Research On Recovery Of Cobalt From Waste Lithium Cobalt Oxide Using Deep Eutectic Solvent

With the rapid development of China's society and economy,China has become a major battery consumer,and hundreds of millions of used lithium-ion batteries are produced every year.Therefore,the recycling of used lithium-ion batteries has become a social concern.Among them,the recycling of lithium cobalt oxide cathode materials is a key link in the recycling of waste lithium-ion batteries.Finding an environmentally friendly leaching agent to process waste lithium cobalt oxide cathode materials and recover valuable and scarce metal cobalt will help ease the tight supply and demand of cobalt resources.This paper attempts to use a new solvent-eutectic solvent to recover metal cobalt from waste lithium cobalt oxide.The matrix research is as follows:First,the response surface method was used to study the dissolution of LiCoO₂ in ChCl-EG DES.The optimal dissolution conditions are:temperature 160?,time 35.87h,stirring speed 500 r/min,and LiCoO₂ particle size 38?m.Electrospray mass spectrometry,Fourier infrared spectroscopy and ultraviolet absorption spectroscopy were used to analyze the existence form of cobalt ion in Ch Cl-EG DES,and the results showed that the existence form of cobalt ion in ChCl-EG DES was[Co Cl₄]^2-.In the measurement temperature range,the temperature has a significant effect on the viscosity and conductivity of LiCoO₂-Ch Cl-EG DES.With the increase of temperature,the viscosity decreases and the conductivity increases.The relationship between the two is inversely proportional,and the concentration of LiCoO₂ has an inverse relationship.The impact is not obvious.Secondly,through the study of electrochemical behavior,the cyclic voltammetry test showed that with the increase of temperature and LiCoO₂ concentration,the initial reduction potential will shift positively,which is beneficial to the progress of electrodeposition.Study the effect of deposition potential on the deposition product.When the deposition potential is-1.1?-1.4 V,only metallic cobalt can be deposited,and when the deposition potential is negative than-2.2 V,cobalt and lithium can be co-deposited,which can be recovered by controlling the deposition potential.Valuable metal in LiCoO₂.At the same time,the effects of different deposition potentials,deposition temperatures and LiCoO₂ concentrations on the morphology of cobalt coatings were studied.The coatings obtained at a deposition potential of-1.3 V,a deposition temperature of 120?,and a LiCoO₂ concentration of 2.0 g·L^-1 were the best.X-ray diffraction(XRD)analysis shows that the cobalt coating has an amorphous structure before heat treatment.And it is found that adding H₂C₂O₄·2H₂O to Ch Cl-EG DES can help the dissolution of LiCoO₂ in the solution to be increased,and the cobalt coating can be electrodeposited at a cell voltage of 2.6?3.0 V.Finally,the co-precipitation method was used to recover the valuable metal cobalt in LiCoO₂,and the dissolution amount of LiCoO₂ in Ch Cl-H₂C₂O₄·2H₂O-LiCoO₂ DES was studied.When the dissolution time is 36 h,the saturated solution at this temperature can be obtained.Co-precipitation experiments were carried out under different conditions.CoC₂O₄·2H₂O was obtained by stirring for 30 min at a precipitation temperature of 25?,and the recovery rate of cobalt was the highest.The calcination experiment was carried out under different conditions.The phase analysis showed that the Co₃O₄ calcined at 400? for 8 h has the highest recovery rate of cobalt,and is the best in terms of microscopic morphology and crystal structure.Under the above conditions,the recovery rate of cobalt was 96.1%.