A dry electrode multi-stage roller film forming equipment and differential calendering method

Abstract

The present invention discloses a dry electrode multi-stage rolling film-forming equipment and a differential calendering method, which belong to the technical field of dry electrode calendering. The equipment includes a first-stage calendering mechanism, a second-stage calendering mechanism, and a third-stage calendering mechanism arranged in sequence along the material travel direction. The first-stage calendering mechanism initially calenders the particle powder coated with a fiberized network into a first-stage membrane. The second-stage calendering mechanism stacks two layers of the first-stage membrane and performs differential thinning and calendering to form a second-stage membrane. The third-stage calendering mechanism stacks two layers of the second-stage membrane and performs differential thinning and calendering to form a finished membrane. The differential calendering method includes the steps of powder fiberization and coating preparation, first-stage calendering collaborative film formation, second-stage differential superposition calendering, a first online thickness-density closed-loop correction, third-stage differential superposition calendering, and a second online thickness-density closed-loop correction. Through the synergistic effect of multi-stage calendering and differential calendering, the problem of poor consistency between membrane compaction density and surface density in the existing dry electrode calendering film-forming technology is effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of dry electrode calendering, and in particular to a dry electrode multi-stage roller-pressing film-forming device and a differential speed calendering method. Background Art

[0002] In the existing dry electrode preparation process, multi-roller continuous rolling equipment is widely used in the calendering process from powder to membrane. Such equipment can meet the basic requirements of calendering to a certain extent, and can achieve high-precision control of the thickness consistency of the membrane. However, due to the problem of uneven distribution of active substances, conductive agents and PTFE binders during the dry mixing process of powders, excessive binder in local areas will form "soft lumps", which will result in low density due to low resistance during the pressing process; and areas with insufficient binder are prone to looseness due to weak particle bonding, forming low-density areas. The uneven distribution phenomenon directly leads to inconsistent blocks in the compaction density and surface density of the membrane after one calendering. What is more serious is that this inconsistency cannot be completely eliminated in the subsequent thinning calendering process. Instead, it will be further stretched in the membrane direction, exacerbating the density unevenness.

[0003] Secondly, the dry-mixed powder itself lacks fluidity, which makes the traditional method of improving density uniformity by increasing rolling pressure or adding calendering passes limited in effect. Due to the weak non-plastic deformation ability of the material, excessive pressurization not only fails to effectively improve density uniformity, but may lead to local stress concentration and even cause diaphragm tearing, resulting in production failure.

[0004] In addition, the problem of uneven surface density in the initial forming stage will be simultaneously amplified in the subsequent thinning and calendering process, resulting in a further increase in the deviation between thickness and density. In order to achieve the desired thinning effect, greater pressure needs to be applied to the thicker areas. However, for non-plastic materials, it is difficult to fill the low-density areas through plastic flow. The final result is that the difference in compaction density will not only not be improved, but will be further expanded.

[0005] Therefore, it is necessary to provide a dry electrode multi-stage roller pressing film forming equipment and a differential calendering method to solve the above technical problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a dry electrode multi-stage roller pressing film forming equipment and a differential speed calendering method to solve the above technical problems.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A dry electrode multi-stage rolling film forming equipment, comprising four primary calendering mechanisms, two secondary calendering mechanisms, a third calendering mechanism and a control mechanism arranged in sequence along the direction of material travel, wherein the output ends of two of the primary calendering mechanisms are connected to the input end of one of the second calendering mechanisms, the output ends of the remaining two primary calendering mechanisms are connected to the input end of the remaining second calendering mechanism, and the output ends of the two second calendering mechanisms are connected to the input end of the third calendering mechanism; the input end of the primary calendering mechanism is connected to a powder hopper for storing and mixing granular powder, and the granular powder enters the primary calendering mechanism. A first-stage calendering mechanism is provided, wherein the granular powder coated with the fiberized network is formed. The first-stage calendering mechanism includes at least one group of pressing rollers for initially pressing the granular powder coated with the fiberized network into a first-stage membrane sheet. The second-stage calendering mechanism includes a first differential-speed pressing roller group for superimposing two layers of the first-stage membrane sheets and performing differential thinning and calendering to form a second-stage membrane sheet. The third-stage calendering mechanism includes a second differential-speed pressing roller group for superimposing two layers of the second-stage membrane sheets and performing differential thinning and calendering to form a finished membrane sheet. The pressing roller group, the first differential-speed pressing roller group, and the second differential-speed pressing roller group are all electrically connected to a control mechanism.

[0009] The first differential calendering roller group includes a first fast calendering roller, a first slow calendering roller, and a first differential drive device, wherein the first fast calendering roller and the first slow calendering roller are arranged side by side in the horizontal direction, and the first differential drive device is used to drive the first fast calendering roller and the first slow calendering roller to rotate at different linear speeds;

[0010] The second differential calendering roller group includes a second fast calendering roller, a second slow calendering roller, and a second differential drive device, wherein the second fast calendering roller and the second slow calendering roller are arranged side by side in the horizontal direction, and the second differential drive device is used to drive the second fast calendering roller and the second slow calendering roller to rotate at different linear speeds;

[0011] The linear speed of the first fast calendering roller is twice that of the first slow calendering roller, and the linear speed of the second fast calendering roller is twice that of the second slow calendering roller.

