Electrode and battery

Abstract

The utility model discloses a pole piece and a battery, wherein the pole piece includes a substrate, a first graphite layer and a second graphite layer. The first graphite layer and the substrate are stacked along a first direction. The second graphite layer is stacked along the first direction with the first graphite layer and is located on a side of the first graphite layer away from the substrate. The thermal conductivity of the second graphite layer is greater than the thermal conductivity of the first graphite layer. The battery includes a pole piece. The application can effectively improve the accuracy of graphite etching depth control, improve battery capacity, and ensure the yield rate of the battery.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a pole piece and a battery. Background Art

[0002] In order to increase the battery capacity, the existing technology is to use advanced electrode materials and thick electrodes, which can effectively reduce the excess weight and volume associated with inactive components (current collectors, separators and packaging materials). However, the use of thick electrodes will deteriorate the charging capacity of the battery. Specifically, due to the dense accumulation of graphite particles, a tortuous diffusion path is created for lithium ion transmission. As the electrode thickness increases, lithium ion transmission is further restricted. Therefore, a significant concentration gradient increases through the electrode thickness, which will lead to large battery polarization and significantly reduce the accessible capacity of the electrode under fast charging conditions.

[0003] In the related art, in order to overcome the transmission limitation of thick electrodes, one way is to use an engineered three-dimensional electrode structure to change the diffusion path of ion transmission. Specifically, laser etching is used to punch holes in the single-layer graphite layer of the pole piece to change the transmission path of the ions, build an efficient ion transmission structure, and improve the charging capacity of the battery. However, due to the process capabilities of the laser etching equipment, different types of anode graphite, and uneven coating thickness, the etching depth varies greatly. Too deep etching depth will cause the pole piece to break and local lithium deposition in the later cycle; too shallow etching depth will not improve the battery performance ideally. Therefore, how to accurately control the graphite etching depth has become an urgent problem to be solved. Utility Model Content

[0004] The main purpose of the utility model is to provide a pole piece and a battery, aiming to solve the technical problem of inaccurate graphite etching depth control.

[0005] To achieve the above-mentioned purpose, the first embodiment of the utility model provides a pole piece, comprising:

[0006] matrix;

[0007] A first graphite layer is stacked with the substrate along a first direction;

[0008] a second graphite layer, stacked with the first graphite layer along the first direction and located on a side of the first graphite layer away from the substrate;

[0009] Wherein, the thermal conductivity of the second graphite layer is greater than the thermal conductivity of the first graphite layer.

[0010] In some embodiments, the thermal conductivity of the first graphite layer is λ1, and the thermal conductivity of the second graphite layer is λ2, wherein λ1:λ2 is 1 / 10 to 1 / 3.

[0011] In some embodiments, the thermal conductivity of the first graphite layer is 70 W / mK to 150 W / mK, and the thermal conductivity of the second graphite layer is 400 W / mK to 800 W / mK.

[0012] In some embodiments, the thickness of the first graphite layer along the first direction is H1, and the thickness of the second graphite layer along the first direction is H2, wherein H1:H2 is 1 / 2-1.

[0013] In some embodiments, a thickness H1 of the first graphite layer along the first direction is 20 μm to 30 μm, and a thickness H2 of the second graphite layer along the first direction is 30 μm to 50 μm.

[0014] In some embodiments, the second graphite layer includes a plurality of openings, each of the openings extends along the first direction, and adjacent openings are spaced apart along a second direction, and the second direction is perpendicular to the first direction.

[0015] In some embodiments, the aperture D of the opening along the second direction is 80 um to 120 um.

[0016] In some embodiments, the opening penetrates the second graphite layer along the first direction.

[0017] In some embodiments, the material of the first graphite layer is natural graphite, and the material of the second graphite layer is graphene.

[0018] A second aspect of the present invention provides a battery, comprising the pole piece as described in the above embodiment.

