A dry film forming roller set and a dry film forming apparatus

Abstract

The application relates to the technical field of power batteries, in particular to a dry film forming roller set and a dry film forming device. The roller set comprises a forming constraint mechanism, a plurality of extrusion rollers, at least a first extrusion roller, a second extrusion roller and a third extrusion roller arranged in sequence along a film forming direction, the forming constraint mechanism is arranged at the bottom of the second extrusion roller, the top surface of the forming constraint mechanism surrounds the bottom of the second extrusion roller, and the two ends of the forming constraint mechanism respectively abut against the first extrusion roller and the third extrusion roller; the end surface of the forming constraint mechanism facing the second extrusion roller, the roller surface of the second extrusion roller and the roller gap between the first extrusion roller and the second extrusion roller form a film forming channel to extrude powder. The dry film forming roller set restrains the film forming path of the powder through the forming constraint mechanism, increases the compaction stroke and makes the extension of the powder in the axial and longitudinal directions be restrained during the film forming process, increases the compaction degree of the particles in the powder, and ensures continuous film forming under the condition of low binder content.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of power batteries, in particular to a dry film forming roller set and a dry film forming device. BACKGROUND

[0002] The forming process of electrode sheets and electrolyte films of solid-state lithium ion batteries mainly includes two technical routes, namely, a wet forming process and a dry forming process. The wet forming process is similar to the manufacturing process of traditional liquid-state lithium ion batteries, and the process principle is to prepare active material powder into slurry through a solvent and a binder, and then remove the liquid components through coating, drying and other processes to finally form electrode sheets and electrolyte film sheets. In comparison, the dry forming process does not need to use a solvent, but directly mixes the binder and the powder material, and then presses the mixture into a film through a roller pressing device. At present, the dry process has formed a mature technical solution in the field of capacitor film sheet preparation, and has also been applied to a certain extent in the field of traditional liquid-state lithium ion batteries.

[0003] In the dry forming process, polytetrafluoroethylene (PTFE) is mainly used as the binder. In the dry film forming process of traditional liquid-state lithium ion batteries, the typical addition amount of PTFE is 1%-5%, and continuous production can be realized through a multi-roller roller pressing machine. However, in the solid-state battery system, due to the lack of electrolyte participating in lithium ion conduction, the binder content has a significant influence on the charge and discharge capacity and rate performance of the battery. Experimental data show that the addition amount of PTFE in the dry film forming process of solid-state batteries needs to be strictly controlled in the range of 0.2%-0.5%, and for some specific electrode formulations, it is even required to reduce the PTFE content to below 0.1%. However, the existing traditional roller pressing equipment generally has technical bottlenecks such as film sheet cracking and difficulty in realizing continuous film forming when processing such ultra-low binder content powder materials.

[0004] In view of the above technical problems, it is urgent to develop a new type of dry film forming equipment to realize stable and continuous production under the condition of low binder content. SUMMARY

[0005] Therefore, in order to overcome the defects of the prior art, the application provides a dry film forming roller set and a dry film forming device, which effectively solve the problem that the existing film forming machine is difficult to form a film due to cracking during the film forming process.

[0006] According to a first aspect of the present application, a dry film forming roller set is provided, comprising a plurality of extrusion rollers arranged in sequence along a film forming direction, wherein the dry film forming roller set further comprises a forming constraint mechanism, and the plurality of extrusion rollers at least comprises a first extrusion roller, a second extrusion roller and a third extrusion roller arranged in sequence along the film forming direction, the forming constraint mechanism is arranged at the bottom of the second extrusion roller, the top surface of the forming constraint mechanism surrounds the bottom of the second extrusion roller, and the two ends of the forming constraint mechanism respectively abut against the first extrusion roller and the third extrusion roller; the end surface of the forming constraint mechanism facing the second extrusion roller, the roller surface of the second extrusion roller and the roller gap between the first extrusion roller and the second extrusion roller form a film forming channel to extrude powder.

[0007] Preferably, the roller gap between the first extrusion roller and the second extrusion roller is a first roller gap, the roller gap between the second extrusion roller and the third extrusion roller is a second roller gap, the first end of the forming constraint mechanism is located in the first roller gap and is tangent to the first extrusion roller, and the second end of the forming constraint mechanism is located in the second roller gap and is tangent to the third extrusion roller.

