Electrode sheet, battery, and manufacturing method for electrode sheet

Abstract

The present invention relates to the technical field of battery production and manufacturing. Disclosed are an electrode sheet, a battery, and a manufacturing method for the electrode sheet. The electrode sheet comprises a current collector, a first graphite layer, and a second graphite layer; the current collector comprises a first wall surface; the first graphite layer is arranged on the first wall surface, and grooves are formed in the side of the first graphite layer facing away from the current collector; the second graphite layer is arranged on the side of the first graphite layer facing away from the current collector, and the second graphite layer fills the grooves, wherein the ion diffusion rate of the material of the second graphite layer is higher than that of the material of the first graphite layer. The battery comprises the electrode sheet. The manufacturing method for the electrode sheet is used for manufacturing the electrode sheet. According to the electrode sheet, the battery, and the manufacturing method for the electrode sheet, the fast-charging capability can be improved while achieving high capacity.

Description

Pole piece, battery and method for preparing pole piece Technical Field

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

[0002] As a new type of secondary battery, lithium-ion batteries offer advantages such as high energy and power density, high operating voltage, light weight, compact size, long cycle life, excellent safety, and environmental friendliness. They hold broad application prospects in portable appliances, power tools, large-scale energy storage, and electric transportation power sources. With the rapid development of lithium-ion battery technology, market demands for increasingly higher performance are demanding not only high energy density but also fast charging speeds.

[0003] In order to meet the characteristics of lithium-ion batteries that require both high energy density and fast charging, in addition to improving materials to achieve fast charging, improvements can also be made in the process, such as the double-layer coating process. However, in the double-layer coating process, the upper and lower materials are divided into two layers, the upper layer is the fast-charging material, and the lower layer is the high-capacity material. Among them, lithium ions migrate very quickly in the upper layer of fast-charging material, but when they reach the lower layer of high-capacity material, the lithium insertion speed will slow down, which limits the rapid diffusion of lithium ions to the bottom layer, that is, reduces the charging speed of the battery.

[0004] Summary of the Invention

[0005] The main purpose of this application is to propose a pole piece, a battery and a method for preparing the pole piece, aiming to solve the problem in the prior art that the battery cannot be fast charged due to the inability of lithium ions to diffuse rapidly, so as to increase the charging speed of the battery.

[0006] In order to achieve the above objectives, the present application provides a pole piece, comprising:

[0007] a current collector comprising a first wall;

[0008] A first graphite layer is provided on the first wall surface, wherein a groove is provided on a side of the first graphite layer facing away from the current collector;

[0009] a second graphite layer, disposed on a side of the first graphite layer facing away from the current collector, and the second graphite layer fills the groove;

[0010] The ion diffusion rate of the material of the second graphite layer is higher than the ion diffusion rate of the material of the first graphite layer.

[0011] In some embodiments, the capacitance of the material of the first graphite layer is higher than the capacitance of the material of the second graphite layer.

[0012] In some embodiments, the groove penetrates the first graphite layer along a direction from the first graphite layer to the current collector.

[0013] In some embodiments, an included angle α between the groove wall of the groove and the first wall surface satisfies: 30°≤α≤90°.

[0014] In some embodiments, the groove runs through both ends of the first graphite layer in a straight line perpendicular to a direction pointing from the first graphite layer to the current collector.

[0015] In some embodiments, the first graphite layer is provided with a plurality of the grooves, and the grooves are spaced apart from each other.

[0016] In some embodiments, the width dimension range D1 of each groove satisfies: 0.5um≤D1≤2000um, the height dimension range D2 of each groove satisfies: 3.5um≤D2≤60um, and the spacing dimension range D3 between two adjacent grooves satisfies: 0.5mm≤D3≤8mm.

[0017] In some embodiments, the thickness range L1 of the first graphite layer satisfies: 3.5 um≤L1≤60 um, and the thickness range L2 of the second graphite layer satisfies: 2 um≤L2≤60 um.

[0018] The second aspect of the present application further provides a battery, comprising: a pole piece as described in any one of the above items.

