Negative plate and battery monomer with same

Abstract

The utility model provides a negative pole piece and a battery monomer with the same. The negative pole piece comprises a current collector, a positive pole piece and a negative pole piece, at least one side surface of the current collector is coated with the conductive coating, and the resistance of the conductive coating is reduced in the direction from the two ends of the current collector to the middle of the current collector. According to the negative plate disclosed by the utility model, the resistance in the middle of the current collector is reduced, and the conductivity of the middle of the current collector can be improved, so that the conductivity of the whole negative plate can be improved, the fast charging performance of a battery monomer can be ensured, and meanwhile, the energy density of the battery monomer can be improved; and the charging and discharging cycle performance of the battery monomer can also be improved.

Description

Technical Field

[0001] The utility model relates to the technical field of battery monomer manufacturing, in particular to a negative electrode sheet and a battery monomer having the same. Background Art

[0002] In order to improve the energy density of battery cells in existing solutions, the surface density of the negative electrode sheet is usually increased. This causes the transmission path of ions inside the negative electrode sheet to become longer and the flow rate of ions inside the negative electrode sheet to become slower, thereby causing the conductivity of the negative electrode sheet to decrease, thereby reducing the cycle performance of the battery cell charge and discharge. Utility Model Content

[0003] The utility model aims to solve at least one of the technical problems existing in the prior art. To this end, the utility model provides a negative electrode sheet, which can improve the conductivity.

[0004] The utility model also provides a battery monomer having the negative electrode sheet.

[0005] According to the negative electrode sheet of the embodiment of the utility model, it includes: a current collector; a conductive coating, wherein the conductive coating coats at least one side surface of the current collector, and the resistance of the conductive coating decreases in the direction from the two ends to the middle of the current collector.

[0006] According to the negative electrode sheet of the utility model, the resistance in the middle of the current collector is reduced, which can improve the conductivity of the middle of the current collector, thereby improving the conductivity of the entire negative electrode sheet, and further ensuring the fast charging performance of the battery cell. At the same time, it can improve the energy density of the battery cell and the charge and discharge cycle performance of the battery cell.

[0007] According to some embodiments of the present invention, the conductive coating includes a first region and two second regions, the first region is disposed between the two second regions, and the resistance of the first region is smaller than the resistance of the second region.

[0008] According to some optional embodiments of the present invention, in the length direction of the current collector, the coating length of the first region is not less than the sum of the coating lengths of the two second regions.

[0009] According to some embodiments of the present invention, the conductive coating includes: a first coating and a second coating, the first coating and the second coating are stacked in a thickness direction of the current collector, and the first coating is located between the second coating and the current collector.

[0010] According to some optional embodiments of the present invention, in the thickness direction of the current collector, the resistance of the second coating layer is not less than the resistance of the first coating layer.

[0011] According to some embodiments of the present invention, the first coating layer includes a first graphite material, the second coating layer includes a second graphite material, and the size of graphite particles in the first graphite material is smaller than the size of graphite particles in the second graphite material.

[0012] According to some optional embodiments of the present invention, the specific surface area of ​​the second graphite material is not less than the specific surface area of ​​the first graphite material.

[0013] According to some embodiments of the present invention, the particle size of the first graphite material satisfies the relationship: (D90-D10) / D50≤1.2.

[0014] According to some embodiments of the present invention, the ratio of the surface density of the first coating layer to that of the second coating layer is 1:9-9:1.

[0015] The battery cell according to the embodiment of the second aspect of the utility model comprises the negative electrode sheet according to the first aspect of the utility model.

[0016] According to the battery cell of the utility model, by setting the negative electrode sheet of the above-mentioned first aspect embodiment, the resistance in the middle position of the current collector is reduced, which can improve the conductivity of the middle position of the current collector, thereby improving the conductivity of the entire negative electrode sheet, and further ensuring the fast charging performance of the battery cell. At the same time, the energy density of the battery cell can be improved, and the charge and discharge cycle performance of the battery cell can also be improved.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of a negative electrode sheet according to an embodiment of the first aspect of the utility model.