[0008] Preferably, the forming constraint mechanism comprises a main body, and the end surface of the main body facing the second extrusion roller is formed as an arc surface, so that the film forming channel is formed as an arc-shaped channel.

[0009] Preferably, the curvature of the arc surface gradually increases so that the film forming channel gradually decreases.

[0010] Preferably, the forming constraint mechanism further comprises an end plate arranged at the two ends of the main body in the axial direction of the second extrusion roller to block the ends of the film forming channel in the axial direction of the second extrusion roller.

[0011] Preferably, the end plate is detachably arranged on the main body.

[0012] Preferably, the inside of the main body is provided with a heating mechanism.

[0013] Preferably, the roller gaps between the plurality of extrusion rollers arranged in sequence along the film forming direction gradually decrease.

[0014] According to a second aspect of the present application, a dry film forming device is provided, wherein the dry film forming device comprises the dry film forming roller set as described above.

[0015] Preferably, the dry film forming device comprises a rack, a feeding mechanism and a winding mechanism, and the feeding mechanism, the dry film forming roller set and the winding mechanism are arranged in sequence along a film forming direction on the rack.

[0016] The dry film forming roller set according to the present application restrains the powder film forming path through the forming restraint mechanism, increases the compaction stroke and restrains the extension of the powder film forming process in the axial and longitudinal directions, further increases the compaction degree of the internal particles of the powder, and ensures continuous film forming under the condition of extremely low binder content. Compared with the traditional roller pressing film forming mode, the existence of the film forming channel makes the powder pushed into the film forming channel by the extrusion force after being extruded by the first extrusion roller and the second extrusion roller to continue to receive the extrusion and shearing action of the roller surface of the second extrusion roller and the surface of the film forming channel, so that the film forming ability of the powder with less glue content is improved, and the production quality of the formed film is improved.

[0017] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are specifically described below, and the accompanying drawings are described in detail as follows. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0019] Figure 1 The structure schematic diagram of the dry film forming roller set according to the embodiment of the present application is shown;

[0020] Figure 2 The partial structure schematic diagram of the dry film forming roller set according to the embodiment of the present application is shown;

[0021] Figure 3 The cross-sectional view of the dry film forming roller set according to the embodiment of the present application is shown;

[0022] Figure 4 The structure schematic diagram of the dry film forming device according to the embodiment of the present application is shown;

[0023] Figure 5 The side view of the dry film forming device according to the embodiment of the present application is shown.

[0024] Reference signs: 1-first extrusion roller; 2-second extrusion roller; 3-third extrusion roller; 4-film forming channel; 701-main body; 702-end plate; 703-quick release part; 8-feeding mechanism; 9-machine frame; 11-winding mechanism; 12-powder. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application and are not all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0026] In the description of the embodiments of the present application, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0027] In addition, the terms "horizontal", "vertical" and the like do not mean that the components must be absolutely horizontal or vertical, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0028] In the description of the embodiments of the present application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "arrangement", "installation", "communication", "connection" should be understood broadly, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be mechanically connected, can be electrically connected; can be directly connected, can be indirectly connected through an intermediate medium, and can be internal communication of two elements. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0029] According to a first aspect of the present application, a dry film forming roller set is provided, such as Figures 1 to 3As shown, the dry film forming roller set is used for dry forming of solid lithium ion batteries. Dry forming requires that the powder 12 filled in the roller gap between two adjacent rollers is extruded by the dry roller pressing film forming equipment. When the powder 12 is extruded to the narrowest part of the roller gap, it will be subjected to the greatest extrusion force, which will cause the distance between the particles in the powder 12 to decrease, so that the binder will contact and bond to form a continuous film. Since the powder 12 will be elongated in the axial and radial directions of the extrusion roller while being extruded and thinned, and the existing dry roller pressing film forming equipment cannot constrain the axial and radial elongation of the powder 12, when the axial and longitudinal extension of the powder 12 exceeds the bonding strength of the binder in the powder 12, film cracking, belt breaking and other phenomena will occur, which will result in the failure of continuous film forming. This phenomenon is particularly obvious when the binder content in the powder 12 is very low (for example, <0.5%). Based on this, the first aspect of the present application provides a dry film forming roller set that uses a forming constraint mechanism to constrain the axial and longitudinal elongation of the powder 12 to ensure the film forming quality.

