Lithium Ion Solvation and Intercalation at Anode-Electrolyte Interface from First Principles

Abstract

Lithium-ion batteries are commonly used to power many consumer devices such as handheld phones, laptops, portable music players, and even electric vehicles. The interface between the anode and the electrolyte plays a key role in the operation and performance of lithium-ion batteries. In this work, we use first principles molecular dynamics (FPMD) to examine the solvation of the Li ion at different distances from the graphite anode. We find that as Li+ approaches the anode, the coordination number of solvent molecules decreases suggesting that the Li ion must shed its solvation shell entirely to enter the anode. In addition, we estimate the energy required for intercalation of the Li ion into the graphite anode in the presence of the electrolyte. We find that the energy required for intercalation is dependent on the edge termination of the graphite due to electrostatic interactions between Li+ and the terminating species. We further verify the intercalation energy from our FPMD simulations using the nudged elastic band (NEB) method to find the minimum energy paths for entry as a function of different edge terminations. Our results can be utilized to design improved battery systems that optimize Li-ion transport into the anode material.