Secondary battery and electronic device

Abstract

The secondary battery comprises an electrode assembly, the electrode assembly comprises a pole piece and a pole lug, and the pole piece comprises a current collector and an active layer arranged on at least one surface of the current collector. The pole piece further comprises a first pole piece edge and a second pole piece edge which are opposite in the first direction, and the tab is connected with the current collector and extends out of the electrode assembly from the first pole piece edge in the first direction. The active layer is provided with a plurality of first Tesla valve channels and a plurality of second Tesla valve channels, the area, provided with the first Tesla valve channels, of the active layer is a first area, the area, provided with the second Tesla valve channels, of the active layer is a second area, and the second area and the first area are arranged in the first direction. The forward flow direction of the first Tesla valve channels is the direction from the edge of the first pole piece to the edge of the second pole piece, the forward flow direction of the second Tesla valve channels is the direction from the edge of the second pole piece to the edge of the first pole piece, and the plurality of second Tesla valve channels are respectively communicated with the plurality of first Tesla valve channels.

Description

Technical Field

[0001] This application relates to the field of energy storage devices, and in particular, to a secondary battery and an electronic device including the secondary battery. Background Art

[0002] Lithium-ion batteries are widely used in electric vehicles and consumer electronic products due to their advantages such as high energy density, high output power, long cycle life, and low environmental pollution. During the charge-discharge cycle of a lithium-ion battery, the electrode plate expands and contracts repeatedly, and it is easy to have the problem of uneven electrolyte distribution, resulting in electrolyte enrichment in the edge area of the battery and poor electrolyte infiltration in the central area of the battery, causing lithium deposition and deterioration of the cycle performance. Summary of the Invention

[0003] An object of this application is to provide a secondary battery that can improve the problem of lithium deposition caused by uneven electrolyte distribution and improve the cycle performance.

[0004] This application provides a secondary battery, including an electrode assembly. The electrode assembly includes an electrode plate and an electrode tab. The electrode plate includes a current collector and an active layer provided on at least one surface of the current collector. The electrode plate further includes a first electrode plate edge and a second electrode plate edge opposite to each other in a first direction. The electrode tab is connected to the current collector and extends out of the electrode assembly from the first electrode plate edge in the first direction. The active layer is provided with a plurality of first Tesla valve channels and a plurality of second Tesla valve channels. The area on the active layer where a plurality of first Tesla valve channels are provided is a first area, and the area on the active layer where a plurality of second Tesla valve channels are provided is a second area. The second area and the first area are arranged in the first direction. The forward flow direction of the first Tesla valve channel is from the first electrode plate edge to the second electrode plate edge, and the forward flow direction of the second Tesla valve channel is from the second electrode plate edge to the first electrode plate edge. A plurality of second Tesla valve channels are respectively communicated with a plurality of first Tesla valve channels.

[0005] By providing the first Tesla valve channels and the second Tesla valve channels on the electrode plate in this application, the electrolyte located outside the edge of the electrode plate can flow into the central area of the electrode plate through the first Tesla valve channels and the second Tesla valve channels and can be stored in the central area, thereby improving the lithium deposition caused by electrolyte enrichment in the edge area of the electrode plate or poor infiltration in the central area of the electrode plate, and improving the cycle performance of the secondary battery.

[0006] In some possible implementation manners, the first Tesla valve channel and the second Tesla valve channel satisfy at least one of the following conditions: (1) the width of the first Tesla valve channel is D1, the depth of the first Tesla valve channel is D2, and 10% ≤ D2 / D1 ≤ 30%; (2) the distance between two adjacent first Tesla valve channels is D3, and 2 μm ≤ D3 ≤ 8 μm; (3) the width of the second Tesla valve channel is D4, the depth of the second Tesla valve channel is D5, and 10% ≤ D5 / D4 ≤ 30%; (4) the distance between two adjacent second Tesla valve channels is D6, and 2 μm ≤ D6 ≤ 8 μm. When the Tesla valve channels satisfy the above conditions, the width, depth, and / or quantity of the Tesla valve channels are within a suitable range, the effects of improving lithium plating and cycling performance are better, and the influence on the energy density is reduced.

[0007] In some possible implementation manners, the first Tesla valve channel and the second Tesla valve channel satisfy at least one of the following conditions: (1) 11% ≤ D2 / D1 ≤ 18%; (2) 4 μm ≤ D3 ≤ 6 μm; (3) 11% ≤ D5 / D4 ≤ 18%; (4) 4 μm ≤ D6 ≤ 6 μm. When the Tesla valve channels satisfy the above conditions, the effects of improving lithium plating and cycling performance are better, and a relatively high energy density can be further taken into account.

[0008] In some possible implementation manners, the electrode sheet is a negative electrode sheet. Along the first direction, the first region of the negative electrode sheet includes a first edge located on one side of the edge of the first electrode sheet, the second region of the negative electrode sheet includes a second edge located on one side of the edge of the second electrode sheet, the distance between the first edge and the edge of the first electrode sheet is L1, the distance between the second edge and the edge of the second electrode sheet is L2, 0 mm ≤ L1 ≤ 6 mm, and / or 0 mm ≤ L2 ≤ 6 mm. When L1 and / or L2 are within the above ranges, the entrances of the first Tesla valve channel and / or the second Tesla valve channel can be arranged in the edge region where the negative electrode sheet extends beyond the positive electrode sheet, or the entrance of the first Tesla valve channel can be close enough to the edge of the positive electrode sheet, so that the electrolyte enriched at the edge of the electrode assembly can smoothly flow into the first Tesla valve channel and / or the second Tesla valve channel, thereby improving the lithium plating and cycling performance.

[0009] In some possible implementation manners, 4 mm ≤ L1 ≤ 6 mm, and / or 4 mm ≤ L2 ≤ 6 mm. When L1 and / or L2 are within the above ranges, the effects of improving lithium plating and cycling performance are better, and the mass loss of the active layer can be reduced to improve the energy density.

[0010] In some possible implementations, the electrode tab is a positive electrode tab. Along the first direction, the first region of the positive electrode tab includes a third edge located on one side of the edge of the first electrode tab, and the second region of the positive electrode tab includes a fourth edge located on one side of the edge of the second electrode tab. The distance between the third edge and the edge of the first electrode tab is L3, and the distance between the fourth edge and the edge of the second electrode tab is L4, where 0 mm ≤ L3 ≤ 2 mm, and / or 0 mm ≤ L4 ≤ 2 mm. When L3 and / or L4 are within the above ranges, the inlets of the first Tesla valve channel and / or the second Tesla valve channel can be made close enough to the edge of the positive electrode tab, so that the electrolyte enriched at the edge of the electrode assembly can smoothly flow into the first Tesla valve channel and / or the second Tesla valve channel, thereby improving the cycling performance.

