A flexible self-supporting thick electrode green sheet forming process

Abstract

This invention discloses a flexible self-supporting thick electrode preform film forming process. The electrode material is formed using three sets of rollers (A, B, and C) arranged in an inverted triangle on an open mill. The mixed, blocky agglomerated material first enters rollers A and B for initial pressing, then passes through rollers B and C for further pressing. This process is repeated multiple times until the material is finally pressed through rollers A and C before exiting. The spacing between rollers A, B, and C can be adjusted independently, and each roller operates independently without interference. This flexible self-supporting thick electrode preform film forming process, based on the characteristics of existing electrode materials, especially the characteristics of the agglomerated material after mixing, addresses the inability to form agglomerated materials. Through optimization of the forming process, breakthrough improvements have been made in several aspects, including frequency, number of open mill cycles, stacking method, and feeding method, thereby improving the electrochemical performance of the electrode and obtaining an electrode with uniform hardness, thickness, and density.

Description

Technical Field

[0001] This invention relates to a process for forming flexible self-supporting thick electrode preform films. Background Technology

[0002] Open mixing was initially used in the plastics industry. The open mixing mill, located before the calender and after the mixer, functions to mix and plasticize the homogeneous raw materials, providing a more uniformly mixed molten material for the calender to shape the plastic products. In existing technologies, to meet the open mixing and plasticizing requirements of the rubber industry, it is necessary to melt the plastic particles through methods such as temperature control, and the proportion of plastic particles is very high. However, the mixture in porous flexible self-supporting thick electrodes consists of ceramic powder and binder, which differs significantly from plastic particles. The existing open mixing process has completely different compatibility with ceramic powders, making it difficult to directly apply to flexible self-supporting thick electrode preforms. Summary of the Invention

[0003] The purpose of this invention is to overcome the defects of the prior art and provide a flexible self-supporting thick electrode preform film forming process. Based on the characteristics of existing electrode materials, especially the characteristics of the material clumps after the mixing process, which cannot be clumped together, the invention optimizes the open milling process and makes breakthrough improvements from several aspects such as frequency, number of open milling cycles, stacking method, and feeding method, thereby improving the electrochemical performance of the electrode and obtaining an electrode with uniform hardness, thickness, and density.

[0004] The technical solution to achieve the above objective is: a flexible self-supporting thick electrode preform film forming process, which uses three sets of rollers A, B, and C arranged in an inverted triangle on an open mill to complete the forming of the electrode material, specifically including the following steps:

[0005] S1, the mixed aqueous ion battery agglomerate material is fed into the buffer silo by screw feeding or vibration feeding, and enters the space between roller group A and roller group B from the lower outlet of the buffer silo;

[0006] S2, the rollers of group A and group B use equal speed or differential speed to initially roll and shape the colloid material before entering the next rolling step;

[0007] S3, by controlling the rotation direction of roller group C, the colloid material is fed in along the gap between roller group B and roller group C; the gap between roller group B and roller group C is set to be less than or equal to the gap between roller group A and roller group B, and roller group B and roller group C are rolled at the same speed or differential speed to obtain the preliminary rolled electrode blank film, which is discharged from the first discharge platform;

[0008] S4. Based on the preform forming condition of the colloid material, if the colloid forming strength is low and the mass thickness distribution is uneven, the electrode preform film that has been initially rolled from the first discharge platform will be fed from the feeding platform between rollers A and rollers B. Steps S2 and S3 will be repeated until the mechanical strength and mass thickness of the obtained electrode preform film meet the design requirements.

[0009] S5. After completing the final roll forming step to obtain an electrode blank film that meets the design requirements, the electrode blank film that meets the design requirements enters between roller group A and roller group C. Roller group A and roller group C are rolled at the same speed. The distance between roller group A and roller group C is controlled for final forming and finishing, and the film is discharged from the second discharge platform, completing the open mill process of electrode blank film production.

[0010] In the above-mentioned flexible self-supporting thick electrode preform film forming process, in step S2, the rollers of group A and group B are rolled in a differential speed manner, and the ratio of their linear speeds is between 0.8 and 1.

[0011] In the above-mentioned flexible self-supporting thick electrode preform film forming process, the interior of each set of rollers is hollow, and a heating medium is installed inside each set of rollers. The temperature of the rollers is controlled at 60-120℃ by external circulation heating.

