Electrode sheet, battery cell, and battery

Abstract

An electrode sheet, a battery cell, and a battery. The electrode sheet comprises a current collector, a first active material layer, and a second active material layer. In an X direction, the current collector comprises a first surface and a second surface. The first active material layer is disposed on the first surface, the first active material layer comprises a first region and a second region which are arranged in a Y direction, and the second region is adjacent to the first region. The second active material layer is disposed on the second surface, and the second active material layer and the first active material layer of the first region are oppositely arranged on the current collector in the X direction. The second region is provided with a concave part. The described electrode sheet solves the problem of the energy density of a battery cell being seriously affected due to a single-surface region of the electrode sheet having high lithium ion embedding and disengaging resistance.

Description

Electrodes, cells and batteries

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 29, 2023, with application number 202323670745.2 and application name “Electrode, Battery Cell and Battery”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a pole piece, a battery cell and a battery. Background Art

[0003] In some batteries, the positive and negative electrodes have double-sided areas and single-sided areas. The double-sided area refers to the electrode having active material layers on both sides, and the single-sided area refers to the electrode having active material layers on one side and no active material layers on the other side. In particular, during the rolling process of the positive electrode of a lithium-ion battery, when the positive electrode is conveyed from the double-sided area to the single-sided area, the pressure applied to the single-sided area of ​​the positive electrode cannot be replenished in time, resulting in a large thickness and low compaction in the single-sided area of ​​the positive electrode. The compaction of the single-sided area of ​​the positive electrode is lower than that of the double-sided area, and the contact between particles and even between particles and the conductive agent is not as close, resulting in reduced electronic conductivity, resulting in high resistance to lithium ions in the single-sided area of ​​the positive electrode escaping from the positive electrode, which seriously affects the energy density of the battery cell.

[0004] Application Contents

[0005] The main purpose of the present application is to provide a pole piece, a battery cell and a battery to solve the problem that the resistance of lithium ions in a single-sided area of ​​the positive pole piece to escape from the positive pole piece is large, which seriously affects the energy density of the battery cell.

[0006] According to one aspect of the present application, a pole piece is provided, comprising:

[0007] A current collector, along the X direction, the current collector including a first surface and a second surface;

[0008] a first active material layer, the first active material layer being disposed on the first surface, the first active material layer comprising a first region and a second region disposed along the Y direction, the second region being adjacent to the first region;

[0009] a second active material layer, the second active material layer being disposed on the second surface, and the second active material layer and the first active material layer in the first region being disposed on the current collector opposite to each other along the X direction;

[0010] Wherein, a recessed portion is provided on the second area.

[0011] Furthermore, the recessed portion includes a plurality of recessed portions, and the plurality of recessed portions are arranged along the second area.

[0012] Further, along the Z direction, the second region (D2) includes a first edge and a second edge, and the distance between one end of the recessed portion close to the first edge and the first edge is between 0 microns and 500 microns; and / or, the distance between one end of the recessed portion close to the second edge and the second edge is between 0 microns and 500 microns.

[0013] Furthermore, the recessed portion includes at least one of a circular hole, a polygonal hole, an elliptical hole, and a funnel-shaped hole.

[0014] Furthermore, the recessed portion has a depth along the X direction, and the first active material layer has a thickness along the X direction, wherein a ratio of the depth to the thickness is greater than or equal to 1:30 and less than 1:1.

[0015] Furthermore, the recessed portion has a depth along the X direction and a width along the Y direction, the depth is between 2 microns and 40 microns, and / or the width is between 30 microns and 200 microns, and / or the spacing between two adjacent recessed portions is between 50 microns and 2000 microns.

[0016] According to another aspect of the present application, a battery cell is provided, comprising:

[0017] The first pole piece is the pole piece provided in the above content of this application.

[0018] Furthermore, a recessed portion is provided on the second region of the first pole piece, and the recessed portion has a depth along the X direction. The battery cell further comprises:

[0019] A second pole piece, wherein the second pole piece and the first pole piece have a predetermined mass specific capacity, and a ratio of the predetermined mass specific capacity to the depth is between 0.034 and 0.171.

[0020] Furthermore, the battery cell includes a winding core, and the second region of the first pole piece is located at a winding end of the winding core.

[0021] Furthermore, the second region of the first pole piece is arranged opposite to the active material layer on the second pole piece.

[0022] Furthermore, the end of the second region of the first pole piece away from the first region (D1) does not exceed the end of the active material layer on the second pole piece.

[0023] Furthermore, it also includes:

[0024] A diaphragm is arranged between the first pole piece and the second pole piece. Along the thickness direction of the battery cell, the distance between the bottom of the recessed portion of the first pole piece and the diaphragm is a first distance, and the distance between the first area of ​​the first pole piece and the diaphragm is a second distance. The first distance is greater than the second distance.

[0025] Furthermore, the first pole piece includes a first bending section, and the initial setting position of the recessed portion of the first pole piece is located in the first bending section.

[0026] According to another aspect of the present application, a battery is provided, comprising the battery cell.

[0027] Compared with the existing technology, the technical solution of this application has at least the following technical effects:

[0028] The present application increases the effective surface area of ​​the electrode by providing a recessed portion on the second region of the first active material layer of the electrode. The recessed portion has a small thickness and a large surface area. The electrode can store more electrolyte in the recessed portion to enhance the wettability of the electrode by the electrolyte, which is beneficial to the infiltration and transmission of the electrolytic ions generated by the electrode in the electrolyte, and improves the deintercalation rate of the electrolytic ions. During charging and discharging, the electrolyte stored in the recessed portion can conduct the electrolytic ions released from the first electrode faster and embed them into the second electrode, preventing lithium deposition in the battery cell, thereby improving the energy density and energy output of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0030] FIG1 is a schematic structural diagram of a pole piece provided in one embodiment of the present application;

[0031] FIG2 is a schematic structural diagram of a recessed portion provided in the second region of FIG1 ;

[0032] FIG3 is a schematic diagram showing the positions of the first area, the second area and the third area on the electrode;

[0033] FIG4 is a schematic structural diagram of a battery cell provided in one embodiment of the present application.