[0011] In some possible implementations, along the first direction, the width of the first region is W1, the width of the second region is W2, and the width of the electrode tab is W, where 0.4 ≤ W1 / W ≤ 0.6, or 0.4 ≤ W2 / W ≤ 0.6. When W1 / W or W2 / W is within the above ranges, it is beneficial for the first Tesla valve channel and / or the second Tesla valve channel to transport the electrolyte to the central region of the electrode tab in the first direction, improving the lithium plating caused by poor electrolyte infiltration in the central region of the electrode tab and enhancing the cycling performance.

[0012] In some possible implementations, along the second direction perpendicular to the first direction, the length of the first region is M1, the length of the second region is M2, and the length of the electrode tab is M, where 0.6 ≤ M1 / M ≤ 1, and / or 0.6 ≤ M2 / M ≤ 1. When M1 / M and / or M2 / M are within the above ranges, the distribution area of the first region and / or the second region on the electrode tab along the second direction is appropriate, and the effect of improving lithium plating and cycling performance is better.

[0013] In some possible implementations, 0.7 ≤ M1 / M ≤ 0.9, and / or 0.7 ≤ M2 / M ≤ 0.9. When M1 / M and / or M2 / M are within the above ranges, the effect of improving lithium plating and cycling performance is better, and a relatively high energy density can be achieved.

[0014] In some possible implementations, along the second direction perpendicular to the first direction, the active layer includes a first active layer edge. The minimum distance between the edge of the first region and the first active layer edge is M3, and the minimum distance between the edge of the second region and the first active layer edge is M4, where 15 mm ≤ M3 ≤ 30 mm, and / or 15 mm ≤ M4 ≤ 30 mm. When M3 and / or M4 are within the above ranges, the problem of powder shedding at the edge of the first active layer of the electrode tab can be improved, and the effect of improving lithium plating and cycling performance is better.

[0015] In some possible implementations, the first Tesla valve channel is directly connected to the second Tesla valve channel.

[0016] In some possible implementations, the active layer is provided with a plurality of grooves, the second Tesla valve channel, the grooves, and the first Tesla valve channel are arranged in sequence along the first direction, and the first Tesla valve channel is communicated with the second Tesla valve channel through the grooves.

[0017] The present application also provides an electronic device, including any one of the above secondary batteries. Description of the Drawings

[0018] The above and / or additional aspects and advantages of the present application will become apparent and easy to understand from the description of the embodiments in conjunction with the following drawings, in which:

[0019] Figure 1 is a schematic diagram of a secondary battery provided by an embodiment of the present application;

[0020] Figure 2 is a schematic diagram of a pole piece provided by an embodiment of the present application;

[0021] Figure 3 is Figure 2 an enlarged view of part A in

[0022] Figure 4 is a cross-sectional schematic diagram of a pole piece provided by an embodiment of the present application;

[0023] Figure 5 is a cross-sectional schematic diagram of a pole piece provided by another embodiment of the present application;

[0024] Figure 6 is a schematic diagram of a pole piece provided by another embodiment of the present application;

[0025] Figure 7 is a schematic diagram of a pole piece provided by yet another embodiment of the present application;

[0026] Figure 8 is a schematic diagram of an electronic device provided by an embodiment of the present application.

[0027] Description of the Main Element Symbols

[0028] Secondary battery 100

[0029] Shell 10

[0030] Electrode assembly 20

[0031] Electrode terminal 30

[0032] Pole piece 40

[0033] Current collector 41

[0034] Active layer 42

[0035] The edge of the first pole piece 40A

[0036] The edge of the second pole piece 40B

[0037] Tab 50

[0038] The first Tesla valve channel 43

[0039] The second Tesla valve channel 44

[0040] The first Tesla valve 430

[0041] The first straight flow channel 431

[0042] The first arc-shaped flow channel 432

[0043] The first converging flow channel 433

[0044] The first diverging flow channel 434

[0045] The second Tesla valve 440

[0046] The second straight flow channel 441

[0047] The second arc-shaped flow channel 442

[0048] The second converging flow channel 443

[0049] The second diverging flow channel 444

[0050] The edge of the first active layer 42A

[0051] The edge of the second active layer 42B

[0052] The first edge 43A

[0053] The second edge 44A

[0054] The third edge 43B

[0055] The fourth edge 44B

[0056] Groove 45

[0057] Electronic device 1 Detailed implementation manners

[0058] The technical solutions in the embodiments of the present application will be clearly and detailedly described below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application.

[0059] Hereinafter, embodiments of the present application will be described in detail. However, the present application can be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this application will be thorough and detailed and will convey to those skilled in the art.

[0060] In addition, for the sake of brevity and clarity, in the drawings, the sizes or thicknesses of various components and layers may be enlarged. Throughout the text, the same numerical values refer to the same elements. In addition, it should be understood that when element A is referred to as "connected" to element B, element A may be directly connected to element B, or there may be an intermediate element C and element A and element B may be indirectly connected to each other.

[0061] Furthermore, when describing the embodiments of the present application, "may" means "one or more embodiments of the present application".

[0062] The technical terms used herein are for the purpose of describing specific embodiments and are not intended to limit the present application. As used herein, the singular forms are also intended to include the plural forms unless the context clearly indicates otherwise. It should be understood that the term "comprising", when used in this specification, refers to the presence of the recited features, values, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, values, steps, operations, elements, components, and / or combinations thereof. It should be understood that although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part without departing from the teachings of the exemplary embodiments.

[0063] "A plurality of" in the present application means two or more.

[0064] Please refer to Figure 1 , an embodiment of the present application provides a secondary battery 100, including a housing 10, an electrode assembly 20 accommodated in the housing 10, an electrolyte (not shown in the figure), and electrode terminals 30. The electrode terminals 30 are electrically connected to the electrode assembly 20 and extend out of the housing 10 for connecting external components. In this embodiment, the number of the electrode terminals 30 is two, namely a positive electrode terminal and a negative electrode terminal, and the two electrode terminals 30 extend out of the housing 10 from the same side. In other embodiments, the number of the electrode terminals 30 may be greater than two, and the plurality of electrode terminals 30 may extend out of the housing 10 from different sides. In some embodiments, in order to achieve high-voltage output, the secondary battery 100 includes a plurality of electrode assemblies 20.

[0065] The housing 10 can be any housing known to be suitable for the secondary battery 100. For example, the housing 10 can be a packaging bag obtained by encapsulating with a packaging film, such as an aluminum-plastic film, a steel-plastic film, etc.; or, the housing 10 can be a metal housing, such as a steel shell, an aluminum shell, etc.

