Deciphering the Degradation Mechanism Induced by the Air‐Exposure in Li2NiO2 and the Recovery Strategy

Cathode prelithium agent is regarded as the most applicable approach to compensate the initial capacity loss in lithium ion batteries (LIBs). Li2NiO2 (LNO) has attracted numerous attention due to its superior environmental stability and reliable synthesis approach. To promote the commercial application of LNO, the understanding of the degradation mechanism induced by air‐exposure and finding reliable strategies to improve the air stability are necessary. Herein, by preserving the LNO in different environments (relative humidity of 70% and 40%), the surface chemistry evolution of LNO is subtly investigated, which shows Li2CO3 and LiOH cover the surface of the LNO, which decline the Li+ diffusion kinetics as well as the charge capacity. What’s more, the slurry turns gel when the LNO exposed to the environment of 70% relative humidity for 2 days and 40% relative humidity for 5 days. Facile approaches, including washing the deteriorative LNO with ethanol, reacting the alkali components with H3BO3, and coating the LNO with Al2O3 are conducted to recover the disabled LNO, which retains 84.2% of initial capacity. In addition, a coating approach is proposed for the fresh LNO to effectively improve the air stability. This work provides guideline to the commercial application of the LNO.