Dry heat roller system

Abstract

The application relates to the technical field of battery pole piece manufacturing, in particular to a dry method hot roller pressing system which comprises an upper roller assembly and a lower roller assembly; the lower roller assembly comprises at least two of a first roller pressing area, a second roller pressing area and a third roller pressing area, the first roughness Ra1 of the first roller pressing area is 0.075-0.1 mu m, the second roughness Ra2 of the second roller pressing area is 0.04-0.7 mu m, and the third roughness Ra3 of the third roller pressing area is 0.01-0.035 mu m. The first roughness can realize the local compaction of PTFE fibers in the roller pressing process, the second roughness can realize the shearing, induction, depolymerization and recombination, the third roughness can realize the fiberization and stretching, through the at least two roller pressing areas, the fiberization, network formation and compaction stages of PTFE fibers in the dry method electrode preparation process are controlled, and the dry method pole piece with uniform in-plane, high peeling strength and low interface resistance is obtained.

Description

Technical Field

[0001] This application relates to the field of battery electrode manufacturing technology, and in particular to a dry hot rolling system. Background Technology

[0002] Dry electrode technology eliminates the traditional processes of slurry mixing, coating, and drying. Using polytetrafluoroethylene (PTFE) as a binder, PTFE fibers form a fiber network under mechanical force during the rolling process. The fiber network entangles the surrounding active materials and conductive agent particles together to form a self-supporting electrode material film, which has great potential for process simplification, cost reduction, and energy density improvement.

[0003] However, existing dry rolling technology is difficult to apply multi-dimensional and multi-scale synergistic effects to materials such as PTFE fibers, resulting in uneven fiberization of PTFE fibers. This leads to problems such as poor electrode uniformity, low peel strength between active material and current collector, and high electrode electronic impedance (Rct), which seriously restricts its industrial application. Utility Model Content

[0004] In view of this, this application provides a dry hot rolling system that can solve at least one of the above-mentioned technical problems.

[0005] This application provides a dry hot rolling system, which includes an upper roll assembly and a lower roll assembly. The lower roll assembly includes at least two of a first rolling region, a second rolling region, and a third rolling region. The first rolling region has a first roughness Ra1 of 0.075 μm-0.1 μm, the second rolling region has a second roughness Ra2 of 0.04 μm-0.7 μm, and the third rolling region has a third roughness Ra3 of 0.01 μm-0.035 μm.

[0006] The dry hot rolling system of this application, by setting at least two of the following three rolling regions on the lower roller assembly: a first rolling region, a second rolling region, and a third rolling region, wherein the first roughness of the first rolling region can achieve the effect of local compaction of PTFE fibers during the rolling process, the second roughness of the second rolling region can achieve the effect of shearing, induction, depolymerization, and recombination of PTFE fibers during the rolling process, and the third roughness of the third rolling region can achieve the effect of stretching and fiberization of PTFE fibers during the rolling process, thereby precisely controlling the fiberization, web formation, and compaction stages of PTFE fibers during the dry electrode preparation process, and finally obtaining dry electrode sheets with in-plane uniformity, high peel strength, and low interfacial resistance (Rct), which is particularly suitable for the preparation of thick electrode sheets.

[0007] In some embodiments, the upper roller assembly includes a first smooth roller, a second smooth roller, and a third smooth roller, and the lower roller assembly includes a first pressure roller, a second pressure roller, and a third pressure roller, wherein the first smooth roller corresponds to the first pressure roller, the second smooth roller corresponds to the second pressure roller, and the third smooth roller corresponds to the third pressure roller; the first roller pressing area is disposed on the first pressure roller, the second roller pressing area is disposed on the second pressure roller, and the third roller pressing area is disposed on the third pressure roller.