[0019] Compared with the prior art, the beneficial effects of the utility model are:

[0020] In the technical solution of the utility model, the pole piece includes a substrate, a first graphite layer and a second graphite layer. The first graphite layer and the substrate are stacked in a first direction, and the second graphite layer is stacked with the first graphite layer and is located on the side of the first graphite layer away from the base. In the prior art, a single-layer graphite layer is provided for the pole piece, and a single-layer graphite layer is etched by laser. The accuracy of the graphite etching depth cannot be achieved due to the process capability of the laser etching equipment. In this solution, the thermal conductivity of the second graphite layer is greater than that of the first graphite layer, that is, the second graphite layer is easier to etch than the first graphite layer. Therefore, the laser etching depth of the pole piece can be controlled by controlling the thickness of the second graphite layer to ensure the accuracy of the control of the graphite etching depth. Therefore, this solution can effectively avoid problems such as pole piece breakage and local lithium deposition in the later cycle caused by excessively deep graphite etching depth, and can also avoid the situation of poor battery performance caused by too shallow etching depth, effectively improve battery capacity, and ensure the yield rate of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0022] Figure 1 Schematic diagram of a pole piece in an embodiment of the utility model; wherein the pole piece is not laser etched, that is, the second graphite layer is not provided with an opening;

[0023] Figure 2 It is a schematic diagram of a pole piece in an embodiment of the utility model; wherein the pole piece has been laser etched, that is, the second graphite layer is provided with a plurality of openings.

[0024] Description of Figure Numbers:

[0025] Pole piece 10;

[0026] Base 100;

[0027] A first graphite layer 200;

[0028] Second graphite layer 300; opening 310;

[0029] First direction X; second direction Y.

[0030] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0032] In the related art, in order to overcome the transmission limitation of thick electrodes, one way is to use an engineered three-dimensional electrode structure to change the diffusion path of ion transmission. Specifically, laser etching is used to punch holes in the single-layer graphite layer of the pole piece to change the transmission path of the ions, build an efficient ion transmission structure, and improve the charging capacity of the battery. However, due to the process capabilities of the laser etching equipment, different types of anode graphite, and uneven coating thickness, the etching depth varies greatly. Too deep etching depth will cause the pole piece to break and local lithium deposition in the later cycle; too shallow etching depth will not improve the battery performance ideally. Therefore, how to accurately control the graphite etching depth has become an urgent problem to be solved.

[0033] In view of this, the first embodiment of the present invention proposes a pole piece 10, which can ensure the accuracy of laser etching depth and improve battery capacity. It should be noted that the pole piece 10 is used as an anode pole piece 10. Figure 1 and Figure 2 The pole piece 10 of the embodiment of the present application is introduced. Specifically, the pole piece 10 includes a substrate 100, a first graphite layer 200 and a second graphite layer 300.

[0034] The substrate 100 is used for coating the graphite layer. It should be noted that the substrate 100 may be a copper foil. The specific configuration of the substrate 100 may refer to the related known technology.

[0035] Reference Figure 1 The first graphite layer 200 is used to be coated on the substrate 100. To facilitate the description and understanding of the specific arrangement of the first graphite layer 200, a first direction X is defined. The first graphite layer 200 and the substrate 100 are stacked along the first direction X. It can be understood that the first direction X can be the thickness direction of the copper foil. Figure 1 The first direction X may be the up-down direction. It should be noted that the first graphite layer 200 may be coated on both sides of the substrate 100 along the first direction X, and the specific coating area and coating thickness of the first graphite layer 200 may be determined according to actual conditions.

[0036] Reference Figure 1 The second graphite layer 300 is used to be coated on the first graphite layer 200. Specifically, the second graphite layer 300 is stacked with the first graphite layer 200 along the first direction X and is located on the side of the first graphite layer 200 that is away from the substrate 100. Figure 1 The orientation in is used as a reference, that is, the first graphite layer 200 is located between the second graphite layer 300 and the substrate 100. It can be understood that the second graphite layer 300 can be coated on the first graphite layer 200 on both sides of the substrate 100 along the first direction X. The specific coating area and coating thickness of the second graphite layer 300 can be determined according to actual conditions.

[0037] It should be noted that the thermal conductivity of the second graphite layer 300 is greater than that of the first graphite layer 200. Therefore, when the pole piece 10 is etched by laser, the second graphite layer 300 is easier to etch by laser due to its high thermal conductivity, while the first graphite layer 200 is difficult to etch by laser due to its low thermal conductivity.

[0038] In the technical solution of the present utility model, the pole piece 10 includes a substrate 100, a first graphite layer 200 and a second graphite layer 300. The first graphite layer 200 and the substrate 100 are stacked along the first direction X, and the second graphite layer 300 is stacked with the first graphite layer 200 and is located on the side of the first graphite layer 200 away from the base. In the prior art, a single-layer graphite layer is provided in the pole piece, and the single-layer graphite layer is etched by laser. Due to the process capability of the laser etching equipment, the accuracy of the graphite etching depth cannot be achieved. In this solution, the thermal conductivity of the second graphite layer 300 is greater than the thermal conductivity of the first graphite layer 200, that is, the second graphite layer 300 is easier to etch than the first graphite layer 200. Therefore, the laser etching depth of the pole piece 10 can be controlled by controlling the thickness of the second graphite layer 300, thereby ensuring the accuracy of the control of the graphite etching depth. Therefore, this solution can effectively avoid problems such as the breakage of the electrode 10 and local lithium deposition in the later cycle caused by excessive etching depth of graphite, and can also avoid the situation where the battery performance is poor due to excessively shallow etching depth, effectively improve the battery capacity and ensure the battery yield.