[0012] Furthermore, the primary calendering mechanism adopts a constant speed calendering mode to calender the granular powder coated with the fiberized network into a primary membrane. The membrane thickness output by the primary calendering mechanism is set to H1, and the linear speed is v1. The secondary calendering mechanism adopts a differential speed calendering mode to input the primary membrane from the primary calendering mechanism and thin the membrane thickness to H2, where H2

[0013] ; ​

[0014] The linear speed of the first fast calendering roller of the secondary calendering mechanism is K1×v2, where K1 is the preset speed ratio of the secondary calendering mechanism;

[0015] The three-stage calendering mechanism continues to thin the secondary film output by the two-stage calendering mechanism to a thickness of H3, wherein H3<H2. Then the linear speed v3 of the second slow calendering roller of the three-stage calendering mechanism satisfies the following relationship:

[0016] ;

[0017] The linear speed of the second fast calendering roller of the three-stage calendering mechanism is K2×v3, where K2 is the preset speed ratio of the three-stage calendering mechanism.

[0018] Furthermore, it also includes a number of confluence guide devices, which are horizontally arranged at the input ends of the secondary calendering mechanism and the tertiary calendering mechanism, and are respectively connected to the output ends of the primary calendering mechanism and the secondary calendering mechanism, for receiving the primary diaphragm from the primary calendering mechanism and the secondary diaphragm from the secondary calendering mechanism, and guiding the primary diaphragm and the secondary diaphragm in a horizontal posture into the secondary calendering mechanism and the tertiary calendering mechanism for differential thinning and calendering.

[0019] Furthermore, the first-level calendering mechanism, the second-level calendering mechanism and the third-level calendering mechanism are all fixed by a frame, and a number of diaphragm tension adjustment guide rollers are provided between the first-level calendering mechanism and the second-level calendering mechanism, and between the second-level calendering mechanism and the third-level calendering mechanism. The output end of the third-level calendering mechanism is provided with a diaphragm winding mechanism electrically connected to the control mechanism, which is used to collect and wind the finished diaphragms into rolls. The control mechanism can adjust the rotation speed of the diaphragm winding mechanism to match the output speed of the finished diaphragms.

[0020] Furthermore, it also includes several thickness monitoring mechanisms, which are respectively arranged at the output ends of the first-stage calendering mechanism, the second-stage calendering mechanism and the third-stage calendering mechanism, for real-time monitoring of the output film thickness and transmitting the thickness signal to the control mechanism. The control mechanism automatically adjusts the pressure and linear speed ratio between the pressure roller group and the first differential pressure roller group, and the pressure and linear speed ratio between the first differential pressure roller group and the second differential pressure roller group according to the thickness signal.

[0021] A differential calendering method for a dry electrode multi-stage roll-pressing film-forming device, used for the dry electrode multi-stage roll-pressing film-forming device, the differential calendering method comprising the following steps:

[0022] S1. Preparation of powder fiberization coating: fully mixing the active material, conductive agent and PTFE fiber in the powder hopper, so that the PTFE fiber self-assembles on the particle surface to form a three-dimensional coating network, thereby obtaining a particle powder coated with a fiberized network;

[0023] S2, primary calendering collaborative film formation: the four primary calendering mechanisms perform primary calendering on the fibrous network-coated granular powder obtained in step S1 at a constant roller gap and a constant speed roller surface to obtain a primary film with uniform thickness and self-sustaining strength;

[0024] S3, secondary differential superposition calendering: The two groups of the first-level membrane sheets are respectively introduced into the inlets of the two first differential pressure roller groups in a horizontal posture, aligned, tensioned and curling eliminated, and differential calendering is performed with the linear speed of the first fast calendering roller being twice that of the first slow calendering roller and the linear speed of the first fast calendering roller being twice that of the pressure roller group, so that the two layers of the first-level membrane sheets are stacked and synchronously stretched and thinned to obtain a secondary membrane sheet;

[0025] S4, first online thickness-density closed-loop calibration: The thickness and surface density of the secondary diaphragm are measured in real time using a thickness monitoring mechanism, and the data are transmitted back to the control mechanism, which adaptively adjusts the roller gap, pressure, and linear speed ratio of the first differential pressure roller group;

[0026] S5, three-stage differential superposition calendering: the two layers of the secondary membrane are subjected to a second differential calendering in the second differential calendering roller group, with the linear speed of the second fast calendering roller being twice that of the second slow calendering roller and the linear speed of the second fast calendering roller being twice that of the first fast calendering roller, to further densify and lock the fiber network structure, thereby forming a finished membrane of target thickness;

[0027] S6. Second online thickness-density closed-loop correction: The thickness and surface density of the finished film are measured in real time by a thickness monitoring mechanism, and the data are transmitted back to the control mechanism. The control mechanism adaptively adjusts the roller gap, pressure and linear speed ratio of the second differential pressure roller group.

[0028] Furthermore, in steps S4 and S6, the thickness monitoring mechanism monitors the actual thickness H in real time. c , the target thickness of the diaphragm is H0, and the diaphragm thickness deviation ΔH is calculated to satisfy the following relationship:

[0029] ;

[0030] When the diaphragm thickness deviation is ΔH≤5%, the control mechanism maintains the currently set calendering parameters unchanged and continues the calendering operation; when the diaphragm thickness deviation is ΔH>5%, the control mechanism correspondingly prioritizes adjusting the speed ratio of the first differential pressure roller group and / or the second differential pressure roller group to return the diaphragm thickness to the target range;

[0031] According to the law of conservation of mass, the instantaneous mass flow m of the material in the calendering zone is constant, which can be expressed as the following relationship:

[0032] ;

[0033] Where ρ is the film density, w is the film width, ρ and w are both considered constant, v is the surface linear velocity of the slow calendering roller, and H is the actual thickness of the film; the optimized speed ratio K'=(K0×H0) / H c , where K0 is the current speed ratio, which represents the linear speed ratio of the first fast calendering roller to the first slow calendering roller, or the linear speed ratio of the second fast calendering roller to the second slow calendering roller. The speed ratio of the first differential pressure roller group or the second differential pressure roller group is adjusted according to the obtained optimized speed ratio K'. The film thickness deviation correction is to change the film strip conveying speed by adjusting the slow roller speed, thereby indirectly adjusting the differential speed ratio within the same group.

