Recovery and Morphological Control of LiCoO2 from Spent Lithium Ion Batteries
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 300oC to 900oC 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.