The recycling of spent lithium-ion batteries is an effective approach to alleviating environmental concerns and promoting resource conservation. LiFePO4 batteries have been widely used in electric vehicles and energy storage stations. Currently, lithium loss, resulting in formation of Fe(III) phase, is mainly responsible for the capacity fade of LiFePO4 cathode. Another factor is poor electrical conductivity that limits its rate capability. Here, we report the use of a multifunctional organic lithium salt (3,4-dihydroxybenzonitrile dilithium) to restore spent LiFePO4 cathode by direct regeneration. The degraded LiFePO4 particles are well coupled with the functional groups of the organic lithium salt, so that lithium fills vacancies and cyano groups create a reductive atmosphere to inhibit Fe(III) phase. At the same time, pyrolysis of the salt produces an amorphous conductive carbon layer that coats the LiFePO4 particles, which improves Li-ion and electron transfer kinetics. The restored LiFePO4 cathode shows good cycling stability and rate performance (a high capacity retention of 88% after 400 cycles at 5 C). This lithium salt can also be used to recover degraded transition metal oxide-based cathodes. A techno-economic analysis suggests that this strategy has higher environmental and economic benefits, compared with the traditional recycling methods.

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 LiNi0.5Co0.2Mn0.3O2 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 Co2O3 and MnO2 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 (LiCoO2 and LiNi0.6Co0.2Mn0.2O2) 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.