Diaphragm pyrolysis assisted recovery method for valuable metals in waste lithium battery material

Abstract

The invention relates to a method for recycling valuable metals in a waste lithium battery material under the assistance of diaphragm pyrolysis, and belongs to the technical field of waste lithium battery recycling. N-methyl pyrrolidone is used as a solvent to be combined with microwave radiation to accelerate separation of a positive active material, and the solvent is recovered through a reduced pressure distillation technology, so that green and energy-saving circulating production is realized; in an inert gas environment, the metal reduction and recovery process is optimized through reducing gas and pyrolytic oil generated through diaphragm pyrolysis, and the pyrolytic oil can be further recycled. Antioxidant substances in the grape seeds and citric acid and ascorbic acid in the lemon juice have a synergistic effect, so that dissolution and complexation of metal ions are enhanced, and the recovery efficiency is improved; the metal extraction agent compounded by Cyanex 272 and pyrolytic oil is adopted, efficient and selective recovery of metal is achieved by adjusting the pH value, the whole process is clean and environmentally friendly, and the requirement for green development is met.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling waste lithium-ion batteries and relates to a method for recycling valuable metals in waste lithium battery materials by assisted diaphragm pyrolysis. Background Art

[0002] In recent years, with the rapid development of the electric vehicle industry, the consumption of lithium batteries, as its core power source, has shown a rapid growth trend. It is estimated that nearly 21 million waste lithium battery packs will be generated between 2015 and 2040. If waste lithium batteries are not properly recycled and effectively treated, the harmful substances in these batteries will seep into the soil and water, causing serious environmental pollution problems and affecting human life safety. Secondly, the abandonment of waste lithium batteries also means the waste and loss of rare and non-renewable high-value metal resources such as cobalt and lithium. Therefore, it is urgent to develop new methods for recycling valuable metals from waste lithium battery materials.

[0003] The traditional method of recovering valuable metals mainly uses inorganic strong acid to leach metal ions from waste batteries. Although this method can effectively extract metal elements, this process will produce a large amount of toxic waste liquid and release toxic gases such as chlorine and sulfur trioxide. These waste liquids and waste gases are extremely challenging to handle due to their complex chemical composition and high toxicity, and it is difficult to achieve efficient and harmless conversion or disposal. Therefore, exploring more environmentally friendly and efficient recycling technologies for valuable metals from waste lithium-ion batteries has become an urgent problem to be solved. Summary of the invention

[0004] The purpose of the present invention is to provide a method for recovering valuable metals from waste lithium battery materials by assisted diaphragm pyrolysis, which is green, environmentally friendly, energy-saving and efficient.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A method for recovering valuable metals from waste lithium battery materials by assisted diaphragm pyrolysis, the method for recovering valuable metals from waste lithium battery materials is as follows:

[0007] S1: Use saturated sodium chloride solution to discharge the waste lithium battery for 6 hours. After ensuring that the voltage is below 1.5V, disassemble the lithium battery, separate the battery shell, diaphragm, positive electrode and negative electrode components, wash each component with deionized water, and place it in a constant temperature drying oven for drying at 50°C for 12 hours.

[0008] S2: placing the dried positive electrode in N-methylpyrrolidone, irradiating with microwaves for 30 min at a heating temperature of 70° C., separating and recovering the N-methylpyrrolidone by vacuum distillation to obtain a positive electrode active material;

[0009] S3: The dried diaphragm and the positive electrode active material are put into a crusher for mixed crushing, and then the crushed product is placed in a tubular furnace for pyrolysis, and a protective gas is introduced. The pyrolysis temperature is set to 450°C, the pyrolysis time is 1h, and the temperature is cooled to room temperature at a cooling rate of 10°C / min, and the pyrolysis oil and solid mixture A are collected;

[0010] S4: grinding the grape seeds with a ball mill at a speed of 400 r / min for 1 h, and sieving with a 500-mesh sieve to obtain grape seed powder;

[0011] S5: adding grape seed powder to 55% to 65% lemon juice solution, heating and stirring at 50° C. for 30 min to obtain solution B;

[0012] S6: placing the solid mixture A in the solution B, stirring continuously at 75°C, while performing ultrasound assistance, the reaction time is 5 hours, and obtaining the solution C by vacuum filtration;

