Performance evaluation on recycling metals from lithium cobaltate by supercritical water combining with leaching-precipitation methods

The recycling of metals from spent lithium-ion batteries is currently a hotspot of research. This paper introduces a novel recovery method that integrates supercritical water and leaching-precipitation techniques to efficiently extract metals from lithium cobaltate electrodes. This study investigates the dissolution behavior of lithium cobaltate in supercritical water, and the interaction between lithium cobaltate and organic impurity (Polyvinylidene Fluoride and N-methylpyrrolidone) during the supercritical water treatment process. Lithium cobaltate reacts with supercritical water to form cobaltous hydroxide and reacts with polyvinylidene fluoride to form cobalt oxide. During the reaction of supercritical water with polyvinylidene fluoride and N-methylpyrrolidone in supercritical water, lithium cobaltate is reduced to cobalt oxide. The addition of N-methylpyrrolidone promotes the reduction of cobalt ion and the decomposition of polyvinylidene fluoride. Subsequently, the cathode materials treated with supercritical water are leached by using hydrochloric acid and sulfuric acid respectively. Cobalt and lithium ions in the leaching solution are precipitated by adding sodium hydroxide and sodium carbonate. The maximum recovery efficiencies of lithium and cobalt are 73 % and 79.60 %, respectively.