[0034] Among them, the above-mentioned drawings include the following figure marks: 10, current collector; 11, first surface; 12, second surface; 20, first active material layer; 21, recessed portion; D1, first region; D2, second region; 22, first edge; 23, second edge; 30, second active material layer; 40, finishing tape; 50, battery cell; 51, first pole piece; 511, first bending section; 52, second pole piece; 53, diaphragm; 60, tape. DETAILED DESCRIPTION

[0035] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0036] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0037] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to actual proportional relationships. The techniques, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific values ​​should be interpreted as being merely exemplary, not as limitations. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0038] In order to solve the problem that the lithium ion insertion and extraction resistance in the single-sided area is large, the ohmic impedance and electrochemical polarization are large, and the energy density of the battery cell 50 is seriously affected. The first embodiment of the present application provides a pole piece, as shown in Figure 1, which includes a current collector 10, a first active material layer 20 and a second active material layer 30. Along the X direction shown in Figure 1 (that is, the thickness direction of the pole piece), the current collector 10 includes a first surface 11 and a second surface 12. The first active material layer 20 is arranged on the first surface 11, and the first active material layer 20 includes a first area D1 and a second area D2 arranged along the Y direction (that is, the length direction of the pole piece), and the second area D2 is adjacent to the first area D1, wherein the Y direction is perpendicular to the X direction. The second active material layer 30 is arranged on the second surface 12, and the second active material layer 30 and the first active material layer 20 of the first area D1 are arranged on the current collector 10 along the X direction. Among them, a recessed portion 21 is provided on the second area D2.

[0039] Therefore, since the current collector 10 is provided with an active material layer on both the first surface 11 and the second surface 12 of its first region D1, and the active material layer is only provided on the first surface 11 of its second region D2. Even if the compaction of the second region D2 is not as high as that of the first region D1, since the embodiment of the present application is provided with a recessed portion 21 on the second region D2, the recessed portion 21 can increase the effective surface area of ​​the first active material layer 20 on the electrode. The larger the effective surface area, the more electrolyte can be stored in the battery cell 50 made using the electrode to enhance the wettability of the electrode by the electrolyte. More electrolyte can increase the rate of electrolytic ion deintercalation. This increases the energy density of the battery cell 50. The greater the energy density of the battery cell 50, the greater its energy output.

[0040] It can be seen that the embodiment of the present application increases the effective surface area of ​​the electrode by providing a recessed portion 21 on the second area D2 of the first active material layer 20 of the electrode. The recessed portion 21 has a small thickness and a large surface area, which enables the electrode to store more electrolyte through the recessed portion 21 to enhance the wettability of the electrode by the electrolyte, which is beneficial to the infiltration and transmission of the electrolytic ions generated by the electrode in the electrolyte, and improves the deintercalation rate of the electrolytic ions. When the battery cell 50 is charging and discharging, if the positive electrode of the battery cell 50 is the first electrode 51 and the negative electrode is the second electrode 52, a recessed portion 21 is provided on the first electrode 51, and the electrolyte stored in the recessed portion 21 can conduct the electrolytic ions released from the first electrode 51 faster and embed them into the second electrode 52, preventing the battery cell 50 from producing lithium plating, thereby improving the energy density and energy output of the battery cell 50. Secondly, although the second area D2 (i.e., the single-sided area) of the first electrode 51 is not as compacted as the double-sided area. However, after rolling, a dense film will form on the surface of the second region D2 of the first electrode sheet 51, which will hinder the escape of lithium ions. However, the recessed portion 21 provided in the second region D2 of the first electrode sheet 51 in this embodiment is equivalent to damaging the dense film to a certain extent, further reducing the escape resistance of the electrolytic ions in the second region D2. After the electrolytic ions escape, they can be conducted by the electrolyte and embedded in the second electrode sheet 52, preventing lithium deposition.

[0041] Moreover, since the recessed portion 21 stores more electrolyte, which speeds up the conduction of electrolytic ions such as lithium ions, it can also reduce electrochemical polarization and concentration polarization. Electrochemical polarization is a type of electrode polarization. Under the action of an external electric field, the change in electrode potential caused by the sluggishness of electrochemical action relative to electron movement changes the original electric double layer, which is called electrochemical polarization. Its characteristics are: due to chemical control, excessive electrons accumulate on the electrode surface at the electron outflow end (negative pole of the power supply, cathode of the electrolytic cell), that is, the electrode potential tends to be negative; the opposite is true at the electron inflow end (positive pole of the power supply, anode of the electrolytic cell). This causes the potential difference between the electrodes to decrease. Concentration polarization is when a current passes through the electrode. If the rate of chemical reaction at the electrode-solution interface is faster and the diffusion rate of ions in the solution is slower, the concentration of the relevant ions near the electrode surface will be different from that in the bulk solution away from the electrode. In this embodiment, due to the improvement in the deintercalation rate of the electrolytic ions, the electrolytic ions released from the first electrode 51 can be conducted faster and embedded in the second electrode 52. The electrolytic ions will not accumulate excessively at either end, but will diffuse out quickly and embed in the second electrode 52, thereby improving both concentration polarization and electrochemical polarization.

[0042] Lithium deposition occurs when electrolytic ions (such as lithium ions in a lithium-ion battery) that should have entered the interior of the second electrode 52 are forced to precipitate on the surface of the second electrode 52. This embodiment utilizes the recessed portion 21 provided in the second region D2 of the electrode to store more electrolyte, thereby increasing the rate of electrolytic ion insertion and extraction, and reducing electrochemical polarization and concentration polarization, thereby preventing lithium deposition.

[0043] Secondly, because different battery cells 50 in a battery pack often have uneven performance due to differences in manufacturing and use, the embodiment of the present application can ensure the performance balance of each battery cell 50 in the battery pack by providing a recessed portion 21 for increasing the surface area of ​​the electrode sheet in the second region D2 of the first electrode sheet 51. That is, according to the performance of each battery cell 50 in the battery pack, different sizes or numbers of recessed portions 21 are provided in the second region D2 of the electrode sheet of different battery cells 50. This reduces the performance differences between the battery cells 50 and improves the performance consistency of the entire battery pack.

