Closed-loop selective recycling process of spent LiNixCoyMn1−x-yO2 batteries by thermal-driven conversion

Abstract

The consumption of lithium-ion batteries raises raw material demand for and the pressure on ecological sustainability. Metals can be recovered in shorter paths while considerably boosting material use, hence selective recycling of specific elements is becoming a hotspot. This paper proposes a thermally-driven closed-loop recycling process for scrap LiNi1/3Co1/3Mn1/3O2 cathodes, in which Li is efficiently extracted by water leaching. Then, by combining the leaching residue with Li2CO3, a solid-phase synthesis is carried out, with Li being targeted to heal into Ni-Co-Mn-O to construct the layered structure. The electrochemical performance of the resynthesized cathode material is comparable to that of the commercial LiNi0.5Co0.2Mn0.3O2 (NCM523) material. During the thermal-driven conversion, solid-state processes can be observed. To ensure charge conservation, Li+ in the unstable layered structure is released and mixed with SO42- to produce Li2SO4, and lattice oxygen escapes and transforms with Ni2+ to generate NiO. For the resynthesized process, the spherical shape of Ni-Co-Mn-O is largely retained. Notably, sulfur is remained in the form of SO42- throughout the closed-loop process and is therefore free of contamination. The thermal-driven conversion recycling process revealed in this study will encourage researchers to ensure more efforts in efficient and selective recovery for sustainable energy storage of rechargeable batteries.