First-principles studies on lithium diffusion in cathodes of lithium-ion batteries

Abstract

The demands for sustainable energy storage make battery research active. LiCoO2 is a widely used cathode material for lithium-ion batteries. However, many studies about cathode materials are carried out owing to problems like high-cost, stability, performances and so on [4-7]. In this study, as part of those work, I wanted to evaluate three novel cathode materials by studying the diffusion of lithium in the materials. The diffusion of lithium-ions is related to the rate of charge and discharge of the batteries since lithium-ions intercalated or de-intercalated during cycles. Calculated materials are LiCoO2, Li3CrSiO5, LiCrO2, Mg3Cu2(SiO4)3 with density functional theory and nudged elastic band method. LiCoO2 is calculated for comparison, and Li3CrSiO5 has a similar hopping mechanism with LiCoO2 though it has bigger migration barriers. Thus, it would be necessary to further study this material for stability or other performances. The third material, LiCrO2, has layered structures like LiCoO2, and the calculated results are also similar to it. However, other experimental studies have shown that the hopping of chromium disturbs the lithium migration and the cyclability becomes bad. To verify this, total energies and migration barriers for various chromium concentrations are calculated, and the sufficient possibility of Cr migration is confirmed. Thus, to use LiCrO2 for cathode materials, some techniques to disturb chromium migration are needed. The last material, Mg3Cu2(SiO4)3 for magnesium-ion batteries, has much bigger migration barriers than other materials. This would be because the material has different structures with the other materials and magnesium ions have bigger valence than lithium-ions, so they could receive more electrostatic repulsion during migration. As a result, it seems that the other calculation is more necessary in order to make sure the reason and whether the material is promising or not. Through the method in this study, other novel materials for the cathode in batteries could be assessed in terms of lithium diffusion.