First-principles study on h-BSi sheet as a promising high-performance anode for sodium-ion batteries.

Seeking cheap, efficient and sustainable alternatives to lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) has emerged as a realm of research, due to the abundance of Na in the earth's crust. We have investigated the relative performance of novel intrinsically metallic h-BSi (BS) sheet as an anode for SIBs, compared to LIBs, through Density Functional Theory studies. Our calculations show that BS has higher chemisorption interactions with Na than Li atoms while drawing substantial electron densities from both, turning them into cations. BS is able to reach a high specific capacity of 1127.62 mA h g for Na, while only as half of that for Li, at ambient temperatures ranging 300-600 K. The moderate sodiation (0.77 V) and lithiation (0.79 V) voltages facilitate BS to prevent the SEI layer formation, metal plating and harmful dendrite growth and to maintain good energy density. BS retains good electronic and ionic conductivities after hosting both Na and Li adatoms, while the former diffuses with about as half the barriers as those of the latter, supporting faster charge/discharge rate and greater preservation of storage capacities in high current densities when BS is used as an anode in SIBs. Na adsorptions cause relatively lower structural deformations to BS, and refrain from forming clusters, leading to good cyclic stability. The superior electrochemical performance of Na, thus, makes BS a potential anode material for SIBs.