Pole piece semi-finished product structure and pole piece

Abstract

The utility model discloses a pole piece semi-finished product structure and a pole piece, the pole piece semi-finished product structure comprises a current collector, the two sides of the current collector are provided with active substance coatings, each active substance coating comprises a main body region and a thinned region, the main body region is arranged in the middle region of the current collector, and the thinned region is arranged in the edge region of the current collector; and the thickness of the thinned area is smaller than that of the main body area. The pole piece is processed and formed by the pole piece semi-finished product structure. The edge area of the pole piece semi-finished product structure is thinned, so that the edge of the pole piece is smoother, and the phenomenon of edge bulge is not easy to occur in the rolling process; and meanwhile, the thinned area can provide a positioning effect for subsequent laser to remove active substances.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a pole piece semi-finished product structure and a pole piece. Background Art

[0002] At present, in the production and manufacturing of electrode sheets, due to the existence of surface tension of the slurry, during the drying process after the electrode coating process, the slurry will migrate to the edge of the electrode sheet, resulting in the electrode sheet being thin in the middle and thick at the edges, which in turn leads to the problem of edge bulging and scrapping during the winding process of the electrode sheet.

[0003] To address this issue, the usual measure is to thin the thick edges of the electrode after coating and drying to adjust the thickness distribution of the electrode. However, this treatment method may cause new problems after the battery cell is stacked or wound, such as insufficient active material in the thinned area of ​​the electrode edge, resulting in a low NP ratio (i.e., the ratio of negative electrode active material to positive electrode active material), blackening of the edge, lithium deposition, etc., which in turn reduces the cycle performance of the battery cell. Therefore, it is also necessary to remove the thinned area of ​​the electrode in the later stage of the electrode manufacturing process.

[0004] However, in the process of using laser technology to remove active materials in the thinned area in the later stage of the process, due to the lack of precise positioning, the laser beam may accidentally irradiate the active material in the middle area of ​​the pole piece, causing these materials that should not be removed to be accidentally damaged. Utility Model Content

[0005] In order to overcome at least one of the defects described in the above-mentioned prior art, one of the purposes of the present application is to provide a semi-finished electrode structure, which can prevent the edge bulging phenomenon during the winding process of the electrode by setting a thinning zone in the edge area of ​​the electrode, and the thinning zone can play a positioning and guiding role in the process of laser removal of active substances.

[0006] The second purpose of this application is to provide a pole piece, which is formed by processing a pole piece semi-finished product structure, which can prevent the edge area of ​​the pole piece from having a small NP ratio, blackening of the edge, lithium deposition, etc. due to insufficient active material.

[0007] One of the technical solutions adopted by this application to solve the problem is:

[0008] A semi-finished electrode structure includes a current collector, with active material coatings provided on both sides of the current collector. The active material coatings include a main area and a thinning area. The main area is arranged in the middle area of ​​the current collector, and the thinning area is arranged in the edge area of ​​the current collector; the thickness of the thinning area is less than the thickness of the main area.

[0009] As a preferred technical solution of the present application, the width of the active material coating is L, the width of the thinning area is a, and the value of a is in the range of 0.1%*L≤a≤20%*L.

[0010] As a preferred technical solution of the present application, the thickness of the main body area is uniform, and the cross section of the main body area is rectangular.

[0011] As a preferred technical solution of the present application, the thickness of the thinning area is uniform, and the cross section of the thinning area is rectangular.

[0012] As a preferred technical solution of the present application, the thickness of the thinning area gradually decreases from the side close to the main body area to the side away from the main body area, and the cross section of the thinning area is triangular.

[0013] As a preferred technical solution of the present application, the thinning area includes a first thinning area and a second thinning area, and the first thinning area connects the second thinning area and the main body area; the thickness of the first thinning area is uniform, the thickness of the second thinning area gradually decreases from the side close to the first thinning area to the side away from the first thinning area, and the cross section of the thinning area is trapezoidal.

[0014] As a preferred technical solution of the present application, the two sides of the main body area are connected with the thinning area.

[0015] As a preferred technical solution of the present application, the cross section shapes of the thinning areas on the two sides of the main body area are the same or different.

[0016] As a preferred technical solution of the present application, there is a current collector bare area between the periphery of the thinning area and the periphery of the current collector.

[0017] The second technical solution adopted by the present application to solve the problem is:

[0018] An electrode sheet is processed and formed in the electrode sheet semi-finished product structure as described above.

