A method for regenerating waste slurry of lithium-ion battery negative electrode

Abstract

The present invention relates to the technical field of resource recycling of lithium ion batteries, and specifically discloses a method for regenerating waste negative electrode slurry of lithium ion batteries. The present invention first uses an organic acid to break the negative electrode waste slurry, which can fully break the agglomerates in the slurry so that the active material and the conductive agent are more evenly dispersed in the slurry, so that the active material and the conductive agent can be fully recovered later. At the same time, the organic acid will not have an adverse effect on the structure of the active material and the conductive agent. Moreover, the viscosity of the slurry after breaking the gel is reduced, which is more conducive to subsequent filtration; then, a specific collector and a foaming agent are added to the broken gel slurry, so that the active material and the conductive agent are flocculated and agglomerated and float on the surface of the slurry, and then through multi-stage precision filtration, water washing and calcination, a regenerated negative electrode material with a purity of more than 99% is obtained, and the graphite structure recovered is not destroyed, and the graphite loss rate is low. It can be directly used as a raw material for producing negative electrode slurry, realizing efficient recycling of negative electrode materials.

Description

Technical Field

[0001] The invention relates to the technical field of resource recycling of lithium ion batteries, and in particular to a method for recycling waste negative electrode slurry of lithium ion batteries. Background Art

[0002] With the rapid development of the new energy industry, lithium-ion batteries have been widely used in mobile phones, digital cameras, electric vehicles and other fields. At present, the negative electrode slurry of lithium-ion batteries is mainly prepared with graphite as the active material, carbon black (SP) as the conductive agent, carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) as the binder. In the production process of lithium-ion batteries, negative electrode slurry waste will be generated. The negative electrode waste slurry mainly comes from the stirring process, coating process, cleaning of the mixing tank, slurry pipeline and other processes. The waste slurry contains materials such as graphite and conductive carbon, which has a high recycling value. However, at present, the negative electrode waste slurry is generally treated by direct scrapping. This treatment method will not only cause pollution to water, soil, etc., but also cause waste of resources. Effective recycling and treatment of negative electrode waste slurry can not only reduce environmental pollution, but also realize the reuse of resources, which has important economic and environmental significance.

[0003] At present, CN114843650A reports a method for recycling graphite negative electrode waste, which mainly includes obtaining high-purity regenerated graphite after leaching graphite waste with sulfuric acid and calcining at high temperature, adding a certain proportion of silicon powder, PVP powder, alcohol and NMP for two ball milling to obtain slurry, and then spray drying and secondary calcining the slurry to obtain silicon-carbon material. The above method is complicated to operate, involving chemical reactions and multiple high-temperature calcinations, which is not only costly, but also structurally damages materials such as graphite, conductive carbon or CMC. Therefore, it is urgent to develop a method for regenerating negative electrode waste slurry that is efficient, environmentally friendly, low in energy consumption, and does not destroy the graphite structure, so as to reduce the environmental protection and raw material costs of lithium-ion batteries and meet the rapid development of lithium-ion batteries. Summary of the invention

[0004] Aiming at the problem that the existing resource utilization method of waste negative electrode slurry of lithium ion batteries has complicated steps, involves chemical reactions and multiple high-temperature calcinations, etc., which is not only costly but also damages the structure of materials such as graphite, conductive carbon or CMC, the present invention provides a regeneration method of waste negative electrode slurry of lithium ion batteries. The method mainly comprises adding an organic acid to the waste negative electrode slurry for gel breaking, then adding a capture agent and a foaming agent to the slurry after gel breaking, and performing multi-stage filtration to obtain a high-purity and high-recovery negative electrode material, thereby realizing the regeneration of the waste negative electrode slurry and having high economic and environmental benefits.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0006] A method for regenerating waste negative electrode slurry of a lithium-ion battery comprises the following steps:

[0007] Step a, adding an organic acid to the lithium ion battery negative electrode waste slurry to stir and break the gel, thereby obtaining a broken gel slurry;

[0008] Step b, adding an oil collector and a non-ionic foaming agent to the debonding slurry, and mixing them evenly to obtain a mixed slurry;

[0009] Step c, filtering the mixed slurry through a multi-stage precision filtration system with successively decreasing pore sizes to obtain a filtrate and a filter residue, washing the filter residue, and then calcining it at a high temperature to obtain a regenerated negative electrode material; wherein the pore size of the precision filtration system is ≥8000 mesh.

