Decoupling the Effect of Electrolyte Infiltration on the Intercalation of Alkali Metal Ions in Highly Oriented Pyrolytic Graphite

Diffusion coefficients of ion in graphitic materials are responsible for high-rate batteries. However, the complex electrochemical response presented a challenge to accurately measure the diffusion coefficient of alkali-metal ions in graphitic materials. Here we design a method to identify the diffusion coefficients of Li+ and Na+ in highly oriented pyrolytic graphite (HOPG) with and without presence of liquid electrolyte infiltration. The results reveal inherent high diffusivity of Li+ in HOPG (∼10-7 cm2·s-1), as compared to HOPG with electrolyte infiltration (∼10-8 cm2·s-1), while Na+ has almost no interlayer diffusion without solvent infiltration. The presence of electrolyte has different effect on the interlayer diffusion of Li+ and Na+.