Methods for processing battery black powder and producing recycled graphite anodes and their applications

Abstract

This invention discloses a method for processing battery black powder and producing recycled graphite anodes, and its application. Waste battery fragments are immersed in an impregnation solution, and the solid material obtained through solid-liquid separation is dried. The dried material is mixed with molten salt, heated to react, and sieved to obtain molten salt slurry (undersize) and copper / aluminum foil (oversize). The molten salt slurry undergoes solid-liquid separation to obtain molten salt and black powder. The black powder is mixed with acid and a reducing agent for leaching. The leaching residue is then subjected to anaerobic calcination to obtain a recycled graphite anode. This invention employs a combined process of antioxidant impregnation and molten salt pyrolysis to recover high-value copper foil, aluminum foil, and black powder. Further processing of the black powder yields a recycled graphite anode with good electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of battery recycling technology, specifically relating to a method for processing battery black powder and producing recycled graphite negative electrodes and its application. Background Technology

[0002] Lithium-ion batteries consist of a casing and internal cells. The casing can be made of stainless steel, nickel-plated metal, or plastic. The internal cells have a spiral structure and mainly consist of a positive electrode, a negative electrode, a separator, and an electrolyte. Generally, the positive electrode material consists of approximately 90% lithium cobalt oxide and other active materials, 7%-8% acetylene black conductive agent, and 3%-4% organic binder, uniformly mixed and coated onto an aluminum foil current collector approximately 20 μm thick. The negative electrode consists of approximately 90% carbon material as the negative electrode active material, 4%-5% acetylene black conductive agent, and 6%-7% binder, uniformly mixed and coated onto a copper foil current collector 15 μm thick. The thickness of the positive and negative electrodes is approximately 0.18-0.20 mm, separated by a separator approximately 10 μm thick. The electrolyte consists of an electrolyte and an organic solvent; the electrolyte is generally a lithium salt organic solvent. The main component of the positive electrode binder is polyvinylidene fluoride (PVDF).

[0003] Currently, the recycling process for spent power batteries mainly includes three steps: pretreatment, secondary treatment of electrode materials, and deep recycling. Because the binder is uniformly adhered to the surface of the electrode materials, it needs to be pyrolyzed at temperatures above 600℃ to remove the binder. Then, acid and alkali leaching is used to recover precious metals such as Co, Ni, Mn, and Li from the positive electrode material. However, the graphite in the negative electrode material is not recovered, resulting in a significant waste of graphite. During pyrolysis, at high temperatures, the negative electrode graphite undergoes a redox reaction with the positive electrode material. The graphite is oxidized, and its particle structure is damaged. Therefore, in subsequent recycling and regeneration of the graphite negative electrode, the amount of graphite recovered is small, and the electrochemical performance of the recovered graphite is significantly reduced. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a method for processing battery black powder and producing a recycled graphite anode and its application. By adding an antioxidant, the graphite is protected to avoid oxidation, and low-temperature molten salt pyrolysis of PVDF is used to recover the copper and aluminum foil therein, thus preparing a recycled graphite anode with good electrochemical performance.

[0005] According to one aspect of the present invention, a method for processing battery black powder and producing a recycled graphite negative electrode is provided, comprising the following steps:

[0006] S1: Waste lithium-ion batteries are discharged, disassembled and crushed to obtain crushed material. The crushed material is then soaked in an impregnation solution, which is one or both of phosphate solution and borate solution.

[0007] S2: The soaked material is subjected to solid-liquid separation, and the resulting solid material is dried to obtain dried material;

[0008] S3: Mix the dried material with molten salt, heat to 310-350℃ to react, and then sieve at the heating temperature to obtain molten salt slurry as undersize and copper-aluminum foil as oversize. The molten salt is at least one of potassium nitrate or sodium nitrate.

