Cathode plate and battery cell

Abstract

The utility model provides a cathode piece and a battery cell, which are characterized in that a current collector is adjacently provided with a coating section and a blank section along a first direction, the first direction is the extension direction of the current collector, and a first boundary is arranged on the current collector to divide the coating section and the blank section; one part of the first gummed paper is attached to one side, back to the current collector, of the cathode active material layer, and the other part of the first gummed paper is attached to the blank section so as to cover the first boundary; the second boundary is the edge of the gummed paper on the cathode active material layer; the first resistance layer is arranged on the face, facing the first gummed paper, of the current collector, the first resistance layer is coated with the cathode active material layer, the conductivity of the first resistance layer is lower than that of the current collector, the projection of the second boundary in the second direction is located in the projection of the first resistance layer in the second direction, and the second direction is the thickness direction of the cathode piece. According to the cathode plate and the battery cell, the lithium precipitation phenomenon of the battery cell can be effectively avoided.

Description

Technical Field

[0001] This utility model relates to the field of new energy technology, and in particular to a cathode sheet and a battery cell. Background Technology

[0002] In lithium battery manufacturing, adhesive tape is often applied to the cathode sheet for various reasons. One reason is to address concerns about deviations in film length design and differences in the matching of thinning at the cathode and anode ends. This is often achieved by applying adhesive tape to the cathode end to ensure the effective anode film length exceeds the effective cathode film length at the end of the wound cell. Another reason is to prevent short circuits within the cell. Adhesive tape is placed at the cathode tabs on the cathode sheet or at positions on the cathode sheet corresponding to the anode tabs on the anode sheet. When adhesive tape is applied to the cathode sheet, it covers part of the cathode active material. During charge-discharge cycles, some lithium ions from this covered material migrate from the edges of the tape and embed into the anode sheet, leading to excessive lithium intercalation in that area and causing lithium plating. Therefore, a cathode sheet design is needed to reduce lithium ion release in this area, effectively preventing lithium plating on the anode sheet. 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 cathode sheet that can effectively prevent lithium plating in the battery cell.

[0004] This utility model also proposes a battery cell.

[0005] A cathode sheet according to a first aspect of the present invention includes: a current collector having a coated section and a blank section disposed adjacent to each other along a first direction, the first direction being the extension direction of the current collector; at least one side of the coated section being coated with a cathode active material layer; and the blank section being exposed outside the cathode active material layer; a first dividing line being disposed on the current collector to separate the coated section and the blank section; a first adhesive tape having a portion attached to the cathode active material layer on the side opposite to the current collector, and another portion attached to the blank section to cover the first dividing line; a second dividing line being the edge of the first adhesive tape on the cathode active material layer along the first direction; and a first resistive layer being disposed on the side of the current collector facing the first adhesive tape, the cathode active material layer being coated on the first resistive layer, the conductivity of the first resistive layer being lower than the conductivity of the current collector, and the projection of the second dividing line in a second direction being located within the projection of the first resistive layer in the second direction, the second direction being the thickness direction of the cathode sheet.

[0006] The cathode sheet according to the first aspect of the present invention has at least the following beneficial effects: the lithium ions attached to the cathode active material by the first adhesive tape cannot migrate directly to the anode sheet, so some lithium ions will migrate laterally, thereby increasing the amount of lithium ions removed from the area near the second boundary line. Therefore, after setting the first resistive layer in this area, the resistance of this area is increased, thereby reducing the offshore current in this area and reducing the rate of lithium ion removal in this area, thus effectively avoiding lithium plating in this area.

[0007] According to some embodiments of the present invention, the first resistive layer is disposed in the coating section, and the first resistive layer has a first end and a second end in the first direction. The first end is located between the first boundary line and the second boundary line in the first direction, and the second end is disposed on the side of the second boundary line away from the first boundary line in the first direction.

[0008] According to some embodiments of the present invention, the distance between the first end and the first dividing line in the first direction is no more than 1 mm, and the distance between the second end and the second dividing line in the first direction is not less than 1 mm and not more than 20 mm.

[0009] According to some embodiments of the present invention, the cathode active material layer, the first adhesive paper and the first resistive layer are provided on both sides of the current collector.

