Utilization method of tailings in dry-method membrane preparation

Abstract

The invention relates to a method for utilizing tailings in a dry-method membrane, relates to the technical field of batteries, and is used for solving at least one of the problems of poor uniformity, continuous generation of more new tailings, low utilization rate of the tailings and the like of a membrane prepared from the recycled tailings in the prior art. The tailings are recycled and located on the two sides of the membrane, after the membrane is machined, the tailings on the two sides can be cut according to needs, and it is guaranteed that almost all the prepared membranes are dry mixed materials. After being cut, the tailings on the two sides can be recycled and used as raw materials for cutting parts on the two sides of the diaphragm in the next production process, so that the generation of the tailings is reduced, the diaphragm is basically made of dry mixed materials, and the uniformity of the diaphragm is good.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a method for utilizing waste materials in dry film forming. Background Technology

[0002] Currently, the production of functional membranes for energy storage devices mainly adopts two technical routes: wet process and dry process. The wet process involves mixing binder, active material and solvent to form a slurry, which is then coated onto the current collector and dried to form a film; while the dry process involves directly dry mixing binder and active components, forming a film layer through a rolling process, and then laminating it with the current collector.

[0003] In dry processing, due to the differences in the flowability of dry-mixed powders, it is difficult to keep the edges of the self-supporting dry film flat, requiring edge trimming before winding. This process typically generates 5%-15% of the total raw material waste, resulting in significant material loss and resource waste.

[0004] CN114434840A discloses a method for recycling tailings from self-supporting dry functional membranes. This method mixes tailings with dry-mix powder to obtain a mixture, which is then used to form the middle section of a membrane. The two sides of the membrane consist of the dry-mix powder, meaning the prepared membrane has virgin material on both sides and tailings mixed in the middle. This method effectively recycles tailings while ensuring the self-supporting dry functional membrane meets the requirements of the membrane production process, as well as mechanical and electrical properties, thus contributing to resource conservation and environmental protection. However, the membrane prepared by this method contains both virgin material (dry-mix powder) and tailings. Since the virgin material has better film-forming and processing properties than the tailings, it is difficult to guarantee the uniformity of the membrane. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a method for utilizing waste materials in dry film production, in order to solve at least one of the problems in the prior art, such as poor uniformity of film sheets made by using recycled waste materials, continuous generation of more new waste materials, and low utilization rate of waste materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for utilizing waste material in dry film production includes the following steps:

[0008] (1) The tailings are crushed to obtain tailings powder;

[0009] (2) The tailing powder and dry mixed powder are respectively fed to the two sides and the middle position of the calendering roller. After calendering, a film primary product with dry mixed powder in the middle and tailing powder on both sides is obtained.

[0010] (3) Cut off the tail powder portion on both sides of the initial membrane product to obtain the finished membrane product.

[0011] Furthermore, in step (1), the fineness of the tailings powder is 18 mesh to 2000 mesh.

[0012] Furthermore, in step (2), the calendering process uses an apparatus including multiple calendering rolls and a feeding device, with a feeding area formed between two adjacent calendering rolls, and the feeding device extending into the feeding area; the feeding device includes a first tail material baffle, a first powder baffle, a second powder baffle, and a second tail material baffle arranged in sequence.

[0013] The channel formed between the first tail material baffle and the first powder baffle is used to transport the tail material powder.

[0014] The channel formed between the first powder baffle and the second powder baffle is used to transport the dry-mixed powder;

[0015] The channel formed between the second powder baffle and the second tail material baffle is used to transport the tail material powder.

[0016] Furthermore, the distance between the first tail material baffle and the second tail material baffle is D1, the distance between the first tail material baffle and the first powder baffle is D2, and the distance between the second powder baffle and the second tail material baffle is D3. Then, D2:D1 = 0.02~0.1:1, and D3:D1 = 0.02~0.1:1.

