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 Ca2+-assisted molten salt strategy for direct regeneration of LiCoO2 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 Ca2+ 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 Ca2+ addition, the recycled LiCoO2 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.