[0008] The first rolling pressing area is set on the first pressing roller, the second rolling pressing area is set on the second pressing roller, and the third rolling pressing area is set on the third pressing roller, which can form a multi-roller series scheme. The structure, temperature and pressure of the first pressing roller, the second pressing roller and the third pressing roller can be set independently to form a process path of "gradient compaction" or "functional zoning". This gradually realizes the four-step coupled process of "local compaction - shear-induced depolymerization - in-groove recombination - drawing into fibers", and finally obtains dry electrode sheets with in-plane uniformity, high peel strength and low interfacial resistance (Rct), which is particularly suitable for the preparation of thick electrode sheets.

[0009] In some embodiments, the upper roller assembly includes a fourth light roller, and the lower roller assembly includes a fourth pressure roller, wherein at least two of the first pressure region, the second pressure region, and the third pressure region are disposed on the fourth pressure roller.

[0010] At least two of the first, second, and third pressing regions are arranged on the fourth pressing roller, which can simplify the structure of the dry hot pressing system.

[0011] In some embodiments, at least two of the first rolling region, the second rolling region, and the third rolling region overlap.

[0012] The overlap of at least some of the different rolling zones can achieve the continuity of the four-step coupled process of "local compaction - shear-induced depolymerization - in-groove recombination - fiber drawing".

[0013] In some embodiments, the lower roller assembly further includes a base roller surface, wherein the first rolling region, the second rolling region, and the third rolling region are distributed on at least a portion of the base roller surface, and the fourth roughness Ra4 of the base roller surface is 0.006μm-0.02μm.

[0014] The fourth roughness of the base roller surface is within the above range, which can meet the flatness requirements when setting the first roller pressing area, the second roller pressing area and the third roller pressing area.

[0015] In some embodiments, the first rolling area includes grooves, the groove width being 0.5mm-3.0mm and the groove depth being 30μm-200μm.

[0016] When the groove depth and width are within the above range, a first rolling region with a first roughness Ra1 of 0.075μm-0.1μm can be obtained.

[0017] In some embodiments, the second rolling region includes a plurality of grooves and / or a plurality of dot-matrix-arranged protrusions, wherein the width of the grooves and / or the protrusions is 50μm-500μm, and the depth of the grooves and / or the height of the protrusions is 5μm-80μm.

[0018] When the dimensions of the grooves and / or lattice protrusions are within the above range, a second roll-pressed region with a second roughness Ra2 of 0.04μm-0.7μm can be obtained.

[0019] In some embodiments, the plurality of grooves form at least one of a cross groove pattern, a honeycomb pattern, a parallel groove pattern, and a spiral groove pattern.

[0020] The grooves can use a variety of patterns, which can increase the applicability of the second pressure roller area.

[0021] In some embodiments, the third rolling region includes a plurality of micro-protrusions, the height of which is 0.1 μm-5 μm.

[0022] With the height of the micro-protrusions within the above range, a third roll forming region with a third roughness Ra3 of 0.01μm-0.035μm can be obtained.

[0023] In some embodiments, the roughness Ra1 of the first rolling region is 0.088μm-0.091μm, the roughness Ra2 of the second rolling region is 0.045μm-0.57μm, and the roughness Ra3 of the third rolling region is 0.015μm-0.025μm.

[0024] The roughness of the first, second, and third rolling regions is preferably within the range described above, which can further precisely control the fiberization, web formation, and compaction stages of PTFE fibers during the dry electrode preparation process, ultimately obtaining a dry electrode sheet with more uniform in-plane properties, higher peel strength, and lower interfacial resistance (Rct). Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the first pressure roller and the first smooth roller provided in one embodiment of this application.

[0026] Figure 2 This is a schematic diagram of the structure of the second pressure roller and the second smooth roller provided in one embodiment of this application.

[0027] Figure 3 This is a schematic diagram of the structure of the third pressure roller and the third smooth roller provided in one embodiment of this application.

[0028] Figure 4 A partial view of the fourth pressure roller provided in one embodiment of this application.