[0012] The above-mentioned flexible self-supporting thick electrode blank film forming process includes rollers made of 42CrMo forged alloy steel, with each roller surface treated with sandblasting and patterning. The roller diameter is 100-500mm, and the effective width is 50-1000mm. The roller surface hardness is HRC 40-70°, with a single-sided hardness layer of more than 3mm. The roller cylindricity is ±0.008mm, and the roller diameter runout is ±0.008mm. The spacing between any two rollers can be adjusted from 0 to 50mm, the travel speed of each roller is 0-10m / min, and the pressure between any two rollers is 0-10T.

[0013] In the above-mentioned flexible self-supporting thick electrode blank film forming process, the roller surfaces of each group of rollers are chrome-plated, and the thickness of the chrome plating layer on one side is 0.1mm.

[0014] In the above-mentioned flexible self-supporting thick electrode preform film forming process, the diameter of each group of rollers is 200mm, the effective width of the rollers is 500mm, and the surface hardness of the rollers is HRC 60°.

[0015] In the above-mentioned flexible self-supporting thick electrode blank film forming process, during the open milling process, the open mill uses a grating ruler digital display as a reference and a servo electric steel pitch adjustment and pressure sensor matched with a grating ruler thickness gauge to adjust the thickness of both sides of the electrode blank film product in real time.

[0016] The above-mentioned flexible self-supporting thick electrode preform film forming process, wherein the colloidal material is composed of ceramic powder, conductive agent, binder and solvent, the mass ratio of ceramic powder to conductive agent is (80-90):(20-10), and the content of binder is 2-15 wt.% of the mixed powder.

[0017] In the above-mentioned flexible self-supporting thick electrode preform film forming process, when the electrode is a positive electrode, the ceramic powder is at least one of manganese-based oxide, polyanionic material and Prussian blue analog; when the electrode is a negative electrode, the ceramic powder is at least one of NASICON-type phosphate compound, metal oxide, activated carbon and Prussian blue analog.

[0018] The conductive agent is an inorganic carbon source, and at least one of artificial graphite, natural graphite, activated carbon, graphene, carbon black, carbon nanotubes and mesoporous carbon is used.

[0019] The adhesive is a polytetrafluoroethylene emulsion with a solid content of 60±2wt%.

[0020] In the above-mentioned flexible self-supporting thick electrode preform film forming process, the manganese-based oxide includes MnO2 and Na. X MnO2 and KxMnO2;

[0021] The chemical formula of the polyanionic material is NaxMy(XO4)n, where M is a transition metal Fe, Mn, Ni, Cu or V, and X is a compound containing tetrahedral or octahedral anionic structural units of S, P, Si, Mo or As.

[0022] The Prussian blue analogue is NaMFe(CN)6, wherein M is Ni, Co, Fe or Cu;

[0023] The NASICON-type phosphate compound is NaTi2(PO4)3 or Na3V2(PO4)3;

[0024] The metal oxide is MoO3 or Na2V6O. 16 .

[0025] The flexible self-supporting thick electrode preform film forming process of the present invention, based on the characteristics of existing electrode materials, especially the characteristics of the material clumps after the mixing process, which cannot be clumped, has made breakthrough improvements in several aspects such as frequency, number of times of open milling, stacking method and feeding method through optimization of the open milling process, thereby improving the electrochemical performance of the electrode and obtaining an electrode with uniform hardness, thickness and density. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the open mill used in the flexible self-supporting thick electrode preform film forming process of the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solution of the present invention, its specific embodiments are described in detail below with reference to the accompanying drawings:

[0028] Please see Figure 1 In the preferred embodiment of the present invention, a flexible self-supporting thick electrode preform film forming process is provided, in which the electrode material is formed by three sets of rollers (A, B, and C) arranged in an inverted triangle on an open mill. Rollers A and B are arranged parallel to each other directly below the buffer hopper 2, and roller C is arranged below rollers A and B. A first discharge platform 4 and a second discharge platform 5 are respectively located on both sides of roller C, and a feeding platform 3 is located above rollers A and B.

[0029] The rollers in groups A, B, and C have frosted and textured surfaces to effectively ensure non-slip feeding. The roller diameter ranges from 100 to 500 mm, and the effective width ranges from 50 to 1000 mm. A preferred roller diameter is 200 mm, and the effective width is 500 mm. The surface hardness is HRC 40–70°, preferably 60°. The hardness layer on each side of the roller is at least 3 mm thick. The roller cylindricity is ±0.008 mm. The roller radial runout is ±0.008 mm. The roller surface is chrome-plated with a chrome layer of 0.1 mm on each side.

[0030] The rollers are made of 42CrMo forged alloy steel, which has good strength, toughness, firmness and bending resistance.