[0019] A third aspect of the present application further provides a method for preparing a pole piece, which is used to manufacture the pole piece described in any one of the above items, comprising:

[0020] Applying a first graphite layer to a current collector, and providing a plurality of grooves spaced apart on the first graphite layer so that the current collector is partially exposed;

[0021] A second graphite layer is coated on a side of the first graphite layer facing away from the current collector, and the second graphite layer completely covers the first graphite layer.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] In the technical solution of the present application, a double-layer coating process is adopted, in which a first graphite layer is provided on one wall surface of the current collector, and a second graphite layer is provided on the side of the first graphite layer facing away from the current collector. The first graphite layer serves as the bottom layer and the second graphite layer serves as the top layer, wherein the diffusion rate of lithium ions in the second graphite layer is greater than the diffusion rate in the first graphite layer. In order to increase the diffusion rate of lithium ions to the bottom layer and thereby increase the charging rate of the battery, a groove is formed in the first graphite layer and filled with a second graphite layer. The upper layer material is interspersed with the bottom layer material to construct a channel for the rapid embedding of lithium ions into the bottom layer, thereby increasing the diffusion rate of lithium ions to the bottom layer and ultimately achieving rapid charging of the battery.

[0024] Batteries utilizing the aforementioned electrode sheets and methods for preparing them can effectively enhance the battery's fast-charging capabilities. Furthermore, by constructing lithium-ion channels by interweaving the upper layer material through the lower layer material, lithium-ion accumulation can be avoided, thereby ensuring the battery's safety during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0026] FIG1 is a front view of the structure of a pole piece in one embodiment of the present application;

[0027] FIG2 is a front view of a pole piece in another embodiment of the present application;

[0028] FIG3 is a top cross-sectional view of the structure of a pole piece in one embodiment of the present application;

[0029] FIG4 is a top cross-sectional view of the structure of a pole piece in another embodiment of the present application;

[0030] FIG5 is a top cross-sectional view of the structure of a pole piece in yet another embodiment of the present application;

[0031] FIG6 is a top cross-sectional view of the structure of a pole piece in yet another embodiment of the present application;

[0032] FIG7 is a schematic flow chart of a method for preparing a pole piece in one embodiment of the present application.

[0033] Description of the accompanying drawings: 100 - current collector; 110 - first wall; 200 - first graphite layer; 210 - groove; 300 - second graphite layer.

[0034] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0036] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0037] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if "and / or", "and / or" or "and / or" appear 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 in which A and B are satisfied at the same time. 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 mutually 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 this application.

[0038] With the development of terminals, mobile devices have increasingly higher requirements for fast charging of batteries. In order to meet the characteristics of lithium-ion batteries that require both high energy density and fast charging, in addition to improving materials to achieve fast charging, improvements can also be made in the process, such as the double-layer coating process. However, in the double-layer coating process, the upper and lower materials are divided into two layers, the upper layer is the fast-charging material, and the lower layer is the high-capacity material. Among them, lithium ions migrate very quickly in the upper fast-charging material, but when they reach the lower high-capacity material, the lithium insertion speed will slow down, which limits the rapid diffusion of lithium ions to the bottom layer, that is, reduces the charging speed of the battery.

[0039] In view of this, referring to Figures 1 to 6, an embodiment of the present application provides a pole piece that uses a double-layer coating method to combine fast-charging materials with high-capacity materials. While retaining high capacity, it can effectively increase charging speed, facilitate fast charging of mobile devices, and bring great convenience to users. This pole piece can be used in batteries with different structures, such as central tab placement, stacked tabs, and multiple tabs, and has a wide range of applicability.

[0040] Specifically, the electrode provided in this embodiment includes a current collector 100, a first graphite layer 200, and a second graphite layer 300. The current collector 100 includes a first wall 110, the first graphite layer 200 is disposed on the first wall 110, and a groove 210 is formed on the side of the first graphite layer 200 facing away from the current collector 100. The second graphite layer 300 is disposed on the side of the first graphite layer 200 facing away from the current collector 100, and the second graphite layer 300 fills the groove 210. Furthermore, along the direction from the first graphite layer 200 to the current collector 100, the second graphite layer 300 can partially fill the groove 210, that is, the second graphite layer 300 still leaves space in the groove, or the second graphite layer 300 can completely fill the groove 210, that is, the second graphite layer 300 is in close contact with the sidewalls and bottom of the groove 210. The ion diffusion rate of the material of the second graphite layer 300 is higher than that of the material of the first graphite layer 200 , that is, the migration speed of lithium ions in the second graphite layer 300 is faster than that in the first graphite layer 200 .

