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A way of directly repairing spent lithium-ion battery cathode materials is needed in response to environmental pollution and resource depletion. In this work, we report a green repair method involving coupled mechanochemistry and solid-state reactions for spent lithium-ion batteries. During the ball-milling repair process, an added manganese source enters into the degraded LiMn2O4 (LMO) crystal structure in order to fill the Mn vacancies formed by Mn deficiency due to the Jahn–Teller effect, thereby repairing the LMO's chemical composition. An added carbon source acts not only as a lubricant but also as a conductor to improve the material's electrical conductivity. Meanwhile, mechanical force reduces the crystal size of the LMO particles, increasing the amount of active sites for electrochemical reactions. Jahn–Teller distortion is successfully suppressed by cation disorder in the LMO material. The cycling stability and rate performance of the repaired cathode material are thereby greatly improved, with the discharge specific capacity being more than twice that of commercial LMO. The proposed solid-state mechanochemical in situ repair process, which is safe for the environment and simple to use, may be extended to the repair of other waste materials without consuming highly acidic or alkaline chemical reagents.
Lin et al. (Thu,) studied this question.