[0019] Reference numerals:

[0020] 100. Negative electrode sheet;

[0021] 10. Current collector;

[0022] 20. Conductive coating; 21. First coating; 22. Second coating;

[0023] 201, first area; 202, second area. DETAILED DESCRIPTION

[0024] The embodiments of the present invention are described in detail below, and 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 to be used to explain the present invention, and should not be construed as limiting the present invention.

[0025] Please refer to the following Figure 1 A negative electrode sheet 100 according to an embodiment of the present invention is described.

[0026] Reference Figure 1 According to the negative electrode sheet 100 of the embodiment of the utility model, the negative electrode sheet 100 includes: a current collector 10 and a conductive coating 20, wherein the conductive coating 20 coats at least one side surface of the current collector 10, that is, the conductive coating 20 can coat one side surface of the current collector 10, and the conductive coating 20 can also coat both sides of the current collector 10. Figure 1 The resistance of the conductive coating 20 decreases from the left end and the right end of the current collector 10 shown in the figure to the middle. The reduced resistance of the conductive coating 20 can promote the insertion and extraction of ions in the middle of the conductive coating 20, thereby improving the charge and discharge performance of the battery cell.

[0027] When the battery cell is working, electrons flow in the negative electrode sheet 100, and ions flow between the electrolyte and the negative electrode sheet 100. For example, if the ions are lithium ions, the lithium ions can be embedded in the first coating 21 and the second coating 22 from the electrolyte, and the lithium ions can also be released from the first coating 21 and the second coating 22 to the electrolyte.

[0028] When charging a battery cell, ions are embedded into the conductive coating 20 through the electrolyte, and electrons flow from the left and right ends of the negative electrode sheet 100 toward the middle of the current collector 10. When the electrons move to the middle of the current collector 10, the attraction of the electrons in the middle to the ions is insufficient due to the transmission distance, which affects the embedding speed of the ions in the middle toward the depth of the conductive coating 20, thereby affecting the charging speed of the battery cell. Similarly, it also affects the escape speed of the ions in the middle away from the negative electrode sheet 100, thereby affecting the discharge speed of the battery cell.

[0029] The negative electrode sheet 100 of the utility model reduces the resistance in the middle of the current collector 10. The reduced resistance can increase the flow rate of electrons, which can improve the conductivity of the middle of the current collector 10 and effectively improve the conductivity of the current collector 10. At the same time, by setting the conductive coating 20 in a step-differentiated manner, it is convenient for electrons to enter the conductive coating 20 and combine with ions, thereby ensuring the fast charging performance of the battery cell. Furthermore, it can also increase the speed of ions escaping from the middle of the current collector 10, thereby improving the charge and discharge cycle performance of the battery cell. In addition, the conductive coating 20 can effectively increase the energy density of the negative electrode sheet 100, thereby ensuring the storage capacity of the battery cell.

[0030] According to the negative electrode sheet 100 of the embodiment of the utility model, the resistance in the middle of the current collector 10 is reduced, which can improve the conductivity of the middle of the current collector 10, thereby improving the conductivity of the entire negative electrode sheet 100, thereby ensuring the fast charging performance of the battery cell, and at the same time, improving the energy density of the battery cell, and also improving the charge and discharge cycle performance of the battery cell.

[0031] According to some embodiments of the present invention, referring to Figure 1 The conductive coating 20 includes a first region 201 and two second regions 202. The first region 201 is disposed between the two second regions 202, and the resistance of the first region 201 is less than the resistance of the second region 202. Therefore, this region division form has a reasonable structure, thereby ensuring the charge and discharge performance of the battery cell.

[0032] For example, Figure 1 As shown, the two second regions 202 are respectively disposed at the left and right ends of the current collector 10 , and one first region 201 is disposed between the two second regions 202 .

[0033] According to some embodiments of the present invention, referring to Figure 1 , in the length direction of the current collector 10 (eg Figure 1 In the left and right directions shown in FIG. 2 , the coating length of the first region 201 is not less than the sum of the coating lengths of the two second regions 202. Thus, limiting the coating length of the first region 201 can ensure that lithium ions in the middle can be quickly embedded and released, thereby ensuring the charging and discharging speed of the battery cell.