[0019] In summary, the electrode sheet semi-finished product structure and the electrode sheet provided by the present application have the following technical effects:

[0020] 1) The electrode sheet semi-finished product structure of the present application sets a thinning area in the edge area of the electrode sheet, so that the thickness of the electrode sheet edge is closer to the center area, thereby forming a more uniform thickness distribution on the entire electrode sheet surface; this helps to maintain the overall flatness of the electrode sheet during the winding process and reduces the bulging phenomenon caused by uneven thickness.

[0021] 2) The setting of the thinning area can provide positioning and guiding for the subsequent process of laser removing the active material on the thinning area.

[0022] 3) The electrode of the present application is formed by processing a semi-finished electrode structure, and the active material on the edge area of ​​the electrode is completely removed, which can prevent the edge area of ​​the electrode from having a small NP ratio, blackening of the edge, lithium precipitation, etc. due to insufficient active material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of a first cross-sectional structure of a thinning area according to an embodiment of the present application;

[0024] Figure 2 A schematic diagram of a second cross-sectional structure of the skived area according to an embodiment of the present application;

[0025] Figure 3 This is a schematic diagram of a third cross-sectional structure of the thinning area according to an embodiment of the present application;

[0026] Figure 4 This is a schematic structural diagram of the electrode according to an embodiment of the present application.

[0027] The meanings of the reference numerals are as follows:

[0028] 1. Current collector; 2. Active material coating; 21. Main body area; 22. Thinning area. DETAILED DESCRIPTION

[0029] For better understanding and implementation, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0030] In the description of this application, it should be noted that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting this application.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0032] Example 1

[0033] See Figures 1 to 3The application discloses a pole piece semi-finished product structure, which comprises a current collector 1, and active material coating layers 2 are arranged on two sides of the current collector 1. Specifically, the active material coating layers 2 comprise main body areas 21 and thinning areas 22, and the main body areas 21 are arranged in the middle area of the current collector 1, and the thinning areas 22 are arranged in the edge area of the current collector 1. The thickness of the thinning areas 22 is less than the thickness of the main body areas 21.

[0034] It should be noted that the current collector 1 is usually made of materials with excellent electrical conductivity and stable chemical properties, such as copper foil (negative electrode) and aluminum foil (positive electrode), as a carrier of electric current. The current collector 1 has large faces on two sides along the thickness direction of the current collector 1, and the large faces on the two sides are oppositely arranged. The active material coating layers 2 are coated on the large faces.

[0035] On the basis of the structure, during the manufacturing of the pole piece, slurry containing active materials, conductive agents, binders and the like can be uniformly coated on the large faces on the two sides of the current collector 1. Then, the coated pole piece is subjected to drying treatment, so that the solvent in the slurry volatilizes, the binder solidifies, and stable active material coating layers 2 are formed.

[0036] During the process, due to the surface tension of the slurry, part of the slurry may migrate to the edge of the pole piece, so that the thickness of the edge area of the active material coating layers 2 increases. Thus, the problem of edge bulging of the pole piece is prone to occur during the winding process of the pole piece, and the pole piece is scrapped. Therefore, the dried pole piece can be subjected to treatment by a thinning device, so that the thick edge area of the edge is thinned to form the thinning areas 22, and the thickness of the thinning areas 22 is less than the thickness of the main body areas 21. In this way, the thickness distribution of the pole piece is adjusted, and the pole piece semi-finished product structure of the application is formed.

[0037] When the pole piece semi-finished product structure of the application is used, the pole piece can be neatly wound by a winding device, so as to be cut and assembled subsequently. Due to the thinning treatment of the edge area of the pole piece, the thickness of the edge of the pole piece is closer to that of the central area, so that a relatively uniform thickness distribution is formed on the surface of the entire pole piece. Thus, the overall flatness of the pole piece can be maintained during the winding process, and the phenomenon of bulging due to uneven thickness is reduced. Meanwhile, the edge of the pole piece subjected to the thinning treatment is smoother, and the roughness and irregularity of the edge are reduced. The smooth edge can be more smoothly fitted on the winding shaft during the winding process, and stress concentration and frictional resistance caused by the uneven edge are reduced.

[0038] During the later process of the pole piece, specifically, the thinning areas 22 need to be removed after the pole piece is cut and before the battery cell is assembled. Specifically, a fine machining technology such as laser etching can be used to accurately remove the active material of the thinning areas 22 by using a laser beam, so that the active material of the thinning areas 22 of the pole piece is rapidly burned and gasified, and the metal conductive current collector 1 is exposed.

[0039] Therefore, by removing the thinning area 22, the problem of the NP ratio being too small due to insufficient active material in the thinning area 22 during use can be prevented after the cell laminates or are wound, and the problem of the thinning area 22 being blackened or even lithium precipitation can be prevented. This helps to improve the energy density, cycle life, safety, and the like of the battery.

