Thermal-Driven Surface Self-Armoring and ElectrochemicalStabilization of Single-Crystal LiNi0.5Co0.2Mn0.3O2 Cathode at High-Voltage Operation forLi Rechargeable Battery

The traditional viewpoint holds that the increasing cycling temperature reduces the life of LiNi0.5Co0.2Mn0.3O2 (NCM523) due to accelerated interfacial reactions between the electrode and the electrolyte, leading to degraded battery performance and increased safety risks. However, a different trend during the cycling of prepared small-size single-crystal NCM523 was discovered. Specifically, elevated operating temperature actually improves the cycling performance of the battery. At 55 °C, the battery achieved an impressive retention rate of 78.5% after 100 cycles at a rate of 1 C and a voltage range of 2–4.5 V, which far exceeded the corresponding performance at 25 °C. Therefore, the relationship between cycling stability and temperature was further investigated and proved that the cycling stability of NCM523 is closely related to the special interfacial reactions. When cycling at 55 °C, a dense passivation CEI layer that is rich in inorganic compounds with high oxidation resistance and mechanical strength was in situ formed on the surface of NCM523, which acts as a strong shield to protect the NCM matrix and effectively improve the battery’s cycling stability. This study elucidates the critical importance of interfacial reactions on stability and provides insights to achieve high stability of lithium-ion batteries under harsh conditions.