[0034] According to some embodiments of the present invention, referring to Figure 1 The conductive coating 20 includes: a first coating 21 and a second coating 22. The first coating 21 and the second coating 22 are arranged in a thickness direction of the current collector 10 (eg Figure 1The first coating 21 is located between the second coating 22 and the current collector 10. Thus, the double-layer conductive coating 20 can effectively increase the rate at which ions flow from the second coating 22 to the first coating 21, shorten the ion transmission time, and thus ensure the fast charging performance of the battery cell.

[0035] According to some optional embodiments of the present invention, referring to Figure 1 , in the thickness direction of the current collector 10 (eg Figure 1 In the vertical direction of the current collector 10 shown in FIG. 1 ), the resistance of the second coating 22 is not less than the resistance of the first coating 21. At a position close to the surface of the current collector 10, the ion embedding ability is reduced. Therefore, reducing the resistance of the first coating 21 can facilitate the embedding of ions, thereby increasing the flow rate of ions in the negative electrode sheet 100.

[0036] According to some embodiments of the present invention, referring to Figure 1 The first coating 21 includes a first graphite material, and the second coating 22 includes a second graphite material. The graphite particles in the first graphite material are smaller than the graphite particles in the second graphite material. As a result, both the first graphite material and the second graphite material have a layered structure, and ions can be embedded in the first graphite material and the second graphite material, which serve as storage and release sites for ions during the charge and discharge process, thereby realizing energy storage and conversion of the battery cell. At the same time, the second graphite material has a large particle roughness, which can further facilitate the embedding and release of ions in the second coating 22, thereby increasing the charge and discharge speed of the battery cell.

[0037] For example, the first graphite material is a single particle material, and the carbonization coverage range is 0-100%, preferably, the carbonization coverage range is 100%, and the second graphite material is a mixture of single particles and secondary particles (rough), wherein the mixing ratio of single particles to secondary particles ranges from 1:9 to 9:1, and the single particle carbonization coverage ranges from 0-100%, preferably, the single particle carbonization coverage range is 100%, and the secondary particle carbonization coverage ranges from 0-100%, preferably, the secondary particle carbonization coverage range is 100%.

[0038] Furthermore, if Figure 1 As shown, the first coating 21 includes: 94%-97% of the first graphite material, 0.5%-1.5% of the conductive agent, 0.2%-1.5% of the thickener, and 1%-3% of the adhesive, and the second coating 22 includes: 94%-97% of the second graphite material, 0.5%-1.5% of the conductive agent, 0.2%-1.5% of the thickener, and 1%-3% of the adhesive. Thus, the conductive agent can enhance the conductivity of the first coating and the second coating, and the thickener can adjust the viscosity and rheological properties of the first coating and the second coating, so that the slurry has suitable construction performance.

[0039] Preferably, the conductive agent includes one or more of conductive carbon black, conductive graphite, carbon nanotubes, graphene, carbon fiber, and acetylene black, so that the conductive effect of the conductive agent can be guaranteed; the thickener includes one or more of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose, so that the thickening effect of the thickener can be guaranteed; the binder includes any one of polyvinylidene fluoride, polyacrylonitrile, styrene-butadiene rubber, polyacrylic acid or polyacrylate, or a combination of at least two of them, so that the bonding effect of the binder can be guaranteed.

[0040] Furthermore, if Figure 1 As shown, the content of the conductive agent in the first coating 21 is not less than that in the second coating 22, and the content of the conductive agent in the first region 201 is not less than that in the second region 202. Thus, increasing the content of the conductive agent in the first coating 21 can effectively increase the flow rate of ions in the negative electrode sheet 100 at a position close to the surface of the current collector 10, and at the same time, increasing the content of the conductive agent in the first region 201 can facilitate the flow of ions in the first region 201, thereby further increasing the flow rate of ions in the negative electrode sheet 100.

[0041] Furthermore, if Figure 1 As shown, the content of the binder in the second coating 22 is not greater than the content of the binder in the first coating 21, and the content of the binder in the first region 201 is not greater than the content of the binder in the second region 202. Therefore, under the premise of ensuring the bonding effect of the second coating 22, the content of the binder in the second coating 22 can be reduced, and the content of other substances, such as the content of the conductive agent, can be increased, so that the conductive performance of the second coating 22 can be effectively adjusted. At the same time, under the premise of ensuring the bonding effect of the first region 201, the content of the binder in the first region 201 can be reduced, and the content of other substances, such as the content of the conductive agent, can be increased, so that the conductive performance of the first region 201 can be effectively adjusted.