[0009] S4: The molten salt slurry under the sieve is subjected to solid-liquid separation at the heating temperature described in step S3 to obtain molten salt and black powder;

[0010] S5: The black powder is mixed with acid and reducing agent to carry out a leaching reaction. Solid-liquid separation is performed to obtain leaching solution and leaching residue. The leaching residue is then subjected to oxygen-free calcination to obtain a regenerated graphite negative electrode.

[0011] In some embodiments of the present invention, in step S1, the waste lithium-ion battery is at least one of ternary lithium-ion battery, lithium cobalt oxide battery, lithium manganese oxide battery or lithium nickel oxide battery.

[0012] In some embodiments of the present invention, in step S1, the particle size of the crushed material is ≤5cm.

[0013] In some embodiments of the present invention, in step S1, the solid-liquid ratio of the crushed material to the impregnation liquid is 0.2-1.0 g / mL, and the impregnation liquid is a phosphate solution with a concentration of 0.2-0.5 g / mL and / or a borate solution with a concentration of 0.2-0.5 g / mL.

[0014] In some embodiments of the present invention, in step S1, the phosphate solution is at least one of potassium dihydrogen phosphate solution or sodium dihydrogen phosphate solution; the borate solution is at least one of potassium tetraborate solution or sodium tetraborate solution.

[0015] In some embodiments of the present invention, in step S1, the soaking temperature is 60-75°C and the soaking time is 2.0-3.0h.

[0016] In some embodiments of the present invention, in step S2, the drying temperature is 100-120°C and the drying time is 1-2 hours.

[0017] In some embodiments of the present invention, in step S3, the mass ratio of the dried material to the molten salt is 1:(1.5-3.0).

[0018] In some embodiments of the present invention, the reaction time in step S3 is 1-2 hours.

[0019] In some embodiments of the present invention, in step S3, the mesh size of the sieve used for screening is 2-3 mm.

[0020] In some embodiments of the present invention, in step S5, the solid-liquid ratio of the black powder to the acid solution is 1.0 g / (3.0-5.0) mL, and the concentration of the acid solution is 0.1-1 mol / L.

[0021] In some embodiments of the present invention, in step S5, the acid solution is at least one of sulfuric acid, hydrochloric acid, or nitric acid.

[0022] In some embodiments of the present invention, in step S5, the reducing agent is at least one of hydrogen peroxide, sodium sulfite, or ascorbic acid.

[0023] In some embodiments of the present invention, in step S5, the leaching reaction temperature is 40-80°C. Further, the leaching reaction time is 1-3 hours.

[0024] In some embodiments of the present invention, in step S5, the temperature of the oxygen-free calcination is 700-900°C. Further, the time of the oxygen-free calcination is 1-3 hours.

[0025] The present invention also provides the application of the recycled graphite anode prepared by the method in lithium-ion batteries.

[0026] According to a preferred embodiment of the present invention, at least the following beneficial effects are achieved:

[0027] 1. This invention employs a combined process of anti-oxidation impregnation and molten salt pyrolysis to recover high-value copper foil, aluminum foil, and black powder. Further processing of the black powder yields recycled graphite anodes with good electrochemical performance. This method not only solves the problem of difficult graphite regeneration but also avoids safety hazards and large-scale oxidation of copper and aluminum in spent lithium-ion batteries at high pyrolysis temperatures.

[0028] 2. First, the waste lithium batteries are crushed and immersed in an impregnation solution to form an antioxidant coating on the internal pores and surface of the waste graphite negative electrode. During molten salt pyrolysis, the antioxidant layer is transformed into high-temperature resistant compounds, such as borates being transformed into high-temperature resistant oxides B2O3, and phosphates being transformed into highly thermally stable metaphosphates or polyphosphates. At the molten salt temperature, the binder on the positive electrode sheet is decomposed and carbonized on one hand, and oxidized and decomposed by the molten salt on the other hand, causing the positive electrode material to detach from the aluminum foil. At the same time, the strong oxidizing property of the molten salt causes a dense oxide film to form on the surface of the aluminum foil, protecting the aluminum foil from further oxidation. Finally, the resulting black powder is leached with acid to remove metal ions while carrying away the antioxidant layer, resulting in graphite leaching residue. The entire process protects the graphite, and the resulting regenerated graphite negative electrode has good electrochemical performance during subsequent graphitization regeneration. Attached Figure Description

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0030] Figure 1 This is a process flow diagram of Embodiment 1 of the present invention. Detailed Implementation

[0031] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for processing battery black powder and producing recycled graphite anodes, referring to Figure 1 The specific process is as follows:

[0034] Step 1: After being discharged and disassembled, the waste ternary lithium-ion batteries are crushed into crushed material with a particle size of less than 5cm.

