Collecting structure, positive plate and battery monomer

Abstract

The utility model relates to the technical field of batteries, and provides a current collecting structure, a positive plate and a battery monomer. The current collecting structure comprises a current collector and a bottom coating arranged on at least one side of the current collector, the bottom coating comprises a first coating and a second coating, and the second coating is located on the edge of the current collector; wherein the conductivity of the second coating is lower than that of the first coating, and / or the thickness of the second coating is larger than that of the first coating. Therefore, the problem of lithium precipitation at the edge of the negative plate can be effectively improved.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a current collecting structure, a positive electrode sheet and a battery cell. Background Art

[0002] Lithium-ion batteries are widely used in various electronic products, such as mobile phones, electric vehicles, energy storage power stations, etc. Among them, electric vehicles or energy storage power stations have high requirements for the processing performance of lithium-ion batteries, the consistency of battery cells, the cycle life and the safety performance.

[0003] At present, during the charge and discharge process of lithium-ion battery cells, the current density in the edge region is large, and lithium deposition is more likely to occur. After lithium ions are deposited on the negative electrode sheet, side reactions will occur with the electrolyte, further deteriorating the battery cell, shortening the life of the battery cell, and possibly triggering safety risks. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a current collecting structure, a positive electrode sheet and a battery cell, aiming to solve the technical problem that lithium deposition easily appears at the edge of the existing lithium-ion battery cell.

[0005] In a first aspect, the present application provides a current collecting structure, which includes a current collector and a bottom coating provided on at least one side of the current collector. The bottom coating includes a first coating and a second coating, and the second coating is located at the edge of the current collector; wherein, the conductivity of the second coating is lower than that of the first coating, and / or, the thickness of the second coating is greater than that of the first coating.

[0006] The beneficial effects of the current collecting structure provided by the utility model are as follows: It should be noted that generally, the electrode sheet includes a current collector and an active material layer coated on the current collector. Generally, in order to improve the adhesion between the current collector and the active material layer and reduce the probability of powder falling off, a bottom coating is usually provided between the current collector and the active material layer, that is, the bottom coating is first coated on the current collector, and then the active material layer is coated on the bottom coating.

[0007] In the present application, by configuring the conductivity of the second coating located at the edge of the current collector to be lower than that of the first coating, the lithium-ion reaction impedance of the positive electrode active material layer coated on the second coating can be increased, thereby improving the problem of lithium deposition at the edge of the negative electrode sheet of the battery cell applying this current collector structure. It is worth mentioning that compared with directly improving the positive electrode active material layer, that is, configuring the conductivity of the positive electrode active material layer at the edge to be lower than that of the positive electrode active material layer in the middle, this current collector structure has the following advantages. First, while improving the problem of lithium deposition at the edge of the negative electrode sheet, it can increase the adhesion between the current collector and the positive electrode active material layer and reduce the probability of powder falling off. It can be seen that this current collector structure can improve both problems simultaneously. Second, since there is no need to change the positive electrode active material layer, while improving the lithium deposition problem, the original performance of the positive electrode active material layer is ensured.

[0008] In addition, by configuring the thickness of the second coating to be greater than that of the first coating, the thickness of the positive electrode active material layer coated on the surface of the second coating will be smaller than the thickness of the positive electrode active material layer coated on the surface of the first coating, thereby reducing the amount of lithium ions escaping from the edge and further improving the problem of lithium deposition at the edge during the use of the battery cell applying this current collector structure. Moreover, the above design can more easily achieve the edge thinning effect during the electrode coating process.

[0009] Optionally, the adhesion of the first coating is greater than that of the second coating.

[0010] Optionally, the first coating includes a first conductive agent, and the first conductive agent includes at least one of a dot-shaped conductive agent, a linear conductive agent, and a flake-shaped conductive agent.

[0011] Optionally, the second coating includes a second conductive agent, and the second conductive agent includes at least one of a dot-shaped conductive agent, a linear conductive agent, and a flake-shaped conductive agent.

[0012] Optionally, the dot-shaped conductive agent includes at least one of carbon black and Super-P.

[0013] Optionally, the linear conductive agent includes at least one of carbon nanotubes and carbon fibers.

