Mechanical properties of high entropy layered cathode structures

Abstract

Based on the high entropy theory, Fe, Mn, and Ni elements are doped into the transition metal Co sites in the LiCoO₂ cathode structure. Two high entropy oxide cathode structures, namely the LiTM_uniformO₂ model and the LiTM_non-uniformO₂ model, are constructed based on whether the distribution of transition metal elements is uniform. The crystal structure parameters, mechanical performance parameters, anisotropy index, and stress-strain performance of two high entropy models are calculated using first principles calculation method, and the structural stability is analyzed from a mechanical perspective. The effects of lithium-ion deintercalation on the crystal structure, mechanical properties, and stress-strain properties of two structures during the charging and discharging processes are studied. The research results indicate that the synergistic effect of multiple transition metal atoms is beneficial for improving the stability and mechanical properties of the cathode structure. The study of mechanical properties during delithiation process shows that as the degree of lithium removal increases, the Young's modulus of the material continues to decrease, while plasticity and toughness first increase and then decrease. Compared with non-uniform model, uniform model has better mechanical properties and cycle stability. The stress-strain performance of the LiTM_uniformO₂ model is superior to that of the LiTM_nonuniformO₂ model, and it can resist the influence of internal stress during battery cycling. This work provides some theoretical guidance for studying cathode materials with excellent mechanical properties and high energy density.