[0031] The spacing between any two sets of rollers can be adjusted from 0 to 50 mm, the roller travel speed is adjustable from 0 to 10 m / min, and the pressure between any two sets of rollers is adjustable from 0 to 10 T. The temperature of each roller can be independently controlled, with a temperature control range of 10 to 200℃.

[0032] During the open milling process, the open mill uses a grating ruler digital display as a reference and a servo electric steel pitch adjustment and pressure sensor matched with a grating ruler thickness gauge to adjust the thickness of both sides of the electrode blank film product in real time.

[0033] The first discharge platform 4, the second discharge platform 5, and the feeding platform 3 constitute a conveying platform. Each conveying platform uses active rollers and passive rollers to drive the conveyor belt to convey materials. The rollers of each conveying platform have a diameter of φ40mm and a length of 500mm. The rollers of each conveying platform are chrome-plated. The conveyor belts are made of green PVC or Teflon belts. The conveying motors of each conveying platform are roller motors. The conveying speed is controlled online, and all rollers work together to achieve a uniform speed and prevent material accumulation and pulling.

[0034] The colloidal material consists of ceramic powder, a conductive agent, and a binder. In this embodiment, the ceramic powder is manganese-based oxide (MnO2), the conductive agent is artificial graphite, and the binder is a polytetrafluoroethylene emulsion with a solid content of 60±2wt%. The three components are mixed in a mass ratio of 80:10:10. Deionized water is used as the solvent, and a slurry with a solid content of 50wt% is prepared and mixed into a colloidal material for later use.

[0035] The flexible self-supporting thick electrode preform film forming process of this embodiment specifically includes the following steps:

[0036] S1. First, preheat the three sets of rollers A, B, and C. After reaching the set temperature of 60°C, feed the prepared colloid material into the buffer silo 2 by screw feeding 1. In the buffer silo 2, the material enters from top to bottom between the A set of rollers and the B set of rollers.

[0037] S2, Roll forming is performed between rollers A and rollers B using a 1:1.2 differential speed ratio. Roller A is set to a speed of 1 m / min, roller B is set to a speed of 1.2 m / min, and the distance between rollers A and rollers B is set to 20 mm. The clump material is then fed into the next rolling step.

[0038] S3, by controlling the rotation direction of roller group C, the colloid material is fed in along the gap between roller group B and roller group C. The gap between roller group B and roller group C is set to 10mm. Roller group B and roller group C are set to the same rolling speed of 1.2m / min. The resulting preliminary rolled electrode blank film is discharged from the first discharge platform 4.

[0039] S3, the electrode blank film that has been initially rolled and formed from the first discharge platform 4 is manually transferred to the feeding platform 3, and steps S2 and S3 are repeated for feeding and rolling. The distance between rollers A and rollers B is set to 8mm, and the distance between rollers B and rollers C is set to 6mm. The rolling speed and roller temperature remain unchanged.

[0040] S4. After repeating the rolling process of step S3 three times, adjust the speed of roller group C to 1 m / min and the distance between roller group A and roller group C to 4 mm for final discharge. This yields the open-milled electrode preform film. Five evenly distributed points on the electrode preform film are randomly selected, and cut into 2cm x 15cm pieces. The film's thickness, mass, hardness, and tensile strength are then tested. The results are shown in the table below:

[0041] Table 1, Test Results Table:

[0042] Location Thickness / mm mass / g Hardness / HA Tensile strength / MPa 1 4.02 23.0 41 0.080 2 4.00 22.8 40 0.075 3 4.01 23.1 40 0.078 4 3.99 23.1 42 0.082 5 4.01 22.9 40 0.082

[0043] The flexible self-supporting thick electrode preform film forming process of the present invention improves the process of open milling after slurry agglomeration, including the number of open milling cycles and the frequency of open milling, with the aim of obtaining electrodes with uniform hardness, thickness, and density. This solves the following problems:

[0044] (1) The uniformity of the feed agglomerate material is controlled to ensure the consistency of film formation during the open mill pressing process. The mixed agglomerate material is fed into rollers A and B through screw feeding, vibration discharge, or manual weighing and stacking on the feeding platform for initial pressing. The spacing between rollers A, B, and C can be adjusted independently, and each roller works independently without interfering with the others. Roller A rotates clockwise, roller B rotates counterclockwise, and roller C can rotate clockwise or counterclockwise as needed for discharge. Rollers A, B, and C are made of stainless steel, chrome-plated alloy, etc., and the roller surface is treated with a 0-3mm rough or mirror finish.