[0035] Step 2: Soak the crushed material in the impregnation solution for 3.0 h at a solid-liquid ratio of 0.2 g / mL. The impregnation solution is a mixed solution of potassium dihydrogen phosphate with a concentration of 0.5 g / mL and potassium tetraborate with a concentration of 0.5 g / mL, and the soaking temperature is 60℃.

[0036] Step 3: Filter the soaked material by pressure and dry it at 100℃ for 2 hours to obtain dried material;

[0037] Step 4: Mix the dried material with sodium nitrate at a mass ratio of 1:1.5, and heat to 310℃, then keep warm for 1-2 hours;

[0038] Step 5: At the temperature described in Step 4, the mixture is sieved through a nickel screen with a aperture of 0.25 mm to obtain molten salt slurry as the undersize and copper-aluminum foil as the oversize.

[0039] Step 6: At the temperature described in step 4, the molten salt slurry under the sieve is centrifuged to obtain molten salt and black powder;

[0040] Step 7: Add the black powder to sulfuric acid with a concentration of 1 mol / L according to the solid-liquid ratio of 1.0 g / 3.0 mL, add hydrogen peroxide, and leach at a temperature of 80℃ for 1 hour.

[0041] Step 8: Solid-liquid separation to obtain leachate and leachate residue;

[0042] Step 9: Wash the leaching residue, dry it, and then calcine it at 700℃ in the absence of oxygen for 3 hours to obtain the regenerated graphite anode.

[0043] Example 2

[0044] A method for processing battery black powder and producing recycled graphite anodes, the specific process is as follows:

[0045] Step 1: After being discharged and dismantled, the waste lithium cobalt oxide batteries are crushed into crushed material with a particle size of less than 5cm.

[0046] Step 2: Soak the crushed material in the impregnation solution for 2.5 hours at a solid-liquid ratio of 0.5 g / mL. The impregnation solution is a mixed solution of sodium dihydrogen phosphate with a concentration of 0.3 g / mL and sodium tetraborate with a concentration of 0.3 g / mL, and the soaking temperature is 65℃.

[0047] Step 3: Filter the soaked material by pressure and dry it at 110℃ for 1.5 hours to obtain dried material;

[0048] Step 4: Mix the dried material with sodium nitrate at a mass ratio of 1:2.0, and heat to 330℃, then keep warm for 1.5 hours;

[0049] Step 5: At the temperature described in Step 4, the mixture is sieved through a nickel screen with a aperture of 0.25 mm to obtain molten salt slurry as the undersize and copper-aluminum foil as the oversize.

[0050] Step 6: At the temperature described in step 4, the molten salt slurry under the sieve is centrifuged to obtain molten salt and black powder;

[0051] Step 7: Add the black powder to hydrochloric acid with a concentration of 0.5 mol / L at a solid-liquid ratio of 1.0 g / 4.0 mL, add sodium sulfite, and leach at a temperature of 60 °C for 2 h.

[0052] Step 8: Solid-liquid separation to obtain leachate and leachate residue;

[0053] Step 9: Wash the leaching residue, dry it, and then calcine it at 800℃ in the absence of oxygen for 2 hours to obtain the regenerated graphite anode.

[0054] Example 3

[0055] A method for processing battery black powder and producing recycled graphite anodes, the specific process of which is as follows:

[0056] Step 1: After being discharged and disassembled, the waste ternary lithium-ion batteries are crushed into crushed material with a particle size of less than 5cm.

