Secondary battery, battery pack, and electronic device
By incorporating large pore areas and an insulating layer design in the electrode, the manufacturing process of the electrode has been optimized, solving the problems in pore configuration and rolling processes of existing secondary batteries, and improving the applicability and efficiency of the electrode.
Patent Information
- Application Number
- CN202422600013.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-25
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2034-10-25
AI Technical Summary
There is room for improvement in the electrode manufacturing process of existing secondary batteries, especially in terms of electrode pore configuration and rolling process.
An electrode structure is designed in which the pore size of the first region is larger than that of the second region, and an insulating layer is set during the electrode manufacturing process to cover the end of the active material layer, which is suitable for electrode manufacturing processes.
By optimizing the pore configuration and insulation layer design, the applicability of the electrode sheet was improved, the loss of the active material layer during the rolling process was reduced, and the manufacturing efficiency and performance of the electrode sheet were enhanced.
Smart Images
Figure CN223501882U_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a secondary battery, a battery pack, and an electronic device. Background Technology
[0002] In the field of new energy power batteries, common power batteries include pouch batteries, prismatic batteries, and cylindrical batteries. Cylindrical batteries refer to cylindrical wound batteries, which include a casing and electrode assemblies encapsulated within the casing. The electrode assemblies include wound first and second electrodes, with a separator located between the first and second electrodes to isolate them. However, existing secondary batteries still require further improvement in certain aspects. Summary of the Invention
[0003] In view of the problems existing in the related technologies, the purpose of the present invention is to provide a secondary battery, a battery pack and an electronic device, so as to provide at least one electrode that is more suitable for electrode manufacturing process.
[0004] To achieve the above objectives, embodiments of this application provide a secondary battery comprising: an electrode assembly, the electrode assembly including a first electrode, a second electrode, and a separator disposed between the first electrode and the second electrode; the first electrode including a first current collector and a first active material layer; the first current collector having a first surface and a second surface opposite to each other in its thickness direction; portions of the first surface and the second surface of the first current collector being covered by the first active material layer; the first active material layer on the first surface including a first flat region and a first thinned region; the direction from the first flat region to the first thinned region being the width direction of the first electrode; in the width direction, the first thinned region having a first end, and the first active material layer on the second surface having a second end; the first end extending beyond the second end in the width direction; the first active material layer on the first surface including a first region extending beyond the second end in the width direction and a second region not extending beyond the second end in the width direction; the pore size of the first region being larger than the pore size of the second region.
[0005] In some embodiments, the first active material layer on the second surface includes a first flat region and a first thinned region in sequence, and the second end is the end of the first thinned region of the first active material layer on the second surface.
[0006] In some embodiments, the secondary battery further includes: an insulating layer covering a first end and a second end, and extending to a first surface and a second surface not covered by the first active material layer. In the width direction of the first electrode, the insulating layer on the first surface has a first end, and the insulating layer on the second surface has a second end, wherein the first end of the insulating layer on the first surface extends beyond the second end of the insulating layer on the second surface in the width direction.
[0007] In some embodiments, the porosity of the first region is larger than that of the insulating layer.
[0008] In some embodiments, the second region includes a portion of the first thinning region that does not extend beyond the second end in the width direction, and a first straight region, wherein the pores of the portion of the first thinning region are smaller than the pores of the first region and larger than the pores of the first straight region.
[0009] In some embodiments, the second electrode includes a second current collector and a second active material layer. The second current collector has a first surface and a second surface opposite to each other in its thickness direction. A portion of the surface of the first surface and the second surface of the second current collector is covered by the second active material layer. The second active material layer on the first surface and the second surface respectively includes a second flat region and a second thinned region in the width direction. In the width direction, the second flat region on the first surface of the second current collector has a first end and the second flat region on the second surface of the second current collector has a second end. The second end of the second flat region extends beyond the first end of the second flat region in the width direction. Furthermore, the first end of the second flat region extends beyond the first end of the first thinned region of the first active material layer in the width direction.
