Pole piece structure and secondary battery comprising same

Abstract

The utility model discloses a pole piece structure, which comprises a base material layer and an active layer coated on the base material layer, the area of the base material layer, which needs to be split and die-cut, is coated with an insulating protection layer, and the insulating protection layer is positioned above the active layer. The utility model also provides a secondary battery comprising the pole piece structure. The pole piece structure provided by the utility model can remarkably reduce the K value of the battery cell, improve the consistency of the battery and prolong the service life of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a pole piece structure and a secondary battery containing the same. Background Art

[0002] With the rapid development of science and technology and the continuous maturity of the market, in the foreseeable future, the market demand for batteries will show an explosive growth, and the requirements for battery performance will continue to increase. Voltage drop is an important indicator of battery performance, which affects the consistency of the battery and is closely related to the battery's service life and safety performance.

[0003] Usually, we use K value (battery voltage drop per unit time) to describe the self-discharge rate of the battery cell. The factors that affect the K value of the battery cell are mainly divided into chemical side reactions and physical micro short circuits. Chemical side reactions are usually closely related to the material system, while physical micro short circuits are inseparable from the battery electrode structure, process technology, and environmental control. Therefore, how to reduce the K value of the battery by developing a new electrode structure is an important part of improving the life and safety performance of lithium-ion batteries. Utility Model Content

[0004] In order to solve the above technical problems, the utility model provides a pole piece structure and a secondary battery containing the same, which can significantly reduce the K value of the battery cell and improve the consistency and service life of the battery.

[0005] The technical solution provided by the utility model is as follows:

[0006] A pole piece structure comprises a substrate layer and an active layer coated on the substrate layer, wherein the substrate layer needs to be coated with an insulating protective layer in the stripe die-cutting area, and the insulating protective layer is located above the active layer.

[0007] Preferably, the protective layer has a thickness of 1.0 to 50.0 μm.

[0008] Preferably, the width of the protective layer is 2 to 60 mm.

[0009] Preferably, the porosity of the protective layer is 10% to 50%.

[0010] Preferably, the substrate layer is a current collector, and the thickness of the substrate layer is 0.5 to 20 μm.

[0011] Preferably, the active layer is one of lithium sodium ion positive electrode or negative electrode materials, and the thickness of the active layer is 10 to 300 μm.

[0012] Preferably, both the upper surface and the lower surface of the substrate layer are coated with an active layer and an insulating protective layer.

[0013] A secondary battery comprises the above-mentioned pole piece structure.

[0014] The present application has the following advantages over the prior art:

[0015] When the electrode structure of the present application is stripped and die-cut, since the insulating protective layer is located above the active layer, it absorbs the energy from the cutting, thereby protecting the active layer. It can effectively avoid the dust pollution generated during cutting, further reduce the physical micro-short circuit of the battery cell, and can significantly reduce the K value of the battery cell, thereby improving the consistency and service life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a structural schematic diagram of the pole piece structure in the embodiment of the utility model.

[0018] Reference numerals:

[0019] 1. Base material layer; 2. Active layer; 3. Insulation protective layer. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] like Figure 1 As shown, an embodiment of the utility model provides a pole piece structure, including a substrate layer and an active layer coated on the substrate layer. The substrate layer needs to be coated with an insulating protective layer in the strip-cut area, and the insulating protective layer is located above the active layer.

[0022] When the pole piece structure of this embodiment is stripped and die-cut, since the insulating protective layer is located above the active layer, it absorbs the energy from the cutting, thereby protecting the active layer. It can effectively avoid the dust pollution generated during the cutting, further reduce the physical micro-short circuit of the battery cell, and can significantly reduce the K value of the battery cell, thereby improving the consistency and service life of the battery.

