Unveiling thermal decomposition kinetics of Single-Crystalline Ni-Rich LiNi_0.88Co_0.07Mn_0.05O₂ cathode for safe Lithium-Ion batteries

Insufficient thermal stabilities of LiNi_xCo_yMn_1-x-yO₂ (NCM) families have aroused wide concerns and safety threats against large-scale application due to oxygen releasing and exothermic side reactions. Towards energy-dense batteries, single-crystalline NCM has been recently highlighted as a promising substitution in providing improved capacity retention beyond polycrystalline counterparts. However, their thermal-driven degradation mechanism remains under investigation and yet critically essential. In this contribution, we have rationally explored the thermal-driven fading behavior of delithiated single-crystalline and polycrystalline LiNi_0.88Co_0.07Mn_0.05O₂. Followed by the Avrami-Erofeev mechanism, a three-step decomposition procedure has been deconvoluted from time-resolved X-ray diffraction and physicochemical analysis, in terms of solid electrolyte interface (SEI) decomposition, layered-to-spinel transition and spinel-to-rock-salt transition. According to thermal kinetic analysis, polycrystalline LiNi_0.88Co_0.07Mn_0.05O₂ exhibits higher decomposition temperature and lower decomposition rate than that in single-crystalline counterparts, contributing to better thermal stability. This study has provided a fundamental understanding of the thermal decomposition of Ni-rich LiNi_0.88Co_0.07Mn_0.05O₂ cathodes and insights of NCM families protection.