[0041] The electrode provided in this embodiment adopts a double-layer coating process, in which a first graphite layer 200 is provided on one wall surface of the current collector 100, and a second graphite layer 300 is provided on the side of the first graphite layer 200 facing away from the current collector 100. The first graphite layer 200 serves as the bottom layer and the second graphite layer 300 serves as the top layer, wherein the diffusion rate of lithium ions in the second graphite layer 300 is greater than the diffusion rate in the first graphite layer 200. In order to increase the diffusion rate of lithium ions to the bottom layer and thus increase the charging rate of the battery, a groove 210 is opened in the first graphite layer 200, and the groove 210 is filled with the second graphite layer 300. By interpenetrating the upper layer material into the bottom layer material, a channel for lithium ions to quickly embed into the bottom layer is constructed, thereby increasing the diffusion rate of lithium ions to the bottom layer and ultimately achieving rapid charging of the battery.

[0042] In addition, if the diffusion rate of lithium ions is slow, as the charging time increases, lithium ions will accumulate on the surface of the active material in large quantities. The accumulation of excessive lithium ions will cause other safety problems during the charging process and affect the normal charging and discharging of the battery.

[0043] In the above embodiments, current collector 100 refers to a structure or component that collects current. In lithium-ion batteries, it primarily refers to metal foil, such as copper foil or aluminum foil. The term also generally includes tabs. These are common structures or components in the art and will not be described in detail here.

[0044] In the above embodiment, referring to Figures 3 to 6, along the direction perpendicular to the direction from the first graphite layer 200 to the current collector 100, the cross-sectional shape of the groove 210 can be a linear groove, or grooves of other different shapes can be used, such as circular grooves, rectangular grooves or other polygonal grooves. Further, along the direction perpendicular to the direction from the first graphite layer 200 to the current collector 100, the groove 210 can be a continuous line, a line segment, an inclined shape or a grid shape. The shapes or arrangements of the grooves 210 will no longer be enumerated one by one here, as long as the second graphite layer 300 fills the grooves 210 and the lithium ions diffuse quickly to the bottom layer.

[0045] In some embodiments, the capacitance of the material of the first graphite layer 200 is higher than the capacitance of the material of the second graphite layer 300 .

[0046] Specifically, the material of the first graphite layer 200 has a higher capacitance than the material of the second graphite layer 300, that is, the first graphite layer 200 can store more lithium ions per unit mass. Under the premise of being able to store the same amount of lithium ions, more lithium ions can be stored per unit mass, and the volume can be designed to be smaller accordingly. That is, under the premise of meeting the requirements of high battery capacity and fast charging, the battery can be designed to be lighter, thinner and more portable, thereby improving the user experience.

[0047] In some embodiments, referring to FIG. 1 , the groove 210 penetrates the first graphite layer 200 along a direction from the first graphite layer 200 to the current collector 100 .

[0048] Specifically, the groove 210 passes through the first graphite layer 200. When the second graphite layer 300 is used to fill the groove 210, the second graphite layer 300 can be directly embedded in the bottom layer to construct a lithium ion channel that goes directly through the bottom layer. In this way, when charging, lithium ions can quickly diffuse to the bottom layer along the lithium ion channel, thereby improving the fast charging capability of the battery and realizing fast charging of the battery.

[0049] In some embodiments, referring to FIG. 1 , the angle α between the groove wall of the groove 210 and the first wall surface 110 satisfies: 30°≤α≤90°, where the value of α can be 30°, 60°, or 90°.

[0050] Specifically, the groove 210 can be a V-shaped structure or a U-shaped structure, and the angle between the groove wall of the groove 210 and the first wall surface 110 is not limited here. Preferably, since the size of the groove 210 is at the micron level, while ensuring the processing accuracy, it has a high processing difficulty. Therefore, in this embodiment, referring to Figure 1, the groove 210 is vertically arranged so that the groove wall of the groove 210 is perpendicular to the first wall surface 110, that is, the angle α between the groove wall of the groove 210 and the first wall surface 110 is 90°, which facilitates the processing and forming of the groove 210 and reduces the difficulty of processing the groove 210. For example, when the groove 210 is processed by laser drilling or physical punching, it only needs to be processed along the same direction, and the groove 210 can be formed, which greatly improves the processing efficiency, saves processing time, and reduces processing costs.

[0051] In some embodiments, referring to FIG. 3 , the groove 210 passes through both ends of the first graphite layer 200 in a straight line perpendicular to a direction from the first graphite layer 200 to the current collector 100 .

[0052] Specifically, based on the same reasons as in the above-mentioned embodiment, since the size of the groove 210 is at the micron level, it has a high processing difficulty while ensuring processing accuracy. Therefore, in this embodiment, referring to Figure 3, the groove 210 is passed through both ends of the first graphite layer 200 in a straight line, which facilitates the processing and forming of the groove 210 and reduces the difficulty of processing the groove 210.

