Diaphragm, battery cell structure and lithium battery

Abstract

The utility model provides a diaphragm, cell structure and lithium battery, diaphragm includes base membrane, cover the ceramic layer of base membrane surface and cover the adhesive layer of ceramic layer outside, the ceramic layer includes mutually connected main body area and thickening area, the thickening area covers the position of base membrane close to the end portion, and the adhesive layer covers the main body area of base membrane. The main body area has uniform thickness, the thickness of the thickening area is larger than that of the main body area, and the adhesive layer comprises a first covering area covering the main body area and a second covering area covering the thickening area. The thickness difference between the thinned area and the central area of the pole piece can be filled by the thickening area, the problem that the gap of the edge area of the cell structure is larger than that of the central area is solved, and the problem of uneven stress caused by the thinned area can be solved by the relatively hard thickening area structure of the ceramic layer.

Description

Technical Field

[0001] This utility model relates to the field of lithium battery technology, specifically to a separator, a cell structure, and a lithium battery. Background Technology

[0002] In lithium batteries, the main function of the separator is to separate the positive and negative electrodes, prevent short circuits caused by contact between the two electrodes, and allow ions to transfer between the positive and negative electrodes.

[0003] In existing processes, thinning zones of a certain width are typically set on the sides of the positive and negative electrode sheets. The thickness of the thinning zone is less than the thickness of the center area of ​​the electrode sheet. When the battery cell assembly is assembled in a positive electrode-separator-negative electrode structure, the gap between the thinning zone and the separator is larger than the gap between the center area and the separator. The lithium ion shuttle path in the thinning zone is longer, and lithium plating is prone to occur due to insufficient electrolyte, which has a certain impact on battery performance. In addition, when the battery electrode assembly is subjected to force, the force is uneven between the thinning zone and the center area, which may lead to breakage or detachment of the electrode material. Patent application CN202023231785.3 discloses an unevenly coated separator and a battery having the separator. The unevenly coated separator includes a separator substrate and a colloidal layer coated on the separator substrate. The colloidal layer includes a base area and a compensation area. The compensation area is located at both ends of the separator substrate, and the base area is located between the two compensation areas and connected to the compensation areas. The thickness of the compensation area is greater than the thickness of the base area. In the above scheme, the thickened structure of the compensation area compensates for the gap effect caused by the thinning area to a certain extent, which enhances the consistency of the cell structure. However, the stiffness of the adhesive layer is insufficient and cannot effectively compensate for the uneven stress between the thinning area and the central area. Utility Model Content

[0004] To address the aforementioned problems, this invention provides a separator that can compensate for the defects caused by the thinning of the electrode in terms of electrical and mechanical properties, thereby improving the performance and safety of the battery.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A diaphragm includes a base membrane, a ceramic layer covering the surface of the base membrane, and an adhesive layer covering the outside of the ceramic layer. The ceramic layer includes a main region and a thickened region connected to each other. The thickened region covers the base membrane near its end. The main region has a uniform thickness, and the thickness of the thickened region is greater than that of the main region. The adhesive layer includes a first covering region covering the main region and a second covering region covering the thickened region.

[0007] Furthermore, the thickness of the thickened region gradually increases in the direction away from the main body region.

[0008] Furthermore, the first coverage area has a uniform thickness, and the thickness of the second coverage area is greater than that of the first coverage area.

[0009] Furthermore, the thickness of the second coverage area gradually increases in the direction away from the first coverage area.

[0010] Furthermore, the ceramic layer and the adhesive layer are disposed on one side of the base film, and the total thickness of the thickened area and the corresponding second covering area exceeds the total thickness of the main body area and the corresponding first covering area by 5~20μm.

[0011] Furthermore, the ceramic layer and the adhesive layer are provided on both sides of the base film, and the total thickness of the thickened area and the corresponding second covering area exceeds the total thickness of the main body area and the corresponding first covering area by 2~10μm.

[0012] Furthermore, the ceramic layer includes a main region and two thickened regions, with the two thickened regions respectively connected to both ends of the main region.

[0013] Furthermore, the thickness of the base film is 6~15μm.

[0014] Another objective of this utility model is to provide a battery cell structure, which includes an electrode and a separator. The electrode includes a foil and a material layer covering the surface of the foil. The material layer includes a central region and a thinned region. The thinned region is located near the end of the material layer. The central region has a uniform thickness, and the thickness of the thinned region is less than that of the central region. At least a portion of the first covering region cooperates with the central region, and at least a portion of the second covering region cooperates with the thinned region.

