A positive electrode sheet and a battery cell

Abstract

The utility model discloses a kind of positive plate and battery core.The positive plate of the utility model includes first current collector and first active material layer.First current collector includes multiple first normal area and first corner area arranged alternately, and the roughness of first corner area is less than the roughness of first normal area.First active material layer is arranged on the surface of first current collector, and the thickness of first active material layer at first corner area is less than the thickness of first active material layer at first normal area.The roughness of the first corner area of first current collector is less than the roughness of first normal area, so it can be attached less first active material layer, and positive plate will carry out delithiation when discharging, due to the active material layer reduction of its corner area, delithiation speed slows down, so as to effectively improve the lithium precipitation phenomenon at corner.

Description

Technical Field

[0001] This utility model relates to the field of battery manufacturing technology, specifically to a positive electrode sheet and a battery cell. Background Technology

[0002] In the field of lithium batteries, lithium plating in battery cells has become a key issue restricting battery life and safety. Due to the high stress in the corner areas of the battery cell, the electrode contact in these areas is poor, resulting in insufficient lithium intercalation space and a significant increase in lithium-ion transport resistance, thus making the corner areas more prone to lithium plating. Utility Model Content

[0003] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a positive electrode sheet that can effectively improve the lithium deposition phenomenon at corners.

[0004] This utility model also proposes a battery cell having the above-mentioned positive electrode plate.

[0005] A positive electrode according to a first aspect embodiment of the present invention includes a first current collector and a first active material layer. The first current collector includes a plurality of alternately arranged first ordinary regions and first corner regions, wherein the roughness of the first corner regions is less than the roughness of the first ordinary regions. The first active material layer is disposed on the surface of the first current collector, wherein the thickness of the first active material layer at the first corner regions is less than the thickness of the first active material layer at the first ordinary regions.

[0006] The positive electrode sheet according to the present invention has at least the following beneficial effects: the roughness of the first corner region of the first current collector is less than that of the first ordinary region, so less first active material layer can be attached. When the positive electrode sheet is discharged, lithium is delithiated. Since the active material layer in its corner region is reduced, the delithiation speed is slowed down, thereby effectively improving the lithium plating phenomenon at the corner.

[0007] According to some embodiments of the present invention, the first ordinary area is directly connected to the first corner area, or the positive electrode sheet further includes a first processing area, the first processing area and the first ordinary area are on the same plane, and the two ends of the first processing area are respectively connected to the first ordinary area and the first corner area.

[0008] According to some embodiments of the present invention, the dyne value of the first corner area is A, the dyne value of the first ordinary area is B, and 0 < A ≤ 0.7B.

[0009] According to some embodiments of this utility model, (B-A)≥2mN / m.

[0010] According to some embodiments of the present invention, 2.6mN / m≤(B-A)≤4mN / m.

[0011] According to some embodiments of the present invention, the contact angle of the surface of the first corner area is C, the contact angle of the surface of the first ordinary area is D, and 30°≤(C-D)≤80°.

[0012] According to some embodiments of this utility model, 40.3°≤(C-D)≤60.6°.

[0013] According to some embodiments of the present invention, the first current collector has a first surface and a second surface arranged opposite to each other, and both the first surface and the second surface include a plurality of alternating first ordinary areas and first corner areas.

[0014] The battery cell according to the second aspect embodiment of the present invention includes the positive electrode sheet as described in any one of the first aspect embodiments.

[0015] The battery cell according to the present invention has at least the following beneficial effects: the roughness of the first corner region of the first current collector is less than the roughness of the first ordinary region, so less first active material layer can be attached. When the positive electrode is discharged, lithium is delithiated. Since the active material layer in its corner region is reduced, the delithiation speed is slowed down, thereby effectively improving the lithium plating phenomenon at the corner. The battery cell using this positive electrode can also effectively improve the lithium plating phenomenon of the battery cell.

[0016] According to some embodiments of the present invention, the negative electrode includes a second current collector and a second active material layer. The second current collector includes a plurality of alternately arranged second normal regions and second corner regions, wherein the roughness of the second corner regions is greater than the roughness of the second normal regions. The second active material layer is disposed on the surface of the second current collector, and the thickness of the second active material layer at the second corner region is greater than the thickness of the second active material layer at the second normal region.

[0017] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0019] Figure 1 This is a schematic diagram of the battery cell structure in one embodiment of the present invention;

[0020] Figure 2 This is a flowchart of the method for manufacturing the positive electrode sheet according to this utility model.

