Study On Recover Metals From LiNi_1/3Co_1/3Mn_1/3O₂ By Sulfate Roasting And Water Leaching

In recent years,the market for new energy vehicles in China has developed rapidly and has promoted the rapid growth of upstream and downstream enterpri ses of the lithium ion battery industry chain.Because the new energy vehicle power lithium ion battery have generally service lifetimes of 3⁵ years.In the face of the upcoming scrapping tide of power lithium ion battery,it is urgent to establish a scrapped power lithium ion battery recycling system.The existing research work has systematically studied the properties and recovery technology of Li Ni_1/3Co_1/3Mn_1/3O₂ cathode material for power lithium ion battery in acidic aqueous solution,but the understanding of the properties of Li Ni_1/3Co_1/3Mn_1/3O₂ in other medium environment is insufficient.The thermal decomposition of Na HSO₄?H₂O,KHSO₄,Na₂S₂O₇ and K₂S₂O₇ was used to produce SO₃,and Li Ni_1/3Co_1/3Mn_1/3O₂ was placed in an atmosphere containing SO₃ gas for baking experiments in this paper.The chemical evolution rule and evolutionary control mechanism of Li Ni_1/3Co_1/3Mn_1/3O₂ in this sulfating roasting process was studied,and the recovery ratio of Li,Ni,Co and Mn in the roasted product was researched by water leaching.The cathode electrode materials Li Ni_1/3Co_1/3Mn_1/3O₂ was obtained by discharging-dismantling from spent power lithium ion battery.Then,the mass-heat change and the composition,morphology and the distribution characteristics of the elements about the roasted product of the mixtures which Li Ni _1/3Co_1/3Mn_1/3O₂ mixed uniformly with Na HSO₄·H₂O,KHSO₄,Na₂S₂O₇,K₂S₂O₇ with different molar ratios was studied by TG-DSC,XRD,SEM and EDS in the roasting process.The roasted product was subjected to a water leaching experiment to observe the change of the recovery rate between the different reactions.The results of the study show that:1.The thermodynamic behavior of the mixture is significantly different from that of a single positive electrode material Li Ni_1/3Co_1/3Mn_1/3O₂.The reaction temperature of Li Ni_1/3Co_1/3Mn_1/3O₂ mixed with sodium salt is significantly lower than the reaction temperature with the potassium salt mixture.The chemical conversion in mixtures was proceeded during the roasting process,and Li,Ni,Co and Mn elements are respectively present in the form of corresponding compound sulfate after roasting.The original spherical structure has completely disappeared,the main microstructural form of the roasting products is block type a nd dense structure,the distribution and shape of these particles is not uniform and irregular.The roasting product is leached by water,and the leaching rate is about 99%.In a comprehensive analysis,the recovery effect of sodium salt mixtures is better than potassium salt mixtures.2.Li Ni_1/3Co_1/3Mn_1/3O₂ was mixed with Na HSO₄·H₂O at different molar ratios for sulfation roasting experiments.By controlling the amount of Na HSO₄·H₂O in the mixed roasting process,the partial pressure of SO₃ in the reaction system can be controlled to control the extent of the reaction.When the ratio of Na HSO₄·H₂O was increased,the Li element from Li Ni_1/3Co_1/3Mn_1/3O₂ will be generated preferentially Li Na?SO₄?,the Mn and Co element will be reacted firstly to produce oxides and then converted to compound sulfates,the Ni element will be generated preferentially Ni O₄⁴⁺and then converted to compound sulfates,whereafter,it was just the conversion of compound sulfates in the roasting process.When the reaction ratio increases to 1:3,Li Ni_1/3Co_1/3Mn_1/3O₂ was converted completely to diffluent compound sulfates.Through the analysis of the morphology of the roasted products,it is found that the spherical structure of Li Ni _1/3Co_1/3Mn_1/3O₂ gradually reacts to form tiny particles.With the increasing of Na HSO₄·H₂O,the original spherical structure of Li Ni_1/3Co_1/3Mn_1/3O₂ was disappeared completely,a sintered phenomenon and cohesion of tiny particles were also observed.The further increasing of Na HSO ₄·H₂O,the agglomeration of particles was broken into irregular,pocket and small sizes.The roasted product of different reaction conditions was subjected to a water leaching experiment,the results showed that the recovery rate of Li Ni _1/3Co_1/3Mn_1/3O₂ was led to a sharp increase firstly,and then it tends to be gentle,and then a rapid increase stage,and the final recovery rate is increased to close to 100%.