Method for comprehensive recovery of ternary positive electrode waste slurry

Abstract

The application discloses a method for comprehensively recovering ternary positive electrode waste slurry, which comprises the following steps: adding the ternary positive electrode waste slurry into NMP slurry, mixing the obtained secondary slurry with polyacrylamide, adding metal salt, heating and reacting, separating to obtain crude NMP and solid residue, and through negative pressure evaporation, dehydration, and anaerobic roasting, water soaking to obtain a lithium salt solution and a filter residue. The application utilizes the characteristics of PAM hydrolysis crosslinking and water absorption material, fixes water, separates NMP, reduces the pressure brought by subsequent rectification, and PAM can be used as a reducing agent to reduce and roast the ternary positive electrode waste, which is convenient for subsequent leaching and improves the recovery rate of metal elements.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion battery positive paste recycling, and particularly relates to a method for comprehensively recycling ternary positive waste paste. BACKGROUND

[0002] Ternary lithium ion batteries are widely used in portable electronic device products such as mobile phones, mobile power supplies and notebooks due to their good safety, high energy density, environmental protection and good electrochemical performance. Meanwhile, with the continuous development of the new energy automobile industry, the demand for lithium ion batteries in the market is also expanding. However, during the manufacturing of ternary positive plates, the changes in the environment, foreign matters and viscosity can easily cause the failure of the paste. In addition, unqualified paste produced due to incorrect proportioning, waste liquid produced during the cleaning of storage tanks, pipelines or floors and other links will inevitably produce waste paste.

[0003] The composition of the waste paste includes NMP (N-methyl pyrrolidone), water, a conductive agent, a positive material and polyvinylidene fluoride (PVDF), and also contains foreign matters such as paste packaging plastic bags, rags and gloves. Since the positive material in the waste paste contains Ni, Co and Mn metals, the waste paste has great recyclable value. If the waste paste is not properly treated, not only will it cause resource waste, but also will it cause environmental pollution.

[0004] At present, some recycling treatment systems and methods for lithium battery positive waste paste have appeared in the market. For example, Chinese patent document 201610662341.4 discloses a lithium ion battery positive waste paste recycling system and method. The disclosed recycling system realizes the continuous and efficient recycling of positive waste paste in the production of lithium ion batteries, can ensure the purity of the recycled material, has high efficiency and small pollution, but lacks an NMP recycling method, and the recycling process is relatively complicated. Similarly, Chinese patent document 201610157841.9 discloses a recycling method for lithium ion battery positive material waste paste. The method mixes the solvent NMP used for preparing paste in production with lithium ion battery positive material waste paste, and then removes water by distillation. The waste paste can be directly used for battery plate slurry after treatment. However, the method cannot be applied to actual complex on-site production, and paste agglomeration and solid foreign matters are difficult to reuse, which does not match the actual production process.

[0005] In addition, the treated waste paste usually adopts reduction acid leaching, that is, the waste ternary positive material is leached by sulfuric acid and hydrogen peroxide to dissolve metal elements such as nickel, cobalt, manganese and lithium. After purification, pure Ni, Co and Mn salt solutions are obtained by using the solution extraction process. The method is simple, but the extractant has extraction capacity for lithium, and the recovery rate of lithium is low.

[0006] Therefore, there is an urgent need for a process method capable of effectively separating metal elements in lithium battery positive electrode waste slurry and realizing NMP recycling, which is of great significance for environmental protection, cost reduction and matching existing actual production processes. SUMMARY

[0007] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application proposes a method for comprehensive recovery of ternary positive electrode waste slurry, which recovers NMP in waste slurry and realizes recovery of valuable metals in positive electrode materials, thereby improving the yield of lithium.

[0008] According to one aspect of the present application, a method for comprehensive recovery of ternary positive electrode waste slurry is proposed, comprising the following steps:

[0009] S1: crushing ternary positive electrode waste slurry, adding N-methyl pyrrolidone for slurry preparation, and obtaining secondary slurry;

[0010] S2: mixing the secondary slurry with polyacrylamide, then adding metal salt, and heating to hydrolyze and crosslink the polyacrylamide, and after the reaction is completed, solid-liquid separation is performed to obtain crude N-methyl pyrrolidone and solid residue;

[0011] S3: the solid residue is subjected to negative pressure evaporation, and then is heated to dehydrate under anaerobic conditions to obtain a dehydrated product;

[0012] S4: the dehydrated product is subjected to anaerobic roasting, and the obtained roasted residue is soaked with water, and solid-liquid separation is performed to obtain a lithium salt solution and a filter residue.

[0013] In some embodiments of the present application, in step S1, the particle size of the crushed material is below 20 mm.

