Dry-method membrane preparation device for preparing lithium battery pole piece

Abstract

The invention relates to the technical field of dry rolling of electrodes of lithium batteries, and discloses a dry membrane preparation device for preparing a lithium battery pole piece, which is characterized by comprising: a plane calendering mechanism capable of performing primary calendering on dry electrode powder in a surface contact calendering mode to form an initial membrane; and the multi-rolling mechanism is arranged on the discharging side of the plane rolling mechanism and used for receiving the initial membrane, the multi-rolling mechanism comprises a plurality of rolling structures which are arranged in series, the rolling gaps between the adjacent rolling structures are gradually reduced step by step, and the multi-rolling mechanism is used for carrying out gradual thinning rolling on the initial membrane to form a target membrane. Through the synergistic effect of'plane calendering preliminary forming 'and'multiple progressive rolling finishing', the lithium battery dry-method electrode diaphragm which is high in density, uniform in structure, excellent in interface performance and controllable in thickness can be efficiently and stably prepared; the dry-method membrane preparation device effectively solves the technical problems that powder is difficult to form, easy to crack, low in thickness and density control precision and the like in a dry-method membrane preparation process.

Description

Technical Field

[0001] This application relates to the field of dry rolling technology for lithium battery electrodes, and particularly to a dry film-forming apparatus for preparing lithium battery electrodes. Background Technology

[0002] Solid-state lithium battery electrode fabrication processes include wet and dry film fabrication. Dry film fabrication has advantages over wet film fabrication in terms of cost, process simplicity, environmental friendliness, and suitability for large-scale production. The dry process eliminates the need for solvents such as NMP, saving energy consumption and recycling costs, thus reducing production costs and environmental pollution. Furthermore, dry film fabrication can achieve higher active material compaction density and smoother electrode morphology, thereby improving the battery's energy density and electrical performance.

[0003] In existing processes, dry film preparation requires thoroughly mixing electrode powders, followed by calendering to form an electrode film, and then rolling to coat the electrode film onto a foil to obtain an electrode sheet.

[0004] Existing equipment directly rolls the electrode powder after mixing. Since the electrode powder is relatively loose at this time, the electrode film formed by direct rolling is prone to having holes, which is not conducive to maintaining the integrity of the film. In addition, the current rolling equipment lacks control over the calendering process of the electrode film and cannot gradually thin the electrode film according to manufacturing needs and make more precise adjustments to the calendering thickness. Summary of the Invention

[0005] To address the aforementioned problems, this application provides a dry film-forming apparatus for preparing lithium battery electrodes, comprising: The planar calendering mechanism can perform initial calendering of dry electrode powder to form an initial film through a surface contact calendering method; A multi-roll pressing mechanism is disposed on the discharge side of the planar calendering mechanism for receiving the initial film. The multi-roll pressing mechanism includes multiple rolling structures arranged in series, with the calendering gap between adjacent rolling structures decreasing progressively. It is used to progressively thin the initial film by rolling to form the target film.

[0006] Preferably, the planar calendering mechanism includes a first pre-pressing component and a second pre-pressing component disposed opposite to each other, a first calendering gap is formed between the first pre-pressing component and the second pre-pressing component, the first calendering gap is used to perform initial calendering on the dry electrode powder, and the first pre-pressing component can move relative to the second pre-pressing component to adjust the size of the first calendering gap.

[0007] Preferably, the first pre-pressing assembly includes a first drive roller group, a first moving belt, and a first size adjustment member. The first moving belt is sleeved on the first drive roller group and can move under the driving action of the first drive roller group to convey and calender the dry electrode powder. The first size adjustment member is connected to the first moving belt and is used to drive the first moving belt to move to adjust the size of the first calendering gap. And / or, the second pre-compression assembly includes a second drive roller group, a second moving belt, and a fixed roller group, wherein the first calendering gap is formed between the second moving belt and the first moving belt, the second moving belt is sleeved on the second drive roller group and can move under the driving action of the second drive roller group to convey the dry electrode powder; the second moving belt is laid on the fixed roller group, and the fixed roller group is used to limit the movement of the second moving belt.

[0008] Preferably, the multi-roll pressing mechanism includes an upper calendering assembly and a lower calendering assembly arranged opposite each other, with a second calendering gap formed between the upper calendering assembly and the lower calendering assembly. The size of the second calendering gap decreases progressively along the conveying direction of the initial film. The upper calendering assembly can move relative to the lower calendering assembly to adjust the size of the second calendering gap.

[0009] Preferably, the upper calendering assembly includes an upper calendering drive, an upper roller assembly, and a second size adjustment component. The upper roller assembly and the upper calendering drive are connected by a transmission connection and can move under the driving action of the upper calendering drive to convey and calender the initial film. The second size adjustment component is connected to the upper roller assembly and is used to drive the upper roller assembly to move to adjust the size of the second calendering gap. The lower calendering assembly includes a lower calendering drive and a lower roller group. A second calendering gap is formed between the lower roller group and the upper roller group. The lower roller group and the lower calendering drive are connected in a driving relationship. The lower roller group can move under the driving action of the lower calendering drive to transport the initial film. The upper roller group and the lower roller group each include multiple rollers. The rollers of the upper roller group and the rollers of the lower roller group are arranged correspondingly to form the rolling structure. The multiple rolling structures are arranged sequentially at intervals along the conveying direction of the initial film.