[0044] Moreover, the embodiment of the present application can also improve the cycle life of the battery cell 50 by providing a recessed portion 21 on the electrode. Since the recessed portion 21 can increase the available surface area of ​​the electrode in the first active material layer 20, the electrode with an increased surface area can reduce the electrode reaction rate during the charge or discharge process, reduce the loss and structural changes of the electrode material, and thus extend the service life of the battery. In addition, providing the recessed portion 21 in the second area D2 of the electrode can also improve the safety of the battery cell 50: after the available surface area of ​​the electrode is increased by providing the recessed portion 21, the heat distribution of the battery cell 50 is more uniform, which helps to dissipate heat and reduce the generation of hot spots, which can reduce the risk of overheating and thermal runaway of the battery and improve the safety of the battery.

[0045] In the embodiment of the present application, a recessed portion 21 can be processed on the second area D2 of the first active material layer 20 of the electrode by laser or mechanical processing equipment. The recessed portion 21 can be set during the process of coating the first active material layer 20 or after rolling. The processing method is flexible and easy to implement.

[0046] Among them, the recessed portion 21 includes a plurality of recessed portions 21, and the plurality of recessed portions 21 can be arranged regularly or irregularly in the second area D2. When the plurality of recessed portions 21 are regularly arranged in the second area D2, they can be arranged in the second area D2 in at least one row along the Y direction, and / or, the plurality of recessed portions 21 can be arranged in the second area D2 in at least one column along the Z direction. In the embodiment of the present application, after determining the number of recessed portions 21 set in the second area D2 of the electrode according to the energy density to be achieved by the battery cell 50, the plurality of recessed portions 21 with a predetermined number can be arranged in the second area D2 of the first active material layer 20 of the electrode, thereby increasing the effective surface area of ​​the electrode. The larger the effective surface area of ​​the electrode, the more electrolyte the battery cell 50 can store. The more electrolyte there is, the higher the deintercalation rate of the electrolytic ions, and the greater the energy density of the battery cell 50.

[0047] Along the Z direction, the first region D1 in this embodiment includes a first edge 22 and a second edge 23. When the recessed portion 21 is arranged on the second region D2 of the first active material layer 20, the distance between the end of the recessed portion 21 closest to the first edge 22 and the first edge 22 (J1 as shown in FIG2 ) is set to be between 0 μm and 500 μm. And / or, the distance between the end of the recessed portion 21 closest to the second edge 23 and the second edge 23 is set to be between 0 μm and 500 μm. For example, the distance between the recessed portion 21 and the first edge 22 and the second edge 23 can be set to any of 0 μm (in this case, the recessed portion 21 is arranged along the z direction of the electrode through the first active material layer 20), 2 μm, 5 μm, 10 μm, 30 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, and 500 μm. The Z direction is perpendicular to the X and Y directions.

[0048] The recessed portion 21 provided in the embodiment of the present application includes at least one of a circular hole, a polygonal hole, an elliptical hole, and a funnel-shaped hole. A circular hole is a hole with a circular cross-section, a polygonal hole is a hole with a polygonal cross-section, an elliptical hole has an elliptical cross-section, and a funnel-shaped hole is a hole whose cross-section gradually decreases from the first surface 11 to the second surface 12. The present application can provide a recessed portion 21 of one form on the first area D1 of the pole piece according to actual needs, such as providing only a circular hole or a polygonal hole as the recessed portion 21 provided in the first area D1, thereby increasing the available surface area of ​​the pole piece. A plurality of different types of recessed portions 21 can also be provided on the same pole piece, such as a combination of a circular hole and a polygonal hole, a combination of a polygonal hole and an elliptical hole, a combination of a circular hole, a polygonal hole, and an elliptical hole, etc. Regardless of how many forms of recesses 21 are provided on the electrode, the plurality of recesses 21 can be arranged in at least one row in the second region D2 along the Y direction, and in at least one column in the second region D2 along the Z direction, thereby increasing the surface area of ​​the electrode to store more electrolyte.

[0049] In the embodiment of the present application, the recessed portion 21 has a depth along the X-direction, and the first active material layer 20 has a thickness along the X-direction, wherein the ratio between the depth and the thickness is greater than or equal to 1:30 and less than 1:1. For example, the ratio between the depth and the thickness is set to include any ratio of 1:1.5, 1:2, 1:5, 1:8, 1:10, 1:15, 1:20, 1:25, and 1:30, wherein the symbol ":" represents an operator ratio. By setting the ratio between the depth and the thickness to be greater than or equal to 1:30, the recessed portion 21 can effectively increase the surface area of ​​the electrode. In a preferred embodiment of the present application, the ratio between the depth and the thickness is set to be greater than or equal to 1 to 15 and less than or equal to 1 to 5. For example, the ratio between the depth and the thickness is set to include any ratio of 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, etc., to ensure that the recessed portion 21 can effectively increase the surface area of ​​the electrode.

[0050] The depressed portion 21 in the embodiment of the present application also has a width along the Y direction, and the depth of the depressed portion 21 is between 2 microns and 40 microns, and the width of the depressed portion 21 is between 30 microns and 200 microns, and the spacing between two adjacent depressed portions 21 is between 50 microns and 2000 microns. The specific value of the depth of the depressed portion 21 includes any value in the depth values ​​such as 2 microns, 4 microns, 6 microns, 8 microns, 10 microns, 15 microns, 20 microns, 25 microns, 27 microns, 28 microns, 30 microns, 31 microns, 33 microns, 35 microns, 37 microns, 38 microns, and 40 microns. The specific value of the width of the depressed portion 21 is one of 30 microns, 50 microns, 70 microns, 80 microns, 90 microns, 100 microns, 130 microns, 140 microns, 150 microns, 170 microns, 180 microns, and 200 microns. In a preferred embodiment of the present application, the depth of the recessed portion 21 is between 3 microns and 20 microns, that is, the preferred value of the depth of the recessed portion 21 includes any value of 4 microns, 6 microns, 8 microns, 10 microns, 12 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns, 20 microns, etc. In a preferred embodiment of the present application, the width of the recessed portion 21 is between 50 microns and 150 microns, specifically, the preferred value of the width of the recessed portion 21 includes any value of 50 microns, 70 microns, 80 microns, 90 microns, 100 microns, 130 microns, 140 microns, 150 microns, etc. The spacing between two adjacent recesses 21 (i.e., J2 as shown in FIG. 2 ) is between 50 μm and 2000 μm. The spacing J2 may be any value of 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 700 μm, 900 μm, 1000 μm, 1500 μm, 2000 μm, etc. Preferably, the spacing J2 between two adjacent recesses 21 is between 100 μm and 500 μm. The preferred value of the spacing J2 may be any value of 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, etc.