[0014] In some embodiments of the present application, in step S1, the amount of N-methyl pyrrolidone used is 1-2 times the volume of the ternary positive electrode waste slurry.

[0015] In some embodiments of the present application, in step S2, the amount of polyacrylamide used is 5%-10% of the mass of the secondary slurry.

[0016] In some embodiments of the present application, in step S2, the polyacrylamide is non-ionic polyacrylamide.

[0017] In some embodiments of the present application, in step S2, the molecular weight of the polyacrylamide is below 1 million. If the molecular weight of the polyacrylamide is too high, the viscosity of the slurry will be too large, and the polyacrylamide will easily undergo physical crosslinking and be difficult to disperse.

[0018] In some embodiments of the present application, in step S2, the metal salt is at least one of a sulfate or a chloride salt of nickel, cobalt or manganese.

[0019] In some embodiments of the present application, in step S2, the metal salt is used in an amount of 2-5% by mass of the polyacrylamide.

[0020] In some embodiments of the present application, in step S2, the heating reaction is carried out at a temperature of 90-100°C. Further, the heating reaction is carried out for a time of 10-20 min.

[0021] In some embodiments of the present application, in step S2, the crude N-methyl pyrrolidone is subjected to a rectification process or returned to step S1 for the slurry preparation.

[0022] In some embodiments of the present application, in step S3, the negative pressure evaporation is carried out at a pressure of 7.5-10.5 kPa and a temperature of 50-60°C. Further, the negative pressure evaporation is carried out for a time of 2-6 h.

[0023] In some embodiments of the present application, in step S3, the heating dehydration is carried out at a temperature of 150-200°C. Further, the heating dehydration is carried out for a time of 30-60 min.

[0024] In some embodiments of the present application, in step S4, the oxygen-free roasting is carried out at a temperature of 600-900°C. Further, the oxygen-free roasting is carried out for a time of 1-3 h.

[0025] In some embodiments of the present application, in step S4, the solid-liquid ratio of the roasting residue and water is 0.5-1.5 g / mL.

[0026] In some embodiments of the present application, in step S4, the soaking is carried out for a time of 10-30 min.

[0027] According to a preferred embodiment of the present application, at least the following beneficial effects are achieved:

[0028] 1. The present application mixes ternary positive electrode waste slurry with NMP to prepare slurry, then adds PAM powder in the secondary slurry, so that PAM is uniformly dispersed in the secondary slurry and absorbs the water in the slurry, then heating and hydrolysis is carried out by adding metal salt, PAM gradually hydrolyzes and crosslinks and solidifies, so that the water in the slurry exists in the solid material, thereby separating from NMP, then solid-liquid separation is carried out, to obtain crude NMP, so as to reduce the pressure of NMP rectification system; the solid residue is subjected to negative pressure evaporation to recover the remaining NMP, the product is dehydrated and then subjected to oxygen-free roasting, the carbide of PAM is used as a reducing agent to reduce the ternary positive electrode material at high temperature, and after water immersion, lithium salt solution and transition metal filter residue which is easy to be treated by acid immersion are directly obtained.

[0029] 2、The application makes full use of the characteristics of PAM hydrolysis crosslinking and water absorption material, fixes water, separates out precious NMP, reduces the pressure brought by subsequent rectification, and PAM can be used as a reducing agent for reducing roasting of ternary positive electrode waste, which is convenient for subsequent leaching and improves the recovery rate of metal elements.

[0030] 3、In order to avoid too high viscosity of the slurry, NMP is additionally added to dilute the slurry and reduce the solid content of the slurry, which is beneficial to uniform dispersion of PAM.

[0031] 4、The application not only uses PAM to fix moisture in the slurry, but also uses the flocculation of PAM to make the small particles in the slurry flocculate, so that the crude NMP produced by pressure filtration contains a large amount of solid small particles, and the recovery rate of the positive electrode material is improved. BRIEF DESCRIPTION OF DRAWINGS

[0032] The application will be further described below in combination with the drawings and examples, in which:

[0033] Figure 1 The process flow chart of the application. DETAILED DESCRIPTION

[0034] The concept and technical effects of the application will be described below in combination with examples, so as to fully understand the purpose, features and effects of the application. Obviously, the described examples are only a part of the examples of the application, but not all the examples. Based on the examples of the application, other examples obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0035] Example 1

[0036] A method for comprehensive recovery of ternary positive electrode waste slurry, referring to Figure 1 , the specific process is as follows:

[0037] Step 1, tearing the ternary positive electrode waste slurry by a tearing machine until the particle size is below 20 mm;

[0038] Step 2, adding NMP according to 2 times the volume of the ternary positive electrode waste slurry to prepare secondary slurry;

