Solid-State Direct Regeneration of Spent Lithium Cobalt Oxide Cathodes for Li-Ion Batteries

Regeneration of spent lithium-ion battery (LIB) electrode materials is essential for sustainable development of the LIB energy storage sector and resource management of the critical metals such as Li, Co, Ni, and Mn. Enormous use of LIBs has been seen in the last two decades in portable electronic devices. In addition, now it is predicted that LIBs will be exploited in electric vehicles and stationary energy storage systems in the coming decades. Wider exploitation of LIB energy storage technologies creates an alarming situation, especially for the resource management of critical metals and the environment. In this work, we report the direct regeneration of a spent lithium cobalt oxide (LCO) cathode material. The deficiency of Li concentration in spent cathode material is fulfilled by the solid-state regeneration process just by heating with the required amount of Li2CO3 at 740 °C for 6 h. In particular, the Li void in the defective LCO crystal structure has been repaired, and the morphology is restored into the pristine LCO. Elemental analysis confirmed the increase of Li content to 7.4% in the relithiated cathode material in comparison to the spent cathode (5.28% Li). The X-ray diffraction study revealed the repair of degraded phase cobalt oxide to pristine phase LCO. XPS analysis also indicated the repair of the degraded phase from Co2+ to Co3+ in the regenerated LCO. Scanning electron microscopy analysis showed the improvement of microcrystals in the regenerated LCO. Cyclic voltammetry analysis showed the enhancement of electrochemical properties in the regenerated LCO and exhibited an enhanced initial charge specific capacity to 148.31 mAh/g at 0.1C rate in comparison to the spent LCO. This work demonstrated a simple and cost-effective regeneration process of spent LCO compared to the pyrometallurgy and hydrometallurgy where the critical metals are recycled in the form of alloys and individual salts, respectively.