Barrier Reduction of Lithium Ion Tunneling through Graphene with Hybrid Defects: First-Principles Calculations

Atomically thin 2D materials such as graphene and hexagonal boron nitride are increasingly explored as a possible platform for atomic diffusion barriers and novel separation technologies. However, a perfectly dense networked lattice structure is impermeable to nearly all ions thereby limiting their application as atomically thin barriers. In this work, climbing image nudged elastic band simulation is applied to identify meaningful strategies to reduce the energy barrier height of Li ions tunneling through monolayer (ML) graphene sheets. Our results reveal that defects such as pore defects, ripples, and some atomic substitutions can effectively reduce the Li ion tunneling barrier and the defects can alter the Li ion adsorption energy to influence the deintercalation process. Furthermore, hybrid defects can balance the energy barrier and potential well to increase the permeability of Li ions through graphene sheets.