[0034] Furthermore, the control mechanism adopts a self-learning algorithm based on a convolutional neural network to perform rolling training on the historical data of the diaphragm thickness and the differential speed of the first differential pressure roller group and the differential speed of the second differential pressure roller group in the past 24 hours, updates the prediction model every 30 minutes, and automatically gives the roller gap compensation amount of the first differential pressure roller group and the second differential pressure roller group.

[0035] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention realizes efficient continuous calendering from granular powder to finished membrane through the synergistic effect of a multi-stage calendering mechanism and a differential pressure roller group. The equipment adopts four first-level calendering mechanisms, two second-level calendering mechanisms and one third-level calendering mechanism, and cooperates with the differential pressure roller group to perform differential thinning calendering, which effectively improves the thickness uniformity and density consistency of the membrane, can reduce the feeding accuracy of the powder and the manufacturing accuracy of the equipment, and at the same time completely solves the problem of substandard or unstable consistency of the compaction density and surface density of dry electrodes, laying the foundation for the dry electrode rolling process to replace wet coating; through online thickness monitoring and adaptive control, the equipment can adjust the calendering parameters in real time to ensure the stability and consistency of product quality; in addition, the self-learning algorithm based on convolutional neural network further optimizes the calendering parameters, adapts to the fluctuations of raw materials and process conditions, reduces manual intervention, and reduces production costs. It not only solves the density inconsistency problem caused by uneven powder distribution in the existing technology, but also significantly improves production efficiency, meets the needs of large-scale production, and has significant economic benefits and market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the dry electrode multi-stage roller-pressing film forming equipment of the present invention;

[0038] Figure 2 Schematic diagram of the first-level calendering mechanism of the present invention;

[0039] Figure 3 Schematic diagram of the two-stage calendering mechanism of the present invention;

[0040] Figure 4 Schematic diagram of the three-stage calendering mechanism of the present invention;

[0041] Figure 5 Schematic diagram of the first differential pressure roller group of the present invention;

[0042] Figure 6 is a schematic diagram of the second differential pressure roller group of the present invention;

[0043] Figure 7 This is a flow chart of the differential calendering method of the dry electrode multi-stage roller pressing film forming equipment of the present invention;

[0044] Among them, 1-first-level calendering mechanism, 11-pressing roller group, 12-first-level diaphragm, 2-second-level calendering mechanism, 21-first differential pressure roller group, 211-first fast calendering roller, 212-first slow calendering roller, 22-second-level diaphragm, 3-third-level calendering mechanism, 31-second differential pressure roller group, 311-second fast calendering roller, 312-second slow calendering roller, 32-finished diaphragm, 4-powder hopper, 5-merging guide device, 6-diaphragm tension adjustment guide roller, 7-diaphragm winding mechanism. DETAILED DESCRIPTION

[0045] The following is a detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings. It should be understood that the specific embodiments given here are only used to illustrate and explain the present invention and cannot be used to limit the present invention.

[0046] like Figures 1 to 6 As shown, a dry electrode multi-stage rolling film forming equipment includes four primary calendering mechanisms 1, two secondary calendering mechanisms 2, a tertiary calendering mechanism 3 and a control mechanism arranged in sequence along the material travel direction, wherein the output ends of two primary calendering mechanisms 1 are connected to the input end of one of the secondary calendering mechanisms 2, the output ends of the remaining two primary calendering mechanisms 1 are connected to the input end of the remaining secondary calendering mechanism 2, and the output ends of the two secondary calendering mechanisms 2 are connected to the input end of the tertiary calendering mechanism 3; the input end of the primary calendering mechanism 1 is connected to a powder hopper 4 for storing and mixing granular powder, and the granular powder enters the primary calendering mechanism 1. The granular powder coated with the fiberized network is formed before, and the first-level calendering mechanism 1 includes at least one group of pressing rollers 11, which is used to initially calender the granular powder coated with the fiberized network into a first-level membrane 12. The second-level calendering mechanism 2 includes a first differential pressing roller group 21, which is used to stack two layers of the first-level membrane 12 and perform differential thinning and calendering to form a second-level membrane 22. The third-level calendering mechanism 3 includes a second differential pressing roller group 31, which is used to stack two layers of the second-level membrane 22 and perform differential thinning and calendering to form a finished membrane 32. The pressing roller group 11, the first differential pressing roller group 21 and the second differential pressing roller group 31 are all electrically connected to the control mechanism.

