Diaphragm structure and lithium ion battery

Abstract

The diaphragm structure comprises a base membrane layer, ceramic layers, a first bonding layer and a second bonding layer, and the ceramic layers are coated on the two side surfaces of the base membrane layer; the surface, far away from the base film layer, of the ceramic layer is coated with a first bonding layer; the base film layer, the ceramic layer and the first bonding layer are equal in width; the edges of the two sides of the face, away from the ceramic layer, of the first bonding layer are coated with second bonding layers in the length direction of the base film layer. The edge of the first bonding layer is coated with the second bonding layer, so that the bonding capacity of the edge of the diaphragm can be effectively improved, the diaphragm and a pole piece can be highly attached in the hot pressing process of the core package, the polarization internal resistance of the lithium ion battery in circulation is reduced, and the purple edge phenomenon of the pole piece is relieved.

Description

Technical Field

[0001] This utility model relates to the field of lithium-ion battery technology, and in particular to a separator structure and a lithium-ion battery. Background Technology

[0002] In recent years, lithium-ion batteries have developed rapidly in the fields of new energy vehicles, portable electronic products, and large-scale energy storage devices, attracting widespread attention. Their key performance characteristics, such as energy density, rate capability, cycle life, and safety, are the focus of industry attention and are crucial for enhancing the market competitiveness of lithium-ion batteries. As an important component of lithium-ion batteries, the performance of the separator significantly affects the battery's overall performance. While researchers are working to improve the thermal stability and mechanical strength of the separator, its adhesive properties have received relatively little attention.

[0003] An existing invention patent application with publication number CN116780107A discloses a separator and a battery. The separator includes a base membrane and a ceramic layer; the ceramic layer is disposed on at least one surface of the base membrane; the ceramic layer includes ceramic and an adhesive, which is solid at room temperature and melts at a temperature greater than 130°C, and has re-adhesive properties.

[0004] In the aforementioned scheme, only a base film and a ceramic layer are placed between the positive and negative electrodes, which are directly bonded to each other. However, during the hot pressing process of the core pack, the compaction ability at the edges of the electrodes is less than that in the middle, and the edges of the core pack cannot be completely wrapped by the separator. Therefore, the adhesion at the edges of the electrodes is weak. In addition, after the battery undergoes multiple charge-discharge cycles, the expansion stress in the electrodes extends towards the edges, resulting in loose adhesion at the edges, increased resistance to lithium-ion transmission, increased internal resistance, and purple edge phenomena, which adversely affect the cycle life of the lithium-ion battery. Therefore, improving the coating structure of the separator and strengthening the adhesion at the edges of the cell electrodes is of great significance for reducing the polarization internal resistance of lithium-ion batteries and improving their cycle life. Utility Model Content

[0005] In view of this, this utility model proposes a separator structure and lithium-ion battery with strong edge bonding, which can effectively improve application stability, in order to solve the problem that the separator and electrode edge bonding is not tight enough in the existing battery cell structure, which affects battery performance.

[0006] The technical solution of this utility model is implemented as follows:

[0007] On the one hand, this utility model provides a diaphragm structure, including a base film layer, a ceramic layer, a first adhesive layer, and a second adhesive layer, wherein,

[0008] The base film layer is coated with a ceramic layer on both sides;

[0009] A first adhesive layer is coated on the ceramic layer away from the base film layer;

[0010] The base film layer, ceramic layer, and first adhesive layer are of equal width;

[0011] The second adhesive layer is coated on both sides of the first adhesive layer away from the ceramic layer along the length of the base film layer.

[0012] Based on the above technical solutions, preferably, the coating width of the second adhesive layer on one side edge of the first adhesive layer is 2 to 15 mm, and the width ratio of the second adhesive layer to the first adhesive layer is 1:20 to 1:60.

[0013] Based on the above technical solutions, preferably, the coating thickness of the first adhesive layer is greater than or equal to the coating thickness of the second adhesive layer.

[0014] Based on the above technical solutions, preferably, the coating thickness of the first adhesive layer is 0.3 to 3 μm, and the coating thickness of the second adhesive layer is 0.3 to 2 μm.

[0015] Based on the above technical solutions, preferably, the first adhesive layer and the second adhesive layer are made of adhesive polymers, and the particle size of the adhesive polymer in the first adhesive layer is larger than that in the second adhesive layer.

[0016] Based on the above technical solutions, preferably, the particle size of the first adhesive layer is 2 to 8 μm, and the particle size of the second adhesive layer is 0.5 to 6 μm.

[0017] Based on the above technical solutions, preferably, the first adhesive layer is one or more of PVDF, SBR, polypropylene and its copolymers, and polyethylene and its copolymers, and the first adhesive layer is coated by roller coating.

