Manufacturing method and manufacturing device of lithium ion diaphragm
By combining extraction, edge cutting and edge burning steps in the lithium-ion diaphragm manufacturing method, the damage problem of silicon negative electrode volume expansion on the diaphragm is solved, the lateral tensile strength and tensile ratio of the diaphragm are improved, and the stability and reliability of the diaphragm under high tensile conditions are ensured.
Patent Information
- Application Number
- CN202412000299.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-03-28
AI Technical Summary
The volume expansion of the silicon negative electrode during the lithiation process produces local compressive stress on commercial polyethylene membranes, resulting in pore collapse, weakening the transmission capacity of lithium ions on the membrane. It is difficult for the prior art to improve the lateral tensile strength of the membrane while ensuring that the membrane is stretched relatively high.
In the manufacturing method of lithium ion diaphragm, the stretch ratio and lateral tensile strength of the diaphragm are improved by the extraction step, the edge cutting step and the edge burning step. The specific steps include: after extraction, the diaphragm is cut horizontally to reduce the inlet width, and thus increase the stretching ratio; then the edge of the diaphragm after cutting is burned, heated first and then cooled to thicken the edges and improve the tensile strength.
Through this method, the transverse tensile strength of the lithium-ion diaphragm is significantly improved, avoiding the film breakage caused by weak edges during secondary stretching, and ensuring the stability and reliability of the diaphragm under high tensile conditions.
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Figure CN119725986A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of diaphragm production, and in particular relates to a method and a device for manufacturing a lithium ion diaphragm. Background Art
[0002] Lithium-ion batteries are usually mainly composed of positive electrodes, negative electrodes, separators, electrolytes, and battery shells. In the structure of lithium-ion batteries, the separator is one of the key internal components. The main function of the separator is to separate the positive and negative electrodes of the battery to prevent the positive and negative electrodes from directly contacting and short-circuiting, and at the same time to allow electrolyte ions to pass smoothly during the battery charging and discharging process to form current.
[0003] The theoretical specific capacity of silicon anode is as high as 3592 mAh g -1 , superior to the currently popular graphite anode material, and is expected to achieve a leap in battery energy density, electric vehicle range and efficiency, and the capacity of portable electronic devices. The main challenge of silicon as a mainstream anode material is that its volume expansion during lithiation is severe (up to 300%). This expansion and subsequent contraction during attenuation will exert huge mechanical stress on silicon particles, resulting in silicon negative crushing and loss of electrical connectivity.
[0004] An easily overlooked factor in the failure of silicon anode (Si): mechanical closure of the diaphragm. The volume expansion of silicon produces local compressive stress on the commercial polyethylene diaphragm, causing pore collapse. This structural damage weakens the transmission capacity of lithium ions on the diaphragm, exacerbating redox inhomogeneity and silicon powdering. Simulation results show that the diaphragm needs a large Young's modulus to withstand the volume expansion of silicon.
[0005] In order to increase the Young's modulus of the diaphragm, it is necessary to increase the stretching ratio of the diaphragm. After the diaphragm is extracted and before the second stretching, the diaphragm is transversely trimmed to reduce the inlet width. When the outlet remains unchanged, the transverse stretching of the diaphragm is greatly improved. For example, when the diaphragm outlet width is 6000mm, if the inlet width is 4000mm, the stretching ratio (diaphragm outlet width / inlet width) is 1.50 times. If the inlet width is 3200mm through trimming, the stretching ratio is 1.88. The stretching ratio of the trimmed diaphragm after extraction is improved, and the strength and air permeability of the diaphragm are significantly improved.
[0006] After extraction, the paraffin oil in the diaphragm is extracted and the diaphragm becomes thinner. If the edges are not cut after extraction, the 20-60mm area on both sides of the diaphragm will be clamped by the chain clamps of the primary stretching mechanism. After the high temperature in the first stretching mechanism, the diaphragm will be closed. When the diaphragm is stretched in the secondary stretching mechanism, the edge clamped by the chain clamp has thick edge support, which is equivalent to linear force, and the middle of the diaphragm is not easy to break; but in order to increase the stretching ratio of the diaphragm to increase the strength of the diaphragm, the thick edge of the diaphragm edge is usually cut off before entering the secondary horizontal stretching device after extraction, but doing so will make the edge area clamped by the chain clamp thinner when the diaphragm is stretched in the second stretching mechanism, which is equivalent to point force. When the stretching is relatively large, the single point force of the diaphragm may cause a gap due to stretching, and the clamp will be detached, until the film breaks and cannot come out from the outlet of the secondary stretching. Summary of the invention
[0007] In view of this, the present invention provides a method and a device for manufacturing a lithium ion diaphragm, which improve the transverse tensile strength of the diaphragm while ensuring that the diaphragm has a relatively high tensile strength, and the diaphragm is not easily torn after trimming.