[0010] In some embodiments, the second electrode includes a second current collector and a second active material layer. The second current collector has a first surface and a second surface opposite to each other in its thickness direction. A portion of the surface of the first surface and the second surface of the second current collector is covered by the second active material layer. In the opposite direction of the width direction, the second active material layer on the first surface and the second surface respectively includes a second flat region and a second thinned region. In the width direction, the second flat region on the first surface of the second current collector has a first end and the second flat region on the second surface of the second current collector has a second end. The first end and the second end of the second flat region are flush and extend beyond the first end of the first thinned region of the first active material layer in the width direction.
[0011] In some embodiments, the first electrode is a positive electrode.
[0012] Embodiments of this application also provide a battery pack, including any of the above-described secondary batteries.
[0013] Embodiments of this application also provide an electronic device including the battery pack described above.
[0014] The beneficial technical effects of this invention are as follows:
[0015] The technical solution of this application configures the porosity of the first region of the first electrode sheet to be larger than that of the second region, providing a first electrode sheet suitable for electrode sheet manufacturing processes. This is because, during electrode sheet manufacturing, when the first active material layer is coated, a first thinning region and a first flat region are formed, and during the rolling process of the coated first active material layer, the active material layer in the first region may not be pressed down. This application, by setting the first region to have larger porosity, allows for a lower weight and fewer particles per unit volume in the active material layer within the first region, making it more suitable for rolling processes. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 A schematic diagram is shown when the electronic device according to an embodiment of this application is a vehicle.
[0018] Figure 2 A perspective view of a secondary battery according to an embodiment of this application is shown.
[0019] Figure 3 A cross-sectional view of a secondary battery according to an embodiment of this application is shown.
[0020] Figure 4 This is a cross-sectional view of the first electrode of a secondary battery according to an embodiment of this application.
[0021] Figure 5A This is a schematic diagram of the first active material layer of the first electrode.
[0022] Figure 5B and Figure 5C These are SEM (scanning electron microscope) images and schematic diagrams showing the porosity changes in different regions of the first active material layer.
[0023] Figure 6 Example porosity of different regions of the first active material layer is shown.
[0024] Figure 7 This is a cross-sectional view of the first electrode of a secondary battery according to another embodiment of this application.
[0025] Figure 8 This is a cross-sectional view of the first and second electrodes of a secondary battery according to another embodiment of this application.
[0026] Figure 9 This is a cross-sectional view of the first and second electrodes of a secondary battery according to another embodiment of this application. Detailed Implementation
[0027] To better understand the spirit of the embodiments of this application, the following description is based on some preferred embodiments of this application.
[0028] Embodiments of this application will be described in detail below. Throughout this specification, identical or similar components and components having identical or similar functions are indicated by similar reference numerals. The embodiments described herein with reference to the accompanying drawings are illustrative and diagrammatic in nature and are intended to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.
[0029] As used herein, the terms “approximately,” “generally,” “substantially,” and “about” are used to describe and indicate minor variations. When used in conjunction with an event or situation, these terms may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately.
[0030] In this specification, unless otherwise specified or limited, relative terms such as “central,” “longitudinal,” “lateral,” “front,” “rear,” “right,” “left,” “inner,” “outer,” “lower,” “higher,” “horizontal,” “vertical,” “above,” “below,” “above,” “below,” “top,” “bottom,” and their derivatives (e.g., “horizontally,” “downward,” “upward,” etc.) should be interpreted as referring to the directions described in the discussion or depicted in the accompanying drawings. These relative terms are used for descriptive convenience only and do not require that this application be constructed or operated in a particular orientation.
[0031] For ease of description, "first," "second," "third," etc., can be used in this article to distinguish different components of a figure or a series of figures. "First," "second," "third," etc., are not intended to describe the corresponding components.