[0029] Explanation of key component symbols: 1. First pressure roller; 11. First roller pressing area; 111. Groove; 2. First smooth roller; 3. Second pressure roller; 31. Second roller pressing area; 4. Second smooth roller; 5. Third pressure roller; 51. Third roller pressing area; 6. Third smooth roller; 7. Fourth pressure roller. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0031] To address the problems of poor uniformity, low peel strength between active material and current collector, and high electronic resistance (Rct) of dry electrode sheets obtained by existing dry electrode technology, this application provides a dry hot rolling system that can produce dry electrode sheets with in-plane uniformity, high peel strength, and low interfacial resistance (Rct), and is particularly suitable for the preparation of thick electrode sheets.

[0032] The dry hot rolling system includes an upper roller assembly and a lower roller assembly. The upper roller assembly is used to contact the current collector, flatten the current collector, and ultimately determine the overall thickness and surface smoothness of the electrode sheet. The lower roller assembly is used to process the binder, such as PTFE fiber, into a micron / nano-scale fiber network, so that the fiber network can entangle the surrounding active material and conductive agent particles together.

[0033] Please refer to Figures 1-3 The lower roller assembly includes at least two of a first roller pressing region 11, a second roller pressing region 31, and a third roller pressing region 51. The first roughness Ra1 of the first roller pressing region 11 is 0.075μm-0.1μm, the second roughness Ra2 of the second roller pressing region 31 is 0.04μm-0.7μm, and the third roughness Ra3 of the third roller pressing region 51 is 0.01μm-0.035μm. Optionally, the first roughness Ra1 can be 0.075μm, 0.085μm, 0.095μm, and 0.1μm, etc.; the second roughness Ra2 can be 0.04μm, 0.05μm, 0.06μm, and 0.07μm, etc.; and the third roughness Ra3 can be 0.01μm, 0.02μm, 0.03μm, and 0.035μm, etc., or it can be a range consisting of any two of the above values.

[0034] By setting at least two of the following three roller pressing regions on the lower roller assembly: a first roller pressing region 11, a second roller pressing region 31, and a third roller pressing region 51, the first roughness of the first roller pressing region 11 can achieve the effect of local compaction of PTFE fibers during the roller pressing process; the second roughness of the second roller pressing region 31 can achieve the effect of shearing, induction, depolymerization, and recombination of PTFE fibers during the roller pressing process; and the third roughness of the third roller pressing region 51 can achieve the effect of stretching and fiberization of PTFE fibers during the roller pressing process. By selecting a combination of at least two roller pressing regions, the fiberization, web formation, and compaction stages of PTFE fibers during the dry electrode preparation process can be precisely controlled, ultimately obtaining a dry electrode sheet with in-plane uniformity, high peel strength, and low interfacial resistance (Rct), which is particularly suitable for the preparation of thick electrode sheets.

[0035] In some embodiments, the roughness Ra1 of the first roll-pressed region 11 is 0.088 μm-0.091 μm, the roughness Ra2 of the second roll-pressed region 31 is 0.045 μm-0.57 μm, and the roughness Ra3 of the third roll-pressed region 51 is 0.015 μm-0.025 μm. The roughnesses of the first roll-pressed region 11, the second roll-pressed region 31, and the third roll-pressed region 51 are preferably within the above ranges, which allows for more precise control of the fiberization, web formation, and compaction stages of PTFE fibers during the dry electrode fabrication process, ultimately resulting in a dry electrode sheet with more uniform in-plane properties, higher peel strength, and lower interfacial resistance (Rct).

[0036] In some embodiments, the first rolling area 11 includes a plurality of parallel grooves 111, which may be longitudinal grooves, transverse grooves, or oblique grooves. A longitudinal groove is one in which the extending direction of the groove 111 is perpendicular to the axis of rotation of the lower roller assembly; a transverse groove is one in which the extending direction of the groove 111 is parallel to the axis of rotation of the lower roller assembly; and an oblique groove is one in which the extending direction of the groove 111 is inclined relative to the axis of rotation of the lower roller assembly. The groove width of the groove 111 is 0.5mm-3.0mm, and the groove depth is 30μm-200μm. Optionally, the groove width of the groove 111 can be 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, and 3mm, etc., and the groove depth of the groove 111 can be 30μm, 60μm, 90μm, 120μm, 150μm, 180μm, and 200μm, etc., or a range consisting of any two of the above values. If the groove depth and groove width of the groove 111 are within the above range, a first roll forming region 11 with a first roughness Ra1 of 0.075μm-0.1μm can be obtained.

