Cathode sheet, roll core and lithium ion battery

Abstract

The utility model relates to lithium ion battery technical field discloses a kind of cathode sheet, roll core and lithium ion battery, cathode sheet includes pole piece body and ceramic coating, pole piece body has straight area and corner area, pole piece body has multiple coating areas in corner area, ceramic coating is equipped in each coating area, the size of each coating area along the length direction of pole piece body is D, 1mm≤D≤15mm, the liquid retention coefficient of corner area is R1, the liquid retention coefficient of straight area is R2, 1.05≤R1 / R2≤2.0.Ceramic coating increases the storage space of electrolyte in corner area, reduce the stress that corner area cathode sheet receives, can also adsorb electrolyte, to increase the liquid retention capacity of corner area;1mm≤D≤15mm, 1.05≤R1 / R2≤2.0, avoid that the coating width of ceramic coating is too small to cause insufficient liquid retention capacity, also avoid that width is too large to make cathode sheet, anode sheet contact insufficiently and worsen lithium precipitation.

Description

Technical Field

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

[0002] Lithium-ion batteries have outstanding advantages such as high energy density, long cycle life, low self-discharge, and no environmental pollution, and are widely used in consumer electronics, electric vehicles, and energy storage. The wound lithium-ion battery is a common structure. However, with the continuous increase in charging rates, interface problems in wound lithium-ion batteries, especially at the corners, have become particularly prominent.

[0003] A wound lithium-ion battery consists of flat and corner regions. The cathode, anode, and separator are wound together to form a core. The cathode, separator, and anode are tightly bonded together, with the separator located between the cathode and anode. The core is filled with electrolyte. After long-term cycling, the electrolyte is gradually consumed. Furthermore, the expansion of the electrodes during use can compress the electrolyte in the corner regions, leading to a reduction in electrolyte in these areas. This often results in abnormal conditions such as lithium plating at the corner interfaces of the cell in the later stages of cycling, affecting the lifespan of the wound lithium-ion battery. Utility Model Content

[0004] The purpose of this invention is to provide a cathode sheet to solve the problem of lithium deposition at the corner interface in the later stages of cycling in existing lithium-ion batteries; this invention also provides a winding core using the cathode sheet; this invention further provides a lithium-ion battery using the winding core.

[0005] To achieve the above objectives, this utility model provides a cathode sheet, comprising an electrode body and a ceramic coating. The electrode body has straight areas and corner areas alternately arranged along its length. The electrode body has multiple coating areas in the corner areas, and each coating area is spaced apart along the length of the electrode body. Each coating area is provided with the ceramic coating. The dimension of each coating area along the length of the electrode body is D, where 1mm≤D≤15mm. The liquid retention coefficient of the corner area is R1, and the liquid retention coefficient of the straight area is R2, where 1.05≤R1 / R2≤2.0.

[0006] Preferably, the porosity φ of the ceramic coating is 30% ≤ φ ≤ 80%.

[0007] Preferably, 45% ≤ φ ≤ 71%.

[0008] Preferably, the ceramic coating is distributed in a striped pattern within the coating area, and the distance between two adjacent striped ceramic coatings is S, where 1mm≤S≤2mm.

[0009] Preferably, the ceramic coating is distributed in a circular pattern within the coating area, and the diameter of the circular ceramic coating is d, where 1 mm ≤ d ≤ 3 mm.

[0010] Preferably, the ceramic coating is distributed in a grid pattern within the coating area, and the grid width of the ceramic coating is L, where 1mm ≤ L ≤ 2mm.

[0011] Preferably, the coating thickness of the ceramic coating in each of the coating areas is T, where 0.001mm ≤ T ≤ 0.01mm.

[0012] Preferably, the coating area is provided on one side of the corner area; or the coating area is provided on both sides of the corner area.

[0013] This utility model also provides a winding core, including an anode sheet, a cathode sheet, and a diaphragm, wherein the anode sheet, the cathode sheet, and the diaphragm are wound together, and the diaphragm is disposed between the anode sheet and the cathode sheet, and the cathode sheet is the cathode sheet described in any of the above technical solutions.