[0018] Based on the above technical solutions, preferably, the second adhesive layer is one or more of PVDF, PMMA, silicone, polyimide microspheres, polyetherimide microspheres, and polyacrylonitrile microspheres, and the second adhesive layer is applied by spraying.

[0019] Based on the above technical solutions, preferably, the base membrane layer is a porous polyolefin membrane or its composite membrane.

[0020] On the other hand, this utility model provides a lithium-ion battery, including the above-mentioned separator structure.

[0021] The membrane structure and lithium-ion battery of this invention have the following advantages over the prior art:

[0022] (1) By coating the edge of the first adhesive layer with the second adhesive layer, the adhesion ability of the separator edge can be effectively improved, so as to ensure that the separator and the electrode can be highly bonded during the hot pressing process of the core pack, thereby reducing the polarization internal resistance of the lithium-ion battery in the cycle and reducing the purple edge phenomenon of the electrode.

[0023] (2) The first adhesive layer is coated by roller coating, which ensures that the overall membrane has suitable adhesion and lithium ion passing kinetics. The second adhesive layer is coated by spray coating, and the adhesive polymer used in the second adhesive layer has a larger particle size and a thinner thickness. This plays a supporting role between the membrane and the electrode during the hot pressing process of the core package. While increasing the adhesive strength, it can avoid excessive compaction at the edge, thus ensuring suitable lithium ion passing kinetics. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a perspective view of the diaphragm structure of this utility model;

[0026] Figure 2 This is a structural diagram of the end face of the diaphragm structure of this utility model;

[0027] In the diagram: 1. Base film layer; 2. Ceramic layer; 3. First adhesive layer; 4. Second adhesive layer. Detailed Implementation

[0028] The technical solutions of this utility model will be clearly and completely described below with reference to the embodiments of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. 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.

[0029] like Figures 1-2 As shown, the diaphragm structure of this utility model includes a base film layer 1, a ceramic layer 2, a first adhesive layer 3, and a second adhesive layer 4.

[0030] like Figure 1 and Figure 2As shown, ceramic layers 2 are coated on both sides of the base film layer 1; a first adhesive layer 3 is coated on the surface of the ceramic layer 2 away from the base film layer 1; the base film layer 1, ceramic layer 2 and the first adhesive layer 3 are of equal width; a second adhesive layer 4 is coated on both sides of the first adhesive layer 3 away from the ceramic layer 2 along the length direction of the base film layer 1.

[0031] As described above, the core pack of a lithium-ion battery is formed by winding electrodes and a separator. The electrode substrate and the base film layer of the separator are strip materials before preparation. They are stored by winding them with rollers. When output, they are strip structures with the output direction being the length direction mentioned above. Correspondingly, the width direction is parallel to the axial direction of the storage rollers.

[0032] A ceramic layer 2 is disposed on the base film layer 1, which can promote the migration of lithium ions between the electrode and the separator, and improve the lithium ion conductivity and overall performance of the battery.

[0033] Meanwhile, the base film layer 1 and ceramic layer 2 ensure the overall strength of the diaphragm and give the diaphragm good heat resistance.

[0034] Among them, the first adhesive layer 3 on the side of the ceramic layer 2 is used to bond the electrode sheet, and the second adhesive layer 4 is also used to bond the electrode sheet. Since the second adhesive layer 4 is located at the edge of the first adhesive layer 3, it can improve the bonding strength at the edge, so that the separator and the electrode sheet are stably bonded, thereby reducing the polarization internal resistance of the lithium-ion battery during cycling and reducing the purple edge phenomenon of the electrode sheet.

[0035] Specifically, the coating width of the second adhesive layer 4 on one side edge of the first adhesive layer 3 is 2 to 15 mm, and the width ratio of the second adhesive layer 4 to the first adhesive layer 3 is 1:20 to 1:60.

[0036] As described above, in order to ensure good adhesion, the width ratio of the first adhesive layer 3 to the second adhesive layer 4 is controlled at 1:20 to 1:60 to ensure that the second adhesive layer 4 can stably bond the electrode sheet to the diaphragm.

[0037] The surface of the first adhesive layer 3 has two second adhesive layers 4, and the width ratio mentioned above is the ratio of a single second adhesive layer 4 to the first adhesive layer 3.

[0038] Depending on the specific battery model and electrode width requirements, the coating width of the second adhesive layer 4 is controlled between 2 and 15 mm.

[0039] In this diaphragm structure, the coating thickness of the first adhesive layer 3 is greater than or equal to the coating thickness of the second adhesive layer 4;

[0040] Specifically, the coating thickness of the first adhesive layer 3 is 0.3 to 3 μm, and the coating thickness of the second adhesive layer 4 is 0.3 to 2 μm.