[0032] For ease of explanation, the following embodiments use a vehicle as an example of an electronic device. Figure 1 A schematic diagram is shown when the electronic device according to an embodiment of this application is a vehicle.
[0033] This application provides an electronic device 1000. For ease of explanation, the following embodiments use a vehicle as an example to illustrate the electronic device 1000. See also... Figure 1The vehicle has a battery pack 1002 installed inside, which can be located at the bottom, front, or rear of the vehicle body 1001. The battery pack 1002 can be used to power the vehicle; for example, it can serve as the vehicle's operating power source. The working part of the electronic device 1000 is electrically connected to the battery pack 1002 to obtain electrical power. The vehicle can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, but are not limited thereto. The working part is the vehicle body, and the battery pack 1002 is located at the bottom of the vehicle body, providing electrical power for the vehicle's movement or the operation of its internal electrical components. However, in some other embodiments, the electronic device 1000 can also be a mobile phone, portable device, laptop, ship, spacecraft, electric toy, and power tool, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; the working part can obtain electrical energy from the battery pack 1002 and perform corresponding functions, such as a fan blade rotation unit or a vacuum cleaner's suction unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the aforementioned electronic device 1000.
[0034] Battery pack 1002 may include multiple secondary batteries (such as cylindrical batteries). In the following description, cylindrical batteries are used as an example of secondary batteries. Figure 2 A perspective view of a secondary battery 100 according to an embodiment of this application is shown. Figure 3 A cross-sectional view of a secondary battery 100 according to an embodiment of this application is shown.
[0035] See Figure 2 and Figure 3The secondary battery 100 includes an electrode assembly 120, a housing 200, and a cover plate 202. The housing 200 and the cover plate 202 are components that jointly house the electrode assembly 120. The housing 200 can be made of any of a variety of available materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The housing 200 can be cylindrical and defines a receiving cavity in which the electrode assembly 120 is disposed. The diameter of the housing 200 can be determined according to the specific size of the electrode assembly 120, such as 18mm, 21mm, 46mm, etc. In some embodiments, the secondary battery 100 can be a 4680 cylindrical battery (outer diameter 46mm, height 80mm), or a 4695 cylindrical battery (outer diameter 46mm, height 95mm), or a 46120 cylindrical battery (outer diameter 46mm, height 120mm).
[0036] The outer casing 200 can be connected to the negative terminal of the electrode assembly 120. One end of the outer casing 200 along the height direction H may have a mounting opening 205, and a cover plate 202 is disposed at the mounting opening 205 and seals the receiving cavity. The secondary battery 100 may also have a terminal post 208 at the end opposite to the cover plate 202, and the terminal post 208 can be connected to the positive terminal of the electrode assembly 120. It should be understood that the terminal post 208 and the outer casing 200 are in an insulated connection state to avoid short circuit of the battery.
[0037] See Figure 3 The housing 200 also has an inwardly protruding crimping portion 203 near the mounting port 205. Along the height direction H of the secondary battery 100, the electrode assembly 120 is disposed between the end wall 111 and the crimping portion 203. The crimping portion 203 restricts the axial movement (movement in the height direction H) of the electrode assembly 120 between the end wall 111 of the housing 200 and the crimping portion 203. The cover plate 202 may have a weak point. When thermal runaway occurs in the battery, the high-temperature, high-pressure emissions can be discharged to the outside from the bottom of the battery, breaking through the weak point on the cover plate 202, thus achieving effective discharge of the emissions.
[0038] The electrode assembly 120 may include a wound first electrode (e.g., a positive electrode) and a second electrode (e.g., a negative electrode), with a diaphragm disposed between the first and second electrodes. The diaphragm may be made of, for example, PP (polypropylene) or PE (polyethylene). To provide protection and insulation for the electrode assembly 120, an insulating film may be wrapped around the outside of the electrode assembly 120. The insulating film may be synthesized from, for example, PP, PE, PET (polyethylene terephthalate), PVC (polyvinyl chloride), or other polymer materials.