[0008] In order to achieve the above object, the present invention adopts the following technical scheme:
[0009] A method for manufacturing a lithium ion diaphragm, comprising an extraction step and a secondary stretching step, the manufacturing method also comprising a trimming step and a hotting step located between the extraction step and the secondary stretching step, the trimming step specifically comprising trimming the edge of the diaphragm after extraction to obtain a trimmed diaphragm, the hotting step specifically comprising first heating the edge of the trimmed diaphragm and then cooling the edge of the trimmed diaphragm.
[0010] In a preferred embodiment, in the ironing step, a heating roller is used to heat the edge of the trimmed diaphragm, and a cooling roller is used to cool the edge of the trimmed diaphragm.
[0011] In a preferred embodiment, in the ironing step, the edge of the trimmed membrane is heated by a heating plate or by infrared heating, and the edge of the trimmed membrane is cooled by a cooling plate.
[0012] In a preferred embodiment, in the ironing step, the heating temperature is 130-150°C, and the cooling temperature is 0-20°C.
[0013] In a preferred embodiment, in the ironing step, the edge of the trimmed diaphragm is heated for 3-5 seconds, and the edge of the trimmed diaphragm is cooled for 1-2 seconds.
[0014] In a preferred embodiment, in the trimming step, the width of the trimmed diaphragm is greater than 0 and less than 500 mm; in the ironing step, the width of the ironed diaphragm is 40-60 mm.
[0015] In a preferred embodiment, the manufacturing method comprises the following steps performed in sequence: a primary stretching step, an extraction step, a trimming step, a curling step, a secondary stretching step, and a winding step.
[0016] The present invention also adopts the following technical solution:
[0017] A manufacturing device for a lithium ion separator, comprising an extraction mechanism and a secondary stretching mechanism, the manufacturing device also comprising:
[0018] A trimming mechanism, which is used to trim the diaphragm to obtain a trimmed diaphragm, and the trimming mechanism is arranged at the rear side of the extraction mechanism;
[0019] The ironing mechanism is used to heat the edge of the trimming membrane. The ironing mechanism is located between the trimming mechanism and the secondary stretching mechanism. The ironing mechanism includes a heating unit arranged at the edge of the trimming membrane.
[0020] In a preferred embodiment, the ironing mechanism further includes a cooling unit arranged at an edge of the membrane, the heating unit and the cooling unit are arranged along a conveying direction of the membrane, and the heating unit and the cooling unit are arranged in parallel.
[0021] In a preferred embodiment, the heating unit has a heating roller, the heating roller has a first fluid channel, and heat transfer oil flows through the first fluid channel; the cooling unit has a cooling roller, the cooling roller has a second fluid channel, and cooling water flows through the second fluid channel.
[0022] The present invention adopts the above solution, which has the following advantages compared with the prior art:
[0023] The manufacturing method of the lithium ion membrane of the present invention performs a trimming treatment on the edge of the membrane before the secondary stretching step in order to increase the stretching ratio of the membrane. The width of the membrane entering the secondary stretching step is reduced to improve the Young's modulus of the membrane. The trimmed membrane is then subjected to an edge ironing treatment. Specifically, the edge of the trimmed membrane is first heated and then cooled. This makes the edge of the membrane thicker and the membrane is not easily torn apart during the secondary stretching. That is, while ensuring that the stretch ratio of the membrane is relatively high, the lateral tensile strength of the membrane is relatively high and it is not easily torn apart during the secondary stretching. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.
[0025] Figure 1 A schematic diagram of a manufacturing method of a lithium ion separator according to an embodiment of the present invention;
[0026] Figure 2 is a schematic diagram of a hot edge mechanism, wherein the edge cutting diaphragm is not shown;
[0027] Figure 3 It is a schematic diagram of the edge ironing mechanism.
[0028] in,
[0029] 1. Trimming diaphragm; 2. Heating roller; 3. Cooling roller. DETAILED DESCRIPTION
[0030] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0031] Reference Figures 1 to 3 As shown, this embodiment provides a method for manufacturing a lithium ion separator, comprising the following steps performed in sequence: a primary stretching step, an extraction step, a trimming step, a hot edge step, a secondary stretching step, and a winding step.
[0032] Furthermore, the trimming step specifically includes trimming the edge of the extracted diaphragm to obtain a trimmed diaphragm, and the ironing step includes first heating the edge of the trimmed diaphragm using a heating unit, and then cooling the edge of the trimmed diaphragm using a cooling unit. The ironing in this embodiment is to first heat the edge of the diaphragm and then cool it, rather than first heating the entire diaphragm and then cooling it. If the entire diaphragm is first heated and then cooled, the entire diaphragm will shrink or thicken, affecting the use effect. The width of the trimming is greater than 0 and less than 500mm, and the width of the ironing is 40-60mm. The larger the width of the trimming, the smaller the inlet width of the diaphragm and the greater the stretching ratio. The "width" here refers to the direction perpendicular to the running direction of the diaphragm.
