Secondary batteries and electronic devices

Abstract

The present application provides a secondary battery and an electronic device. The secondary battery includes a positive electrode sheet. The positive electrode sheet includes a current collector, a tab protruding from the current collector, and an insulating layer provided on at least one surface of the current collector. The insulating layer is provided along a side edge of the current collector close to the tab and is adjacent to the active material layer. Here, the ratio of the thickness of the insulating layer to the thickness of the active material layer is 0.5 to 0.7, and the thickness of the active material layer is 200 to 400 μm.

Description

Technical Field

[0001] This application relates to the field of energy storage devices, and particularly to secondary batteries and electronic devices equipped with secondary batteries.

Background Art

[0002] An insulating layer for preventing burrs is usually provided at the edge of the electrode sheet of a battery. The active material layer and the insulating layer are usually coated synchronously on the surface of the current collector of the electrode sheet. However, in the drying process, the active material layer and the insulating layer may penetrate each other at the boundary position and cause melting. Eventually, the boundary line at the boundary position between the dried active material layer and the insulating layer is blurred, resulting in variations in the determination of the position of the active material layer, affecting the dimensions of the electrode sheet, and further causing a risk of low capacity of the battery.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The object of this application is to provide a secondary battery and an electronic device that can improve the problem of affecting the size of the electrode sheet due to the interaction region at the boundary between the active material layer and the insulating layer.

Means for Solving the Problems

[0004] The first aspect of this application provides a secondary battery including a positive electrode sheet. The positive electrode sheet includes a current collector, a tab protruding from the current collector, and an insulating layer provided on at least one surface of the current collector. The insulating layer is provided along the side adjacent to the tab of the current collector and is adjacent to the active material layer. Here, the ratio of the thickness of the insulating layer to the thickness of the active material layer is 0.5 to 0.7, and the thickness of the active material layer is 200 to 400 μm.

[0005] In the secondary battery provided by this invention, by controlling the thickness of the active material layer to 200 to 400 μm and controlling the ratio of the thickness of the insulating layer to the thickness of the active material layer to 0.5 to 0.7, the dimensions of the interaction region at the boundary between the active material layer and the insulating layer, which is formed when the active material paste and insulating paste penetrate and mix with each other during the coating process, can be reduced, thereby reducing the influence of the interaction region on the dimensions of the electrode sheet.

[0006] According to some embodiments of the present invention, the ratio of the thickness of the insulating layer to the thickness of the active material layer is 0.6 to 0.7, which is more advantageous for reducing the size of the interaction region.

[0007] According to some embodiments of the present invention, the dimensions of the interaction region can be further reduced by controlling the thickness of the active material layer to 200-370 μm. Furthermore, the dimensions of the interaction region can be further reduced by controlling the thickness of the active material layer to 200-280 μm.

[0008] According to several embodiments of this application, the coating weight of the active material layer is 427-740 mg / 1540.25 mm 2 This is advantageous for reducing the size of the interaction area.

[0009] According to several embodiments of this application, the coating weight of the active material layer is 427-640 mg / 1540.25 mm 2 That is the case.

[0010] According to some embodiments of the present invention, the compaction density of the active material layer is 2.6 to 3 g / cc, which is advantageous for reducing the size of the interaction region.

[0011] According to some embodiments of the present application, the insulating layer contains inorganic particles comprising one or more of alumina, boehmite, zirconia, boron oxide, or hexagonal boron nitride.

[0012] According to some embodiments of the present application, the active material layer contains an active material comprising one or more of the following: lithium nickel cobalt manganate, lithium manganate, lithium iron phosphate, or lithium manganese iron phosphate.

[0013] According to some embodiments of the present invention, the active material consists of lithium manganate and lithium iron phosphate, and the mass ratio of lithium manganate to lithium iron phosphate is 3.5 to 12, which appropriately adjusts the width of the interaction region of the secondary battery and the thickness expansion rate of the secondary battery after storage.

[0014] According to some embodiments of the present invention, the active material consists of lithium manganate and lithium iron phosphate, and the mass ratio of lithium manganate to lithium iron phosphate is 4 to 10, which can further reduce the thickness expansion rate of the secondary battery after storage.