[0039] Step 3, under continuous stirring, adding 5% of the total mass of the slurry of non-ionic PAM powder (molecular weight below 1 million) to the secondary slurry, uniformly dispersing the PAM, then adding 2% of the mass of the PAM of nickel sulfate, and heating to 90℃ for 20 min, so that the PAM hydrolysis crosslinking, the tail gas generated in the hydrolysis crosslinking process enters the tail gas treatment system;

[0040] Step 4, solid-liquid separation is carried out by using a filter press to obtain crude NMP and filter residue, and the crude NMP enters a rectification process or returns to step 2 for slurry preparation;

[0041] Step 5, negative pressure evaporation is carried out on the filter residue, the negative pressure pressure is controlled to be 7.5 kPa, the evaporation temperature is 50 DEG C, the evaporation time is 2 h, and the evaporation tail gas enters a rectification system;

[0042] Step 6, the evaporation product is dehydrated under oxygen-free conditions at 150 DEG C for 60 min;

[0043] Step 7, after dehydration, the product is subjected to oxygen-free calcination at 600 DEG C for 3 h in the absence of air / oxygen to obtain calcined residue;

[0044] Step 8, water is added to the calcined residue according to a solid-liquid ratio of 0.5 g / mL, and soaked for 10 min;

[0045] Step 9, solid-liquid separation is carried out to obtain filter residue and lithium salt solution, and the filter residue is subjected to acid leaching to obtain a metal salt solution.

[0046] Example 2

[0047] A method for comprehensive recovery of ternary positive electrode waste slurry, the specific process is as follows:

[0048] Step 1, the ternary positive electrode waste slurry is torn by a shredder to a particle size of less than 20 mm;

[0049] Step 2, NMP is added according to 1.5 times the volume of the ternary positive electrode waste slurry to prepare secondary slurry;

[0050] Step 3, under constant stirring, 8% of the total mass of the slurry of non-ionic PAM powder (molecular weight below 1 million) is added to the secondary slurry, the PAM is uniformly dispersed, then 3% of the mass of the PAM of manganese sulfate is added, and the temperature is raised to 95 DEG C for 15 min, so that the PAM is hydrolyzed and cross-linked, and the tail gas generated in the hydrolysis and cross-linking process enters a tail gas treatment system;

[0051] Step 4, solid-liquid separation is carried out by using a filter press to obtain crude NMP and filter residue, and the crude NMP enters a rectification process or returns to step 2 for slurry preparation;

[0052] Step 5, negative pressure evaporation is carried out on the filter residue, the negative pressure pressure is controlled to be 9.0 kPa, the evaporation temperature is 55 DEG C, the evaporation time is 4 h, and the evaporation tail gas enters a rectification system;

[0053] Step 6, the evaporation product is dehydrated under oxygen-free conditions at 180 DEG C for 45 min;

[0054] Step 7, after dehydration, the product is subjected to oxygen-free roasting at 750℃ for 2h in the absence of air / oxygen to obtain roasting residue;

[0055] Step 8, water is added to the roasting residue according to a solid-liquid ratio of 1.0g / mL, and soaked for 20min;

[0056] Step 9, solid-liquid separation is performed to obtain filter residue and lithium salt solution, and the filter residue is subjected to acid leaching to obtain metal salt solution.

[0057] Example 3

[0058] A method for comprehensive recovery of ternary positive electrode waste slurry, the specific process is as follows:

[0059] Step 1, the ternary positive electrode waste slurry is torn by a shredder until the particle size is below 20mm;

[0060] Step 2, NMP is added according to 1 times the volume of the ternary positive electrode waste slurry to prepare a secondary slurry;

[0061] Step 3, under constant stirring, 10% of the total mass of the slurry of non-ionic PAM powder (molecular weight below 1 million) is added to the secondary slurry, and after uniform dispersion of the PAM, 5% of the mass of the PAM of nickel chloride is added, and the temperature is raised to 100℃ for 10min to hydrolyze and crosslink the PAM, and the tail gas generated in the hydrolysis and crosslinking process enters the tail gas treatment system;

[0062] Step 4, solid-liquid separation is performed by a filter press to obtain crude NMP and filter residue, and the crude NMP enters a rectification process or returns to step 2 for slurry preparation;

[0063] Step 5, the filter residue is subjected to negative pressure evaporation, the negative pressure pressure is controlled at 10.5kPa, the evaporation temperature is 60℃, and the evaporation time is 6h, and the evaporation tail gas enters the rectification system;

[0064] Step 6, the evaporation product is subjected to dehydration at 200℃ for 30min under oxygen-free conditions;

[0065] Step 7, after dehydration, the product is subjected to oxygen-free roasting at 900℃ for 1h in the absence of air / oxygen to obtain roasting residue;

[0066] Step 8, water is added to the roasting residue according to a solid-liquid ratio of 1.5g / mL, and soaked for 30min;

[0067] Step 9, solid-liquid separation is performed to obtain filter residue and lithium salt solution, and the filter residue is subjected to acid leaching to obtain metal salt solution.

