Electrode sheet and preparation method therefor

Abstract

Provided are an electrode sheet and a preparation method therefor. The electrode sheet comprises a current collector, a transition layer, and an active material layer. The transition layer is connected to the current collector, and a first groove is formed on the side of the transition layer away from the current collector. The active material layer is connected to the current collector, the active material layer covers the transition layer, at least part of the active material layer is located in the first groove, the active material layer is provided with a removal region, and the removal region corresponds to the transition layer. By forming the first groove on the side of the transition layer away from the current collector, compensation space can be provided in the thickness direction of the current collector, such that a portion of the active material layer can fill the first groove to reduce the height of a protrusion formed on the surface of the active material layer. Thus, after removing part of the active material layer in the removal region, the height of the protrusion on the surface of the active material layer and a height difference between the protrusion and the transition layer are reduced, thereby effectively reducing the probability of wrinkling of electrode sheets after the completion of a rolling process, and ensuring the yield of electrode sheets.

Description

Pole piece and method for preparing same Technical Field

[0001] The present invention relates to the technical field of battery preparation, and in particular to a pole piece and a method for preparing the pole piece. Background Art

[0002] Related technology pre-coats a transition layer on the surface of the current collector before coating the active material on the current collector, so as to improve the performance of the electrode through the transition layer. The coating of the active material layer will cover the transition layer and form certain protrusions at the corresponding position of the transition layer. In the subsequent process, it is necessary to remove a part of the active material layer to expose the transition layer to ensure the performance of the transition layer. After removing part of the active material layer, there will still be some protrusions on the surface of the active material layer, and there is a large height difference between the protrusion and the flat surface of the active material layer relative to the height of the current collector, and there is also a large height difference between the protrusion and the transition layer relative to the height of the current collector. The large height difference will increase the probability of wrinkling of the electrode during the subsequent rolling process. Therefore, it is necessary to study and solve the above problems.

[0003] Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a pole piece that can reduce the probability of wrinkling of the pole piece after the rolling process, thereby ensuring the pole piece yield.

[0005] The present invention also provides a method for preparing the pole piece.

[0006] A pole piece according to an embodiment of the present invention includes a current collector, a transition layer, and an active material layer. The current collector has a predetermined thickness. The transition layer is connected to the current collector, and a first groove is provided on a side of the transition layer facing away from the current collector. The active material layer is connected to the current collector, covering the transition layer, with at least a portion of the active material layer located within the first groove. The active material layer has a removal area corresponding to the transition layer.

[0007] The pole piece according to an embodiment of the present invention has at least the following beneficial effects: by providing a first groove on the side of the transition layer facing away from the current collector, a compensation space is provided in the thickness direction of the current collector, allowing a portion of the active material layer to fill the first groove, thereby reducing the height of the protrusions formed on the surface of the active material layer. Furthermore, after the portion of the active material layer in the removal area is removed, the height difference formed by the protrusions is reduced, effectively reducing the probability of wrinkling in the pole piece after the rolling process, thereby ensuring the pole piece yield.

[0008] According to some embodiments of the present invention, the current collector has a set length, and the first groove and the removal area are staggered in the length direction.

[0009] According to some embodiments of the present invention, the projection of the removal area on the end face of the transition layer along the thickness direction is located on the inner side of the end face of the transition layer in the length direction, and the first groove is located on the outer edge of the transition layer in the thickness direction perpendicular to the current collector.

[0010] According to some embodiments of the present invention, the current collector has a set width, and the first grooves are provided on outer edges of the transition layer in both the length direction and the width direction.

[0011] According to some embodiments of the present invention, the side of the transition layer facing away from the current collector has a first end face and a second end face, the first end face is the end face of the transition layer facing away from the current collector with the largest distance from the current collector, the distance between the first end face and the current collector is L1, the second end face is the bottom surface of the first groove facing the current collector, the distance between the second end face and the current collector is L2, satisfying: 2um≤L1-L2≤20μm.

[0012] According to some embodiments of the present invention, the transition layer is a ceramic layer.

[0013] According to some embodiments of the present invention, a second groove is provided on the side of the active material layer facing away from the current collector, the second groove corresponds to the removal area, and the second groove communicates with the surface of the transition layer facing away from the current collector.