[0010] Preferably, the second size adjustment member is configured to adjust the tilt angle of the upper roller group relative to the lower roller group, such that the second calendering gap has a tapered structure in the conveying direction of the initial film; Along the conveying direction of the initial film, the second size adjustment member includes adjustment units disposed at least at both ends of the upper roller assembly for adjusting the relative positions of the two ends of the upper roller assembly.

[0011] Preferably, the roller diameter of the upper roller group is different from that of the lower roller group.

[0012] Preferably, the multi-roller mechanism further includes a gap detection component disposed at the initial end and / or end of the initial film conveying direction for detecting the size of the second calendering gap.

[0013] Preferably, the dry film-forming apparatus further includes a feeding mechanism disposed at the feeding end of the planar calendering mechanism for receiving and conveying the dry electrode powder to the planar calendering mechanism; The feeding mechanism includes a feeding bin and a feeding roller assembly. The feeding roller assembly is located at the outlet of the feeding bin and is used to transport the dry electrode powder to the planar calendering mechanism.

[0014] Preferably, the dry film-forming apparatus further includes: An edge cutting mechanism is provided on the discharge side of the multi-roller pressing mechanism for cutting the edge of the target film. The edge cutting mechanism includes an upper edge cutting roller, a lower edge cutting roller, and an edge collecting groove. The upper edge cutting roller and the lower edge cutting roller are arranged opposite to each other, and the edge collecting groove is located below the lower edge cutting roller for collecting the cut edge material. A film-belt laminating mechanism is disposed on the side of the edge material cutting mechanism away from the multi-roll pressing mechanism. The film-belt laminating mechanism includes an upper laminating clamping roller, a lower laminating clamping roller, and a current collector base belt. The upper laminating clamping roller and the lower laminating clamping roller are disposed opposite to each other. The current collector base belt is sandwiched between the upper laminating clamping roller and the lower laminating clamping roller. The film-belt laminating mechanism is used to laminate the target film onto the current collector.

[0015] Based on the above technical solution, the dry film-forming apparatus for preparing lithium battery electrodes described in this application has the following beneficial effects: This application utilizes the synergistic effect of "planar calendering preliminary forming" and "multiple progressive roll pressing finishing" to efficiently and stably prepare high-density, uniformly structured, excellent interfacial properties, and controllable thickness dry electrode films for lithium batteries. This dry film-forming device effectively solves key technical problems in the dry film-forming process, such as difficulty in powder forming, easy cracking, and low accuracy in thickness and density control. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0017] Figure 1 This is a schematic diagram of the overall structure of the dry film-forming apparatus provided in the embodiments of this application.

[0018] Figure 2 This is a front view of the dry film-forming apparatus provided in the embodiments of this application.

[0019] Figure 3 This is a partial enlarged view of the multi-roller pressing mechanism provided in this application embodiment, located at the junction of the upper and lower roller groups.

[0020] Figure 4 This is a schematic diagram of the upper and lower rollers of the edge cutting knife in the edge cutting mechanism provided in the embodiments of this application.

[0021] The reference numerals in the attached drawings are as follows: 100, dry film-forming apparatus; 20, feeding mechanism; 21, feeding hopper; 22, feeding roller pair; 30, planar calendering mechanism; 31, first pre-pressing assembly; 311, first drive roller group; 312, first moving belt; 313, first size adjustment component; 32, second pre-pressing assembly; 321, second drive roller group; 322, second moving belt; 323, fixed roller group; 40, multi-roll pressing mechanism; 41, upper calendering assembly; 42, 43, 44, 45, 46, 47, 48, 49 ... 1. Upper roller assembly; 412. Second dimension adjustment component; 413. Adjustment unit; 42. Lower calendering assembly; 421. Lower roller assembly; 43. Roller; 44. Gap detection assembly; 45. Scraper; 50. Edge cutting mechanism; 51. Upper edge cutter roller; 52. Lower edge cutter roller; 53. Edge collection trough; 60. Film belt lamination mechanism; 61. Upper lamination pinch roller; 62. Lower lamination pinch roller; 63. Current collector base belt; 70. Target film; P. Conveying direction. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. In the description of this application, it should be understood that the terms "upper," "lower," "left," "right," "top," "bottom," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0024] In dry film-forming processes, the core lies in the direct use of dry, loose electrode powder, relying entirely on physical mechanical compaction rather than solvent-assisted molding. While this material and process characteristic brings cost and environmental advantages, it also presents unique technical challenges. For example, loose powder directly subjected to concentrated roller pressure is prone to developing pores due to uneven densification. Furthermore, there is a lack of effective equipment for continuous and controllable progressive thinning of pure solid films. Therefore, to address the problems of "incomplete films" and "uncontrollable calendering process" caused by the inherent characteristics of dry film-forming processes, this invention proposes the following technical solutions: like Figures 1-4 As shown in the figure, this application discloses a dry film-forming apparatus 100 for preparing lithium battery electrodes, characterized in that it includes: The planar calendering mechanism 30 is capable of performing initial calendering of dry electrode powder to form an initial film through a surface contact calendering method. A multi-roll pressing mechanism 40 is disposed on the discharge side of the planar calendering mechanism 30 for receiving the initial film. The multi-roll pressing mechanism 40 includes multiple rolling structures arranged in series, with the calendering gap between adjacent rolling structures decreasing step by step, for progressively thinning the initial film to form the target film 70.