[0051] Specifically, the shape of the recessed portion provided in this embodiment is preferably a funnel-shaped hole. The funnel-shaped hole can be conveniently and quickly processed and set in the second area D2 of the pole piece by laser drilling. The process is simple and the processing efficiency is high, thereby reducing the production cost of the pole piece due to the difficulty of the processing technology. Along the X direction, the cross-sectional area of ​​the funnel-shaped hole gradually increases, and the depth of the funnel-shaped hole along the X direction is between 2 microns and 40 microns. In the embodiment of the present application, the specific value of the depth of the funnel-shaped hole includes any value of the depth values ​​of 2 microns, 4 microns, 6 microns, 8 microns, 10 microns, 15 microns, 20 microns, 25 microns, 27 microns, 28 microns, 30 microns, 31 microns, 33 microns, 35 microns, 37 microns, 38 microns, 40 microns, etc. The width of the funnel-shaped hole along the Y direction, i.e., the pore diameter of the funnel-shaped hole on the surface of the second region D2 (the surface of the second region D2 away from the current collector 10), is between 30 μm and 200 μm. Specific values ​​of the pore diameter include any of 30 μm, 50 μm, 70 μm, 80 μm, 90 μm, 100 μm, 130 μm, 140 μm, 150 μm, 170 μm, 180 μm, 200 μm, etc. In a preferred embodiment of the present application, the depth of the funnel-shaped hole is between 3 μm and 20 μm. Preferred values ​​of the pore depth include any of 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, etc. In a preferred embodiment of the present application, the diameter of the funnel-shaped holes is between 50 and 150 microns. Specifically, the preferred values ​​of the diameter include any of 50, 70, 80, 90, 100, 130, 140, and 150 microns. The spacing between two adjacent funnel-shaped holes (i.e., J2 as shown in FIG2 ) is between 50 and 2000 microns. For example, the spacing J2 includes any of 50, 100, 200, 300, 400, 500, 700, 900, 1000, 1500, and 2000 microns. Preferably, the spacing J2 between two adjacent funnel-shaped holes is between 100 and 500 microns. Specifically, the preferred values ​​of the spacing J2 include any of 100, 200, 300, 400, and 500 microns.

[0052] In another embodiment of the present application, the depth of the recessed portion 21 is between 2 microns and 40 microns, the width of the recessed portion 21 is between 30 microns and 200 microns, and the spacing between two adjacent recessed portions 21 is between 100 microns and 5000 microns. Specifically, the depth of the recessed portion 21 includes any value selected from the group consisting of 2 microns, 3 microns, 4 microns, 5 microns, 8 microns, 10 microns, 12 microns, 14 microns, 20 microns, 25 microns, 30 microns, and 40 microns. The width of the recessed portion 21 includes any value selected from the group consisting of 30 microns, 50 microns, 80 microns, 90 microns, 100 microns, 130 microns, 150 microns, 180 microns, and 200 microns. The spacing between two adjacent recesses 21 includes any value selected from 100 microns, 200 microns, 300 microns, 400 microns, 600 microns, 800 microns, 1000 microns, 1500 microns, 2000 microns, 2500 microns, 3000 microns, 4000 microns, 4500 microns, and 5000 microns. Preferably, the depth of the recesses 21 is between 3 microns and 30 microns, with preferred values ​​for the depth including any value selected from 3 microns, 4 microns, 5 microns, 8 microns, 10 microns, 12 microns, 14 microns, 20 microns, 25 microns, and 30 microns. The width of the recesses 21 is between 50 microns and 150 microns, with preferred values ​​for the width including any value selected from 50 microns, 80 microns, 90 microns, 100 microns, 130 microns, and 150 microns. The distance between two adjacent recessed portions 21 is between 1000 μm and 3000 μm, that is, the preferred value of the distance between two adjacent recessed portions 21 includes any value of 1000 μm, 1500 μm, 2000 μm, 2500 μm, and 3000 μm.

[0053] Specifically, when the recessed portion 21 provided in this embodiment is a polygonal hole, the width of the polygonal hole along the Y direction is k as shown in FIG2 . The polygonal hole includes a rectangular hole with a rectangular cross-section. The width k of the rectangular hole along the Y direction is between 30 μm and 200 μm, and the depth of the rectangular hole along the X direction is between 2 μm and 40 μm. Specifically, the value of the rectangular hole width k includes any value of 30 μm, 50 μm, 80 μm, 90 μm, 100 μm, 130 μm, 150 μm, 180 μm, and 200 μm, and the value of the rectangular hole depth includes any value of 2 μm, 3 μm, 4 μm, 5 μm, 8 μm, 10 μm, 12 μm, 14 μm, 20 μm, 25 μm, 30 μm, and 40 μm. The distance between two adjacent rectangular holes (J3 as shown in Figure 2) is between 100 microns and 5000 microns. The specific value of the distance J3 may include: any value of 100 microns, 200 microns, 300 microns, 400 microns, 600 microns, 800 microns, 1000 microns, 1500 microns, 2000 microns, 2500 microns, 3000 microns, 4000 microns, 4500 microns, and 5000 microns.

[0054] In a preferred embodiment of the present application, the width k of the rectangular hole is between 50 μm and 150 μm, that is, the preferred value of the width k includes any value of 50 μm, 80 μm, 90 μm, 100 μm, 130 μm, and 150 μm. The depth of the rectangular hole is between 3 μm and 30 μm, and the preferred value of the depth includes any value of 3 μm, 4 μm, 5 μm, 8 μm, 10 μm, 12 μm, 14 μm, 20 μm, 25 μm, and 30 μm. The spacing J3 between two adjacent rectangular holes is between 1000 μm and 3000 μm, that is, the preferred value of the spacing J3 includes any value of 1000 μm, 1500 μm, 2000 μm, 2500 μm, and 3000 μm.

[0055] As shown in Figure 3, in an embodiment of the present application, the first active material layer 20 located on the first surface 11 of the current collector 10 and the second active material layer 30 on the second surface 12 are aligned in the first area D1 of the current collector 10 and staggered in the second area D2 (that is, only the first active material layer 20 exists in the second area D2). In the embodiment of the present application, regularly or irregularly arranged recesses 21 can be directly distributed in the second area D2. Specifically, the recesses 21 arranged on the second area D2 are arranged along the Y direction to the electrode finishing tape 40, which effectively increases the surface area of ​​the electrode, thereby increasing the energy density of the battery cell 50 including the electrode, the performance balance between the battery cell 50 and another battery cell 50, the cycle life of the battery cell 50, etc.

