Research On Dissolution Separation And Metal Leaching Of Cathode Materials From Spent Lithium-Ion Batteries

With the widespread application of lithium-ion batteries in electric vehicles,mobile electronic devices,etc.,the number of spent lithium-ion batteries has also increased sharply,and its recycling has become an urgent issue.Spent lithium-ion batteries contain a large amount of strategic metals such as lithium,cobalt,and manganese,which have extremely high recycling value.In addition,it contains many harmful compounds,which will cause serious harm to the environment if it is not treated in a timely and standardized manner.In this paper,the spent lithium cobalt oxide battery was taken as the research object,and the dissolution and separation of cathode material particles and metal leaching were studied by using deep eutectic solvent（DES）.The influence of dissolution parameters and leaching conditions on dissociation efficiency and leaching rate,using SEM-EDS,XRD,FTIR to characterize the cathode material and DES solution before and after dissociation,and analyze the microscopic morphology and crystal structure before and after the reaction and the change of functional groups,explored the mechanism of DES dissolution and separation and metal leaching kinetics,and formed a new recycling method for spent lithium-ion batteries.First,use choline chloride and xylitol to prepare a DES solution with a mass concentration of 70%,and conduct a dissolution and separation study on the cathode electrode sheet obtained by manual disassembly.The results show that,under stirring conditions,choline chloride:xylitol The highest dissociation efficiency of 94.92%can be achieved under the conditions of molar ratio of 2:1,dissociation time of 20 min,dissociation temperature of 140℃,and solid-liquid ratio of 16 g/L.Through SEM-EDS analysis,it is found that the surface of the cathode electrode material is smooth and complete after dissociation,and there is basically no residue on the surface of the aluminum foil;XRD analysis shows that the crystal structure of the cathode material has not changed,and DES will not damage the cathode material;FTIR analysis shows that,The hydrogen bond donor in DES destroys the molecular structure of the binder（PVDF）in the cathode electrode,thereby achieving a dissociation effect,which provides good conditions for the subsequent leaching or regeneration of the cathode material.In order to explore the recycling performance of DES,the dissociation efficiency of DES to the cathode material was investigated under the optimal condition of solvent separation of the cathode electrode for five cycles.The results showed that the dissociation efficiency gradually decreased with the increase of the number of cycles.The dissociation efficiency at the time of use is 91.89%,and the dissociation efficiency will reach 67.96%at the fifth use.As the number of cycles increases,SEM analysis shows that the agglomeration of cathode material particles is gradually obvious,and the number of cathode particles adhered to the surface of aluminum foil gradually increases.FTIR analysis shows that the hydrogen bond energy in DES is weakened.Finally,the dissociation effect of the first use can be achieved by adding new solution,thereby reducing the cost of DES dissociation of the cathode electrode of the spent lithium-ion battery.Choline chloride and citric acid were used to configure DES with a concentration of 70%to leach the cathode material after dissociation,and the influence of each parameter on metal leaching was analyzed.The experimental results show that:when choline chloride:citric acid=2:1;leaching time 60 min;leaching temperature 80°C;solid-liquid ratio 20 g/L,the leaching rates of Co and Li are the highest.Up to 94.26%and 96.98%.The study of leaching kinetics found that the leaching reactions of Co and Li are controlled by diffusion and the mixing of surface chemical reactions.-1.According to the activation energy of the two metals,Li is easier to leach than Co.Finally,the separation and recovery of two valuable metals is realized,and high-purity metal oxides are obtained.The research of this paper lays the foundation for the application of DES in the dissolution and separation of cathode electrode materials of spent lithium-ion batteries and the leaching of metals,and provides a new and effective method for the green recycling of spent lithium-ion batteries,which has a good application prospect.Choline chloride and citric acid were used to configure DES with a concentration of 70%to leach the cathode electrode material after dissociation,and the influence of each parameter on metal leaching was analyzed.The experimental results show that:when choline chloride:citric acid=2:1;leaching time 60 min;leaching temperature80°C;solid-liquid ratio 20 g/L,the leaching rates of Co and Li are the highest.Up to94.26%and 96.98%.The leaching kinetics showed that the leaching reactions of Co and Li were controlled by diffusion control and surface chemical reaction mixing,and the activation energies of the two valuable metals were determined to be 17.40 k J·mol^-1and 15.77 k J·mol^-1,respectively.According to the activation energy of the two metals,Li is easier to leach than Co.Finally,the separation and recovery of two valuable metals is realized,and high-purity metal oxides are obtained.The research of this thesis lays the foundation for the application of DES in the dissolution and separation of cathode materials of spent lithium-ion batteries and the leaching of metals,and provides a new and effective method for the green recycling of spent lithium-ion batteries,which has a good application prospect.This thesis has 49 pictures,7 tables,and 105 references.