Résumé
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 byproducts across the entire battery value chain. Na2SO4 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 Na2SO4 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 Na2SO4 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 Na2SO4 generation, upcycling of Na2SO4 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 Na2SO4 accumulation and outlines diverse valorization opportunities within and beyond the battery industry.