[0025] Understandably, the fundamental characteristic of dry film-forming technology lies in its complete elimination of solvents, directly using dry electrode powder composed of active materials, conductive agents, and binders (such as PTFE) as raw materials. This characteristic brings a dual impact: on the one hand, it avoids the high energy consumption, high cost, and environmental pollution problems caused by the use of solvents in wet processes, and eliminates defects such as electrode delamination caused by solvent evaporation; on the other hand, its core process conditions are purely physical mechanical forming, which does not depend on the flow and evaporation of solvents, but relies entirely on mechanical forces such as pressure and shear force to compact and densify the loose dry electrode powder and form a self-supporting film with sufficient strength and continuity. This process places extremely high demands on the way mechanical force is applied, the control precision, and the gradualness. When dry electrode powder is directly subjected to high pressure, it is very easy to generate pores and cracks due to uneven stress, and it is difficult to achieve high uniformity and high density in one-time forming.

[0026] In this embodiment, the planar calendering mechanism 30 is used to perform initial calendering on completely loose dry electrode powder through surface contact. First, the surface contact differs from the line contact of the traditional hard roller 43. Surface contact can provide more uniform and gentler initial pressure, avoiding splashing of dry electrode powder or uneven density of the initial film due to excessive local pressure. This helps to initially integrate the loose powder into an initial film with a certain strength and integrity. Second, unlike direct high-pressure rolling, the planar calendering mechanism 30 achieves preliminary densification and pre-forming of the dry electrode powder through large-area, relatively gentle surface contact pressure. This step can initially integrate the loose dry electrode powder into an "initial film" with a certain integrity and initial strength, creating a structural foundation for subsequent high-precision rolling. This avoids the loose dry electrode powder being directly "squeezed apart" or subjected to uneven force in the subsequent high-pressure roll gap, thereby reducing the generation of incomplete defects such as holes and cracks from the source.

[0027] In this embodiment, the contact surface between the first moving belt 312 and the dry electrode powder is provided with an elastic material, so that it can form a "dynamic horizontal contact surface" when the dry electrode powder is squeezed against each other, thereby achieving surface contact with the dry electrode powder.

[0028] In this embodiment, the multi-roll pressing mechanism 40 receives the "initial film" pre-formed by planar calendering and performs at least two roll pressings to achieve the concept of progressive compaction. The multi-roll pressing mechanism 40 includes multiple sets of roll pressing structures arranged in series to form a "multi-pass" continuous processing. The design of "gradually decreasing calendering gaps between adjacent roll pressing structures" and "progressive thinning roll pressing" enables gradual and controllable compression of the initial film. Furthermore, in the binder fibrillation process, the binder needs to form a three-dimensional fiber network under shear force and pressure to bond the active material particles. A single large-deformation roll pressing may lead to stress concentration between powder particles, damage to the binder fiber network, and inaccurate thickness control.

[0029] By employing the progressive rolling pressing method described in this application, air between powder particles can be expelled more smoothly, resulting in a denser arrangement of active material particles. This avoids internal structural damage or cracking caused by excessive pressure in a single pass. Furthermore, the overall compaction deformation can be decomposed into multiple smaller, controllable steps, allowing each rolling press to progressively increase the compaction density of the initial membrane. Simultaneously, by precisely controlling the roller gap in each pass, the initial membrane can be guided to flow smoothly, resulting in a more uniform internal structure. Moreover, the progressive thinning also facilitates the uniform extension and redistribution of the binder's fiber network under pressure, binding the active particles and conductive agent more firmly together to form a stable and uniform electrode structure. This suppresses electrode delamination, effectively improving not only the compaction density and mechanical strength of the final target membrane 70 but also enabling precise control over the initial membrane thickness and surface flatness, thereby obtaining an electrode with superior and more uniform electrical performance.

[0030] Therefore, the dry film-forming process fundamentally avoids the cost, energy consumption, and pollution problems associated with solvent use, and eliminates electrode delamination defects caused by solvent evaporation in wet processes, laying the foundation for the preparation of thick electrodes. Furthermore, the dry film-forming device 100 employs a "surface contact" planar calendering mechanism 30 at its front end, which gently integrates the loose, poorly flowing dry electrode powder, avoiding uneven powder agglomeration or film tearing caused by stress concentration in the initial stage, thus forming an "initial film" preform suitable for subsequent fine processing.

[0031] Subsequently, the design of the multi-roll pressing mechanism with 40 passes enables continuous production and improves efficiency. The progressively decreasing gap between adjacent calendering stages, through gradual thinning during rolling, allows the initial film to undergo a smooth transition from loose to dense. During this process, powder particles are gradually rearranged, and pores are slowly eliminated. This is particularly beneficial for the formation of the fibrillated network of the binder in the dry electrode. Compared to single-stage high-pressure compaction, this gradual compaction more effectively releases internal stress, greatly reducing the risk of internal cracks in the initial film during rolling, thus producing a crack-free, homogeneous, thick electrode.