[0015] A second aspect of the present application provides an electronic device including a secondary battery according to any of the above embodiments. [Brief explanation of the drawing]

[0016] The above-mentioned and / or additional aspects and advantages of the present application will be evident and readily apparent from the following description of embodiments associated with the drawings. Here, [Figure 1] This is a schematic diagram of a partial plan view of a positive electrode sheet provided by one embodiment of the present invention. [Figure 2] Figure 1 is a schematic cross-sectional view of the positive electrode sheet along the line II-II. [Modes for carrying out the invention]

[0017] The following describes in detail the technical aspects of the embodiments of the present application, but it is clear that the embodiments described are only a selection of embodiments of the present application, not all embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present application. The terms used in this specification are for the purpose of describing specific embodiments and are not intended to limit the present application.

[0018] The embodiments of the present application will be described in detail below. However, the present application can be embodied in many different forms and should not be construed as being limited to the exemplary embodiments described herein. Rather, by providing these exemplary embodiments, the present application will be communicated to those skilled in the art in full and in detail.

[0019] Furthermore, for conciseness and clarity, the sizes or thicknesses of various components, layers, etc., are shown enlarged in the drawings. Throughout the text, the same numbers refer to the same element. As used herein, the terms “and / or” include any and all combinations of one or more related enumerated items. Furthermore, when element A is said to be “connected” to element B, element A may be directly connected to element B, or there may be an intermediate element C present. That is, elements A and B may be indirectly connected to each other.

[0020] Furthermore, when "possible" is used to describe embodiments of the present application, it means "one or more embodiments of the present application." 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, singular forms are intended to include plural forms unless the context specifically indicates otherwise. Furthermore, as used herein, the term "including" means the presence of the described features, figures, steps, operations, elements and / or components, but it should be understood that this does not exclude the presence or addition of one or more other features, figures, steps, operations, elements, components and / or combinations thereof.

[0021] Spatial-related terms such as "upper" can be used in this specification for the purpose of briefly explaining in the figures the relationship between one element or feature and another element(s) or feature(s). Spatial-related terms are intended to include different directions of the device during use or operation in addition to the directions described in the figures. For example, if the device in the figure is inverted, an element described as "above" or "upper" of another element will be positioned "below" or "lower surface" of the other element. Therefore, the exemplary term "upper" can include the upper and lower directions. Terms such as first, second, third, etc. are used in this specification to describe various elements, components, regions, layers, and / or parts, but it should be understood that 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. Therefore, the first element, component, region, layer or part discussed below can be referred to as the second element, component, region, layer or part on the premise of not departing from the teachings of the exemplary embodiments.

[0022] In the prior art, as the demand for high energy density batteries by people increases, generally, in order to improve the battery capacity, it is necessary to install an active material layer with a larger coating weight on the upper surface of the electrode sheet. As a result, the large coating weight leads to an increase in the thickness of the active material layer. The applicant has discovered that when forming a thick active material layer by coating, the boundary line at the boundary position between the active material layer and the insulating layer becomes blurred, and the active material layer and the insulating layer penetrate and mix with each other at the boundary position to form an interaction region, which affects the dimensions of the electrode sheet. \(

[0023] Based on the above problems discovered by the applicant, the applicant improves the thickness of the active material layer and the insulating layer of the polar sheet to reduce the dimensions of the interaction region, and further reduces the influence on the dimensions of the polar sheet due to the existence of the interaction region. Hereinafter, the embodiments of the present invention will be further described.

[0024] The secondary battery according to an embodiment of the present application includes a housing, a positive electrode sheet, a negative electrode sheet, a separator, and an electrolytic solution housed in the housing, and a separator is provided between the positive electrode sheet and the negative electrode sheet.

[0025] Refer to FIGS. 1 and 2. The positive electrode sheet 10 includes a current collector 11, a tab 12, an active material layer 13, and an insulating layer 14. The current collector 11 includes a first surface 11a and a second surface 11b arranged opposite to each other. The tab 12 protrudes from a side edge of the current collector 11 and is connected to the first surface 11a and the second surface 11b. The active material layer 13 is provided on the first surface 11a and is spaced apart from the tab 12. In other embodiments, the active material layer 13 may be arranged on the first surface 11a and the second surface 11b in order to increase the energy density. The insulating layer 14 is provided on the first surface 11a along the side edge of the tab 12 along the current collector 11 and is adjacent to the active material layer 13. Along the direction perpendicular to the first surface (the thickness direction of the positive electrode sheet 10), the thickness of the active material layer is 200 to 400 μm, and the ratio of the thickness H of the insulating layer 14 to the thickness T of the active material layer 13 is 0.5 to 0.7.