[0014] This utility model also provides a lithium-ion battery, including a casing and a core disposed within the casing, wherein the core is the core described in any of the above technical solutions.

[0015] Compared with the prior art, the present invention, which discloses a cathode sheet, a core, and a lithium-ion battery, has the following advantages: A coating area is provided in the corner region of the electrode body, and a ceramic coating is provided within this coating area. The ceramic coating has a thickness, which increases the space occupied in the corner region, thereby increasing the spacing between the cathode sheet and the separator, increasing the electrolyte storage space in the corner region, and reserving space for the expansion of the cell when the battery is heated. This reduces the stress on the cathode sheet in the corner region. Simultaneously, the ceramic coating has high porosity, allowing it to absorb electrolyte, thus increasing the electrolyte retention capacity in the corner region and reducing the risk of lithium plating. Furthermore, the size of the coating area (1mm≤D≤15mm) ensures that 1.05≤R1 / R2≤2.0, preventing insufficient electrolyte retention due to an excessively small coating width, and also preventing insufficient contact between the cathode and anode sheets due to an excessively large coating width, which could reduce the lithium-ion conduction rate and worsen lithium plating. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the cathode sheet of this utility model after it is coated with a ceramic coating on one side and wound into a core;

[0017] Figure 2 This is a schematic diagram of the structure of the cathode sheet of this utility model after it is coated with ceramic coating on both sides and wound into a core;

[0018] Figure 3These are schematic diagrams showing different shapes of the ceramic coating on the cathode sheet of this utility model.

[0019] In the figure, 1 is the cathode plate, 11 is the electrode body, 111 is the straight area, 112 is the corner area, 113 is the coating area, 12 is the ceramic coating, 2 is the anode plate, and 3 is the diaphragm. Detailed Implementation

[0020] The specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but are not intended to limit its scope.

[0021] A preferred embodiment of the cathode plate 1 of this utility model is as follows: Figures 1 to 3 As shown, the cathode plate 1 includes an electrode body 11 and a ceramic coating 12, with the ceramic coating 12 coated on the electrode body 11.

[0022] The electrode body 11 has multiple straight regions 111 and corner regions 112 alternately arranged along its length. The length direction of the electrode body 11 is consistent with the winding direction of the cathode sheet 1 when it is wound into a core. The cathode sheet 1 has multiple folds when it is wound into a core, and each fold has two straight regions 111 and two corner regions 112. The straight regions 111 and corner regions 112 of the electrode body 11 correspond to the straight interface and corner interface of the formed lithium-ion battery.

[0023] The electrode body 11 has multiple coated areas 113 in the corner area 112. These coated areas 113 are spaced apart along the length of the electrode body 11, with gaps between adjacent areas. Each coated area 113 is coated with a ceramic coating 12. Therefore, the area in the corner area 112 without the ceramic coating 12 is the area where the electrode body 11 is directly exposed. After the cathode sheet 1 is wound into a core, the area between the ceramic coatings 12 can be used to store electrolyte, providing electrolyte storage space and improving the electrolyte retention capacity of the corner area 112.

[0024] The ceramic coating 12 has a high porosity, which allows it to adsorb and store some electrolyte, ensuring ion transfer. In addition, after the ceramic coating 12 is applied to the coating area 113 of the corner region 112, it can increase the gap between the cathode plate 1 and the separator 3, increasing the electrolyte storage space and thus reducing the risk of lithium plating due to insufficient electrolyte wetting affecting ion transfer. Furthermore, the space increased by the ceramic coating 12 can reserve the expansion space required for the heating of the lithium-ion battery during use, reducing the stress on the cathode plate 1 in the corner region 112 and reducing the risk of lithium plating.