[0014] Optionally, the flake-shaped conductive agent includes graphene.

[0015] Optionally, the thickness of the second coating is between 2.5 microns and 3 microns.

[0016] Optionally, the thickness of the first coating is between 0.9 microns and 1.2 microns.

[0017] Optionally, the width of the second coating is 8 - 20 mm.

[0018] Optionally, there are two second coatings, and the first coating is located between the two second coatings.

[0019] Optionally, the second coating is disposed around the first coating.

[0020] In a second aspect, the present application provides a positive electrode sheet, which includes a positive electrode active material layer and the current collecting structure described above. Among them, the positive electrode active material layer is provided on the surface of the first coating away from the current collector and the surface of the second coating away from the current collector.

[0021] The beneficial effect of the positive electrode sheet provided by the present utility model is that: due to the adoption of the above-mentioned current collecting structure, the problem of lithium deposition at the edge of the negative electrode sheet cooperating therewith can be improved.

[0022] In a third aspect, the present application provides a battery cell, including the positive electrode sheet described above.

[0023] The beneficial effect of the battery cell provided by the present utility model is that: due to the adoption of the above-mentioned positive electrode sheet, the service life of the battery cell can be extended. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a cross-sectional view of the current collecting structure provided by the embodiment of the present utility model;

[0026] Figure 2 It is a schematic structural view of the current collecting structure provided by the embodiment of the present utility model;

[0027] Figure 3 It is another schematic structural view of the current collecting structure provided by the embodiment of the present utility model.

[0028] Among them, the reference numerals in the drawings:

[0029] 100, current collecting structure; 10, current collector; 20, bottom coating;

[0030] 21, first coating; 22, second coating. Detailed Embodiments

[0031] The following will describe in detail the embodiments of the present utility model. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present utility model, and should not be construed as limiting the present utility model.

[0032] Throughout the specification, reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, the phrases "in one embodiment" or "in some embodiments" appearing throughout the specification do not necessarily refer to the same embodiment. Additionally, in one or more embodiments, the particular features, structures, or characteristics may be combined in any suitable manner.

[0033] In the description of the present utility model, it should be understood that the orientation or positional relationships indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present utility model.

[0034] Furthermore, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0035] In the present utility model, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0036] Please refer to Figures 1 to 3 , and now the current collecting structure 100, the positive electrode sheet, and the battery cell in the embodiments of the present utility model will be described.

[0037] Please refer to Figures 1 to 3 , the present application provides a current collecting structure 100, which includes a current collector 10 and a bottom coating 20 disposed on at least one side of the current collector 10. The bottom coating 20 includes a first coating 21 and a second coating 22, and the second coating 22 is located at the edge of the current collector 10; wherein, the conductivity of the second coating 22 is lower than that of the first coating 21. Specifically, the bottom coating 20 is disposed on at least one side in the thickness direction of the current collector 10.

[0038] It should be noted that generally, the electrode sheet includes a current collector 10 and an active material layer coated on the current collector 10. Generally, in order to improve the adhesion between the current collector 10 and the active material layer and reduce the probability of powder falling off, a base coating 20 is usually provided between the current collector 10 and the active material layer, that is, the base coating 20 is first coated on the current collector 10, and then the active material layer is coated on the base coating 20. The phenomenon of powder falling off will lead to problems such as poor Hipot in the process and abnormal self-discharge of the battery cell, affecting the process yield and the normal use of the battery cell. As for the reason of powder falling off, the electrode sheet needs to be slit to obtain an electrode sheet with a smaller width.

[0039] In the present application, by configuring the conductivity of the second coating 22 at the edge of the current collector 10 to be lower than that of the first coating 21, the lithium-ion reaction impedance of the positive electrode active material layer coated on the second coating 22 can be increased, thereby improving the problem of lithium deposition at the edge of the negative electrode sheet of the battery cell applying the current collector structure 100.