[0053] In addition, the groove 210 is straightly passed through both ends of the first graphite layer 200, providing more filling channels for the second graphite layer 300. In unit time, more lithium ions can quickly diffuse along the channels to the bottom layer, effectively improving the charging capacity of the battery and achieving fast charging of the battery.

[0054] In some embodiments, referring to FIG. 3 to FIG. 6 , the first graphite layer 200 is provided with a plurality of grooves 210 , and the grooves 210 are spaced apart from each other.

[0055] Specifically, by providing multiple mutually spaced grooves 210 in the first graphite layer 200, multiple independent filling channels are provided for the second graphite layer 300, thereby constructing multiple fast ion channels. When charging the battery, lithium ions can quickly diffuse to the bottom layer along these multiple independent ion channels, thereby effectively improving the battery's fast charging capability.

[0056] Furthermore, the construction of multiple independent ion channels effectively avoids the accumulation of lithium ions in the same ion channel, allowing lithium ions to be dispersed to different ion channels and diffuse rapidly to the bottom layer along different ion channels at the same time. In this way, while achieving fast charging of the battery, it can also prevent abnormal charging and discharging due to the accumulation of lithium ions, eliminate safety hazards during the battery charging process, and thus improve the safety performance of the battery.

[0057] In some embodiments, the width D1 of each groove 210 satisfies the following range: 0.5 μm ≤ D1 ≤ 2000 μm. For example, D1 can be 0.5 μm, 10 μm, 100 μm, 1000 μm, 2000 μm, etc. The height D2 of each groove 210 satisfies the following range: 3.5 μm ≤ D2 ≤ 60 μm. For example, D2 can be 3.5 μm, 20 μm, 40 μm, 60 μm, etc. The spacing D3 between two adjacent grooves 210 satisfies the following range: 0.5 mm ≤ D3 ≤ 8 mm. For example, D3 can be 0.5 mm, 3 mm, 6 mm, 8 mm, etc.

[0058] Specifically, as described above, along the direction perpendicular to the first graphite layer 200 pointing vertically to the current collector 100, the cross-sectional shape of the groove 210 can be a linear groove, wherein the multiple grooves 210 on the first graphite layer 200 can be continuous straight-line grooves as a whole, or discontinuous line segment grooves.

[0059] When the plurality of grooves 210 are continuous linear grooves, referring to FIG3 , the width dimension range D1 of each groove 210 satisfies the following conditions: 0.5 μm ≤ D1 ≤ 2000 μm. For example, D1 can be 0.5 μm, 10 μm, 100 μm, 1000 μm, 2000 μm, etc. The height dimension range D2 of each groove 210 satisfies the following conditions: 3.5 μm ≤ D2 ≤ 60 μm. For example, D2 can be 3.5 μm, 20 μm, 40 μm, 60 μm, etc. The spacing dimension range D3 between two adjacent grooves 210 satisfies the following conditions: 0.5 mm ≤ D3 ≤ 8 mm. For example, D3 can be 0.5 mm, 3 mm, 6 mm, 8 mm, etc.

[0060] When the plurality of grooves 210 are discontinuous line-segment grooves, referring to FIG4 , the width dimension range D1 of each groove 210 satisfies the following conditions: 0.5um≤D1≤2000um. For example, D1 can be 0.5um, 10um, 100um, 1000um, 2000um, and so on. The height dimension range D2 of each groove 210 satisfies the following conditions: 3.5um≤D2≤60um. For example, D2 can be 3.5um, 20um, 40um, 60um, and so on. The spacing dimension range D3 between two adjacent grooves 210 satisfies the following conditions: 0.5mm≤D3≤8mm. For example, D3 can be 0.5mm, 3mm, 6mm, 8mm, and so on. The line segment length dimension range D4 of each groove 210 satisfies the following conditions: 1mm≤D4≤10mm. For example, D4 ​​can be 1mm, 4mm, 8mm, 10mm, and so on.

[0061] In addition, along the direction perpendicular to the direction perpendicular to the first graphite layer 200 pointing to the current collector 100, the cross-sectional shape of the groove 210 can also be a groove of different shapes such as a circular groove, a rectangular groove or other polygonal groove. When the cross-sectional shape of the groove 210 is a groove of different shapes, referring to Figures 5 to 6, the height dimension range D2 of each groove 210 satisfies: 3.5um≤D2≤60um. For example, D2 can take values ​​of 3.5um, 20um, 40um, 60um, etc. The spacing dimension range D3 between two adjacent grooves 210 satisfies: 0.5mm≤D3≤8mm. For example, D3 can take values ​​of 0.5mm, 3mm, 6mm, 8mm, etc. The groove area dimension range D5 of each groove 210 satisfies: 0.25mm 2 ≤D5≤25mm 2 For example, D5 can be set to 0.25mm 2 , 10mm 2 , 20mm 2 , 25mm 2 etc.

