Adaptable Eutectic Salt for the Direct Recycling of Highly Degraded Layer Cathodes.

Recycling spent lithium-ion batteries (LIBs) is promising for resource reuse and environmental conservation but suffers from complex processing and loss of embedded value of spent LIBs in conventional metallurgy-based recycling routes. Herein, we selected a eutectic LiI-LiOH salt with the lowest eutectic point among binary eutectic lithium salt systems to provide a Li-rich molten environment, not only offering excess lithium but benefiting ion diffusion compared with that in the solid environment. Hence, the highly degraded LiNi 0.5 Co 0.2 Mn 0.3 O 2 in spent LIBs which suffers high Li-deficiency and serious structural defects with harmful phase transitions is directly regenerated. A facile one-step heating strategy in the presence of a combination of the eutectic lithium salt and Co 2 O 3 and MnO 2 additives not only simplifies the recycling process but also endows the cathode materials with lithium supplementation and structural ordering, which contributes to a restoration of the capacity and stable cycling performance. In particular, this eutectic salt with a low eutectic point helps decrease the temperature and time of the direct recycling process and shows good adaptability for other layer oxide cathode materials (LiCoO 2 and LiNi 0.6 Co 0.2 Mn 0.2 O 2 ) in spent LIBs with varying cathode chemistry. As such, the feasibility of the direct recycling route is improved and broadened with simple and efficient processing, providing an idea for energy-saving cathode regeneration in future LIB recycling.