[0030] In the following description, reference will be made to Figures 1 to 3 The detailed structure of the forming constraint mechanism of the dry film forming roller set will be described in detail.

[0031] As Figures 1 to 3 shown, in an embodiment, the dry film forming roller set includes a plurality of extrusion rollers arranged in sequence along the film forming direction. The film forming direction can be understood as the direction from left to right of Figure 2 and Figure 3 . The powder 12 is gradually extruded and thinned through the roller gap between the plurality of extrusion rollers to achieve film forming. The plurality of extrusion rollers at least includes a first extrusion roller 1, a second extrusion roller 2 and a third extrusion roller 3 arranged in sequence along the film forming direction. The powder 12 is formed through the roller gap between the first extrusion roller 1 and the second extrusion roller 2, and then thinned through the roller gap between the second extrusion roller 2 and the third extrusion roller 3.

[0032] A forming constraint mechanism is located at the bottom of the second extrusion roller 2. The top surface of the forming constraint mechanism surrounds the bottom of the second extrusion roller 2, and the two ends of the forming constraint mechanism abut against the first extrusion roller 1 and the third extrusion roller 3, respectively. This constrains the roll gaps between the first extrusion roller 1 and the second extrusion roller 2, and between the second extrusion roller 2 and the third extrusion roller 3, preventing the powder 12 from elongating axially and radially on the extrusion rollers. The end face of the forming constraint mechanism facing the second extrusion roller 2, the roller surface of the second extrusion roller 2, and the roll gap between the first and second extrusion rollers form a film-forming channel 4 to extrude the powder 12. The powder 12 forms a film within the film-forming channel 4. The forming constraint mechanism constrains the film-forming path of the powder 12, greatly increasing the compaction stroke and restricting the axial and longitudinal elongation of the powder 12 during film formation. This further increases the compaction of the particles inside the powder 12, ensuring continuous film formation with minimal binder content. Compared to the traditional roll forming method, the presence of the film forming channel 4 allows the powder 12 to be pushed into the film forming channel 4 by the extrusion force after being extruded by the first extrusion roller 1 and the second extrusion roller 2. It continues to be subjected to the extrusion and shearing action of the roller surface of the second extrusion roller 2 and the surface of the film forming channel 4, thereby improving the film forming ability of the powder 12 with a low adhesive content and improving the production quality of the formed film.

[0033] Preferably, such as Figures 1 to 3 As shown, in this embodiment, the gap between the first extrusion roller 1 and the second extrusion roller 2 is the first gap, and the gap between the second extrusion roller 2 and the third extrusion roller 3 is the second gap. The first end of the forming constraint mechanism is located at the first gap and is tangent to the first extrusion roller 1. The first end of the forming constraint mechanism can be formed as a smooth transition surface and can cooperate with the roller surface of the first extrusion roller 1. At the same time, the first end of the forming constraint mechanism (the end closer to the first extrusion roller 1) is tangent to the roller surface of the first extrusion roller 1 at the first gap, preventing the powder 12 from being stuck to the roller surface of the first extrusion roller 1 after being compacted through the first gap, and ensuring that the compacted powder 12 can all follow the roller surface of the second extrusion roller 2 into the arc-shaped film-forming channel 4.

[0034] Furthermore, the second end of the forming constraint mechanism is located at the second roll gap and is tangent to the third extrusion roll 3. The second end of the forming constraint mechanism (the end closer to the third extrusion roll 3) can be formed as a smooth transition surface and can cooperate with the roll surface of the third extrusion roll 3. At the same time, the second end of the forming constraint mechanism is tangent to the roll surface of the third extrusion roll 3 at the second roll gap, so as to guide the powder 12 after film formation into the second roll gap from below for extrusion and transfer the powder 12 to the roll surface of the third extrusion roll 3. Afterwards, it can be extruded and thinned by multiple subsequent extrusion rolls in sequence before being wound up.

[0035] Preferably, such as Figures 1 to 3As shown, in the embodiment, the forming constraint mechanism can further include a main body 701, an end face of the main body 701 facing the second extrusion roller 2 is formed as an arc surface, so that the film forming channel 4 is formed as an arc channel.

