Flotation Separation Of Electrode Materials From Waste Lithium-ion Batteries Based On Roasting Modification

Lithium-ion batteries contains rich metal elements and a variety of toxic substances,recycling waste lithium batteries can not only realize resource recycling,but also prevent environmental pollution.In this paper,the waste power batteries of Li Mn₂O₄ is taken as the research object,and the method of“roasting enhanced flotation”is used to solve the problem that the cathode and anode electrode materials are difficult to be separated by flotation in the process of recycling Li Mn₂O₄ batteries,namely by roasting to remove organic adhesive on the surface of the electrode materials,thereby increasing the electrode materials surface wettability difference,thus strengthen the flotation separation process.The main research conclusions are:（1）The research on the flotation behavior of single electrode materials of lithium-ion batteries shows that the flotation behavior of commercial Li Mn₂O₄ is opposite to that of commercial graphite,while the flotation behavior of waste Li Mn₂O₄ and waste graphite performs similar hydrophobic.During the flotation separation of the mixed electrode materials,the flotation separation efficiency of waste Li Mn₂O₄ and graphite is low,while that of commercial Li Mn₂O₄ and graphite is high.XRD,XPS,SEM,FT-IR and contact angle analysis shows that the surface of waste lithium battery electrode material is coated with organic compounds containing C,O,F and other elements,resulting in similar surface properties of anode and cathode electrode materials,and thus having similar flotation behavior,which finally increases the difficulty of flotation separation of anode and cathode electrode materials.（2）The thermal stability analysis of electrode materials shows that the decomposition temperature range of organic matter is 400-600℃.On the basis of fully mastering the surface properties of the electrode materials and the thermal stability of organics of the electrode materials,muffle furnace was used to explore the effect of roasting temperature and time on the removal of organic matter on the surface of the electrode materials.The results shows that after roasted at 550℃for 2h,the organics adhered to the surface can be fully oxidized and decomposed,then the original surface of electrode material can be exposed without changing the phase composition of the electrode material.XPS analysis results shows that the F functional groups on the surface of the electrode materials decreased from 40%to 6%after roasting;Contact angle analysis shows that the difference of contact angle between cathode and anode electrode materials increased from 4.4°to 22°after roasting.（3）The results of flotation separation experiments of electrode materials under different roasting parameters shown that the flotation separation efficiency of Li Mn₂O₄ and graphite after roasted at 550℃for2h was significantly better than that of untreated electrode materials.At this time,the grade of Li Mn₂O₄ in the flotation concentrate increased from63.10%to 90.98%.The residual amount of graphite in the small closed-circuit flotation concentrate is small,and the purity of Li Mn₂O₄ reaches 99%.