[0057] Step 2: Soak the crushed material in the impregnation solution for 2.0 h at a solid-liquid ratio of 1.0 g / mL. The impregnation solution is a mixed solution of sodium dihydrogen phosphate with a concentration of 0.2 g / mL and sodium tetraborate with a concentration of 0.2 g / mL, and the soaking temperature is 75 °C.

[0058] Step 3: Filter the soaked material by pressure and dry it at 120℃ for 1 hour to obtain dried material;

[0059] Step 4: Mix the dried material with potassium nitrate at a mass ratio of 1:3.0, and heat to 350℃, then keep warm for 1 hour;

[0060] Step 5: At the temperature described in Step 4, the mixture is sieved through a nickel screen with a aperture of 0.25 mm to obtain molten salt slurry as the undersize and copper-aluminum foil as the oversize.

[0061] Step 6: At the temperature described in step 4, the molten salt slurry under the sieve is centrifuged to obtain molten salt and black powder;

[0062] Step 7: Add the black powder to 0.1 mol / L nitric acid at a solid-liquid ratio of 1.0 g / 5.0 mL, add ascorbic acid, and leach at 80°C for 1 hour.

[0063] Step 8: Solid-liquid separation to obtain leachate and leachate residue;

[0064] Step 9: Wash the leaching residue, dry it, and then calcine it at 900℃ in the absence of oxygen for 1 hour to obtain the regenerated graphite anode.

[0065] Comparative Example 1

[0066] A method for processing battery black powder and producing recycled graphite negative electrodes differs from Example 1 in that it does not use an impregnation solution. The specific process is as follows:

[0067] Step 1: After being discharged and disassembled, the waste ternary lithium-ion batteries are crushed into crushed material with a particle size of less than 5cm.

[0068] Step 2: Mix the crushed material with sodium nitrate at a mass ratio of 1:1.5, and heat to 310℃, then keep warm for 1-2 hours;

[0069] Step 3: At the temperature described in Step 2, the mixture is sieved through a nickel screen with a aperture of 0.25 mm to obtain molten salt slurry as the undersize and copper-aluminum foil as the oversize.

[0070] Step 4: At the temperature described in Step 2, the molten salt slurry under the sieve is centrifuged to obtain molten salt and black powder;

[0071] Step 5: Add the black powder to sulfuric acid with a concentration of 1 mol / L according to the solid-liquid ratio of 1.0 g / 3.0 mL, add hydrogen peroxide, and leach at a temperature of 80℃ for 1 hour.

[0072] Step 6: Solid-liquid separation to obtain leachate and leachate residue;

[0073] Step 7: Wash the leaching residue, dry it, and then calcine it at 700℃ in the absence of oxygen for 3 hours to obtain the regenerated graphite anode.

[0074] Comparative Example 2

[0075] A method for processing battery black powder and producing recycled graphite negative electrodes differs from Example 2 in that it does not use an impregnation solution. The specific process is as follows:

[0076] Step 1: After being discharged and dismantled, the waste lithium cobalt oxide batteries are crushed into crushed material with a particle size of less than 5cm.

[0077] Step 2: Mix the crushed material with sodium nitrate at a mass ratio of 1:2.0, and heat to 330℃, then keep at that temperature for 1.5 hours.

[0078] Step 3: At the temperature described in Step 2, the mixture is sieved through a nickel screen with a aperture of 0.25 mm to obtain molten salt slurry as the undersize and copper-aluminum foil as the oversize.

[0079] Step 4: At the temperature described in Step 2, the molten salt slurry under the sieve is centrifuged to obtain molten salt and black powder;

[0080] Step 5: Add the black powder to hydrochloric acid with a concentration of 0.5 mol / L at a solid-liquid ratio of 1.0 g / 4.0 mL, add sodium sulfite, and leach at a temperature of 60 °C for 2 hours.

[0081] Step 6: Solid-liquid separation to obtain leachate and leachate residue;

[0082] Step 7: Wash the leaching residue, dry it, and then calcine it at 800℃ in the absence of oxygen for 2 hours to obtain the regenerated graphite anode.