[0010] Compared with the prior art, the regeneration method of the waste negative electrode slurry of the lithium ion battery provided by the present invention first uses an organic acid to break the gel of the waste negative electrode slurry, which can fully break the agglomerates in the slurry so that the active material and the conductive agent are more evenly dispersed in the slurry, so that the active material and the conductive agent can be fully recovered later. At the same time, the organic acid will not have an adverse effect on the structure of the active material and the conductive agent. Moreover, the viscosity of the slurry after breaking the gel is reduced, which is more conducive to subsequent filtration; then, a specific collector and a foaming agent are added to the broken gel slurry to make the active material and the conductive agent flocculate and agglomerate and float on the surface of the slurry. Subsequently, through multi-stage precision filtration, water washing and calcination, a regenerated negative electrode material with a purity of more than 99% is obtained, and the structure of the recovered graphite is not destroyed, the graphite loss rate is low, and it can be directly used as a raw material for producing negative electrode slurry, thereby realizing efficient recycling of negative electrode materials.

[0011] The present invention realizes the recycling of negative electrode materials in negative electrode waste slurry through simple acid-adding degelling, capturing and agglomerating negative electrode active substances and conductive agents, and washing and calcining steps, thereby reducing environmental treatment and raw material costs, having high economic and environmental benefits, and having high promotion and application value.

[0012] It should be noted that the negative electrode waste slurry described in the present invention can be conventional negative electrode slurry in the art. The waste slurry is generated during the stirring process, coating process, cleaning of the stirring tank, slurry pipeline, etc. The waste slurry generated in the above process can be collected and recycled according to the above steps.

[0013] Furthermore, in step a, the organic acid is one or more of formic acid, oxalic acid or succinic acid.

[0014] Furthermore, in step a, the amount of the organic acid added is 0.5% to 1% of the mass of the negative electrode waste slurry.

[0015] Furthermore, in step a, the stirring and breaking gel rotation speed is 30r / min~50r / min, and the stirring and breaking gel time is 1h~2h.

[0016] The preferred type, amount of addition, stirring speed and time of the organic acid can minimize the residue of the organic acid in the system and the damage to the structures of graphite and conductive agent, while ensuring that the negative electrode slurry is fully broken.

[0017] Furthermore, in step b, the oil collector is one or both of kerosene and diesel.

[0018] Furthermore, in step b, the amount of the oil collector added is 0.01% to 0.03% of the mass of the negative electrode waste slurry.

[0019] Furthermore, in step b, the nonionic foaming agent is one or more of 2# oil, 4# oil, pine oil, cresol acid or camphor oil.

[0020] Furthermore, in step b, the amount of the non-ionic foaming agent added is 0.01% to 0.03% of the mass of the negative electrode waste slurry.

[0021] The preferred collector is combined with a specific foaming agent to fully capture the graphite and conductive agent in the slurry system, and make the captured components float on the slurry surface, thereby improving the recovery rate of graphite and conductive agent and the subsequent filtration efficiency.

[0022] Exemplarily, after adding the collector and the frother, stirring is carried out at 50 r / min to 80 r / min for 2 h to 3 h to fully.

[0023] Furthermore, in step c, the multi-stage precision filtration system is a two-stage filtration system, wherein the pore size of the first-stage filtration system is 8000 mesh to 10000 mesh, and the pore size of the second-stage filtration system is 15000 mesh to 20000 mesh.

[0024] The use of the above-mentioned precision filtration system can fully recover the graphite and conductive agent in the negative electrode slurry, thereby improving the recovery rate.

[0025] Exemplarily, after filtering with a filter cloth of 8000-10000 mesh, the filtrate is filtered again with a filter cloth of 15000-20000 mesh, the filter residues are combined, and the filter residues are washed and calcined.

[0026] Furthermore, in step c, the washing specifically comprises: washing with water and organic alcohol in sequence, and the number of washing times is ≥3.

[0027] Exemplarily, the organic alcohol is methanol, ethanol or propanol.

[0028] It should be noted that the number of times the filter residue is washed with water and alcohol is based on the residual amount of collector and foaming agent in the filter residue being ≤0.1%.

[0029] Furthermore, the filtrate obtained in step b is distilled to recover the organic solvent in the filtrate. The recovered organic solvent can be reused in the preparation of the negative electrode slurry, thereby reducing the amount of waste liquid generated and avoiding waste of resources.

[0030] Furthermore, in step c, the calcination temperature is 1000° C. to 1200° C., and the calcination time is 5 min to 10 min.

