Winding type positive plate and battery

Abstract

The winding type positive plate comprises a positive current collector and a slurry layer arranged on at least one surface of the positive current collector, a blank area is further arranged on the surface, provided with the slurry layer, of the positive current collector, and the blank area and the slurry layer are adjacently arranged in the length direction. The blank area is in contact with the corresponding end part of the slurry layer; the positive plate is spirally wound along the length direction to form a plurality of straight line parts and a plurality of bent parts from inside to outside, and the innermost bent part is a blank area. According to the utility model, the blank area is arranged at the innermost bending part after the positive plate is wound, so that the slurry layer at the innermost bending part can be prevented from cracking and even falling off after the positive plate is wound and hot-pressed. Therefore, when the positive plate disclosed by the utility model is assembled in the battery, the short circuit of the battery caused by the cracking and falling of the slurry layer at the innermost bending part of the positive plate is avoided, and the yield of battery production is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a wound positive electrode sheet and a battery. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, high average output voltage, low self-discharge, no memory effect and long cycle life, and are widely used in electronic equipment, energy storage devices and new energy vehicles. With the advancement of society and technology, consumers have higher and higher requirements for the performance of lithium-ion batteries, which means that the requirements for the manufacturing technology of lithium-ion batteries are also getting higher and higher.

[0003] The square wound battery is a common lithium-ion battery. Its positive and negative electrodes are generally made by continuous coating, and then wound with a diaphragm using a winding needle to form a battery cell. However, the innermost circle of the wound battery cell is the positive electrode, which is bent 180 degrees in the opposite direction after winding with a winding needle. Since the positive electrode is brittle, the innermost bend of the positive electrode is prone to cracking after hot pressing of the wound battery cell, causing the positive electrode slurry to fall off and cause a short circuit, etc., resulting in a low battery yield. Utility Model Content

[0004] In order to solve the above-mentioned defects in the prior art, one of the purposes of the present invention is to provide a wound positive electrode sheet to prevent the innermost curved portion of the positive electrode sheet from cracking and dropping slurry after winding and hot pressing.

[0005] In order to solve the above-mentioned defects in the prior art, a second object of the present invention is to provide a battery having the characteristic of high yield rate.

[0006] The technical solution provided according to one of the purposes of the utility model is as follows:

[0007] A wound positive electrode sheet, comprising: a positive electrode current collector and a slurry layer provided on at least one surface of the positive electrode current collector, wherein the surface of the positive electrode current collector provided with the slurry layer is also provided with a blank area, the blank area and the slurry layer are adjacently provided along the length direction, and the blank area and the corresponding end of the slurry layer are in contact;

[0008] The positive electrode sheet is spirally wound along the length direction to form a plurality of straight portions and a plurality of curved portions from the inside to the outside, and the innermost curved portion is a blank area.

[0009] Furthermore, in the wound state, the distance between the two end portions of the blank area corresponding to the slurry layer is greater than the thickness of the slurry layer.

[0010] Furthermore, in the wound state, the distance between the two end portions of the blank area corresponding to the slurry layer is less than 1.5 times the thickness of the slurry layer.

[0011] Furthermore, the thickness of the positive electrode current collector is 12 μm±4 μm.

[0012] Furthermore, the surface of the positive electrode current collector is also provided with an insulating layer extending in the length direction, and the insulating layer is provided on both sides of the slurry layer in the width direction.

[0013] Furthermore, a gap is provided between the slurry layer and the insulating layer, a color layer is provided between the slurry layer and the insulating layer, and the color layer is in contact with corresponding ends of the slurry layer and the insulating layer.

[0014] Further, the blank area extends along the width direction, and the blank area contacts the corresponding end portion of the insulating layer in the width direction.

[0015] Furthermore, the thickness of the slurry layer and the thickness of the insulating layer are both greater than the thickness of the color layer.

[0016] Further, the thickness of the slurry layer is equal to the thickness of the insulating layer.

[0017] The technical solution provided according to the second purpose of the utility model is as follows:

[0018] A battery comprises a negative electrode sheet, a separator and a positive electrode sheet which are wound together, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet.

