A separator, a wound battery cell, and a secondary battery
By staggering the ceramic layer group at the corner of the separator, the problem of electrolyte extrusion at the corner of the lithium-ion battery is solved, improving the battery's lifespan and safety performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHEJIANG LIWINON ENERGY TECHNOLOGY CO LTD
- Filing Date
- 2025-06-06
- Publication Date
- 2026-07-14
AI Technical Summary
During the cyclic charging and discharging process of lithium-ion batteries, the distance between the electrodes at the corners is compressed, causing the electrolyte to be squeezed out and lithium plating to occur, which affects the battery performance and lifespan.
First and second ceramic layers are disposed at predetermined corners of the separator and are staggered to form gaps, thereby increasing the electrolyte storage space and reducing the risk of lithium plating.
By staggering the ceramic layer group, electrolyte wetting is improved, battery life is extended, physical punctures are reduced, and Hi-pot defect rate and K-value defect rate are improved.
Smart Images
Figure CN224502234U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of battery technology, specifically to a separator, a wound cell, and a secondary battery. Background Technology
[0002] Currently, most lithium-ion batteries employ a wound structure. During cyclic charging and discharging, the positive and negative electrodes of a lithium-ion battery continuously expand and contract. The distance between the electrodes at the corners is compressed, causing the electrolyte to be continuously squeezed out. This can easily lead to insufficient electrolyte and wetting at the corner electrodes, resulting in lithium plating. Lithium plating degrades battery performance and significantly shortens cycle life. Utility Model Content
[0003] The purpose of this application is to overcome the shortcomings of the existing technology and provide a separator, a wound cell, and a secondary battery. The separator includes a first safety coating, a base film, and a second safety coating arranged sequentially. A first ceramic layer group is provided on the side of the first safety coating located at the predetermined corner that is away from the base film. A second ceramic layer group is provided on the side of the second safety coating located at the predetermined corner that is away from the base film. The first ceramic layer group and the second ceramic layer group are staggered in the length direction of the separator, which can form a gap (height difference) in the corner area of the wound cell, provide space to store electrolyte, increase electrolyte wetting, reduce the impact of lithium plating on the corner of the wound cell, and extend the battery life.
[0004] To achieve the above objectives, in a first aspect of this application, a separation membrane is provided, comprising a first safety coating, a base film, and a second safety coating disposed sequentially. The separation membrane includes a predetermined flat portion and a predetermined corner portion arranged alternately. The first safety coating located at the predetermined corner portion has a first ceramic layer group disposed on the side facing away from the base film. The first ceramic layer group includes at least two first ceramic layers arranged at intervals along the length direction of the separation membrane. The second safety coating located at the predetermined corner portion has a second ceramic layer group disposed on the side facing away from the base film. The second ceramic layer group has at least two second ceramic layers arranged at intervals along the length direction of the separation membrane. The first ceramic layer group and the second ceramic layer group are staggered in the length direction of the separation membrane.
[0005] In one embodiment of this application, the misalignment distance S1 is 0.5 to 2 mm.
[0006] In the same predetermined corner, the dimensions of the first ceramic layer and the second ceramic layer in the length direction of the isolation membrane are both W, and the spacing between any two adjacent first ceramic layers and the spacing between any two adjacent second ceramic layers are both S2; the isolation membrane satisfies: 0.2mm≤W-S1≤0.5mm, and / or, 0≤S1-S2≤0.5mm.
[0007] As an embodiment of this application, the ratio between the thickness of the first ceramic layer and the thickness of the second ceramic layer is (1~1.2):1.
[0008] As an embodiment of this application, the thickness of the first ceramic layer is 0.5 to 50 μm, and the thickness of the second ceramic layer is 0.5 to 50 μm.
[0009] As an embodiment of this application, in the length direction of the isolation membrane, the ratio between the size of the first ceramic layer group and the size of its corner portion is (0.5~0.8):1;
[0010] And / or, the ratio between the size of the second ceramic layer and the size of the corner portion is (0.5 to 0.8):1.
[0011] As an embodiment of this application, the thickness of the first safety coating is 0.5 to 10 μm, and the thickness of the second safety coating is 0.5 to 10 μm.
[0012] In a second aspect of this application, a wound battery cell is provided, comprising a negative electrode, a positive electrode, and a separator as described in the first aspect. The separator is disposed between the positive electrode and the negative electrode. The negative electrode, the separator, and the positive electrode are sequentially stacked and wound to form a wound structure. The wound structure includes a flat area and a corner area. The corner area connects to an adjacent flat area. A predetermined flat portion is located in the flat area, and a predetermined corner portion is located in the corner area.