[0047] The dry electrode multi-stage rolling film forming equipment of the present invention realizes efficient and continuous rolling from granular powder to finished film 32 through the multi-stage calendering mechanism working in coordination, effectively improving production efficiency and meeting the needs of large-scale production. The equipment includes four primary calendering mechanisms 1, two secondary calendering mechanisms 2 and one tertiary calendering mechanism 3. The primary calendering mechanism 1 is responsible for the preliminary rolling of the granular powder coated with the fiberized network into a film to complete the initial forming; the secondary calendering mechanism 2 adopts differential calendering technology to promote the directional flow of particles and rearrange and fill them, thereby optimizing the film structure; the tertiary calendering mechanism 3 further enhances the particle rearrangement and shaping function, not only continuing the effect of the secondary calendering, but also shaping the film thickness consistency, so that the compaction density, surface density and thickness uniformity of the film all meet the process requirements. By combining the step-by-step calendering with the shearing action of the differential rollers, the film thickness is gradually thinned and the density is more uniform. By utilizing the statistical average effect, complementary effect and step-by-step smoothing effect of multi-layer superimposed calendering, the traditional "single-layer optimization" thinking mode is broken through. In particular, the stress state and material behavior are changed by superimposing the structure, overcoming the limitation of simply applying pressure to non-plastic materials.

[0048] After the first stage of calendering, the surface density fluctuation is controlled within ±3.2%-3.8%, and the compaction density fluctuation is controlled within ±0.24-0.28g / cm³. Based on probability theory, after two membrane sheets are overlapped and calendered once, the probability of overlapping blocks with inconsistent compaction density and surface density is between 1% and 36%. Even calculated based on the maximum probability of 36%, after a single overlap, the surface density fluctuation can still be controlled within ±1.15%-1.36%, and the compaction density fluctuation is controlled within ±0.0864-0.1g / cm³. After two overlaps, the surface density fluctuation is further reduced to ±0.414%-0.49%, and the compaction density fluctuation is reduced to ±0.031-0.036g / cm³, significantly better than the standard surface density requirements of ±0.54%-0.7% and the compaction density requirements of ±0.039-0.0457g / cm³.

[0049] The first differential roller group 21 includes a first fast calendering roller 211, a first slow calendering roller 212, and a first differential drive device. The first fast calendering roller 211 and the first slow calendering roller 212 are arranged side by side in the horizontal direction. The first differential drive device is used to drive the first fast calendering roller 211 and the first slow calendering roller 212 to rotate at different linear speeds.

[0050] The second differential pressing roller group 31 includes a second fast calendering roller 311, a second slow calendering roller 312 and a second differential drive device. The second fast calendering roller 311 and the second slow calendering roller 312 are arranged side by side in the horizontal direction. The second differential drive device is used to drive the second fast calendering roller 311 and the second slow calendering roller 312 to rotate at different linear speeds.

[0051] By arranging the first fast calendering roller 211 and the first slow calendering roller 212 horizontally side by side and driven at different linear speeds by a first differential drive, the membrane can be effectively differentially calendered, promoting directional flow of particles, achieving rearrangement and dense packing, thereby optimizing the internal structure of the membrane and improving its density uniformity. Similarly, the second differential calendering roller set 31 has the same structure and function, further enhancing this structural advantage, enabling efficient thickness control and structural optimization of the membrane during continuous production, thereby improving product quality and meeting high-standard production requirements.

[0052] The linear speed of the first fast calendering roller 211 is twice that of the first slow calendering roller 212 , and the linear speed of the second fast calendering roller 311 is twice that of the second slow calendering roller 312 .

[0053]

[0054] As a preferred embodiment of the present invention, the primary calendering mechanism 1 adopts a constant speed calendering mode to calender the granular powder coated with the fiberized network into a primary diaphragm 12. The thickness of the diaphragm output by the primary calendering mechanism 1 is set to H1, and the linear speed is v1. The secondary calendering mechanism 2 adopts a differential calendering mode, inputs the primary diaphragm 12 from the primary calendering mechanism 1, and thins the diaphragm thickness to H2, where H2 < H1. The linear speed v2 of the first slow calendering roller 212 of the secondary calendering mechanism 2 satisfies the following relationship:

[0055] ;

[0056] The linear speed of the first fast calendering roller 211 of the secondary calendering mechanism 2 is K1×v2, where K1 is the preset speed ratio of the secondary calendering mechanism 2;

[0057] The three-stage calendering mechanism 3 continues to thin the secondary film 22 output by the two-stage calendering mechanism 2 to a thickness of H3, where H3 < H2. The linear velocity v3 of the second slow calendering roller 312 of the three-stage calendering mechanism 3 satisfies the following relationship:

[0058] ;

[0059] The linear velocity of the second fast calendering roller 311 of the three-stage calendering mechanism 3 is K2×v3, where K2 is a preset speed ratio of the three-stage calendering mechanism 3 .

[0060] In order to achieve a sequential thinning of the thickness from the first-stage calendering mechanism 1 to the second-stage calendering mechanism 2, and from the second-stage calendering mechanism 2 to the third-stage calendering mechanism 3, and to avoid material accumulation or excessive stretching of the diaphragm at each calendering entrance, according to the instantaneous mass flow conservation principle, the linear velocity of the membrane belt of the latter calendering mechanism 1 should strictly match the linear velocity of the outlet of the previous calendering mechanism 1, and be proportional to the ratio of the thickness of the front and rear diaphragms;

[0061] Assume that the thickness of the film output by the primary calendering mechanism 1 is H1 and the linear speed is v1. The secondary calendering mechanism 2 reduces the thickness to H2 (H2 < H1). Then the linear speed v2 of the first slow calendering roller 212 of the secondary calendering mechanism 2 should satisfy:

[0062] ;

[0063] If the three-stage calendering mechanism 3 continues to reduce the film thickness to H3 (H3 < H2), the linear velocity v3 of the second slow calendering roller 312 of the three-stage calendering mechanism 3 should satisfy:

[0064] ;