[0031] Furthermore, in step c, the temperature is raised to 1000°C-1200°C by programmed heating, and the heating rate is ≥200°C / s.

[0032] The optimal calcination temperature and time can fully remove residual impurities and ensure the purity of the recovered graphite and conductive agent while ensuring that the structure of the graphite and conductive agent is not destroyed and the graphite loss rate is low.

[0033] The regeneration method of lithium ion battery negative electrode waste slurry provided by the present invention simplifies the complex steps in the traditional recycling process, reduces the operation difficulty and cost, and the method will not cause structural damage to materials such as graphite and conductive carbon, ensuring that the recycled negative electrode material still has good electrochemical properties. The recycled negative electrode material can be reused in the production of lithium ion batteries, thereby increasing the added value of the negative electrode waste slurry. At the same time, it also reduces environmental pollution and resource waste, which is of great significance for promoting the sustainable development of the lithium ion battery industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the process flow for recycling waste negative electrode slurry of lithium-ion batteries in an embodiment of the present invention;

[0035] Figure 2 is a SEM image of graphite recovered in Example 1 of the present invention;

[0036] Figure 3 This is a SEM image of the graphite recovered in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] The traditional recycling technology scheme has complicated steps, involving chemical reactions and high-temperature calcination, which is not only costly, but also causes structural damage to materials such as graphite, conductive carbon or CMC. In order to solve this problem, the embodiment of the present invention provides a resource recycling technology for scrapped negative electrode slurry in the lithium battery production process, including the following steps:

[0039] Step a, adding an organic acid to the lithium ion battery negative electrode waste slurry to stir and break the gel, thereby obtaining a broken gel slurry;

[0040] Step b, adding an oil collector and a non-ionic foaming agent to the debonding slurry, and mixing them evenly to obtain a mixed slurry;

[0041] Step c, filtering the mixed slurry through a multi-stage precision filtration system with successively decreasing pore sizes to obtain a filtrate and a filter residue, washing the filter residue, and then calcining it at a high temperature to obtain a regenerated negative electrode material; wherein the pore size of the precision filtration system is ≥8000 mesh.

[0042] The method provided by the present invention not only solves the problems existing in the existing recycling technology, but also realizes the efficient, low-cost, environmentally friendly recycling and reuse of the negative electrode slurry of waste lithium-ion batteries, which is of great significance for promoting the sustainable development of the lithium-ion battery industry.

[0043] In order to better illustrate the present invention, further examples are given below.

[0044] Example 1

[0045] The embodiment of the present invention provides a method for regenerating waste negative electrode slurry of a lithium ion battery, comprising the following steps:

[0046] Step a, transferring the collected lithium-ion battery negative electrode waste slurry into a container, adding 0.8% oxalic acid by weight of the negative electrode waste slurry, stirring and breaking the gel at 40 r / min for 1.5 h to obtain a broken gel slurry;

[0047] Step b, adding 0.02% kerosene and 0.02% pine oil by weight of the negative electrode waste slurry to the debonding slurry, stirring at 70 r / min for 2.5 h to obtain a mixed slurry;

[0048] Step c, filtering the mixed slurry through a 10000 mesh filter cloth to obtain a filter residue and a filtrate; finely filtering the obtained filtrate through a 20000 mesh filter cloth to obtain an organic solvent, and combining the filter residues;

[0049] Step d, washing the filter residue with deionized water and ethanol four times in sequence, heating the washed filter residue to 1100° C. at a rate of 200° C. / s, and calcining for 8 minutes to obtain a regenerated negative electrode material.

[0050] Example 2

[0051] The embodiment of the present invention provides a method for regenerating waste negative electrode slurry of a lithium ion battery, comprising the following steps:

[0052] Step a, transferring the collected lithium-ion battery negative electrode waste slurry into a container, adding succinic acid in an amount of 0.5% by mass of the negative electrode waste slurry, stirring and breaking the gel at 30 r / min for 2 h, and obtaining a broken gel slurry;

[0053] Step b, adding 0.01% diesel and 0.03% 2# oil by weight of the negative electrode waste slurry to the broken gel slurry, stirring at 50 r / min for 3 hours to obtain a mixed slurry;

[0054] Step c, filtering the mixed slurry through an 8000 mesh filter cloth to obtain a filter residue and a filtrate; finely filtering the obtained filtrate through a 15000 mesh filter cloth to obtain an organic solvent, and combining the filter residues;

[0055] Step d, washing the filter residue with deionized water and ethanol for 5 times in sequence, heating the washed filter residue to 1200° C. at a rate of 250° C. / s, and calcining for 5 minutes to obtain a regenerated negative electrode material.