[0013] As an embodiment of this application, the first ceramic layer group is located between the adjacent first safety coating and the positive electrode sheet, and the second ceramic layer group is located between the adjacent second safety coating and the negative electrode sheet.
[0014] In a third aspect of this application, a secondary battery is provided, comprising a wound cell as described in the first aspect. Attached Figure Description
[0015] Figure 1 A schematic diagram of the cross-sectional structure of the isolation membrane provided in this application;
[0016] Figure 2 This is a partial schematic diagram of the wound battery cell provided in this application.
[0017] In the figure, 1 is the separator, 11 is the base film, 12 is the first safety coating, 13 is the second safety coating, 14 is the first ceramic layer, 15 is the second ceramic layer, 2 is the negative electrode, and 3 is the positive electrode. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0019] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.
[0020] In this application, the use of "first" and "second" is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.
[0021] In this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.
[0022] In this application, the terms "an embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this application, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0023] Please see Figures 1-2This application provides an isolation membrane 1, including a first safety coating 12, a base film 11, and a second safety coating 13 arranged sequentially. The isolation membrane 1 includes a predetermined flat portion and a predetermined corner portion arranged alternately. The first safety coating 12 located at the predetermined corner portion has a first ceramic layer group on the side facing away from the base film 11. The first ceramic layer group includes at least two first ceramic layers 14 arranged at intervals along the length direction of the isolation membrane 1. The second safety coating 13 located at the predetermined corner portion has a second ceramic layer group on the side facing away from the base film 11. The second ceramic layer group includes at least two second ceramic layers 15 arranged at intervals along the length direction of the isolation membrane 1. The first ceramic layer group and the second ceramic layer group are staggered in the length direction of the isolation membrane 1.
[0024] This application arranges the first ceramic layer group and the second ceramic layer group in a staggered manner along the length of the separator 1. This not only creates a gap (height difference) in the corner area of the wound cell, providing space to store electrolyte, increasing electrolyte wetting, reducing the impact of lithium plating on the corner of the wound cell, and extending battery life, but also improves the thickness consistency of the separator 1 in the wound cell, reduces physical punctures, and has a certain improvement effect on physical K-value defects and Hi-pot defects.
[0025] In this application, the length direction of the separator 1 is... Figures 1-2 The direction L in the middle.
[0026] In one embodiment, the misalignment distance S1 is 0.5 to 2 mm. For example, S1 can be 0.5 mm, 0.7 mm, 1 mm, 1.2 mm, 1.4 mm, 1.5 mm, 1.8 mm, 2 mm, or a range of any two values therein.
[0027] Specifically, in the same predetermined corner, the dimensions of the first ceramic layer 14 and the second ceramic layer 15 in the length direction of the isolation membrane 1 are both W, and the spacing between any two adjacent first ceramic layers 14 and the spacing between any two adjacent second ceramic layers 15 are both S2; the isolation membrane satisfies: 0.2mm≤W-S1≤0.5mm, and / or, 0≤S1-S2≤0.5mm.
[0028] For example, W-S1 can be a range of 0.2mm, 0.3mm, 0.4mm, 0.5mm or any two of these values; S1-S2 can be a range of 0mm, 1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm or any two of these values.
[0029] When 0.2mm≤W-S1≤0.5mm and 0≤S1-S2≤0.5mm, the gap distribution of the separator 1 in the corner area of the wound cell is more uniform.
[0030] Specifically, W can be 0.7 to 2.5 mm. For example, W can be 0.7 mm, 1 mm, 1.2 mm, 1.4 mm, 1.5 mm, 1.8 mm, 2 mm, 2.5 mm, or any range of two of these values.
[0031] Specifically, S2 can be 0.5 to 1.5 mm. For example, S2 can be 0.5 mm, 0.7 mm, 0.9 mm, 1 mm, 1.2 mm, 1.4 mm, 1.5 mm, or any range of two values therein.
[0032] In one embodiment, along the length of the separator 1, the ratio between the size of the first ceramic layer group and the size of the corner portion is (0.5 to 0.8):1, and the ratio between the size of the second ceramic layer group and the size of the corner portion is (0.5 to 0.8):1. Under this ratio, while ensuring the flatness of the wound cell, the gap of the separator in the corner area of the wound cell can be optimized, ensuring that the lithium plating in the corner area is uniformly improved.