[0037] In some embodiments, the second roll forming region 31 includes a plurality of grooves and / or dot-matrix-arranged protrusions, wherein the width of the grooves and / or protrusions is 50μm-500μm, and the depth of the grooves or the height of the protrusions is 5μm-80μm. Optionally, the aforementioned width can specifically be 50μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, and 500μm, etc., and the aforementioned height or depth can specifically be 5μm, 15μm, 25μm, 35μm, 45μm, 55μm, 65μm, 75μm, and 80μm, etc., or it can be a range consisting of any two of the above values. When the size of the grooves and / or dot-matrix protrusions is within the above range, a second roll forming region 31 with a second roughness Ra2 of 0.04μm-0.7μm can be obtained.

[0038] In some embodiments, the groove pattern includes at least one of cross groove pattern, honeycomb pattern, parallel groove pattern and spiral groove pattern, and the cross-sectional shape of the protrusion includes a circle or polygon, which can improve the applicability of the second pressure roller area 31.

[0039] In some embodiments, the third rolling region 51 includes a plurality of spaced-apart micro-protrusions. The shape of the micro-protrusions includes circular or polygonal protrusions, and the height of the micro-protrusions is 0.1 μm-5 μm. Optionally, the height of the micro-protrusions can be 0.1 μm, 1 μm, 2 μm, 3 μm, 4 μm, and 5 μm, or any range consisting of any two of the above values. When the height of the micro-protrusions is within the above range, a third rolling region 51 with a third roughness Ra3 of 0.01 μm-0.035 μm can be obtained.

[0040] In some embodiments, please refer to Figures 1-3 The upper roller assembly includes a first smooth roller 2, a second smooth roller 4, and a third smooth roller 6, while the lower roller assembly includes a first pressure roller 1, a second pressure roller 3, and a third pressure roller 5. The first pressure roller region 11 is located on the first pressure roller 1, the second pressure roller region 31 is located on the second pressure roller 3, and the third pressure roller region 51 is located on the third pressure roller 5. The first pressure roller region 11, the second pressure roller region 31, and the third pressure roller region 51 are located on different pressure rollers, forming a multi-roller series configuration. In this configuration, the structure, temperature, and pressure of the first pressure roller 1, the second pressure roller 3, and the third pressure roller 5 can be independently set to form a "gradient compaction" or "functional zoning" process path. This gradually realizes a four-step coupled process of "local compaction - shear-induced depolymerization - in-groove recombination - drawing into fibers," ultimately obtaining dry-processed electrode sheets with in-plane uniformity, high peel strength, and low interfacial resistance (Rct), which is particularly suitable for the preparation of thick electrode sheets.

[0041] It should be noted that this application does not limit the area of ​​the first pressing region 11 on the first pressing roller 1, the area of ​​the second pressing region 31 on the second pressing roller 3, and the area of ​​the third pressing region 51 on the third pressing roller 5. They can be selected according to the required uniformity, peel strength and interface resistance of the electrode.

[0042] In some embodiments, please refer to Figure 4 The upper roller assembly includes a fourth smooth roller (not shown in the figure), and the lower roller assembly includes a fourth pressure roller 7. At least two of the first pressure region 11, the second pressure region 31, and the third pressure region 51 are disposed on the fourth pressure roller 7. The arrangement of at least two of the first pressure region 11, the second pressure region 31, and the third pressure region 51 on the fourth pressure roller 7 can simplify the structure of the dry hot rolling system.

[0043] It should be noted that this application does not limit the area and position of the first rolling region 11, the second rolling region 31 and the third rolling region 51 on the fourth pressure roller 7, and they can be selected according to the required uniformity, peel strength and interface resistance of the electrode.