[0021] Reference numerals: Cell 100, Positive electrode 101, Negative electrode 102, First current collector 103, First corner region 104, First ordinary region 105, First processing region 106, First active material layer 107, Second current collector 108, Second corner region 109, Second ordinary region 110, Second active material layer 111. Detailed Implementation

[0022] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0023] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0024] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0025] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0026] In the description of this utility model, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0027] refer to Figure 1According to a first aspect embodiment of the present invention, the positive electrode 101 includes a first current collector 103 and a first active material layer 107. The first current collector 103 includes a plurality of alternately arranged first ordinary regions 105 and first corner regions 104, wherein the roughness of the first corner regions 104 is less than the roughness of the first ordinary regions 105. The first active material layer 107 is disposed on the surface of the first current collector 103, and the thickness of the first active material layer 107 at the first corner regions 104 is less than the thickness of the first active material layer 107 at the first ordinary regions 105. Since the roughness of the first corner regions 104 of the first current collector 103 is less than the roughness of the first ordinary regions 105, less first active material layer 107 can adhere to them. When the positive electrode 101 discharges, lithium deposition occurs. Due to the reduced active material layer in the corner regions, the lithium deposition rate is slowed down, thereby effectively improving the lithium plating phenomenon at the corners.

[0028] It should be noted that the roughness mentioned in this article does not refer entirely to the roughness of the object's surface, but rather to a description of the surface's adhesion. This can be specifically reflected by the dyne value and contact angle described below. The roughness of the first corner region 104 is less than that of the first ordinary region 105, that is, the dyne value of the first corner region 104 is less than that of the first ordinary region 105. The first corner region 104 has low surface energy and poor adhesion, making it more difficult for the first active material layer 107 to adhere to the first corner region 104. As a result, the thickness of the first active material layer 107 on the surface of the first corner region 104 is less than the thickness of the first active material layer 107 on the surface of the first ordinary region 105. Similarly, this can also be reflected by the size of the contact angle. The contact angle is the angle formed at the three-phase contact point when the droplet reaches equilibrium on the solid surface. The roughness of the first corner region 104 is less than that of the first ordinary region 105, that is, the contact angle at the first corner region 104 is greater than that at the first ordinary region 105. Therefore, the wettability of the first corner region 104 is lower than that of the first ordinary region 105. This also means that the first active material layer 107 is more difficult to adhere to the first corner region 104, thereby achieving a thickness of the first active material layer 107 on the surface of the first corner region 104 that is less than that of the first active material layer 107 in the first ordinary region 105, thus improving the technical effect of corner lithium plating.

[0029] refer to Figure 1 In some embodiments of this utility model, the first ordinary region 105 and the first corner region 104 are directly connected; alternatively, the positive electrode 101 further includes a first processing region 106, which is on the same plane as the first ordinary region 105, and its two ends are respectively connected to the first ordinary region 105 and the first corner region 104. Specifically, as shown... Figure 1 As shown in the upper section of the first local current collector 103, the first ordinary area 105 is directly connected to the first corner area 104, as follows. Figure 1As shown in the lower section of the first current collector 103, the first corner region 104 and the first ordinary region 105 are connected by the first processing region 106. The first processing region 106 and the first corner region 104 undergo essentially the same processing steps, and their surface physical properties are identical. Both the first processing region 106 and the first ordinary region 105 are essentially straight sections in the current collector; the difference lies in the fact that the first processing region 106 undergoes the same processing steps as the first corner region 104, thus creating a difference in physical properties between them. The purpose of setting up the first processing region 106 is to add redundancy when processing the first corner region 104, thereby ensuring that the first corner region 104 can be completely processed, ensuring that the dyne value and contact angle of the entire first corner region 104 change, so that the thickness of the first active material layer 107 in the first corner region 104 is uniform. Figure 1 The reduction shown indicates that the effect of stabilizing and improving lithium plating at corners is achieved.

[0030] In some embodiments of this invention, the dyne value of the first corner region 104 is A, and the dyne value of the first ordinary region 105 is B, where 0 < A ≤ 0.7B. The dyne value describes the surface tension coefficient, i.e., the interaction force per unit length between adjacent portions of a liquid or solid surface. It directly reflects the surface energy of a material and affects properties such as wettability and adhesion. A higher dyne value indicates a higher surface energy, making it easier for adhesives or coatings to wet and adhere firmly; a lower dyne value indicates a lower surface energy, making adhesion difficult. Therefore, a lower dyne value for the first corner region 104 compared to the first ordinary region 105 makes it more difficult for the first active material layer 107 to adhere to the surface of the first corner region 104. Thus, a lower dyne value reduces the content of the active material layer in the first corner region 104, improving lithium plating. Specifically, the dyne value of the first corner region 104 should be reduced by at least 30% compared to the first ordinary region 105, i.e., A≤0.7B. When A is greater than 0.7B, the reduction in dyne value is small, the surface energy change is low, and thus the effect of reducing the thickness of the first active material layer 107 is also poor, and the effect of improving lithium plating is not obvious.