[0033] In one embodiment, the ratio between the thickness of the first ceramic layer 14 and the thickness of the second ceramic layer 15 is (1 to 1.2):1.
[0034] In one embodiment, the thickness h1 of the first ceramic layer 14 is 0.5 to 50 μm.
[0035] In one embodiment, the thickness h2 of the second ceramic layer 15 is 0.5 to 50 μm.
[0036] This application controls the thickness of the first ceramic layer 14 and the thickness of the second ceramic layer 15 within the range of 0.5 to 50 μm. This not only ensures that the gap of the separator 1 in the corner area of the wound cell is moderate, thus guaranteeing the energy density of the battery while avoiding excessive gaps that would reduce the energy density of the battery, but also improves the thickness consistency of the separator 1 in the wound cell, reduces physical punctures, and has a certain improvement effect on physical K-value defects and Hi-pot defects.
[0037] In one embodiment, the thickness H1 of the first safety coating 12 is 0.5 to 10 μm.
[0038] In one embodiment, the thickness H2 of the second safety coating 13 is 0.5 to 10 μm.
[0039] In this application, the provision of the first safety coating 12 and the second safety coating 13 can improve the safety performance of the diaphragm 1 and play a role in preventing puncture.
[0040] This application controls the thickness of the first safety coating 12 and the thickness of the second safety coating 13 to be within the range of 0.5 to 10 μm, which can reduce the defect rate of the separator in the Hi-pot test while ensuring the energy density of the battery.
[0041] In one embodiment, the materials of the first safety coating 12 and the second safety coating 13 each independently include inorganic particles and a binder. The materials of the first safety coating 12 and the second safety coating 13 may also independently include at least one of polymer nanoparticles and nanofibers. The mass percentage of inorganic particles in the first safety coating 12 and the second safety coating 13 are each independently 70-90%, and the mass percentage of the binder in the first safety coating 12 and the second safety coating 13 are each independently 3-10%.
[0042] In one embodiment, the first ceramic layer 14 is made of inorganic particles and a binder, and the second ceramic layer 15 also comprises inorganic particles and a binder. The mass percentage of inorganic particles in the first ceramic layer 14 and the second ceramic layer 15 are each independently 95-99.5%; the mass percentage of inorganic particles in the first ceramic layer 14 and the second ceramic layer 15 are each independently 0.5-5%.
[0043] In this application, the inorganic particles may include at least one of alumina, silicon dioxide, zirconium oxide, titanium dioxide, and boehmite. The binder may include at least one of polyvinylidene fluoride, polyvinylidene fluoride, styrene-butadiene rubber, polyacrylate, and sodium carboxymethyl cellulose. The polymer nanoparticles may be at least one of butyl methacrylate-acrylonitrile-styrene copolymer, butyl methacrylate-ethylene oxide-styrene copolymer, and butyl methacrylate-acrylic acid-styrene copolymer.
[0044] In a second aspect of this application, a wound battery cell is provided, comprising a negative electrode 3, a positive electrode 2, and a separator 1 as described in the first aspect. The separator 1 is disposed between the positive electrode 2 and the negative electrode 3. The negative electrode 3, the separator 1, and the positive electrode 2 are sequentially stacked and wound to form a wound structure. The wound structure includes a flat area and a corner area. The corner area connects to an adjacent flat area. A predetermined flat portion is located in the flat area, and a predetermined corner portion is located in the corner area.
[0045] In one embodiment, the first ceramic layer group is located between the adjacent first safety coating 12 and the positive electrode 2, and the second ceramic layer group is located between the adjacent second safety coating 13 and the negative electrode 3.
[0046] In a third aspect of this application, a secondary battery is provided, comprising a wound cell as described in the first aspect.
[0047] The inventors conducted extensive research experiments during the research process, including designing and fabricating different separators and secondary batteries, and testing battery performance. Some experimental examples and test results are listed below to illustrate this application:
[0048] Example 1
[0049] Please see Figures 1-2 A secondary battery includes a wound cell, comprising a negative electrode 3, a positive electrode 2, and a separator 1. The separator 1 is disposed between the positive electrode 2 and the negative electrode 3. The negative electrode 3, the separator 1, and the positive electrode 2 are sequentially stacked and wound to form a wound structure. The wound structure includes a flat area and a corner area. The corner area connects to an adjacent flat area. A predetermined flat portion is located in the flat area, and a predetermined corner portion is located in the corner area. During assembly, the positive electrode, separator, and negative electrode are sequentially stacked and wound in the same direction to form a wound cell. Then, an aluminum-plastic film is used for encapsulation, electrolyte is injected, and the battery undergoes vacuum sealing, formation, and shaping to obtain the secondary battery.