[0013] S7: adding the extraction active substance to the pyrolysis oil, wherein the volume ratio of the extraction active substance to the pyrolysis oil is 1:3, and stirring at 70° C. for 50 minutes to obtain a metal extractant;

[0014] S8: mixing solution C and a metal extractant, wherein the volume ratio of solution C to the metal extractant is 1:1, performing extraction under heating and pressurizing conditions, adjusting pH≈7.5 to extract cobalt in the system, and the extraction equilibrium time is 5 minutes, and separating using a separatory funnel to obtain solution D;

[0015] S9: Add saturated sodium carbonate solution to solution D, introduce high-purity argon gas and stir at 60° C. for 30 min, filter using a 0.45 μm filter membrane, wash the precipitate with deionized water, and obtain lithium carbonate after vacuum drying.

[0016] Furthermore, the active ingredient of the waste lithium battery is lithium cobalt oxide.

[0017] Furthermore, the parameters of the reduced pressure distillation in S2 are set to a temperature of 110° C. and a pressure of 1 kPa.

[0018] Furthermore, the protective gas in S3 is one of high-purity nitrogen or high-purity argon.

[0019] Furthermore, the solid-liquid mass ratio of the solid mixture A and the solution B in S6 is 1:5.

[0020] Furthermore, the ultrasonic power in S6 is 5kHz.

[0021] Furthermore, the active substance extracted in S7 is Cyanex 272.

[0022] Furthermore, in S8, the extraction temperature is 80° C. and the pressure is 3 MPa.

[0023] Selecting N-methylpyrrolidone as a solvent can selectively dissolve the binder and some impurities in the positive electrode material, and effectively separate the positive electrode active material from the current collector. Microwave radiation uniformly heats the solvent and the positive electrode material through high-frequency electromagnetic waves, accelerates the interaction between the solvent molecules and the positive electrode material, and significantly improves the separation efficiency of the positive electrode active material. After the separation and extraction is completed, the N-methylpyrrolidone is recovered by vacuum distillation technology. By reducing the system pressure, the boiling point of the solvent is significantly reduced, so that the distillation process can be carried out at a lower temperature. It not only effectively avoids the loss and oxidation of metal ions that may be caused by high temperature, but also ensures that the recovered N-methylpyrrolidone has a high purity, which is convenient for subsequent recycling. No harmful substances are produced in the process, which significantly reduces the production cost and embodies the green and energy-saving circular production concept.

[0024] In an inert gas atmosphere, the diaphragm will undergo a pyrolysis reaction and produce reducing gases such as carbon monoxide and hydrogen and pyrolysis oil. The reducing gas will undergo a reduction reaction with the high-valent cobalt in the positive electrode active material, reducing the high-valent metal to a low-valent form, thereby improving the efficiency and selectivity of subsequent acid leaching. The pyrolysis oil produced during the pyrolysis process is separated and recovered by physical methods, and the pyrolysis oil can be further used as an extraction compounding agent to achieve further recycling of resources.

[0025] Grape seeds are rich in a variety of antioxidants, such as catechin, epicatechin, epigallocatechin gallate, etc. These substances are easily oxidized to aldehyde or carboxyl groups at a lower potential, making it easier to combine with metal ions and promote the dissolution and leaching of metal ions. In addition, some components in grape seeds can form stable chelates with metal ions, which helps to further improve the leaching efficiency of metals.

[0026] Lemon juice is rich in citric acid, which contains three carboxylic acid groups. As an organic acid, citric acid has a strong ability to dissolve and complex metal ions. In the recycling process of waste lithium battery materials, citric acid can react with metal ions in the positive electrode material to form soluble metal citric acid complexes, which helps the leaching and recovery of metals. Lemon juice also contains a large amount of ascorbic acid. When acting in synergy with citric acid, ascorbic acid can further enhance the dissolution and complexation of metal ions, thereby improving the recovery rate and purity of metals.

[0027] When grape seeds and lemon juice are used together for lithium battery recycling, they can play a synergistic role. On the one hand, the antioxidants and chelating agents in grape seeds can combine with metal ions to promote the dissolution and leaching of metals; on the other hand, the acidic environment and reducing properties provided by lemon juice can further accelerate this process. In addition, compared with the commonly used inorganic acid leaching system, grape seeds and lemon juice, as natural biomass materials, will not cause environmental pollution after the reaction. They have the advantages of cleanliness, environmental protection and sustainability, which is in line with the current concept of green development.

