Can black mass have a second life as an electrode material for desalination of brackish water via capacitive deionization?

“Black Mass” (BM) is the industry term that indicates the powdered material recovered from the spent Li-ion batteries (LIBs) after mechanical and thermal processing to remove binder, electrolytes, plastics and steel. In addition to graphite, it contains valuable metals, including cobalt, lithium, manganese, nickel and copper. Thus, recycling and reusing BM is of paramount importance to reduce the carbon footprint of the LIB supply chain and the need for virgin materials. Capacitive deionization (CDI), which utilizes carbon-based electrodes enriched with metal oxides, is a promising and sustainable technology for brackish water desalination. This article proposes, for the first time, the reuse of BM as an electrode material for CDI of brackish water. The proposal is based on the results of a feasibility study carried out on two different grades of BM, whose physiochemical properties are investigated by a combination of analytic techniques. The evaluation of their electrochemical performance in 0.1 mol L−1 NaCl solution by cyclic voltammetry shows that, at 5 mV s−1 scan rate, electrodes prepared with as-recovered BM exhibit specific capacitance (73−87 F g−1) comparable or superior to those obtained by using virgin materials. Therefore, regardless of the details of their processing, giving a second life to BM as a CDI electrode is a viable strategy to address the needs of the circular economy and sustainability of freshwater production.