Recovery and Morphological Control of LiCoO2 from Spent Lithium Ion Batteries

Nowadays, lithium ion batterys (LIBs) are commonly used electrochemical power source in mobile devices, such as smart phone and lap-top computer, and electric vehicles. As increasing the utilization of LIBs, it must be noted that equal amounts of spent LIBs are produced after lifetime failure. The massive amount of lithium ion battery waste will cause the environmental pollution, increasing energy demand for treatment, and rapid decrease in primary resources, since it contains lots of chemical substances such as Co, Cu, Li, organic electrolytes, and plastics. So, the recycling of major components from LIBs is considered to be a beneficial way to prevent environmental pollution and improve the utilization of the world’s metal resources. Cobalt showed the highest concentration and cost among the recovered materials from LIBs.

 In this study, we suggest environmentally benign leaching and separation process of cobalt by using the mild organic acid. And, it was directly used for synthesis and morphological control of Co₃O₄ and LiCoO₂ active materials.

 Many organic acids successfully dissolved the cobalt from the spent cathode material. While the leaching efficiency was a little lower than that of sulfuric acid, citric and malic acid showed more than 85% leaching efficiency among the various acids. The difference between citric and malic acids and the others is only that they have one hydroxyl group with 2- or 3- carboxylic acid groups.

 After the leaching experiment, the obtained cobalt ion solution was transferred to autoclave vessel with appropriate additives. Under the autogenic pressurized condition, some cobalt compounds were precipitated with the various nanostructures, such as sphere, rod, plate, and fiber. Then, the cobalt compounds were thermally treated in Air environment from 300^oC to 900^oC to produce nanostructured Co₃O₄. Also, the Co₃O₄ and cobalt compounds were respectively mixed with Li₂CO₃ powder and calcined to re-synthesize the nanostructured LiCoO₂.  With the appropriate thermal treatment, the nanostructures could be almost passed down from the cobalt compounds to Co₃O₄ and LiCoO₂. XRD results revealed that Co₃O₄-mediated LiCoO₂ had almost same crystallinity and cationic ordering with commercial one. In the case of cobalt compounds-mediated one, however, the cationic ordering that is the ratio of (003) reflection and (104) reflection was lower than commercial LiCoO₂. And, the re-synthesized LiCoO₂ was also applied to lithium-ion battery and showed very promising performance. More detailed experimental and results will be discussed in our presentation.