[0040] The processing method by laser etching can accurately control the energy input, accurately remove the active material of the thinning area 22, and avoid damage to the surrounding area (for example, the main area 21).

[0041] As a preferred technical solution of the present application, the width of the active material coating layer 2 is L, and the width of the thinning area 22 is a, wherein the value range of a is 0.1%*L≤a≤20%*L.

[0042] It should be noted that although the thinning area 22 itself does not directly contribute to the energy density, by accurately controlling its width and completely removing the active material thereon in the subsequent process, the compactness and consistency of the overall structure of the battery can be ensured, thereby indirectly improving the energy density of the battery.

[0043] Specifically, the value range of a is not less than 0.1%*L, which can prevent the thinning area 22 from being too narrow, thereby avoiding the main area 21 being damaged due to operation errors or insufficient equipment precision during the process of removing the thinning area 22, ensuring the integrity and performance of the main area 21, and reducing the processing difficulty and cost. At the same time, the edge of the pole piece often has the phenomenon of stress concentration and enhanced electrochemical activity, and the too narrow thinning area 22 may not be able to effectively alleviate these edge effects, thereby affecting the overall performance of the battery.

[0044] Similarly, the value range of a is not greater than 20%*L, which can ensure that the main area 21 has sufficient width to carry sufficient active material, thereby ensuring the energy density and performance of the battery. If the thinning area 22 is too wide, the area of the main area 21 will be reduced, thereby reducing the energy output of the battery. At the same time, the edge region of the pole piece needs to withstand certain mechanical stress and electrochemical corrosion during the assembly and use of the battery; the too wide thinning area 22 may weaken the edge structural strength of the pole piece, increasing the risk of pole piece damage or deformation.

[0045] Therefore, by setting the value range of a to be between 0.1%*L and 20%*L, the thinning area 22 can effectively alleviate the edge effect, improve the feasibility of pole piece winding and assembly, and ensure that the main area 21 has sufficient width and performance; this helps to reduce material consumption and processing cost, and improve the cost-effectiveness of the product.

[0046] As a preferred technical solution of the present application, the thickness of the main area 21 is uniform, and the cross section of the main area 21 is rectangular.

[0047] Therefore, the uniformity of the thickness of the main region 21 can ensure the uniform distribution of the active material on the current collector 1, thereby making the current distribution on the electrode more uniform; it helps to reduce the current density difference inside the battery, reduce the risk of local overheating and lithium deposition, and thus improve the performance stability and safety of the battery.

[0048] In addition, the cross-sectional shape of the main body region 21 is rectangular, which is conducive to achieving precise control of the width and thickness of the coating and reducing performance fluctuations caused by irregular shapes.

[0049] As a preferred technical solution of this application, see Figure 1 The thickness of the thinned area 22 is uniform, and the cross-section of the thinned area 22 is rectangular.

[0050] The uniform thickness of the skived area 22 enables removal processes such as laser etching to maintain consistent processing efficiency and depth throughout the entire skived area 22, avoiding incomplete or excessive removal due to uneven thickness, thereby improving production efficiency and yield. Furthermore, the simple and clear rectangular cross-section of the skived area 22 facilitates precise positioning and processing by processing tools such as laser beams. Operators simply follow pre-set processing parameters to achieve rapid and precise removal of active material from the skived area 22.

[0051] It should be noted that due to the sudden change in thickness, there is a clear boundary between the thinned area 22 and the main area 21. Therefore, when removing the active material in the thinned area 22, it is easier to avoid accidental damage to the main area 21, which helps to maintain the integrity and performance of the main area 21.

[0052] Therefore, by completely removing the active material from the thinned area 22, the current distribution within the battery is optimized, reducing current density differences and local overheating caused by edge effects. This also prevents a low NP ratio due to insufficient active material during subsequent battery use, thereby reducing the occurrence of lithium plating.

[0053] As a preferred technical solution of this application, see Figure 2 The thickness of the thinned area 22 gradually decreases from the side close to the main area 21 to the side away from the main area 21, and the cross-section of the thinned area 22 is triangular.

[0054] That is, the thickness of the thinned area 22 is designed to be gradual, so that when removing the active material on the thinned area 22, laser etching or other cleaning tools can more easily penetrate the thinner part and gradually penetrate into the thicker part; the gradual thickness distribution helps to reduce energy loss during the cleaning process and improve the cleaning efficiency.

[0055] At the same time, since the thinning area 22 and the main area 21 transition through a gradual thickness change, when removing the active material in the thinning area 22, it is easier to control the removal depth to avoid unnecessary damage to the main area 21; this helps to maintain the integrity and performance stability of the main area 21.