[0026] As the current collector 11, any positive electrode current collector known in the art, such as a copper foil, a copper alloy foil, or a composite current collector, can be used. The tab 12 and the current collector 11 are integrally formed. For example, the current collector 11 and the tab 12 are formed by cutting one copper foil.

[0027] [[ID=ID=13]]The insulating layer 14 includes inorganic particles and a binder. Examples of the inorganic particles include one or more of alumina, boehmite, zirconia, boron oxide, or hexagonal boron nitride. Examples of the binder include one or more of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, and sodium carboxymethyl cellulose.

[0028] The active material layer 13 includes an active material, a conductive agent, and a binder. Examples of the active material include one or more of lithium nickel cobalt manganate, lithium manganate, lithium iron phosphate, or lithium manganese iron phosphate. Any conductive agent known in the art can be used as the conductive agent. For example, examples of conductive agents include one or more of conductive Ketjenblack, Super-P, acetylene black, graphene, carbon nanotubes, and carbon fibers. Any binder known in the art can be used as the binder. For example, the binder includes one or more of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, and sodium carboxymethylcellulose.

[0029] The active material layer 13 and the insulating layer 14 are manufactured by a simultaneous coating process. In some embodiments, the method for manufacturing a secondary battery comprises the following steps.

[0030] The active material, conductive agent, and binder are dissolved in a solvent to form an active paste with a solid content of 65% or more. Of this paste, the proportion of the active material is 95.5% or more.

[0031] Inorganic particles and a binder are dissolved in a solvent to form an insulating paste with a solid content of 30-50%. Of this paste, inorganic particles make up 80% or more.

[0032] The activating paste and insulating paste are applied synchronously to the surface of the current collector 11.

[0033] The active paste coating and the insulating paste coating are dried to form an active material layer 13 and an insulating layer 14, thereby obtaining a positive electrode sheet 10.

[0034] A secondary battery is manufactured by laminating or winding a positive electrode sheet 10, a separator film, and a negative electrode sheet. The solvent may include, but is not limited to, one or more of N-methylpyrrolidone, anhydrous ethanol, and acetone.

[0035] In this invention, by controlling the thickness of the active material layer 13 to 200-400 μm and controlling the ratio of the thickness of the insulating layer 14 to the thickness of the active material layer 13 to 0.5-0.7, the dimensions of the interaction region at the boundary between the active material layer 13 and the insulating layer 14, which is formed by the penetration and melting of the active material paste and insulating paste during coating, can be reduced, thereby improving the influence of the interaction region on the dimensions of the electrode sheet.

[0036] If the ratio of the thickness H of the insulating layer 14 to the thickness T of the active material layer 13 is less than 0.5, the difference in thickness between the insulating layer 14 and the active material layer 13 is too large. During the drying process, under the fluidity and surface tension of the active paste, the active paste and insulating paste tend to mix at the boundary to form interaction regions, and the size of these interaction regions becomes too large, affecting the size of the positive electrode sheet 10. Also, if the ratio of the thickness H of the insulating layer 14 to the thickness T of the active material layer 13 is less than 0.5, the thickness H of the insulating layer 14 may become too small. If the height of the burr formed by cutting is greater than the thickness H of the insulating layer 14, the burr may pierce the insulating layer 14, making it easier to cause a short circuit between the positive and negative electrodes, which can lead to safety problems.

[0037] If the ratio of the thickness H of the insulating layer 14 to the thickness T of the active material layer 13 is greater than 0.7, the thickness H of the insulating layer 14 becomes close to the thickness T of the active material layer 13. This means that during the cold pressure process of the secondary battery 100, the insulating layer 14 may be compressed, and because inorganic particles are incompressible, the partial current collector 11 corresponding to the insulating layer 14 may be damaged by the pressure, causing a cold pressure breakage problem. Also, if the ratio of the thickness H of the insulating layer 14 to the thickness T of the active material layer 13 is greater than 0.7, the difference in solid content between the insulating paste and the active paste becomes too large, resulting in a coating weight (740 mg / 1540.25 mm). 2 When increasing the thickness of the insulating layer 14 by increasing the size of the (reaching) value, the insulating layer may not dry completely during application and may adhere to the adhesive roll, causing problems such as scratches on the electrode sheet and tape breakage.

[0038] In some embodiments, the ratio of the thickness H of the insulating layer 14 to the thickness T of the active material layer 13 is 0.6 to 0.7, which is further advantageous in reducing the size of the interaction region.