[0041] In this membrane structure, the first adhesive layer 3 and the second adhesive layer 4 are made of adhesive polymers, and the particle size of the adhesive polymer in the first adhesive layer 3 is larger than that in the second adhesive layer 4.

[0042] Specifically, the adhesive polymer particles in the first adhesive layer 3 have a particle size of 2–8 μm, and the adhesive polymer particles in the second adhesive layer 4 have a particle size of 0.5–6 μm.

[0043] In this diaphragm structure, the first adhesive layer 3 is one or more of PVDF, SBR, polypropylene and its copolymers, and polyethylene and its copolymers, and the first adhesive layer 3 is coated by roller coating.

[0044] The second adhesive layer 4 is one or more of PVDF, PMMA, silicone, polyimide microspheres, polyetherimide microspheres, and polyacrylonitrile microspheres, and the second adhesive layer 4 is applied by spraying.

[0045] Among them, PVDF is polyvinylidene fluoride, SBR is styrene-butadiene rubber, and PMMA is polymethyl methacrylate.

[0046] As mentioned above, the materials, coating thickness, and particle size of the adhesive polymer in the first adhesive layer 3 and the second adhesive layer 4 are set. The first adhesive layer 3 can ensure that the separator as a whole has suitable adhesion and lithium-ion passage kinetics. On the other hand, the second adhesive layer 4 is coated by spraying, and the adhesive polymer particle size of the second adhesive layer 4 is larger and the thickness is thinner. During the hot pressing of the core package, it plays a supporting role between the separator and the electrode, which increases the bonding strength between the two while avoiding excessive compaction at the edge, thus ensuring suitable lithium-ion passage kinetics.

[0047] Specifically, the base membrane layer 1 is a porous polyolefin membrane and its composite membrane.

[0048] Specific implementation steps:

[0049] A ceramic layer 2 is provided on both sides of the base film layer 1, and a first adhesive layer 3 is coated on the ceramic layer 2 by roller pressing. Finally, a second adhesive layer 4 is sprayed on the edge of the first adhesive layer 3.

[0050] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. 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 structure, characterized in that: It includes a base film layer (1), a ceramic layer (2), a first adhesive layer (3), and a second adhesive layer (4), wherein, The ceramic layer (2) is coated on both sides of the base film layer (1); The ceramic layer (2) is coated with the first adhesive layer (3) on the surface away from the base film layer (1); The base film layer (1), the ceramic layer (2), and the first adhesive layer (3) are of equal width; The first adhesive layer (3) has a second adhesive layer (4) coated on both sides of the side away from the ceramic layer (2) along the length direction of the base film layer (1).

2. The diaphragm structure as described in claim 1, characterized in that: The coating width of the second adhesive layer (4) on one side edge of the first adhesive layer (3) is 2 to 15 mm, and the width ratio of the second adhesive layer (4) to the first adhesive layer (3) is 1:20 to 1:

60.

3. The diaphragm structure as described in claim 1, characterized in that: The coating thickness of the first adhesive layer (3) is greater than or equal to the coating thickness of the second adhesive layer (4).

4. The diaphragm structure as described in claim 3, characterized in that: The coating thickness of the first adhesive layer (3) is 0.3 to 3 μm, and the coating thickness of the second adhesive layer (4) is 0.3 to 2 μm.

5. The diaphragm structure as described in claim 1, characterized in that: The first adhesive layer (3) and the second adhesive layer (4) are made of adhesive polymers, and the particle size of the adhesive polymer in the first adhesive layer (3) is larger than that in the second adhesive layer (4).

6. The diaphragm structure as described in claim 5, characterized in that: The adhesive polymer particle size of the first adhesive layer (3) is 2 to 8 μm, and the adhesive polymer particle size of the second adhesive layer (4) is 0.5 to 6 μm.

7. The diaphragm structure according to any one of claims 1 to 6, characterized in that: The first adhesive layer (3) is one of PVDF, SBR, polypropylene and its copolymers, and polyethylene and its copolymers, and the first adhesive layer (3) is coated by roller coating.

8. The diaphragm structure according to any one of claims 1 to 6, characterized in that: The second adhesive layer (4) is one of PVDF, PMMA, silicone, polyimide microspheres, polyetherimide microspheres, and polyacrylonitrile microspheres, and the second adhesive layer (4) is applied by spraying.

9. The diaphragm structure according to any one of claims 1 to 6, characterized in that: The base membrane layer (1) is a porous polyolefin membrane and its composite membrane.

10. A lithium-ion battery, characterized in that: Includes the membrane structure as described in any one of claims 1 to 9.

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