[0068] Table 1 Main components of 100g original ternary positive electrode waste slurry used in examples 1-3

[0069] NMP water Li nickel cobalt manganese 28.3g 9.6g 4.2g 36g

[0070] Comparative Example

[0071] A method for comprehensive recovery of ternary positive electrode waste slurry, the main difference from Example 1 is that PAM is not added, the specific process is as follows:

[0072] Step 1, the ternary positive electrode waste slurry is torn by a shredder, and the particle size is below 20mm;

[0073] Step 2, solid-liquid separation is carried out by a filter press, and crude NMP and filter residue are obtained;

[0074] Step 3, the filter residue is subjected to negative pressure evaporation, the negative pressure is controlled at 7.5kPa, the evaporation temperature is 50℃, and the evaporation time is 2h, and the evaporation tail gas enters the rectification system;

[0075] Step 4, the evaporation product is calcined at 600℃ for 3h under anaerobic conditions, and calcined residue is obtained;

[0076] Step 5, water is added to the calcined residue according to the solid-liquid ratio of 0.5g / mL, and soaked for 10min;

[0077] Step 6, solid-liquid separation is carried out, and filter residue and lithium salt solution are obtained, and the filter residue is subjected to acid leaching to obtain a metal salt solution.

[0078] Table 2 Water content of crude NMP obtained in Examples 1-3 and Comparative Example

[0079] water content of crude NMP g / g Example 1 4.1％ Example 2 4.5％ Example 3 5.7％ Comparative Example 25.9％

[0080] As shown in Table 2, the water content of crude NMP in the comparative example is very high, which is due to the fact that PAM is not added to fix the water, so that NMP in the waste slurry cannot be separated from water. High water content will increase the pressure brought by subsequent rectification.

[0081] Table 3 Molar ratio of Li to transition metal in the filter residue finally obtained in Examples 1-3 and Comparative Example

[0082] Li / transition metal Example 1 0.034 Example 2 0.028 Example 3 0.033 Comparative Example 0.831

[0083] As shown in Table 3, the lithium content in the filter residue of the comparative example is very high, while the filter residue of the examples only contains a very small amount of lithium. This is because the comparative example is only ordinary anaerobic calcination, there is no reducing agent, and the calcination process cannot well destroy the crystal structure of the ternary positive electrode material, so only a small amount of lithium ions are leached out, and most of them still exist in the filter residue.

[0084] The embodiments of the present application are described in detail above with reference to the drawings, but the present application is not limited to the above-described embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application. Furthermore, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for comprehensive recovery of ternary positive electrode waste slurry, characterized in that, The method comprises the following steps: S1: crushing ternary positive electrode waste slurry, adding N-methyl pyrrolidone for slurry preparation to obtain secondary slurry; S2: mixing the secondary slurry with polyacrylamide, then adding metal salt, heating to hydrolyze and crosslink the polyacrylamide, after reaction, solid-liquid separation is performed to obtain crude N-methyl pyrrolidone and solid residue; S3: the solid residue is subjected to negative pressure evaporation, then is heated to dehydrate under anaerobic condition to obtain dehydrated product; S4: the dehydrated product is subjected to anaerobic roasting, the roasted residue is soaked with water, and solid-liquid separation is performed to obtain lithium salt solution and filter residue; In step S2, the polyacrylamide is non-ionic polyacrylamide; the metal salt is at least one of sulfate or chloride salt of nickel, cobalt or manganese; the amount of the polyacrylamide is 5%-10% of the mass of the secondary slurry; the amount of the metal salt is 2%-5% of the mass of the polyacrylamide.

2. The method of claim 1, wherein, In step S1, the amount of the N-methyl pyrrolidone is 1-2 times of the volume of the ternary positive electrode waste slurry.

3. The method of claim 1, wherein, In step S2, the molecular weight of the polyacrylamide is below 1 million.

4. The method of claim 1, wherein, In step S2, the temperature of the heating reaction is 90-100℃.

5. The method of claim 1, wherein, In step S3, the pressure of the negative pressure evaporation is 7.5-10.5kPa, and the temperature is 50-60℃.

6. The method of claim 1, wherein, In step S3, the temperature of the heating dehydration is 150-200℃.

7. The method of claim 1, wherein, In step S4, the temperature of the anaerobic roasting is 600-900℃.

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