[0039] The following introduces the thermal conductivity ratio between the first graphite layer 200 and the second graphite layer 300. In some embodiments, the thermal conductivity of the first graphite layer 200 is λ1, and the thermal conductivity of the second graphite layer 300 is λ2. Among them, λ1:λ2 is 1 / 10 to 1 / 3. Exemplarily, λ1:λ2 can be 1 / 10, 1 / 7, 1 / 4 or 1 / 3, etc. In this scheme, λ1 and λ2 are in a specific ratio, that is, the etching difficulty of the first graphite layer 200 is several times that of the second graphite layer 300, so that even if the laser beam penetrates the first graphite layer 200, it is difficult to etch the second graphite layer 300. Therefore, the etching depth can be controlled by controlling the thickness of the second graphite layer 300, so as to achieve precise control of the etching depth, improve battery performance, and ensure the yield rate of the battery.

[0040] The specific selection of thermal conductivity of the first graphite layer 200 and the second graphite layer 300 is described below. In some embodiments, the thermal conductivity of the first graphite layer 200 is 70W / mK to 150W / mK. For example, the thermal conductivity of the first graphite layer 200 can be 70W / mK, 82W / mK, 91W / mK, 112W / mK, 134W / mK, 140W / mK or 150W / mK, etc.

[0041] The thermal conductivity of the second graphite layer 300 is 400 W / mK to 800 W / mK. For example, the thermal conductivity of the second graphite layer 300 may be 400 W / mK, 460 W / mK, 570 W / mK, 600 W / mK, 730 W / mK, or 800 W / mK.

[0042] This solution can effectively reduce the situation where the laser etches the first graphite layer 200 after penetrating and etching the second graphite layer 300 by coating the first graphite layer 200 and the second graphite layer 300 with thermal conductivity within the above range, thereby avoiding the low capacitance phenomenon.

[0043] Reference Figure 1 , the following introduces the thickness ratio relationship between the first graphite layer 200 and the second graphite layer 300. In some embodiments, the thickness of the first graphite layer 200 along the first direction X is H1. The thickness of the second graphite layer 300 along the first direction X is H2. Among them, H1:H2 is 1 / 2 to 1. Exemplarily, H1:H2 can be 1 / 2, 2 / 3, 3 / 4 or 1, etc. Preferably, H1:H2 is 1 / 2 to 2 / 3. Exemplarily, H1:H2 can be 1 / 2, 3 / 5 or 2 / 3, etc. This solution can not only improve the charging capacity of the battery, but also enable the battery to have a higher capacity by making the thickness of the first graphite layer 200 and the thickness of the second graphite layer 300 present a specific proportional relationship.

[0044] The specific thickness setting of the first graphite layer 200 is introduced below. In some embodiments, the thickness H1 of the first graphite layer 200 along the first direction X is 20μm to 30μm. Exemplarily, H1 can be 20μm, 22μm, 24μm, 27μm or 30μm, etc. When the thickness of the first graphite layer 200 is too thin, the battery capacity will be low, and when the thickness of the first graphite layer 200 is too thick, the charging capacity of the battery will be reduced. This solution sets the first graphite layer 200 to a specified thickness, which can not only increase the battery capacity, but also ensure the charging capacity of the battery.

[0045] The specific thickness setting of the second graphite layer 300 is introduced below. In some embodiments, the thickness H2 of the second graphite layer 300 along the first direction X is 30μm to 50μm. Exemplarily, H2 can be 30μm, 35μm, 41μm, 47μm or 50μm, etc. When the thickness of the second graphite layer 300 is too thin, the effective ion channel constructed after etching is insufficient, and the improvement of the battery charging capacity is weak; when the thickness of the second graphite layer 300 is too thick, too much graphite will be etched, and low capacity phenomenon is prone to occur. By setting the second graphite layer 300 to the above-mentioned thickness range, this solution can not only effectively improve the battery charging capacity, but also avoid the occurrence of low battery capacity phenomenon.