[0010] According to some embodiments of this utility model, the cathode sheet further includes a cathode tab, which is fixed on the current collector. A groove is formed on the cathode active material layer, and the cathode tab is accommodated in the groove. A second adhesive paper is covered on the side of the cathode tab away from the current collector. A second resistive layer is provided on the side of the current collector facing the second adhesive paper. The cathode active material layer is coated on the second resistive layer. The groove penetrates the cathode active material layer and the second resistive layer along a second direction. The projection of the edge of the second adhesive paper along the second direction is located within the projection of the second resistive layer in the second direction. The conductivity of the second resistive layer is lower than the conductivity of the current collector.

[0011] According to some embodiments of the present invention, the second resistive layer is disposed along an edge path, the edge path being the projection of the edge of the second adhesive paper onto the current collector along the second direction, and the width of the second resistive layer disposed along the edge path is not less than 3mm and not more than 20mm.

[0012] According to some embodiments of this utility model, a third adhesive paper is provided on the side of the cathode active material facing away from the current collector. The third adhesive paper corresponds to the anode tab on the anode plate. The projection of the anode tab in the second direction is located within the projection of the third adhesive paper in the second direction. A third resistive layer is provided on the side of the current collector facing the third adhesive paper. The cathode active material layer is coated on the third resistive layer. The projection of the third adhesive paper along the second direction is located within the projection of the third resistive layer along the second direction. The conductivity of the third resistive layer is lower than the conductivity of the current collector.

[0013] According to some embodiments of the present invention, the distance between the edge of the third adhesive paper projected along the second direction and the edge of the third resistive layer projected along the second direction is not less than 1 mm and not more than 20 mm.

[0014] According to some embodiments of the present invention, the material of the first resistive layer is a conductive adhesive coating, a conductive nano coating, or a lithium iron phosphate coating.

[0015] The battery according to a second aspect of the present invention includes the cathode sheet described in any of the above embodiments.

[0016] 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

[0017] Figure 1 This is a schematic diagram of the structure of a cathode sheet in a battery cell according to the present invention;

[0018] Figure 2 This is a schematic diagram of the structure of the first resistive layer region of a cathode sheet according to the present invention;

[0019] Figure 3 This is a schematic diagram of the structure of the second resistive layer region of a cathode sheet according to the present invention.

[0020] Icon labels:

[0021] 1. Cathode plate; 11. Current collector; 111. Blank section; 112. Coated section; 12. Cathode active material layer; 13. Cathode tab; 14. First adhesive tape; 15. Second adhesive tape; 16. Third adhesive tape; 17. First resistive layer; 18. Second resistive layer; 19. Third resistive layer; 2. Anode plate; 3. Diaphragm; 4. First boundary line; 5. Second boundary line; 6. Edge path. 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 orientation descriptions, such as up and down, are based on the orientation 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, "multiple" refers to two or more. The use of "first" and "second" is for distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features or their sequential relationship.

[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] Lithium plating in batteries is a significant problem. There are many reasons for this, but a common one is that a localized area on the cathode may experience a faster release rate of lithium ions, preventing the anode from absorbing them quickly enough and leading to lithium crystallization and plating. Excessive lithium ion release in localized areas can also cause plating. The main hazards of lithium plating are as follows: First, it significantly reduces battery capacity. Normally, lithium ions should be uniformly embedded in the negative electrode material. However, lithium plating causes some lithium ions to form lithium metal on the negative electrode surface, preventing them from participating in the charging and discharging process. This reduces the number of usable lithium ions and consequently lowers battery capacity. Furthermore, lithium plating increases internal resistance, reduces charging and discharging efficiency, and further impacts battery performance. Second, it shortens battery cycle life. The deposited lithium metal may react with the electrolyte, generating irreversible byproducts that damage the battery's internal structure and accelerate aging. Simultaneously, the growth of lithium dendrites may penetrate the separator, causing internal short circuits, further reducing battery capacity and shortening its lifespan. Finally, lithium plating poses serious safety hazards. Lithium metal has high chemical reactivity and, under certain conditions, can trigger thermal runaway, leading to battery fires or even explosions, posing a significant threat to the personal safety and property of users. In summary, lithium plating significantly reduces battery capacity, shortens cycle life, and introduces safety risks. Therefore, when using and maintaining batteries, efforts should be made to avoid lithium plating as much as possible to ensure battery safety and performance stability.