[0062] In some embodiments, the thickness range L1 of the first graphite layer 200 satisfies the following: 3.5 μm ≤ L1 ≤ 60 μm. For example, L1 can be 3.5 μm, 20 μm, 40 μm, 60 μm, etc. The thickness range L2 of the second graphite layer 300 satisfies the following: 2 μm ≤ L2 ≤ 60 μm. For example, L2 can be 2 μm, 20 μm, 40 μm, 60 μm, etc.

[0063] Specifically, referring to Figure 1, the first graphite layer 200 and the second graphite layer 300 are projected along a direction perpendicular to the direction from the first graphite layer 200 to the current collector 100. The area enclosed by the outer contour of the projected area of ​​the second graphite layer 300 is larger than the area enclosed by the outer contour of the projected area of ​​the first graphite layer 200, that is, the second graphite layer 300 completely covers the first graphite layer 200. With such a structure, the area of ​​the groove 210 can be fully and effectively utilized, so that lithium ions can quickly diffuse to the bottom layer through the ion channel formed by the groove 210, thereby improving the fast charging performance of the battery.

[0064] Correspondingly, an embodiment of the present application further provides a battery, which includes the electrode in any of the above embodiments.

[0065] In this embodiment, specifically, the battery can have a centrally placed tab, a stacked tab, or multiple tabs, etc. Thanks to the above improvements, the battery of this embodiment has the same technical effects as above, which will not be repeated here.

[0066] It should be noted that other contents of the battery disclosed in this application can be found in the prior art and will not be described in detail here.

[0067] Correspondingly, an embodiment of the present application further provides a method for manufacturing a pole piece in any of the above embodiments, referring to FIG7 , comprising:

[0068] Step S101: applying a first graphite layer 200 to the current collector 100, and providing a plurality of grooves 210 at intervals on the first graphite layer 200 so that the current collector 100 is partially exposed;

[0069] Step S102: applying the second graphite layer 300 to the side of the first graphite layer 200 facing away from the current collector 100 , and the second graphite layer 300 completely covers the first graphite layer 200 ;

[0070] Among them, the capacitance of the material of the first graphite layer 200 is higher than the capacitance of the material of the second graphite layer 300, and the ion diffusion rate of the material of the second graphite layer 300 is higher than the ion diffusion rate of the material of the first graphite layer 200, that is, the first graphite layer 200 is a high-capacity graphite layer, and the second graphite layer 300 is a fast-charging graphite layer.

[0071] In some embodiments, specifically, the first graphite layer 200 is applied to the current collector 100 by extrusion coating. After the first graphite layer 200 is applied, a groove 210 is provided on the side of the first graphite layer 200 facing away from the current collector 100 to expose the current collector 100. The size and structure of the groove 210 herein all adopt the size and structure of the groove 210 described in the above embodiment, so they will not be described in detail here. Then, the pole piece coated with the first graphite layer 200 is rolled to achieve the designed compaction. Then, the rolled pole piece is coated for the second time, that is, the second graphite layer 300 is coated on the side of the first graphite layer 200 facing away from the current collector 100, and the second graphite layer 300 fills the above groove 210. After the second graphite layer 300 is applied, the pole piece is rolled again to achieve the designed compaction. Finally, the remaining battery manufacturing processes are completed for the pole piece after the second rolling. The result is a battery with both high capacity and fast charging performance. After secondary rolling, the double-layer graphite layers are tightly compacted, reducing the risk of material falling off and helping to increase the energy density of the battery.

[0072] In some embodiments, specifically, the first graphite layer 200 is applied to the current collector 100 by transfer coating. After the first graphite layer 200 is applied, a groove 210 is provided on the side of the first graphite layer 200 facing away from the current collector 100 to expose the current collector 100. The size and structure of the groove 210 herein all adopt the size and structure of the groove 210 described in the above embodiment, so they will not be described in detail here. Then, the pole piece coated with the first graphite layer 200 is rolled to achieve the designed compaction. Then, the rolled pole piece is coated for the second time, that is, the second graphite layer 300 is coated on the side of the first graphite layer 200 facing away from the current collector 100, and the second graphite layer 300 fills the above groove 210. After the second graphite layer 300 is applied, the pole piece is rolled again to achieve the designed compaction. Finally, the remaining battery manufacturing processes are completed for the pole piece after the second rolling. The result is a battery with both high capacity and fast charging performance. After secondary rolling, the double-layer graphite layers are tightly compacted, reducing the risk of material falling off and helping to increase the energy density of the battery.