[0040] It is worth mentioning that compared with directly improving the positive electrode active material layer, that is, configuring the conductivity of the positive electrode active material layer at the edge to be lower than that of the positive electrode active material layer in the middle, the current collector structure 100 has the following advantages. First, while improving the problem of lithium deposition at the edge of the negative electrode sheet, it can improve the adhesion between the current collector 10 and the positive electrode active material layer and reduce the probability of powder falling off. It can be seen that the current collector structure 100 can improve both problems at the same time. Second, since there is no need to change the positive electrode active material layer, while improving the problem of lithium deposition, the original performance of the positive electrode active material layer is guaranteed.

[0041] It can be understood that the current collector 10 has opposite two sides in its own thickness direction. The base coating 20 can be provided only on one side, or on both sides, which is not limited herein. In this embodiment, the base coating 20 is provided on both sides of the current collector 10 in the thickness direction.

[0042] In another embodiment of the present application, the adhesion of the first coating 21 is greater than that of the second coating 22. Specifically, the first coating 21 includes a first binder, and the mass ratio of the first binder in the first coating 21 is A1%, and the second coating 22 includes a second binder, and the mass ratio of the second binder in the second coating 22 is A2%, satisfying the relationship: A1 < A2. In this embodiment, by adjusting the proportion of the binder in the coating, the adhesion of the first coating 21 is made greater than that of the second coating 22, so that the conductivity of the second coating 22 at the edge of the current collector 10 is lower than that of the first coating 21, increasing the resistance of the diaphragm at the edge of the current collector 10, and further increasing the reaction impedance of lithium ions in the corresponding region, effectively improving the problem of lithium deposition at the edge of the negative electrode sheet. In addition, since the mass ratio of the second binder in the second coating 22 is higher, the problem of powder falling off after the electrode sheet is slit can be improved.

[0043] It can be seen that in the above embodiment, by only increasing the proportion of the second binder in the second coating 22, the problem of lithium deposition on the negative electrode sheet can be improved while the problem of easy powder falling off after slitting the positive electrode sheet can be improved.

[0044] In some embodiments, A1 is 35 to 45, that is, the mass ratio of the first binder in the first coating 21 is 35% to 45%. As an example, the mass ratio of the first binder in the first coating 21 can be 35%, 37%, 39%, 41%, 43%, 45% or the range between any two of the foregoing values.

[0045] In some embodiments, A2 is 60 to 70, that is, the mass ratio of the second binder in the second coating 22 is 60% to 70%. As an example, the mass ratio of the second binder in the second coating 22 can be 60%, 62%, 64%, 66%, 68%, 70% or the range between any two of the foregoing values.

[0046] In some embodiments, the first coating 21 includes a first conductive agent, and the mass ratio of the first conductive agent in the first coating 21 is B1%, and the second coating 22 includes a second conductive agent, and the mass ratio of the second conductive agent in the second coating 22 is B2%, satisfying the relationship: B1 > B2. Such an arrangement is made to make the conductivity of the second coating 22 lower than that of the second coating 22.

[0047] In some embodiments, the first conductive agent includes at least one of a dot-shaped conductive agent, a linear conductive agent, and a flake-shaped conductive agent.

[0048] In some embodiments, the second conductive agent includes at least one of a dot-shaped conductive agent, a linear conductive agent, and a flake-shaped conductive agent.

[0049] Among them, the conductivity of the flaky conductive agent is better than that of the linear conductive agent, and the conductivity of the linear conductive agent is better than that of the dot-shaped conductive agent. The types of the first conductive agent and the second conductive agent are not particularly limited in this application, that is, the types of the first conductive agent and the second conductive agent may be the same or different. For example, both the first conductive agent and the second conductive agent can adopt dot-shaped conductive agents. Again, both the first conductive agent and the second conductive agent can adopt linear conductive agents. As long as the conductivity of the second coating 22 is lower than that of the first coating 21.

[0050] In some embodiments, the dot-shaped conductive agent includes at least one of carbon black and Super-P.

[0051] In some embodiments, the linear conductive agent includes at least one of carbon nanotubes and carbon fibers.

[0052] In some embodiments, the flaky conductive agent includes graphene.

[0053] In this embodiment, the second conductive agent adopts a dot-shaped conductive agent, and the first conductive agent adopts a composite conductive agent, which is a combination of two or three of the dot-shaped conductive agent, the linear conductive agent, and the flaky conductive agent. Specifically, in this embodiment, the first conductive agent adopts a combination of a dot-shaped conductive agent and a linear conductive agent. With such a setting, while achieving that the conductivity of the second coating 22 is lower than that of the first coating 21, the production cost is reduced.