[0044] In some embodiments, the first roll pressing region 11, the second roll pressing region 31, and the third roll pressing region 51 at least partially overlap. The at least partial overlap of the different roll pressing regions can achieve the continuity of the four-step coupled process of "local compaction-shear-induced depolymerization-in-groove recombination-drawing into fibers".

[0045] In some embodiments, the lower roller assembly further includes a base roller surface (not shown in the figure), with a first rolling region 11, a second rolling region 31, and a third rolling region 51 distributed on at least a portion of the base roller surface, wherein the fourth roughness Ra4 of the base roller surface is 0.006 μm-0.02 μm. The fourth roughness of the base roller surface is within the above range, which can meet the flatness requirements when the first rolling region 11, the second rolling region 31, and the third rolling region 51 are set, reducing the processing difficulty of the first rolling region 11, the second rolling region 31, and the third rolling region 51.

[0046] The present application will be described below through specific embodiments and comparative examples.

[0047] Example 1 (1) After grinding and polishing, the mold steel forms a base roller surface with a fourth roughness Ra4≤0.01μm, thus obtaining the fourth pressure roller and the fourth polished roller; and the base roller surface of the fourth pressure roller is laser etched to form a first roller pressing area, a second roller pressing area and a third roller pressing area with a third roughness Ra3 of 0.8μm. The first roller pressing area includes a 90° cross groove with a groove width of 1.5mm and a groove depth of 50μm. The second roller pressing area includes a 45° cross diamond groove with a groove width of 200μm, a groove depth of 30μm and a groove spacing of 400μm.

[0048] (2) A tungsten carbide (WC-Co) coating with a thickness of about 15 μm is deposited on the surface of the fourth pressure roller. After deposition, the third pressure roller area is slightly polished to ensure that the Ra3 value is stable.

[0049] (3) The negative electrode material is rolled using the above-mentioned roller assembly, wherein the roller temperature is 90°C, the linear pressure is 60kN / m, the speed is 2m / min, and the composition of the negative electrode material includes graphite negative electrode material (96wt%), conductive carbon black (2wt%) and PTFE (2wt%).

[0050] Using the pressure roller assembly of Example 1, the dry-process electrode sheets obtained have a thickness uniformity (within ±2μm) >98%, a peel strength >25N / m, and an interface resistance (Rct) of 25Ω·cm². After 150 kilometers of electrode production, the outline of the second roller pressing area is clear, and the size change of the second roller pressing area is <2μm as measured by a three-dimensional morphology instrument. Moreover, there is no material sticking after 24 hours of continuous production, and no intermediate cleaning is required.

[0051] Example 2 (1) After grinding and polishing, stainless steel forms a base roller surface with a fourth roughness Ra4 of 0.01μm, resulting in a fourth pressure roller and a fourth smooth roller. Chemical etching is used on the base roller surface of the fourth pressure roller to form a second roller pressing area and a third roller pressing area with a third roughness Ra3 of 1.2μm. The second roller pressing area includes a honeycomb dot matrix groove with a dot diameter of 100μm, a groove depth of 20μm, and a center spacing of 250μm, resulting in the fourth pressure roller. A smooth pressure roller is used as the fourth smooth roller.

[0052] (2) The surface of the fourth pressure roller is coated with DLC (diamond-like carbon) coating with a thickness of about 4 μm.

[0053] (3) The above-mentioned pressure roller assembly is used to roll the negative electrode material, wherein the roller temperature is 85°C, the linear pressure is 45kN / m, the speed is 1.5m / min, and the negative electrode material is silicon-carbon composite negative electrode material (SiOx / C).

[0054] Using the pressure roller assembly of Example 2, the dry electrode obtained was discharged at a rate of 0.5C. After 200 cycles, the capacity retention rate was 85%, the electrode porosity was 45%-50%, the peel strength was >20N / m, and the silicon-carbon composite negative electrode material was almost not adhered to the pressure roller assembly. The pressure roller assembly ran continuously for 72 hours without failure.

