Extractive and Recovery of Lithium Carbonate from Waste Secondary Battery Using Eco-Friendly Molten Carbonate Electrolyte

초록

This study explores a high-efficiency lithium recovery method from spent lithium-ion battery cathodes using an environmentally friendly pyrometallurgical approach. A molten carbonate electrolysis process was employed to reduce NCM composite oxides, thereby extracting lithium within the molten salt. By eliminating the use of acidic solutions at all process stages, this study effectively addresses the critical issue of wastewater generation in conventional processes. The reduced lithium oxide either reacted with carbon dioxide present in the molten salt or was directly converted into lithium carbonate at the carbon electrode. Meanwhile, the oxides of other metal species underwent reduction and remained electrodeposited, allowing for initial separation. Lithium was further isolated through a two-step water washing and fractionation process based on solubility differences. Prior to electrolysis, cyclic voltammetry analysis was conducted to determine the theoretical reduction potentials of the metal oxides through electrochemical calculations. It was confirmed that lithium was reduced at a potential of 1.3 V. During electrolysis, a constant potential application and current analysis revealed an average current of 1.3 A and a total electrode potential of 2.6 V, enabling the observation of the redox behavior of NCM elements. The process achieved a 95% lithium carbonate recovery rate, and the recovered lithium carbonate exhibited a purity of 99% with a well-defined crystalline structure, demonstrating excellent recovery efficiency.

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