[0066] The electrode assembly 20 includes a plurality of electrode plates, a plurality of tabs, and a separator. The plurality of electrode plates include a positive electrode plate and a negative electrode plate. The separator is disposed between adjacent positive and negative electrode plates to reduce the risk of short circuit due to contact between the positive and negative electrode plates. The plurality of tabs are respectively connected to the plurality of electrode plates and are connected to the corresponding electrode terminals 30. The electrode assembly 20 can have a wound structure formed by winding a positive electrode plate, a separator, and a negative electrode plate after lamination. The electrode assembly 20 can also have a stacked structure formed by sequentially laminating a positive electrode plate, a separator, and a negative electrode plate.

[0067] Please refer to Figure 2 and Figure 4 , the electrode plate 40 includes a current collector 41 and an active layer 42. The active layer 42 can be disposed on one surface or both surfaces of the current collector 41 in its thickness direction. The electrode plate 40 includes a first electrode plate edge 40A and a second electrode plate edge 40B that are opposite to each other in the first direction X. The tab 50 is connected to the current collector 41, extends out of the electrode assembly from the first electrode plate edge 40A along the first direction X, and is connected to the electrode terminal 30. In some embodiments, the tab 50 directly serves as the electrode terminal 30 and extends out of the housing to be electrically connected to an external component. In some embodiments, the tab 50 is integrally provided with the current collector 41. In other embodiments, the tab 50 is welded to the current collector 41.

[0068] The active layer 42 is provided with a plurality of first Tesla valve channels 43 and a plurality of second Tesla valve channels 44. The first Tesla valve channels 43 and the second Tesla valve channels 44 are formed by removing a part of the active layer 42. The area on the active layer where there are a plurality of first Tesla valve channels 43 is the first area, and the edges of the outermost first Tesla valve channels 43 enclose to form the first area. The plurality of first Tesla valve channels 43 in the first area are arranged along a second direction Y perpendicular to the first direction X. The first area is arranged close to the edge 40A of the first electrode tab. The area on the active layer where there are a plurality of second Tesla valve channels 44 is the second area, and the edges of the outermost second Tesla valve channels 44 enclose to form the second area. The plurality of second Tesla valve channels 44 in the second area are arranged along the second direction Y. The second area is arranged close to the edge 40B of the second electrode tab. The second area and the first area are arranged along the first direction X, and the plurality of first Tesla valve channels 43 communicate with the plurality of second Tesla valve channels 44 respectively. The forward flow direction of the first Tesla valve channel 43 is from the edge 40A of the first electrode tab to the edge 40B of the second electrode tab, and the forward flow direction of the second Tesla valve channel 44 is from the edge 40B of the second electrode tab to the edge 40A of the first electrode tab. The electrolyte outside the edge 40A of the first electrode tab can easily flow into the central area of the electrode tab 40 in the first direction X through the first Tesla valve channel 43, and the electrolyte outside the edge 40B of the second electrode tab can easily flow into the central area of the electrode tab 40 through the second Tesla valve channel 44, and the electrolyte flowing into the central area of the electrode tab 40 will be stored in the Tesla valve channel and will not flow out of the edge of the electrode tab 40 through the Tesla valve channel, so that the electrolyte can be distributed approximately evenly in each area of the electrode tab 40, thereby improving the lithium deposition caused by the enrichment of the electrolyte in the edge area of the electrode tab 40 or the poor wetting of the central area of the electrode tab 40, and improving the cycle performance of the secondary battery 100. In this application, the edge area of the electrode tab 40 refers to the area on the electrode tab 40 close to the edge of the electrode tab 40, and the central area of the electrode tab 40 refers to the area on the electrode tab 40 close to the center line of the electrode tab 40.

[0069] In some embodiments, please refer to Figure 2 and Figure 3, the first Tesla valve channel 43 includes a plurality of first Tesla valves 430. Each first Tesla valve 430 includes a first straight flow channel 431, a first arc-shaped flow channel 432, a first converging flow channel 433, and a first diverging flow channel 434. The first straight flow channel 431 is arranged at an angle with the edge of the first electrode tab 40A. The first converging flow channel 433 is arranged at an acute angle with the first straight flow channel 431. One end of the first arc-shaped flow channel 432 communicates with the first straight flow channel 431 through the first converging flow channel 433, and the other end of the first arc-shaped flow channel 432 communicates with the first straight flow channel 431 through the first diverging flow channel 434. The first straight flow channels 431 of adjacent first Tesla valves 430 are connected. When the electrolyte flows forward in the direction from the edge of the first electrode tab 40A to the edge of the second electrode tab 40B, the electrolyte can bypass the resistance flow channel composed of the first arc-shaped flow channel 432, the first converging flow channel 433, and the first diverging flow channel 434, and directly flow unobstructed along the first straight flow channel 431 to the central region of the electrode tab 40. And under the action of the unique structure of the first Tesla valve 430, the electrolyte can obtain a certain acceleration, accelerating the liquid replenishment speed of the central region of the electrode tab 40. When the electrolyte flows backward in the direction from the edge of the second electrode tab 40B to the edge of the first electrode tab 40A, the electrolyte in the first straight flow channel 431 will be blocked by the resistance flow channel composed of the first arc-shaped flow channel 432, the first converging flow channel 433, and the first diverging flow channel 434. When the electrolyte enters through the first converging flow channel 433, it will be blocked by the first arc-shaped flow channel 432, resulting in that it is difficult for the electrolyte to flow backward outside the edge of the first electrode tab 40A, thus realizing unidirectional conduction. Among them, the more the number of the first Tesla valves 430, the greater the resistance generated by the first Tesla valve channel 43.

[0070] In some embodiments, please refer to Figure 2 and Figure 3, the second Tesla valve channel 44 includes a plurality of second Tesla valves 440. The second Tesla valve 440 includes a second straight flow channel 441, a second arc-shaped flow channel 442, a second converging flow channel 443, and a second diverging flow channel 444. The second straight flow channel 441 is arranged at an angle with the second pole piece edge 40B, and the second converging flow channel 443 is arranged at an acute angle with the second straight flow channel 441. One end of the second arc-shaped flow channel 442 is communicated with the second straight flow channel 441 through the second converging flow channel 443, and the other end of the second arc-shaped flow channel 442 is communicated with the second straight flow channel 441 through the second diverging flow channel 444. The second straight flow channels 441 of adjacent two second Tesla valves 440 are communicated. When the electrolyte flows forward in the direction from the second pole piece edge 40B to the first pole piece edge 40A, the electrolyte can bypass the resistance flow channel composed of the second arc-shaped flow channel 442, the second converging flow channel 443, and the second diverging flow channel 444, and directly flow unobstructedly along the second straight flow channel 441 to the central area of the pole piece 40. And under the action of the unique structure of the second Tesla valve 440, the electrolyte can obtain a certain acceleration, accelerating the liquid replenishment speed of the central area of the pole piece 40. When the electrolyte flows backward in the direction from the first pole piece edge 40A to the second pole piece edge 40B, the electrolyte in the second straight flow channel 441 will be blocked by the resistance flow channel composed of the second arc-shaped flow channel 442, the second converging flow channel 443, and the second diverging flow channel 444. When the electrolyte enters through the second converging flow channel 443, it will be blocked by the second arc-shaped flow channel 442, resulting in that it is difficult for the electrolyte to flow backward outside the second pole piece edge 40B, thereby realizing unidirectional conduction. Among them, the more the number of the second Tesla valves 440, the greater the resistance generated by the second Tesla valve channel 44.