[0027] Reference Figure 1 and Figure 2 The cathode sheet in the first embodiment of this utility model includes: a current collector 11, a cathode active material layer 12, a first boundary line 4, a second boundary line 5, a first adhesive tape 14, and a first resistive layer 17. The current collector 11 has a coated section 112 and a blank section 111 adjacent to each other along a first direction, the first direction being the extension direction of the current collector 11. At least one side of the coated section 112 is coated with the cathode active material layer 12, and the blank section 111 is exposed outside the cathode active material layer 12. In existing battery manufacturing, blank sections 111 are usually provided at the head and tail of the cathode sheet 1. Providing blank sections 111 has multiple effects, not only helping to fix the position of the cathode sheet 1 and prevent the active material layer from falling off or shifting during winding, but also helping to improve the mechanical stability of the battery and prevent misalignment during winding. Simultaneously, the process of coating the cathode active material onto the current collector 11 also necessitates the provision of blank sections 111 on the current collector 11.

[0028] The first dividing line 4 is set on the current collector 11 to separate the coated section 112 and the blank section 111. That is, with the first dividing line 4 as the boundary, one side of the first dividing line 4 is the coated section 112, and the other side is the blank section 111. A portion of the first adhesive tape 14 is attached to the side of the cathode active material layer 12 facing away from the current collector 11, and the other portion of the first adhesive tape 14 is attached to the blank section 111 to cover the first dividing line 4. During the winding process of the battery cell, it is difficult to align the tail and head of the cathode sheet 1 and the anode sheet 2. When the two electrodes cannot be aligned, lithium plating is likely to occur, and the active material layer of the anode may even come into direct contact with the current collector 11 on the cathode sheet 1, resulting in a short circuit. Therefore, the first adhesive tape 14 is required.

[0029] The second dividing line 5 is the edge of the first adhesive tape 14 on the cathode active material layer 12. The first resistive layer 17 is disposed on the side of the current collector 11 facing the first adhesive tape 14. The cathode active material layer 12 is coated on the resistive layer. The conductivity of the first resistive layer 17 is lower than that of the current collector 11. The projection of the second dividing line 5 in the second direction lies within the projection of the first resistive layer 17 in the second direction, which is the thickness direction of the cathode sheet 1. Under the cover of the first adhesive tape 14, lithium ions in the cathode active material layer 12 covered by the first adhesive tape 14 cannot directly pass through the first adhesive tape 14 for migration. Therefore, lithium ions under the cover of the first adhesive tape 14 will migrate laterally across the second dividing line 5. This results in a significant increase in the rate of lithium ion release in the area near the second dividing line 5 that is not covered by the first adhesive tape 14, and also increases the total amount of lithium ions released in this area. This leads to the anode sheet 2 not having enough time to absorb excess lithium ions, and the anode sheet 2 in this area not being able to completely absorb lithium ions, resulting in lithium plating in this area. Therefore, a first resistive layer 17 is set in this area, so that the first resistive layer 17 reduces the current in this area by a large resistance, thereby reducing the lithium ion release rate in this area. When the lithium ion release rate in this area is reduced, the anode plate 2 corresponding to this area has sufficient time to absorb lithium ions, thereby effectively avoiding lithium plating in this area.

[0030] According to some embodiments of this utility model, a first resistive layer 17 is disposed in the coating section 112. The first resistive layer 17 has a first end and a second end in a first direction. The first end is located between the first boundary line 4 and the second boundary line 5 in the first direction, and the second end is disposed on the side of the second boundary line 5 opposite to the first boundary line 4 in the first direction. Since no cathode active material layer 12 is disposed on the blank section 111, the first resistive layer 17 disposed on the blank section 111 would reduce the energy density of the battery cell and would not be able to reduce the lithium-ion release rate. Only the current reduced by the first resistive layer 17 in the coating section 112 has the effect of reducing the lithium-ion release rate. Therefore, the first end of the first resistive layer 17 is disposed between the first boundary line 4 and the second boundary line 5. The area where lithium plating occurs is near both sides of the second boundary line 5. Therefore, the area near the side of the second boundary line 5 opposite to the first boundary line 4 also needs to reduce the lithium-ion release rate to avoid lithium plating. Therefore, the second end is disposed on the side of the second boundary line 5 opposite to the first boundary line 4.