[0028] The metal extractant prepared by compounding Cyanex 272 and pyrolysis oil has a good effect. Cyanex 272 can efficiently and selectively extract metal ions from the solution, improving the recovery rate and purity of the metal; the main components of pyrolysis oil are aromatic hydrocarbons, which have good solubility and stability, which help to disperse and dissolve Cyanex 272, enhance the extraction effect, and prevent Cyanex 272 from decomposing or deteriorating at high temperatures. Adjusting the pH value of the solution during the extraction process can change the existence form of cobalt, making it easier to form a complex with Cyanex 272; at the same time, the adjustment of pH value can also reduce the interference of impurity ions and improve the extraction purity of metal ions.

[0029] Beneficial effects of the present invention:

[0030] (1) N-methylpyrrolidone is selected as the solvent to effectively separate the positive electrode active material and the current collector through its selective dissolving ability. Microwave radiation technology is combined to accelerate the separation process and significantly improve the separation efficiency. During the recovery process, vacuum distillation technology is used to efficiently recover the solvent at low temperature, avoid high temperature loss and oxidation, ensure the high purity of the solvent, and realize green and energy-saving circular production.

[0031] (2) The diaphragm is converted into reducing gas and pyrolysis oil by pyrolysis reaction under an inert gas atmosphere. The reducing gas can reduce high-valent metals to improve the efficiency of subsequent acid leaching. The pyrolysis oil is recycled as an extraction compounding agent. The application of natural biomass materials such as grape seeds and lemon juice, through their antioxidant, chelating and reducing properties, promotes the dissolution, leaching and reduction of metal ions, improves the recovery rate and purity, and reduces environmental pollution, which is in line with the concept of green and sustainable development.

[0032] (3) The metal extractant prepared by compounding Cyanex 272 with pyrolysis oil can efficiently and selectively extract metal ions, improve the recovery rate and purity, and further improve the extraction effect by adjusting the pH value of the solution, optimizing the extraction conditions, and reducing the interference of impurities, so as to achieve high-purity recovery of cobalt ions. The extractant and its application method show good economic benefits and environmental friendliness; finally, lithium is further recovered through a simple and easy chemical precipitation method, realizing the efficient recovery of valuable metals in waste lithium batteries. DETAILED DESCRIPTION

[0033] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0034] Example 1

[0035] S1: Use saturated sodium chloride solution to discharge the waste lithium battery for 6 hours. After ensuring that the voltage is below 1.5V, disassemble the lithium battery, separate the battery shell, diaphragm, positive electrode and negative electrode components, wash each component with deionized water, and place it in a constant temperature drying oven for drying at 50°C for 12 hours.

[0036] S2: placing the dried positive electrode in N-methylpyrrolidone, heating it under microwave radiation for 30 min at a temperature of 70°C, separating and recovering the N-methylpyrrolidone by vacuum distillation at a temperature of 110°C and a pressure of 1 kPa, to obtain a positive electrode active material;

[0037] S3: The dried diaphragm and the positive electrode active material are placed in a crusher for mixed crushing, and then the crushed product is placed in a tubular furnace for pyrolysis, high-purity argon is introduced, the pyrolysis temperature is set to 450°C, the pyrolysis time is 1h, and the temperature is cooled to room temperature at a cooling rate of 10°C / min, and the pyrolysis oil and solid mixture A are collected;

[0038] S4: grinding the grape seeds with a ball mill at a speed of 400 r / min for 1 h, and sieving with a 500-mesh sieve to obtain grape seed powder;

[0039] S5: adding grape seed powder to 55% lemon juice solution, wherein the solid-liquid mass ratio of grape seed powder to lemon juice solution is 1:30, heating and stirring at 50° C. for 30 minutes to obtain solution B;

[0040] S6: placing the solid mixture A in the solution B, wherein the solid-liquid mass ratio of the solid mixture A to the solution B is 1:5, continuously stirring at 75°C, and simultaneously performing ultrasonic assistance, with an ultrasonic power of 5 kHz and a reaction time of 5 h, and obtaining the solution C by vacuum filtration;

[0041] S7: adding Cyanex 272 to the pyrolysis oil, wherein the volume ratio of Cyanex 272 to the pyrolysis oil is 1:3, and stirring at 70° C. for 50 minutes to obtain a metal extractant;