[0032] Finally, by precisely controlling the gap of the last rolling process, a "target diaphragm 70" with uniform thickness, smooth surface, and high compaction density can be obtained. This diaphragm structure is dense and uniform, which is conducive to building an efficient electron conduction network, thereby improving the rate performance and cycle life of the battery.

[0033] In summary, this application, through the synergistic effect of "planar calendering preliminary forming" and "multiple progressive roll pressing finishing", can efficiently and stably prepare high-density, uniformly structured, excellent interfacial performance, and controllable thickness dry electrode films for lithium batteries. The dry film-forming device 100 effectively solves the key technical problems in the dry film-forming process, such as difficulty in powder forming, easy cracking, and low accuracy in thickness and density control.

[0034] like Figure 2 As shown, the planar calendering mechanism 30 includes a first pre-pressing component 31 and a second pre-pressing component 32 disposed opposite to each other. A first calendering gap is formed between the first pre-pressing component 31 and the second pre-pressing component 32. The first calendering gap is used to perform initial calendering on the dry electrode powder. The first pre-pressing component 31 can move relative to the second pre-pressing component 32 to adjust the size of the first calendering gap.

[0035] Understandably, the first pre-pressing component 31 and the second pre-pressing component 32 are arranged opposite each other to form a first calendering gap, constituting a basic rolling or pressing unit. In the dry electrode process, the initial dry electrode powder is a solid mixture of active material, conductive agent, and binder, with poor flowability and lack of cohesion. This surface-contact first calendering gap can apply an initial, relatively uniform pressure to the powder, acting as a pre-pressing roller, with the purpose of initially integrating the loose dry electrode powder into an initial film with a certain integrity and self-sustaining strength.

[0036] Understandably, the first pre-compression component 31 can move relative to the second pre-compression component 32 to adjust the size of the first calendering gap, which is the core of the planar calendering mechanism 30 to achieve process adaptability and control precision. By adjusting the size of the first calendering gap, the initial calendering force and compression ratio applied to the powder can be precisely controlled, which can directly affect the "areal density" and "compacted density" of the initial film.

[0037] Therefore, the "first calendering gap," formed by the two opposing pre-pressing components, provides a preliminary forming channel for the loose, poorly flowing dry electrode powder, transforming it from a three-dimensional powder into a two-dimensional film. This channel determines the basic structure and uniformity of the initial film. The technical feature of "adjustable first calendering gap size" enhances the adaptability of the planar calendering mechanism 30. Because in dry film-making processes, the mixing uniformity of the powder, the degree of fibrillation of the binder, and the performance requirements of the target product are all variables, operators can compensate for batch-to-batch differences in powder or actively optimize the compression ratio of the initial calendering by adjusting the gap in real time and precisely. This directly controls the thickness and initial compaction density of the initial film, thus avoiding problems such as uneven film surface density, localized looseness, or over-pressure cracking caused by fixed initial calendering parameters. This ensures that the initial film entering the subsequent multi-roll pressing mechanism 40 for progressive thinning has a consistent and good quality starting point, guaranteeing the performance uniformity and production yield of the final target film 70.

[0038] In a preferred embodiment, the first pre-pressing assembly 31 includes a first drive roller group 311, a first moving belt 312, and a first size adjustment member 313. The first moving belt 312 is sleeved on the first drive roller group 311 and can move under the driving action of the first drive roller group 311 to convey and calender the dry electrode powder. The first size adjustment member 313 is connected to the first moving belt 312 and is used to drive the first moving belt 312 to move to adjust the size of the first calendering gap.

[0039] Understandably, in the first pre-compression assembly 31, the first drive roller group 311 drives the first moving belt 312 to move cyclically, making it a dynamic conveying and calendering working surface. The first size adjustment element 313 is connected to the first moving belt 312 to precisely control its position. In the dry film-forming process, the electrode powder is a solid mixture of active material, conductive agent, and binder, with poor flowability and lack of cohesion. Therefore, this movable belt calendering surface, compared to a fixed pressure plate, can continuously and stably convey and contact the powder, avoiding powder accumulation or poor conveying, while also providing a basis for adjusting the calendering force.

[0040] And / or, the second pre-compression assembly 32 includes a second drive roller group 321, a second moving belt 322, and a fixed roller group 323. The first calendering gap is formed between the second moving belt 322 and the first moving belt 312. The second moving belt 322 is sleeved on the second drive roller group 321 and can move under the driving action of the second drive roller group 321 to convey the dry electrode powder. The second moving belt 322 is placed on the fixed roller group 323, and the fixed roller group 323 is used to limit the movement of the second moving belt 322.

[0041] In this embodiment, the first pre-compression component 31 and the second pre-compression component 32 with the above-described structural form are included.

[0042] In this embodiment of the application, both the first moving belt 312 and the second moving belt 322 are metal steel belts.

[0043] Understandably, in the second pre-compression assembly 32, a first calendering gap is formed between the second moving belt 322 and the first moving belt 312. The second moving belt 322 is also driven by the second drive roller group 321, ensuring synchronous or coordinated conveying with the first moving belt 312. This is crucial for maintaining the tension stability and surface quality of the powder or initial film during the calendering process. The fixed roller group 323 provides support and limits for the second moving belt 322, ensuring it maintains a stable running trajectory and flatness during calendering, preventing deformation or vibration of the second moving belt 322, thereby ensuring the uniformity of the calendering gap.