[0017] Furthermore, along the feeding direction, the first tail material baffle extends to a depth of H1 in the feeding area, the first powder baffle extends to a depth of H2 in the feeding area, the second powder baffle extends to a depth of H4 in the feeding area, and the second tail material baffle extends to a depth of H3 in the feeding area.

[0018] Then H2:H1 = 1.05 to 1.3:1, H4:H3 = 1.05 to 1.3:1.

[0019] Furthermore, the mass of tail material added between the first tail material baffle and the first powder baffle is the same as the mass of tail material added between the second powder baffle and the second tail material baffle, both being M1. The mass of dry mixed powder added between the first powder baffle and the second powder baffle is M2. Therefore, M1:M2 = 0.1~0.2:1.

[0020] Furthermore, in step (2), the calendering is performed using 3 to 5 grade rollers.

[0021] Furthermore, in step (2), the D50 of the dry-mixed powder is 4 to 15 μm.

[0022] Furthermore, in step (2), during the calendering process, the feeding speed of the tailing powder and the dry mixed powder is the same, which is 1 to 3 kg / min.

[0023] Furthermore, in step (3), the cutting involves cutting off the tail material on both sides of the membrane to ensure that the final membrane product is made entirely of new material.

[0024] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0025] 1. This invention recycles and reuses the waste material located on both sides of the membrane. After the membrane is processed, the waste material on both sides can be cut off as needed, ensuring that the prepared membrane is almost entirely dry-mixed material. The waste material on both sides can also be recycled after cutting and used as raw material for the next production of the membrane, thereby reducing the generation of waste material. The membrane is basically made of dry-mixed material, resulting in better membrane uniformity.

[0026] 2. The low-particle-size dry-mixed powder material of this invention is prone to over-pressing during dry calendering, making continuous film formation impossible. Furthermore, the low-particle-size dry-mixed powder material has poor flowability during calendering, failing to fully contact the tailings powder, resulting in gaps or a loose interface between the two powders. This necessitates the cutter moving further inwards during edge trimming, increasing the amount of waste material in the dry-mixed electrode sheet. Conversely, the high-particle-size dry-mixed material, when calendered, makes it difficult to improve electrode compaction, reducing electrochemical performance. Moreover, the high flowability and ductility of the high-particle-size dry-mixed material during calendering cause the width of the dry-mixed electrode sheet to exceed the preset range, increasing edge trimming waste.

[0027] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0028] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0029] Figure 1 This is a front view of the apparatus used in the calendering process of the present invention;

[0030] Figure 2 This is a top view of the apparatus used in the calendering process of the present invention.

[0031] Figure label:

[0032] 1-First tail material baffle, 2-First powder baffle, 3-Second powder baffle, 4-Second tail material baffle. Detailed Implementation

[0033] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0034] A specific embodiment of the present invention discloses a method for utilizing waste material in dry film production, comprising the following steps:

[0035] (1) The tailings are crushed to obtain tailings powder;

[0036] (2) The tailing powder and dry mixed powder are respectively fed to the two sides and the middle position of the calendering roller. After calendering, a film primary product with dry mixed powder in the middle and tailing powder on both sides is obtained.

[0037] (3) Cut off the tail powder portion on both sides of the initial membrane product to obtain the finished membrane product.

[0038] Compared with existing technologies, this invention recycles and reuses the waste material located on both sides of the membrane. After the membrane is processed, the waste material on both sides can be cut off as needed, ensuring that the prepared membrane is almost entirely dry-mixed material. The waste material on both sides can also be recycled after cutting and used as raw material for the cut parts of the membrane in the next production, thereby reducing the generation of waste material. The membrane is basically made of dry-mixed material, resulting in better membrane uniformity.

[0039] It should be noted that the dry-mixed powder in this invention is the new material, which usually includes active materials, binders and additives. The tailings are the edge material removed after the dry-mixed powder has undergone one or more calendering and trimming processes.