[0039] The electrode assembly 120 has a positive electrode tab and a negative electrode tab at both ends of the secondary battery 100 in the height direction H. In some embodiments, the positive electrode tab faces the end wall 111 and is electrically connected to the terminal post 208, making the terminal post 208 positively charged; the negative electrode tab faces the mounting port 205, and the housing 200 is electrically connected to the negative electrode tab, thus becoming negatively charged. However, in other embodiments, the negative electrode tab may be connected to the terminal post 208, and the positive electrode tab may be connected to the housing 200.
[0040] Figure 4 This is a cross-sectional view of the first electrode of a secondary battery according to an embodiment of this application. See also... Figure 4 The first electrode 10 includes a first current collector 18 and a first active material layer 16. The first current collector 18 has a first surface 18a and a second surface 18b opposite each other in its thickness direction. A portion of the surface of the first surface 18a and the second surface 18b is covered by the first active material layer 16.
[0041] In some embodiments, the first electrode 10 is a positive electrode, and the first active material layer 16 is a positive active material layer. In some embodiments, the positive active material of the first active material layer 16 can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The first current collector 18 is a positive current collector, and the material of the positive current collector can be aluminum. The first active material layer 16 can be formed by coating the first current collector 18 using a coating device.
[0042] The first active material layer 16 on the first surface 18a includes a first flat region 14a and a first thinned region 12a adjacent to each other. The direction from the first flat region 14a to the first thinned region 12a is the width direction D of the first electrode 10. In some embodiments, the width direction D of the first electrode 10 corresponds to the height direction of the secondary battery. The first active material layer 16 on the second surface 18b includes a first flat region 14b and a first thinned region 12b adjacent to each other. The thicknesses of the first thinned regions 12a and 12b may be less than the thicknesses of the first flat regions 14a and 14b, respectively.
[0043] In the width direction D, the first thinned region 12a of the first active material layer 16 on the first surface 18a has a first end 12e1, and the first active material layer 16 on the second surface 18b has a second end 12e2. The first end 12e1 and the second end 12e2 of the first active material layer 16 on the first surface 18a and the second surface 18b may not be aligned. In this embodiment, the first end 12e1 extends beyond the second end 12e2 in the width direction D.
[0044] Since the first end 12e1 extends beyond the second end 12e2, the first active material layer 16 on the first surface 18a includes a first region A1 that extends beyond the second end 12e2 in the width direction D, and a second region A2 that does not extend beyond the second end 12e2 in the width direction D. The first region A1 is specifically the portion of the first thinned region 12a that extends beyond the second end 12e2 in the width direction D.
[0045] Figure 5A This is a schematic diagram of the first active material layer of the first electrode. Figure 5B and Figure 5C These are SEM images and schematic diagrams showing the porosity variations in different regions of the first active material layer. (Reference) Figures 5A to 5C As shown, according to an embodiment of this application, the pore size of the first region A1 is larger than that of the second region A2. This pore size configuration is more suitable for electrode manufacturing processes. This is because, during electrode manufacturing, when the first active material layer 16 is coated, a first thinning region 12a and a first flat region 14a are formed, and during the rolling process of the coated first active material layer 16, the active material layer in the first region A1 may not be pressed down. By setting the first region A1 to have larger pores, this application allows for a smaller weight and fewer particles per unit volume in the active material layer of the first region A1, making it more suitable for rolling processes.
[0046] In some embodiments, the porosity of the first active material layer 16 can be measured by the following method: a test area of 1000 μm × 100 μm is selected on the surface of the active material layer 16. The surface of the active material layer 16 refers to the surface of the active material layer on the side away from the first current collector 18. All the gaps between particles in this area are counted. The brightness between particles and pores in the image is distinguished, with the brighter ones being particles and the darker ones being pores. Then, the image is processed by software, adjusting the particles to a black background and the pores to white. The area occupied by the pores in the entire image is counted to obtain the surface porosity.
