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

Lithium manganese oxide (LiMnO) 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 (WO). Different WO wt % were investigated before settling for 0.5%WO-LMO as the synergic surface-modified LMO. Using galvanostatic charge-discharge, 0.50 WO-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 WO-LMO possesses better ion diffusion than pristine LMO, around 10 and 10 cm·s 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.