[0039] In some embodiments, the size of the interaction region can be further reduced by controlling the thickness of the active material layer to 200-370 μm.

[0040] In some embodiments, the thickness of the active material layer 13 is adjusted by controlling the coating weight and compaction density of the active material layer 13.

[0041] In some embodiments, the coating weight of the active material layer 13 was 427-740 mg / 1540.25 mm 2 The compaction density of the active material layer 13 is 2.6 to 3 g / cc. In this way, the thickness of the active material layer 13 can be controlled to an appropriate level, which is advantageous for reducing the size of the interaction area. Preferably, the coating weight of the active material layer 13 is 427 to 640 mg / 1540.25 mm 2 That is the case.

[0042] In some embodiments, the thickness of the insulating layer 14 is adjusted by controlling the solid content of the insulating paste and the coating weight of the insulating layer 14.

[0043] In some embodiments, the active material of the active material layer 13 consists of lithium manganese oxide and lithium iron phosphate, with a mass ratio of 3.5 to 12. The higher the lithium manganese oxide content, the more gas is generated within the secondary battery. By controlling the mass ratio of lithium manganese oxide to lithium iron phosphate to 3.5 to 12, the width of the interaction region and the thickness expansion rate of the secondary battery after storage can be appropriately controlled.

[0044] In some embodiments, the active material consists of lithium manganate and lithium iron phosphate, with a mass ratio of 4 to 10, which can further reduce the thickness expansion rate of the secondary battery after storage.

[0045] In some embodiments, the active material of the active material layer 13 consists of lithium manganate and lithium iron phosphate, and the mass ratio of lithium manganate to lithium iron phosphate is preferably 3.5 to 9, and more preferably 3.5 to 7.65.

[0046] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material provided on the surface of the negative electrode current collector. Here, the negative electrode current collector can be any negative electrode current collector known in the art, such as copper foil, copper alloy foil, or composite current collector. The negative electrode active material can be any negative electrode active material known in the art. For example, the negative electrode active material can include at least one of graphite, hard carbon, soft carbon, silicon, silicon carbon, or silicon oxide. The negative electrode active material may also include a conductive agent and a binder. The conductive agent may include at least one of conductive carbon black (Super-P), carbon nanotubes (CNTs), carbon fibers, or graphene. The binder may include at least one of styrene-butadiene rubber (SBR), polyvinyl alcohol (PVa), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or sodium carboxymethylcellulose (CMC-Na).

[0047] The separator may be any separator known in the art. For example, the separator can be selected from films made of one or more materials from polyethylene, polypropylene, nonwoven fabric, and polyfiber.

[0048] The electrolyte may be any electrolyte known in the art. For example, the electrolyte may be one or more selected from organic carbonates, including ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, etc., which are electron insulating and ion conductive. As a solvent, TiPF6, TiBF4, TiBOB, TiA S It contains one or more lithium salts from among F6, Ti(CF3SO2)2N, TiCF3SO3, and TiCTO4 as a solute.

[0049] The housing may be any housing known in the art. For example, the housing may be a packaging bag sealed with an sealing film such as an aluminum-plastic film or a steel-plastic film. Alternatively, the housing may be a metal housing such as a steel housing or an aluminum housing.

[0050] Another embodiment of the present application provides an electronic device including the above-described secondary battery. The electronic device may be any power-using equipment that uses an electrochemical device. For example, the electronic device may be a mobile phone, a portable device, a laptop computer, a battery car, an electric vehicle, a steamship, a spacecraft, an electric toy, and a power tool.

[0051] The following are some specific examples and comparative examples provided to better illustrate the present invention. <Example 1> An active paste with 67% solid content is obtained by dispersing 9.64% lithium iron phosphate, 86.76% lithium manganese (with a mass ratio of 9 of lithium manganese to lithium iron phosphate), 0.6% conductive carbon paste, 1.2% conductive carbon black, and 1.8% polyvinylidene fluoride in nitrogen methylpyrrolidone. An insulating paste with 35% solid content is obtained by dispersing 88% boehmite and 12% polyvinylidene fluoride in nitrogen methylpyrrolidone. The active paste and insulating paste are applied to aluminum foil to form an active coating and an insulating coating. The active coating and insulating coating are adjacent, and the thickness of the active coating and the insulating coating are equal. The active coating and insulating coating are dried to obtain an active material layer and an insulating layer. Subsequently, a positive electrode sheet as shown in Figure 1 is obtained by cold pressing, dicing, and stripping. Here, the coating weight of the active material layer is 427 mg / 1540.25 mm 2 The compaction density of the active material layer is 3 g / cc, the thickness T of the active material layer is 200 μm, the thickness H of the insulating layer is 130 μm, and the H / T ratio is 0.65.

