Sustainable upcycling of mixed spent cathodes to a high-voltage polyanionic cathode material.

Sustainable battery recycling is essential for achieving resource conservation and alleviating environmental issues. Many open/closed-loop strategies for critical metal recycling or direct recovery aim at a single component, and the reuse of mixed cathode materials is a significant challenge. To address this barrier, here we propose an upcycling strategy for spent LiFePO 4 and Mn-rich cathodes by structural design and transition metal replacement, for which uses a green deep eutectic solvent to regenerate a high-voltage polyanionic cathode material. This process ensures the complete recycling of all the elements in mixed cathodes and the deep eutectic solvent can be reused. The regenerated LiFe 0.5 Mn 0.5 PO 4 has an increased mean voltage (3.68 V versus Li/Li + ) and energy density (559 Wh kg -1 ) compared with a commercial LiFePO 4 (3.38 V and 524 Wh kg -1 ). The proposed upcycling strategy can expand at a gram-grade scale and was also applicable for LiFe 0.5 Mn 0.5 PO 4 recovery, thus achieving a closed-loop recycling between the mixed spent cathodes and the next generation cathode materials. Techno-economic analysis shows that this strategy has potentially high environmental and economic benefits, while providing a sustainable approach for the value-added utilization of waste battery materials.