Research On The Recycling Of Graphite Anode Powder For Waste Lithium-ion Batteries

In recent years,with the rapid development of the new energy automobile industry,lithium-ion batteries in the product scrap cycle have also increased dramatically.At present,most of the lithium-ion battery recycling process focuses on the extraction and separation of valuable metals of cathode materials,but the negative electrode materials that account for 5%to 15%of the total cost of lithium-ion batteries are usually treated in the form of accumulation or high temperature incineration,which not only causes waste of resources,but also aggravates environmental pollution.Based on this,in order to realize the closed-chain recycling of the anode material of the waste lithium-ion battery,this paper uses the graphite anode powder of the waste lithium-ion phosphate battery as the raw material,and removes impurities such as iron,aluminum and copper by sulfuric acid leaching and pure water washing;then the gas phase oxidation roasting is used to further remove the fluorine-containing organic matter adhered to the graphite surface,and finally the phenolic resin is used as the coating material for coating modification.A systematic study of each key influencing factor was concluded as follows:The results of the sulfuric acid leaching-pure and water washing study showed that the graphite purity>99.5%,and the impurity removal rate>95%under the optimization conditions of H₂SO₄ concentration of 2.5mol/L,hydrogen peroxide dosage of 3 m L,leaching temperature of 95°C,liquid-solid ratio of 6:1 and washing temperature of 80°C,washing time of 40 min,and washing of 3 times.The results of the gas phase oxidation treatment show that the vapor phase oxidation method can remove the fluorine-containing organic matter adhering to the graphite surface,making the edge of the material more regular,which is conducive to improving the performance of the first charge and discharge.The first charge-discharge specific capacity of the graphite material obtained after treatment at 500°C and air atmosphere for3 h was 327.55 m Ah·g^-1 and 402.07 m Ah·g^-1,respectively,and the first round Coulomb efficiency was 81.47%.Using phenolic resin as the coating source,the liquid phase impregnation method is used to coat the gas phase oxide graphite.The results show that the materials prepared have the best electrochemical properties under the phenolic resin is 15%of the mass of graphite,the calcination temperature of 850°C and the calcination time G@C of 5 h:at the current density of 0.1C,the reversible capacity of the material cycle100 turns is 337.36 m Ah·g^-1,and the capacity retention rate is 93.48%;at the current density of 5 C,the specific capacity of the material G@C can still reach 135.40 m Ah·g^-1,which is 62.66%higher than that before the coating(83.24 m Ah·g^-1).There are 58 figures,18 tables,and 77 references in this thesis.