[0055] Example 3: (1) After grinding and polishing, the hard chrome plated mold steel forms a base roller surface with a fourth roughness Ra4 of 0.015μm, and a second pressure roller and a second smooth roller are obtained. The second roller pressing area is formed by laser etching on the base roller surface of the second pressure roller. The second roller pressing area includes a rectangular groove with a groove width of 80μm, a groove depth of 40μm, and a groove spacing of 150μm, so that the second roughness Ra2 of the second roller pressing area is 0.5μm. A tungsten carbide (WC-Co) coating is deposited on the roller surface of the second pressure roller.

[0056] (2) After grinding and polishing, the hard chrome plated mold steel forms a base roller surface with a fourth roughness Ra4 of 0.015μm, and a fourth pressure roller and a fourth polished roller are obtained. Laser etching is used on the base roller surface of the fourth pressure roller to form a first roller pressing area and a third roller pressing area with a third roughness Ra3 of 1.8μm. The first roller pressing area includes a groove with a groove width of 2.0mm and a groove depth of 100μm. A DLC (diamond-like carbon) coating is deposited on the roller surface of the second pressure roller.

[0057] (3) The above-mentioned pressure roller assembly is used to roll the positive electrode material. The second pressure roller has a roller temperature of 70°C and a line pressure of 50kN / m. The fourth pressure roller has a roller temperature of 110°C and a line pressure of 80kN / m. The composition of the positive electrode material includes NCM811 positive electrode material (94wt%), conductive agent (4wt%), and PTFE (2wt%).

[0058] Using the pressure roller assembly of Example 3, the pressure roller assembly is free from adhesion, the surface density fluctuation of the positive electrode sheet is <±1.5%, the peel strength is >40N / m, and the linear speed can be increased to 3.5m / min without the occurrence of roller adhesion or electrode sheet quality problems.

[0059] Example 4 (1) After grinding and polishing, the hard chrome plated mold steel forms a base roller surface with a fourth roughness Ra4 of 0.006 μm, and the third pressure roller and the third smooth roller are obtained. The third roller pressing area is formed by laser etching on the base roller surface of the third pressure roller. The third roller pressing area includes shallow microgrooves with a groove width of 300 μm and a groove depth of 15 μm, so that the second roughness Ra3 of the third roller pressing area is 0.3 μm. Tungsten carbide (WC-Co) coating is deposited on the roller surface of the third pressure roller.

[0060] (2) After grinding and polishing, the hard chrome plated mold steel forms a base roller surface with a second roughness Ra4 of 0.006 μm, and a second pressure roller and a second smooth roller are obtained. A second roller pressing area is formed on the base roller surface of the second pressure roller by laser etching. The first roller pressing area includes a deep microgroove with a groove width of 150 μm and a groove depth of 50 μm, so that the second roughness Ra2 of the second roller pressing area is 1 μm. A tungsten carbide (WC-Co) coating is deposited on the roller surface of the second pressure roller.

[0061] (3) After grinding and polishing, the hard chrome plated mold steel forms a base roller surface with a fourth roughness Ra4 of 0.006μm, and the first pressure roller and the first smooth roller are obtained. The first roller pressing area is formed by laser etching on the base roller surface of the first pressure roller. The first roller pressing area includes grooves with a groove width of 1.0mm and a groove depth of 120μm, so that the second roughness Ra1 of the first roller pressing area is 0.4μm. A DLC (diamond-like carbon) coating is deposited on the roller surface of the first pressure roller.

[0062] (4) The above-mentioned pressure roller assembly is used to roll the positive electrode material, wherein the temperature of the first pressure roller is 120°C and the linear pressure is 100kN / m, the temperature of the second pressure roller is 100°C and the linear pressure is 60kN / m, the temperature of the third pressure roller is 80°C and the linear pressure is 30kN / m, and the positive electrode material is lithium cobalt oxide (LCO) positive electrode.