[0056] The second embodiment of the present application provides a battery cell 50, which includes a first electrode 51. The first electrode 51 is the electrode provided in the first embodiment of the present application. The specific structure of the electrode is provided in the first embodiment of the present application, and will not be repeated here.

[0057] As shown in Figure 4, the battery cell 50 also includes a second electrode sheet 52. In this embodiment, the first electrode sheet 51 is a positive electrode sheet, and the second electrode sheet 52 is a negative electrode sheet. A recessed portion 21 is provided in the second region D2 of the first electrode sheet 51. The recessed portion 21 has a depth along the X-direction. There are two types of battery specific capacity: mass specific capacity, which refers to the amount of energy that can be discharged per unit weight of the battery or active material. The other is volume specific capacity, which refers to the amount of energy that can be discharged per unit volume of the battery or active material. The second pole piece 52 and the first pole piece 51 have a predetermined mass specific capacity, and the ratio of the predetermined mass specific capacity (NP ratio) to the depth is between 0.034 and 0.171. The ratio of the predetermined mass specific capacity to the depth can be specifically one of 0.034, 0.038, 0.04, 0.08, 0.10, 0.12, 0.13, 0.14, 0.142, 0.146, 0.15, 0.152, 0.157, 0.159, 0.16, 0.164, 0.166, 0.17, 0.171, etc. Specifically, within the above-mentioned range of the ratio between the predetermined mass specific capacity and the depth, the predetermined mass specific capacity (NP ratio) is between 1.02 and 1.20, and the depth of the recessed portion 21 is between 7 microns and 30 microns. The depth of the recessed portion 21 may specifically be any one of 7 micrometers, 8 micrometers, 10 micrometers, 12 micrometers, 15 micrometers, 19 micrometers, 20 micrometers, 22 micrometers, 21 micrometers, 26 micrometers, 28 micrometers, and 30 micrometers. The predetermined mass specific capacity is any value of 1.02, 1.05, 1.08, 1.10, 1.12, 1.14, 1.16, 1.18, and 1.20. Secondly, the recessed portion 21 also includes a width along the Y direction, which is such as the aperture of the funnel-shaped hole located on the surface of the second region D2 or the width k of the polygonal hole. The width of the recessed portion 21 is between 30 microns and 150 microns at a predetermined mass specific capacity. For example, when the NP ratio is between 1.02 and 1.10, the width of the recessed portion 21 is one of 30 microns, 40 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 110 microns, 120 microns, 130 microns, 140 microns, 150 microns, etc.

[0058] The NP ratio in this embodiment is also called the CB value (the full name of the CB value in English is Cell Balance). It is generally understood as the excess ratio of the second pole piece 52. It is usually required that the NP ratio is ≥1 under ideal conditions. Otherwise, the lithium ions cannot be completely accepted by the second pole piece 52 after being released from the first pole piece 51. The excess lithium ions are deposited on the surface of the second pole piece 52 at a low potential, which will seriously deteriorate the battery performance and safety characteristics. Therefore, the recessed portion 21 provided in the second area D2 of the first pole piece 51 in this embodiment can also increase the CB value of the battery cell 50 and reduce lithium deposition. This is because the depth of the recessed portion 21 on the second area D2 of the first pole piece 51 can be adjusted to make the predetermined mass specific capacity between the first pole piece 51 and the second pole piece 52 between 1.02 and 1.20 (i.e., to achieve the ideal state of NP ratio ≥1). The calculation formula of the NP ratio is as follows:

[0059] In a preferred embodiment of the present application, the NP ratio is between 1.02 and 1.10. Preferred values ​​of the NP ratio include 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, and 1.10. In the embodiment of the present application, the active material capacity of the second electrode 52 is between 300 mA.h / g and 370 mA.h / g, and specific values ​​include any one of 300 mA.h / g, 310 mA.h / g, 320 mA.h / g, 330 mA.h / g, 340 mA.h / g, 350 mA.h / g, 360 mA.h / g, and 370 mA.h / g. The active material capacity of the first electrode piece 51 is between 160mA.h / g and 200mA.h / g. The specific value of the active material capacity of the first electrode piece 51 may include any value of 160mA.h / g, 163mA.h / g, 165mA.h / g, 170mA.h / g, 172mA.h / g, 175mA.h / g, 180mA.h / g, 181mA.h / g, 184mA.h / g, 185mA.h / g, 190mA.h / g, 195mA.h / g, 197mA.h / g, and 200mA.h / g. The surface density of the first pole piece 51 is between 50g / m2 and 300g / m2. The surface density of the first pole piece 51 includes any value of 50g / m2, 60g / m2, 80g / m2, 100g / m2, 120g / m2, 150g / m2, 158g / m2, 180g / m2, 200g / m2, 250g / m2, 255g / m2, 270g / m2, 280g / m2, and 300g / m2. The surface density of the second pole piece 52 is between 20g / m2 and 180g / m2. In the embodiment of the present application, the specific value of the surface density of the second pole piece 52 includes any value including 20g / m2, 30g / m2, 35g / m2, 40g / m2, 50g / m2, 60g / m2, 70g / m2, 80g / m2, 90g / m2, 100g / m2, 120g / m2, 140g / m2, 160g / m2, 170g / m2, and 180g / m2.

[0060] When the battery cell 50 includes a winding core, the second region D2 of the first pole piece 51 serving as the positive electrode (i.e., the single-sided region of the first pole piece 51) is located at the winding tail end of the winding core. The second pole piece 52 serving as the negative electrode is also generally composed of a current collector 10 and an active material layer provided on the first surface 11 and the second surface 12 of the current collector 10. The second pole piece 52 may be provided with a single-sided region at one or both ends along its own length, i.e., the portion of the second pole piece 52 located at the winding head end and / or the winding tail end of the winding core may be a single-sided region or a double-sided region. Regardless of the structural form of the second pole piece 52, the winding core in this embodiment may be outwrapped with the current collector foil through the second region D2 of the first pole piece 51 (i.e., the side of the current collector 10 of the first pole piece 51 where the active material layer is not provided is located on the surface of the winding core, to achieve foil outwrapping). The recessed portion 21 in the second region D2 of the first electrode 51 can store more electrolyte to increase the deintercalation rate of the electrolytic ions. During charging and discharging, the electrolyte stored in the recessed portion 21 can conduct the electrolytic ions released from the first electrode 51 more quickly and embed them into the second electrode 52, preventing the battery cell 50 from producing lithium plating, thereby improving the energy density and energy output of the battery cell 50.