[0042] S8: mixing solution C and a metal extractant, wherein the volume ratio of solution C to the metal extractant is 1:1, performing extraction at an extraction temperature of 80°C and a pressure of 3 MPa, adjusting the pH to 7.5 to extract cobalt in the system, and the extraction equilibrium time is 5 min, and separating using a separatory funnel to obtain solution D;

[0043] S9: Add saturated sodium carbonate solution to solution D, wherein the volume ratio of solution D to saturated sodium carbonate solution is 2:1, introduce high-purity argon gas and stir at 60°C for 30 minutes, filter with a 0.45 μm filter membrane, wash the precipitate with deionized water, and obtain lithium carbonate after vacuum drying.

[0044] Example 2

[0045] S1: Use saturated sodium chloride solution to discharge the waste lithium battery for 6 hours. After ensuring that the voltage is below 1.5V, disassemble the lithium battery, separate the battery shell, diaphragm, positive electrode and negative electrode components, wash each component with deionized water, and place it in a constant temperature drying oven for drying at 50°C for 12 hours.

[0046] S2: placing the dried positive electrode in N-methylpyrrolidone, heating it under microwave radiation for 30 min at a temperature of 70°C, separating and recovering the N-methylpyrrolidone by vacuum distillation at a temperature of 110°C and a pressure of 1 kPa, to obtain a positive electrode active material;

[0047] S3: The dried diaphragm and the positive electrode active material are placed in a crusher for mixed crushing, and then the crushed product is placed in a tubular furnace for pyrolysis, high-purity argon is introduced, the pyrolysis temperature is set to 450°C, the pyrolysis time is 1h, and the temperature is cooled to room temperature at a cooling rate of 10°C / min, and the pyrolysis oil and solid mixture A are collected;

[0048] S4: grinding the grape seeds with a ball mill at a speed of 400 r / min for 1 h, and sieving with a 500-mesh sieve to obtain grape seed powder;

[0049] S5: adding grape seed powder to 60% lemon juice solution, wherein the solid-liquid mass ratio of grape seed powder to lemon juice solution is 1:30, heating and stirring at 50° C. for 30 minutes to obtain solution B;

[0050] S6: placing the solid mixture A in the solution B, wherein the solid-liquid mass ratio of the solid mixture A to the solution B is 1:5, continuously stirring at 75°C, and simultaneously performing ultrasonic assistance, with an ultrasonic power of 5 kHz and a reaction time of 5 h, and obtaining the solution C by vacuum filtration;

[0051] S7: adding Cyanex 272 to the pyrolysis oil, wherein the volume ratio of Cyanex 272 to the pyrolysis oil is 1:3, and stirring at 70° C. for 50 minutes to obtain a metal extractant;

[0052] S8: mixing solution C and a metal extractant, wherein the volume ratio of solution C to the metal extractant is 1:1, performing extraction at an extraction temperature of 80°C and a pressure of 3 MPa, adjusting the pH to 7.5 to extract cobalt in the system, and the extraction equilibrium time is 5 min, and separating using a separatory funnel to obtain solution D;

[0053] S9: Add saturated sodium carbonate solution to solution D, wherein the volume ratio of solution D to saturated sodium carbonate solution is 2:1, introduce high-purity argon gas and stir at 60°C for 30 minutes, filter with a 0.45 μm filter membrane, wash the precipitate with deionized water, and obtain lithium carbonate after vacuum drying.

[0054] Example 3

[0055] S1: Use saturated sodium chloride solution to discharge the waste lithium battery for 6 hours. After ensuring that the voltage is below 1.5V, disassemble the lithium battery, separate the battery shell, diaphragm, positive electrode and negative electrode components, wash each component with deionized water, and place it in a constant temperature drying oven for drying at 50°C for 12 hours.