[0025] In this embodiment, the ceramic coating 12 is an insulating component. The ceramic coating 12 is composed of insulating materials and an adhesive. The insulating materials include alumina, boehmite, etc., and the adhesive is polyvinylidene fluoride (PVDF). After the insulating materials are bonded and formed by the adhesive, pores exist between the insulating materials, thus providing an electrolyte storage effect. In this embodiment, the mass percentage of the adhesive in the ceramic coating 12 is δ, where 1% ≤ δ ≤ 8%. The component in the ceramic coating 12 that adsorbs the electrolyte is the insulating material. If the mass fraction of the adhesive is less than 1%, the adhesion of the insulating material within the ceramic coating 12 will be poor. If the mass fraction of the adhesive is greater than 8%, the insulating material component will be too small, resulting in reduced porosity and a decreased ability to adsorb the electrolyte.

[0026] The dimension of each coating region 113 along the length of the electrode body 11 is defined as D, where D is the width of the coating region 113, 1mm≤D≤15mm. The liquid retention coefficient of the corner region 112 is R1, and the liquid retention coefficient of the straight region 111 is R2, 1.05≤R1 / R2≤2.0. The width of the coating region 113 affects the morphology and liquid retention capacity of the corner region 112. The width of the coating region 113 is the width of the entire region. Within the coating region 113, the ceramic coating 12 can be coated continuously or intermittently. D is the sum of the widths of the ceramic coating 12 and the electrode body 11 within this region.

[0027] The width D of the coating area 113 is between 1 and 15 mm because when the coating area 113 is too small (less than 1 mm), the coverage area of ​​the ceramic coating 12 is too small, resulting in insufficient improvement in liquid retention capacity and lithium plating. When the coating area 113 is too large (greater than 15 mm), the coverage area of ​​the ceramic coating 12 is too large, and it may even completely cover the corner area 112, causing the overall thickness of the wound core and the formed lithium-ion battery to exceed the standard, resulting in insufficient contact between the cathode plate 1 and the anode plate 2 in the corner area 112, leading to a worsening of the lithium plating phenomenon.

[0028] The electrolyte retention coefficient is the ratio of the electrolyte mass to the cell capacity, where the cell capacity is measured in mAh. Therefore, the electrolyte retention coefficient of the corner region 112 refers to the ratio of the electrolyte mass of the corner region 112 to the cell capacity of the corner region 112, and the electrolyte retention coefficient of the flat region 111 refers to the ratio of the electrolyte mass of the flat region 111 to the cell capacity of the flat region 111.

[0029] If R1 / R2 < 1.05, the electrolyte retention coefficient of the corner region 112 is low, which means it cannot absorb more electrolyte, leading to a risk of lithium plating. If 2.0 < R1 / R2, the electrolyte retention coefficient of the corner region 112 is too high. In this case, the volume of the ceramic coating 12 is too large, which may cause the overall battery thickness and / or width to exceed specifications. This would result in the cathode sheet 1 and the separator 3 not being able to make close contact over a large area, reducing the lithium-ion conduction rate and leading to lithium plating.

[0030] The cathode plate 1 has a coating area 113 in the corner area 112 of the electrode body 11. A ceramic coating 12 is disposed in the coating area 113. The ceramic coating 12 has a thickness, which increases the space occupied by it in the corner area 112, increases the spacing between the cathode plate 1 and the separator 3 in the corner area 112, increases the electrolyte storage space in the corner area 112, and also reserves space for the expansion of the cell when the battery is heated, reducing the stress on the cathode plate 1 in the corner area 112. At the same time, the ceramic coating 12 has a large porosity, which can adsorb electrolyte, thereby increasing the electrolyte retention capacity of the corner area 112 and reducing the risk of lithium plating. Meanwhile, the size of the coating area 113 is 1mm≤D≤15mm, which can ensure 1.05≤R1 / R2≤2.0, avoiding insufficient electrolyte retention capacity due to the coating width of the ceramic coating 12 being too small, and also avoiding insufficient contact between the cathode plate 1 and the anode plate 2 due to the width of the ceramic coating 12 being too large, which would reduce the lithium ion conduction rate and cause the deterioration of lithium plating.

[0031] Preferably, the porosity φ of the ceramic coating 12 is 30% ≤ φ ≤ 80%.

[0032] The ceramic coating 12 has high porosity, allowing it to adsorb and store a portion of the electrolyte. With a porosity of 30% ≤ φ ≤ 80%, the ceramic coating 12 can ensure ion transfer. Preferably, the porosity is 45% ≤ φ ≤ 71%.

