "charge-concentration mechanism" under more realistic experimental conditions. The proposed mechanism could be used as a guiding principle to improve or develop new borophene-based electrode materials with high rate performance for LIBs. (C) 2018 Elsevier B.V. All rights reserved.