[0054] When A1 and A2 are equal, by changing the proportion of the conductive agent in the coating and changing the type of the conductive agent, the resistance of the diaphragm at the edge of the current collector 10 can also be increased.

[0055] In some embodiments, the thickness of the second coating 22 is between 2.5 microns and 3 microns. As an example, the thickness of the second coating 22 can be 2.5 microns, 2.6 microns, 2.7 microns, 2.8 microns, 2.9 microns, 3 microns, or the range between any two of the foregoing values.

[0056] In some embodiments, the thickness of the first coating 21 is between 0.9 microns and 1.2 microns. As an example, the thickness of the first coating 21 can be 0.9 microns, 1 micron, 1.1 microns, 1.2 microns, or the range between any two of the foregoing values.

[0057] Limiting the thicknesses of the first coating 21 and the second coating 22 within the above ranges, on the one hand, avoids excessive thickness, resulting in too much decrease in the energy density of the battery. On the other hand, avoids too small thickness, resulting in poor improvement effect of lithium deposition at the edge of the negative electrode sheet.

[0058] In some embodiments, the width of the second coating 22 is 8 to 20 mm. As an example, the width of the second coating 22 can be 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, or a range between any two of the foregoing values. With such a setting, on the one hand, it is possible to avoid excessive width of the second coating 22, which may cause excessive decrease in the energy density of the battery. On the other hand, it is possible to avoid too small a thickness, which may result in poor improvement effect of lithium deposition at the edge of the negative electrode sheet.

[0059] In some embodiments, please refer to Figure 2 , two second coatings 22 are provided, and the first coating 21 is located between the two second coatings 22. Specifically, the two second coatings 22 are respectively provided at both ends of the current collector 10 in its own width direction. The two second coatings 22 are both in contact with the first coating 21, and both the first coating 21 and the second coating 22 extend along the length direction of the current collector 10. This current collection structure 100 is suitable for producing wound battery cells.

[0060] It can be understood that the electrical conductivity of the two second coatings 22 can be the same or different, as long as the electrical conductivity of both second coatings 22 is lower than that of the first coating 21, which is not limited herein. In this embodiment, it is preferred that the electrical conductivity of the two second coatings 22 is the same. In this way, the variety of slurries can be reduced, and the production cost and production difficulty can be lowered.

[0061] In some embodiments, please refer to Figure 3 , the second coating 22 is disposed to surround the first coating 21. This current collection structure 100 is suitable for producing laminated battery cells, and the electrode sheets of laminated battery cells are usually square. At this time, the second coating 22 is disposed to surround the current collector 10 at the edge, and the first coating 21 is disposed inside the second coating 22, and the inner circle of the first coating 21 is in contact with the second coating 22.

[0062] It can be understood that the current collector 10 can be a metal foil or a composite current collector 10. Among them, since this current collection structure 100 is applicable to the positive electrode sheet, the metal foil can be an aluminum foil, and the composite current collector 10 can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector 10 can be formed by forming a metal material, such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0063] The present application also provides another current collector structure 100, which includes a current collector 10 and a bottom coating 20 provided on at least one side of the current collector 10. The bottom coating 20 includes a first coating 21 and a second coating 22. The second coating 22 is located at the edge of the current collector 10. Among them, the thickness of the second coating 22 is greater than that of the first coating 21.

[0064] In the above current collector structure 100, by configuring the thickness of the second coating 22 to be greater than that of the first coating 21, the thickness of the positive electrode active material layer coated on the surface of the second coating 22 will be smaller than the thickness of the positive electrode active material layer coated on the surface of the first coating 21, thereby reducing the amount of lithium ions escaping from the edge, and further improving the problem of lithium plating at the edge during the use of the battery cell with this current collector structure 100. Moreover, the above design can more easily achieve the edge thinning effect during the coating process of the electrode sheet. This is because, generally, during the coating process, since the slurry is liquid, the slurry at the edge of the bottom coating 20 will volatilize first, and the liquid slurry in the middle will flow towards the edge, resulting in the edge of the bottom coating 20 bulging. The bulging of the edge of the bottom coating 20 will cause abnormalities in subsequent preparation. The prior art usually improves the above problem by reducing the coating amount in the edge area. In the current collector structure 100, since the thickness of the second coating 22 is greater than that of the first coating 21, there is no need to deliberately thin the edge.

