Lithium ion batteries (LIBs) are becoming alternative, high capacity, low cost, long cycle life, and rechargeable electrical power sources. These are now favorable for the applications of electric vehicles and automobiles according to the demand of modern era. Specially, the properties of LIBs are major concern for its use as anode material. The LIBs performance is improving day by day to cope the demand of energy storage. The commercially available graphite anode has low specific capacity, so, high specific containing new materials are necessary to take place of graphite. Now a days, two-dimensional (2D) materials are grabbing attention for anode material because of their high charge capacity, small volume expansion for good cyclability, large surface to volume ratio, low diffusion barrier, and unique electronic properties. It has been seen in the recent studies that alkali metal intercalation in layers from same materials (bilayer) or from different materials improves the potential application for rechargeable batteries. The intercalation of alkali metal in bi-layer or interface material is more favorable than the monolayer. Borophene is a famous group-III 2D material has been predicted with sixteen (16) different structures and proved as anode material for metal ion batteries. It has become attractive and alternative choice than graphite due to its low price, light weight, buckled structure, it preserve its metallic character after Li adsorption, large adsorption energy (-1.12), high theoretical capacity (1860 mAh g-1), moderate energy barrier (2.6 m eV). The stability of borophene was improved by making its interface with boron nitride. This interface improves the adsorption energy (-2.46) and open circuit voltage (1.04 V) than monolayer borophene and have higher charging capacity (1698 mA h g-1) than commercially available graphite anode. Different bi-layer structures of materials have already been reported for examining their potential application as anode materials. According to literature borophene appeared as emerging candidate for metal ion batteries and intercalation of Li in bi-layer borophene is still unknown.We adsorb lithium in most favorable site inside bilayer buckled borophene which is hollow site. We adsorb 12 lithium atoms as shown:
To calculate the adsorption energy we use the following formula:
My study shows that bilayer b-borophene has high capacity and large adsorption energy as compared to some monolayer borophene structures and its interfaces except h-borophene which has the high capacity than our work. We also calculated DOSES before and after intercalation of lithium. The diffusion barrier also calculated using nudge elastic band (NEB) as shown below.
To conclude first principle calculations are executed on novel bilayer b-borophene for the application as anode material in Li-ion batteries. We intercalated Li in bilayer b-borophene and observed stability of structure upon adsorption of 6 Li atoms that remain preserved. The adsorption energy is found to be higher than commercially available graphite anode material. The negative value of adsorption energy exhibits spontaneous process of Li adsorption that is key requirement for anode material. The calculated value of storage capacity appeared as 3080 mAh/g. Our material exhibit low diffusion barrier and low OCV i.e. 800 meV and 0.08V which confirms its potential as anode material. These results announce intercalation of Li in bilayer b-borophene is more feasible than monolayer.