[0073] In some embodiments, specifically, the first graphite layer 200 is applied to the current collector 100 by extrusion coating, and the electrode sheet coated with the first graphite layer 200 is rolled to achieve the designed compaction. Then, a groove 210 is opened on the first graphite layer 200 after rolling. Here, the groove 210 can be opened by laser drilling or physical punching. The size and structure of the groove 210 are all based on the size and structure of the groove 210 described in the above embodiment, so they are not described here. Then, a second graphite layer 300 is applied to one side of the groove 210 opened in the first graphite layer 200, and the second graphite layer 300 fills the above groove 210. After the second graphite layer 300 is applied, the electrode sheet is rolled again to achieve the designed compaction. Finally, the remaining battery manufacturing processes are completed on the electrode sheet after the second rolling. In this way, a battery with both high capacity and fast charging performance is obtained. Moreover, after the second rolling, the double-layer graphite layers are tightly compacted, which reduces the risk of material shedding and helps to improve the energy density of the battery.

[0074] It should be noted that in the above embodiment, there is no specific order for the steps of rolling the graphite layer and forming the grooves 210 in the first graphite layer 200. That is, the grooves 210 can be formed first and then rolled, or rolled first and then formed. The specific processing order can be arbitrarily changed according to the processing situation. Furthermore, the process method for forming the grooves 210 is not limited to a single method herein.

[0075] The electrode processing technology in the above embodiment is simple, which can solve the problem of fast charging and capacity compatibility of batteries, while improving the charging speed of the battery and retaining the high capacity of the battery. The battery using the above electrode and the preparation method of the above electrode can effectively improve the fast charging capability of the battery. And by inserting the upper material into the bottom material to construct a lithium ion channel, the accumulation of lithium ions can be avoided, thereby ensuring the safety performance of the battery during use.

[0076] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. All equivalent structural transformations made using the contents of the present application description and drawings under the inventive concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A pole piece, comprising: a current collector including a first wall; A first graphite layer, disposed on the first wall surface, wherein a groove is provided on a side of the first graphite layer away from the current collector; A second graphite layer is disposed on a side of the first graphite layer away from the current collector, and the second graphite layer fills the groove; The ion diffusion rate of the material of the second graphite layer is higher than the ion diffusion rate of the material of the first graphite layer.

2. The pole piece according to claim 1, wherein: The capacitance of the material of the first graphite layer is higher than the capacitance of the material of the second graphite layer.

3. The pole piece according to claim 1, wherein: The groove penetrates the first graphite layer along a direction from the first graphite layer to the current collector.

4. The pole piece according to claim 3, wherein: An included angle α between the groove wall of the groove and the first wall surface satisfies: 30°≤α≤90°.

5. The pole piece according to claim 3, wherein: Along a direction perpendicular to the direction from the first graphite layer to the current collector, the groove runs through two ends of the first graphite layer in a straight line.

6. The pole piece according to claim 1, wherein: The first graphite layer is provided with a plurality of the grooves, and the grooves are arranged one by one at intervals.

7. The pole piece according to claim 6, wherein: The width dimension range D1 of each groove satisfies: 0.5um≤D1≤2000um, the height dimension range D2 of each groove satisfies: 3.5um≤D2≤60um, and the spacing dimension range D3 between two adjacent grooves satisfies: 0.5mm≤D3≤8mm.

8. The pole piece according to any one of claims 1 to 7, wherein: The thickness size range L1 of the first graphite layer satisfies: 3.5um≤L1≤60um, and the thickness size range L2 of the second graphite layer satisfies: 2um≤L2≤60um.

9. A battery comprising: A pole piece as claimed in any one of claims 1 to 8.

10. A method for preparing a pole piece, for manufacturing the pole piece according to any one of claims 1 to 8, comprising: Applying a first graphite layer to a current collector, and providing a plurality of grooves at intervals on the first graphite layer so that the current collector is partially exposed; A second graphite layer is coated on a side of the first graphite layer facing away from the current collector, and the second graphite layer completely covers the first graphite layer.

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