[0083] Comparative Example 3

[0084] A method for processing battery black powder and producing recycled graphite negative electrodes differs from Example 3 in that it does not use an impregnation solution. The specific process is as follows:

[0085] Step 1: After being discharged and disassembled, the waste ternary lithium-ion batteries are crushed into crushed material with a particle size of less than 5cm.

[0086] Step 2: Mix the crushed material with potassium nitrate at a mass ratio of 1:3.0, and heat to 350℃, then keep warm for 1 hour;

[0087] Step 3: At the temperature described in Step 2, the mixture is sieved through a nickel screen with a aperture of 0.25 mm to obtain molten salt slurry as the undersize and copper-aluminum foil as the oversize.

[0088] Step 4: At the temperature described in Step 2, the molten salt slurry under the sieve is centrifuged to obtain molten salt and black powder;

[0089] Step 5: Add the black powder to 0.1 mol / L nitric acid at a solid-liquid ratio of 1.0 g / 5.0 mL, add ascorbic acid, and leach at 80°C for 1 hour.

[0090] Step 6: Solid-liquid separation to obtain leachate and leachate residue;

[0091] Step 7: Wash the leaching residue, dry it, and then calcine it at 900℃ in the absence of oxygen for 1 hour to obtain the regenerated graphite anode.

[0092] Comparative Example 4

[0093] A method for processing battery black powder and producing recycled graphite anodes differs from Example 1 in that it does not use molten salt mixing but directly performs low-temperature pyrolysis. The specific process is as follows:

[0094] Step 1: After being discharged and disassembled, the waste ternary lithium-ion batteries are crushed into crushed material with a particle size of less than 5cm.

[0095] Step 2: Soak the crushed material in the impregnation solution for 3.0 h at a solid-liquid ratio of 0.2 g / mL. The impregnation solution is a mixed solution of potassium dihydrogen phosphate with a concentration of 0.5 g / mL and potassium tetraborate with a concentration of 0.5 g / mL, and the soaking temperature is 60℃.

[0096] Step 3: Filter the soaked material by pressure and dry it at 100℃ for 2 hours to obtain dried material;

[0097] Step 4: Pyrolyze the dried material at 310℃ and keep it at that temperature for 1-2 hours;

[0098] Step 5: At the temperature described in Step 4, the pyrolysis material is sieved through a nickel sieve with a aperture of 0.25 mm to obtain black powder as the undersize and copper-aluminum foil as the oversize.

[0099] Step 6: Add the black powder to sulfuric acid with a concentration of 1 mol / L according to the solid-liquid ratio of 1.0 g / 3.0 mL, add hydrogen peroxide, and leach at a temperature of 80℃ for 1 hour.

[0100] Step 7: Solid-liquid separation to obtain leachate and leachate residue;

[0101] Step 8: Wash the leaching residue, dry it, and then calcine it at 700℃ in the absence of oxygen for 3 hours to obtain the regenerated graphite anode.

[0102] Comparative Example 5

[0103] A method for processing battery black powder and producing recycled graphite anodes differs from Example 2 in that it does not use molten salt mixing but directly performs low-temperature pyrolysis. The specific process is as follows:

[0104] Step 1: After being discharged and dismantled, the waste lithium cobalt oxide batteries are crushed into crushed material with a particle size of less than 5cm.

[0105] Step 2: Soak the crushed material in the impregnation solution for 2.5 hours at a solid-liquid ratio of 0.5 g / mL. The impregnation solution is a mixed solution of sodium dihydrogen phosphate with a concentration of 0.3 g / mL and sodium tetraborate with a concentration of 0.3 g / mL, and the soaking temperature is 65℃.

[0106] Step 3: Filter the soaked material by pressure and dry it at 110℃ for 1.5 hours to obtain dried material;

[0107] Step 4: Pyrolyze the dried material at 330℃ and keep it at that temperature for 1.5 hours;

[0108] Step 5: At the temperature described in Step 4, the pyrolysis material is sieved through a nickel sieve with a aperture of 0.25 mm to obtain black powder as the undersize and copper-aluminum foil as the oversize.