[0019] Beneficial effects:

[0020] The utility model provides a blank area, and the blank area is provided at the innermost curved part of the positive electrode sheet after winding, so as to prevent the slurry layer of the innermost curved part from cracking or even falling off after the positive electrode sheet is rolled and hot-pressed. Therefore, when the positive electrode sheet of the utility model is assembled in a battery, the battery short circuit will not be caused by the cracking and falling off of the slurry layer of the innermost curved part of the positive electrode sheet, thereby improving the yield rate of battery production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of coating of the wound positive electrode sheet of the utility model;

[0022] Figure 2 It is a top view of the wound battery cell of the present invention.

[0023] Reference numerals:

[0024] 10. Positive electrode sheet; 101. Straight portion; 102. Curved portion; 20. Negative electrode sheet; 30. Separator; 1. Positive electrode current collector; 2. Slurry layer; 3. Blank area; 4. Insulating layer; 5. Color layer. DETAILED DESCRIPTION

[0025] For better understanding and implementation, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0026] In the description of the present invention, it should be noted that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc. indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0028] The utility model provides a battery, referring to Figure 2 The battery of the utility model is a square wound lithium-ion battery, which is obtained by loading a wound battery cell into a metal shell of a square battery, injecting liquid, and packaging. The wound battery cell includes a positive electrode sheet 10, a negative electrode sheet 20, and a separator 30 that are wound, and the separator 30 is arranged between the positive electrode sheet 10 and the negative electrode sheet 20. The wound battery cell is wound by a winding needle, and then the positive electrode sheet 10, the negative electrode sheet 20, and the separator 30 are fitted and pressed according to the setting sequence to ensure the electrochemical performance of the battery. When the positive electrode sheet 10, the negative electrode sheet 20, and the separator 30 are wound by the winding needle, they are all bent 180 degrees in the opposite direction. Since the separator 30 has good toughness and the negative electrode slurry on the negative electrode sheet 20 has strong adhesion, the winding hot pressing has basically no effect on the separator 30 and the negative electrode sheet 20. However, the positive electrode sheet 10 is relatively brittle, and the adhesion of the positive electrode slurry on the positive electrode sheet 10 is relatively low. After the wound battery cell is hot-pressed, the bends of the positive electrode sheet 10 away from the center are not easy to crack due to the auxiliary buffering of the diaphragm 30 and the negative electrode sheet 20, while the innermost bends have no buffering or less buffering and are prone to cracking, causing the positive electrode slurry to fall and cause a short circuit, etc., resulting in a low battery yield.

[0029] To this end, the utility model also provides a wound positive electrode sheet, see Figure 1 Whether in the coated state or the wound state, the length direction and width direction of the utility model are Figure 1The direction shown is taken as the standard, and the thickness direction is perpendicular to the plane formed by the length direction and the thickness direction. On this basis, the wound positive electrode sheet of the utility model includes a positive electrode collector 1 and a slurry layer 2 provided on at least one surface of the positive electrode collector 1, and the surface of the positive electrode collector 1 provided with the slurry layer 2 is also provided with a blank area 3, and the blank area 3 and the slurry layer 2 are adjacently arranged along the length direction, and the blank area 3 and the corresponding end of the slurry layer 2 are in contact. The positive electrode sheet 10 is spirally wound along the length direction to form a plurality of straight portions 101 and a plurality of curved portions 102 from the inside to the outside, and the innermost curved portion 102 is the blank area 3.

[0030] Specifically, the positive electrode current collector 1 may have only one surface coated with the positive electrode slurry to form the slurry layer 2. In this case, the blank area 3 is arranged on the same side as the slurry layer 2. The blank area 3 and the slurry layer 2 are arranged adjacent to each other along the length direction and the corresponding ends are in contact, so that the blank area 3 divides the slurry layer 2 into two sections in the length direction. Since the blank area 3 is essentially the positive electrode current collector 1 without any substance coated in the blank area 3, the blank area 3 is arranged so that two sections of the slurry layer 2 are arranged at intervals in the length direction on the positive electrode current collector 1. In addition, the length of the slurry layer 2 near the winding center is shorter, so that the blank area 3 is just located at the innermost curved portion 102 after the positive electrode sheet 10 is wound, and the blank area 3 covers the entire innermost curved portion 102, that is, the innermost curved portion 102 is not coated with any substance.

[0031] When positive electrode slurry is coated on both opposite surfaces of the positive electrode collector 1 to form slurry layers 2 on both opposite surfaces of the positive electrode collector 1 , blank areas 3 are provided on both surfaces. The positions of the blank areas 3 on the two surfaces correspond and are both located at the innermost curved portion 102 .