[0065] In addition, inside the secondary calendering mechanism 2 and the tertiary calendering mechanism 3, a differential pressure roller group is used to apply shear calendering. The linear speed of the first slow calendering roller 212 of the secondary calendering mechanism 2 is v2, and the linear speed of the corresponding first fast calendering roller 211 is K1×v2, where K1 is the set speed ratio of the secondary calendering mechanism 2. In this embodiment, the value K1=2.0. The linear speed of the second slow calendering roller 312 of the tertiary calendering mechanism 3 is v3, and the linear speed of the corresponding second fast calendering roller 311 is K2×v3, where K2 is the set speed ratio of the tertiary calendering mechanism 3. In this embodiment, the value K2=2.0 is taken. By setting the differential speed between the fast and slow rollers in the same calendering mechanism, a directional shearing and stretching effect can be applied to the membrane during the calendering process, thereby promoting the orientation of the fiberized network and the efficient compaction of the particles, and optimizing the internal structure and electrochemical properties of the membrane. At the same time, the linear speed of the slow calendering roller at each level of calendering mechanism is strictly matched with the linear speed of the calendering outlet of the previous level to ensure that the thickness thinning of the membrane during transmission is synchronously balanced with the linear speed, thereby avoiding accumulation or excessive stretching of the membrane at the entrance due to speed mismatch, thereby realizing an efficient and stable continuous film forming process.

[0066] In this embodiment, the linear speed v1 of the first-level calendering mechanism 1 is set to 1 m / min, the thickness of the output first-level film 12 is H1=0.5 mm, and the second-level calendering mechanism 2 presses the first-level film 12 to H2=0.25 mm. According to the formula v2=v1×(H1 / H2), the linear speed of the first slow calendering roller 212 of the second-level calendering mechanism 2 is v2=1×(0.5 / 0.25)=2 m / min. Since K1=2.0, Therefore, the linear speed of the first fast calendering roller 211 is 2×2=4m / min; similarly, if the three-stage calendering mechanism 3 thins the thickness of the secondary membrane 22 to H3=0.125mm, the linear speed of the second slow calendering roller 312 of the three-stage calendering mechanism 3 is v3=v2×(H2 / H3)=2×(0.25 / 0.125)=4m / min, and the linear speed of the second fast calendering roller 311 is K2×v3=2×4=8m / min.

[0067] As a preferred embodiment of the present invention, it also includes a plurality of confluence guiding devices 5, which are horizontally arranged at the input ends of the secondary calendering mechanism 2 and the tertiary calendering mechanism 3, and are respectively connected to the output ends of the primary calendering mechanism 1 and the secondary calendering mechanism 2, for receiving the primary diaphragm 12 from the primary calendering mechanism and the secondary diaphragm 22 from the secondary calendering mechanism 2, and guiding the primary diaphragm 12 and the secondary diaphragm 22 in a horizontal posture to the secondary calendering mechanism 2 and the tertiary calendering mechanism 3 for differential thinning and calendering.

[0068] The confluence guide device 5 is horizontally arranged at the input end of the secondary calendering mechanism 2 and the tertiary calendering mechanism 3, and is respectively connected to the output end of the primary calendering mechanism 1 and the secondary calendering mechanism 2, ensuring that the primary diaphragm 12 and the secondary diaphragm 22 always maintain a stable horizontal posture during the transmission process, and there will be no sagging, deviation or accumulation due to gravity, ensuring that the diaphragm can smoothly and stably enter the next-level calendering mechanism 1, avoiding equipment jams, shutdowns and other failures that may be caused by poor diaphragm transmission, and greatly improving the stability and reliability of equipment operation.

[0069] As a preferred embodiment of the present invention, the first-level calendering mechanism 1, the second-level calendering mechanism 2 and the third-level calendering mechanism 3 are all fixed by a frame, and a number of diaphragm tension adjustment guide rollers 6 are provided between the first-level calendering mechanism 1 and the second-level calendering mechanism 2, and between the second-level calendering mechanism 2 and the third-level calendering mechanism 3. The output end of the third-level calendering mechanism 3 is provided with a diaphragm winding mechanism 7 electrically connected to the control mechanism, which is used to collect and wind the finished diaphragm 32 into a roll. The control mechanism can adjust the rotation speed of the diaphragm winding mechanism 7 to match the output speed of the finished diaphragm 32.

[0070] Through the tension-adjusting guide roller and the electrically connected winding mechanism, precise control of the diaphragm tension and winding speed is achieved, effectively preventing the diaphragm from becoming loose or over-stretched during the transmission and winding process. The first-level calendering mechanism 1, the second-level calendering mechanism 2 and the third-level calendering mechanism 3 are fixed by a frame, combined with the diaphragm tension-adjusting guide roller 6, to ensure the stable transmission of the diaphragm in different calendering stages, thereby improving the forming quality of the diaphragm. In addition, the control mechanism adjusts the rotation speed of the diaphragm winding mechanism 7 to match it with the output speed of the finished diaphragm 32, further improving production efficiency and yield rate, and reducing production costs.

[0071] As a preferred embodiment of the present invention, it also includes several thickness monitoring mechanisms, which are respectively arranged at the output ends of the first-stage calendering mechanism 1, the second-stage calendering mechanism 2 and the third-stage calendering mechanism 3, for real-time monitoring of the output film thickness and transmitting the thickness signal to the control mechanism. The control mechanism automatically adjusts the pressure and linear speed ratio between the pressure roller group 11 and the first differential pressure roller group 21, as well as the pressure and linear speed ratio between the first differential pressure roller group 21 and the second differential pressure roller group 31 according to the thickness signal.

