Efficient Direct Recycling of Degraded LiMn₂O₄ Cathodes by One-Step Hydrothermal Relithiation

Due to the large demand of lithium-ion batteries (LIBs) for energy storage in daily life and the limited lifetime of commercial LIB cells, exploring green and sustainable recycling methods becomes an urgent need to mitigate the environmental and economic issues associated with waste LIBs. In this work, we demonstrate an efficient direct recycling method to regenerate degraded lithium manganese oxide (LMO) cathodes to restore their high capacity, long cycling stability, and high rate performance, on par with pristine LMO materials. This one-step regeneration, achieved by a hydrothermal reaction in dilution Li-containing solution, enables the reconstruction of desired stoichiometry and microphase purity, which is further validated by testing spent LIBs with different states of health. Life-cycle analysis suggested the great environmental and economic benefits enabled by this direct regeneration method compared with today's pyro- and hydrometallurgical processes. This work not only represents a fundamental understanding of the relithiation mechanism of spent cathodes but also provides a potential solution for sustainable and closed-loop recycling and remanufacturing of energy materials.