[0071] Please refer to Figure 3 and Figure 4, the width of the first Tesla valve channel 43 is D1, and the depth of the first Tesla valve channel 43 is D2. In the present application, the width of the first Tesla valve channel 43 refers to the cross-sectional width of the first straight flow channel 431, and the cross-sectional widths of the first arc flow channel 432, the first converging flow channel 433, and the first diverging flow channel 434 are substantially the same as the cross-sectional width of the first straight flow channel 431. In some embodiments, 10% ≤ D2 / D1 ≤ 30%. For example, D2 / D1 can be 10%, 15%, 20%, 25%, 30%, or a range composed of any two of these values. When the energy density remains unchanged, that is, when the mass loss of the active layer removed to form the first Tesla valve channel 43 is certain, controlling D2 / D1 within the above range can make the width and depth of the first Tesla valve channel 43 within a suitable range, and the effect of improving lithium plating and cycling performance is better. When D2 / D1 < 10%, the depth of the first Tesla valve channel 43 is small, and when etching to form the first Tesla valve channel 43, it is easy to have a situation where the etching does not penetrate, resulting in the non-penetration of the channel, and the effect of improving the cycling performance is limited; when D2 / D1 > 30%, the depth of the first Tesla valve channel 43 is large, more active layer needs to be removed, which affects the energy density of the secondary battery, and it is easy to have excessive etching, requiring higher precision for processing equipment (such as lasers), increasing the cost.

[0072] In some embodiments, 11% ≤ D2 / D1 ≤ 18%. When D2 / D1 is within the above range, the effect of improving lithium plating and cycling performance is better, and the impact on the energy density of the secondary battery is smaller, and the channel is not prone to excessive etching.

[0073] Please refer to Figure 3 , in the second direction Y, the spacing between two adjacent first Tesla valve channels 43 is D3. The spacing between two adjacent first Tesla valve channels 43 refers to the spacing between two edges on the same side of two adjacent first straight flow channels 431 in the second direction Y. In some embodiments, 2μm ≤ D3 ≤ 8μm. For example, D3 can be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, or a range composed of any two of these values. When the area of the electrode sheet 40 is certain and the width of the channel is certain, when D3 is within the above range, the number of the first Tesla valve channels 43 is appropriate, and the effect of improving lithium plating and cycling performance is better. When D3 < 2μm, D3 is small, the number of channels is too large, causing design redundancy, having a greater impact on the energy density of the secondary battery, and requiring higher precision for processing equipment (such as lasers), increasing the cost; when D3 > 8μm, the number of channels is small, and the effect of improving lithium plating and cycling performance is limited.

[0074] In some embodiments, 4 μm ≤ D3 ≤ 6 μm. When D3 is within the above range, the effect of improving the cycle performance is better, and a relatively high energy density can be achieved at the same time.

[0075] Please refer to Figure 3 and Figure 5 , the width of the second Tesla valve channel 44 is D4, and the depth of the second Tesla valve channel 44 is D5. In this application, the width of the second Tesla valve channel 44 refers to the cross-sectional width of the second straight flow channel 441. The cross-sectional widths of the second arc-shaped flow channel 442, the second converging flow channel 443, and the second diverging flow channel 444 are substantially the same as the cross-sectional width of the second straight flow channel 441. In some embodiments, 10% ≤ D5 / D4 ≤ 30%. For example, D5 / D4 can be 10%, 15%, 20%, 25%, 30%, or any range composed of any two of these values. When the energy density remains unchanged, that is, when the mass loss of the active layer removed to form the second Tesla valve channel 44 is constant, controlling D5 / D4 within the above range can keep the width and depth of the second Tesla valve channel 44 within a suitable range, and the effect of improving the cycle performance is better. When D5 / D4 < 10%, the depth of the second Tesla valve channel 44 is relatively small, and it is easy to have a situation where the etching does not penetrate during the etching to form the second Tesla valve channel 44, resulting in an unpenetrated channel and limited improvement in the cycle performance. When D5 / D4 > 30%, the depth of the second Tesla valve channel 44 is relatively large, more active layer needs to be removed, which affects the energy density of the secondary battery, and it is easy to have excessive etching, requiring higher precision for processing equipment (such as lasers), increasing the cost.

[0076] In some embodiments, 11% ≤ D5 / D4 ≤ 18%. When D5 / D4 is within the above range, the effect of improving the cycle performance is better, and the impact on the energy density of the secondary battery is relatively small, and it is not easy to have excessive etching of the channel.

[0077] Please refer to Figure 3, in the second direction Y, the spacing between two adjacent second Tesla valve channels 44 is D 6. The spacing between two adjacent second Tesla valve channels 44 refers to the spacing between two edges of two adjacent second straight-through flow channels 441 located on the same side in the second direction Y. In some embodiments, 2μm≤D 6≤8μm. For example, D 6 can be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm or a range consisting of any two values ​​therein. When the area of ​​the pole piece 40 is constant and the width of the channel is constant, when D 6 is in the above range, the number of the second Tesla valve channels 44 is appropriate, and the effect of improving the cycle performance is better. When D 6<2μm, D 6 is small, the number of channels is too large, resulting in design redundancy, a greater impact on the energy density of the secondary battery, and a higher precision requirement for processing equipment (such as lasers), which increases costs; when D 6>8μm, the number of channels is small, and the effect of improving the cycle performance is limited.

[0078] In some embodiments, 4 μm ≤ D 6 ≤ 6 μm. When D 6 is within the above range, the effect of improving the cycle performance is better and a higher energy density can be taken into account.

[0079] See also Figure 2 , along the first direction X, the width of the first region is W1, and the width of the pole piece 40 is W. In some embodiments, 0.4≤W 1 / W≤0.6. For example, W 1 / W can be 0.4, 0.45, 0.5, 0.55, 0.6, or a range consisting of any two values ​​therein. When W1 / W is within the above range, it is beneficial for the first Tesla valve channel 43 to transfer the electrolyte to the central area of ​​the pole piece 40 in the first direction X, improve the lithium precipitation caused by poor electrolyte infiltration in the central area of ​​the pole piece 40, and improve the cycle performance.