[0056] S2: placing the dried positive electrode in N-methylpyrrolidone, heating it under microwave radiation for 30 min at a temperature of 70°C, separating and recovering the N-methylpyrrolidone by vacuum distillation at a temperature of 110°C and a pressure of 1 kPa, to obtain a positive electrode active material;

[0057] S3: The dried diaphragm and the positive electrode active material are placed in a crusher for mixed crushing, and then the crushed product is placed in a tubular furnace for pyrolysis, high-purity argon is introduced, the pyrolysis temperature is set to 450°C, the pyrolysis time is 1h, and the temperature is cooled to room temperature at a cooling rate of 10°C / min, and the pyrolysis oil and solid mixture A are collected;

[0058] S4: grinding the grape seeds with a ball mill at a speed of 400 r / min for 1 h, and sieving with a 500-mesh sieve to obtain grape seed powder;

[0059] S5: adding grape seed powder to 65% lemon juice solution, wherein the solid-liquid mass ratio of grape seed powder to lemon juice solution is 1:30, heating and stirring at 50° C. for 30 minutes to obtain solution B;

[0060] S6: placing the solid mixture A in the solution B, wherein the solid-liquid mass ratio of the solid mixture A to the solution B is 1:5, continuously stirring at 75°C, and simultaneously performing ultrasonic assistance, with an ultrasonic power of 5 kHz and a reaction time of 5 h, and obtaining the solution C by vacuum filtration;

[0061] S7: adding Cyanex 272 to the pyrolysis oil, wherein the volume ratio of Cyanex 272 to the pyrolysis oil is 1:3, and stirring at 70° C. for 50 minutes to obtain a metal extractant;

[0062] S8: mixing solution C and a metal extractant, wherein the volume ratio of solution C to the metal extractant is 1:1, performing extraction at an extraction temperature of 80°C and a pressure of 3 MPa, adjusting the pH to 7.5 to extract cobalt in the system, and the extraction equilibrium time is 5 min, and separating using a separatory funnel to obtain solution D;

[0063] S9: Add saturated sodium carbonate solution to solution D, wherein the volume ratio of solution D to saturated sodium carbonate solution is 2:1, introduce high-purity argon gas and stir at 60°C for 30 minutes, filter with a 0.45 μm filter membrane, wash the precipitate with deionized water, and obtain lithium carbonate after vacuum drying.

[0064] Example 4

[0065] S1: Use saturated sodium chloride solution to discharge the waste lithium battery for 6 hours. After ensuring that the voltage is below 1.5V, disassemble the lithium battery, separate the battery shell, diaphragm, positive electrode and negative electrode components, wash each component with deionized water, and place it in a constant temperature drying oven for drying at 50°C for 12 hours.

[0066] S2: placing the dried positive electrode in N-methylpyrrolidone, heating it under microwave radiation for 30 min at a temperature of 70°C, separating and recovering the N-methylpyrrolidone by vacuum distillation at a temperature of 110°C and a pressure of 1 kPa, to obtain a positive electrode active material;

[0067] S3: The dried diaphragm and the positive electrode active material are placed in a crusher for mixed crushing, and then the crushed product is placed in a tubular furnace for pyrolysis, high-purity argon is introduced, the pyrolysis temperature is set to 450°C, the pyrolysis time is 1h, and the temperature is cooled to room temperature at a cooling rate of 10°C / min, and the pyrolysis oil and solid mixture A are collected;

[0068] S4: grinding the grape seeds with a ball mill at a speed of 400 r / min for 1 h, and sieving with a 500-mesh sieve to obtain grape seed powder;

[0069] S5: adding grape seed powder to 55% lemon juice solution, wherein the solid-liquid mass ratio of grape seed powder to lemon juice solution is 1:30, heating and stirring at 50° C. for 30 minutes to obtain solution B;

[0070] S6: placing the solid mixture A in the solution B, wherein the solid-liquid mass ratio of the solid mixture A to the solution B is 1:5, continuously stirring at 75°C, and simultaneously performing ultrasonic assistance, with an ultrasonic power of 5 kHz and a reaction time of 5 h, and obtaining the solution C by vacuum filtration;

[0071] S7: adding Cyanex 272 to the pyrolysis oil, wherein the volume ratio of Cyanex 272 to the pyrolysis oil is 1:2, and stirring at 70° C. for 50 minutes to obtain a metal extractant;

[0072] S8: mixing solution C and a metal extractant, wherein the volume ratio of solution C to the metal extractant is 1:1, performing extraction at an extraction temperature of 80°C and a pressure of 3 MPa, adjusting the pH to 7.5 to extract cobalt in the system, and the extraction equilibrium time is 5 min, and separating using a separatory funnel to obtain solution D;

[0073] S9: Add saturated sodium carbonate solution to solution D, wherein the volume ratio of solution D to saturated sodium carbonate solution is 2:1, introduce high-purity argon gas and stir at 60°C for 30 minutes, filter with a 0.45 μm filter membrane, wash the precipitate with deionized water, and obtain lithium carbonate after vacuum drying.