[0050] The isolation membrane 1 includes a first safety coating 12, a base film 11, and a second safety coating 13 arranged sequentially. The isolation membrane 1 includes a predetermined flat portion and a predetermined corner portion arranged alternately. The first safety coating 12 located at the predetermined corner portion has a first ceramic layer group on the side facing away from the base film 11. The first ceramic layer group includes at least two first ceramic layers 14 arranged at intervals along the length direction of the isolation membrane 1. The second safety coating 13 located at the predetermined corner portion has a second ceramic layer group on the side facing away from the base film 11. The second ceramic layer group includes at least two second ceramic layers 15 arranged at intervals along the length direction of the isolation membrane 1. The first ceramic layer group and the second ceramic layer group are staggered in the length direction of the isolation membrane 1, and the staggered distance S1 is 1 mm.
[0051] In the same predetermined corner, the dimensions of the first ceramic layer 14 and the second ceramic layer 15 in the length direction of the isolation membrane 1 are both W. The spacing between any two adjacent first ceramic layers 14 and the spacing between any two adjacent second ceramic layers 15 are both S2. W is 1.4 mm, S2 is 0.7 mm, W-S1=0.4 mm, and S1-S2=0.3 mm.
[0052] The ratio between the thickness of the first ceramic layer 14 and the thickness of the second ceramic layer 15 is 1.1:1; the thickness h1 of the first ceramic layer 14 is 22 μm and the thickness h2 of the second ceramic layer 15 is 20 μm.
[0053] The first ceramic layer group is located between the adjacent first safety coating 12 and the positive electrode 2, and the second ceramic layer group is located between the adjacent second safety coating 13 and the negative electrode 3. In the length direction of the separator 1, the ratio between the size of the first ceramic layer group and the size of its corner portion is 0.6:1, and the ratio between the size of the second ceramic layer group and the size of its corner portion is 0.6:1.
[0054] The thickness H1 of the first safety coating 12 is 3 μm, and the thickness H2 of the second safety coating 13 is 3 μm.
[0055] The first safety coating 12 and the second safety coating 13 are made of the same material, which is composed of the following components by mass percentage: 88% aluminum oxide, 6% sodium carboxymethyl cellulose binder, and 12% polymer particles butyl methacrylate-acrylonitrile-styrene copolymer.
[0056] The first ceramic layer 14 and the second ceramic layer 15 are made of the same material, both consisting of the following components by mass percentage: 97.5% aluminum oxide and 2.5% sodium carboxymethyl cellulose binder.
[0057] The base membrane 11 is a PP / PE / PP composite membrane (Celgard 2325).
[0058] Example 2
[0059] The difference between this embodiment and Embodiment 1 is that in this embodiment, S1 is 0.5mm, S2 is 0.5mm, W is 0.7mm, W-S1=0.2mm, and S1-S2=0mm.
[0060] Example 3
[0061] The difference between this embodiment and Embodiment 1 is that in this embodiment, S1 is 2mm, S2 is 1.5mm, W is 2.5mm, W-S1=0.5mm, and S1-S2=0.5mm.
[0062] Example 4
[0063] The difference between this embodiment and embodiment 1 is that, in this embodiment, the ratio between the size of the first ceramic layer group and the size of its corner portion along the length direction of the isolation membrane 1 is 0.5:1, and the ratio between the size of the second ceramic layer group and the size of its corner portion is 0.5:1.
[0064] Example 5
[0065] The difference between this embodiment and embodiment 1 is that, in this embodiment, the ratio between the size of the first ceramic layer group and the size of its corner portion along the length direction of the isolation membrane 1 is 0.8:1, and the ratio between the size of the second ceramic layer group and the size of its corner portion is 0.8:1.
[0066] Example 6
[0067] The difference between this embodiment and embodiment 1 is that, in this embodiment, the ratio between the size of the first ceramic layer group and the size of its corner portion along the length direction of the isolation membrane 1 is 0.9:1, and the ratio between the size of the second ceramic layer group and the size of its corner portion is 0.9:1.
[0068] Comparative Example 1
[0069] The difference between this comparative example and Example 1 is that in this comparative example, the first ceramic layer group and the second ceramic layer group correspond one-to-one in the length direction of the isolation membrane, that is, S1 is 0.
[0070] Comparative Example 2
[0071] The difference between this comparative example and Example 1 is that this comparative example does not have a second ceramic layer group.