[0040] Specifically, in step (1), the fineness of the tailing powder is 18 mesh to 2000 mesh, for example, 18 mesh, 100 mesh, 200 mesh, 300 mesh, 400 mesh, 500 mesh, 600 mesh, 700 mesh, 800 mesh, 900 mesh, 1000 mesh, 1100 mesh, 1200 mesh, 1300 mesh, 1400 mesh, 1500 mesh, 1600 mesh, 1700 mesh, 1800 mesh, 1900 mesh, and 2000 mesh.

[0041] It should be noted that if the powder fineness is too high, it is prone to clumping, which can cause material jamming during calendering and result in a lack of continuity in film formation. If the fineness is too low, a finer mesh screen is required, but the fine mesh screen will damage the degree of fibrosis and reduce the cohesion of the electrode.

[0042] Specifically, such as Figure 1 and 2As shown, in step (2), the calendering process uses a device that includes multiple calendering rolls and a feeding device. A feeding area is formed between two adjacent calendering rolls, and the feeding device extends to the feeding area. The feeding device includes a first tail material baffle 1, a first powder baffle 2, a second powder baffle 3, and a second tail material baffle 4 arranged in sequence.

[0043] The channel formed between the first tail material baffle 1 and the first powder baffle 2 is used to transport the tail material powder.

[0044] The channel formed between the first powder baffle 2 and the second powder baffle 3 is used to transport the dry mixed powder;

[0045] The channel formed between the second powder baffle 3 and the second tail material baffle 4 is used to transport the tail material powder.

[0046] Specifically, such as Figure 2 As shown, the distance between the first tail material baffle 1 and the second tail material baffle 4 is D1, the distance between the first tail material baffle 1 and the first powder baffle 2 is D2, and the distance between the second powder baffle 3 and the second tail material baffle 4 is D3. Then, D2:D1 = 0.02 to 0.1:1, for example, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, and D3:D1 = 0.02 to 0.1:1, for example, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1.

[0047] It should be noted that D2 and D3 refer to the feed width of the tailings powder. If the tailings width is too high, the pressure exerted on the virgin material film-forming area during calendering will be excessive, exacerbating the extension of the tailings into the virgin material film-forming area during calendering. This will make it impossible to eliminate the impact of the tailings on the final film. If the tailings width is too low, it will not be able to prevent the extrusion of the virgin material during calendering, ultimately leading to an increase in the amount of tailings generated from the virgin material.

[0048] Specifically, such as Figure 1 As shown, along the feeding direction, the first tail material baffle 1 extends to a depth of H1 in the feeding area, the first powder baffle 2 extends to a depth of H2 in the feeding area, the second powder baffle 3 extends to a depth of H4 in the feeding area, and the second tail material baffle 4 extends to a depth of H3 in the feeding area.

[0049] Then H2:H1 = 1.05 to 1.3:1, for example, 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1; H4:H3 = 1.05 to 1.3:1, for example, 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1.

[0050] It should be noted that H2 and H4 are both virgin material baffles. If the height of H2 and H4 is too low, the tail material powder will flow more towards the virgin material film-forming area during calendering due to the obstruction of the baffles, thus making it impossible to remove the tail material in the final electrode sheet. If the height of H2 and H4 is too high, the tail material will flow more easily towards the tail material baffle side during calendering, failing to stop the flow of virgin material during film formation, resulting in an increase in the tail material generated after the final virgin material film is formed.

[0051] Specifically, the mass of tail material added between the first tail material baffle 1 and the first powder baffle 2 is the same as the mass of tail material added between the second powder baffle 3 and the second tail material baffle 4, both being M1. The mass of dry mixture powder added between the first powder baffle 2 and the second powder baffle 3 is M2. Then M1:M2 = 0.1 to 0.2:1, for example, 0.1:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1, 0.2:1.