[0014] The method for preparing a pole piece according to an embodiment of the present invention is used to prepare the pole piece in the above embodiment, comprising the following steps:

[0015] coating a transition layer coating on one side of the current collector to form a transition layer;

[0016] removing a portion of the transition layer away from the current collector to form a first groove;

[0017] An active material layer coating is applied to the current collector so that at least a portion of the active material layer coating covers the transition layer to form an active material layer.

[0018] The method for preparing the electrode according to the embodiment of the present invention has at least the following beneficial effects: by removing a portion of the transition layer to form a first groove, part of the active material layer can be located in the first groove after the active material layer coating is coated and formed. The first groove can provide spatial compensation to reduce the protrusion height of the active material layer caused by the setting of the transition layer, so as to reduce the probability of wrinkling of the electrode after the subsequent rolling process is completed, thereby ensuring the yield of the electrode.

[0019] According to some embodiments of the present invention, after forming the active material layer, the further step is included: removing a portion of the active material layer away from the current collector to form a second groove exposing the transition layer.

[0020] According to some embodiments of the present invention, after the active material layer is formed, the following steps are also included: removing a portion of the active material layer facing away from the current collector; removing a portion of the transition layer facing away from the current collector, and a second groove is defined between the active material layer and the transition layer to expose the transition layer.

[0021] According to some embodiments of the present invention, after forming the second groove, the method further includes the following steps: rolling the current collector, the active material layer, and the transition layer.

[0022] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0024] FIG1 is a schematic diagram of a pole piece according to an embodiment of the present invention;

[0025] FIG2 is a cross-sectional view of a pole piece according to an embodiment of the present invention;

[0026] FIG3 is a cross-sectional view of pole pieces according to other embodiments of the present invention;

[0027] FIG4 is a partial schematic diagram of a pole piece according to an embodiment of the present invention;

[0028] FIG5 is a schematic diagram of a pole piece according to an embodiment of the related art;

[0029] FIG6 is a cross-sectional view of a pole piece according to an embodiment of the related art;

[0030] FIG7 is a cross-sectional view of pole pieces according to other embodiments of the related art;

[0031] FIG8 is a cross-sectional view of a pole piece according to another embodiment of the related art;

[0032] FIG9 is a flow chart of a method for preparing a pole piece according to some embodiments of the present invention;

[0033] FIG10 is a flow chart of a method for preparing a pole piece according to other embodiments of the present invention;

[0034] FIG11 is a flow chart of a method for preparing a pole piece according to other embodiments of the present invention.

[0035] Reference numerals:

[0036] Current collector 100, transition layer 200, first groove 201, first end surface 210, second end surface 220, active material layer 300, second groove 310, removed area 320;

[0037] Current collector 400 , transition layer 410 , active material layer 420 , protrusion 421 , and wrinkle 430 . DETAILED DESCRIPTION

[0038] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0039] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They 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 orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0040] In the description of the present invention, "several" means more than one, "plurality" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

[0041] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0042] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0043] Referring to Figures 6 to 8, Figure 6 shows a related art electrode sheet with the active material layer intact. Figure 7 shows the electrode sheet in Figure 6 with a portion of the active material layer removed, exposing the transition layer. Figure 8 shows the electrode sheet in Figure 7 after roller pressing. In related art, after the active material layer 420 is coated on the current collector 400, a protrusion 421 is formed on the active material layer 420 at a location corresponding to the transition layer 410, facing away from the current collector 400. After the active material layer 420 is partially removed to expose the transition layer 410, a height difference exists between the protrusion 421 and the flat surface of the active material layer 420 relative to the height of the current collector 400. The protrusion 421 also exists between the protrusion 421 and the transition layer 410 relative to the height of the current collector 400. Due to the presence of the protrusion 421, the electrode sheet will become wrinkled after roller pressing, forming wrinkles 430, as shown in Figure 8. This affects the flatness of the electrode sheet and, in turn, its performance. In order to solve the above problems, the present application provides a first groove on the transition layer, and the first groove provides a compensation space in the thickness direction to reduce the protruding height of the protrusion and the height difference formed, reduce the probability of wrinkling after rolling, and improve the flatness of the pole piece after rolling.