[0047] Figure 6 Example porosity measurements of different regions in the first active material layer are shown. (Reference) Figure 6 As shown, the porosity of the first active material layer 16 can gradually decrease within the range of 20% to 8%. Specifically, the porosity in the first region A1 can be greater than 18%, for example, 18.6%; the porosity in the second region A2 can be less than 18%, for example, within the range of 17% to 9%. From these measurement results, it can be seen that, according to the electrode manufacturing process, the porosity of the first region A1 can be greater than that of the second region A2 in the technical solution of this application. In some embodiments, the first flat region 14a can have a substantially uniform porosity, that is, within the error range of the coating process, the porosity remains substantially unchanged, for example, approximately 9%.
[0048] See again Figure 4 As shown, the first active material layer 16 on the second surface 18b of the first current collector 18 sequentially includes a first flat region 14b and a first thinned region 12b in the width direction D. In this embodiment, the second end 12e2 of the first active material layer 16 on the second surface 18b is the end of the first thinned region 12b. That is, the first region A1 is the region formed by the positional difference between the ends of the first thinned regions 12a and 12b of the first active material layer 16 on the first surface 18a and the second surface 18b. In some embodiments, the width of the first region A1 in the width direction can be approximately 100 micrometers. Such a width value conforms to the error range of the electrode manufacturing process.
[0049] Specifically, the second region A2 may include a portion of the first thinned region 12a, specifically a first thinned region A3, which does not extend beyond the second end 12e2 in the width direction D. The second region A2 also includes a first flat region 14a. In some embodiments, the pore size of this portion of the first thinned region A3 is smaller than that of the first region A1 but larger than that of the first flat region 14a. This pore size configuration is more suitable for electrode manufacturing processes. Because this portion of the first thinned region A3 has a larger weight and more particles per unit volume than the active material layer in the first region A1, after the rolling process, the pore size of this portion of the first thinned region A3 will be smaller than that of the first region A1 but larger than that of the first flat region 14a.
[0050] Figure 7 This is a cross-sectional view of the first electrode of a secondary battery according to another embodiment of this application. See also... Figure 7 As shown, in some embodiments, an insulating layer 40 is disposed on the first surface 18a and the second surface 18b of the first current collector 18. The insulating layer 40 covers the first end 12e1 and the second end 12e2 of the first active material layer 16 on the first surface 18a and the second surface 18b, and extends to the first surface 18a and the second surface 18b not covered by the first active material layer 16.
[0051] In some embodiments, the insulating layer 40 is mainly composed of boehmite and PVDF (polyvinylidene fluoride). Boehmite accounts for 80% of the composition, and PVDF accounts for 20%. In some embodiments, the insulating layer is a ceramic material layer. The thickness of the insulating layer 40 is 1.5mm-2.5mm, for example, 1.5mm, 1.7mm, 2mm, 2.1mm, 2.3mm, or 2.5mm. By setting the thickness range of the insulating layer 40, it is avoided that the coating thickness of the insulating layer 40 is too thin, making it difficult to obtain the required electrical insulation and support strength; at the same time, it is avoided that the thickness of the insulating layer 40 is too thick, which may lead to a longer curing time for the coating layer and an increase in the overall structural thickness.
[0052] In some embodiments, the insulating layer 40 includes a color developer to distinguish whether the side coated with the insulating layer 40 is the front or back side of the first electrode 10 through the color development effect of the color developer, including but not limited to distinguishing the areal density of the front and back sides of the first electrode 10. The main component of the color developer may be bismuth vanadate, which is yellow in color.
