Study of Lithium Transport in NMC Layered Oxide Cathode Material Using Multiscale Computational Approach

Enhancing the rate capability of lithium-ion batteries (LIBs), as a promising energy storage device, requires a comprehensive understanding of lithium (Li) transport in their constituent parts. In this study, Li transport in the LiNi_0.333Mn_0.333Co_0.333O₂ (NMC111) cathode active material was examined by a multiscale computational approach ranging from density functional theory (DFT) to Monte Carlo (MC) simulations. The approach was first applied to lithium cobalt oxide (LCO) to compare our model with an existing available one for barrier energies in layered structures. Two barrier energy models, named the interpolated barrier model and the local cluster expansion, together with the periodic cluster expansion, were integrated into the KMC algorithm. Results of KMC simulations in LCO were similar using both barrier models. Thus, the approach was then applied to NMC111 by using only the much simpler interpolated barrier model. Our MC simulations showed a perfect honeycomb-like ordering of Li ions in the Li layer of NMC111 at a Li concentration of 0.8. This perfect ordering of Li ions caused a significant decrease in the thermodynamic factor, which consequently resulted in a minimum in the chemical diffusion coefficient at this concentration, confirming previous studies. The perfect correlation between our simulations and the experimental measurements of other studies reflects the precision of our formalism in studying the transport behavior of Li in the NMC111 crystal.