[0072] By setting up thickness monitoring mechanisms at the output ends of each level of calendering mechanisms, the thickness of the diaphragm can be monitored in real time and the data can be fed back to the control mechanism, realizing accurate monitoring and automatic adjustment of the calendering process, ensuring that the thickness of the diaphragm meets the process requirements, thereby significantly improving the stability and consistency of product quality, reducing the defective rate, and lowering production costs.

[0073] like Figure 7As shown, a differential calendering method for a dry electrode multi-stage roller-pressing film forming device is used for the dry electrode multi-stage roller-pressing film forming device. The differential calendering method includes the following steps:

[0074] S1. Preparation of powder fiberization coating: The active material, conductive agent and PTFE fiber are fully mixed in the powder hopper 4, so that the PTFE fiber self-assembles on the particle surface to form a three-dimensional coating network, thereby obtaining a particle powder coated with a fiberized network;

[0075] S2, primary calendering collaborative film formation: four primary calendering mechanisms 1 perform primary calendering on the granular powder coated with the fiberized network obtained in step S1 at a constant roller gap and a constant speed roller surface to obtain a primary film 12 with uniform thickness and self-sustaining strength;

[0076] S3, secondary differential superposition calendering: Two groups of primary membrane sheets 12 are respectively introduced into the inlets of two first differential pressure roller groups 21 in a horizontal posture, aligned, tensioned and curled. Differential calendering is performed with the linear speed of the first fast calendering roller 211 being twice that of the first slow calendering roller 212, and the linear speed of the first fast calendering roller 211 being twice that of the pressure roller group 11. After the two layers of primary membrane sheets 12 are stacked, they are simultaneously stretched and thinned to obtain a secondary membrane sheet 22;

[0077] S4, first online thickness-density closed-loop calibration: The thickness and surface density of the secondary diaphragm 22 are measured in real time using the thickness monitoring mechanism, and the data are transmitted back to the control mechanism, which adaptively adjusts the roller gap, pressure, and linear speed ratio of the first differential pressure roller group 21;

[0078] S5, three-stage differential superposition calendering: The two-layer secondary membrane 22 is subjected to a second differential calendering in the second differential roller group 31, with the linear speed of the second fast calendering roller 311 being twice that of the second slow calendering roller 312 and the linear speed of the second fast calendering roller 311 being twice that of the first fast calendering roller 211, to further densify and lock the fiber network structure, thereby forming a finished membrane 32 of target thickness;

[0079] S6. Second online thickness-density closed-loop correction: The thickness and surface density of the finished film 32 are measured in real time by the thickness monitoring mechanism, and the data are transmitted back to the control mechanism, which adaptively adjusts the roller gap, pressure and linear speed ratio of the second differential pressure roller group 31.

[0080] The differential calendering method of the present invention effectively solves the problem of poor consistency between the compaction density and surface density of the diaphragm in the existing dry electrode calendering film-forming technology through the synergistic effect of multi-stage calendering and differential calendering. The preliminary calendering film is formed by the first-stage calendering mechanism 1; the second-stage and third-stage calendering mechanisms 3 adopt differential calendering technology to subject the diaphragm to shear force during the calendering process, prompting the particles to rearrange and distribute, thereby improving the density uniformity of the diaphragm; in addition, through the online thickness-density closed-loop correction system, the calendering parameters are monitored and automatically adjusted in real time to ensure precise control of the thickness and density of the diaphragm. Compared with the existing technology, the present invention not only improves the consistency of the compaction density and surface density of the diaphragm, but also avoids the problem of local stress concentration or diaphragm tearing caused by the weak non-plastic deformation ability of the material, significantly improving the quality and performance of the dry electrode.

[0081] As a preferred embodiment of the present invention, in steps S4 and S6, the thickness monitoring mechanism monitors the actual thickness H in real time. c , the target thickness of the diaphragm is H0, and the diaphragm thickness deviation ΔH is calculated to satisfy the following relationship:

[0082] ;

[0083] When the diaphragm thickness deviation is ΔH≤5%, the control mechanism maintains the currently set calendering parameters unchanged and continues the calendering operation; when the diaphragm thickness deviation is ΔH>5%, the control mechanism correspondingly prioritizes adjusting the speed ratio of the first differential pressure roller group 21 and / or the second differential pressure roller group 31 to return the diaphragm thickness to the target range;

[0084] According to the law of conservation of mass, the instantaneous mass flow m of the material in the calendering zone is constant, which can be expressed as the following relationship:

[0085] ;

[0086] Where ρ is the film density, w is the film width, ρ and w are both considered constant, v is the surface linear velocity of the slow calendering roller, and H is the actual thickness of the film; the optimized speed ratio K'=(K0×H0) / H c , where K0 is the current speed ratio, and the speed ratio represents the linear speed ratio of the first fast calendering roller 211 to the first slow calendering roller 212, or the linear speed ratio of the second fast calendering roller 311 to the second slow calendering roller 312. The speed ratio of the first differential pressure roller group 21 or the second differential pressure roller group 31 is adjusted according to the obtained optimized speed ratio K'. The film thickness deviation correction is achieved by changing the film strip conveying speed by adjusting the slow roller speed, thereby indirectly adjusting the differential speed ratio within the same group.

