Huge Lithium Storage in 2D Bilayer Structures with Point Defects

Current Li-ion batteries have a low energy density mainly because of the low Li intercalation level in graphite anodes. The high-density packing of lithium atoms in electrode materials amplifies the storage capacity and efficiency of energy storage devices. The use of two-dimensional (2D) bilayer structures offers an immediate advantage of high-density lithium storage compared to conventional graphite electrodes. However, the lithium storage in 2D homostructures and heterostructures is still limited. In the present theoretical study, we have modified 2D bilayer structures by creating controlled point defects. Using ab initio calculations, we show that the 2D bilayer structures of boron nitride-boron nitride (BN-BN), graphene-boron nitride (G-BN), and graphene-graphene (G-G) with a point defect in each structure are more stable and can store up to 11 times more Li atoms. On increasing the defect density, the stability of the G-BN structure increases but the lithium storage capacity does not increase. Except for the first Li atom, the intercalation of extra Li atoms does not cause volume changes of the defective 2D bilayer structures. Defective 2D bilayer structures might be a high-energy-density anode material.