[0042] According to some embodiments of the present invention, Figure 1 As shown, the specific surface area of ​​the second graphite material is not less than the specific surface area of ​​the first graphite material. The specific surface area is the total area per unit mass of the material. Therefore, the larger the specific surface area, the more contact areas between the ions and the second graphite material, which can further facilitate the embedding of the ions in the second graphite material, thereby improving the fast charging performance of the battery cell.

[0043] According to some embodiments of the present invention, referring to Figure 1, the particle size of the first graphite material satisfies the relationship: (D90-D10) / D50≤1.2. D90 is the volume content of particles smaller than this particle size accounting for 90% of all particles, D10 is the volume content of particles smaller than this particle size accounting for 10% of all particles, and D50 is the median particle size. Therefore, limiting the particle size of the first graphite material can make ions better embedded and released in the first graphite material, thereby ensuring the charge and discharge performance of the battery cell.

[0044] According to some embodiments of the present invention, referring to Figure 1 , the ratio of the surface density of the first coating 21 to the second coating 22 is 1:9-9:1. The surface density is the mass per unit area. Therefore, by limiting the surface density ratio of the first coating 21 to the second coating 22, the energy density of the negative electrode sheet 100 at different positions can be effectively adjusted, and the storage performance of the battery cell can be adjusted. Preferably, the ratio of the surface density of the first coating 21 to the second coating 22 is 5:5, so that the energy density of the first coating and the second coating can be equalized, which is convenient for processing the negative electrode sheet.

[0045] According to the battery cell of the second embodiment of the utility model, Figure 1 , including the negative electrode sheet 100 of the first aspect of this embodiment.

[0046] According to the battery cell of the embodiment of the utility model, by setting the negative electrode sheet 100 of the above-mentioned first embodiment, the resistance in the middle position of the current collector 10 is reduced, and the conductivity of the middle position of the current collector 10 can be improved, thereby improving the conductivity of the entire negative electrode sheet 100, thereby ensuring the fast charging performance of the battery cell, and at the same time, improving the energy density of the battery cell and the charge and discharge cycle performance of the battery cell.

[0047] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0048] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0049] In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. 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 utility model. In this specification, the schematic representations 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 one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0051] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A negative electrode sheet, characterized in that: include: current collector; A conductive coating is coated on at least one side of the current collector, and the resistance of the conductive coating decreases in a direction from both ends to the middle of the current collector.

2. The negative electrode sheet according to claim 1, characterized in that: The conductive coating includes a first region and two second regions, the first region is disposed between the two second regions, and the resistance of the first region is smaller than the resistance of the second region.

3. The negative electrode sheet according to claim 2, characterized in that: In the length direction of the current collector, a coating length of the first region is not less than a sum of coating lengths of two second regions.

4. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: The conductive coating comprises: a first coating and a second coating, wherein the first coating and the second coating are stacked in a thickness direction of the current collector, and the first coating is located between the second coating and the current collector.

5. The negative electrode sheet according to claim 4, characterized in that: In a thickness direction of the current collector, the resistance of the second coating layer is not less than the resistance of the first coating layer.

6. The negative electrode sheet according to claim 4, characterized in that: The first coating layer includes a first graphite material, the second coating layer includes a second graphite material, and the graphite particles in the first graphite material have a smaller size than the graphite particles in the second graphite material.

7. The negative electrode sheet according to claim 6, characterized in that: The specific surface area of ​​the second graphite material is not less than the specific surface area of ​​the first graphite material.

8. The negative electrode sheet according to claim 6, characterized in that: The particle size of the first graphite material satisfies the relationship: (D90-D10) / D50≤1.2, wherein D90 is the particle size smaller than which the volume content of particles accounts for 90% of all particles, D10 is the particle size smaller than which the volume content of particles accounts for 10% of all particles, and D50 is the median particle size.

9. The negative electrode sheet according to claim 4, characterized in that: The ratio of the surface density of the first coating layer to the second coating layer is 1:9-9:

1.

10. A battery cell, characterized in that: include: The negative electrode sheet according to any one of claims 1 to 9.

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