[0109] Step 6: Add the black powder to hydrochloric acid with a concentration of 0.5 mol / L at a solid-liquid ratio of 1.0 g / 4.0 mL, add sodium sulfite, and leach at a temperature of 60 °C for 2 hours.

[0110] Step 7: Solid-liquid separation to obtain leachate and leachate residue;

[0111] Step 8: Wash the leaching residue, dry it, and then calcine it at 800℃ in the absence of oxygen for 2 hours to obtain the regenerated graphite anode.

[0112] Comparative Example 6

[0113] A method for processing battery black powder and producing recycled graphite anodes differs from Example 3 in that it does not use molten salt mixing but directly performs low-temperature pyrolysis. The specific process is as follows:

[0114] Step 1: After being discharged and disassembled, the waste ternary lithium-ion batteries are crushed into crushed material with a particle size of less than 5cm.

[0115] Step 2: Soak the crushed material in the impregnation solution for 2.0 h at a solid-liquid ratio of 1.0 g / mL. The impregnation solution is a mixed solution of sodium dihydrogen phosphate with a concentration of 0.2 g / mL and sodium tetraborate with a concentration of 0.2 g / mL, and the soaking temperature is 75 °C.

[0116] Step 3: Filter the soaked material by pressure and dry it at 120℃ for 1 hour to obtain dried material;

[0117] Step 4: Pyrolyze the dried material at 350℃ and keep it at that temperature for 1 hour;

[0118] Step 5: At the temperature described in Step 4, the pyrolysis material is sieved through a nickel sieve with a aperture of 0.25 mm to obtain black powder as the undersize and copper-aluminum foil as the oversize.

[0119] Step 6: Add the black powder to 0.1 mol / L nitric acid at a solid-liquid ratio of 1.0 g / 5.0 mL, add ascorbic acid, and leach at 80 °C for 1 h.

[0120] Step 7: Solid-liquid separation to obtain leachate and leachate residue;

[0121] Step 8: Wash the leaching residue, dry it, and then calcine it at 900℃ in the absence of oxygen for 1 hour to obtain the regenerated graphite anode.

[0122] Comparative Example 7

[0123] A method for processing battery black powder and producing recycled graphite anodes differs from Example 1 in that it directly pyrolyzes the crushed material at high temperature. The specific process is as follows:

[0124] Step 1: After being discharged and disassembled, the waste ternary lithium-ion batteries are crushed into crushed material with a particle size of less than 5cm.

[0125] Step 2: Pyrolyze the crushed material at 500℃ for 2 hours, and then sieve it through a sieve with a pore size of 0.25mm to obtain black powder as the undersize and copper-aluminum foil as the oversize.

[0126] Step 7: Add the black powder to sulfuric acid with a concentration of 1 mol / L according to the solid-liquid ratio of 1.0 g / 3.0 mL, add hydrogen peroxide, and leach at a temperature of 80℃ for 1 hour.

[0127] Step 8: Solid-liquid separation to obtain leachate and leachate residue;

[0128] Step 9: Wash the leaching residue, dry it, and then calcine it at 700℃ in the absence of oxygen for 3 hours to obtain the regenerated graphite anode.

[0129] The black powder obtained in Examples 1-3 and Comparative Examples 1-7 was tested, and the results are shown in Table 1.

[0130] Table 1

[0131]

[0132] As shown in Table 1, in Comparative Examples 1-3, the carbon content in the black powder was low, indicating that the carbon was oxidized during pyrolysis, resulting in a decrease in content. In Comparative Examples 4-6, the carbon content in the black powder was very high, and the nickel, cobalt, and manganese content in the metal foil was also high, indicating that the positive electrode powder desorption was incomplete. The aqueous binder of the negative electrode was easily soluble in water, and the negative electrode powder could be completely removed during the soaking in step 2. Therefore, the black powder in Comparative Examples 4-6 mainly contained carbon powder, and the positive electrode powder failed to completely detach from the aluminum foil. In Comparative Example 7, the pyrolysis temperature was high, and a large amount of aluminum foil was oxidized and entered the black powder.

