Lithium-ion batteries (LIBs) have emerged as the battery of choice for rapidly growing markets in electric vehicles (EVs) and grid electricity storage. This spurs a great demand for lithium, graphite, cobalt, and nickel that could outstrip the supply of virgin materials. Thus, there is an enormous interest in the development of new sustainable technologies for recycling and recovery of valuable materials from secondary resources, especially from used lithium-ion batteries. Compared to conventional high-temperature pyrometallurgical or hydrometallurgical methods, direct recycling of LIBs is a more desirable approach because it can directly regenerate the cathode materials by relithiation without destroying the LIB compounds. Additionally, direct recycling is a comparatively low-cost and less resource-intensive method of recovering LIB materials.

However, completely regenerating the full capacity and long-term performance of the original materials is still particularly challenging. For instance, the cathode materials are often coated with a nanometer-thick protecting layer, which is engineered to reduce the degrading effect on the cathode from direct contact with the electrolyte. The long-term charge-discharge cycling causes damage to this coating layer, and thus it needs to be repaired in order to recover the material performance. To address this challenge, we have developed a novel process that can regenerate and upgrade cathode materials from aged lithium-ion batteries, as well as create a new coating layer to improve the performance of the cathode materials. In this presentation, we will provide a case study to show the performance improvement of recycled lithium cobalt oxide (LCO) materials by forming an alumina coating layer on the surface. By controlling the thickness and sintering temperature, this surface alumina coating can be an effective way to improve the stability and cyclability of recycled LCO cathode materials. Material characterization by XPS, SEM, STEM, and XRD helps to reveal the structure and composition of the surface alumina coating layer, and provides insights into the healing and protective roles of this layer for recycled LCO particles.