[0056] Example 3

[0057] The embodiment of the present invention provides a method for regenerating waste negative electrode slurry of a lithium ion battery, comprising the following steps:

[0058] Step a, transferring the collected lithium-ion battery negative electrode waste slurry into a container, adding formic acid at 1% by mass of the negative electrode waste slurry, stirring and breaking the gel at 50 r / min for 1 hour, and obtaining a broken gel slurry;

[0059] Step b, adding 0.03% kerosene and 0.01% camphor oil by weight of the negative electrode waste slurry to the broken gel slurry, stirring at 80 r / min for 2 h to obtain a mixed slurry;

[0060] Step c, filtering the mixed slurry through a 10000 mesh filter cloth to obtain a filter residue and a filtrate; finely filtering the obtained filtrate through a 15000 mesh filter cloth to obtain an organic solvent, and combining the filter residues;

[0061] Step d, washing the filter residue with deionized water and ethanol four times in sequence, heating the washed filter residue to 1000° C. at a rate of 200° C. / s, and calcining for 10 min to obtain a regenerated negative electrode material.

[0062] The purity of the regenerated negative electrode materials obtained in Examples 1 to 3 is ≥99%, and the total recovery rate of graphite and conductive carbon is 98% to 99%.

[0063] Comparative Example 1

[0064] This comparative example provides a method for regenerating waste negative electrode slurry of a lithium ion battery. The only difference from Example 1 is that a sulfuric acid solution with a mass concentration of 98% is added in step a. The specific steps are as follows:

[0065] Step a, transferring the collected lithium-ion battery negative electrode waste slurry into a container, adding a 98% sulfuric acid solution with a mass concentration of 0.8% of the negative electrode waste slurry, stirring and breaking the gel at 40 r / min for 1.5 hours to obtain a broken gel slurry;

[0066] Step b, adding 0.02% kerosene and 0.02% pine oil by weight of the negative electrode waste slurry to the debonding slurry, stirring at 70 r / min for 2.5 h to obtain a mixed slurry;

[0067] Step c, filtering the mixed slurry through a 10000 mesh filter cloth to obtain a filter residue and a filtrate; finely filtering the obtained filtrate through a 20000 mesh filter cloth to obtain an organic solvent, and combining the filter residues;

[0068] Step d, washing the filter residue with deionized water and ethanol four times in sequence, heating the washed filter residue to 1100° C. at a rate of 200° C. / s, and calcining for 8 minutes to obtain a regenerated negative electrode material.

[0069] The SEM images of the regenerated negative electrode materials prepared in this comparative example and Example 1 are as follows Figure 2~Figure 3 As shown in the figure, it can be seen that the structures of graphite and conductive carbon in the regenerated negative electrode material recovered in Example 1 are not destroyed, while the structures of graphite and conductive carbon in the regenerated negative electrode material recovered in Comparative Example 1 are obviously irregular, and there are also some tiny impurities, which is mainly caused by the destruction of the structures of graphite and conductive carbon.

[0070] Comparative Example 2

[0071] This comparative example provides a method for regenerating waste slurry of negative electrodes of lithium-ion batteries. The only difference from Example 1 is that no foaming agent is added in step b. The specific steps are as follows:

[0072] Step a, transferring the collected lithium-ion battery negative electrode waste slurry into a container, adding 0.8% oxalic acid by weight of the negative electrode waste slurry, stirring and breaking the gel at 40 r / min for 1.5 h to obtain a broken gel slurry;

[0073] Step b, adding kerosene in an amount of 0.02% by mass of the negative electrode waste slurry to the debonding slurry, stirring at 70 r / min for 2.5 h to obtain a mixed slurry;

[0074] Step c, filtering the mixed slurry through a 10000 mesh filter cloth to obtain a filter residue and a filtrate; finely filtering the obtained filtrate through a 20000 mesh filter cloth to obtain an organic solvent, and combining the filter residues;

[0075] Step d, washing the filter residue with deionized water and ethanol four times in sequence, heating the washed filter residue to 1100° C. at a rate of 200° C. / s, and calcining for 8 minutes to obtain a regenerated negative electrode material.

[0076] The purity of the regenerated negative electrode material recovered in this comparative example is 98%, and the total recovery rate of graphite and conductive carbon is 86%, and the recovery rate is significantly reduced.