[0065] The present application also provides another current collector structure 100, which includes a current collector 10 and a bottom coating 20 provided on at least one side of the current collector 10. The bottom coating 20 includes a first coating 21 and a second coating 22. The second coating 22 is located at the edge of the current collector 10. Among them, the conductivity of the second coating 22 is lower than that of the first coating 21, and the thickness of the second coating 22 is greater than that of the first coating 21. With such a setting, the problem of lithium plating at the edge of the negative electrode sheet can be improved to a greater extent.

[0066] After coating the positive electrode active material layer on the first coating 21 and the second coating 22 of the above current collector structure 100, a positive electrode sheet is made. The positive electrode sheet, negative electrode sheet and separator are prepared into a core by winding or laminating. After the core undergoes preheating and hot pressing processes, the electrode sheets and the separator are closely adhered. After welding with a connecting piece, laser welding of the case cover, baking, liquid injection, formation, welding of the sealing nail, and grading, a battery cell is obtained.

[0067] The present application also provides a positive electrode sheet, which includes a positive electrode active material layer and at least one of the above current collector structures 100. Among them, a positive electrode active material layer is provided on the surface of the first coating 21 away from the current collector 10 and the surface of the second coating 22 away from the current collector 10. Since the above at least one current collector structure 100 is adopted in this positive electrode sheet, the problem of lithium plating at the edge of the negative electrode sheet used in cooperation with this positive electrode sheet can be effectively improved.

[0068] The present application also provides a battery cell, which includes the above-mentioned positive electrode sheet. Since the battery cell adopts the above-mentioned positive electrode sheet, the service life of the battery cell can be extended. In addition, it can effectively improve the lithium plating window of the battery cell and enhance the fast charging ability of the battery cell.

[0069] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A current collecting structure, characterized in that: It includes a current collector (10) and a bottom coating (20) provided on at least one side of the current collector (10). The bottom coating (20) includes a first coating (21) and a second coating (22), and the second coating (22) is located at the edge of the current collector (10); wherein, the conductivity of the second coating (22) is lower than that of the first coating (21); and / or, the thickness of the second coating (22) is greater than that of the first coating (21).

2. The current collector structure according to claim 1, characterized in that: The adhesion of the first coating (21) is greater than that of the second coating (22).

3. The current collecting structure according to claim 1, wherein: the first coating (21) includes a first conductive agent, and the first conductive agent includes at least one of a dot-shaped conductive agent, a linear conductive agent, and a flake-shaped conductive agent; and / or, the second coating (22) includes a second conductive agent, and the second conductive agent includes at least one of a dot-shaped conductive agent, a linear conductive agent, and a flake-shaped conductive agent.

4. The current collecting structure according to claim 3, wherein: the dot-shaped conductive agent includes at least one of carbon black and Super-P; and / or, the linear conductive agent includes at least one of carbon nanotubes and carbon fibers; and / or, the flake-shaped conductive agent includes graphene.

5. The current collecting structure according to claim 1, wherein: the thickness of the second coating (22) is between 2.5 microns and 3 microns; and / or, the thickness of the first coating (21) is between 0.9 microns and 1.2 microns.

6. The current collector structure according to claim 1, characterized in that: The width of the second coating (22) is 8 - 20 mm.

7. The current collector structure according to claim 1, wherein: There are two second coatings (22), and the first coating (21) is located between the two second coatings (22).

8. The current collection structure according to claim 1, wherein: The second coating (22) is arranged to surround the first coating (21).

9. A positive electrode sheet, characterized in that: It includes a positive electrode active material layer and the current collecting structure (100) according to any one of claims 1 to 8. Among them, the positive electrode active material layer is provided on the surface of the first coating (21) away from the current collector (10) and the surface of the second coating (22) away from the current collector (10).

10. A battery cell, characterized in that: It includes the positive electrode sheet according to claim 9.

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