[0044] In this embodiment, the first size adjustment member 313 is a pressing cylinder, which can drive the position of the first moving belt 312 relative to the second moving belt 322 in the vertical direction, change the size of the first calendering gap, and thus change the calendering force on the dry electrode powder.

[0045] In this embodiment, the first size adjustment member 313, used to move the first moving belt 312 to adjust the size of the first calendering gap, is the core of achieving process adaptability and precise control. By adjusting the position of the first moving belt 312, the size of the first calendering gap can be changed precisely and continuously, thereby changing the initial calendering force and compression ratio applied to the dry electrode powder. This is a key means of controlling the initial film's "areal density" and "compacted density," providing a uniform and controllable blank foundation for subsequent multiple rolling processes.

[0046] In this embodiment, the first drive roller group 311 and the second drive roller group 321 each include a drive motor and a rotating roller 43. The output shaft of the drive motor is connected to the rotating roller 43 to drive the rotating roller 43 to rotate, thereby driving the movable belt sleeved on it to rotate.

[0047] In this embodiment, the fixed roller group 323 also includes a plurality of rollers 43, which are arranged sequentially at intervals along the conveying direction P of the dry electrode powder. The fixed roller group 323 is correspondingly arranged below the rotating rollers 43 that are also arranged at intervals along the conveying direction P of the dry electrode powder in the first drive roller group 311, and the two constitute the first calendering gap.

[0048] In this embodiment, each rotating roller 43 in the fixed roller group 323 is also connected to the output shaft of the drive motor in the second drive roller group 321. In other embodiments, each rotating roller 43 in the fixed roller group 323 and the rotating roller 43 in the second drive roller group 321 can also be controlled separately and individually.

[0049] Therefore, the planar calendering mechanism 30, by employing dual moving belts for coordinated conveying and calendering and integrating an adjustable gap structure, provides the dry film-forming process with the ability to perform high-precision and flexible control over the initial forming process. This design ensures that loose, dry electrode powder can be smoothly and uniformly compacted initially, forming an initial film with consistent quality and suitable strength, fundamentally improving the process stability and product uniformity of dry film-forming.

[0050] like Figures 2-3 As shown, the multi-roller mechanism 40 includes an upper calendering assembly 41 and a lower calendering assembly 42 arranged opposite to each other. A second calendering gap is formed between the upper calendering assembly 41 and the lower calendering assembly 42. The size of the second calendering gap decreases step by step along the conveying direction P of the initial film. The upper calendering assembly 41 can move relative to the lower calendering assembly 42 to adjust the size of the second calendering gap.

[0051] Understandably, if only a single or equal-gap rolling process is used, loose powder or a pre-formed diaphragm will suffer excessive deformation at once, leading to internal stress concentration, uneven density, or even tearing. Therefore, by setting progressively decreasing gaps, the initial diaphragm undergoes multiple, gradual compressions during its journey. For example, by setting up a sequentially arranged first-, second-, and third-stage rolling structure, the thickness of the initial diaphragm is gradually reduced from h1 to h2 (h2...

[0052] Understandably, by precisely adjusting the second calendering gap, the compression ratio and final pressure of each roll pressing structure can be flexibly controlled.

[0053] Therefore, through its adjustable and progressively decreasing second calendering gap design, the dry film-making process is provided with the ability to controllably and progressively perform precision rolling on the initial film. This design effectively solves the problems of uneven density, difficulty in thickness control, and easy breakage of films that are easy to occur when dry electrode powder is directly formed. It can stably produce high-quality electrode films with high compaction density, high thickness uniformity, and complete structure.

[0054] ​In a preferred embodiment, the upper calendering assembly 41 includes an upper calendering drive, an upper roller assembly 411, and a second size adjustment component 412. The upper roller assembly 411 is convexly connected to the upper calendering drive and can move under the driving action of the upper calendering drive to convey and calender the initial film. The second size adjustment component 412 is connected to the upper roller assembly 411 and is used to drive the upper roller assembly 411 to move to adjust the size of the second calendering gap. The lower calendering assembly 42 includes a lower calendering drive and a lower roller group 421. A second calendering gap is formed between the lower roller group 421 and the upper roller group 411. The lower roller group 421 is connected to the lower calendering drive. The lower roller group 421 can move under the driving action of the lower calendering drive to transport the initial film. The upper roller group 411 and the lower roller group 421 each include multiple rollers 43. The rollers 43 of the upper roller group 411 and the rollers 43 of the lower roller group 421 are correspondingly arranged to form the rolling structure. The multiple rolling structures are arranged sequentially at intervals along the conveying direction P of the initial film.

[0055] In this embodiment, the lower calendering assembly 42 further includes a scraper 45 disposed on the lower roller group 421 for scraping the initial film based on thickness requirements.

[0056] Understandably, by adjusting the position of the upper roller group 411, the gap size of each "roller pressing structure" can be precisely set. Furthermore, combined with the design of "multiple roller pressing structures arranged sequentially", the operator can precisely set a gap sequence that decreases step by step along the conveying direction P, thereby achieving "gradual thinning". This adjustability allows the dry film forming device 100 to flexibly adapt to the production requirements of different target thicknesses and compaction densities.

[0057] In a possible embodiment, the driving of the upper calendering drive member on the upper roll group 411 and the driving of the lower calendering drive member on the lower roll group 421 can be driven independently or in concert.