[0032] It should be noted that in the present invention, the slurry layer 2 is provided on both opposite surfaces of the positive electrode current collector 1, and the thickness of the slurry layer 2 on both surfaces is equal. On this basis, the "thickness" in the present invention refers to the thickness of both sides.

[0033] Therefore, the present invention provides the blank area 3, and provides the blank area 3 at the innermost curved portion 102 after the positive electrode sheet 10 is wound, so as to prevent the slurry layer 2 at the innermost curved portion 102 from cracking or even falling off after the positive electrode sheet is wound and hot-pressed. Therefore, when the positive electrode sheet 10 of the present invention is assembled in a battery, the battery short circuit will not be caused by the cracking and falling off of the slurry layer 2 at the innermost curved portion 102 of the positive electrode sheet 10, thereby improving the yield rate of battery production.

[0034] It is worth noting that the present invention only sets the blank area 3 in the innermost curved portion 102. This is because the innermost curved portion 102 is directly wound and bent without any buffer or with little buffer, and it is easy to crack and cause the slurry layer 2 to fall off. However, the curved portions 102 at other positions are buffered by the accumulated thickness of the separator 30, the negative electrode sheet 20, etc., and the slurry layer 2 is not easy to crack and fall off.

[0035] Furthermore, since the innermost curved portion 102 is the blank area 3 , the slurry layer 2 has a certain thickness during winding, so the slurry layer 2 and the diaphragm 30 are attached and pressed tightly, and a gap is set between the blank area 3 and the diaphragm 30 .

[0036] After the positive electrode sheet 10 is wound and bent using a winding needle, the curved portion 102 is an arc-shaped structure and is located at at least one end in the length direction of the straight portion 101. In order to prevent the slurry layer 2 from cracking and falling off at the innermost curved portion 102, the slurry layer 2 is not provided at the innermost curved portion 102, that is, the arc-shaped segments of the curved portion 102 are all blank areas 3, and the blank areas 3 are arc-shaped structures after winding. The most basic requirement for winding the positive electrode sheet 10 is that the slurry layers 2 on the two opposite surfaces are non-contact after winding. Therefore, in the wound state, the spacing between the two ends of the corresponding slurry layer 2 of the blank area 3 is greater than the thickness of the slurry layer 2. That is, in the wound state, the spacing between the two ends of the arc-shaped segment of the blank area 3 is greater than the thickness of the slurry layer 2 to ensure that the innermost curved portion 102 is not coated with any material.

[0037] If the blank area 3 is too long, the weight of the battery cell will increase and the battery capacity will be lost. Therefore, in the wound state, the distance between the two ends of the blank area 3 corresponding to the slurry layer 2 is less than 1.5 times the thickness of the slurry layer 2. Controlling the length of the blank area 3 can avoid increasing the weight of the battery cell and damaging the capacity of the battery, and ensure that the innermost curved portion 102 of the positive electrode sheet 10 will not fall off the slurry layer 2 during winding, thereby avoiding the risk of short circuit.

[0038] In the present invention, the thickness of the positive electrode current collector is 12 μm ± 4 μm. This thickness range can ensure the mechanical strength of the positive electrode current collector 1 and realize the lightness of the positive electrode current collector 1. The application in the battery can improve the energy density of the battery.

[0039] In addition, the surface of the positive electrode current collector 1 is further provided with an insulating layer 4 extending continuously along the length direction, and the insulating layer 4 is provided on both sides of the slurry layer 2 in the width direction to play an insulating role.

[0040] A gap is set between the slurry layer 2 and the insulating layer 4. On the one hand, the active material in the slurry layer 2 is prevented from flowing and diffusing to the insulating layer 4, thereby avoiding the loss of active material in the slurry layer 2. On the other hand, the setting of the gap can prevent the active material in the slurry layer 2 from extending to the junction of the slurry layer 2 and the insulating layer 4 and accumulating during the cold pressing process, thereby avoiding stress concentration at the junction, making the positive electrode sheet 10 not easy to break at the junction, and ensuring the yield rate of the positive electrode sheet 10.