[0063] Using the pressure roller assembly of Example 4, the electrode sheet has no delamination or cracks, and the areal capacity reaches 8.5mAh / cm². Under a linear pressure of up to 100kN / m, the pressure roller assembly has no deformation capacity, and Rct < 40Ω·cm² under high load.

[0064] Comparative Example 1 Unlike Example 1, the mold steel is ground and polished to form a substrate roller surface with a fourth roughness Ra4 of 0.05 μm, and a DLC coating is deposited.

[0065] Using the pressure roller assembly of Comparative Example 1, after depositing the DLC coating, the original peaks and valleys of the substrate roller surface were amplified, resulting in an actual Ra4 of 0.07μm on the substrate roller surface and the presence of stress concentration points. Under the same working conditions, the DLC coating exhibited local peeling after producing approximately 50 kilometers of electrode sheets. The peeled DLC coating particles contaminated the electrode sheets, causing scratches on the electrode sheet surface and increasing the risk of short circuits.

[0066] Furthermore, those skilled in the art should recognize that the above embodiments are merely illustrative of this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of this application's disclosure.

Claims

1. A dry hot rolling system, characterized in that, The dry hot roll pressing system includes an upper roll assembly and a lower roll assembly; The lower roller assembly includes at least two of a first rolling region, a second rolling region, and a third rolling region. The first roughness Ra1 of the first rolling region is 0.075μm-0.1μm, the second roughness Ra2 of the second rolling region is 0.04μm-0.7μm, and the third roughness Ra3 of the third rolling region is 0.01μm-0.035μm.

2. The dry hot rolling system according to claim 1, characterized in that, The upper roller assembly includes a first light roller, a second light roller, and a third light roller, and the lower roller assembly includes a first pressure roller, a second pressure roller, and a third pressure roller, wherein the first light roller corresponds to the first pressure roller, the second light roller corresponds to the second pressure roller, and the third light roller corresponds to the third pressure roller; The first roller pressing area is disposed on the first pressure roller, the second roller pressing area is disposed on the second pressure roller, and the third roller pressing area is disposed on the third pressure roller.

3. The dry hot rolling system according to claim 1, characterized in that, The upper roller assembly includes a fourth light roller, and the lower roller assembly includes a fourth pressure roller, wherein at least two of the first pressure region, the second pressure region, and the third pressure region are disposed on the fourth pressure roller.

4. The dry hot rolling system according to claim 3, characterized in that, There is overlap between at least two of the first rolling region, the second rolling region, and the third rolling region.

5. The dry hot rolling system according to claim 1, characterized in that, The lower roller assembly further includes a base roller surface, wherein the first roller pressing region, the second roller pressing region, and the third roller pressing region are distributed on at least a portion of the base roller surface, and the fourth roughness Ra4 of the base roller surface is 0.006μm-0.02μm.

6. The dry hot rolling system according to claim 1, characterized in that, The first rolling area includes grooves, the groove width being 0.5mm-3.0mm and the groove depth being 30μm-200μm.

7. The dry hot rolling system according to claim 1, characterized in that, The second rolling area includes multiple grooves and / or multiple protrusions arranged in a matrix, wherein the width of the grooves and / or the protrusions is 50μm-500μm, and the depth of the grooves and / or the height of the protrusions is 5μm-80μm.

8. The dry hot rolling system according to claim 7, characterized in that, The plurality of grooves form at least one of the following: cross groove pattern, honeycomb pattern, parallel groove pattern, and spiral groove pattern.

9. The dry hot rolling system according to claim 1, characterized in that, The third rolling area includes multiple micro-protrusions, the height of which is 0.1μm-5μm.

10. The dry hot rolling system according to claim 1, characterized in that, The roughness Ra1 of the first rolling region is 0.088μm-0.091μm, the roughness Ra2 of the second rolling region is 0.045μm-0.57μm, and the roughness Ra3 of the third rolling region is 0.015μm-0.025μm.

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