[0074] Example 5

[0075] S1: Use saturated sodium chloride solution to discharge the waste lithium battery for 6 hours. After ensuring that the voltage is below 1.5V, disassemble the lithium battery, separate the battery shell, diaphragm, positive electrode and negative electrode components, wash each component with deionized water, and place it in a constant temperature drying oven for drying at 50°C for 12 hours.

[0076] S2: placing the dried positive electrode in N-methylpyrrolidone, heating it under microwave radiation for 30 min at a temperature of 70°C, separating and recovering the N-methylpyrrolidone by vacuum distillation at a temperature of 110°C and a pressure of 1 kPa, to obtain a positive electrode active material;

[0077] S3: The dried diaphragm and the positive electrode active material are placed in a crusher for mixed crushing, and then the crushed product is placed in a tubular furnace for pyrolysis, high-purity argon is introduced, the pyrolysis temperature is set to 450°C, the pyrolysis time is 1h, and the temperature is cooled to room temperature at a cooling rate of 10°C / min, and the pyrolysis oil and solid mixture A are collected;

[0078] S4: grinding the grape seeds with a ball mill at a speed of 400 r / min for 1 h, and sieving with a 500-mesh sieve to obtain grape seed powder;

[0079] S5: adding grape seed powder to 55% lemon juice solution, wherein the solid-liquid mass ratio of grape seed powder to lemon juice solution is 1:30, heating and stirring at 50° C. for 30 minutes to obtain solution B;

[0080] S6: placing the solid mixture A in the solution B, wherein the solid-liquid mass ratio of the solid mixture A to the solution B is 1:5, continuously stirring at 75°C, and simultaneously performing ultrasonic assistance, with an ultrasonic power of 5 kHz and a reaction time of 5 h, and obtaining the solution C by vacuum filtration;

[0081] S7: adding Cyanex 272 to the pyrolysis oil, wherein the volume ratio of Cyanex 272 to the pyrolysis oil is 1:4, and stirring at 70° C. for 50 minutes to obtain a metal extractant;

[0082] S8: mixing solution C and a metal extractant, wherein the volume ratio of solution C to the metal extractant is 1:1, performing extraction at an extraction temperature of 80°C and a pressure of 3 MPa, adjusting the pH to 7.5 to extract cobalt in the system, and the extraction equilibrium time is 5 min, and separating using a separatory funnel to obtain solution D;

[0083] S9: Add saturated sodium carbonate solution to solution D, wherein the volume ratio of solution D to saturated sodium carbonate solution is 2:1, introduce high-purity argon gas and stir at 60°C for 30 minutes, filter with a 0.45 μm filter membrane, wash the precipitate with deionized water, and obtain lithium carbonate after vacuum drying.

[0084] Comparative Example 1

[0085] No grape seed powder was added to the metal leaching system, and the remaining steps were the same as those in Example 1.

[0086] Comparative Example 2

[0087] Only Cyanex 272 was used as the extractant, and the remaining steps were consistent with those in Example 1.

[0088] Comparative Example 3

[0089] The extractant used was only pyrolysis oil, and the remaining steps were consistent with those in Example 1.

[0090] Comparative Example 4

[0091] No diaphragm was added during the pyrolysis process, and the remaining steps were consistent with Example 1.

[0092] The leaching rate of the metal and the purity of the lithium carbonate in the examples and comparative examples were detected by inductively coupled plasma mass spectrometry.

[0093] The experimental data are recorded as follows:

[0094] Cobalt leaching rate Lithium leaching rate Lithium carbonate purity Example 1 97.5％ 98.7％ 99.1％ Example 2 98.1％ 98.9％ 99.2％ Example 3 95.5％ 97.1％ 99.0％ Example 4 97.5％ 98.7％ 99.2％ Example 5 97.5％ 98.7％ 94.1％ Comparative Example 1 75.6％ 71.4％ 97.2％ Comparative Example 2 97.5％ 98.7％ 99.2％ Comparative Example 3 97.5％ 98.7％ 32.3％ Comparative Example 4 90.2％ 95.6％ 99.0％

[0095] It can be seen from the data of the embodiments and comparative examples that the addition of a diaphragm during the pyrolysis process is beneficial to improving the leaching rate of metals in subsequent steps. Lemon juice and grape seeds can be used to efficiently leach metal ions from waste lithium batteries. At the same time, the extractant prepared by mixing pyrolysis oil and Cyanex 272 in a volume ratio of 1:3 has a higher metal separation efficiency.