[0061] At the same time, regardless of whether the portion of the second electrode 52 located at the winding end of the core is a single-sided area or a double-sided area, the second area D2 of the first electrode 51 must be arranged relative to the active material layer on the second electrode 52. In the case where the second area D2 of the first electrode 51 is provided with a recessed portion 21 capable of storing more electrolyte, the electrolytic ions released from the second area D2 of the first electrode 51 can be embedded in the active material layer of the second electrode 52 faster and more timely, thereby preventing the battery cell 50 from producing lithium plating. Therefore, in this embodiment, when the second area D2 of the first electrode 51 is located at the winding end of the core, by arranging the second area D2 of the first electrode 51 relative to the active material layer of the second electrode 52, it is ensured that the lithium ions generated from the first electrode 51 can be embedded in the second electrode 52, thereby avoiding the occurrence of lithium plating. Secondly, the end of the second area D2 of the first electrode 51 away from the first area D1 does not exceed the end of the active material layer of the second electrode 52.

[0062] The battery cell 50 provided in this embodiment also includes a diaphragm 53, which is arranged between the first electrode 51 and the second electrode 52. Along the thickness direction of the battery cell 50, the distance between the bottom of the recessed portion 21 of the first electrode 51 and the diaphragm 53 is a first distance, and the distance between the first area D1 of the first electrode 51 and the diaphragm 53 is a second distance. By ensuring that the first distance is greater than the second distance, it is beneficial for the battery cell 50 to store more electrolyte in the second area D2, thereby increasing the energy density of the battery cell 50.

[0063] The first pole piece 51 includes a first bent section 511. The initial location of the recessed portion 21 of the first pole piece 51 is located within the first bent section 511. Specifically, as shown in FIG4 , the first bent section 511 is the bent section of the first pole piece 51 that is closest to the end of the diaphragm 53 located at the outermost side of the winding core. The initial location of the recessed portion 21 of the first pole piece 51 is the starting point of the bend of the first bent section 511 (i.e., the intersection of the thin line and the thick line representing the outline of the first pole piece 51 in FIG4 ).

[0064] The third embodiment of the present application provides a battery, which includes a battery cell 50. For the specific structure of the battery cell 50, please refer to the content provided in the second embodiment of the present application, and the embodiment of the present application will not be repeated here.

[0065] The fourth embodiment of the present application provides an application embodiment of a pole piece based on the above three embodiments.

[0066] The electrode sheets in the embodiment of the present application include a first electrode sheet 51 and a second electrode sheet 52. The first electrode sheet 51 is a positive electrode sheet, and the second electrode sheet 52 is a negative electrode sheet. The first electrode sheet 51 includes a current collector 10, a first active material layer 20, and a second active material layer 30. The current collector 10 includes a first surface 11 and a second surface 12 along the X direction. The first active material layer 20 is provided on the first surface 11. The first active material layer 20 includes a first region D1 and a second region D2 arranged along the Y direction, and the second region D2 is adjacent to the first region D1. The second active material layer 30 is provided on the second surface 12, and the second active material layer 30 is symmetrically arranged with the first active material layer 20 in the first region D1.

[0067] Among them, the first active material layer 20 located on the first surface 11 and the second active material layer 30 on the second surface 12 of the first electrode 51 are aligned in the first area D1 of the current collector 10 (that is, the active material layers on both sides of the current collector 10 are aligned, which is the double-sided area of ​​the first electrode 51), and staggered in the second area D2 (that is, only the first active material layer 20 exists in the second area D2, which is the single-sided area of ​​the first electrode 51). In the application embodiment of the present application, regularly arranged or irregularly arranged recessed portions 21 can be provided in the second area D2 of the first electrode 51 to increase the deintercalation rate of the electrolytic ions and prevent lithium precipitation. Specifically, the recessed portion 21 on the first electrode 51 is arranged along the Y direction from the junction of the second area D2 and the first area D1 to the tail end of the second area D2 away from the first area D1, and ends in the tail adhesive tape 40 of the electrode (as shown in Figure 2).

[0068] The recessed portion 21 in this embodiment increases the surface area of ​​the first electrode 51, enabling the electrode to store more electrolyte through the recessed portion 21 to enhance the wettability of the electrode by the electrolyte, which is beneficial to the infiltration and transmission of the electrolytic ions generated by the electrode in the electrolyte, and improves the deintercalation rate of the electrolytic ions. During charging and discharging, the electrolyte stored in the recessed portion 21 can conduct the electrolytic ions released from the first electrode 51 faster and embed them into the second electrode 52, preventing the battery cell 50 from producing lithium deposition, thereby improving the energy density and energy output of the battery cell 50. Secondly, the presence of the recessed portion 21 is equivalent to a certain degree of damage to the dense film on the electrode, further reducing the escape resistance of the electrolytic ions in the second region D2, and reducing the electrochemical polarization and concentration polarization. This increases the energy density of the battery cell 50. This embodiment can also provide recesses 21 of different sizes or numbers in the second region D2 of the electrode sheets of different battery cells 50, depending on the performance of each battery cell 50 in the battery pack, to ensure balanced performance of each battery cell 50 in the battery pack. Furthermore, because the recesses 21 can increase the available surface area of ​​the electrode sheet in the first active material layer 20, the increased surface area of ​​the electrode sheet can reduce the electrode reaction rate during charge or discharge, reduce electrode material loss and structural changes, and thus extend the battery's service life. Furthermore, by increasing the available surface area of ​​the electrode sheet through the provision of the recesses 21, the heat distribution of the battery cell 50 is also more uniform, which helps dissipate heat and reduce the generation of hot spots. This can reduce the risk of overheating and thermal runaway of the battery, thereby improving battery safety.