[0052] It should be noted that this invention requires controlling the quality of the tailings powder feeding. This is mainly because the tailings powder itself has higher compaction and lower flowability during calendering compared to the virgin material. This reduces burrs generated when the virgin material forms a film and decreases the amount of tailings generated from trimming. An excessively high proportion will cause the tailings to flow into the dry-mixed powder area during film formation, resulting in an excessively high proportion of waste tailings in the final film, affecting electrode performance. Conversely, an excessively low proportion will fail to prevent the virgin material from extending into the tailings powder area, leading to an increased proportion of tailings generated from the virgin material.

[0053] Specifically, in step (2), the D50 of the dry mixed powder is 4 to 15 μm, for example, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm.

[0054] Low-particle-size dry-blended powder materials are prone to over-pressing during dry calendering, making continuous film formation impossible. Furthermore, their poor flowability during calendering prevents sufficient contact with the tailing powder, resulting in gaps or a loose interface between the two materials. This necessitates the cutter moving further inwards during edge trimming, increasing waste material in the dry-blended electrode. Conversely, high-particle-size dry-blended materials are difficult to compact during calendering, reducing electrochemical performance. Their high flowability and ductility during calendering cause the electrode width to exceed the preset range, increasing edge trimming waste.

[0055] Specifically, in step (2), the calendering is performed using 3 to 5 (e.g., 1, 2, 3) grade rollers.

[0056] Specifically, in step (2), during the calendering process, the feeding speed of the tail powder and the dry mixed powder is the same, which is 1 to 3 kg / min, for example, 1 kg / min, 1.2 kg / min, 1.4 kg / min, 1.6 kg / min, 1.8 kg / min, 2 kg / min, 2.2 kg / min, 2.4 kg / min, 2.6 kg / min, 2.8 kg / min, and 3 kg / min.

[0057] It should be noted that feeding speeds below the acceptable range will cause feeding delays, leading to localized material shortages during calendering. Feeding speeds that are too high will cause material accumulation, compaction, and agglomeration, clogging the roller gaps.

[0058] It should be noted that in step (3), cutting means cutting off the tail material on both sides of the membrane to ensure that the final membrane product is made of new material.

[0059] The technical solution of the present invention will be further explained below with reference to specific embodiments.

[0060] In the following examples, the dry mix and tailings have the same composition. The tailings are the edge material removed after one or more calendering and trimming processes of the dry mix. In the following examples and Comparative Example 1, the tailings have graphite as the main active material and a tap density of 1.2 g / cm³. 3 The average particle size (D50) is 12.5 μm, the main active material in the dry-mixed powder is graphite, and the tap density is 1.2 g / cm³. 3 The invention is illustrated by example, but is not limited thereto.

[0061] Example 1

[0062] This embodiment of a method for utilizing waste material in dry film production includes the following steps:

[0063] (1) The tailings are crushed to obtain tailings powder with a fineness of 100 mesh;

[0064] (2) The tailing powder and the dry mixed powder with D50 of 8μm are respectively fed to the two sides and the middle position of the calendering roller. After calendering, a film primary product with dry mixed powder in the middle and tailing powder on both sides is obtained.

[0065] Specifically, the calendering process uses an apparatus including multiple calendering rolls and a feeding device, with a feeding area formed between two adjacent calendering rolls, and the feeding device extending into the feeding area; the feeding device includes a first tail material baffle 1, a first powder baffle 2, a second powder baffle 3, and a second tail material baffle 4 arranged in sequence.

[0066] The channel formed between the first tail material baffle 1 and the first powder baffle 2 is used to transport the tail material powder.

[0067] The channel formed between the first powder baffle 2 and the second powder baffle 3 is used to transport the dry mixed powder;

[0068] The channel formed between the second powder baffle 3 and the second tail material baffle 4 is used to transport the tail material powder;

[0069] The distance between the first tail material baffle 1 and the second tail material baffle 4 is D1, the distance between the first tail material baffle 1 and the first powder baffle 2 is D2, and the distance between the second powder baffle 3 and the second tail material baffle 4 is D3. Then D2:D1 = 0.02:1, D3:D1 = 0.02:1.

