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 LiNiO2 to metallic nickel has been reported, which is a typical cathode material of lithium-ion battery. In this paper, the electrochemical reduction behavior of LiNiO2 is studied at 750 °C in the eutectic NaCl-CaCl2 molten salt, and the constant cell voltage electrolysis of LiNiO2 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 LiNiO2 cathode is reduced to metallic nickel, with NiO and a small amount of Li0.4Ni1.6O2 detected inside the partially reduced cathode. After prolonging the electrolysis time to 12 h, LiNiO2 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.

Electrolytic reduction of Gd2O3-ZnO in NaCl-CaCl2 Molten Salt

“…However, due to the use of fluoride electrolyte or electrolysis of rare Earth chloride, problems such as environmental unfriendliness still exist. The FFC method, 20 as a modified molten salt electrolysis, can directly reduce oxides to metals in the chloride molten salts, and has two significant advantages: (i) it is performed under conditions below the metal melting point and molten salt decomposition voltage, so the energy consumption is relatively lower; 21,22 (ii) the oxide raw materials are easy to obtain and the metal or alloy can be reduced directly in situ. In recent studies of rare Earth alloys preparation, the presence of transition metals, such as Ni, Fe, and Co, could promote the reduction of rare Earth oxides through the ionization of O in the lattice.…”