Sustainable Strategies for the Recycling of Sodium‐Ion Battery Cathodes Using Organic Acids

ABSTRACT As the global demand for energy storage grows, sodium‐ion batteries (SIBs) are emerging as a cost‐effective and resource‐abundant alternative to lithium‐ion batteries (LIBs). However, despite their increasing deployment, efficient end‐of‐life recycling strategies for SIBs remain underdeveloped. In this work, a novel two‐step hydrometallurgical process is presented for recovering critical metals from spent SIB cathodes. The first step employs mild citric acid leaching, achieving recovery efficiencies above 95% for nickel (Ni), manganese (Mn), sodium (Na), and iron (Fe). This performance not only demonstrates the effectiveness of citric acid as a biodegradable leaching agent but also fulfils forthcoming European Union requirements, which mandate 90% Ni recovery by 2027 and 95% by 2031. In the second step, selective precipitation with oxalic acid enables targeted recovery of Ni and Mn, with precipitation yields exceeding 95%. The resulting Mn‐Ni mixed oxalate is a promising precursor for resynthesizing Na‐Ni‐Fe‐Mn cathodes or other advanced applications. Overall, this integrated method introduces an environmental and closed‐loop recycling route that advances circular economy principles and supports the sustainable transition from LIBs to next‐generation SIB technologies.