Abstract:

A hydrometallurgical process for the recovery of cobalt oxalate from spent lithium-ion batteries was used to recycle cobalt compound by using alkali leaching, reductive acid leaching and chemical deposition of cobalt oxalate. The recycled cobalt oxalate was used to synthesize nano-Co₃O₄ anode material by sol-gel method. The samples were characterized by thermal gravity analysis and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and charge/discharge measurements. The influence of molar ratio of Co²⁺ to citric acid and calcination temperature on the structure and electrochemical performance of nano-Co₃O₄ was evaluated. As the molar ratio of Co²⁺ to citric acid is 1:1, the face-centered cubic (fcc) Co₃O₄ powder shows the discharge capacity of 760.9 mA h g^-1, the high coulombic efficiency of 99.7% in the first cycle at the current density of 125 mA g^-1, and the excellent cycling performance with the reversible capacity of 442.3 mA h g^-1 after 20 cycles at the current density of 250 mA g^-1.

Key words: Spent lithium-ion batteries, Sol-gel method, Reductive acid leaching, Nanostructure cobalt oxide, Electrochemical behavior