[0056] In addition, since there is a clear boundary between the thinned area 22 and the main area 21 (such as achieved by precisely controlling the thinning width a), accidental damage to the main area 21 can be avoided when removing the active material in the thinned area 22.

[0057] Therefore, by precisely controlling the shape and width of the thinning area 22, it is possible to remove excess material while retaining as much active material as possible in the center area of ​​the electrode, thereby optimizing the distribution of active materials in the entire electrode and helping to improve the energy density and cycle performance of the battery cell.

[0058] As a preferred technical solution of this application, see Figure 3 The thinned area 22 includes a first thinned area 22 and a second thinned area 22. The first thinned area 22 connects the second thinned area 22 and the main area 21. The thickness of the first thinned area 22 is uniform, and the thickness of the second thinned area 22 gradually decreases from the side close to the first thinned area 22 to the side away from the first thinned area 22. The cross-section of the thinned area 22 is trapezoidal.

[0059] The uniform thickness of the first thinned area 22 allows the cleaning tool (such as a laser etching device) to maintain a consistent processing speed and depth in this area, thereby improving cleaning efficiency. Furthermore, the uniform thickness facilitates precise control of the cleaning process, reducing the risk of over- or under-cleaning. The thickness of the second thinned area 22 gradually decreases, allowing the cleaning tool to easily penetrate the thinner portion and gradually penetrate into the thicker portion, further improving cleaning efficiency. Furthermore, the gradual thickness provides a natural transition area for the cleaning tool, helping to maintain the accuracy and consistency of the cleaning path.

[0060] In addition, the cross-section of the overall thinned area 22 is trapezoidal, forming a smooth transition between the thinned area 22 and the main area 21. During the cleaning process, this smooth transition helps reduce stress concentration caused by sudden changes, thereby reducing the risk of damage to the main area 21.

[0061] Furthermore, the uniform thickness of the first skived region 22, which serves as a transitional region connecting the second skived region 22 and the main body region 21, acts as a buffer. When the second skived region 22 is removed, the first skived region 22 can partially absorb the impact and vibration generated during the removal process, further protecting the main body region 21 from damage.

[0062] It should be noted that when forming the thinning areas 22 of the above three different cross-sectional shapes, the thick edge of the active material layer can be thinned by mechanical thinning, chemical etching thinning or laser thinning. Among them, the mechanical thinning method mainly thins the thick edge of the edge of the pole piece directly by mechanical cutting, grinding or compression. The chemical etching thinning method uses a chemical corrosive agent to corrode the thick edge of the pole piece to achieve the purpose of thinning. The laser thinning method uses a laser beam to accurately thin the edge of the pole piece; the laser beam has the characteristics of high precision and high energy density, and can realize fine processing of the edge of the pole piece. The present application preferably uses the laser thinning method to form the thinning area 22.

[0063] In summary, by forming thinned regions 22 with various cross-sectional shapes, this application facilitates the laser etching equipment to more accurately identify and locate the areas where active material needs to be removed during the back-end manufacturing process of the electrode. The laser beam can be precisely scanned along a pre-set path, ensuring that only the active material in the target area is removed without damaging surrounding areas.

[0064] As a preferred technical solution of the present application, both sides of the main body area 21 are connected to the thinning area 22.

[0065] During the winding process, the pole piece may experience uneven tension due to thickness differences on both sides. The presence of the thinned area 22 can balance this difference, allowing the pole piece to maintain a relatively uniform tension distribution during winding, helping to reduce problems such as pole piece deformation, wrinkling, or breakage caused by uneven tension.

[0066] In addition, in the latter stage of the electrode manufacturing process, after the active material on the thinned area 22 is completely removed by a cleaning tool and the current collector 1 is exposed, the current distribution on both sides of the main area 21 can be made more uniform; this helps to reduce performance degradation problems caused by uneven current distribution, such as capacity attenuation and increased internal resistance.

[0067] As a preferred technical solution of the present application, the cross-sectional shapes of the thinned areas 22 on both sides of the main area 21 are the same or different.

[0068] Specifically, when the cross-sectional shapes of the thinned regions 22 on either side of the main region 21 differ, stress can be dispersed or transferred to varying degrees, thereby reducing stress concentration at the edge of the main region 21. Furthermore, because the cross-sectional shapes of the thinned regions 22 on either side differ, the active material region requiring removal can be more accurately located by identifying the different shapes of the thinned regions 22 on either side.