[0053] In the width direction D, the insulating layer 40 on the first surface 18a has a first end 40e1, and the insulating layer 40 on the second surface 18b has a second end 40e2. The first end 40e1 of the insulating layer 40 on the first surface 18a extends beyond the second end 40e2 of the insulating layer 40 on the second surface 18b in the width direction D. This positional difference between the first end 40e1 and the second end 40e2 of the insulating layer 40 on the first surface 18a and the second surface 18b also applies to the electrode manufacturing process. Because in the electrode manufacturing process, the width of the insulating layer 40 formed is consistent in the width direction, that is, the width of the insulating layer 40 on the first surface 18a and the insulating layer 40 on the second surface 18b is consistent, therefore, there will be a positional difference between the insulating layer 40 formed on the first surface 18a and the second surface 18b, so that the first end 40e1 of the insulating layer 40 on the first surface 18a extends beyond the second end 40e2 of the insulating layer 40 on the second surface 18b in the width direction D.
[0054] In some embodiments, the pore size of the first region A1 is larger than that of the insulating layer 40. As described above, this pore size configuration is more suitable for electrode manufacturing processes. Because the active material layer in the first region A1 can be prevented from being pressed down when the coated first active material layer 16 is rolled, the pore size in the first region A1 can be maximized.
[0055] Figure 8 This is a cross-sectional view of the first and second electrodes of a secondary battery according to another embodiment of this application. (Reference) Figure 8As shown, a second electrode 20 is illustrated. In some embodiments, the second electrode 20 is a negative electrode. The second electrode 20 may include a second current collector 28 and a second active material layer 26. The second current collector 28 may be a negative electrode current collector, and the material of the negative electrode current collector may be copper. The second active material layer 26 may be a negative electrode active material, and the negative electrode active material may be carbon or silicon, etc.
[0056] The second current collector 28 has a first surface 28a and a second surface 28b opposite to each other in its thickness direction. A portion of the surfaces of the first surface 28a and the second surface 28b of the second current collector 28 is covered by a second active material layer 26. The second active material layer 26 on the first surface 28a sequentially includes a second flat region 24a and a second thinned region 22a in the opposite direction of the width direction D. The second active material layer 26 on the second surface 28b sequentially includes a second flat region 24b and a second thinned region 22b in the opposite direction of the width direction D. That is, for the second electrode 20, the direction from the second flat regions 24a, 24b to the corresponding second thinned regions 22a, 22b is in the opposite direction of the width direction. In this embodiment, the secondary battery can be a cylindrical battery.
[0057] In the width direction D, the second straight region 24a on the first surface 28a of the second current collector 28 has a first end 24e1, and the second straight region 24b on the second surface 28b of the second current collector 28 has a second end 24e2. The first end 24e1 and the second end 24e2 can be flush with each other, and the first end 24e1 and the second end 24e2 extend beyond the first end 12e1 of the first thinned region 12a of the first active material layer 16 of the first electrode 10 in the width direction D. In this way, lithium ions detached from the positive active material layer of the first electrode 10 (positive electrode) can be embedded into the negative active material layer of the second electrode 20 (negative electrode), thereby avoiding lithium plating on the second electrode 20.
[0058] Figure 9 This is a cross-sectional view of the first and second electrodes of a secondary battery according to another embodiment of this application. (Reference) Figure 9 As shown, with Figure 8 The difference in the illustrated embodiment is that, for the second electrode 20, the direction from the second flat regions 24a, 24b to the corresponding second thinned regions 22a, 22b is the width direction D. In this embodiment, the secondary battery can be, for example, a prismatic battery.
[0059] In this embodiment, in the width direction D, the second straight region 24a on the first surface 28a of the second current collector 28 has a first end 24e3, which is connected to the corresponding second thinning region 22a. The second straight region 24b on the second surface 28b of the second current collector 28 has a second end 24e4, which is connected to the corresponding second thinning region 22b. Due to process errors, the second thinning regions 22a and 22b on the first surface 28a and the second surface 28b may have positional differences. In this embodiment, the second end 24e4 extends beyond the first end 24e3 in the width direction D.
