High-Valence Surface-Modified LMO Cathode Materials for Lithium-Ion Batteries: Diffusion Kinetics and Operando Thermal Stability Investigation

Lithium manganese oxide (LiMn₂O₄) is a prevalent cathode material for lithium-ion batteries due to its low cost, abundant material sources, and ecofriendliness. However, its capacity fade, low energy density, and fast auto-discharge hinders its large-scale commercialization. Consequently, scientists are urged to achieve high-performance LMO cathodes through material doping and surface modification using a wide range of transition metals, polymers, and carbon precursors. Few studies have considered the potential of high-valence transition metal oxides in stabilizing the LMO's cycling process and enhancing the overall battery performance. In this work, we report the synthesis of surface-modified lithium manganese oxide using high-valence tungsten oxide (W^VIO₃). Different WO₃ wt % were investigated before settling for 0.5%WO₃-LMO as the synergic surface-modified LMO. Using galvanostatic charge-discharge, 0.50 WO₃-LMO exhibited better rate capability by retaining 51% of its initial capacity at a 20C rate, compared to 34% for the pristine LMO. Furthermore, cyclic voltammetry at different scan rates showed that 0.50 WO₃-LMO possesses better ion diffusion than pristine LMO, around 10^-11 and 10^-13 cm²·s^-1 respectively. Finally, using in situ Raman spectroscopy, reaction mechanisms during cycling were investigated, and operando accelerating rate calorimetry (ARC) visualized the surface-modified LMO's cycling thermal stability and highlighted its potential use for safe high-voltage lithium-ion batteries in automotive applications.