[0031] According to some embodiments of this utility model, the distance between the first end and the first dividing line 4 in the first direction is no more than 1 mm, and the distance between the second end and the second dividing line 5 in the first direction is not less than 1 mm and not more than 20 mm. The distance between the first end and the first dividing line 4 is no more than 1 mm, allowing the first resistive layer 17 to more effectively reduce the rate at which lithium ions are released from the cathode active material layer 12 covered by the first adhesive paper 14. Limiting the distance between the second end and the second dividing line 5 ensures that the lithium ion release efficiency in the area near the second dividing line 5 is sufficiently reduced, while also minimizing the impact on the overall charge / discharge rate and energy density of the battery cell.

[0032] According to some embodiments of the present invention, the current collector 11 is provided with a cathode active material layer 12, a first adhesive paper 14 and a first resistive layer 17 on both sides.

[0033] According to some embodiments of this utility model, refer to Figure 3The cathode plate 1 also includes a cathode tab 13, which is fixed to the current collector 11. A groove is formed in the cathode active material layer 12, and the cathode tab 13 is accommodated within the groove. A second adhesive tape 15 covers the side of the cathode tab 13 away from the current collector 11. A second resistive layer 18 is provided on the side of the current collector 11 facing the second adhesive tape 15. The cathode active material layer 12 is coated on the second resistive layer 18. The groove penetrates the cathode active material layer 12 and the second resistive layer 18 along a second direction. The projection of the edge of the second adhesive tape 15 along the second direction lies within the projection of the second resistive layer 18 in the second direction. The conductivity of the second resistive layer 18 is lower than that of the current collector 11. At the location of the cathode tab 13, a second adhesive tape 15 is also provided to cover it for protection. There are several reasons for providing the second adhesive tape 15, one of the more important being to prevent burrs on the cathode tab 13 from piercing the separator 3, thereby preventing a short circuit inside the battery cell. After the second adhesive tape 15 is installed, lithium plating occurs in the edge area of ​​the second adhesive tape 15. The reason for this lithium plating is the same as that for the lithium plating that occurs on the second boundary line 5. Therefore, a second resistive layer 18 is installed to reduce the release rate of lithium ions in the edge area of ​​the second adhesive tape 15, thereby effectively preventing the occurrence of lithium plating. According to some embodiments of this utility model, the second resistive layer 18 is installed along the edge path 6, which is the projection of the edge of the second adhesive tape 15 along the second direction onto the current collector 11. The width of the second resistive layer 18 along the edge path 6 is not less than 3 mm and not more than 20 mm. This ensures that the release efficiency of lithium ions in the area near the edge path 6 is reduced sufficiently, while avoiding the adverse effects caused by an excessively large area where the second resistive layer 18 is installed.

[0034] According to some embodiments of this utility model, refer to Figure 3 A third adhesive strip 16 is provided on the side of the cathode active material layer 12 facing away from the current collector 11. The third adhesive strip 16 corresponds to the anode tab on the anode plate 2. The projection of the anode tab in the second direction lies within the projection of the third adhesive strip 16 in the second direction. A third resistive layer 19 is provided on the side of the current collector 11 facing the third adhesive strip 16. The projection of the third adhesive strip 16 in the second direction lies within the projection of the third resistive layer 19 in the second direction. The conductivity of the third resistive layer 19 is lower than that of the current collector 11. The third adhesive strip 16 is provided to prevent short circuits inside the cell caused by burrs on the anode plate 2 piercing the separator 3. Lithium plating occurs at the edge of the third adhesive strip 16, and the reason for lithium plating is the same as that for lithium plating at the second boundary line 5. Therefore, the third resistive layer 19 is provided to reduce the lithium ion release rate at the edge of the third adhesive strip 16, thereby effectively preventing lithium plating.

[0035] According to some embodiments of this utility model, the distance between the edge of the third adhesive tape 16 projected along the second direction and the edge of the third resistive layer 19 projected along the second direction is not less than 1 mm. This avoids the adverse effects caused by an excessively large area where the second resistive layer 18 is disposed.

