Exfoliation of Electrolyte-Intercalated Graphene: Molecular Dynamics Simulation Study

Abstract

Ethylene carbonate (EC) is one of the most common electrolyte for lithium ion batteries, but it has a narrow working temperature range. Despite the structural similarity, propylene carbonate (PC) has a wider working temperature range as an electrolyte, but it induces exfoliation of the graphite anode. To understand the different behavior of EC and PC electrolytes at the atomistic level, we performed molecular dynamics (MD) simulations of electrolyte intercalated graphene sheets. We observed no diffusion of electrolyte between graphene sheets when interlayer distance is less than 6 A, but both of EC and PC form monolayer between graphene sheets with comparable density when interlayer distance is 7–8 A. Because of the size difference, the intercalated PC molecules induce a longer separation distance between graphene sheets compared to that of EC. The longer separation with PC intercalant induces more frequent sliding-exfoliation movement. We found that the exfoliation diffusion coefficient of the graphene s...