[0044] The following describes the pole piece of the embodiment of the present application with reference to the drawings in the specification. It should be noted that the active material layer 300 is not removed in Figures 1 and 5, and the transition layer 200 and the projection area of ​​the removed area 320 along the thickness direction are shown by cross-hatching for illustration. Figure 4 only shows the transition layer 200 and a portion of the current collector 100. Although the protrusions are not clearly shown in Figures 2 to 4, there are actually protrusions of smaller amplitude, which are not emphasized in the figures for the sake of convenience. The specific position and shape of the protrusions can be seen in Figures 6 and 7.

[0045] Referring to Figures 1 to 4, a pole piece according to an embodiment of the present invention includes a current collector 100, a transition layer 200, and an active material layer 300. The current collector 100 has a predetermined thickness. The transition layer 200 is connected to the current collector 100. A first groove 201 is provided on the side of the transition layer 200 facing away from the current collector 100. The active material layer 300 is connected to the current collector 100, covering the transition layer 200. At least a portion of the active material layer 300 is located within the first groove 201. The active material layer 300 is provided with a removed area 320, which corresponds to the transition layer 200. Providing the first groove 201 on the side of the transition layer 200 facing away from the current collector 100 provides a compensation space in the thickness direction of the current collector 100, allowing a portion of the active material layer 300 to fill the first groove 201, thereby reducing the height of the protrusion formed on the surface of the active material layer 300. After the removal of part of the active material layer 300 in the removal area 320 is completed, the height difference formed by the protrusion is reduced, which effectively reduces the probability of wrinkling of the electrode after the rolling process is completed, thereby ensuring the electrode yield.

[0046] The provision of the transition layer 200 can reduce the probability of the battery catching fire or generating heat when subjected to abnormal conditions such as squeezing, collision or puncture, and better protect the current collector 100, reduce the short-circuit runaway problem caused by the exposed edge of the current collector 100, and improve the safety of the battery. The transition layer 200 can be a layer comprising nickel-cobalt-manganese ternary material particles or lithium iron phosphate particles. The properties of the nickel-cobalt-manganese ternary material particles and lithium iron phosphate particles can be used to reduce the energy density of the battery and the probability of the battery's cycle performance decreasing to ensure battery performance. In some embodiments, the transition layer 200 is a ceramic layer, which includes ceramic particles. The ceramic particles can reduce the probability of lithium plating during low-temperature charging of the battery, thereby slowing down the battery's capacity decay rate and improving the safety of the battery. At the same time, the ceramic layer can further increase the bonding force between the active material layer 300 and the current collector 100, reduce the expansion amplitude of the electrode during the cycle, ensure the electrical performance of the battery, and extend the battery's service life.

[0047] 2 and 3 , in some embodiments, a second groove 310 is provided on the side of the active material layer 300 facing away from the current collector 100. The second groove 310 corresponds to the removed area 320 and is connected to the surface of the transition layer 200 facing away from the current collector 100. The second groove 310 is formed after removing part of the active material layer 300 in the area 320, which can reduce a portion of the active material layer 300, thereby reducing the probability of lithium deposition when the electrode is applied to the cathode. In addition, by exposing the transition layer 200 through the second groove 310 and allowing the transition layer 200 to correspond to the tab, the probability of the tab's burrs and other structures piercing the electrode surface and directly contacting the current collector 100 can be effectively reduced, thereby improving the safety performance of the electrode.

[0048] 1 and 3 , the removal region 320 provided in the active material layer 300 is within the raised region formed after the active material layer 300 is applied to the transition layer 200. In some embodiments, the projection of the removal region 320 in the thickness direction is located within the end face of the transition layer 200, that is, the projection of the second groove 310 in the thickness direction is located within the end face of the transition layer 200, to ensure that the transition layer 200 can be accurately exposed after a portion of the active material layer 300 is removed, and that the transition layer 200 can be accurately positioned when applied to correspond to the tab.