[0080] See also Figure 2 , along the first direction X, the width of the second region is W2. In some embodiments, 0.4≤W2 / W≤0.6. For example, W2 / W can be 0.4, 0.45, 0.5, 0.55, 0.6 or a range consisting of any two values ​​therein. When W2 / W is within the above range, it is beneficial for the second Tesla valve channel 44 to transfer the electrolyte to the central area of ​​the pole piece 40 in the first direction X, improve the lithium precipitation caused by poor electrolyte infiltration in the central area of ​​the pole piece 40, and improve the cycle performance.

[0081] See also Figure 2 and Figure 4, along the second direction Y, the length of the first region is M1, and the length of the pole piece 40 is M. In some embodiments, 0.6 ≤ M1 / M ≤ 1. For example, M1 / M can be 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or a range composed of any two of these values. When the width of the channels is constant and the spacing between the channels is constant, when M1 / M is within the above range, the distribution area of the plurality of first Tesla valve channels 43 on the pole piece 40 along the second direction Y is appropriate, and the effect of improving lithium deposition and cycling performance is better.

[0082] In some embodiments, 0.7 ≤ M1 / M ≤ 0.9. When M1 / M is within the above range, the distribution area of the plurality of first Tesla valve channels 43 on the pole piece 40 along the second direction Y is larger, the effect of improving lithium deposition and cycling performance is better, and a relatively high energy density can be taken into account.

[0083] Please refer to Figure 2 and Figure 5 , along the second direction Y, the length of the second region is M2. In some embodiments, 0.6 ≤ M2 / M ≤ 1. For example, M2 / M can be 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or a range composed of any two of these values. When the width of the channels is constant and the spacing between the channels is constant, when M2 / M is within the above range, the distribution area of the plurality of second Tesla valve channels 44 on the pole piece 40 along the second direction Y is appropriate, and the effect of improving lithium deposition is better.

[0084] In some embodiments, 0.7 ≤ M2 / M ≤ 0.9. When M2 / M is within the above range, the distribution area of the plurality of second Tesla valve channels 44 on the pole piece 40 along the second direction Y is larger, and the effect of improving lithium deposition is better.

[0085] Please refer to Figure 2 , Figure 4 and Figure 5, the active layer 42 includes a first active layer edge 42A located on one side of the second direction Y. The minimum distance between the edge of the first region and the first active layer edge 42A is M3, and the minimum distance between the edge of the second region and the second active layer edge 42B is M4. In this application, the minimum distance between the first region and the first active layer edge 42A refers to the distance between the edge of the first region on the same side of the first active layer edge 42A in the second direction Y and the first active layer edge 42A. The minimum distance between the second region and the first active layer edge 42A refers to the distance between the edge of the second region on the same side of the first active layer edge 42A in the second direction Y and the first active layer edge 42A. In some embodiments, 15 mm ≤ M3 ≤ 30 mm, and / or, 15 mm ≤ M4 ≤ 30 mm. When M3 and / or M4 are within the above ranges, the problem of powder falling off at the first active layer edge 42A of the electrode sheet 40 can be improved, and the effects of improving lithium deposition and cycle performance are better.

[0086] Please refer to Figure 2 , Figure 4 and Figure 5 , along the second direction Y, the active layer 42 includes a second active layer edge 42B opposite to the first active layer edge 42A. The minimum distance between the first region and the second active layer edge 42B is M5, and the minimum distance between the second region and the second active layer edge 42B is M6. In this application, the minimum distance between the first region and the second active layer edge 42B refers to the distance between the edge of the first region closest to the second active layer edge 42B in the second direction Y and the second active layer edge 42B. The minimum distance between the second region and the second active layer edge 42B refers to the distance between the edge of the second region closest to the second active layer edge 42B in the second direction Y and the second active layer edge 42B. In some embodiments, 15 mm ≤ M5 ≤ 30 mm, and / or, 15 mm ≤ M6 ≤ 30 mm. When M5 and / or M6 are within the above ranges, the problem of powder falling off at the second active layer edge 42B of the electrode sheet 40 can be improved, and the effects of improving lithium deposition and cycle performance are better.

[0087] In some embodiments, the electrode sheet 40 is a negative electrode sheet. The current collector 41 may include at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Al, and their combinations. The active layer 42 includes a negative active material, and the negative active material may be selected from at least one of graphite-based materials and silicon materials. The graphite-based materials may be selected from at least one of artificial graphite and natural graphite; the silicon materials may be selected from at least one of silicon carbide compounds, silicon oxides, silicon carbides, and silicon.

[0088] Please refer to Figure 6, when the electrode sheet 40 is a negative electrode sheet, the first region includes a first edge 43A on one side of the first electrode sheet edge 40A, and the second region includes a second edge 44A on one side of the second electrode sheet edge 40B. Along the first direction X, the distance between the first edge 43A and the first electrode sheet edge 40A of the negative electrode sheet is L1, and the distance between the second edge 44A and the second electrode sheet edge 40B of the negative electrode sheet is L2. In some embodiments, 0 mm ≤ L1 ≤ 6 mm, and / or, 0 mm ≤ L2 ≤ 6 mm. To reduce the risk of lithium deposition at the edge of the negative electrode sheet, it is usually configured that the edge of the negative electrode sheet extends beyond the edge of the positive electrode sheet. When L1 and / or L2 are within the above range, the inlet of the first Tesla valve channel 43 and / or the second Tesla valve channel 44 can be arranged within the region where the negative electrode sheet extends beyond the positive electrode sheet, or the inlet of the first Tesla valve channel 43 is close enough to the edge of the positive electrode sheet, so that the electrolyte enriched at the edge of the electrode assembly can smoothly flow into the first Tesla valve channel 43 and / or the second Tesla valve channel 44, thereby improving the lithium deposition and cycle performance.

[0089] In some embodiments, 4 mm ≤ L1 ≤ 6 mm, and / or, 4 mm ≤ L2 ≤ 6 mm. When L1 and / or L2 are within the above range, the electrolyte enriched at the edge of the electrode assembly can smoothly flow into the first Tesla valve channel 43 and / or the second Tesla valve channel 44 to improve the lithium deposition and cycle performance, and the mass loss of the active layer can be reduced to improve the energy density.

[0090] In some embodiments, the electrode sheet 40 is a positive electrode sheet. The current collector 41 may include at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Al, and their combinations. The active layer 42 includes a positive electrode active material, and the positive electrode active material may include at least one of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminate, and their combinations.

[0091] Referring to FIG. 5, when the electrode sheet 40 is a positive electrode sheet, the first region includes a third edge 43B located on one side of the first edge 40A of the first electrode sheet, and the second region includes a fourth edge 44B located on one side of the second edge 40B of the second electrode sheet. Along the first direction X, the distance between the third edge 43B and the first edge 40A of the negative electrode sheet is L3, and the distance between the fourth edge 44B and the second edge 40B of the negative electrode sheet is L4. In some embodiments, 0 mm ≤ L3 ≤ 2 mm, and / or, 0 mm ≤ L4 ≤ 2 mm. When L3 and / or L4 are within the above ranges, the inlets of the first Tesla valve channel 43 and / or the second Tesla valve channel 44 can be made close enough to the edge of the positive electrode sheet, so that the electrolyte enriched at the edge of the electrode assembly can smoothly flow into the first Tesla valve channel 43 and / or the second Tesla valve channel 44, thereby improving the cycle performance.