[0052] After mixing graphite, polyvinylidene fluoride, and conductive carbon black, the mixture is applied to copper foil, and then cold-pressed, diced, and stripped to obtain a negative electrode sheet.

[0053] A positive electrode sheet, a polyethylene separator, and a negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets, and the assembly is wound up to obtain an electrode assembly. Next, the electrode assembly is placed in an aluminum-plastic film, injected with a liquid, and chemically converted to obtain a lithium-ion battery.

[0054] <Example 2-11> Examples 2 to 11 are the same as Example 1 except that at least one of the following differs: the coating weight of the active material layer, the thickness T of the active material layer, the compaction density of the active material layer, and the thickness H and H / T of the insulating layer. Of these, T is 200 to 400 μm and H / T is 0.5 to 0.7.

[0055] <Examples 12-17> Examples 12 to 17 are the same as Example 3 except for the difference in the lithium manganate content, lithium iron phosphate content, and the thickness H of the insulating layer.

[0056] <Example 18> Example 18 is the same as Example 3 except for the lithium iron phosphate, the coating weight of the active material layer, and the compaction density of the active material layer.

[0057] <Comparative Example 1-5> Comparative Examples 1 to 5 are the same as Example 1, except for the coating weight of the active material layer, the thickness T of the active material layer, the compaction density of the active material layer, and the thickness H of the insulating layer.

[0058] Observe and measure the dimensions of the interaction area in Examples 1-18 and Comparative Examples 1-5.

[0059] The positive electrode sheet is removed, cut transversely with a splitting cutter, and the cross-section is analyzed using a scanning electron microscope (SEM). This allows observation of a white insulating layer, a black active material layer, and a gray interaction region located between the white insulating layer and the black active material layer in the width direction of the positive electrode sheet.

[0060] Using the "dotted line mode," measure the distance from the highest point of the white insulating layer to the current collector, repeat the above steps three times, and determine the average value, which is the thickness H of the insulating layer. Move 25-35 mm laterally along the width direction of the electrode sheet, from the edge of the black active material layer toward the back, take three points, measure the distance from the surface of the white active material layer to the current collector, and then determine the average value, i.e., the thickness T of the active material layer.

[0061] Using the "parallel line mode," the distance between two parallel lines, i.e., the width of the interaction region, is measured along the width direction of the electrode sheet, starting from the point where the white insulating layer and the gray interaction region meet, and ending at the point where the black active material layer and the gray interaction region meet. This step is repeated three times, and the average value is calculated; this average value represents the width of the interaction region.

[0062] Observe the frequency of tape breakage during cold pressing of the positive electrode sheet.

[0063] If the width of the interaction area is 0.5 mm or less, and the tape cutting frequency is 20,000 m / cut or more, then it is determined that this is within the acceptable range for the product and process, and the effect is judged to be "OK". Conversely, if the interaction area does not meet these criteria, the effect is judged to be "NG".

[0064] The high-temperature storage performance of lithium-ion batteries from Examples 1-18 and Comparative Examples 1-5 will be tested.

[0065] The lithium-ion battery was placed in a 25°C constant temperature chamber and left standing for 5 minutes to allow it to reach a constant temperature. It was then charged to 4.2V with a constant current of 0.5C, charged again with a constant voltage until the current reached 0.05C, left standing for 30 minutes, and then discharged to 2.8V with a constant current of 0.2C, and left standing for 5 minutes. The initial thickness of the lithium-ion battery was measured and recorded using a micrometer. The tested lithium-ion battery was then transferred to a 60°C constant temperature chamber for 60 days for storage. After storage, it was removed, placed in a 25°C constant temperature chamber for 5 minutes to allow it to reach a constant temperature, and its thickness was measured and recorded as the thickness after storage.

[0066] Thickness expansion rate = (Thickness after memory - Initial thickness) / Initial thickness × 100%.

[0067] Table 1 shows the data and measurement results for Examples 1-18 and Comparative Examples 1-5.

