Abstract:

Pre-lithiation technology can significantly enhance the initial coulombic efficiency and cycle life of batteries. Among the various prelithiation approaches, cathode lithium replenishment agent technology is one of the simplest and most effective methods. Li₂NiO₂ (LNO) is a widely used additive owing to its simple preparation process, low cost, and environmental friendliness. However, Li₂NiO₂ currently faces issues such as low specific capacity and poor environmental stability, which limit its wide application. To address these issues, the study prepared a lithium-rich nickelate GP-LNO with high environmental stability and specific capacity through vacuum sintering. For comparison, a lithium-rich nickelate NM-LNO sintered under atmospheric pressure using identical processes. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed that GP-LNO exhibited superior particle integrity, higher crystallinity, and lower NiO impurity peaks. The results of potentiometric titration show that GP-LNO had better environmental stability, After 360 minutes in an environment with a temperature of 25 ℃ and humidity of 38%, the total Li content of GP-LNO increased by only 0.04%, compared to a 0.94% increase for NM-LNO under the same conditions. Electrochemical performance analysis revealed that GP-LNO achieved a higher first-cycle charge capacity. In the voltage range of 2.8—4.3 V, using constant current and constant voltage charging and discharging at a rate of 0.05 C, GP-LNO recorded a first-cycle capacity of 434.21 mAh/g, surpassing NM-LNO's capacity by 28.2 mAh/g. As the rate increased, the first-cycle charging capacity of GP-LNO first increased and then decreased. At a rate of 0.5 C, the first-cycle charge capacity of GP-LNO reached 438.64 mAh/g. This work significantly improved the first-cycle charge capacity and irreversible capacity of LNO material through vacuum sintering, by preventing Ni oxidation and impurity formation, and effectively enhanced the environmental stability of LNO, which provide valuable insights for advancing industrial application.

Key words: Li₂NiO₂, pre-lithiation technology, environmental stability, first cycle capacity, vacuum sinterin