Unveiling thermal decomposition kinetics of Single-Crystalline Ni-Rich LiNi0.88Co0.07Mn0.05O2 cathode for safe Lithium-Ion batteries

• Thermal decomposition of NCM families is followed by Avrami-Erofeev mechanism. • Phase transition contributes to determinative exothermic reaction for instability. • Single-crystalline NCM shows less thermal stability than poly-crystalline one. Insufficient thermal stabilities of LiNi x Co y Mn 1-x-y O 2 (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 0.88 Co 0.07 Mn 0.05 O 2 . 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 0.88 Co 0.07 Mn 0.05 O 2 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 0.88 Co 0.07 Mn 0.05 O 2 cathodes and insights of NCM families protection.