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.

Keywords

cathode recycling / circular economy / end-of-life batteries / energy transition / hydrometallurgy / organic acids leaching / sustainable resource recovery

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