[0092] In some embodiments, referring to Figure 2 and Figure 6 , each first Tesla valve channel 43 communicates directly with the corresponding second Tesla valve channel 44. With such an arrangement, the electrolyte flowing into the electrode sheet 40 through the first Tesla valve channel 43 and the second Tesla valve channel 44 can be stored in the central region of the electrode sheet 40.

[0093] In some embodiments, referring to Figure 7 , the active layer 42 is further provided with a plurality of grooves 45. The second Tesla valve channels 44, the grooves 45, and the first Tesla valve channels 43 are arranged along the first direction X, and each first Tesla valve channel 43 communicates with the corresponding second Tesla valve channel 44 through the corresponding groove 45. The grooves 45 can be strip-shaped, circular, wavy, etc., and the present application does not make any restrictions. In some embodiments, the center line of the electrode sheet 40 passes through the grooves 45.

[0094] Referring to Figure 8 , an embodiment of the present application further provides an electronic device 1. The electronic device 1 includes the secondary battery 100 as described above. The electronic device 1 of the present application can be, but is not limited to, a laptop computer, a pen input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal TV, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a moped, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flash, a camera, a large household battery, and a lithium-ion capacitor, etc.

[0095] The present application will be described in detail below through specific examples and comparative examples. Among them, taking a pouch cell as an example of a secondary battery and combining with a specific preparation process and testing method to describe the present application. Those skilled in the art should understand that the preparation methods described in the present application are only examples, and any other suitable preparation methods are within the scope of the present application.

[0096] Example 1

[0097] Preparation of the positive electrode sheet: The positive electrode active material (lithium cobaltate), conductive agent (conductive carbon black), and binder (polyvinylidene fluoride) were dissolved in an N-methylpyrrolidone solution in a weight ratio of 97.5:1:1.5 to form a positive electrode slurry with a solid content of 75%. Aluminum foil was used as the current collector, and the positive electrode slurry was coated on the surface of the positive electrode current collector to obtain a positive electrode active layer, and the thickness of the single-sided positive electrode active layer was 50 μm. Subsequently, it was cold-pressed and cut to obtain a positive electrode sheet. Then, a laser etching process was used to etch multiple first Tesla valve channels and multiple second Tesla valve channels on the positive electrode active layer of the positive electrode sheet. The structure of the positive electrode sheet is as Figure 2 shown.

[0098] Preparation of the negative electrode sheet: The negative electrode active material (graphite), conductive agent (conductive carbon black), thickening agent (sodium carboxymethyl cellulose), and binder (styrene-butadiene rubber) were mixed in a mass ratio of 97.5:1:0.5:1, and then deionized water was added as a solvent and stirred evenly to obtain a negative electrode slurry with a solid content of 50 wt%. Copper foil was used as the current collector, and the negative electrode slurry was coated on the surface of the negative electrode current collector to obtain a negative electrode active layer, and the thickness of the single-sided negative electrode active layer was 75 μm. Subsequently, it was cold-pressed and cut to obtain a negative electrode sheet. Then, a laser etching process was used to etch multiple first Tesla valve channels and multiple second Tesla valve channels on the negative electrode active layer of the negative electrode sheet. The structure of the negative electrode sheet is as Figure 2 shown.

[0099] Preparation of the separator: A polyethylene film was selected as the separator.

[0100] Preparation of the electrolyte: Ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and vinylene carbonate (VC) were mixed in a weight ratio of 20:30:20:28:2 to obtain an organic solvent, and then the fully dried lithium salt LiPF6 and the organic solvent were mixed in a weight ratio of 8:92 to obtain the electrolyte.

[0101] Preparation of lithium-ion battery: Stack the positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to obtain an electrode assembly; Place the electrode assembly in an aluminum-plastic film packaging bag and perform hot-pressing bonding under a preset pressure, and obtain a lithium-ion battery after liquid injection and formation. The length, width, and thickness of the battery are 19.255 mm, 11.9 mm, and 3.94 mm respectively, D1 = D4, D2 = D5, D3 = D6, L1 = L2, L3 = L4, M1 = M2, M3 = M4.

[0102] Examples 2 - 17

[0103] The difference from Example 1 is that at least one of D1, D2, and D3 is different.

[0104] Comparative Example 1

[0105] The difference from Example 1 is that both the positive electrode sheet and the negative electrode sheet are provided with Tesla valve channels.

[0106] The following describes the test methods for each parameter of this application.

[0107] (1) Testing of length, width, and depth:

[0108] Use a CCD (Charge Coupled Device) device to scan the cross-section of the electrode sheet and measure the corresponding length, width, and depth.

[0109] (2) Testing of cycle capacity retention rate:

[0110] At 25°C, charge the lithium-ion battery according to the following charging steps:

[0111] 1) Constant current at 1.65C until 4.10V, then constant voltage until cutoff at 1.55C;

[0112] 2) Constant current at 1.55C until 4.20V, then constant voltage until cutoff at 1.4C;

[0113] 3) Constant current at 1.4C until 4.24V, then constant voltage until cutoff at 1.1C;

[0114] 4) Constant current at 1.1C until 4.27V, then constant voltage until cutoff at 0.7C;

[0115] 5) Constant current at 0.7C until 4.30V, then constant voltage until cutoff at 0.4C;

[0116] 6) Constant current at 0.4C until 4.5V, then constant voltage until cutoff at C / 40.

[0117] The above charge-discharge process is one cycle. Record the discharge capacity after the first cycle as the initial discharge capacity. Repeat the above charge-discharge process 1000 times, and record the discharge capacity after 1000 cycles as the discharge capacity after cycling. Capacity retention rate = (discharge capacity after cycling / initial discharge capacity) × 100%.

[0118] (3) Lithium plating test:

[0119] After completing 1000 cycles according to the above charge-discharge process, disassemble the battery to obtain the negative electrode sheet and observe the lithium plating situation of the negative electrode sheet. If no white lithium metal is precipitated, it is recorded as "no lithium plating"; if white lithium metal is precipitated and the proportion of the lithium plating area is greater than 0 and less than 5%, it is recorded as "mild lithium plating"; if white lithium metal is precipitated and the proportion of the lithium plating area is greater than or equal to 5% and less than or equal to 10%, it is recorded as "moderate lithium plating"; if white lithium metal is precipitated and the proportion of the lithium plating area is greater than 10%, it is recorded as "severe lithium plating". Among them, the proportion of the lithium plating area is the percentage of the lithium plating area in the surface area of the negative electrode sheet.

