Dissolution of Spent NCM Cathodes Via Electron Transfer from the Anaerobic Respiration of Shewanella Putrefaciens

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With the rapid growth of the electric vehicle (EV) market, the global demand for lithium-ion batteries (LIBs) is increasing significantly. As the LIB market expands, we are also confronting the challenge of disposing of the increasing number of spent LIBs. Currently, pyrometallurgy and hydrometallurgy are the commercialized methods for recycling spent LIBs. However, these processes result in significant environmental pollution, high energy consumption and the depletion of valuable resources such as Li and Mn in the slag. Here, we explored the dissolution of spent NCM622 cathodes, a critical component of LIBs, using bioleaching via the anaerobic respiration of Shewanella putrefaciens bacteria in the neutral environment (i.e., pH 7.5). This study enhances the novelty of bioleaching as an eco-friendly and simple technology. The spent NCM622 cathodes were dissolved by approximately 79 % within four weeks. Using X-ray photoelectron spectroscopy (XPS), we confirmed the electron transfer from S. putrefaciens to the NCM622 cathode. Before the reaction, the oxidation states of the elements in the NCM622 were identified as Ni (III), Co (III), and Mn (IV). After the reaction, the metals were reduced to Ni (II), Co (II), and Mn (II/III), respectively, by the respiration of S. putrefaciens under anaerobic conditions. When S. putrefaciens respired under anaerobic conditions, electrons were transferred to the metals in the NCM622, and the metals in the NCM622 were reduced and subsequently dissolved (i.e., dissimilatory process). This study provided a new mechanism of bioleaching of valuable metals in spent LIBs under environmentally sustainable conditions through the dissimilatory process by S. putrefaciens. Furthermore, this technology could be expanded to advance microbial fuel cells (MFC), enabling the recycling of spent cathodes in LIBs while generating electricity.