[0060] In some embodiments, the first end 24e3 of the second straight region 24a of the second electrode 20 extends beyond the first end 12e1 of the first thinned region 12a of the first active material layer 16 of the first electrode 10 in the width direction D. That is, in the width direction D, one end (first end 24e3) of the second straight region of the second electrode 20 extends beyond the longer end (first end 12e1) of the first thinned region of the first electrode 10. In this way, lithium ions detached from the positive active material layer of the first electrode 10 (positive electrode) can be embedded into the negative active material layer of the second electrode 20 (negative electrode), thereby avoiding lithium plating on the second electrode 20.
[0061] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A secondary battery, characterized in that, The electrode assembly includes a first electrode, a second electrode, and a diaphragm disposed between the first electrode and the second electrode. The first electrode includes a first current collector and a first active material layer. The first current collector has a first surface and a second surface opposite each other in its thickness direction. A portion of the first surface and the second surface of the first current collector are covered by the first active material layer. The first active material layer on the first surface includes a first flat region and a first thinned region, wherein the direction from the first flat region to the first thinned region is the width direction of the first electrode sheet. In the width direction, the first thinned region has a first end, and the first active material layer on the second surface has a second end, the first end extending beyond the second end in the width direction. The first active material layer on the first surface includes a first region extending beyond the second end in the width direction and a second region not extending beyond the second end in the width direction, wherein the pores of the first region are larger than the pores of the second region.
2. The secondary battery according to claim 1, characterized in that, The first active material layer on the second surface sequentially includes a first flat region and a first thinned region, and the second end is the end of the first thinned region of the first active material layer on the second surface.
3. The secondary battery according to claim 1, characterized in that, Also includes: An insulating layer covers the first end and the second end, and extends to the first surface and the second surface not covered by the first active material layer. In the width direction of the first electrode, the insulating layer on the first surface has a first end and the insulating layer on the second surface has a second end, wherein the first end of the insulating layer on the first surface extends beyond the second end of the insulating layer on the second surface in the width direction.
4. The secondary battery according to claim 3, characterized in that, The porosity of the first region is larger than that of the insulating layer.
5. The secondary battery according to claim 1, characterized in that, The second region includes a portion of the first thinning region that does not extend beyond the second end in the width direction, and the first straight region, wherein the pore size of the portion of the first thinning region is smaller than the pore size of the first region and larger than the pore size of the first straight region.
6. The secondary battery according to claim 1, characterized in that, The second electrode includes a second current collector and a second active material layer. The second current collector has a first surface and a second surface opposite to each other in its thickness direction. A portion of the first surface and the second surface of the second current collector are covered by the second active material layer. The second active material layer on the first surface and the second surface of the second current collector respectively includes a second straight region and a second thinned region in the width direction. In the width direction, a second straight region on the first surface of the second current collector has a first end, and a second straight region on the second surface of the second current collector has a second end, the second end of the second straight region extending beyond the first end of the second straight region in the width direction. Furthermore, the first end of the second straight region extends beyond the first end of the first thinned region of the first active material layer in the width direction.
7. The secondary battery according to claim 1, characterized in that, The second electrode includes a second current collector and a second active material layer. The second current collector has a first surface and a second surface opposite to each other in its thickness direction. A portion of the first surface and the second surface of the second current collector are covered by the second active material layer. In the opposite direction of the width direction, the second active material layer on the first surface and the second surface of the second current collector respectively includes a second flat region and a second thinned region. In the width direction, the second flat region on the first surface of the second current collector has a first end, and the second flat region on the second surface of the second current collector has a second end. The first end and the second end of the second flat region are flush and extend beyond the first end of the first thinned region of the first active material layer in the width direction.
8. The secondary battery according to claim 1, characterized in that, The first electrode is a positive electrode.
9. A battery pack, characterized in that, The secondary battery includes any one of claims 1 to 8.
10. An electronic device, characterized in that, Includes the battery pack as described in claim 9.