[0046] Reference Figure 2In some embodiments, after the second graphite layer 300 is etched by laser, a plurality of openings 310 are formed in the second graphite layer 300. The specific arrangement of the plurality of openings 310 is described below. Each opening 310 extends along the first direction X to Figure 2 The orientation in is used as a reference, that is, each opening 310 is arranged to extend in the up-down direction.

[0047] The specific arrangement of the plurality of openings 310 on the second graphite layer 300 is described below. Specifically, adjacent openings 310 are arranged at intervals along the second direction Y, and the second direction Y is perpendicular to the first direction X. It should be noted that the second direction Y can be any direction perpendicular to the first direction X. It can be understood that the interval between two adjacent openings 310 can be uniform or non-uniform. Some embodiments of the present application are described by taking the uniform interval between two adjacent openings 310 as an example.

[0048] by Figure 2 In some embodiments, the plurality of openings 310 may be arranged at intervals along the left-right direction. In other embodiments, the plurality of openings 310 may be arranged at intervals along the front-back direction. In other embodiments, the plurality of openings 310 may also be arranged at intervals along any inclined direction perpendicular to the up-down direction. The specific arrangement of the plurality of openings 310 may be determined according to actual conditions. Some embodiments of the present application are described by taking the plurality of openings 310 being arranged at intervals along the left-right direction and the front-back direction at the same time as an example.

[0049] The size setting of the opening 310 is described below. It should be noted that, when viewed along the first direction X, the outer contour of the opening 310 may be a circle. When the opening 310 is cut along the first direction X and viewed along the second direction Y, the outer contour of the opening 310 may be an inverted trapezoid, a triangle, or a dot array, etc. In some embodiments of the present application, the outer contour of the opening 310 is described as an inverted trapezoid (viewed along the second direction Y).

[0050] In some embodiments, the aperture D of the opening 310 along the second direction Y is 80 um to 120 um. For example, the aperture D of the opening 310 may be 80 um, 85 um, 93 um, 105 um, 117 um, or 120 um. Figure 2 The aperture of the opening 310 refers to the aperture of the second graphite layer 300 at the end away from the first graphite layer 200. In this solution, by setting the aperture of the opening 310 to the above size range, the opening 310 can better lock the electrolyte of the battery, thereby ensuring the performance of the battery and reducing the loss of graphite.

[0051] The following describes the depth of the opening 310. In some embodiments, the opening 310 may penetrate the second graphite layer 300 along the first direction X, that is, the depth of the opening 310 is equal to the thickness of the second graphite layer 300. Therefore, the present solution can control the laser etching depth by controlling the thickness of the second graphite layer 300, thereby ensuring the accuracy of the control of the graphite etching depth.

[0052] In some embodiments, the material of the first graphite layer 200 is natural graphite, and the material of the second graphite layer 300 is graphene.

[0053] The second embodiment of the utility model provides a battery, which includes the pole piece 10 in the above embodiment. This solution can ensure the accuracy of graphite etching depth control, effectively avoid the problems of pole piece 10 breaking and local lithium deposition in the later cycle caused by too deep graphite etching depth, and can also avoid the situation of poor battery performance caused by too shallow etching depth, effectively improve battery capacity, and ensure the yield rate of the battery.

[0054] The following describes the test process of etching the pole piece 10 of some embodiments and verifying its performance.

[0055] The specific steps for making soft-pack square batteries and testing their performance are as follows:

[0056] Cathode pole piece 10: The cathode active material is evenly coated on the aluminum current collector, and then rolled and cut into strips to obtain the cathode pole piece 10.

[0057] Anode electrode 10: A double layer of graphite is coated on a copper foil, and then the second graphite layer 300 is etched through.

[0058] Isolation film: The PE surface is coated with a ceramic mixture as an isolation film.

[0059] Electrolyte: Ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PP) are mixed in a volume ratio of 1:1:4:4, and then fully dried lithium salt LiPF6 is dissolved in a mixed organic solvent at a ratio of 1 mol / L to prepare an electrolyte.

[0060] Preparation of a full battery: The cathode electrode sheet 10, the anode electrode sheet 10, and the separator are wound or stacked to form a bare battery cell, and then liquid is injected and packaged to obtain a finished lithium-ion battery.

[0061] Table 1 shows the setting parameters of the pole piece 10 of some embodiments and comparative examples of the present application.