[0049] After removing the portion of the active material layer 300 in the removal area 320, referring to FIG3 , an unremoved protrusion exists in the portion of the active material layer 300 not covered by the projection of the transition layer 200 by the second groove 310. In some embodiments, referring to FIG3 and FIG4 , the first groove 201 and the removal area 320 are staggered in the length direction of the current collector 100 so that the position of the spatial compensation provided by the first groove 201 directly corresponds to the unremoved protrusion. This minimizes the height of the protrusion formed on the surface of the active material layer 300 and the height difference with the transition layer 200, further ensuring the flatness of the electrode surface after the subsequent rolling operation and reducing the probability of wrinkling.

[0050] Referring to Figures 1 and 3 , the projection of the removal region 320 along the thickness direction onto the end surface of the transition layer 200 is located inward of the end surface of the transition layer 200 along the length direction of the current collector 100, ensuring that after the portion of the active material layer 300 is removed, the second groove 310 formed can completely correspond to the transition layer 200. Furthermore, the first groove 201 is located at the outer edge of the transition layer 200 in the direction perpendicular to the thickness of the current collector 100 to ensure the spatial compensation effect provided by the first groove 201. In a further embodiment, the transition layer 200 is provided with the first groove 201 along both the longitudinal and width directions of the current collector 100. This ensures that after the portion of the active material layer 300 is removed, it can surround the second groove 310, ensuring that the protrusion formed along the circumference of the second groove 310 is spatially compensated, improving uniformity and further reducing the likelihood of subsequent wrinkling. Specifically, the first groove 201 can extend along the circumference of the transition layer 200 as a U-shaped groove to semi-enclose the removal region 320. Alternatively, the first grooves 201 distributed in the length direction and the first grooves 201 distributed in the width direction are combined into an L-shaped groove.

[0051] The occurrence of wrinkling is closely related to the height of the protrusions of the active material layer 300 and the resulting height difference. Based on this, as another improvement to the above solution, referring to Figure 4 , the side of the transition layer 200 facing away from the current collector 100 has a first end face 210 and a second end face 220. The first end face 210 is the end face of the transition layer 200 facing away from the current collector 100 with the largest distance from the current collector 100. The distance between the first end face 210 and the current collector 100 is L1. The second end face 220 is the bottom surface of the first groove 201 facing the current collector 100. The distance between the second end face 220 and the current collector 100 is L2, satisfying the following: 2μm ≤ L1-L2 ≤ 20μm. By controlling the difference between L1 and L2, the depth of the first groove 201 in the thickness direction can be controlled, thereby adjusting the spatial compensation effect. When L1-L2 is less than 2μm, the depth of the first groove 201 is small, and the spatial compensation provided is too small. Setting 2um≤L1-L2 can ensure sufficient depth for spatial compensation. When L1-L2 is greater than 20μm, the transition layer 200 is required to have a greater thickness. The thickness of the transition layer 200 may even be greater than the set thickness of the active material layer 300, which will affect the use of the electrode. In addition, the thicker active material layer 300 needs to be removed in the removal area 320, which is prone to over-removal during removal, resulting in exposure of the current collector 100, a high defect rate, and high process requirements. Therefore, controlling L1-L2 between 2μm and 20μm can facilitate the preparation of the transition layer 200 while achieving a good spatial compensation effect.

[0052] 9 , a method for preparing a pole piece according to an embodiment of the present invention is used to prepare the pole piece in the above embodiment, including the following steps:

[0053] S100, coating a transition layer coating on one side of the current collector 100 to form a transition layer 200;

[0054] S200 , removing a portion of the transition layer 200 facing away from the current collector 100 to form a first groove 201 ;

[0055] S300 , applying an active material layer coating to the current collector 100 , so that at least a portion of the active material layer coating covers the transition layer 200 , to form an active material layer 300 .

[0056] By removing a portion of the transition layer 200 in step S200 to form a first groove 201, a portion of the active material layer 300 can be located in the first groove 201 after the active material layer 300 is coated and formed in step S300. The first groove 201 can provide spatial compensation to reduce the protrusion height of the active material layer 300 caused by the setting of the transition layer 200, so as to reduce the probability of wrinkling of the electrode after the subsequent rolling process is completed, thereby ensuring the electrode yield.