[0041] A color layer 5 is provided between the slurry layer 2 and the insulating layer 4, and the color layer 5 is in contact with the corresponding ends of the slurry layer 2 and the insulating layer 4. The provision of the color layer 5 can improve the recognition rate of the edge of the positive electrode sheet 10, and when the positive electrode sheet 10 and the negative electrode sheet 20 are stacked by a CCD camera or the like, they can be accurately aligned, thereby improving the yield rate and efficiency of stacking.

[0042] The blank area 3 extends in the width direction, and the blank area 3 and the corresponding end of the insulating layer 4 are in contact in the width direction. That is, the blank area 3 divides the color layer 5 into two sections in the length direction, which can prevent the color layer 5 at the innermost curved portion 102 from falling off to other positions of the positive electrode sheet 10 during winding, or even falling off to the negative electrode sheet 20 and the separator 30 to affect the lamination.

[0043] In the present invention, the thickness of the slurry layer 2 and the thickness of the insulating layer 4 are both greater than the thickness of the color layer 5. On the one hand, the slurry flow and diffusion of the color layer 5 are prevented from affecting the clarity of the boundary between the color layer 5 and the slurry layer 2, and the clarity of the boundary between the color layer 5 and the insulating layer 4. On the other hand, the thickness of the color layer 5 is small, and when the positive electrode sheet 10 is wound, the slurry layer 2 can be closely attached to the separator 30, thereby improving the conduction of lithium ions.

[0044] On this basis, the thickness of the slurry layer 2 of the present invention is equal to the thickness of the insulating layer 4, thereby ensuring that the slurry layer 2 is in close contact with the diaphragm 30 and the insulating layer 4 is also in close contact with the diaphragm 30, thus playing a good insulating role.

[0045] The technical means disclosed in the solution of the utility model are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical solutions composed of any combination of the above technical features. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the utility model, and these improvements and modifications are also regarded as the protection scope of the utility model.

Claims

1. A wound positive electrode sheet, characterized in that: include: A positive electrode current collector (1) and a slurry layer (2) provided on at least one surface of the positive electrode current collector (1), wherein the surface of the positive electrode current collector (1) provided with the slurry layer (2) is also provided with a blank area (3), the blank area (3) and the slurry layer (2) are arranged adjacent to each other along the length direction, and the blank area (3) and the corresponding end portions of the slurry layer (2) are in contact; The positive electrode sheet (10) is spirally wound along the length direction to form a plurality of straight portions (101) and a plurality of curved portions (102) from the inside to the outside, and the innermost curved portion (102) is the blank area (3).

2. The wound positive electrode sheet according to claim 1, characterized in that: In the wound state, the distance between the two ends of the blank area (3) corresponding to the slurry layer (2) is greater than the thickness of the slurry layer (2).

3. The wound positive electrode sheet according to claim 2, characterized in that: In the wound state, the distance between the two ends of the blank area (3) corresponding to the slurry layer (2) is less than 1.5 times the thickness of the slurry layer (2).

4. The wound positive electrode sheet according to claim 1, characterized in that: The thickness of the positive electrode current collector is 12 μm±4 μm.

5. The wound positive electrode sheet according to claim 1, characterized in that: The surface of the positive electrode current collector (1) is also provided with an insulating layer (4) extending continuously along the length direction, and the insulating layer (4) is provided on both sides of the slurry layer (2) in the width direction.

6. The wound positive electrode sheet according to claim 5, characterized in that: A gap is provided between the slurry layer (2) and the insulating layer (4), a color layer (5) is provided between the slurry layer (2) and the insulating layer (4), and the color layer (5) is in contact with corresponding ends of the slurry layer (2) and the insulating layer (4).

7. The wound positive electrode sheet according to claim 5 or 6, characterized in that: The blank area (3) extends in the width direction, and the blank area (3) and corresponding ends of the insulating layer (4) are in contact with each other in the width direction.

8. The wound positive electrode sheet according to claim 6, characterized in that: The thickness of the slurry layer (2) and the thickness of the insulating layer (4) are both greater than the thickness of the color layer (5).

9. The wound positive electrode sheet according to claim 5 or 6, characterized in that: The thickness of the slurry layer (2) is equal to the thickness of the insulating layer (4).

10. A battery, characterized in that: include: A wound negative electrode sheet (20), a separator (30), and a wound positive electrode sheet (10) as claimed in any one of claims 1 to 9, wherein the separator (30) is arranged between the positive electrode sheet (10) and the negative electrode sheet (20).

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