[0072] Performance testing
[0073] The performance of the secondary batteries in the above embodiments and comparative examples was tested using the following methods:
[0074] (1) Hi-pot defect rate: Using a Hi-pot detector, at a constant voltage, cells with resistance less than the specified value are screened out and judged as NG; the Hi-pot defect rate is calculated according to the following formula: Hi-pot defect rate = number of NG / total number of inputs × 100%;
[0075] (2) K-value defect rate: The K-value of the sample cell is tested using the voltage drop method. (OCV1 voltage - OCV2 voltage) / test interval time. Cells with a voltage drop greater than the specification value are judged as NG. The K-value defect rate is calculated according to the following formula: K-value defect rate = NG quantity / total number of inputs × 100%.
[0076] (3) Lithium plating degree: The sample cell was disassembled every 50 cycles to evaluate the lithium plating state at the interface. The earliest cycle in which lithium plating appeared in the base group was used as the benchmark to compare whether the earliest cycle number of lithium plating appeared was delayed. Under the same cycle period, the improvement effect was determined based on the degree of lithium plating at the interface.
[0077] The test results are shown in Table 1.
[0078] Table 1
[0079] Test Project Hi-pot defect rate (%) K-value defect rate (%) Lithium plating degree Example 1 0.2 0.6 Significant improvement Example 2 0.4 0.7 improve Example 3 0.2 0.5 Significant improvement Example 4 0.1 0.6 improve Example 5 0.2 0.6 Significant improvement Example 6 0.3 0.8 Slight improvement Comparative Example 1 2.2 3.3 Slight improvement Comparative Example 2 0.6 1.2 No improvement
[0080] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.
Claims
1. A separating membrane, characterized in that, The isolation membrane includes a first safety coating, a base film, and a second safety coating arranged sequentially. The isolation membrane includes a predetermined flat portion and a predetermined corner portion arranged alternately. The first safety coating located at the predetermined corner portion has a first ceramic layer group on the side facing away from the base film. The first ceramic layer group includes at least two first ceramic layers arranged at intervals along the length direction of the isolation membrane. The second safety coating located at the predetermined corner portion has a second ceramic layer group on the side facing away from the base film. The second ceramic layer group has at least two second ceramic layers arranged at intervals along the length direction of the isolation membrane. The first ceramic layer group and the second ceramic layer group are staggered in the length direction of the isolation membrane.
2. The separator membrane as described in claim 1, characterized in that, The misalignment distance S1 is 0.5 to 2 mm.
3. The separator membrane as described in claim 2, characterized in that, In the same predetermined corner, the dimensions of the first ceramic layer and the second ceramic layer in the length direction of the isolation membrane are both W, and the spacing between any two adjacent first ceramic layers and the spacing between any two adjacent second ceramic layers are both S2; the isolation membrane satisfies: 0.2mm≤W-S1≤0.5mm, and / or, 0≤S1-S2≤0.5mm.
4. The separator membrane as described in claim 1, characterized in that, The ratio between the thickness of the first ceramic layer and the thickness of the second ceramic layer is (1~1.2):
1.
5. The separator membrane as described in claim 1, characterized in that, The thickness of the first ceramic layer is 0.5–50 μm, and the thickness of the second ceramic layer is 0.5–50 μm.
6. The separator membrane as described in claim 1, characterized in that, Along the length of the isolation membrane, the ratio between the size of the first ceramic layer group and the size of its corner portion is (0.5 to 0.8):1; And / or, the ratio between the size of the second ceramic layer and the size of the corner portion is (0.5 to 0.8):
1.
7. The separator membrane as described in claim 1, characterized in that, The thickness of the first safety coating is 0.5 to 10 μm, and the thickness of the second safety coating is 0.5 to 10 μm.
8. A wound battery cell, characterized in that, It also includes a negative electrode sheet, a positive electrode sheet, and a separator as described in any one of claims 1 to 7, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet, the separator, and the positive electrode sheet are sequentially stacked and wound to form a wound structure, wherein the wound structure includes a flat area and a corner area, the corner area is connected to an adjacent flat area, the predetermined flat portion is located in the flat area, and the predetermined corner portion is located in the corner area.
9. The wound battery cell as described in claim 8, characterized in that, The first ceramic layer group is located between the adjacent first safety coating and the positive electrode, and the second ceramic layer group is located between the adjacent second safety coating and the negative electrode.
10. A secondary battery, characterized in that, Includes the wound battery cell as described in any one of claims 8 to 9.