[0120] (4) Volume energy density test:

[0121] 1) Under the environmental condition of 25°C, let the secondary battery stand for 10 min, charge it at a constant current of 0.2C to 4.5V, then charge it at a constant voltage until the current is 0.02C, and let it stand for 5 min; then discharge it at a constant current of 0.2C to 3V and let it stand for 5 min, and record the discharge capacity C0;

[0122] 2) Measure the length, width and thickness of the secondary battery with a PPG (Parallel Plate Gauge);

[0123] 3) Calculate through the following formula: Volume energy density = plateau voltage × C0 / (length × width × thickness).

[0124] (5) Conduct Hi-pot test on the lithium-ion battery and calculate the test passing rate.

[0125] Hi-pot test (High Potential test) is also called high voltage insulation test, which is an insulation resistance test used to judge whether there is a short circuit in the electrode assembly.

[0126] The test method is as follows: Detect the leakage current generated by the secondary battery prepared in the example or comparative example under the test voltage of 100V output by the high-pressure machine, and then calculate the resistance value = test voltage / leakage current. Compare the calculated resistance value with the set determination resistance. In this application, the preset value of the determination resistance is 5mΩ. If the detected resistance value is greater than or equal to the preset value of 5mΩ, it is determined that the tested product passes the test (OK); if the detected resistance value is less than the preset value of 5mΩ, the test voltage is instantaneously cut off and the tested product is determined to fail the test (NG). For each group of examples or comparative examples, 100 secondary batteries are tested. The number of lithium-ion batteries passing the test is X1, and the test pass rate is X1 / 100×100%, which is also the Hi-pot excellent rate.

[0127] Table 1

[0128]

[0129]

[0130] According to the experimental data of the comparative examples and examples in Table 1, it can be seen that by applying the solution of setting the first Tesla valve channel and the second Tesla valve channel on the active layer in the present invention, the cycle capacity retention rate of the secondary battery has increased. This is because the first Tesla valve channel and the second Tesla valve channel are set and interconnected, which can guide the electrolyte at the edge of the electrode sheet to concentrate towards the middle of the electrode sheet, reducing the lithium deposition problem caused by the lack of electrolyte in the middle area of the electrode sheet, and thus improving the cycle capacity retention rate of the secondary battery.

[0131] According to the experimental data of Examples 1 to 9, it can be seen that when D1 is constant, as D2 deepens, that is, as D2 / D1 increases, the degree of lithium deposition on the negative electrode sheet decreases and the cycle capacity retention rate increases. This is because as the depths of the first Tesla valve channel and the second Tesla valve channel increase, it is more conducive to the electrolyte transmission and liquid retention in the middle of the electrode sheet, thereby reducing the lithium deposition caused by the lack of electrolyte in the middle of the negative electrode sheet, and thus increasing the cycle capacity retention rate of the secondary battery; but at the same time, as D2 increases, more parts of the active layer are removed, resulting in a loss of volume energy density. To balance the relatively high cycle capacity retention rate, relatively low degree of lithium deposition on the negative electrode sheet, and relatively high volume energy density of the secondary battery, 10%≤D2 / D1≤30% is selected. Further, 11%≤D2 / D1≤18% is preferably selected.

[0132] According to the experimental data of Example 1, Examples 10 to 17, when D3 < 2 μm, the number of channels is too large, resulting in design redundancy, which has a greater impact on the energy density of the secondary battery. Moreover, because too much active layer is etched, the risk of active layer shedding increases, resulting in an increased risk of internal short circuit and a lower passing rate of the Hi-pot test; when D3 > 8 μm, the number of channels is small, and the improvement effect on lithium plating and cycle performance is limited. The degree of lithium plating on the negative electrode sheet deteriorates, and the cycle capacity retention rate of the secondary battery also decreases accordingly. To balance a high cycle capacity retention rate, a low degree of lithium plating on the negative electrode sheet, a high volumetric energy density, and a high passing rate of the Hi-pot test, 2 μm ≤ D3 ≤ 8 μm is selected. Further, 4 μm ≤ D3 ≤ 6 μm is preferably selected.

[0133] Examples 18 - 23

[0134] The difference from Example 1 is that at least one of W1 and W2 is different.

[0135] Table 2

[0136]

[0137] According to the experimental data of Example 1, Examples 18 to 23, it can be seen that when W1 / W is closer to 0.5, that is, when W2 / W is closer to 0.5, the cycle capacity retention rate is higher. This is because when W1 / W is closer to 0.5, that is, when W2 / W is closer to 0.5, the first Tesla valve channel and the second Tesla valve channel have a better effect of draining the electrolyte at the edge of the electrode sheet to the middle area of the electrode sheet, and have a better effect on solving the problem of lack of electrolyte in the middle area of the electrode sheet, so a higher cycle capacity retention rate can be obtained. Based on the above considerations, 0.4 ≤ W1 / W ≤ 0.6, or 0.4 ≤ W2 / W ≤ 0.6 is selected.

[0138] Table 3

[0139]

[0140]

[0141] According to the experimental data of Example 1, Examples 24 to 32, it can be seen that when M1 / M < 0.6, the proportion of the lengths of the first region and the second region in the length direction of the electrode sheet is relatively small, and the improvement effect on lithium plating and cycle performance is limited. Therefore, 0.6 ≤ M1 / M ≤ 1 is selected. When M1 / M = 1, the degree of lithium plating is low and the cycle capacity retention rate is relatively high, but because more active layer is lost due to etching, the volumetric energy density of the secondary battery is low. To balance a low degree of lithium plating on the negative electrode sheet, a high cycle capacity retention rate, and a high volumetric energy density, 0.7 ≤ M1 / M ≤ 0.9 is preferably selected.

[0142] Examples 33 - 44

[0143] It is different from Example 1 in that at least one of L1, L3, and M3 is different.

[0144] Table 4

[0145]

[0146]

[0147] According to the experimental data of Example 1, Examples 33 to 37, it can be seen that as L1 increases, the degree of lithium deposition on the negative electrode deteriorates and the cycle capacity retention rate decreases. However, because the active layer lost due to etching decreases, the volume energy density increases to some extent. In order to balance a lower degree of lithium deposition on the negative electrode, a higher cycle capacity retention rate, and a higher volume energy density, 0 mm ≤ L1 ≤ 6 mm is selected. Further, 4 mm ≤ L1 ≤ 6 mm is preferably selected.

[0148] According to the experimental data of Example 1, Examples 38 to 40, it can be seen that as L3 increases, the degree of lithium deposition on the negative electrode deteriorates and the cycle capacity retention rate decreases. However, because the active layer lost due to etching decreases, the volume energy density increases to some extent. In order to balance a lower degree of lithium deposition on the negative electrode, a higher cycle capacity retention rate, and a higher volume energy density, 0 mm ≤ L3 ≤ 2 mm is selected.