[0070] Along the feeding direction, the first tail material baffle 1 extends to a depth of H1 in the feeding area, the first powder baffle 2 extends to a depth of H2 in the feeding area, the second powder baffle 3 extends to a depth of H4 in the feeding area, and the second tail material baffle 4 extends to a depth of H3 in the feeding area; then H2:H1 = 1.05:1, H4:H3 = 1.05:1;

[0071] The mass of tail material added between the first tail material baffle 1 and the first powder baffle 2 is the same as the mass of tail material added between the second powder baffle 3 and the second tail material baffle 4, both being M1. The mass of dry mixed powder added between the first powder baffle 2 and the second powder baffle 3 is M2. Therefore, M1:M2=0.1:1.

[0072] The calendering process employs a five-stage rolling process, with the linear speed ratio of the five rollers being 1:2.3:1.9:1.8:1.

[0073] The feeding rate of the tailing powder and the dry mixed powder is the same, which is 1 kg / min.

[0074] (3) Cut off the tail powder portion on both sides of the initial membrane product to obtain the finished membrane product.

[0075] Example 2

[0076] The method for utilizing tailings in a dry film-making process in this embodiment is similar to that in embodiment 1, except that in step (1), the fineness of the tailings powder is 1000 mesh.

[0077] In step (2), D2:D1 = 0.06:1, D3:D1 = 0.06:1; H2:H1 = 1.175:1, H4:H3 = 1.175:1; M1:M2 = 0.15:1;

[0078] The calendering process employs a five-stage roller pressing method, with the five rollers having a linear speed ratio of 1:1.9:1.7:1.6:1. The feeding speed of the tailing powder and the dry-mixed powder is the same, both being 2 kg / min.

[0079] Example 3

[0080] The method for utilizing tailings in a dry film-making process in this embodiment is similar to that in embodiment 1, except that in step (1), the fineness of the tailings powder is 1000 mesh.

[0081] In step (2), D2:D1 = 0.1:1, D3:D1 = 0.1:1; H2:H1 = 1.3:1, H4:H3 = 1.3:1; M1:M2 = 0.2:1;

[0082] The calendering process employs a five-stage rolling process, with the linear speed ratio of the five rollers being 1:3:1.4:1.2:1.

[0083] The feeding rate of the tailing powder and the dry mixed powder is the same, which is 3 kg / min.

[0084] Comparative Example 1

[0085] The method for utilizing tailings in dry film making in this embodiment is similar to that in embodiment 1, except that in step (2), D2:D1 = 0.2:1 and D3:D1 = 0.2:1.

[0086] Comparative Example 2

[0087] The method for utilizing tailings in a dry film-making process in this embodiment is similar to that in embodiment 1, except that in step (2), H2:H1 = 1.4:1 and H4:H3 = 1.4:1.

[0088] Comparative Example 3

[0089] The method for utilizing tailings in a dry film-making process in this embodiment is similar to that in embodiment 1, except that in step (2), M1:M2 = 0.3:1.

[0090] Comparative Example 4

[0091] The method for utilizing tailings in a dry film-making process in this embodiment is similar to that in embodiment 1, except that in step (2), the calendering process is performed by directly calendering the film using a pair of rollers.

[0092] Comparative Example 5

[0093] The method for utilizing tailings in a dry film-making process in this embodiment is similar to that in embodiment 1, except that in step (2), during the calendering process, the feeding speed of the tailings powder and the dry mixed powder is the same, which is 5 kg / min.

[0094] Experimental Example 1

[0095] The thickness and areal density of the membrane products obtained by the methods in Examples 1-3 and Comparative Examples 1-5 were tested respectively, and the results are shown in Table 1. The thickness and areal density were measured at six different points taken from left to right on the membrane, denoted as 1-6.

[0096] The areal density is calculated by sampling the electrode sheet with a sampler, measuring the sample mass, and dividing by the area. Uniformity is calculated by dividing the overall standard deviation of the areal density or thickness measured at different locations by the average of the areal density or thickness at those locations. The results are shown in Table 1.