[0087] The differential calendering method of the present invention monitors the thickness of the diaphragm in real time through a thickness monitoring mechanism, and automatically adjusts the calendering parameters according to the thickness deviation. When the diaphragm thickness deviation ΔH ≤ 5%, the current calendering parameters are kept unchanged; when ΔH > 5%, the diaphragm thickness is returned to the target range by adjusting the speed ratio of the differential pressure roller group. Based on the law of conservation of mass, the calendering speed is adjusted using the optimized speed ratio K' to ensure the accuracy of the thickness deviation correction, effectively solving the problem of inconsistent diaphragm thickness and density caused by uneven powder mixing in the prior art, avoiding the risk of diaphragm tearing caused by excessive pressurization in traditional methods, significantly improving the consistency of diaphragm thickness and density, and improving product quality and production efficiency.

[0088] As a preferred embodiment of the present invention, the control mechanism adopts a self-learning algorithm based on a convolutional neural network to perform rolling training on the historical data of the diaphragm thickness and the differential speed of the first differential pressure roller group 21 and the differential speed of the second differential pressure roller group 31 in the past 24 hours, updates the prediction model every 30 minutes, and automatically gives the roller gap compensation amount of the first differential pressure roller group 21 and the second differential pressure roller group 31.

[0089] Using a self-learning algorithm based on a convolutional neural network, the equipment automatically optimizes calendering parameters to adapt to fluctuations in raw materials and process conditions, improving production flexibility and stability. By continuously optimizing calendering parameters, the stability and consistency of product quality are enhanced. Compared with traditional methods, this approach avoids frequent manual adjustments due to fluctuating conditions, reduces production interruptions, and improves production efficiency. Furthermore, through continuous learning and optimization, it significantly improves the stability and consistency of product quality and enhances the flexibility and adaptability of the production process.

[0090] It should be understood that the above embodiments are one or more embodiments of the present invention. There are many other embodiments and variations thereof based on the present invention. The variations and modifications made by ordinary technicians in this industry through the present invention without making groundbreaking innovations all fall within the scope of protection of the present invention.

Claims

1. A dry electrode multi-stage roller-pressing film forming device, characterized by: The invention comprises four primary calendering mechanisms, two secondary calendering mechanisms, a tertiary calendering mechanism and a control mechanism arranged in sequence along the direction of material travel, wherein the output ends of two of the primary calendering mechanisms are connected to the input end of one of the secondary calendering mechanisms, the output ends of the remaining two primary calendering mechanisms are connected to the input end of the remaining secondary calendering mechanism, and the output ends of the two secondary calendering mechanisms are connected to the input end of the tertiary calendering mechanism; the input end of the primary calendering mechanism is connected to a powder hopper for storing and mixing granular powder, and the granular powder is mixed by a mixing hopper before entering the primary calendering mechanism. The fiberized network is coated to form a particle powder coated with a fiberized network. The primary calendering mechanism includes at least one group of pressing rollers for initially calendering the particle powder coated with the fiberized network into a primary membrane sheet. The secondary calendering mechanism includes a first differential pressure roller group for superimposing two layers of the primary membrane sheets and performing differential thinning and calendering to form a secondary membrane sheet. The tertiary calendering mechanism includes a second differential pressure roller group for superimposing two layers of the secondary membrane sheets and performing differential thinning and calendering to form a finished membrane sheet. The pressure roller groups, the first differential pressure roller group, and the second differential pressure roller group are all electrically connected to a control mechanism. The first differential calendering roller group includes a first fast calendering roller, a first slow calendering roller, and a first differential drive device, wherein the first fast calendering roller and the first slow calendering roller are arranged side by side in the horizontal direction, and the first differential drive device is used to drive the first fast calendering roller and the first slow calendering roller to rotate at different linear speeds; The second differential calendering roller group includes a second fast calendering roller, a second slow calendering roller, and a second differential drive device, wherein the second fast calendering roller and the second slow calendering roller are arranged side by side in the horizontal direction, and the second differential drive device is used to drive the second fast calendering roller and the second slow calendering roller to rotate at different linear speeds; The linear speed of the first fast calendering roller is twice that of the first slow calendering roller, and the linear speed of the second fast calendering roller is twice that of the second slow calendering roller.

2. The dry electrode multi-stage roll-pressing film forming equipment according to claim 1, characterized in that: The first-stage calendering mechanism adopts a constant-speed calendering mode to calender the granular powder coated with the fiberized network into a first-stage film. The film thickness output by the first-stage calendering mechanism is set to H1, and the linear speed is v1. The second-stage calendering mechanism adopts a differential-speed calendering mode to input the first-stage film from the first-stage calendering mechanism and thin the film thickness to H2, where H2<H1. The linear speed v2 of the first slow calendering roller of the second-stage calendering mechanism satisfies the following relationship: ； The linear speed of the first fast calendering roller of the secondary calendering mechanism is K1×v2, where K1 is the preset speed ratio of the secondary calendering mechanism; The three-stage calendering mechanism continues to thin the secondary film output by the two-stage calendering mechanism to a thickness of H3, wherein H3<H2. Then the linear speed v3 of the second slow calendering roller of the three-stage calendering mechanism satisfies the following relationship: ； The linear speed of the second fast calendering roller of the three-stage calendering mechanism is K2×v3, where K2 is the preset speed ratio of the three-stage calendering mechanism.

3. The dry electrode multi-stage roll-pressing film forming equipment according to claim 1, characterized in that: It also includes a number of confluence guide devices, which are horizontally arranged at the input ends of the secondary calendering mechanism and the tertiary calendering mechanism, and are respectively connected to the output ends of the primary calendering mechanism and the secondary calendering mechanism, for receiving the primary diaphragm from the primary calendering mechanism and the secondary diaphragm from the secondary calendering mechanism, and guiding the primary diaphragm and the secondary diaphragm in a horizontal posture into the secondary calendering mechanism and the tertiary calendering mechanism for differential thinning and calendering.