[0069] Along the Z direction, the first region D1 in this embodiment includes a first edge 22 and a second edge 23. When the recessed portion 21 is arranged on the second region D2 of the first pole piece 51, the distance between the end of the recessed portion 21 near the first edge 22 and the first edge 22 (J1 as shown in FIG2 ) is set to be between 0 μm and 500 μm. If the recessed portion 21 is a circular hole or a funnel-shaped hole, the distance between the endpoint of the circular hole or funnel-shaped hole near the first edge 22 and the first edge 22 is between 0 μm and 500 μm. The distance between the end of the recessed portion 21 near the second edge 23 and the second edge 23 is between 0 μm and 500 μm. If the recessed portion 21 is a circular hole or a funnel-shaped hole, the distance between the endpoint of the circular hole or funnel-shaped hole near the second edge 23 and the second edge 23 is between 0 μm and 500 μm. For example, the distance between the recessed portion 21 and the first edge 22 and / or the second edge 23 can be set to specifically include any distance value of 0 micron (i.e., the recessed portion 21 is set on the first active material layer 20 along the z direction of the pole piece), 2 microns, 5 microns, 10 microns, 30 microns, 50 microns, 100 microns, 200 microns, 300 microns, 400 microns, and 500 microns.

[0070] In the embodiment of the present application, the recessed portion 21 has a depth along the X direction, and the first active material layer 20 has a thickness along the X direction, wherein the ratio between the depth and the thickness is greater than or equal to 1:30 and less than 1:1. By setting the ratio between the depth and the thickness to be greater than or equal to 1:30, the recessed portion 21 can effectively increase the surface area of ​​the electrode. In a preferred embodiment of the present application, the ratio between the depth and the thickness is set to be less than 1:5 and greater than or equal to 1:15.

[0071] There are two types of specific capacity of batteries, one is mass specific capacity, that is, the amount of electricity that can be discharged by a unit weight of a battery or active material. The other is volume specific capacity, that is, the amount of electricity that can be discharged by a unit volume of a battery or active material. In this embodiment, the ratio between the predetermined mass specific capacity between the first pole piece 51 and the second pole piece 52 and the depth of the recess 21 is between 0.034 and 0.171. Specifically, within the above-mentioned ratio range between the predetermined mass specific capacity and the depth of the recess 21, the predetermined mass specific capacity is between 1.02 and 1.20, and the depth value of the depth of the recess 21 is between 7 microns and 30 microns. That is, the depth of the recess 21 set on the first pole piece 51 in the embodiment of the present application must be such that the predetermined mass specific capacity (referred to as NP ratio) of the first pole piece 51 and the second pole piece 52 satisfies:

[0072] In a preferred embodiment, the depth of the recessed portion 21 is a depth at which the NP ratio is between 1.02 and 1.10. In the embodiment of the present application, the active material capacity of the second pole piece 52 is between 300 mA.h / g and 370 mA.h / g, the active material capacity of the first pole piece 51 is between 160 mA.h / g and 200 mA.h / g, the surface density of the first pole piece 51 is between 50 g / m2 and 300 g / m2, and the surface density of the second pole piece 52 is between 20 g / m2 and 180 g / m2.

[0073] The shape of the recessed portion 21 provided in the second region D2 of the first pole piece 51 is preferably a funnel-shaped hole or a rectangular hole. The diameter of the funnel-shaped hole located on the surface of the second region D2 is between 30 and 200 microns, preferably between 50 and 150 microns. The depth of the funnel-shaped hole along the X direction is between 2 and 30 microns, preferably between 3 and 20 microns, and the spacing J2 between two adjacent funnel-shaped holes is between 50 and 2000 microns. Preferably, the spacing J2 between two adjacent funnel-shaped holes is between 100 and 500 microns. The width k of the rectangular hole is between 30 and 200 microns, preferably between 50 and 150 microns, and the depth of the rectangular hole is between 2 and 40 microns. Preferably, the depth of the rectangular holes along the X-direction is between 3 and 30 microns, and the spacing J3 between adjacent rectangular holes is between 100 and 5000 microns. Preferably, the spacing J3 between adjacent rectangular holes is between 100 and 3000 microns. When multiple funnel-shaped holes and / or rectangular holes are arranged in the second region D2, as shown in FIG2 , the funnel-shaped holes on the first active material layer 20 are arranged in three rows and multiple columns, with the number of columns depending on the length of the second region D2 in the Y-direction. The arrangement of the funnel-shaped holes begins at the junction of the second region D2 and the first region D1 and ends within the adhesive tape 40. The rectangular holes are arranged on the first active material layer 20 with or without penetrating the first active material layer 20 along the Z-direction. The arrangement of the rectangular holes begins at the junction of the second region D2 and the first region D1 and ends within the adhesive tape 40.

[0074] The funnel-shaped holes or rectangular holes on the first electrode piece 51 provided in this application embodiment can be set on the current collector 10 with a thickness ranging from 7 microns to 15 microns, which is suitable for thick electrode pieces with high energy density, and can also be set on high-rate thin electrode pieces.

[0075] The funnel-shaped or rectangular hole in the first pole piece 51 can be formed by laser or mechanical means, and can be formed after the first pole piece 51 is coated or rolled, etc., which makes the manufacturing method flexible and convenient. The obtained first pole piece 51 can be used in wound lithium-ion batteries or laminated lithium-ion batteries.

[0076] As shown in Figure 4, when the first electrode 51 provided in the application embodiment of the present application is applied to a wound lithium-ion battery, the lithium-ion battery includes a winding core structure formed by winding the first electrode 51, the second electrode 52, the separator 53 and the adhesive tape 60. As shown in Figure 4, the thick line representing the thicker part of the outline of the first electrode 51 represents the second area D2 of the first electrode 51, and the thick line representing the thicker part of the outline of the second electrode 52 represents the double-sided area of ​​the second electrode 52. The second area D2 of the first electrode 51 is wound at the tail of the battery cell 50 (i.e., the outer layer of the battery cell 50). The end of the second area D2 of the first electrode 51 away from the first area D1 does not exceed the end of the active material layer of the second electrode 52. The starting point of the recessed portion 21 provided in the second area D2 of the first electrode 51 is located at the starting point of the bend of the first bending section 511 of the first electrode 51 (i.e., the intersection of the thin line and the thick line of the first electrode 51 in Figure 4). Along the thickness direction of the battery cell 50, the distance between the recessed portion 21 of the second region D2 of the first electrode 51 and the diaphragm 53 is greater than the distance between the first region D1 and the diaphragm 53, which is beneficial for the battery cell 50 to store more charge in the second region D2, thereby increasing the energy density of the battery cell 50.

