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In this paper, we developed an efficient and environment-friendly approach, the molten-salt-electrolysis (MSE), to recover lithium and cobalt from spent LiCoO 2 -based lithium-ion batteries (LIBs). Unlike the conventional ways that employ strong acid lixiviants and reducing agents, the spent LiCoO 2 was electrochemically reduced to either CoO or Co under controlled potentials at the cathode, releasing Li 2 O into molten salts where the Li 2 O combined with CO 2 generated at the carbon anode to produce Li 2 CO 3 . After electrolysis, CoO/Co and Li 2 CO 3 were leached out from the molten salts in water, and the recovery rates of Li and Co were high up to 85% and 99%, respectively. In addition, the LiCoO 2 was regenerated from the recovered CoO and Li 2 CO 3 , exhibiting excellent electrochemical performances as a cathode in a LIB. Overall, the MSE route employs electrons as the reducing agent and molten salt as a solvent to recycle spent LIBs, which could be a simple, comprehensive, and green process for recycling various cathode materials.

An ammonium chloride roasting approach can convert lithium metal oxides to water-soluble lithium and transition metal chlorides at 300 °C, promising an energy-efficient and environmentally benign way to recover end-of-life lithium-ion batteries. Unlike conventional chlorination processes, the roasting of LiCoO2 using NH4Cl as both reducing and chlorination agents is complex, and thus more efforts such as thermodynamics and the underlying mechanism are required to be understood. This paper aims to study the chlorination process by comprehensive thermodynamic analysis and a variety of control experiments such as operating temperature, gas atmosphere, NH4Cl/LiCoO2 mass ratios, and the way of mixing feedstocks. It is found that the chlorination of LiCoO2 is governed by a solid-to-solid reaction mechanism based on thermodynamics, thermal analysis, and roasting products. Finally, the regenerated LiCoO2 delivers a specific capacity of over 139.8 mAh g–1 at 0.5C with a capacity retention rate of 99% after 100 cycles. Overall, the chlorination process can be engineered by adjusting the temperatures, pressure, and contact area between NH4Cl and LiCoO2 to further reduce the energy consumption and thereby increase the utilization of NH4Cl and chlorination efficiencies.

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