[0031] In some embodiments of this invention, (B-A) ≥ 2 mN / m, preferably 2.6 mN / m ≤ (B-A) ≤ 4 mN / m. This provides a more specific definition of the reduction in dyne value, meaning the dyne value of the first corner region 104 must be reduced by at least 2.6 mN / m compared to the dyne value of the first ordinary region 105, specifically by 2.6 mN / m, 2.8 mN / m, 3.0 mN / m, etc. If the reduction is still less than 2.6 mN / m, it will also result in a lower surface energy change, thus reducing the thickness of the first active material layer 107 less effectively, and the improvement in lithium plating effect will be insignificant.

[0032] In some embodiments of this invention, the contact angle of the surface of the first corner region 104 is C, and the contact angle of the surface of the first ordinary region 105 is D, where 30°≤(C-D)≤80°, preferably 40.3°≤(C-D)≤60.6°. The contact angle of an object's surface is a key parameter describing the wetting behavior of a liquid on a solid surface; specifically, it refers to the angle between the tangent of the gas-liquid interface and the tangent of the solid-liquid interface at the gas-liquid-solid three-phase contact point. Its core significance lies in reflecting the degree of wetting of the solid surface by the size of the angle, thereby assessing the hydrophilicity or hydrophobicity of the material. Specifically, the larger the contact angle, the less easily the solid surface is wetted. In this embodiment of the invention, the contact angle of the surface of the first corner region 104 is larger than that of the surface of the first ordinary region 105, making it less likely to be wetted by the first active material layer 107. During manufacturing, the content of the first active material layer 107 per unit area in the first corner region 104 is lower, thereby reducing the lithium removal rate and improving lithium plating. The contact angle of the surface of the first ordinary region 105 needs to be controlled within a suitable range, namely 40.3°≤(C-D)≤60.6°. Specifically, the contact angle increase value can be 40.3°, 50.2°, 60.6°, etc. When the contact angle increase value is less than 40.3°, the change in surface wettability will also be small, the effect of reducing the thickness of the first active material layer 107 will be poor, and the effect of improving lithium plating will not be obvious. When the contact angle increase value is greater than 60.6°, the wettability of the surface of the first corner region 104 is too low, and only a small amount of the first active material layer 107 can be attached, that is, the content of positive electrode active material is reduced too much. The active material is the main body of energy storage, which is not conducive to the cell 100 maintaining a sufficiently high energy density.

[0033] refer to Figure 1 In some embodiments of this utility model, the first current collector 103 has a first surface and a second surface arranged opposite to each other. Both the first surface and the second surface include multiple alternately arranged first ordinary regions 105 and first corner regions 104. Processing both sides of the positive electrode 101 allows it to... Figure 1 The effect of forming a lowering of the first active material layer 107 on both sides is shown, thereby better reducing the detachment rate and improving the lithium plating phenomenon.

[0034] The battery cell 100 according to a second aspect embodiment of the present invention includes a positive electrode 101 as described in any of the first aspect embodiments. The roughness of the first corner region 104 of the first current collector 103 is less than the roughness of the first ordinary region 105, thus allowing for the adhesion of less first active material layer 107. During discharge, the positive electrode 101 undergoes lithium removal. Due to the reduced active material layer in its corner region, the lithium removal rate is slowed, effectively improving the lithium plating phenomenon at the corner. The battery cell 100 using this positive electrode 101 can also effectively improve the lithium plating phenomenon of the battery cell 100.

[0035] refer to Figure 1 In some embodiments of this utility model, the negative electrode 102 includes a second current collector 108 and a second active material layer 111. The second current collector 108 includes a plurality of alternately arranged second ordinary regions 110 and second corner regions 109, the roughness of the second corner regions 109 being greater than the roughness of the second ordinary regions 110. The second active material layer 111 is disposed on the surface of the second current collector 108, and the thickness of the second active material layer 111 at the second corner regions 109 is greater than the thickness of the second active material layer 111 at the second ordinary regions 110. The roughness here, as well as the roughness at the positive electrode 101, refers to changing the physical properties of the current collector surface, causing changes in the adhesion and wetting ability of the active material at different locations. Specifically, this can be reflected in changes in dyne value or contact angle. Due to changes in dyne value and contact angle, when a slurry containing active material is coated on the surface of the current collector, the surface with a higher dyne value and a smaller contact angle is less likely to be wetted by the active material, thus resulting in changes in content and thickness. Specifically, for the negative electrode 102, the dyne value of the second corner region 109 is reduced and the contact angle is increased, making it easier for the second active material layer 111 to adhere. After uniformly coating with a slurry containing the second active material, the final thickness of the second active material layer 111 in the second corner region 109 will be greater than the thickness of the second active material layer 111 in the second ordinary region 110, thereby improving the lithium intercalation capability at the corner of the negative electrode 102 and improving the lithium plating phenomenon. The change in thickness is essentially the change in the content of the second active material layer 111 per unit area.