[0033] Preferably, the ceramic coating 12 is distributed in a striped pattern within the coating area 113, and the distance between two adjacent striped ceramic coatings 12 is S, where 1mm≤S≤2mm.

[0034] like Figure 3 As shown, the ceramic coating 12 is distributed in multiple striped intervals. The ceramic coating 12 can increase the spacing between the cathode plate 1 and the diaphragm 3. At the same time, the intervals between the striped ceramic coatings 12 can also store electrolyte, improving the electrolyte retention capacity of the corner area 112. The distance S between two adjacent ceramic coatings 12 is between 1 and 2 mm. This distance matches the width of the coating area 113, ensuring the coverage of the ceramic coating 12 while avoiding the ceramic coating 12 being too dense.

[0035] Preferably, the ceramic coating 12 is distributed in a circular pattern within the coating area 113, and the diameter of the circular ceramic coating 12 is d, where 1 mm ≤ d ≤ 3 mm.

[0036] like Figure 3 As shown, the ceramic coatings 12 are distributed in circular intervals. The intervals between the circular ceramic coatings 12 can also store electrolyte, improving the electrolyte retention capacity of the corner area 112. The diameter d of the ceramic coatings 12 is 1 to 3 mm, which matches the width of the coating area 113. The ceramic coatings 12 absorb electrolyte while increasing the electrolyte storage space.

[0037] Preferably, the ceramic coating 12 is distributed in a grid pattern within the coating area 113, and the grid width of the grid-shaped ceramic coating 12 is L, where 1mm≤L≤2mm.

[0038] like Figure 3 As shown, the ceramic coating 12 is distributed in a grid pattern. The gaps between the grid-shaped ceramic coatings 12 can also store electrolyte, improving the electrolyte retention capacity of the corner area 112. The grid width L is between 1 and 2 mm, which matches the width of the coating area 113, thereby increasing the electrolyte storage space while utilizing the ceramic coating 12 to adsorb electrolyte.

[0039] Preferably, the coating thickness of the ceramic coating 12 in each coating area 113 is T, where 0.001mm≤T≤0.01mm.

[0040] The coating thickness T of the ceramic coating 12 is maintained between 0.001 and 0.01 mm. While improving the liquid retention capacity, it can prevent the thickness of the ceramic coating 12 in the corner area 112 from exceeding the specification, thus preventing the overall lithium-ion battery from exceeding the specification in the thickness or width direction.

[0041] Preferably, one side of the corner area 112 is provided with a coating area 113; or both sides of the corner area 112 are provided with coating areas 113.

[0042] like Figure 1 and Figure 2 As shown, a ceramic coating 12 may be applied to one side or both sides of the corner area 112 as needed to ensure that the distance between the cathode plate 1 and the anode plate 2 is within a suitable range, which helps to prevent lithium deposition in the corner area 112.

[0043] In some preferred embodiments, the electrode body 11 of the cathode sheet 1 is made of pure carbon material. After the ceramic coating 12 is coated on the coating area 113 of the corner area 112, the parameters such as the mass ratio δ of the adhesive, the pore size of the ceramic coating 12, the thickness T of the ceramic coating 12, and the ratio of the liquid retention coefficient R1 of the corner area 112 to the liquid retention coefficient R2 of the straight area 111 are shown in Table 1.

[0044]

[0045] Table 1

[0046] In some preferred embodiments, the electrode body 11 of the cathode sheet 1 is made of 10% Si-doped negative electrode material. After the ceramic coating 12 is coated on the coating area 113 of the corner area 112, the parameters such as the mass ratio δ of the adhesive, the pore size of the ceramic coating 12, the thickness T of the ceramic coating 12, and the ratio of the liquid retention coefficient R1 of the corner area 112 to the liquid retention coefficient R2 of the straight area 111 are shown in Table 2.