[0077] During the production of the first electrode sheet 51, the first electrode sheet 51, after being coated with the active material layer, is rolled using a roller to achieve the thickness and compaction density required by the process. A laser is then used to create a recessed portion 21 in the second region D2 of the first electrode sheet 51. During this process, the laser power, speed, filling spacing, frequency, and other parameters are controlled to form an electrolyte recessed portion 21 in the second region D2 of the first electrode sheet 51. The first electrode sheet 51, which has already been pierced or polygonally grooved, is then laser cleaned to remove the soft tab area. The cleaned first electrode sheet 51 is then die-cut.

[0078] After the first pole piece 51 provided in the embodiment of the present application is provided with the recessed portion 21 in the second region D2, the first pole piece 51 has the following advantages:

[0079] 1) Improving the energy density of the battery cell: The recessed portion 21 provided in the second region D2 of the first electrode 51 can increase the effective surface area of ​​the first electrode 51, thereby improving the energy density of the battery cell 50. By increasing the available area of ​​the first electrode 51, the battery cell 50 can store more charge and provide higher energy output.

[0080] 2) Improving the performance balance of the battery cells 50: Since different battery cells 50 in a battery pack often have uneven performance due to differences in manufacturing and use, the embodiment of the present application can ensure the performance balance of each battery cell 50 in the battery pack by providing a recessed portion 21 for increasing the surface area of ​​the electrode sheet in the second region D2 of the first electrode sheet 51. That is, according to the performance of each battery cell 50 in the battery pack, different sizes or numbers of recessed portions 21 are provided in the second region D2 of the first electrode sheet 51 of different battery cells 50. This reduces the performance differences between the battery cells 50 and improves the performance consistency of the entire battery pack.

[0081] 3) Improve the cycle life of the battery cell 50: Since the recessed portion 21 can increase the available surface area of ​​the electrode in the first active material layer 20, the electrode with increased surface area can reduce the electrode reaction speed during charge or discharge, reduce the loss and structural changes of the electrode material, and thus extend the service life of the battery.

[0082] 4) Improved safety: By increasing the available surface area of ​​the electrode by providing the recessed portion 21, the heat distribution of the battery cell 50 is more uniform, which helps to dissipate heat and reduce the generation of hot spots, which can reduce the risk of overheating and thermal runaway of the battery and improve the safety of the battery.

[0083] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0084] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0085] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A pole piece, characterized in that, Comprising: A current collector (10), along the X direction, the current collector (10) includes a first surface (11) and a second surface (12); A first active material layer (20), the first active material layer (20) is disposed on the first surface (11), the first active material layer (20) includes a first region (D1) and a second region (D2) disposed along the Y direction, the second region (D2) is adjacent to the first region (D1); A second active material layer (30), the second active material layer (30) is disposed on the second surface (12), and the second active material layer (30) and the first active material layer (20) of the first region (D1) are disposed opposite to each other along the X direction on the current collector; Wherein, a recess (21) is provided on the second region (D2).

2. The electrode sheet according to claim 1, wherein, There are multiple recesses (21), and the multiple recesses (21) are arranged on the second region (D2).

3. The pole piece according to claim 1, wherein Along the Z direction, the second region (D2) includes a first edge (22) and a second edge (23), and the distance between one end of the recess (21) close to the first edge (22) and the first edge (22) is between 0 micrometers and 500 micrometers; and / or, the distance between one end of the recess (21) close to the second edge (23) and the second edge (23) is between 0 micrometers and 500 micrometers.

4. The pole piece according to any one of claims 1 to 3, characterized in that, The recess (21) includes at least one of a circular hole, a polygonal hole, an elliptical hole, and a funnel-shaped hole.

5. The pole piece according to any one of claims 1 to 3, characterized in that, The recess (21) has a depth along the X direction, and the first active material layer (20) has a thickness along the X direction, wherein the ratio of the depth to the thickness is greater than or equal to 1:30 and less than 1:

1.

6. The pole piece according to any one of claims 1 to 3, characterized in that, The recess (21) has a depth along the X direction and a width along the Y direction, the depth is between 2 micrometers and 40 micrometers, and / or, the width is between 30 micrometers and 200 micrometers, and / or, the distance between two adjacent recesses (21) is between 50 micrometers and 2000 micrometers.

7. A battery cell, characterized in that, The battery cell (50) includes: A first pole piece (51), the first pole piece (51) is the pole piece according to any one of claims 1 to 6.

8. The battery cell according to claim 7, wherein A recess (21) is provided on the second region (D2) of the first pole piece (51), the recess (21) has a depth along the X direction, and the battery cell (50) further includes: A second pole piece (52), and there is a predetermined mass specific capacity between the second pole piece (52) and the first pole piece (51), and the ratio of the predetermined mass specific capacity to the depth is between 0.034 and 0.

171.

9. The battery cell according to claim 7, wherein The battery cell includes a wound core, and the second region (D2) of the first pole piece (51) is located at the winding end of the wound core.

10. The battery cell according to claim 8, wherein, The second region (D2) of the first pole piece (51) is disposed opposite to the active material layer on the second pole piece (52).

11. The battery cell according to claim 10, characterized in that, The end of the second region (D2) of the first pole piece (51) away from the first region (D1) does not extend beyond the end of the active material layer on the second pole piece (52).

12. The battery cell according to claim 8, wherein, Further comprising: A separator (53), the separator (53) is disposed between the first electrode plate (51) and the second electrode plate (52). Along the thickness direction of the battery cell (50), the distance between the bottom of the concave portion (21) of the first electrode plate (51) and the separator (53) is a first distance, and the distance between the first region (D1) of the first electrode plate (51) and the separator (53) is a second distance, and the first distance is greater than the second distance.

13. The battery cell according to any one of claims 8 to 12, characterized in that, The first electrode plate (51) includes a first bending section (511), and the starting position of the concave portion (21) of the first electrode plate (51) is located within the first bending section (511).

14. A battery, characterized in that, The battery includes the battery cell (50) according to any one of claims 7 to 13.

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