[0058] Understandably, by creating a linear velocity difference between the upper and lower rollers 43, a shear force can be introduced during the calendering process. This shear force helps to further fibrillate the binder in dry film making, forming a stronger three-dimensional network structure, thereby more effectively bonding the active material particles and improving the mechanical strength and conductivity uniformity of the electrode film.

[0059] Therefore, the upper calendering assembly 41 and the lower calendering assembly 42, through their multi-roller 43, multi-pass adjustable gap arrangement structure and independent driving capability, together constitute a rolling system capable of precisely, progressively and introducing shear force on the initial film. This design effectively solves the technical problems of uneven density, difficulty in thickness control and insufficient binder networking in direct dry powder calendering, and can stably produce high-quality electrode films with high compaction density, high uniformity and complete structure.

[0060] As a preferred implementation method, such as Figure 3 As shown, the second size adjustment member 412 is configured to adjust the tilt angle α of the upper roller group 411 relative to the lower roller group 421, so that the second calendering gap has a tapered structure in the conveying direction P of the initial film.

[0061] It is understood that the tapered structure is a funnel-shaped structure with a wide inlet and a narrow outlet along the conveying direction P of the initial membrane, so as to gradually thin the initial membrane to the required thickness.

[0062] Understandably, by adjusting the tilt angle α of the upper roller group 411, a "trumpet-shaped" or "gradually narrowing" gap with a wide inlet and a narrow outlet can be formed between it and the lower roller group 421. This design decomposes the overall thinning target into a continuous process with a gradually increasing compression ratio, allowing the fiber network of the binder to extend and reorganize more smoothly under shear force, thereby bonding the active particles together more evenly and firmly, and improving the uniformity of density distribution inside the membrane.

[0063] Furthermore, along the conveying direction P of the initial film, the second size adjustment member 412 includes adjustment units 413 at least disposed at both ends of the upper roller group 411 for adjusting the relative positions of the two ends of the upper roller group 411.

[0064] Understandably, this is the specific technical solution for achieving the above-mentioned tilt angle α adjustment and ensuring gap uniformity. This "adjustment unit 413" with independent adjustment at both ends allows the operator to precisely control the inlet and outlet gap of the "gradually narrowing structure" and compensate for gap unevenness caused by changes in pressure in real time, ensuring the ultimate uniformity of the diaphragm's lateral thickness.

[0065] In this embodiment, the adjustment unit 413 includes a lifter, an arc block, and a worm gear transmission that achieves mechanical self-locking. This is prior art and will not be described in detail here.

[0066] Therefore, the second size adjustment component 412, through its design that can precisely control the tilt angle α of the upper roller group 411 and the relative position of both ends, provides a precise solution for the dry film-making process with a continuous and controllable gradually shrinking gap from the inlet to the outlet.

[0067] In this embodiment of the application, the diameter of the roller 43 of the upper roller group 411 is different from the diameter of the roller 43 of the lower roller group 421.

[0068] Understandably, the core binder of the dry electrode requires shear force to fully fibrillate and form a three-dimensional network structure encapsulating the active material particles. When the upper and lower rollers 43 have different diameters, even if they are driven to rotate at the same angular velocity, their roller surface linear velocities will differ. This difference in linear velocity creates a strong shear force in the roller gap, and this shear force field can more effectively stretch and extend the fibers, making them more evenly distributed among the active material particles, thereby significantly improving the mechanical strength and internal bonding force of the electrode film. Furthermore, the introduction of differential velocity, i.e., the difference in linear velocity caused by the different diameters, promotes the rearrangement and densification of powder particles in the calendering direction, helping to break up local agglomerations and making the compaction process more uniform.

[0069] like Figure 2 As shown, the multi-roller mechanism 40 further includes a gap detection component 44, which is disposed at the initial end and / or the end of the initial film conveying direction P, for detecting the size of the second calendering gap.

[0070] In this embodiment, the gap detection component 44 is a ranging sensor.

[0071] Understandably, the progressive thinning effect of the dry electrode relies entirely on the precise setting of the "second calendering gap" sequence, which decreases step by step along the conveying direction P. The gap detection component 44 can directly measure the actual gap between the pressure roller and the bearing surface (or another pressure roller). By setting the gap detection component 44 at the initial end, the starting gap of the first rolling structure can be precisely set; by setting the gap detection component 44 at the end, the exit gap of the final rolling structure can be monitored, i.e., the thickness reference of the final film. This real-time detection function allows the operator or control system to grasp the true state of the second calendering gap at any time, thereby ensuring that the reference parameters of the entire multi-pass rolling process are always within the set range.

[0072] like Figure 2 As shown, the dry film-forming apparatus 100 also includes a feeding mechanism 20, which is disposed at the feeding end of the planar calendering mechanism 30, for receiving and conveying the dry electrode powder to the planar calendering mechanism 30. The feeding mechanism 20 includes a feeding bin 21 and a feeding roller pair 22. The feeding roller pair 22 is disposed at the discharge port of the feeding bin 21 and is used to transport the dry electrode powder to the planar calendering mechanism 30.