[0033] Furthermore, in the ironing step, the edge of the trimmed diaphragm 1 is heated by the heating roller 2, and the edge of the trimmed diaphragm 1 is cooled by the cooling roller 3. Figure 2 and Figure 3 As shown, in this embodiment, there are eight heating rollers 2 and two cooling rollers 3. The diaphragm of the trimmed diaphragm 1 has a front edge and a rear edge that are arranged opposite to each other. Four heating rollers 2 and one cooling roller 3 are arranged on the front edge and the rear edge respectively. Both the heating rollers 2 and the cooling rollers 3 are in contact with the edge of the slit diaphragm 1. The temperature at which the heating rollers 2 heat the trimmed diaphragm 1 is 130-150°C, and the temperature at which the cooling rollers 3 cool the trimmed diaphragm 1 is 0-20°C. The edge of the trimmed diaphragm 1 is heated for 3-5 seconds, and the edge of the trimmed diaphragm 1 is cooled for 1-2 seconds. In the specific operation, the edge of the trimmed diaphragm 1 is heated first, and the edge of the trimmed diaphragm 1 shrinks when heated, and the thickness of the edge increases. Then, the edge of the trimmed diaphragm 1 is cooled, so that the edge of the trimmed diaphragm 1 is harder and has a higher tensile strength.
[0034] In the edge ironing step of other embodiments, the edge of the diaphragm may be heated by a heating plate or by infrared heating, and the edge of the diaphragm may be cooled by a cooling plate.
[0035] If the diaphragm is not trimmed, the middle part of the diaphragm is not easy to break in the secondary stretching step, but the stretching ratio is relatively low, and the Young's modulus of the diaphragm is small, which causes the diaphragm to be unable to withstand the volume expansion of silicon. In order to overcome the above defects, the edges of the diaphragm are trimmed to increase the stretching ratio, but after trimming, due to the thin edges, the middle part of the diaphragm is easily cut off during the secondary stretching process. To address the above problems, the present embodiment performs an edge ironing treatment on the trimmed diaphragm. It can be seen from Table 1 that the diaphragm obtained by the manufacturing method of the present embodiment, after actual use, has a transverse tensile strength (TD) and acupuncture strength that are equivalent to or even higher than those without trimming. This shows that the manufacturing method of the present embodiment can not only ensure that the diaphragm has a high stretching ratio, but also will not have the phenomenon of film breakage due to the thin stretching edge during the secondary stretching process, and has high reliability.
[0036] Table 1 Comparison of diaphragms without trimming and trimming after hot edge
[0037]
[0038] The present embodiment also provides a manufacturing device for a lithium-ion diaphragm, including an extraction mechanism and a secondary stretching mechanism, and a trimming mechanism and an ironing mechanism disposed between the extraction mechanism and the secondary stretching mechanism, wherein the trimming mechanism is disposed at the rear side of the extraction mechanism, and the ironing mechanism is located between the trimming mechanism and the secondary stretching mechanism. The trimming mechanism includes a tool holder and a cutter disposed on the tool holder. After extraction, the diaphragm is transported to the bottom of the tool holder via a conveying roller, and the cutter on the tool holder cuts off the edge of the diaphragm, and the cutting range is 0-500mm; the ironing mechanism includes a heating unit and a cooling unit disposed at the edge position of the trimmed diaphragm 1, and the heating unit and the cooling unit are located below the diaphragm 1. The heating unit and the cooling unit are disposed along the diaphragm conveying direction and the heating unit and the cooling unit are disposed parallel to each other. The diaphragm conveying direction here refers to Figure 3 The running direction of the middle diaphragm is the left-right direction. After the diaphragm has its edges cut off at the trimming mechanism, a trimmed diaphragm 1 is obtained, and the trimmed diaphragm 1 is transported to the heating unit and the cooling unit through a plurality of conveying rollers to heat and cool the edges of the trimmed diaphragm 1.
[0039] Furthermore, the heating unit has a heating roller 2, which has a first fluid channel, in which heat transfer oil flows, and the trimming diaphragm 1 is heated by the heat carried by the heating oil, and the temperature of the heating oil is controlled by a mold temperature controller, and the mold temperature controller controls the temperature of the heating oil between 130-150°C; the cooling unit has a cooling roller 3, and the cooling roller 3 has a second fluid channel, in which cooling water flows, and the cooling water is temperature-controlled by circulating water. This is because the trimming diaphragm 1 has a relatively high heat after passing through the heating roller 2, and the temperature of the cooling roller 3 will be increased when passing through the cooling roller 3. Therefore, it is necessary to continuously circulate the liquid in the cooling roller 3 and replace the cooling water so that the temperature in the cooling roller 3 is maintained at 0-20°C.