[0023] In this embodiment, the protective layer can be a high molecular polymer (such as one or more of polyamide-imide, polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, polyolefins, and polyurethane), or a mixture of a high molecular polymer and other insulating functional materials. The preparation method of the protective layer is as follows: the above materials are prepared into a uniform and stable slurry by stirring, and the solid content thereof is 1% to 20%, and the viscosity thereof is 200 to 10000 mPa.s, and then the slurry is coated on the pole piece strip die-cutting area. The thickness of the protective layer is 1.0 to 50.0 μm. The width of the protective layer is 2 to 60 mm. The porosity of the protective layer is 10% to 50%.

[0024] In this embodiment, the substrate layer is a current collector, which can be aluminum foil, copper foil, or composite foil, and the thickness of the substrate layer is 0.5-20 μm. The upper and lower surfaces of the substrate layer are coated with an active layer and an insulating protective layer.

[0025] Preferably, the active layer is one of lithium sodium ion positive electrode or negative electrode materials, and the thickness of the active layer is 10 to 300 μm.

[0026] A secondary battery comprises the above-mentioned pole piece structure.

[0027] Taking the 4670160 model lithium-ion battery as an example, the positive and negative active layers are coated on the surface of the substrate through conventional processes such as stirring, coating, and rolling. The polymer and the organic solvent are mixed in a weight ratio of 1:9, stirred for 6 hours, and then vacuum treated at a vacuum degree of -85kPa for 30 minutes to obtain the relevant insulating protective layer glue, in which the polymer content is 10% and the glue viscosity is 2350mPa.s. The glue is applied to the strip die-cut areas of the positive and negative electrodes, and baked at 90°C for 10 minutes to form an insulating protective layer with a coating width of 4mm and a single-sided coating thickness of 5μm. Similarly, the glue is applied to the strip die-cut area on the other side of the electrode to prepare the electrode structure provided by the present technical solution.

[0028] It and the conventional electrode structure without a protective layer are simultaneously subjected to striping, die-cutting, lamination & winding, assembly, liquid injection, and chemical composition to prepare a 4670160 battery. The battery cell prepared with the electrode structure provided by this technical solution is the experimental group, and the battery cell with the conventional electrode structure is the control group. Using the 1+1+2 K value test process, they are respectively subjected to OCV tests, and the K value is calculated by K=(OCV1-OCV2) / (T2-T1). The obtained K value results are shown in Table 1 below:

[0029] Table 1 K value calculation results

[0030]

[0031]

[0032] As can be seen from Table 1, the K value of the experimental group of cells is about 60 times lower than that of the control group of cells, which shows that this technical solution can significantly reduce the physical micro-short circuit of the cells, reduce the K value, and improve the consistency and service life of the cells.

[0033] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A pole piece structure, characterized in that: It comprises a substrate layer (1) and an active layer (2) coated on the substrate layer (1), wherein the substrate layer (1) needs to be coated with an insulating protective layer (3) in the strip die-cutting area, and the insulating protective layer (3) is located above the active layer (2).

2. The pole piece structure according to claim 1, characterized in that: The thickness of the protective layer (3) is 1.0 to 50.0 μm.

3. The pole piece structure according to claim 1, characterized in that: The width of the protective layer (3) is 2 to 60 mm.

4. The pole piece structure according to claim 1, characterized in that: The porosity of the protective layer (3) is 10% to 50%.

5. The pole piece structure according to any one of claims 1 to 4, characterized in that: The substrate layer (1) is a current collector, and the thickness of the substrate layer (1) is 0.5 to 20 μm.

6. The pole piece structure according to any one of claims 1 to 4, characterized in that: The active layer (2) is one of lithium sodium ion positive electrode or negative electrode materials, and the thickness of the active layer (2) is 10 to 300 μm.

7. The pole piece structure according to any one of claims 1 to 4, characterized in that: The upper surface and the lower surface of the substrate layer (1) are both coated with an active layer (2) and an insulating protective layer (3).

8. A secondary battery, characterized in that: The invention comprises a pole piece structure as claimed in any one of claims 1 to 7.

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