Upcycling spent cathodes into single-crystalline Ni-rich cathode materials through selective lithium extraction

Direct recycling has been considered the most promising method of recycling spent batteries because of its eco-friendliness and cost-effectiveness. However, the uneven distribution of elements and particle sizes in spent cathode materials, caused by different states of health, presents a challenge for direct recycling. In this study, we employed a pre-treatment process using chlorination to selectively extract residual lithium and enhance the uniformity of the particle sizes in a spent LiNi_0.6Co_0.2Mn_0.2O₂ cathode. Furthermore, a multi-step aging process was designed to increase the primary particle size and minimize impurity formation, resulting in the successful synthesis of upcycled single-crystalline LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811). The bimodal electrode, which contained both upcycled single-crystalline and commercially available polycrystalline NCM811, exhibited a large discharge capacity of 191.3 mA h g⁻¹ at 0.2C and maintained a stable cycle performance of 84.1% after 300 cycles at 1C. Our study highlights the use of selective lithium extraction in the regeneration process, enabling the homogenization of the element distribution and particle size in spent cathode materials as well as the effective utilization of upcycled single-crystalline cathode materials.