[0040] The lithium ion diaphragm of this embodiment is trimmed after extraction to obtain a trimmed diaphragm 1, which is conveyed to a plurality of parallel heating rollers 2, which heat the edges of the trimmed diaphragm 1 at a temperature of 130-150°C. The holes on the heated diaphragm are closed, and the diaphragm heat shrinks, causing the diaphragm to thicken. Then, the edges of the heated trimmed diaphragm 1 are cooled by the cooling roller 3. The trimming can reduce the entrance width of the diaphragm entering the secondary stretching mechanism to increase the stretching ratio of the diaphragm, increase the Young's modulus of the diaphragm, and prevent the diaphragm from being unable to withstand the volume expansion of silicon; by first heating and then cooling the edge of the trimmed diaphragm 1, the trimmed diaphragm 1 is prevented from being torn during the secondary stretching process, that is, the method for making the lithium ion diaphragm of this embodiment can not only ensure that the diaphragm has a smaller entrance width to increase the stretching ratio, but also has a higher transverse tensile strength and is not easily torn.
[0041] As shown in this specification and claims, the terms "comprises" and "include" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list, and the method or device may also include other steps or elements. The term "and / or" as used herein includes any combination of one or more of the relevant listed items.
[0042] It should be noted that, unless otherwise specified, when a feature is referred to as being "fixed" or "connected" to another feature, it may be directly fixed or connected to the other feature, or it may be indirectly fixed or connected to the other feature. In addition, the descriptions of up, down, left, right, etc. used in the present invention are only relative to the relative positional relationship of the components of the present invention in the drawings.
[0043] The above embodiment is only for illustrating the technical concept and features of the present invention, and is a preferred embodiment. Its purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for manufacturing a lithium ion separator, comprising an extraction step and a secondary stretching step, characterized in that: The manufacturing method also includes a trimming step and a hotting step located between the extraction step and the secondary stretching step. The trimming step specifically includes trimming the edge of the extracted diaphragm to obtain a trimmed diaphragm. The hotting step specifically includes first heating the edge of the trimmed diaphragm and then cooling the edge of the trimmed diaphragm.
2. The manufacturing method according to claim 1, characterized in that: In the ironing step, a heating roller is used to heat the edge of the trimmed diaphragm, and a cooling roller is used to cool the edge of the trimmed diaphragm.
3. The manufacturing method according to claim 1, characterized in that: In the edge ironing step, the edge of the trimmed diaphragm is heated by a heating plate or by infrared heating, and the edge of the trimmed diaphragm is cooled by a cooling plate.
4. The manufacturing method according to claim 1, characterized in that: In the ironing step, the heating temperature is 130-150°C and the cooling temperature is 0-20°C.
5. The manufacturing method according to claim 4, characterized in that: In the ironing step, the edge of the trimmed membrane is heated for 3-5 seconds, and the edge of the trimmed membrane is cooled for 1-2 seconds.
6. The manufacturing method according to claim 1, characterized in that: In the trimming step, the width of the trimmed diaphragm is greater than 0 and less than 500 mm; in the ironing step, the width of the ironed diaphragm is 40-60 mm.
7. The manufacturing method according to claim 1, characterized in that: The manufacturing method comprises the following steps which are performed in sequence: a primary stretching step, an extraction step, an edge cutting step, an edge ironing step, a secondary stretching step, and a winding step.
8. A manufacturing device used in the manufacturing method according to any one of claims 1 to 7, comprising an extraction mechanism and a secondary stretching mechanism, characterized in that: The manufacturing device also includes: A trimming mechanism, which is used to trim the diaphragm to obtain a trimmed diaphragm, and the trimming mechanism is arranged at the rear side of the extraction mechanism; The ironing mechanism is used to heat the edge of the trimming membrane. The ironing mechanism is located between the trimming mechanism and the secondary stretching mechanism. The ironing mechanism includes a heating unit arranged at the edge of the trimming membrane.
9. The manufacturing device according to claim 8, characterized in that: The ironing mechanism further comprises a cooling unit arranged at the edge of the trimming membrane, the heating unit and the cooling unit are arranged along the membrane conveying direction and the heating unit and the cooling unit are arranged in parallel.
10. The manufacturing device according to claim 9, characterized in that: The heating unit comprises a heating roller, the heating roller comprises a first fluid channel, and heat transfer oil flows through the first fluid channel; the cooling unit comprises a cooling roller, the cooling roller comprises a second fluid channel, and cooling water flows through the second fluid channel.