[0062]

[0063]

[0064] Table 1

[0065] The performance indicators of the battery are introduced below. The cycle attenuation rate is the percentage of the initial capacity when the battery cell is charged to 4.53V at 3.2C step rate, charged to the cut-off voltage at 1.5C rate, and cycled 800 times. The rate performance is the ratio of the 2C rate discharge capacity to the 0.2C rate discharge at room temperature. The charging window is the maximum rate corresponding to the cell not depositing lithium after the cell interface is disassembled at 4.8C, 4.6C, 4.4C, 4.2C, 4.0C, 3.8C, 3.6C, 3.4C, 3.2C, 3.0C, 2.8C, 2.6C, 2.4C, 2.0C, 1.8C, 1.6C, 1.4C, and 1.2C conditions and the cell is directly charged to the cut-off voltage.

[0066] The batteries of some embodiments and comparative examples of the present application were tested, and the results shown in Table 2 were obtained.

[0067] Serial number Capacity decay rate Rate performance Lithium Separation Window Example 1 93％ 97.2％ 4.2C Example 2 89％ 98.5％ 4.6C Example 3 92％ 98.2 4.4C Example 4 87％ 94.3％ 4.2C Example 5 85％ 95.3％ 4.2C Example 6 94％ 98.8％ 4.4C Comparative Example 1 79％ 93.2％ 3.6C Comparative Example 2 82％ 95.7％ 4.6C Comparative Example 3 81％ 92.6％ 3.2C Comparative Example 4 81％ 91.2％ 4.4C

[0068] Table 2

[0069] Referring to Examples 1-3 and Comparative Examples 1-2 in Tables 1 and 2, it can be seen that the thickness and ratio of the second graphite layer 300 to the first graphite layer 200 will affect the lithium deposition window and rate performance. When the thickness of the second graphite layer 300 is large, the lithium deposition window and rate performance are good, but the capacity attenuation rate is poor.

[0070] Referring to Examples 4-6 and Comparative Examples 3-4 in Tables 1 and 2, it can be seen that the thermal conductivity of the second graphite layer 300 and the first graphite layer 200 and their ratio will affect the lithium precipitation window and rate performance. The second graphite layer 300 has a large thermal conductivity. When etching the same depth, the etched volume is relatively larger, the constructed ion channel is also larger, the lithium precipitation window is improved, but the capacity attenuation rate is reduced. In addition, the upper layer has a large thermal conductivity, and energy is more easily transferred to the first graphite layer 200. When the second graphite layer 300 is through-etched, it is easy to damage the first graphite layer 200, reducing the capacity of the battery.

[0071] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0072] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or", "and / or" or "and / or" appears in the full text, its meaning includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the utility model.

[0073] The above are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the utility model concept, or directly / indirectly used in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A pole piece, characterized in that: include: matrix; A first graphite layer is stacked with the substrate along a first direction; a second graphite layer, stacked with the first graphite layer along the first direction and located on a side of the first graphite layer away from the substrate; Wherein, the thermal conductivity of the second graphite layer is greater than the thermal conductivity of the first graphite layer.

2. The pole piece according to claim 1, characterized in that: The thermal conductivity of the first graphite layer is λ1, and the thermal conductivity of the second graphite layer is λ2, wherein λ1:λ2 is 1 / 10 to 1 / 3.

3. The pole piece according to claim 2, characterized in that: The thermal conductivity of the first graphite layer is 70 W / mK to 150 W / mK, and the thermal conductivity of the second graphite layer is 400 W / mK to 800 W / mK.

4. The pole piece according to claim 1, characterized in that: The thickness of the first graphite layer along the first direction is H1, and the thickness of the second graphite layer along the first direction is H2, wherein H1:H2 is 1 / 2-1.

5. The pole piece according to claim 4, characterized in that: A thickness H1 of the first graphite layer along the first direction is 20 μm to 30 μm, and a thickness H2 of the second graphite layer along the first direction is 30 μm to 50 μm.

6. The pole piece according to claim 1, characterized in that: The second graphite layer includes a plurality of openings, each of the openings extends along the first direction, and adjacent openings are arranged at intervals along a second direction, and the second direction is perpendicular to the first direction.

7. The pole piece according to claim 6, characterized in that: The aperture D of the opening along the second direction is 80 um to 120 um.

8. The pole piece according to claim 6, characterized in that: The opening penetrates the second graphite layer along the first direction.

9. The pole piece according to claim 1, characterized in that: The material of the first graphite layer is natural graphite, and the material of the second graphite layer is graphene.

10. A battery, characterized in that: Comprising a pole piece as described in any one of claims 1 to 9.

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