Recycle Of Cathode Material In Spent Lithium Ion Batteries Based On Novel Green Solvents

Lithium-ion batteries(LIB),as representatives of clean energy,are widely used in fields such as electric vehicles,large instruments,and electronic devices.Against the background of the global energy crisis and the "dual-carbon policy",the growing of retired LIB poses enormous environmental and economic pressures on modern society.Hydrometallurgy is the most common technical route for recycling valuable metals in the cathode materials of LIB,but traditional leaching solvents have many problems such as high energy consumption,poor performance,a large amount of waste liquid,and equipment corrosion.Based on the above reality,this article developed novel green solvents of guanidine hydrochloride-lactic acid and ethylene glycol-aluminum chloride to cleanly and efficiently dissolve lithium cobalt oxide(LCO)and lithium nickel cobalt manganese oxides(NCM),and explored the physical and chemical properties,with leaching mechanism to open up new hydrometallurgical paths for secondary resource recovery.The main research results are as follows:1.Under the premise of analyzing the metal composition and crystal structure of LCO,four deep eutectic solvents were designed,and a clean and efficient low-melting solvent,guanidine hydrochloride-lactic acid,was selected.GUC-LAC could dissolve Li 61.09%,Co 34.72%from LCO in 24 h,at 50℃ with solid-liquid ratio of 1/50.The dissolution ratios of Li and three other transition metals of NCM could reach more than 80%.After filtration,washing,drying and calcination,the stripping products by oxalic acid turned to highly pure Co3O4,which could be directly reused in the manufacture of cathode materials.2.The dissolution performance of deep eutectic solvents was enhanced by ascorbic acid.The solvent increased the LCO dissolution ratio to Li 97.42%,Co 96.91%in 24 h,at 50℃ and solid-liquid ratio of 1/50,respectively.Through stripping of oxalic acid and supplement of ascorbic acid,guanidine hydrochloride-lactic acid could be used at least three times and maintain dissolution performance,which greatly reduced the use of solvents.The relationship between solvent compositions and dissolution performance was established by 1H-NMR,UV-vis of the transition metal state and coordination environment,and Hammett acidity and cyclic voltammetry of the solvent physical and chemical properties.3.Nine inorganic salt-ethylene glycol solvents were developed,and the effects of different factors such as inorganic salt cations,anions,crystalline water,and dissolution rates were investigated.A simple,easily obtainable,suitable viscosity,and superior performance ethylene glycol-aluminum chloride solvent was screened.The solvent could load Li 3506 ppm and Co 22858 ppm for one time,in 6 h,and at 90℃.The solvent could also enhance the performance with a small amount of H2O2 at 50℃,maintaining the same properties as the dissolution ratio of 90℃.The solvent structures and metal states were analyzed by 1H-NMR,FT-IR,and UV-vis,and the leaching mechanism of the solvent on LCO was analyzed by FT-IR and GC-MS,and to explain the origin of acidity and reducibility.