Valorization Pathways for Sodium Sulfate: Addressing One of the Most Abundant By-Products of the Battery Industry

The rapid expansion of the lithium-ion battery (LIB) industry has resulted in a significant increase in sodium sulfate (Na2SO4) generation, making it one of the most abundant inorganic by-products across the entire battery value chain. Na2SO4 is formed at multiple stages, going from lithium ore processing, the synthesis of nickel-manganese-cobalt (NMC) precursors to the hydrometallurgical recycling of production scraps and end-of-life LIBs. This growing volume of Na2SO4 presents serious environmental and economic challenges at the industrial scale, such as wastewater management issues. In this perspective article, we first assess the origins and quantities of Na2SO4 produced throughout the LIB lifecycle, then, review current large-scale utilization practices and evaluate recent literature on emerging valorization strategies. While current conventional reuse options remain limited, several approaches including new developments to reduce Na2SO4 generation, upcycling of Na2SO4 or reintegrating it into the battery supply chain appear to be promising and sustainable paths forward. Overall, this work underscores the urgency of addressing Na2SO4 accumulation and outlines diverse valorization opportunities within and beyond the battery sector.