Li-ion battery recycling by energy-efficient, high-throughput Li2SO4 salt splitting in a diaphragm flow cell

Rapidly growing demand for lithium-ion batteries (LIBs) necessitates a significant expansion of LIB recycling to ensure adequate supply and avoid waste buildup. Traditional hydrometallurgical LIB recycling processes use super-stoichiometric quantities of acid and base and generate large volumes of salt waste that pose an environmental burden. Electrochemical regeneration of acid and base from salt offers a zero-waste alternative but faces challenges with respect to throughput and energy consumption, with current densities typically limited to ≤ 100 mA/cm2 and energy demands > 0.10 kWh/mol. These limitations stem from a reliance on ion exchange membranes (IEMs), which lead to high cell resistance. This study reports a hydrometallurgical process to recycle lithium cobalt oxide (LCO) and lithium nickel manganese cobalt oxide (NMC) cathodes using acid and base electrochemically generated from a Li2SO4 electrolyte. The electrochemical cell used contains no IEMs, enabling excellent energy efficiency between 0.033 and 0.097 kWh/mol at current densities up to 500 mA/cm2 and imparting a robust tolerance for impurities that typically foul IEMs. The produced acid and base are found to be competent for etching and recovering > 90% of the valuable metals from LIBs at industrially relevant pulp densities up to 66 g/L and are readily regenerated from the salt solution left at the end of the metal recovery process.