[0036] Preferably, as Figures 1 to 3 As shown, in the embodiment, the curvature of the arc surface gradually increases so that the film forming channel 4 gradually decreases, in combination with the second roller surface, forming a cavity structure gradually decreasing from left to right in Figure 2 and Figure 3 The cavity structure gradually decreasing from left to right in the embodiment further plays a role of gradually thinning extrusion on the powder 12 with less content of glue, thereby further increasing the contact and adhesion between the binders in the powder 12 and strengthening the film forming capability.

[0037] Preferably, as Figures 1 to 3 As shown, in the embodiment, the forming constraint mechanism further includes end plates 702, the end plates 702 are arranged at both ends of the main body 701 in the axial direction of the second extrusion roller 2, so as to block the ends of the film forming channel 4 in the axial direction of the second extrusion roller 2, so that the film forming channel 4 is formed as a completely closed channel, thereby constraining the elongation of the powder 12 in the axial and longitudinal directions.

[0038] Preferably, as Figures 1 to 3 As shown, in the embodiment, the end plates 702 are detachably arranged on the main body 701. The two end plates 702 can be designed as quick-release plate body structures through quick-release members 703, facilitating disassembly, cleaning and maintenance. The quick-release plate body structure can be formed as a quick-release door structure, the quick-release member 703 can be a combination of a hinge shaft and a fixed buckle, or the quick-release member 703 can be, for example, a connecting bolt, which is disassembled through threaded connection.

[0039] Preferably, as Figures 1 to 3 As shown, in the embodiment, the height of the end plate 702 in the vertical direction (up and down direction) Figure 2 is higher than that of the main body 701, thereby realizing the blocking of the film forming channel 4 by the end plate 702.

[0040] Preferably, as Figures 1 to 3As shown, in the embodiment, the interior of the main body 701 is provided with a heating mechanism (not shown). Since the film 12 generally needs to be heated, the heating mechanism such as an electric heating wire or a liquid oil circuit can be provided in the interior of the extrusion roller to heat the film forming channel 4 during film forming. Since the main body 701 surrounds the roller surface of the second extrusion roller 2, installing the heating mechanism in the main body 701 can achieve more uniform heating of the film forming channel 4, and has a more uniform heating effect than the traditional roller pressing mechanism, which is more conducive to film forming. In addition, the heating mechanism can cooperate with the original heating system in the extrusion roller to simultaneously heat the upper and lower surfaces of the film during film forming, improve the heating efficiency and uniformity, and facilitate the bonding of the binder in the powder 12.

[0041] Preferably, as Figures 1 to 3 As shown, in the embodiment, the roll gap between the plurality of extrusion rollers arranged in sequence in the film forming direction gradually decreases, so that the thickness of the formed film gradually thins and is wound by the winding mechanism 11.

[0042] The working process of the dry film forming roller group is as follows: the powder 12 enters from the feeding mechanism 8, enters the first roll gap through the conveying belt mechanism, and is further extruded and sheared by the roller surface of the second extrusion roller 2 and the channel surface of the film forming channel 4 to ensure continuous film forming without cracking. After the thick film is further thinned by the second roll gap and the third roll gap, it is wound into a coiled material.

[0043] The dry film forming roller group constrains the powder film forming path through the forming constraint mechanism, increases the compaction stroke, and constrains the extension of the powder film forming process in the axial and longitudinal directions, further increases the compaction degree of the particles inside the powder, and ensures continuous film forming under the condition of extremely low binder content. Compared with the traditional roller pressing film forming method, the existence of the film forming channel makes the powder pushed into the film forming channel by the extrusion force after being extruded by the first extrusion roller and the second extrusion roller to continue to be extruded and sheared by the roller surface of the second extrusion roller and the surface of the film forming channel, so that the film forming ability of the powder with less glue content is improved, and the production quality of the formed film is improved.

