Decoding lithium-ion dynamics: unveiling the role of concentrations and local environments in spinel Li_xMn₂O₄

The spinel LiMn₂O₄ (LMO) offers efficient lithium-ion diffusion channels, yet the mechanisms underlying its transport dynamics remain elusive. In this study, we employ molecular dynamics (MD) simulations, climbing-image nudged elastic band (CI-NEB) calculations, and electronic structure analyses to elucidate the mechanisms governing lithium-ion dynamics in spinel LMO. Our results reveal the critical role of lithium-ion concentrations and asymmetric Mn³⁺/Mn⁴⁺ distributions in modulating diffusion barriers and ion migration pathways. The Jahn-Teller distortions, induced by Mn³⁺ ions, introduce anisotropic structural changes that significantly alter the energy landscape for diffusion. Notably, we identify a non-linear relationship between the lithium-ion concentration and ionic mobility: low lithium-ion concentrations enable rapid ion transport, while high concentrations increase Coulomb repulsion, hindering diffusion. These findings provide new insights into the coupling of electronic, structural, and ionic properties in LMO, emphasizing the pivotal role of the electronic structure and local environment in optimizing its performance as a cathode material.