Direct conversion of degraded LiCoO2 cathode materials into high-performance LiCoO2: A closed-loop green recycling strategy for spent lithium-ion batteries

Lithium cobalt oxide (LiCoO2) is the most widely used cathode materials for smart phones and laptop batteries. With the rapid development of portable electronics, more than 100,000 tons of spent lithium-ion batteries (LIBs) are produced every year. Conventional battery recycling processes including pyrometallurgical and hydrometallurgical processes mainly aim at extracting valuable metallic components from spent LIB cathodes, which requires high temperature reduction and/or acid/alkali chemicals to destroy covalent bond in cathodes and convert them into atoms for further extraction. The former leads to high energy consumption and the latter produces a lot of wastewater, which not only increases cost, but also damages our environment. Moreover, traditional recycling starts from spent battery cathodes and ends up with lithium/cobalt salts, which is unsustainable. Herein, a different recycling strategy to directly convert degraded LiCoO2 into high-voltage LiCoO2 cathode materials was proposed, featuring a closed-loop and green procedure. The directly-converted LiCoO2 from spent cathodes exhibits excellent cyclability at 4.5 V with a high capacity retention of 97.4% after 100 cycles, even superior than pristine LiCoO2. The recovery efficiencies of lithium and cobalt reach 91.3% and 93.5%, respectively, and the energy consumption could be greatly reduced since the roasting temperature was dropped below 400 °C with the assistance of ammonium sulfate. Due to the utilization of low-cost reagents and water as the leaching agent, the potential benefit of the recovery process was estimated to reach 6.94 $/kg cell.