Direct regeneration of spent LiCoO2 cathodes with Ca2+-assisted molten salt strategy

Direct regeneration of spent cathodes through molten salt is economically and environmentally attractive for recycling of lithium-ion batteries due to elimination of metal extraction and mild regeneration conditions. However, low crystallinity and unsatisfactory restored performances of recycled cathode materials strongly retard their applications. Herein, a feasible Ca ²⁺ -assisted molten salt strategy for direct regeneration of LiCoO ₂ is proposed. With the addition of minor CaO into eutectic salts, interestingly, regeneration kinetics was significantly improved with complete microstructural repair and elevated crystallinity. Furthermore, homogeneous introduction of Ca ²⁺ into Li vacancies expedites the Li ⁺ transfer rate during electrochemical reactions with formation of speedy wave-shape diffusion pathways as confirmed by neutron powder diffraction. Benefiting from the observed structural changes that result from the molten salt with Ca ²⁺ addition, the recycled LiCoO ₂ battery showed outstanding capacities of 108.7 mAh/g at 4C, which delivered 188.7 % performance recovery of commercial new batteries. This simple process may open up new opportunities for sustainable recycling of spent batteries.