A vapor thermal approach to selective recycling of spent lithium-ion batteries

Abstract

Minimizing energy consumption, the amount of chemicals used, and secondary wastes is key to achieving a techno-economic approach for recycling spent lithium-ion batteries (LIBs). Herein, we report a vapor thermal reduction approach to converting lithium transition metal oxides (LTMOs) to water-insoluble TMOs and water-soluble Li salts with markedly reduced water and chemical use, and temperature. Compared with the hydrothermal process, the water vapor approach reduces the usage of water and ammonium salts, making the selective extraction happen at <250 °C. In addition, thermodynamic calculations imply that ammonium salts act as the reducing agent to drive the selective conversion because of the synergic effect of water vapor and ammonium salts. By changing the amount of water and salts, we confirm that ammonium ions and water vapor co-drive the selective extraction of Li from LTMOs with 3–25% of water compared with the hydrothermal process and 18–30% of the amount of salt of the roasting process. Using the optimized water and NH₄Cl or (NH₄)₂SO₄, the extraction efficiency of both Li and TMs reaches 98%. Overall, this paper provides a green method to recycle spent LIBs, which can be expanded to selectively separate value metals from various feedstocks.