[0036] According to some embodiments of this utility model, the material of the first resistive layer 17 is a conductive adhesive coating, a conductive nano-coating, or a lithium iron phosphate coating. The conductive nano-coating is a nano-coating composed of a mixture of ceramic and a conductive agent. The third resistive layer 19 and the second resistive layer 18 can both be made of the same material as the first resistive layer 17. All three can be made of materials with a conductivity lower than that of the current collector 11.

[0037] The battery according to the second aspect of the present invention includes a cathode sheet 1 as described in any of the above embodiments.

[0038] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model 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 utility model.

Claims

1. A cathode plate, characterized in that, include: A current collector is provided with a coated section and a blank section adjacent to each other along a first direction, the first direction being the extension direction of the current collector. At least one side of the coated section is coated with a cathode active material layer, and the blank section is exposed outside the cathode active material layer. A first dividing line is provided on the current collector to separate the coated section and the blank section; A first adhesive tape, a portion of which is attached to the side of the cathode active material layer facing away from the current collector, and another portion of which is attached to the blank section to cover the first dividing line; The second dividing line is along the first direction, and the second dividing line is the edge of the first adhesive paper on the cathode active material layer; A first resistive layer is disposed on the side of the current collector facing the first adhesive paper. The cathode active material layer is coated on the first resistive layer. The conductivity of the first resistive layer is lower than that of the current collector. The projection of the second dividing line in the second direction is located within the projection of the first resistive layer in the second direction. The second direction is the thickness direction of the cathode sheet.

2. The cathode sheet according to claim 1, characterized in that, The first resistive layer is disposed in the coating section. The first resistive layer has a first end and a second end in the first direction. The first end is located between the first boundary line and the second boundary line in the first direction, and the second end is disposed on the side of the second boundary line away from the first boundary line in the first direction.

3. The cathode sheet according to claim 2, characterized in that, The distance between the first end and the first dividing line in the first direction is no more than 1 mm, and the distance between the second end and the second dividing line in the first direction is not less than 1 mm and not more than 20 mm.

4. The cathode sheet according to claim 1, characterized in that, The current collector is provided with the cathode active material layer, the first adhesive paper and the first resistive layer on both sides.

5. The cathode sheet according to claim 4, characterized in that, The cathode sheet further includes a cathode tab fixed to the current collector. A groove is formed on the cathode active material layer, and the cathode tab is accommodated in the groove. A second adhesive tape covers the side of the cathode tab away from the current collector. A second resistive layer is provided on the side of the current collector facing the second adhesive tape. The cathode active material layer is coated on the second resistive layer. The groove penetrates the cathode active material layer and the second resistive layer along a second direction. The projection of the edge of the second adhesive tape along the second direction is located within the projection of the second resistive layer in the second direction. The conductivity of the second resistive layer is lower than that of the current collector.

6. The cathode sheet according to claim 5, characterized in that, The second resistive layer is disposed along an edge path, which is the projection of the edge of the second adhesive paper onto the current collector along the second direction. The width of the second resistive layer disposed along the edge path is not less than 3 mm and not more than 20 mm.

7. The cathode sheet according to claim 1, characterized in that, A third adhesive strip is provided on the side of the cathode active material facing away from the current collector. The third adhesive strip corresponds to the anode tab on the anode plate. The projection of the anode tab in the second direction is located within the projection of the third adhesive strip in the second direction. A third resistive layer is provided on the side of the current collector facing the third adhesive strip. The cathode active material layer is coated on the third resistive layer. The projection of the third adhesive strip along the second direction is located within the projection of the third resistive layer along the second direction. The conductivity of the third resistive layer is lower than that of the current collector.

8. The cathode sheet according to claim 7, characterized in that, The distance between the edge of the third adhesive tape projected along the second direction and the edge of the third resistive layer projected along the second direction is not less than 1 mm and not more than 20 mm.

9. The cathode sheet according to claim 1, characterized in that, The material of the first resistive layer is a conductive adhesive coating, a conductive nano coating, or a lithium iron phosphate coating.

10. A battery cell, characterized in that, Includes the cathode plate according to any one of claims 1-9.

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