[0068] [Table 1-1] [Table 1-2] [Table 1-3]

[0069] From a comparison of Examples 1-12 and Comparative Examples 1-5, when the thickness T of the active material layer is 200-400 μm and the ratio H / T of the insulating layer thickness H to the active material layer thickness is 0.5-0.7, the width of the interaction region is 0.13-0.4 mm and the tape breakage frequency is 20,000-26,000 m / time, indicating that the effect is OK. However, when H / T is 0.6-0.7, the width of the interaction region is 0.13-0.23 mm, which is smaller.

[0070] As can be seen from Examples 3, 12-17, when the thickness of the active material layer and the thickness of the insulating layer are within an appropriate range, the influence of the mass ratio of lithium manganese oxide to lithium iron phosphate on high-temperature storage performance is relatively large. When the mass ratio of lithium manganese oxide to lithium iron phosphate is smaller, the thickness expansion rate after storage is relatively small. When the mass of lithium manganese oxide to lithium iron phosphate is relatively large, the thickness expansion rate after storage is relatively large. Also, as is clear from Example 18, when the positive electrode active material contains only lithium iron phosphate, the width of the interaction region becomes larger. Furthermore, when the positive electrode active material contains only lithium iron phosphate, the drying rate of the active layer is relatively fast, the drying rate of the insulating layer is slow, and the insulating layer flows toward the active layer due to capillary stress. In addition, because the surface tension of the lithium iron phosphate paste is high, the edges of the positive electrode active material layer shrink during drying, the insulating layer paste flows further into the positive electrode active material layer, and the two layers penetrate each other to form the intersection width of the interaction region.

[0071] The embodiments disclosed herein are merely preferred examples and, of course, do not limit the present application. Accordingly, equivalent modifications made based on the present application still fall within the scope covered by the present application. [Explanation of Symbols]

[0072] 10 Positive electrode sheet 11 Current collector 12 tabs 13 Active material layer 14. Insulating layer 11a 1st surface 11b Second Surface

Claims

1. A secondary battery including a positive electrode sheet, wherein the positive electrode sheet is A current collector, a tab protruding from the current collector, An active material layer provided on at least one surface of the current collector, The current collector comprises an insulating layer provided along the side adjacent to the tab and adjacent to the active material layer, The ratio of the thickness of the insulating layer to the thickness of the active material layer is 0.5 to 0.7, and the thickness of the active material layer is 200 to 400 μm. The aforementioned insulating layer is characterized by containing inorganic particles.

2. The secondary battery according to claim 1, characterized in that the ratio of the thickness of the insulating layer to the thickness of the active material layer is 0.6 to 0.

7.

3. The secondary battery according to claim 1, characterized in that the thickness of the active material layer is 200 to 370 μm.

4. The secondary battery according to claim 1, characterized in that the thickness of the active material layer is 200 to 280 μm.

5. The coating weight of the active material layer is 427-740 mg / 1540.25 mm ２ The secondary battery according to claim 1, characterized in that it is the same as the one described in claim 1.

6. The coating weight of the active material layer is 427-640 mg / 1540.25 mm ２ The secondary battery according to claim 5, characterized in that it is the same as the one described in claim 5.

7. The secondary battery according to claim 1, characterized in that the compaction density of the active material layer is 2.6 to 3 g / cc.

8. The secondary battery according to claim 1, characterized in that the inorganic particles include one or more of alumina, boehmite, zirconia, boron oxide, or hexagonal boron nitride.

9. The secondary battery according to claim 1, characterized in that the active material layer includes an active material, and the active material includes one or more of the following: lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium iron phosphate, or lithium manganese iron phosphate.

10. The secondary battery according to claim 9, characterized in that the active material consists of lithium manganate and lithium iron phosphate, and the mass ratio of lithium manganate to lithium iron phosphate is 3.5 to 12.

11. The secondary battery according to claim 9, characterized in that the active material consists of lithium manganate and lithium iron phosphate, and the mass ratio of lithium manganate to lithium iron phosphate is 3.5 to 9.

12. The secondary battery according to claim 9, characterized in that the active material consists of lithium manganate and lithium iron phosphate, and the mass ratio of lithium manganate to lithium iron phosphate is 3.5 to 7.

65.

13. The secondary battery according to claim 9, characterized in that the active material consists of lithium manganate and lithium iron phosphate, and the mass ratio of lithium manganate to lithium iron phosphate is 4 to 10.

14. An electronic device characterized by including a secondary battery as described in any one of claims 1 to 13.

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