[0149] According to the experimental data of Example 1, Examples 41 to 44, it can be seen that as M3 increases, the degree of lithium deposition on the negative electrode deteriorates and the cycle capacity retention rate decreases. However, because the edges of the first region and the second region in the second direction are far from the edge of the active layer, the risk of shedding of the active material at the edge of the active layer due to etching is reduced, and the passing rate of the Hi-pot test increases to some extent. In order to balance a lower degree of lithium deposition on the negative electrode, a higher cycle capacity retention rate, and a higher passing rate of the Hi-pot test, 15 mm ≤ M3 ≤ 30 mm is selected.

[0150] Examples 45 - 47

[0151] It is different from Example 1 in that for the electrode plate provided with channels (the first Tesla valve channel and the second Tesla valve channel), whether a groove is provided or not.

[0152] Table 5

[0153]

[0154] Note: " / " represents that there is no such data item.

[0155] According to the experimental data of Comparative Example 1, Example 1, Example 45 and Example 46, setting the first Tesla valve channel and the second Tesla valve channel on either the positive electrode or the negative electrode can improve both the lithium plating and the cycling performance. Setting the first Tesla valve channel and the second Tesla valve channel on both the positive electrode and the negative electrode simultaneously can enable the secondary battery to obtain a better cycling capacity retention rate. However, it can also be seen that setting the first Tesla valve channel and the second Tesla valve channel on both the positive electrode and the negative electrode simultaneously results in a decrease in the volume energy density and the Hi-pot test passing rate of the secondary battery compared to setting the first Tesla valve channel and the second Tesla valve channel on either the positive electrode or the negative electrode.

[0156] According to the experimental data of Comparative Example 1, Example 1 and Example 47, when the first Tesla valve channel and the second Tesla valve channel are not directly connected but are connected by a groove, the degree of lithium plating on the negative electrode can also be reduced and the cycling performance of the secondary battery can be improved.

[0157] The above disclosure is only the preferred embodiment of the present application, and of course it cannot be used to limit the present application. Therefore, the equivalent changes made according to the present application still fall within the scope covered by the present application.

Claims

1. A secondary battery, comprising an electrode assembly, the electrode assembly comprising a pole piece and a pole ear, the pole piece comprising a current collector and an active layer disposed on at least one surface of the current collector, the pole piece further comprising a first pole piece edge and a second pole piece edge opposite to each other along a first direction, the pole ear being connected to the current collector and extending from the first pole piece edge along the first direction out of the electrode assembly, characterized in that: The active layer is provided with a plurality of first Tesla valve channels and a plurality of second Tesla valve channels; The area on the active layer where the plurality of the first Tesla valve channels are arranged is a first area, and the area on the active layer where the plurality of the second Tesla valve channels are arranged is a second area, and the second area and the first area are arranged along the first direction; The forward flow direction of the first Tesla valve channel is from the edge of the first pole piece to the edge of the second pole piece, and the forward flow direction of the second Tesla valve channel is from the edge of the second pole piece to the edge of the first pole piece. Multiple second Tesla valve channels are respectively connected to multiple first Tesla valve channels.

2. The secondary battery according to claim 1, wherein: The first Tesla valve channel and the second Tesla valve channel satisfy at least one of the following conditions: (1) The width of the first Tesla valve channel is D1, the depth of the first Tesla valve channel is D2, 10%≤D2 / D1≤30%; (2) The distance between two adjacent first Tesla valve channels is D 3, 2 μm ≤ D 3 ≤ 8 μm; (3) The width of the second Tesla valve channel is D4, the depth of the second Tesla valve channel is D5, 10%≤D5 / D4≤30%; (4) The distance between two adjacent second Tesla valve channels is D 6, 2 μm ≤ D 6 ≤ 8 μm.

3. The secondary battery according to claim 2, characterized in that: The first Tesla valve channel and the second Tesla valve channel satisfy at least one of the following conditions: (1) 11%≤D2 / D1≤18%; (2) 4μm≤D 3≤6μm; (3) 11%≤D5 / D4≤18%; (4) 4μm≤D 6≤6μm.

4. The secondary battery according to claim 1, wherein: The pole piece is a negative pole piece. Along the first direction, the first region of the negative pole piece includes a first edge located on one side of the edge of the first pole piece, the second region of the negative pole piece includes a second edge located on one side of the edge of the second pole piece, the distance between the first edge and the edge of the first pole piece is L1, the distance between the second edge and the edge of the second pole piece is L2, 0mm≤L1≤6mm, and / or, 0mm≤L2≤6mm.

5. The secondary battery according to claim 4, characterized in that: 4mm≤L1≤6mm, and / or, 4mm≤L2≤6mm.

6. The secondary battery according to claim 1, wherein: The pole piece is a positive pole piece. Along the first direction, the first area of ​​the positive pole piece includes a third edge located on one side of the edge of the first pole piece, and the second area of ​​the positive pole piece includes a fourth edge located on one side of the edge of the second pole piece. The distance between the third edge and the edge of the first pole piece is L3, and the distance between the fourth edge and the edge of the second pole piece is L4, 0mm≤L3≤2mm, and / or, 0mm≤L4≤2mm.

7. The secondary battery according to claim 1, wherein: Along the first direction, the width of the first region is W1, the width of the second region is W2, the width of the pole piece is W, 0.4≤W1 / W≤0.6, or 0.4≤W2 / W≤0.

6.

8. The secondary battery according to claim 1, wherein: Along a second direction perpendicular to the first direction, the length of the first region is M1, the length of the second region is M2, the length of the pole piece is M, 0.6≤M1 / M≤1, and / or, 0.6≤M2 / M≤1.

9. The secondary battery according to claim 8, characterized in that 0.7≤M1 / M≤0.9, and / or, 0.7≤M2 / M≤0.

9.

10. The secondary battery according to claim 1, wherein: Along a second direction perpendicular to the first direction, the active layer includes a first active layer edge, a minimum distance between an edge of the first region and the edge of the first active layer is M3, a minimum distance between an edge of the second region and the edge of the first active layer is M4, 15 mm ≤ M3 ≤ 30 mm, and / or 15 mm ≤ M4 ≤ 30 mm.

11. The secondary battery according to claim 1, wherein The first Tesla valve channel is directly connected to the second Tesla valve channel.

12. The secondary battery according to claim 1, wherein: The active layer is provided with a plurality of grooves, the second Tesla valve channel, the grooves and the first Tesla valve channel are arranged in sequence along the first direction, and the first Tesla valve channel is connected with the second Tesla valve channel through the grooves.

13. An electronic device, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 12.

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