[0077] Comparative Example 3

[0078] This comparative example provides a method for regenerating waste slurry of negative electrodes of lithium ion batteries. The only difference from Example 1 is that the foaming agent in step b is replaced by an ionic foaming agent, sodium oleate. The specific steps are as follows:

[0079] Step a, transferring the collected lithium-ion battery negative electrode waste slurry into a container, adding 0.8% oxalic acid by weight of the negative electrode waste slurry, stirring and breaking the gel at 40 r / min for 1.5 h to obtain a broken gel slurry;

[0080] Step b, adding 0.02% kerosene and 0.02% sodium oleate by weight of the negative electrode waste slurry to the debonding slurry, stirring at 70 r / min for 2.5 h to obtain a mixed slurry;

[0081] Step c, filtering the mixed slurry through a 10000 mesh filter cloth to obtain a filter residue and a filtrate; finely filtering the obtained filtrate through a 20000 mesh filter cloth to obtain an organic solvent, and combining the filter residues;

[0082] Step d, washing the filter residue with deionized water and ethanol four times in sequence, heating the washed filter residue to 1100° C. at a rate of 200° C. / s, and calcining for 8 minutes to obtain a regenerated negative electrode material.

[0083] The purity of the regenerated negative electrode material recovered in this comparative example is 85%. When sodium oleate is used as a foaming agent, a large amount of inorganic matter remains on the surface of the negative electrode material during the heat treatment of the recovered material, which has a very important influence on the purity of the material. The total recovery rate of graphite and conductive carbon is 97%.

[0084] In summary, the present invention provides a method for recycling waste negative electrode slurry of lithium-ion batteries with simple steps, low energy consumption and no damage to the material structure, which realizes the high-value utilization of the waste slurry, has high environmental and economic benefits, and has high value for promotion and application.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for regenerating waste negative electrode slurry of lithium ion batteries, characterized in that: The steps include: Step a, adding an organic acid to the negative electrode waste slurry of the lithium ion battery for stirring and breaking the gel to obtain a broken gel slurry; the amount of the organic acid added is 0.5% to 1% of the mass of the negative electrode waste slurry; the stirring and breaking speed is 30r / min to 50r / min, and the stirring and breaking time is 1h to 2h; Step b, adding an oil collector and a non-ionic foaming agent to the debonding slurry, and mixing them evenly to obtain a mixed slurry; Step c, filtering the mixed slurry through a multi-stage precision filtration system with successively decreasing pore sizes to obtain a filtrate and a filter residue, washing the filter residue, and then calcining it at a high temperature to obtain a regenerated negative electrode material; wherein the pore size of the precision filtration system is ≥8000 mesh.

2. The method for regenerating waste negative electrode slurry of lithium ion batteries according to claim 1, characterized in that: In step a, the organic acid is one or more of formic acid, oxalic acid or succinic acid.

3. The method for regenerating waste negative electrode slurry of lithium ion batteries according to claim 1, characterized in that: In step b, the oil collector is one or both of kerosene and diesel.

4. The method for regenerating waste negative electrode slurry of a lithium ion battery according to claim 1 or 3, characterized in that: In step b, the amount of the oil collector added is 0.01% to 0.03% of the mass of the negative electrode waste slurry.

5. The method for regenerating waste negative electrode slurry of lithium ion batteries according to claim 1, characterized in that: In step b, the nonionic foaming agent is one or more of 2# oil, 4# oil, pine oil, cresol or camphor oil.

6. The method for regenerating waste negative electrode slurry of lithium ion batteries according to claim 1 or 5, characterized in that: In step b, the amount of the non-ionic foaming agent added is 0.01% to 0.03% of the mass of the negative electrode waste slurry.

7. The method for regenerating waste negative electrode slurry of lithium ion batteries according to claim 1, characterized in that: In step c, the multi-stage precision filtration system is a two-stage filtration system, wherein the aperture of the first-stage filtration system is 8000 mesh to 10000 mesh, and the aperture of the second-stage filtration system is 15000 mesh to 20000 mesh; and / or In step c, the washing specifically comprises: washing with water and organic alcohol in sequence, and the number of washing times is ≥3.

8. The method for regenerating waste negative electrode slurry of lithium ion batteries according to claim 1 or 7, characterized in that: In step c, the calcination temperature is 1000° C. to 1200° C., and the calcination time is 5 min to 10 min.

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