Closed-loop selective recycling process of spent LiNi_xCo_yMn_1−x-yO₂ batteries by thermal-driven conversion

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 LiNi_1/3Co_1/3Mn_1/3O₂ 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 LiNi_0.5Co_0.2Mn_0.3O₂ (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 SO₄^2- 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 SO₄^2- 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.