Analysis of Graphene Coating on Si Anode and Defect Engineering for Lithium Ion Battery

Silicon is the most promising anode material due to its huge capacity about 4200mAh/g and their abundance. However its usage is hindered by large volume expansion, causing pulverization and so on. To reduce the problems, coating on silicon anode is one of the efficiency methods. In this presentation, computational study on the effect of graphene coating to Si anode material is performed by using density functional theory calculations. We construct the atomic model to examine interactions between amorphous silicon and graphene during lithiation. The lithiation of Si anode increases the not only mechanical contact force between outer graphene layer and amorphous silicon but also the shear resistance. To explain the interaction between graphene and silicon, we examine the charge distribution of silicon and graphene considering lithiation insertion. The number of density, electron field distribution and electric potential are also calculated. Charge-non polar interaction between Li-ion and graphene increase the contact energy between graphene-silicon. In addition, we also study the effect of defect on graphene such as mono, di, and stone-wales defect. These defects increase the contact force between defected graphene and lithium silicide.