[0073] In this embodiment, the feeding mechanism 20 is used to receive and transport dry electrode powder, which is the starting point of the entire dry film-making process. Its design needs to adapt to the characteristics of dry electrode powder, which has good flowability but no cohesive force, to ensure that the dry electrode powder can be continuously, stably and uniformly supplied to the subsequent forming station, laying the foundation for subsequent uniform calendering.

[0074] As can be understood, as mentioned above, the core of the dry film-forming process is to directly press dry electrode powder into a film. Unlike wet slurry, dry powder has poor flowability and is prone to agglomeration. Traditional feeding methods are prone to uneven delivery and interruption of supply, which directly leads to instability in the film-forming process and makes the film prone to defects, holes, and cracks. The "feeding bin 21" in this application, as an intermediate buffer and storage unit, can receive and temporarily store the mixed powder, providing material reserves for subsequent continuous calendering. The "feeding roller pair 22" is a mechanical conveying device that can actively and controllably push the dry electrode powder from the outlet of the feeding bin 21 to the planar calendering mechanism 30, replacing the unstable method of relying on the powder's own weight or airflow, and ensuring that the dry electrode powder can enter the forming area at a continuous and stable flow rate.

[0075] Furthermore, dry film production requires extremely high uniformity of the dry electrode powder before calendering. If the dry electrode powder is unevenly distributed before entering the first calendering gap, resulting in accumulation or cavities, even with higher subsequent calendering pressure, it will be impossible to completely eliminate defects such as uneven film thickness, localized low density (soft spots), or pores. The feeding roller pair 22, while conveying the dry electrode powder, can also flatten, compact, and initially shear the powder layer, helping to break up agglomerates and make the powder more evenly distributed in the width direction, forming a relatively flat powder strip with consistent density, which then enters the planar calendering mechanism 30 for initial calendering.

[0076] In a possible embodiment, the feed roller pair 22 consists of one or more pairs of rollers 43 that rotate in opposite directions or at different speeds.

[0077] like Figure 2 As shown, the dry film-forming apparatus 100 further includes: An edge cutting mechanism 50 is disposed on the discharge side of the multi-roller pressing mechanism 40 and is used to cut the edge of the target film 70. The edge cutting mechanism 50 includes an upper edge cutting roller 51, a lower edge cutting roller 52, and an edge collecting groove 53. The upper edge cutting roller 51 and the lower edge cutting roller 52 are disposed opposite to each other, and the edge collecting groove 53 is disposed below the lower edge cutting roller 52 and is used to collect the cut edge material. The film tape laminating mechanism 60 is disposed on the side of the edge material cutting mechanism 50 away from the multi-roll pressing mechanism 40. The film tape laminating mechanism 60 includes an upper laminating clamping roller 61, a lower laminating clamping roller 62, and a current collector base belt 63. The upper laminating clamping roller 61 and the lower laminating clamping roller 62 are disposed opposite to each other, and the current collector base belt 63 is sandwiched between the upper laminating clamping roller 61 and the lower laminating clamping roller 62. The film tape laminating mechanism 60 is used to laminate the target film 70 onto the current collector.

[0078] Understandably, the edge cutting mechanism 50 is located on the discharge side of the multi-roll pressing mechanism 40. Its core consists of a pair of opposing edge cutting upper rollers 51 and lower edge cutting rollers 52, as well as an edge collection groove 53 below. The function of this edge cutting mechanism 50 is to cut off the irregular or excessively wide edge portions on both sides of the "target film 70" formed after multi-roll pressing, so as to obtain a finished film strip with precise width and neat edges, and to collect the waste generated during cutting.

[0079] Understandably, the film-strip lamination mechanism 60 is located behind the edge material cutting mechanism 50, and its core consists of a pair of opposing upper lamination clamping rollers 61 and lower lamination clamping rollers 62, and a current collector base belt 63 passing between them. The function of this film-strip lamination mechanism 60 is to firmly bond the pre-cut target film 70 with the current collector through hot pressing or cold pressing to form the final battery electrode.

[0080] In a possible embodiment, the current collector is an aluminum foil or a copper foil.

[0081] Therefore, the edge cutting mechanism 50 solves the problems of uneven film edges and width during the dry film formation process, ensuring the consistency of the target film 70's dimensions through precise cutting. Simultaneously, its integrated edge collection trough 53 can automatically and centrally collect cutting waste, preventing the scattering and accumulation of edge material on the production line. This not only maintains a clean production environment but, more importantly, allows the edge material, pressed from pure dry powder, to be easily crushed and directly reused in the upstream feeding process, achieving closed-loop utilization of raw materials, significantly reducing production costs and conforming to the concept of green manufacturing.

[0082] The membrane-coating mechanism 60 efficiently and firmly combines the formed electrode membrane with the current collector. It uses a pinch roller pressing method to ensure the uniformity and tightness of the coating process, thereby ensuring the conductivity and structural stability of the electrode.

[0083] The integration of these two mechanisms enables the dry film-making process to complete all key steps from powder compaction, molding, trimming to bonding with the current collector in a coherent equipment flow, greatly simplifying the process, reducing intermediate transfer and storage links, and improving the automation level and overall yield of the production line.

[0084] The foregoing description has fully disclosed the specific embodiments of this application. It should be noted that any modifications made by those skilled in the art to the specific embodiments of this application do not depart from the scope of the claims. Accordingly, the scope of the claims of this application is not limited to the foregoing specific embodiments.

