LiF as a Crack/Defect Healer and Structural Stabilizer for the Spent Lithium Cobalt Oxide

Abstract

The proliferation of lithium-ion batteries results in a substantial accumulation of spent batteries. Traditional pyrometallurgical and hydrometallurgical processes require significant energy inputs, involve the use of hazardous chemicals, and generate large amounts of pollutants, making them inefficient for the economic or environmental recycling of spent batteries. For the spent lithium cobalt oxide (LCO) cathodes, which lose electrochemical activity due to the structural damage, we demonstrated that LiF could serve as both a crack/defect healer to repair the damaged structure and a structural stabilizer to consolidate the electrode/electrolyte interface and the reversibility of phase transitions. The density functional theory calculations revealed the presence of F atoms in the U-LCO crystal leads to a widened energy separation between the Co 3d and O 2p orbitals, such an alteration effectively suppresses the activity of lattice oxygen and stabilizes the structure of U-LCO. The as-upcycled LCO cathode demonstrates significantly improved stability with an impressive capacity retention of 81.6% after 260 cycles, surpassing those of the pristine LCO (62.3%) and normally regenerated LCO (35.6%). Moreover, the recycling process only involves a solid sintering procedure, leading to a reduced carbon footprint by 73.1% and 64.1%, and increased benefits by 62.2% and 47.7%, as compared with the pyro and hydro methods, respectively. The as-proposed upcycling strategy provides a practical and efficient solution for the closed-loop development of LCO batteries.