[0047]

[0048] Table 2

[0049] This utility model also provides a preferred embodiment of a winding core, including an anode sheet 2, a cathode sheet 1, and a diaphragm 3. The anode sheet 2, the cathode sheet 1, and the diaphragm 3 are wound together. The diaphragm 3 is disposed between the anode sheet 2 and the cathode sheet 1. The specific structure of the cathode sheet 1 is the same as that of the cathode sheet 1 in any of the above embodiments, and will not be described again here.

[0050] This utility model also provides a preferred embodiment of a lithium-ion battery, including a casing and a core disposed within the casing. The structure of the core is the same as that of the core in any of the above embodiments, and will not be described again here.

[0051] In summary, this utility model embodiment provides a cathode sheet, a core, and a lithium-ion battery. A coating area is provided in the corner region of the electrode body, and a ceramic coating is applied within this coating area. The ceramic coating has a thickness, which increases the space occupied in the corner region, thereby increasing the spacing between the cathode sheet and the separator, increasing the electrolyte storage space in the corner region, and also reserving space for the cell expansion when the battery is heated, reducing the stress on the cathode sheet in the corner region. Simultaneously, the ceramic coating has high porosity, allowing it to absorb electrolyte, thus increasing the electrolyte retention capacity in the corner region and reducing the risk of lithium plating. Furthermore, the size of the coating area (1mm≤D≤15mm) ensures 1.05≤R1 / R2≤2.0, preventing insufficient electrolyte retention due to an excessively small coating width, and also preventing insufficient contact between the cathode and anode sheets due to an excessively large coating width, which could reduce the lithium-ion conduction rate and worsen lithium plating.

[0052] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present utility model, and these improvements and substitutions should also be considered within the protection scope of the present utility model.

Claims

1. A cathode plate, characterized in that, The electrode body (11) includes an electrode body (11) and a ceramic coating (12). The electrode body (11) has a straight area (111) and a corner area (112) that are alternately arranged along the length direction. The electrode body (11) has a plurality of coating areas (113) in the corner area (112). Each coating area (113) is spaced apart along the length direction of the electrode body (11). Each coating area (113) is provided with the ceramic coating (12). The dimension of each coating area (113) along the length direction of the electrode body (11) is D, where 1 mm ≤ D ≤ 15 mm. The liquid retention coefficient of the corner area (112) is R1, and the liquid retention coefficient of the straight area (111) is R2, where 1.05 ≤ R1 / R2 ≤ 2.

0.

2. The cathode sheet according to claim 1, characterized in that, The porosity of the ceramic coating (12) is φ, 30% ≤ φ ≤ 80%.

3. The cathode sheet according to claim 2, characterized in that, 45% ≤ φ ≤ 71%.

4. The cathode sheet according to claim 1, characterized in that, The ceramic coating (12) is distributed in a striped pattern within the coating area (113), and the distance between two adjacent striped ceramic coatings (12) is S, where 1mm≤S≤2mm.

5. The cathode sheet according to claim 1, characterized in that, The ceramic coating (12) is distributed in a circular interval within the coating area (113), and the diameter of the circular ceramic coating (12) is d, 1mm≤d≤3mm.

6. The cathode sheet according to claim 1, characterized in that, The ceramic coating (12) is distributed in a grid pattern within the coating area (113), and the grid width of the ceramic coating (12) is L, where 1mm ≤ L ≤ 2mm.

7. The cathode sheet according to any one of claims 1-6, characterized in that, The coating thickness of the ceramic coating (12) in each of the coating areas (113) is T, where 0.001mm≤T≤0.01mm.

8. The cathode sheet according to any one of claims 1-6, characterized in that, The corner area (112) has a coating area (113) on one side; or the corner area (112) has a coating area (113) on both sides.

9. A type of winding core, characterized in that, It includes an anode plate (2), a cathode plate (1) and a diaphragm (3), wherein the anode plate (2), the cathode plate (1) and the diaphragm (3) are wound together, and the diaphragm (3) is disposed between the anode plate (2) and the cathode plate (1), wherein the cathode plate (1) is the cathode plate (1) according to any one of claims 1-8.

10. A lithium-ion battery, characterized in that, It includes a housing and a core disposed within the housing, the core being the core as described in claim 9.

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