[0036] refer to Figure 1 and Figure 2 In some embodiments of this utility model, the manufacturing method of the positive electrode 101 includes the following steps:

[0037] A first current collector 103 is provided, comprising alternating first normal regions 105 and first corner regions 104. The surface of the first current collector 103 is treated to make the roughness of the first corner region 104 less than that of the first normal region 105. A slurry containing a first active material is coated on the surface of the first current collector 103 to form a first active material layer 107, the thickness of the first active material layer 107 at the first corner region 104 being less than that at the first normal region 105. By changing the surface roughness of the first current collector 103 through surface treatment, the roughness of the first corner region 104 of the first current collector 103 can be made less than that of the first normal region 105, thus allowing for the adhesion of a smaller first active material layer 107. From a macroscopic perspective, this results in a smaller thickness and a smaller amount of first active material. Since the positive electrode 101 undergoes lithium delithiation during discharge, the reduced active material layer in the corner region slows down the lithium delithiation rate, thereby effectively improving the lithium plating phenomenon at the corner.

[0038] When manufacturing the positive electrode 101, the dyne value of the first corner region 104 is increased and the contact angle is reduced, making it less likely for the first active material layer 107 to adhere. As a result, after uniformly coating with a slurry containing the first active material, the final thickness of the first active material layer 107 in the first corner region 104 will be less than the thickness of the first active material layer 107 in the first ordinary region 105. This reduces the lithium removal rate at the corner of the positive electrode 101 and improves the lithium plating phenomenon. The change in thickness is essentially a change in the content of the first active material layer 107 per unit area.

[0039] refer to Figure 2In some embodiments of this utility model, the surface treatment of the first current collector 103 includes: applying adhesive tape to the surface of the first current collector 103, with the adhesive tape covering the first corner area 104; subjecting the surface of the first current collector 103 to corona treatment; and then peeling off the adhesive tape after the corona treatment. The corona treatment of the first current collector 103 involves generating high-energy plasma through high-frequency, high-voltage discharge. These particles impact the material surface at high speed, causing the surface molecular chemical bonds to break and degrade. Furthermore, the corona treatment significantly increases the surface energy of the material, enhancing the surface's affinity for polar substances and thus increasing surface roughness to some extent. The higher surface energy promotes more uniform spread of liquid and penetration into microscopic depressions, thereby increasing its surface energy. The higher surface energy after corona treatment allows for better bonding with coating materials. Moreover, corona treatment can typically be performed on a production line without requiring additional complex equipment or prolonged downtime. Therefore, by applying adhesive tape to the surface of the first corner region 104, it can be prevented from being corona-treated. This results in the surface energy of the corona-treated first ordinary region 105 being higher and the contact angle being smaller than that of the uncorona-treated first corner region 104, making it easier to combine with the first active material layer 107. The adhesive application and corona treatment processes are simple and controllable. This can efficiently create a difference in surface properties between the first corner region 104 and the first ordinary region 105, ultimately resulting in a lower content of the first active material layer 107 in the first corner region 104, thus improving the corner lithium plating phenomenon.

[0040] In some embodiments of this utility model, the surface energy of the first ordinary region 105 can be changed by applying an additional coating or by spraying with chemical reagents, so that the surface energy of the first ordinary region 105 is higher than that of the first corner region 104.

[0041] In some embodiments of this invention, the power of the corona treatment is P, and the corona treatment time is T, where 3kW≤P≤4.5kW and 1s≤T≤3s. The power and time of the corona treatment must also be controlled within a suitable range. A longer corona treatment time or a higher power will result in a higher surface energy of the current collector surface, thus improving its wettability. Specifically, the corona power can be 3kW, 3.5kW, 4.5kW, etc., and the corona treatment time can be 1s, 2s, 3s, etc. When the corona treatment time or power is too low, the corona effect is not obvious, and the change in surface wettability of the first ordinary region 105 compared to the first corner region 104 is small, resulting in an insignificant improvement in lithium plating. When the corona power or time is too high, it may damage the surface of the first current collector 103, or cause too much first active material to adhere to the first ordinary region 105, while the first corner region 104 has relatively less first active material, which is detrimental to the energy density requirements of the battery.