[0096] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for recovering valuable metals from waste lithium battery materials assisted by diaphragm pyrolysis, characterized in that: The method for recovering valuable metals from waste lithium battery materials is as follows: S1: Use saturated sodium chloride solution to discharge the waste lithium battery for 6 hours. After ensuring that the voltage is below 1.5V, disassemble the lithium battery, separate the battery shell, diaphragm, positive electrode and negative electrode components, wash each component with deionized water, and place it in a constant temperature drying oven for drying at 50°C for 12 hours. S2: placing the dried positive electrode in N-methylpyrrolidone, irradiating with microwaves for 30 min at a heating temperature of 70° C., separating and recovering the N-methylpyrrolidone by vacuum distillation to obtain a positive electrode active material; S3: The dried diaphragm and the positive electrode active material are put into a crusher for mixed crushing, and then the crushed product is placed in a tubular furnace for pyrolysis, and a protective gas is introduced. The pyrolysis temperature is set to 450°C, the pyrolysis time is 1h, and the temperature is cooled to room temperature at a cooling rate of 10°C / min, and the pyrolysis oil and solid mixture A are collected; S4: grinding the grape seeds with a ball mill at a speed of 400 r / min for 1 h, and sieving with a 500-mesh sieve to obtain grape seed powder; S5: adding grape seed powder to 55% to 65% lemon juice solution, heating and stirring at 50° C. for 30 min to obtain solution B; S6: placing the solid mixture A in the solution B, stirring continuously at 75°C, while performing ultrasound assistance, the reaction time is 5 hours, and obtaining the solution C by vacuum filtration; S7: adding the extraction active substance to the pyrolysis oil, wherein the volume ratio of the extraction active substance to the pyrolysis oil is 1:3, and stirring at 70° C. for 50 minutes to obtain a metal extractant; S8: mixing solution C and a metal extractant, wherein the volume ratio of solution C to the metal extractant is 1:1, performing extraction under heating and pressurizing conditions, adjusting pH≈7.5 to extract cobalt in the system, and the extraction equilibrium time is 5 minutes, and separating using a separatory funnel to obtain solution D; S9: Add saturated sodium carbonate solution to solution D, introduce high-purity argon gas and stir at 60° C. for 30 min, filter using a 0.45 μm filter membrane, wash the precipitate with deionized water, and obtain lithium carbonate after vacuum drying.

2. The method for recovering valuable metals from waste lithium battery materials by diaphragm pyrolysis-assisted method according to claim 1, characterized in that: The active component of the waste lithium battery is lithium cobalt oxide.

3. The method for recovering valuable metals from waste lithium battery materials by diaphragm pyrolysis-assisted method according to claim 1, characterized in that: The parameters of the reduced pressure distillation in S2 are set as temperature of 110° C. and pressure of 1 kPa.

4. The method for recovering valuable metals from waste lithium battery materials by diaphragm pyrolysis-assisted method according to claim 1, characterized in that: The protective gas in S3 is one of high-purity nitrogen or high-purity argon.

5. The method for recovering valuable metals from waste lithium battery materials by diaphragm pyrolysis-assisted method according to claim 1, characterized in that: The solid-to-liquid mass ratio of the solid mixture A to the solution B in S6 is 1:

5.

6. The method for recovering valuable metals from waste lithium battery materials by diaphragm pyrolysis-assisted method according to claim 1, characterized in that: The ultrasonic power in S6 is 5kHz.

7. The method for recovering valuable metals from waste lithium battery materials by diaphragm pyrolysis-assisted method according to claim 1, characterized in that: The active substance extracted in S7 is Cyanex 272.

8. The method for recovering valuable metals from waste lithium battery materials by diaphragm pyrolysis-assisted method according to claim 1, characterized in that: The extraction temperature in S8 is 80° C. and the pressure is 3 MPa.