Sodium Sulfate in the Li–Ion Battery Industry: Challenges, Opportunities, and Emerging Valorization Strategies

The rapid expansion of the lithium–ion battery (LIB) industry has resulted in a significant increase in sodium sulfate (Na 2 SO 4 ) generation, making it one of the most abundant inorganic byproducts across the entire battery value chain. Na 2 SO 4 is generated at multiple stages, during the lithium ore processing, the synthesis of nickel–manganese–cobalt (NMC) precursors, or upon the hydrometallurgical recycling of production scraps and end-of-life LIBs. This growing volume of Na 2 SO 4 presents serious environmental and economic challenges, particularly at the industrial scale, where wastewater management is becoming increasingly problematic. In this article, we first assess the origins and quantities of Na 2 SO 4 generated throughout the LIB lifecycle; then, we review current large-scale utilization practices and evaluate recent literature on emerging valorization strategies. While conventional reuse options remain limited, several approaches, including new developments and processes to reduce Na 2 SO 4 generation, upcycling of Na 2 SO 4 into higher-value products, or reintegrating it into the battery supply chain, appear to be promising and sustainable paths forward. Overall, this work underscores the urgency of addressing Na 2 SO 4 accumulation and outlines diverse valorization opportunities within and beyond the battery industry.