[0057] 10 , in some embodiments, after forming the active material layer 300, the following step is further included: S400, removing a portion of the active material layer 300 facing away from the current collector 100 to form a second groove 310 exposing the transition layer 200. In step S500, by removing a portion of the active material layer 300 to form the second groove 310, the transition layer 200 is exposed.

[0058] Referring to Figure 11 , in some other embodiments, after forming the active material layer 300, the following steps are further included: S500, removing a portion of the active material layer 300 facing away from the current collector 100. S510, removing a portion of the transition layer 200 facing away from the current collector 100, thereby defining a second groove 310 between the active material layer 300 and the transition layer 200, exposing the transition layer 200. Based on the removal of the portion of the active material layer 300 in step S510, the second groove 310 is formed by removing a portion of the transition layer 200 facing away from the current collector 100 in step S520. This allows the maximum thickness of the transition layer 200 to be reduced after the active material layer 300 is formed, thereby reducing the depth of the first groove 201 at this point, making the transition layer 200 more flat overall. This further improves the surface uniformity of the active material layer 300 during the subsequent rolling process.

[0059] The active material layer 300 and the transition layer 200 may be removed by laser removal, or by conventional removal methods in the art such as manual scraping and mechanical scraping.

[0060] After forming the second groove 310, the following step is further included: S600, rolling the current collector 100, the active material layer 300, and the transition layer 200. After the rolling operation of step S600, the current collector 100, the active material layer 300, and the transition layer 200 can be compacted to improve the performance of the electrode sheet.

[0061] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A pole piece, characterized in that: include: a current collector having a set thickness; A transition layer connected to the current collector, wherein a first groove is provided on a side of the transition layer away from the current collector; An active material layer is connected to the current collector, the active material layer covers the transition layer, at least a portion of the active material layer is located in the first groove, and the active material layer is provided with a removal area, and the removal area corresponds to the transition layer.

2. The pole piece according to claim 1, characterized in that: The current collector has a set length, and the first groove and the removal area are staggered in the length direction.

3. The pole piece according to claim 2, characterized in that: The projection of the removal area on the end surface of the transition layer along the thickness direction is located on the inner side of the end surface of the transition layer in the length direction, and the first groove is located on the outer edge of the transition layer in the thickness direction perpendicular to the current collector.

4. The pole piece according to claim 3, characterized in that: The current collector has a set width, and the transition layer is provided with the first grooves at outer edges in the length direction and the width direction.

5. The pole piece according to claim 1, characterized in that: The side of the transition layer facing away from the current collector has a first end face and a second end face, the first end face is the end face of the transition layer facing away from the current collector and having the largest distance from the current collector, the distance between the first end face and the current collector is L1, the second end face is the bottom surface of the first groove facing the current collector, the distance between the second end face and the current collector is L2, satisfying: 2um≤L1-L2≤20μm.

6. The pole piece according to claim 1, characterized in that: The transition layer is a ceramic layer.

7. The pole piece according to any one of claims 1 to 6, characterized in that: A second groove is provided on the side of the active material layer away from the current collector, the second groove corresponds to the removal area, and the second groove is connected to the surface of the transition layer away from the current collector.

8. A method for preparing a pole piece, used for preparing the pole piece according to any one of claims 1 to 7, characterized in that: The following steps are involved: Coating a transition layer coating on one side of the current collector to form a transition layer; Removing a portion of the transition layer away from the current collector to form a first groove; An active material layer coating is applied to the current collector so that at least a portion of the active material layer coating covers the transition layer to form an active material layer.

9. The method for preparing a pole piece according to claim 8, characterized in that: After forming the active material layer, the method further comprises the following steps: removing a portion of the active material layer away from the current collector to form a second groove exposing the transition layer.

10. The method for preparing a pole piece according to claim 8, characterized in that: After forming the active material layer, the method further comprises the following steps: removing a portion of the active material layer away from the current collector; A portion of the transition layer facing away from the current collector is removed, and a second groove exposing the transition layer is defined between the active material layer and the transition layer.

11. The method for preparing a pole piece according to claim 9 or 10, characterized in that: After forming the second groove, the method further includes the following steps: rolling the current collector, the active material layer and the transition layer.

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