Deciphering the Degradation Mechanism Induced by the Air‐Exposure in Li ₂ NiO ₂ 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.