[0044] In addition, as Figure 4 and Figure 5As shown, according to the second aspect of the present application, a dry film forming device is provided, which comprises the dry film forming roller set as described above. The dry film forming device further comprises a rack 9, a feeding mechanism 8 and a winding mechanism 11, the feeding mechanism 8, the dry film forming roller set and the winding mechanism 11 are sequentially arranged along the film forming direction on the rack 9. The rack 9 is used to support and fix each mechanism, and the feeding mechanism 8 feeds the powder 12, which can be a mechanism in the prior art, for example, a quantitative feeding system or a simple continuous feeding system. In addition to the forming constraint mechanism described above, the dry film forming roller set can further comprise a roller shaft, a bearing sealing system, a heating system, a motor drive control system and the like. Precise feedback type adjustment of parameters such as roller pressure, gap, temperature and speed can be realized to extrude the powder 12 into a film. In the embodiment, a four-roller type is adopted, i.e., three processing roller gaps are provided, and a controllable heating system is arranged in the roller body to adjust the temperature of the roller, so as to realize simultaneous heating of the upper and lower surfaces of the film during the film forming process, improve the heating efficiency and uniformity, and facilitate the bonding of the binder in the powder 12 into a film. The first roller gap performs film forming processing, and the last two roller gaps thin the rough film to the required thickness. In actual application, the number of film forming rollers and thinning rollers can be increased according to requirements to further increase the number of film forming and thinning roller gaps. The winding mechanism 11 can also use the components in the prior art, for example, a winding drum is used, and a tension adjusting mechanism, a roller adjusting mechanism and the like are arranged to wind the film material after film forming.

[0045] In addition, the dry film forming device can further comprise a film thickness measurement feedback linkage system and a cutting and shaping system. The film thickness measurement feedback linkage system can measure the film thickness online before winding, and simultaneously feedback to the roller gap adjusting system for closed loop feedback adjustment, so as to ensure accurate realization of the target film thickness. The cutting and shaping system can cut the edges of the film material before winding or during roller pressing, so as to ensure the size and edge of the film material to be neat and the thickness to be consistent.

[0046] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present application, which are used to illustrate the technical solutions of the present application, but not to limit the same. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that any person skilled in the art can make modifications or easily think of changes to the technical solutions recorded in the foregoing embodiments within the technical scope disclosed by the present application, or make equivalent replacements to some technical features; and these modifications, changes or replacements do not cause the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A dry film-forming roller assembly, comprising a plurality of extrusion rollers arranged sequentially along the film forming direction, characterized in that, The dry film-forming roller assembly further includes a forming constraint mechanism. The plurality of extrusion rollers include at least a first extrusion roller, a second extrusion roller, and a third extrusion roller arranged sequentially along the film forming direction. The forming constraint mechanism is disposed at the bottom of the second extrusion roller, the top surface of the forming constraint mechanism surrounds the bottom of the second extrusion roller, and the two ends of the forming constraint mechanism abut against the first extrusion roller and the third extrusion roller, respectively. The gap between the end face of the forming constraint mechanism facing the second extrusion roller and the roller surface of the second extrusion roller, and the roller gap between the first extrusion roller and the second extrusion roller, form a film-forming channel to extrude powder. The forming constraint mechanism includes a main body, the end face of the main body facing the second extrusion roller is formed as an arc surface, so that the film forming channel is formed as an arc-shaped channel; The forming constraint mechanism further includes end plates, which are disposed at both ends of the body in the axial direction of the second extrusion roller to block the ends of the film forming channel in the axial direction of the second extrusion roller.

2. The dry film-forming roller assembly according to claim 1, characterized in that, The roll gap between the first extrusion roller and the second extrusion roller is the first roll gap, and the roll gap between the second extrusion roller and the third extrusion roller is the second roll gap. The first end of the forming constraint mechanism is located in the first roll gap and is tangent to the first extrusion roller, and the second end of the forming constraint mechanism is located in the second roll gap and is tangent to the third extrusion roller.

3. The dry film-forming roller assembly according to claim 1, characterized in that, The curvature of the arc surface gradually increases so that the film-forming channels gradually decrease.

4. The dry film-forming roller assembly according to claim 1, characterized in that, The end plate is detachably mounted on the main body.

5. The dry film-forming roller assembly according to claim 1, characterized in that, The main body is equipped with a heating mechanism inside.

6. The dry film-forming roller assembly according to claim 1, characterized in that, The gap between the multiple extrusion rollers arranged sequentially along the film forming direction gradually decreases.

7. A dry film-forming apparatus, characterized in that, The dry film forming apparatus includes the dry film forming roller assembly according to any one of claims 1 to 6.

8. The dry film-forming apparatus according to claim 7, characterized in that, The dry film forming apparatus includes a frame, a feeding mechanism, and a winding mechanism. The feeding mechanism, the dry film forming roller group, and the winding mechanism are arranged sequentially on the frame along the film forming direction.

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