Recovery Of Cathode Materials From Spent Lithium-ion Batteries By Sulfation Roasting And Water Leaching Process

Different from the reduction roasting recovery process of valuable metal elements such as Li,Ni,Co and Mn from spent lithium-ion batteries,this paper proposed and studied a method for recovering valuable metals from spent lithium-ion batteries through a new process of“low temperature roasting-water leaching”.Li Ni_0.8Co_0.1Mn_0.1O₂ cathode material which was obtained from disassembling spent lithium-ion batteries mixed with NaHSO₄·H₂O and roasted together at different mixing rations,Li Ni_0.8Co_0.1Mn_0.1O₂ was gradually converted into part or all of water-soluble metal sulfuric acid double salt and recovered Li,Ni,Co and Mn elements.The roasted products were then subjected to water leaching experiments,detecting the content of Li,Ni,Co and Mn elements in the leachate,Calculating the leaching rate of elements,achieving selective and full recovery of valuable metal elements.In this paper,elements evolution and way of combination of roasted products of mixtures were studied,revealing the occurrence of elements and the mechanism of phases transition during roasting process,the mechanism of valuable metals recovery was explained theoretically.LiNi_0.8Co_0.1Mn_0.1O₂ can maintain thermodynamic stability in high temperature environment,but it thermodynamic stability was subjected to destroy when roasted with NaHSO₄·H₂O,the occurrence of Li,Ni,Co and Mn elements was changed.The mixture of Li Ni_0.8Co_0.1Mn_0.1O₂ and NaHSO₄·H₂O was roasted by different mass ration at 600?for 30min,the XRD results show that the removal of Li element from layer structure,which lead to structure destroyed gradually as the NaHSO₄·H₂O amount of addition increasing,and the structure was destroyed completely until the layered structure was destroyed completely,the occurrence of Li,Ni,Co and Mn elements was Li NaSO₄,Ni O and Co Mn₂O₄,respectively.Water leaching experiments further verified that only Li element was leached into the water solution and the recovery rate of Li element increased with the addition of NaHSO₄·H₂O at a lower mass ration.The leaching rate of Li element reached 96.6%,only a small amount of Ni,Co and Mn elements were leached into the solution at this time.Studying on selective separation of roasted products by the mass ration of stoichiometric1:1.40 of the mixture of Li Ni_0.8Co_0.1Mn_0.1O₂ and NaHSO₄·H₂O.At 175?,Li element was released from the layered structure preferentially,and generated Li₂SO₄,indicating that the layered structure was destroyed at this time.After continuing to increase the temperature,the layered structure Li Ni_0.8Co_0.1Mn_0.1O₂ was destroyed completely,and generated Na₂Ni(SO₄)₂,Ni O,Co Mn₂O₄,Li NaSO₄,Na₆Ni(SO₄)₄ under high temperature.After roasting,the raw materials of the spherical structure became smaller particles and sintered together,the sodium compounds and nickel compounds interacted distribution,and the distribution of nickel and oxygen was uniform in the washed slag.The valence state of the Ni and Co elements in the roasted products both became+2,and the valence states of the Mn element decreased from+4to+3.In order to achieve the full recovery of Li,Ni,Co and Mn elements,we continue to increase the amount of NaHSO₄·H₂O added to make all of them into water-soluble sulfates.The mixture was roasted at 600?for 30 min according to a certain proportion,and the roasted products were all Ni O,Li NaSO₄,Na₂Mn(SO₄)₂,Na₂Co(SO₄)₂,Na₂Ni(SO₄)₂ and Na₆Ni(SO₄)₄.When the mixture ration was 1:3.51,the phase composition was consistent with the roasted products of 1:2.11 and 1:2.81,but the characteristic peaks of Ni O have become very weak,indicating that Ni O was converted to Ni SO₄ at this ration.When the mixture ration was 1:4.21,the elements of Li,Ni,Co and Mn elements were transformed into corresponding water soluble bimetallic sulfates.ICP was used to determine the Li,Ni,Co and Mn content in the leach solution of the roasting products.It was found that the leaching rate of the elements increasing gradually as the mixture ration increased.When the mixture ration was 1:4.21,the leaching rate was reached maximum,the leaching rate of Li,Ni,Co and Mn elements was99.30%,99.64%,100%and 99.23%respectively,and achieving recovery of elements fully.The valence states of the Ni,Co and Mn were+2 in the roasting products when the mass ratio was 1:4.21 of the mixture of LiNi_0.8Co_0.1Mn_0.1O₂ and NaHSO₄·H₂O.