Electrochemical recovery of Ni metallic in molten salts from spent lithium-ion battery

Abstract Massive deployment of lithium-ion battery inevitably causes a large amount of solid waste. To be sustainably implemented, technologies capable of reducing environmental impacts and recovering resources from spent lithium-ion battery have been an urgent task. The electrochemical reduction of LiNiO 2 to metallic nickel has been reported, which is a typical cathode material of lithium-ion battery. In this paper, the electrochemical reduction behavior of LiNiO 2 is studied at 750 °C in the eutectic NaCl-CaCl 2 molten salt, and the constant cell voltage electrolysis of LiNiO 2 is carried out. The results show that Ni(III) is reduced to metallic nickel by a two-step process, Ni(III) → Ni(II) → Ni, which is quasi-reversible controlled by diffusion and electron transfer. After electrolysis for 6 h at 1.4 V, the surface of LiNiO 2 cathode is reduced to metallic nickel, with NiO and a small amount of Li 0.4 Ni 1.6 O 2 detected inside the partially reduced cathode. After prolonging the electrolysis time to 12 h, LiNiO 2 is fully electroreduced to metallic nickel, achieving a high current efficiency of 98.60%. The present work highlights that molten salt electrolysis could be an effective protocol for reclamation of spent lithium-ion battery.