[0045] (2) During the electrode open-milling process, rollers A and B travel at different speeds to generate shear stress between and within the colloid material, promoting the fiberization of the PTFE binder, forming a three-dimensional network coating effect, and increasing the mechanical strength of the film. Rollers C can travel at the same speed as rollers A and B, and have a different roller spacing than rollers A and B, allowing the sheared material to be stretched and calendered. Furthermore, depending on the number of open-milling cycles required, the material from the first discharge platform can be repeatedly rolled to fully utilize the binder's properties and achieve the required mechanical strength after plasticization. Then, the second discharge platform is selected for collecting the finished film for the next process. The second discharge platform 5 serves as the finished product discharge area, and the first discharge platform 4 serves as the semi-finished product discharge area, making them less likely to be confused.

[0046] (3) The three sets of rollers A, B and C can be independently temperature controlled to meet the temperature requirements of different forms of adhesive and expand the selectivity of film adhesive.

[0047] In summary, the flexible self-supporting thick electrode preform film forming process of the present invention, based on the characteristics of existing electrode materials, especially the characteristics of the material clumps after the mixing process, which cannot be clumped, has made breakthrough improvements in several aspects such as frequency, number of times of open milling, stacking method, and feeding method through optimization of the open milling process, thereby improving the electrochemical performance of the electrode and obtaining an electrode with uniform hardness, thickness, and density.

[0048] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A flexible self-supporting thick electrode green sheet forming process, characterized by, The electrode material is formed using three sets of rollers (A, B, and C) arranged in an inverted triangle on an open mill. The specific steps include: S1, the mixed aqueous ion battery agglomerate material is fed into the buffer silo using a screw feeder or vibratory feeder, and enters the space between rollers A and rollers B from the lower outlet of the buffer silo; the agglomerate material is composed of ceramic powder, conductive agent, binder and solvent, the mass ratio of ceramic powder to conductive agent is (80~90):(20~10), and the content of binder is 2~15 wt.% of the mixed powder; S2, the rollers of group A and group B use equal speed or differential speed to initially roll and shape the colloid material before entering the next rolling step; the rollers of group A and group B use differential speed to roll and shape the material, and the ratio of their linear speeds is 0.8 to 1; S3, by controlling the rotation direction of roller group C, the colloid material is fed in along the gap between roller group B and roller group C; the gap between roller group B and roller group C is set to be less than or equal to the gap between roller group A and roller group B, and roller group B and roller group C are rolled at the same speed or differential speed to obtain the preliminary rolled electrode blank film, which is discharged from the first discharge platform; S4. Based on the preform forming condition of the colloid material, if the colloid forming strength is insufficient and the mass thickness distribution is uneven, the electrode preform film that has been initially rolled from the first discharge platform will be fed from the feeding platform between rollers A and rollers B. Steps S2 and S3 will be repeated until the mechanical strength and mass thickness of the obtained electrode preform film meet the design requirements. S5. After completing the final roll forming step to obtain an electrode blank film that meets the design requirements, the electrode blank film that meets the design requirements enters between roller group A and roller group C. Roller group A and roller group C are rolled at the same speed. The distance between roller group A and roller group C is controlled for the final forming and finishing, and the film is discharged from the second discharge platform to complete the production of the electrode blank film. Each set of rollers is hollow inside, and each set of rollers is equipped with a heating medium. The temperature of the rollers is controlled at 60~120℃ by external circulation heating. During the open milling process, the open mill uses a grating ruler digital display as a reference, and a servo motor with a pressure sensor matched with a grating ruler thickness gauge to adjust the thickness of both sides of the electrode blank film product in real time.

2. The process for forming a flexible self-supporting thick electrode preform film according to claim 1, characterized in that, Each set of rollers is made of 42CrMo forged alloy steel. The surface of each set of rollers is treated with sandblasting and patterning. The roller diameter is 100~500mm, and the effective width of the roller is 50~1000mm. The surface hardness of the roller is HRC 40~70°, and the hardness layer on one side is more than 3mm. The cylindricity of the roller is ±0.008mm, and the roller diameter runout is ±0.008mm. The distance between any two sets of rollers can be adjusted from 0 to 50mm. The traveling speed of each set of rollers is 0~10m / min, and the pressure between any two sets of rollers is 0~10T.

3. The process for forming a flexible self-supporting thick electrode preform film according to claim 1, characterized in that, The roller surfaces of each group of rollers are chrome-plated, and the thickness of the chrome plating layer on one side is 0.1 mm.

4. The process for forming a flexible self-supporting thick electrode preform film according to claim 1, characterized in that, Each set of rollers has a roller diameter of 200 mm, an effective roller width of 500 mm, and a roller surface hardness of HRC 60°.

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