  Most recent exciting experimental advances introduced buckled and flat
borophene nanomembranes as new members to the advancing family of
two-dimensional (2D) materials. Borophene, is the boron atom analogue of
graphene with interesting properties suitable for a wide variety of
applications. In this investigation, we conducted extensive first-principles
density functional theory simulations to explore the application of four
different flat borophene films as anode materials for Al, Mg, Na or Li-ion
batteries. In our modelling, first the strongest binding sites were predicted
and next we gradually increased the adatoms coverage until the maximum capacity
was reached. Bader charge analysis was employed to evaluate the charge transfer
between the adatoms and the borophene films. Nudged elastic band method was
also utilized to probe the ions diffusions. We calculated the average atom
adsorption energies and open-circuit voltage profiles as a function of adatoms
coverage. Our findings propose the flat borophene films as electrically
conductive and thermally stable anode materials with ultra high capacities of
2480 mAh/g, 1640 mAh/g and 2040 mAh/g for Mg, Na or Li-ion batteries,
respectively, which distinctly outperform not only the buckled borophene but
also all other 2D materials. Our study may provide useful viewpoint with
respect to the possible application of flat borophene films for the design of
high capacity and light weight advanced rechargeable ion batteries.