[0015] Another objective of this invention is to provide a lithium battery comprising the aforementioned cell structure.

[0016] The following beneficial effects can be achieved by applying this utility model:

[0017] 1. The separator provided by this utility model is configured with a ceramic layer consisting of an interconnected main body area and a thickened area. The main body area has a uniform thickness, and the thickness of the thickened area is greater than that of the main body area. When the separator is combined with the electrode, the thickened area can fill the thickness difference between the thinned area and the central area of ​​the electrode, solving the problem that the gap in the edge area of ​​the cell structure is greater than the gap in the central area. Furthermore, the relatively hard thickened area structure of the ceramic layer can also compensate for the uneven stress caused by the thinned area.

[0018] 2. In some embodiments of this utility model, the first covering area of ​​the adhesive layer has a uniform thickness, and the thickness of the second covering area is greater than that of the first covering area. The second covering area of ​​the adhesive layer and the thickened area of ​​the ceramic layer together compensate for the thickness difference between the thinned area and the central area of ​​the electrode sheet, thereby reducing the required thickening range of the thickened area of ​​the ceramic layer, avoiding affecting the winding flexibility of the cell structure, and facilitating the processing and assembly of the battery. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the diaphragm structure in one embodiment;

[0020] Figure 2 for Figure 1 A magnified view of a portion of the image;

[0021] Figure 3 This is a schematic diagram of the battery cell structure in one embodiment;

[0022] Figure 4 This is a schematic diagram of the cell structure in another embodiment;

[0023] In the figure: 1-base film, 2-ceramic layer, 21-main area, 22-thickening area, 3-adhesive layer, 31-first covering area, 32-second covering area, 4-foil layer, 5-material layer, 51-central area, 52-thinning area. Detailed Implementation

[0024] The technical solution of this utility model will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model. Example

[0025] Reference Figure 1 and Figure 2 An embodiment of the first aspect of this utility model provides a separator for lithium batteries, comprising a base film 1, a ceramic layer 2 covering the surface of the base film, and an adhesive layer 3 covering the outside of the ceramic layer 2. In this embodiment, referring to existing lithium battery technology, the base film can be made of materials such as PP and PE, and its thickness can be designed as needed, typically 6~15μm. The ceramic layer includes inorganic materials constituting the ceramic material and an adhesive for bonding the inorganic materials. Considering the maturity of the process, one of the common choices for the aforementioned inorganic materials is Al2O3, and one of the common choices for the aforementioned adhesives is PVDF adhesive. However, as long as the performance requirements of the lithium battery are met, other types of inorganic materials and adhesives can be selected as needed, not limited to the above combinations. One of the common choices for the adhesive layer is PVDF adhesive, but the compatibility between the adhesive layer and the ceramic layer must also be considered.

[0026] More specifically, the ceramic layer 2 includes an interconnected main body region 21 and a thickened region 22. The thickened region 22 covers the base film 1 near its end. The main body region 21 has a uniform thickness, and the thickness of the thickened region 22 is greater than that of the main body region 21. Depending on the processing method, the thickened region may have different structural shapes. For example, in a first embodiment, the thickened region has a uniform thickness overall. In a second embodiment, the thickness of the thickened region gradually increases in the direction away from the main body region. Considering the compatibility between the separator and the electrode in the lithium battery structure and the ease of processing, the second embodiment is generally preferred for the thickened region. In a more preferred embodiment, the thickness increase rate of the portion of the thickened region near the main body region is relatively large, and the thickness increase rate of the portion away from the main body region is relatively small, making the position of the thickened region near the outer end relatively gentle to avoid excessive local pressure on the corners of the electrode. Layer 3 includes a first covering area 31 covering the main body area 21 and a second covering area 32 covering the thickened area. In different embodiments, the first covering area and the second covering area have different relative structures. For example, in the first embodiment, the overall thickness of the adhesive layer is kept relatively uniform, so that the first covering area and the second covering area are macroscopically equal in thickness. In the second embodiment, the thickness of the second covering area is greater than that of the first covering area. When the former embodiment is used, a relatively larger thickness difference should be set between the thickened area and the main body area. When the latter embodiment is used, due to the compensation effect of the second covering area, a relatively smaller thickness difference should be set between the thickened area and the main body area. Considering the performance of the battery, the latter embodiment is preferred, so that the required thickening range is reduced, avoiding affecting the winding flexibility of the cell structure, facilitating the processing and assembly of the battery, and also retaining the characteristics of enhanced mechanical properties.

