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 (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.