[0042] Specifically, regarding the manufacturing process of the positive electrode 101, after corona treatment of the first current collector 103, the changes in its surface dyne value, contact angle, and active material layer content, as well as the improvement in lithium plating effect, are shown in the following table examples.

[0043]

[0044] In some embodiments of this utility model, the manufacturing method of the negative electrode 102 includes the following steps:

[0045] A second current collector 108 is provided, comprising alternating second normal regions 110 and second corner regions 109. The surface of the second current collector 108 is treated to make the roughness of the second corner region 109 greater than that of the second normal region 110. A slurry containing a second active material is coated on the surface of the second current collector 108 to form a second active material layer 111, the thickness of the second active material layer 111 at the second corner region 109 being greater than its thickness at the second normal region 110. By surface-treating the second current collector 108 of the negative electrode 102 to make the roughness of the second corner region 109 greater than that of the second normal region 110, more of the second active material layer 111 can be attached. Since the negative electrode 102 undergoes lithium intercalation during discharge, more active material can enhance the lithium intercalation capability at the corner of the negative electrode 102, thereby effectively improving the lithium plating phenomenon at the corner. The roughness mentioned in this paragraph has the same meaning as above.

[0046] Specifically, in some embodiments of this utility model, corona treatment can also be used in the manufacturing process of the negative electrode 102. The difference between the negative electrode 102 and the positive electrode 101 is that, since the length of the corner area is generally smaller than the length of the ordinary section, the second corner area 109 on the second current collector 108 of the negative electrode 102 can be directly corona treated without applying adhesive to the ordinary area. This increases the surface energy of the second corner area 109 and reduces the contact angle, thereby achieving better wettability and allowing more of the second active material layer 111 to adhere. During the discharge process, the negative electrode 102 will undergo lithium intercalation. More active material can enhance the lithium intercalation capability at the corner of the negative electrode 102, thereby effectively improving the lithium plating phenomenon at the corner. Furthermore, the dyne value of the second corner region 109 should be increased by at least 2.4 mN / m compared to the second ordinary region 110, while the contact angle should be reduced between 38.4° and 58.5°. This can meet the dual requirements of improving corner lithium plating and ensuring the energy density of the cell 100.

[0047] Regarding the manufacturing process of the negative electrode 102, after corona treatment of the second corner region 109 of the second current collector 108, the changes in the dyne value, contact angle, and content of the active material layer on its surface, as well as the improvement of lithium plating effect, are shown in the following table of examples.

[0048]

[0049] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A positive electrode plate, characterized in that, include: The first current collector includes a plurality of alternating first normal regions and first corner regions, wherein the roughness of the first corner region is less than that of the first normal region; A first active material layer is disposed on the surface of the first current collector, and the thickness of the first active material layer at the first corner area is less than the thickness of the first active material layer at the first ordinary area.

2. The positive electrode sheet according to claim 1, characterized in that, The first ordinary area is directly connected to the first corner area, or the positive electrode sheet further includes a first processing area, which is on the same plane as the first ordinary area, and the two ends of the first processing area are respectively connected to the first ordinary area and the first corner area.

3. The positive electrode sheet according to claim 1, characterized in that, The dyne value of the first corner zone is A, the dyne value of the first ordinary zone is B, and 0 < A ≤ 0.7B.

4. The positive electrode sheet according to claim 3, characterized in that, (B-A)≥2mN / m.

5. The positive electrode sheet according to claim 4, characterized in that, 2.6mN / m≤(B-A)≤4mN / m.

6. The positive electrode sheet according to claim 1, characterized in that, The contact angle of the surface of the first corner area is C, and the contact angle of the surface of the first ordinary area is D, where 30°≤(C-D)≤80°.

7. The positive electrode sheet according to claim 6, characterized in that, 40.3°≤(C-D)≤60.6°.

8. The positive electrode sheet according to claim 1, characterized in that, The first current collector has a first surface and a second surface arranged opposite to each other, and both the first surface and the second surface include a plurality of alternating first normal areas and first corner areas.

9. A battery cell, characterized in that, include: The negative electrode and the positive electrode as described in any one of claims 1-8.

10. The battery cell according to claim 9, characterized in that, The negative electrode includes: The second current collector includes a plurality of alternately arranged second normal areas and second corner areas, wherein the roughness of the second corner area is greater than that of the second normal area; A second active material layer is disposed on the surface of the second current collector, and the thickness of the second active material layer at the second corner area is greater than the thickness of the second active material layer at the second normal area.

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