[0097] Table 1

[0098]

[0099]

[0100] As shown in Table 1, the film thickness uniformity of the film prepared by the method of the present invention is 0.86-2.22%, and the areal density uniformity is 1.41-2.36%.

[0101] Compared with Example 1, the unsuitable ratio of D, H and M in Comparative Examples 1-3 will affect the degree of extension of the tail powder into the dry mixture powder, which will easily lead to large differences in the extension of powder at different depths, affecting the quality of the final membrane near the interface of the two powders. Therefore, compared with Example 1, the uniformity of the membranes in Comparative Examples 1-3 will be worse.

[0102] Compared with Example 1, the uniformity of the film prepared by one-pass calendering in Comparative Example 5 was reduced.

[0103] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for utilizing waste material in dry film production, characterized in that, Includes the following steps: (1) The tailings are crushed to obtain tailings powder; (2) The tailing powder and dry mixed powder are respectively fed to the two sides and the middle position of the calendering roller. After calendering, a film primary product with dry mixed powder in the middle and tailing powder on both sides is obtained. (3) Cut off the tail powder portion on both sides of the initial membrane product to obtain the finished membrane product.

2. The method for utilizing waste material in dry film production according to claim 1, characterized in that, In step (1), the fineness of the tailing powder is 18 mesh to 2000 mesh.

3. The method for utilizing waste material in dry film production according to claim 1, characterized in that, In step (2), the calendering process uses an apparatus including multiple calendering rolls and a feeding device, with a feeding area formed between two adjacent calendering rolls, and the feeding device extending into the feeding area; the feeding device includes a first tail material baffle, a first powder baffle, a second powder baffle, and a second tail material baffle arranged in sequence. The channel formed between the first tail material baffle and the first powder baffle is used to transport the tail material powder. The channel formed between the first powder baffle and the second powder baffle is used to transport the dry-mixed powder; The channel formed between the second powder baffle and the second tail material baffle is used to transport the tail material powder.

4. The method for utilizing waste material in dry film production according to claim 3, characterized in that, The distance between the first tail material baffle and the second tail material baffle is D1, the distance between the first tail material baffle and the first powder baffle is D2, and the distance between the second powder baffle and the second tail material baffle is D3. Then, D2:D1 = 0.02~0.1:1, and D3:D1 = 0.02~0.1:

1.

5. The method for utilizing waste material in dry film production according to claim 3, characterized in that, Along the feeding direction, the first tail material baffle extends to a depth of H1 in the feeding area, the first powder baffle extends to a depth of H2 in the feeding area, the second powder baffle extends to a depth of H4 in the feeding area, and the second tail material baffle extends to a depth of H3 in the feeding area. Then H2:H1 = 1.05 to 1.3:1, H4:H3 = 1.05 to 1.3:

1.

6. The method for utilizing waste material in dry film production according to claim 3, characterized in that, The mass of tail material added between the first tail material baffle and the first powder baffle is the same as the mass of tail material added between the second powder baffle and the second tail material baffle, both being M1. The mass of dry mixed powder added between the first powder baffle and the second powder baffle is M2. Therefore, M1:M2 = 0.1~0.2:

1.

7. The method for utilizing waste material in dry film production according to claim 3, characterized in that, In step (2), the calendering is performed using 3 to 5 grade rollers.

8. A method for utilizing waste material in dry film production according to any one of claims 1-7, characterized in that, In step (2), the D50 of the dry-mixed powder is 4 to 15 μm.

9. A method for utilizing waste material in dry film production according to any one of claims 1-7, characterized in that, In step (2), during the calendering process, the feeding speed of the tailing powder and the dry mixed powder is the same, which is 1 to 3 kg / min.

10. A method for utilizing waste material in dry film production according to claims 1-7, characterized in that, In step (3), cutting involves cutting off the tail material on both sides of the membrane to ensure that the final membrane product is made entirely of new material.

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