Power characteristics of spinel cathodes correlated with elastic softness and phase transformation for high-power lithium-ion batteries

Abstract

The power characteristics of lithium-ion batteries (LIBs) are crucial for the advent of commercialized, high-power applications, such as electric vehicles. Through both first-principles multiscale simulations and experiments, here, we present fundamental understanding on the power characteristics of the high-voltage spinel cathode correlated with its elastic softness and phase transformation in nanodomains for high-power LIBs. Atomic models of LiNi_0.5Mn_1.5O₄ and LiNi_0.5Mn_1.5−xTi_xO₄ are developed for multiscale phase field modeling based on structural information for the as-prepared nanopowders. The combined computational and experimental investigations suggest that the thermodynamic phase stability of LiNi_0.5Mn_1.5O₄ can be effectively enhanced by the incorporation of Ti into the structure without any change to the redox mechanism. Ti incorporation provides a faster ionic mobility and the improved phase stability because of the reinforced Ti⁴⁺–O bonds. Based on the multiscale phase transformation kinetics, LiNi_0.5Mn_1.5−xTi_xO₄ exhibits an enhanced elastic softness and slower phase separation than LiNi_0.5Mn_1.5O₄ in the nanodomain during Li⁺ insertion and extraction. Such characteristics are mainly responsible for the improved electrochemical performance at higher current rates, as confirmed by electrochemical experiments. This fundamental understanding of the power characteristics with respect to the correlations with elastic softness and phase transformation will provide a guideline to develop and design advanced materials for high-power LIBs.