Claims

1. A dry film-forming apparatus for preparing lithium battery electrodes, characterized in that, It includes: The planar calendering mechanism can perform initial calendering of dry electrode powder to form an initial film through a surface contact calendering method; A multi-roll pressing mechanism is disposed on the discharge side of the planar calendering mechanism for receiving the initial film. The multi-roll pressing mechanism includes multiple rolling structures arranged in series, with the calendering gap between adjacent rolling structures decreasing progressively. It is used to progressively thin the initial film by rolling to form the target film.

2. The dry film-forming apparatus according to claim 1, characterized in that, The planar calendering mechanism includes a first pre-pressing component and a second pre-pressing component arranged opposite to each other. A first calendering gap is formed between the first pre-pressing component and the second pre-pressing component. The first calendering gap is used to perform initial calendering on the dry electrode powder. The first pre-pressing component can move relative to the second pre-pressing component to adjust the size of the first calendering gap.

3. The dry film-forming apparatus according to claim 2, characterized in that, The first pre-compression assembly includes a first drive roller group, a first movable belt, and a first size adjustment component. The first movable belt is sleeved on the first drive roller group and can move under the driving action of the first drive roller group to transport and calender the dry electrode powder. The first size adjustment member is connected to the first moving belt, and the first size adjustment member is used to drive the first moving belt to move in order to adjust the size of the first rolling gap; And / or, the second pre-compression assembly includes a second drive roller group, a second moving belt, and a fixed roller group, wherein the first calendering gap is formed between the second moving belt and the first moving belt, the second moving belt is sleeved on the second drive roller group and can move under the driving action of the second drive roller group to convey the dry electrode powder; the second moving belt is laid on the fixed roller group, and the fixed roller group is used to limit the movement of the second moving belt.

4. The dry film-forming apparatus according to claim 1, characterized in that, The multi-roller mechanism includes an upper calendering assembly and a lower calendering assembly arranged opposite each other. A second calendering gap is formed between the upper calendering assembly and the lower calendering assembly. The size of the second calendering gap decreases step by step along the conveying direction of the initial film. The upper calendering assembly can move relative to the lower calendering assembly to adjust the size of the second calendering gap.

5. The dry film-forming apparatus according to claim 4, characterized in that, The upper calendering assembly includes an upper calendering drive, an upper roller assembly, and a second size adjustment component. The upper roller assembly and the upper calendering drive are connected by a transmission and can move under the driving action of the upper calendering drive to transport and calender the initial film. The second size adjustment component is connected to the upper roller group and is used to drive the upper roller group to move in order to adjust the size of the second calendering gap; The lower calendering assembly includes a lower calendering drive and a lower roller group. A second calendering gap is formed between the lower roller group and the upper roller group. The lower roller group and the lower calendering drive are connected in a driving relationship. The lower roller group can move under the driving action of the lower calendering drive to transport the initial film. The upper roller group and the lower roller group each include multiple rollers. The rollers of the upper roller group and the rollers of the lower roller group are arranged correspondingly to form the rolling structure. The multiple rolling structures are arranged sequentially at intervals along the conveying direction of the initial film.

6. The dry film-forming apparatus according to claim 5, characterized in that, The second size adjustment member is configured to adjust the tilt angle of the upper roller group relative to the lower roller group, so that the second calendering gap has a tapered structure in the conveying direction of the initial film; Along the conveying direction of the initial film, the second size adjustment member includes adjustment units disposed at least at both ends of the upper roller assembly for adjusting the relative positions of the two ends of the upper roller assembly.

7. The dry film-forming apparatus according to claim 5, characterized in that, The diameter of the upper roller group is different from that of the lower roller group.

8. The dry film-forming apparatus according to claim 5, characterized in that, The multi-roller mechanism further includes a gap detection component, which is disposed at the initial end and / or the end of the initial film conveying direction for detecting the size of the second calendering gap.

9. The dry film-forming apparatus according to claim 1, characterized in that, The dry film-forming apparatus further includes a feeding mechanism, which is disposed at the feeding end of the planar calendering mechanism, for receiving and conveying the dry electrode powder to the planar calendering mechanism; The feeding mechanism includes a feeding bin and a feeding roller assembly. The feeding roller assembly is located at the outlet of the feeding bin and is used to transport the dry electrode powder to the planar calendering mechanism.

10. The dry film-forming apparatus according to claim 1, characterized in that, The dry film-forming apparatus further includes: An edge cutting mechanism is provided on the discharge side of the multi-roller pressing mechanism for cutting the edge of the target film. The edge cutting mechanism includes an upper edge cutting roller, a lower edge cutting roller, and an edge collecting groove. The upper edge cutting roller and the lower edge cutting roller are arranged opposite to each other, and the edge collecting groove is located below the lower edge cutting roller for collecting the cut edge material. A film-belt laminating mechanism is disposed on the side of the edge material cutting mechanism away from the multi-roll pressing mechanism. The film-belt laminating mechanism includes an upper laminating clamping roller, a lower laminating clamping roller, and a current collector base belt. The upper laminating clamping roller and the lower laminating clamping roller are disposed opposite to each other. The current collector base belt is sandwiched between the upper laminating clamping roller and the lower laminating clamping roller. The film-belt laminating mechanism is used to laminate the target film onto the current collector.

Images