[0027] Reference Figure 3 The second aspect of this utility model provides a cell structure for a lithium battery, which includes an electrode and a separator. The electrode is divided into a positive electrode and a negative electrode, and the separator is disposed between the positive electrode and the negative electrode. Specifically, the electrode includes a foil 4 and a material layer 5 covering the surface of the foil. The material layer 5 includes a central region 51 and a thinned region 52. The thinned region 52 is located near the end of the material layer. The central region 51 has a uniform thickness, and the thickness of the thinned region is less than that of the central region, and the thickness gradually decreases in the direction away from the central region. When the electrode and the separator are assembled, at least a portion of the first covering region 31 cooperates with the central region 51, and at least a portion of the second covering region 32 cooperates with the thinned region 52. The thickness difference between the thickened region and the main body region is used to compensate for the thickness difference between the thinned region and the central region. Alternatively, in some embodiments, the thickness difference between the second covering region and the first covering region is also used to compensate for the thickness difference between the thinned region and the central region. (See reference...) Figure 3 and Figure 4The electrode structure and the separator structure correspond to each other. When the electrode has a thinned region at only one end, the separator also has a thickened region at only one end. When both ends of the electrode have thinned regions, both ends of the separator have thickened regions. Furthermore, in some embodiments, the separator may be a single-sided separator with a ceramic layer and an adhesive layer covering only one side. In this case, the thickness difference between the thickened region and the main body region should be larger than that of a double-sided separator. For example, the thickness difference of a double-sided separator can be set to 2~10μm, and the thickness difference of a single-sided separator can be set to 5~20μm.

[0028] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A diaphragm, characterized in that: The material includes a base film (1), a ceramic layer (2) covering the surface of the base film, and an adhesive layer (3) covering the outside of the ceramic layer. The ceramic layer includes a main body region (21) and a thickened region (22) connected to each other. The thickened region covers the base film near its end. The main body region (21) has a uniform thickness. The thickness of the thickened region (22) is greater than that of the main body region. The adhesive layer includes a first covering region (31) covering the main body region and a second covering region (32) covering the thickened region.

2. The diaphragm according to claim 1, characterized in that: The thickness of the thickened region (22) gradually increases in the direction away from the main body region.

3. The diaphragm according to claim 1, characterized in that: The first coverage area (31) has a uniform thickness, and the second coverage area (32) has a greater thickness than the first coverage area.

4. A diaphragm according to claim 3, characterized in that: The thickness of the second coverage area (32) gradually increases in the direction away from the first coverage area (31).

5. A diaphragm according to claim 1, characterized in that: The ceramic layer (2) and the adhesive layer (3) are provided on one side of the base film (1), and the total thickness of the thickened area (22) and the corresponding second covering area (32) exceeds the total thickness of the main body area (21) and the corresponding first covering area (31) by 5~20 μm.

6. A diaphragm according to claim 1, characterized in that: The ceramic layer (2) and the adhesive layer (3) are provided on both sides of the base film. The total thickness of the thickened area (22) and the corresponding second covering area (32) exceeds the total thickness of the main body area (21) and the corresponding first covering area (31) by 2~10 μm.

7. A diaphragm according to claim 1, characterized in that: The ceramic layer includes a main region (21) and two thickened regions (22), with the two thickened regions respectively connected to both ends of the main region.

8. A diaphragm according to claim 1, characterized in that: The thickness of the base film (1) is 6~15μm.

9. A battery cell structure, characterized in that: The device includes an electrode sheet and a diaphragm as described in any one of claims 1 to 8. The electrode sheet includes a foil (4) and a material layer (5) covering the surface of the foil. The material layer includes a central region (51) and a thinned region (52). The thinned region is located near the end of the material layer. The central region has a uniform thickness. The thickness of the thinned region is less than that of the central region. At least a portion of the first covering region (31) mates with the central region (51), and at least a portion of the second covering region (32) mates with the thinned region (52).

10. A lithium battery, characterized in that: Includes the cell structure described in claim 9.

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