4. The dry electrode multi-stage roll-pressing film forming equipment according to claim 1, characterized in that: The first-stage calendering mechanism, the second-stage calendering mechanism and the third-stage calendering mechanism are all fixed by a frame, and a number of film tension adjustment guide rollers are provided between the first-stage calendering mechanism and the second-stage calendering mechanism, and between the second-stage calendering mechanism and the third-stage calendering mechanism. The output end of the third-stage calendering mechanism is provided with a film winding mechanism electrically connected to the control mechanism, which is used to collect and wind the finished film into a roll. The control mechanism can adjust the rotation speed of the film winding mechanism to match the output speed of the finished film.

5. The dry electrode multi-stage roll-pressing film forming equipment according to claim 1, characterized in that: It also includes several thickness monitoring mechanisms, which are respectively arranged at the output ends of the first-stage calendering mechanism, the second-stage calendering mechanism and the third-stage calendering mechanism, and are used to monitor the thickness of the output membrane in real time and transmit the thickness signal to the control mechanism. The control mechanism automatically adjusts the pressure and linear speed ratio between the pressure roller group and the first differential pressure roller group, and the pressure and linear speed ratio between the first differential pressure roller group and the second differential pressure roller group according to the thickness signal.

6. A differential rolling method for a dry electrode multi-stage roll-pressing film forming device, characterized in that: For the dry electrode multi-stage roll-pressing film forming equipment according to claim 1, the differential rolling method comprises the following steps: S1. Preparation of powder fiberization coating: fully mixing the active material, conductive agent and PTFE fiber in the powder hopper, so that the PTFE fiber self-assembles on the particle surface to form a three-dimensional coating network, thereby obtaining a particle powder coated with a fiberized network; S2, primary calendering collaborative film formation: the four primary calendering mechanisms perform primary calendering on the fibrous network-coated granular powder obtained in step S1 at a constant roller gap and a constant speed roller surface to obtain a primary film with uniform thickness and self-sustaining strength; S3, secondary differential superposition calendering: The two groups of the first-level membrane sheets are respectively introduced into the inlets of the two first differential pressure roller groups in a horizontal posture, aligned, tensioned and curling eliminated, and differential calendering is performed with the linear speed of the first fast calendering roller being twice that of the first slow calendering roller and the linear speed of the first fast calendering roller being twice that of the pressure roller group, so that the two layers of the first-level membrane sheets are stacked and stretched and thinned synchronously to obtain a secondary membrane sheet; S4, first online thickness-density closed-loop calibration: The thickness and surface density of the secondary diaphragm are measured in real time using a thickness monitoring mechanism, and the data are transmitted back to the control mechanism, which adaptively adjusts the roller gap, pressure, and linear speed ratio of the first differential pressure roller group; S5, three-stage differential superposition calendering: the two layers of the secondary membrane are subjected to a second differential calendering in the second differential calendering roller group, with the linear speed of the second fast calendering roller being twice that of the second slow calendering roller and the linear speed of the second fast calendering roller being twice that of the first fast calendering roller, to further densify and lock the fiber network structure, thereby forming a finished membrane of target thickness; S6. Second online thickness-density closed-loop correction: The thickness and surface density of the finished film are measured in real time by a thickness monitoring mechanism, and the data are transmitted back to the control mechanism. The control mechanism adaptively adjusts the roller gap, pressure and linear speed ratio of the second differential pressure roller group.

7. The differential rolling method of the dry electrode multi-stage roll-pressing film forming equipment according to claim 6, characterized in that: In steps S4 and S6, the thickness monitoring mechanism monitors the actual thickness in real time as H c , the target thickness of the diaphragm is H0, and the diaphragm thickness deviation ΔH is calculated to satisfy the following relationship: ； When the diaphragm thickness deviation is ΔH≤5%, the control mechanism maintains the currently set calendering parameters unchanged and continues the calendering operation; when the diaphragm thickness deviation is ΔH>5%, the control mechanism correspondingly prioritizes adjusting the speed ratio of the first differential pressure roller group and / or the second differential pressure roller group to return the diaphragm thickness to the target range; According to the law of conservation of mass, the instantaneous mass flow m of the material in the calendering zone is constant, which can be expressed as the following relationship: ； Where ρ is the film density, w is the film width, ρ and w are both considered constant, v is the surface linear velocity of the slow calendering roller, and H is the actual thickness of the film; the optimized speed ratio K'=(K0×H0) / H c , where K0 is the current speed ratio, which represents the linear speed ratio of the first fast calendering roller to the first slow calendering roller, or the linear speed ratio of the second fast calendering roller to the second slow calendering roller. The speed ratio of the first differential pressure roller group or the second differential pressure roller group is adjusted according to the obtained optimized speed ratio K'. The film thickness deviation correction is to change the film strip conveying speed by adjusting the slow roller speed, thereby indirectly adjusting the differential speed ratio within the same group.

8. The differential speed rolling method of the dry electrode multi-stage roll-pressing film forming equipment according to claim 6, characterized in that: The control mechanism adopts a self-learning algorithm based on a convolutional neural network to perform rolling training on the historical data of the diaphragm thickness and the differential speed of the first differential pressure roller group and the differential speed of the second differential pressure roller group over the past 24 hours, updates the prediction model every 30 minutes, and automatically provides the roller gap compensation amount of the first differential pressure roller group and the second differential pressure roller group.

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