Selective Extraction of Lithium from Spent NMC Battery Cathodes Using Sodium Hydroxide as a Leaching Agent at Elevated Temperatures

Abstract

The demand for lithium-ion batteries (LIBs) is rapidly increasing due to the growth of the electronics and electric vehicle industries. Even though the batteries are rechargeable, their storage capacity decreases, and they eventually end up being wasted. Recycling the spent LIBs is necessary to reduce the environmental impact and utilize the precious metals contained in the waste The present work focuses on the selective recovery of lithium from the cathodes of spent NMC batteries through the hydrometallurgical process using a sodium hydroxide solution. The leaching process was carried out in 2 M and 4 M NaOH concentrations for 120 minutes at high pressure and at temperatures of 398.15 K, 423.15 K, 448.15 K, and 473.15 K. Experimental results showed that 56.53% of lithium could be recovered with nearly 100% selectivity under the optimum leaching conditions of 473.15 K and 4 M NaOH. The release of lithium ions was due to a combination of sodium adsorption, ion exchange, and impregnation mechanisms. Calculation results showed that the activation energy of the lithium leaching process was 2.1990×104 J/mol, the reaction was endothermic with enthalpy and entropy at standard conditions (298.15 K) of 4.8936×105 J/mol and 1.4421×103 J/mol/K, respectively. The present work also suggested that total lithium recovery can be increased through leaching processes.