[0069] Preferably, the thinned areas 22 on both sides of the main area 21 are set to have the same cross-sectional shape. In this way, during the production process, the thinned areas 22 on both sides can be processed using the same process and equipment, thereby improving production efficiency and consistency. Among them, the same cross-sectional shape means that the thinned areas 22 on both sides are more balanced in physical properties (such as stress distribution, heat conduction, etc.), which helps to maintain the stability of the overall performance of the battery. And when cleaning the thinned areas 22, since the cross-sectional shapes of the thinned areas 22 on both sides are the same, the same cleaning tools and methods can be used for processing, avoiding the trouble of changing tools or adjusting process parameters due to different shapes, thereby improving cleaning efficiency.

[0070] As a preferred technical solution of the present application, there is a current collector exposed area between the periphery of the thinned area 22 and the periphery of the current collector 1 .

[0071] The exposed current collector area acts as a "bridge" for current transmission, allowing current to flow more smoothly within the battery. This helps reduce current losses during transmission and improves the battery's energy conversion efficiency. Simultaneously, the exposed current collector area reduces the contact resistance between the current collector 1 and the active material, thereby lowering the battery's internal resistance. Low internal resistance means the battery responds faster during charge and discharge, improving its power density and cycle stability.

[0072] It should be noted that during the post-electrode manufacturing process, the thinned region 22 is removed to expose the current collector 1, further optimizing the current distribution within the battery. By properly configuring the width and shape of the thinned region 22, the current can flow more evenly within the battery, reducing performance degradation or safety issues caused by uneven current distribution.

[0073] Example 2

[0074] See Figure 4 This embodiment discloses a pole piece, which is formed by processing the pole piece semi-finished structure of the first embodiment. Specifically, the pole piece includes a current collector 1 and an active material layer, wherein the active material layer is located in the middle of the current collector 1, an exposed current collector area exists between the edge of the active material layer and the edge of the current collector 1, and the thickness of the active material layer is uniform.

[0075] The electrode of this embodiment is formed by processing the semi-finished electrode structure of the first embodiment. Specifically, in the back-end process of the electrode, the active material in the thinned area 22 is completely removed by a removal tool such as a laser etching device, exposing the current collector 1, so that the active material layer retains the main area 21 with uniform thickness. Among them, the shape of the thinned area 22 is designed in this application to play a positioning role, facilitating the guidance of the laser beam to remove the thinned area 22 without damaging the main area 21.

[0076] Therefore, the pole piece in this embodiment is manufactured by further processing the pole piece semi-finished product structure, which makes the pole piece processing process more refined and automated, thereby improving production efficiency and product quality.

[0077] The technical means disclosed in the present application are not limited to those disclosed in the above-mentioned embodiments, but also include technical solutions composed of any combination of the above-mentioned technical features. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the present application, and such improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A semi-finished pole piece structure, characterized by: It includes a current collector, and active material coatings are provided on both sides of the current collector. The active material coatings include a main area and a thinning area. The main area is arranged in the middle area of ​​the current collector, and the thinning area is arranged in the edge area of ​​the current collector; the thickness of the thinning area is less than the thickness of the main area.

2. The pole piece semi-finished structure according to claim 1, characterized in that: The width of the active material coating is L, the width of the thinned area is a, and the value range of a is 0.1%*L≤a≤20%*L.

3. The pole piece semi-finished structure according to claim 1, characterized in that: The thickness of the main body area is uniform, and the cross section of the main body area is rectangular.

4. The pole piece semi-finished structure according to claim 3, characterized in that: The thickness of the thinned area is uniform, and the cross section of the thinned area is rectangular.

5. The pole piece semi-finished structure according to claim 3, characterized in that: The thickness of the thinned area gradually decreases from a side close to the main area to a side away from the main area, and the cross-section of the thinned area is triangular.

6. The pole piece semi-finished structure according to claim 3, characterized in that: The thinning zone includes a first thinning zone and a second thinning zone, the first thinning zone connects the second thinning zone and the main zone; the thickness of the first thinning zone is uniform, and the thickness of the second thinning zone gradually decreases from the side close to the first thinning zone to the side away from the first thinning zone, and the cross-section of the thinning zone is trapezoidal.

7. The pole piece semi-finished structure according to any one of claims 1 to 6, characterized in that: Both sides of the main body area are connected to the thinned areas.

8. The pole piece semi-finished product structure according to claim 7, characterized in that: The cross-sectional shapes of the thinned areas on both sides of the main area are the same or different.

9. The pole piece semi-finished structure according to claim 7, characterized in that: There is a current collector exposed area between the periphery of the thinned area and the periphery of the current collector.

10. A pole piece, characterized in that: The pole piece is formed by processing the pole piece semi-finished product structure according to any one of claims 1 to 9.

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