Si[formula omitted]BN nanosheets as anchoring cathode material for realizing high capacity Al-ion battery

Abstract

Identifying a stable and high-capacity cathode material is crucial for the practical implementation of Aluminium-ion batteries (AIBs). Using first-principles calculations, we propose Si2BN as a suitable cathode material for AIBs. We show that sp2 hybrid Si2BN nanosheets with polar-covalent bonding nature favour the adsorption of a large number of AlCl4 clusters with significant charge transfer that results in a higher adsorption strength and stability compared to non-polar carbon cathodes. The estimated theoretical specific capacity (TSC) of Si2BN is 330 mAh/g, which is six times higher than that of graphite. Bilayer studies reveal that Si2BN shows surface adsorption of AlCl4 similar to that of the monolayer, but intercalation at low concentration of AlCl4 is unfavourable and it also shows that the binding strength of AlCl4 significantly improves when we first adsorb AlCl4 on the outer layers of Si2BN and then intercalate it between the layers. The nudged elastic band (NEB) study elucidates an easy diffusion of AlCl4 along the two-dimensional sheet with a barrier of 0.19−0.22 eV. Thermodynamical stability analysis implies the absence of more serious Cl2 gas evolution that makes Si2BN a durable cathode material. Hence, the proposed Si2BN has a great advantage over carbonaceous cathodes for designing high energy density and quick charge AIBs.