[0133] Test case

[0134] To verify the electrical performance of the regenerated negative electrode material prepared above, lithium-ion batteries were prepared using this regenerated negative electrode material as the negative electrode and relevant tests were conducted. The weight formula for preparing the negative electrode is as follows: regenerated negative electrode material: conductive acetylene black: SBR: CMC = 94.5:1:2.5:2, mixed to form an active material slurry, coated on copper foil, dried, rolled, and slit to prepare negative electrode sheets, and then assembled into 2025 type coin cells for battery performance testing. The test results are shown in Table 2.

[0135] Table 2

[0136] 0.2C capacity mAh / g Capacity retention % after 100 cycles at 0.2C Example 1 358 96.7 Example 2 354 96.6 Example 3 351 95.9 Comparative Example 1 296 86.8 Comparative Example 2 294 86.5 Comparative Example 3 290 85.8 Comparative Example 4 355 95.7 Comparative Example 5 356 96.3 Comparative Example 6 353 96.1 Comparative Example 7 322 91.6

[0137] As can be seen from Table 2, the electrochemical performance of Comparative Examples 1-3 and Comparative Example 7 was poor due to the severe damage to the graphite structure.

[0138] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method of treating battery soot and producing a recycled graphite negative electrode, characterized by, The method comprises the following steps: S1: waste lithium ion battery is discharged, disassembled and crushed to obtain crushed material, and the crushed material is soaked in an impregnation liquid, which is one or both of a phosphate solution or a borate solution; S2: the soaked material is subjected to solid-liquid separation, and the obtained solid material is dried to obtain dried material; S3: the dried material is mixed with fused salt, heated to 310-350 DEG C for reaction, and then sieved at the heating temperature to obtain undersize fused salt slurry and oversize copper-aluminum foil, wherein the fused salt is at least one of potassium nitrate or sodium nitrate; S4: the undersize fused salt slurry is subjected to solid-liquid separation at the heating temperature of step S3 to obtain fused salt and black powder; S5: the black powder is mixed with acid liquid and reducing agent for leaching reaction, and solid-liquid separation is performed to obtain leaching liquid and leaching residue, and the leaching residue is subjected to anaerobic calcination to obtain regenerated graphite negative electrode.

2. The method of claim 1, wherein, In step S1, the particle size of the crushed material is ≤5 cm.

3. The method of claim 1, wherein, In step S1, the solid-liquid ratio of the crushed material to the impregnation liquid is 0.2-1.0 g / mL, and the impregnation liquid is a phosphate solution with a concentration of 0.2-0.5 g / mL and / or a borate solution with a concentration of 0.2-0.5 g / mL.

4. The method of claim 1, wherein, In step S1, the phosphate solution is at least one of potassium dihydrogen phosphate solution or sodium dihydrogen phosphate solution; and the borate solution is at least one of potassium tetraborate solution or sodium tetraborate solution.

5. The method of claim 1, wherein, In step S1, the soaking temperature is 60-75 DEG C, and the soaking time is 2.0-3.0 h.

6. The method of claim 1, wherein, In step S3, the mass ratio of the dried material to the fused salt is 1:(1.5-3.0).

7. The method of claim 1, wherein, In step S3, the screen mesh aperture of the sieving is 2-3 mm.

8. The method of claim 1, wherein, In step S5, the solid-liquid ratio of the black powder to the acid liquid is 1.0 g / (3.0-5.0) mL, and the concentration of the acid liquid is 0.1-1 mol / L.

9. The method of claim 1, wherein, In step S5, the anaerobic calcination temperature is 700-900 DEG C.

10. The regenerated graphite negative electrode prepared by the method according to any one of claims 1-9 is applied in a lithium ion battery.

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