Secondary battery and electronic device

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] The present 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 the 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. Finally, 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] An object of the present application is to provide a secondary battery and an electronic device capable of improving the problem that the size of the electrode sheet is affected by the interaction region at the boundary between the active material layer and the insulating layer.

Means for Solving the Problems

[0004] A first aspect of the present 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 the present application, 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 active material paste and the insulating paste penetrate and mix with each other during the coating process, thereby reducing the size of the interaction region at the boundary position between the active material layer and the insulating layer formed, and reducing the influence of the interaction region on the size of the electrode sheet.

[0006] According to some embodiments of the present application, 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 application, by further controlling the thickness of the active material layer to 200 to 370 μm, the size of the interaction region is further reduced. Further, by controlling the thickness of the active material layer to 200 to 280 μm, the size of the interaction region is further reduced.

[0008] According to some embodiments of the present application, the coating weight of the active material layer is 427 to 740 mg / 1540.25 mm 2 which is advantageous for reducing the size of the interaction region.

[0009] According to some embodiments of the present application, the coating weight of the active material layer is 427 to 640 mg / 1540.25 mm 2 and is.

[0010] According to some embodiments of the present application, the consolidation 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 containing 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 including one or more of lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium iron phosphate, or lithium manganese iron phosphate.

[0013] According to some embodiments of the present application, the active material consists of lithium manganese oxide and lithium iron phosphate, and the mass ratio of lithium manganese oxide to lithium iron phosphate is 3.5 to 12, which makes the width of the interaction region of the secondary battery appropriate and the thickness expansion rate after storage of the secondary battery appropriate.

[0014] According to some embodiments of the present application, the active material consists of lithium manganese oxide and lithium iron phosphate, and the mass ratio of lithium manganese oxide to lithium iron phosphate is 4 to 10, and the thickness expansion rate after storage of the secondary battery can be further reduced.

[0015] The second aspect of the present application provides an electronic device including the secondary battery according to any of the above embodiments.

Brief Description of the Drawings

[0016] The above and / or additional aspects and advantages of the present application will become apparent and be easily understood from the description of the embodiments in connection with the following drawings. Here,

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0017] The technical aspects in the embodiments of the present application will be clearly and detailedly described below. Clearly, the described embodiments are only some of the embodiments of the present application, not all of them. Unless otherwise defined, all technical terms and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present application pertains. 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.

[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. Instead, by providing these exemplary embodiments, the present application is fully and detailedly conveyed to those skilled in the art.

[0019] Furthermore, for the sake of brevity and clarity, in the drawings, the sizes or thicknesses of various components and layers are shown enlarged. Throughout the text, the same numerical values refer to the same elements. As used in this specification, the term "and / or" includes any and all combinations of one or more of the associated listed items. Further, when element A is referred to as being "connected to" element B, element A may be directly connected to element B, or there may be an intermediate element C. That is, element A and element B may be indirectly connected to each other.

[0020] Furthermore, when the word "may" is used in describing the embodiments of the present application, it means "one or more embodiments of the present application". The technical terms used in this specification are for the purpose of describing specific embodiments and are not intended to limit the present application. As used in this specification, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Further, as used in this specification, the term "comprising" means the presence of the described features, numerical values, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, numerical values, 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 simply explaining, in order to describe the relationship between one element or feature and another element(s) or feature(s) as illustrated in the figures. The 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 other elements will be positioned "below" or "lower surface" of other elements. Thus, the exemplary term "upper" can include both upward and downward 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. Thus, the first element, component, region, layer, or part discussed below can be referred to as the second element, component, region, layer, or part without 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. This results in an increase in the thickness of the active - material layer due to the large coating weight. 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 blend 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 - mentioned problems discovered by the applicant, the applicant improves the thicknesses 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 of the existence of the interaction region on the dimensions of the polar sheet. Hereinafter, the embodiments of the present invention will be further described.

[0024] A 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 accommodated in the housing, and a separator is provided between the positive electrode sheet and the negative electrode sheet.

[0025] Referring 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 that are disposed 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 disposed 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 11a (the thickness direction of the positive electrode sheet 10), the thickness of the active material layer 13 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] 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 - hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, and sodium carboxymethyl cellulose.

[0028] The active material layer 13 contains 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. As the conductive agent, any conductive agent known in the art can be used. For example, examples of the conductive agent include one or more of conductive ketjen black, Super-P, acetylene black, graphene, carbon nanotubes, carbon fibers, etc. As the binder, any binder known in the art can be used. For example, the binder can include one or more of polyvinylidene fluoride, a copolymer of vinylidene fluoride - hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose.

[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] Dissolve the active material, the conductive agent, and the binder in a solvent to form an active paste with a solid content of 65% or more. Among them, the proportion of the active material is 95.5% or more.

[0031] Dissolve the inorganic particles and the binder in a solvent to form an insulating paste with a solid content of 30 - 50%. Among them, the proportion of the inorganic particles is 80% or more.

[0032] Simultaneously apply the active paste and the insulating paste onto the surface of the current collector 11.

[0033] Dry the active paste coating film and the insulating paste coating film to form the active material layer 13 and the insulating layer 14, and obtain the positive electrode sheet 10.

[0034] Stack or wind the positive electrode sheet 10, the separator film, and the negative electrode sheet to fabricate a secondary battery. The solvent can include, but is not limited to, one or more of N - methylpyrrolidone, absolute ethanol, and acetone.

[0035] In this application, by controlling the thickness of the active material layer 13 to be 200 to 400 μm and controlling the ratio of the thickness of the insulating layer 14 to the thickness of the active material layer 13 to be 0.5 to 0.7, during coating, due to the penetration and mixing of the active material paste and the insulating paste, the size of the interaction region at the boundary between the active material layer 13 and the insulating layer 14 can be reduced, and the influence of the interaction region on the size of the electrode sheet can be improved.

[0036] When 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 difference between the insulating layer 14 and the active material layer 13 is too large. During the drying process, under the fluidity of the active paste and the surface tension of the active paste, the active paste and the insulating paste are likely to mix at the boundary position to form an interaction region, and the size of the interaction region is too large, which affects the size of the positive electrode sheet 10. Also, when 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 small. If the height of the burr formed by cutting is larger than the thickness H of the insulating layer 14, the burr may pierce the insulating layer 14, easily causing a short circuit inside the positive and negative electrodes and potentially causing safety problems.

[0037] When 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 approaches the thickness T of the active material layer 13. As a result, in the cold pressing process of the secondary battery 100, the insulating layer 14 may be pressed. Since the inorganic particles are non-compressible, the current collector 11 corresponding to the insulating layer 14 may be damaged under the action of pressure, causing problems in the cold pressing shear zone. Also, when 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, since the difference in the solid content between the insulating paste and the active paste is too large, when increasing the thickness of the insulating layer 14 by increasing the coating weight (reaching 740 mg / 1540.25 mm 2 (to reach), the insulating layer cannot be completely dried during coating, adheres to the adhesive roll, and problems such as scratches and tape breakage occur on the electrode sheet.

[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 more advantageous for reducing the size of the interaction region.

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

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

[0041] In some embodiments, the coating weight of the active material layer 13 is 427 to 740 mg / 1540.25 mm 2 and the consolidation 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 have an appropriate thickness, which is advantageous for reducing the size of the interaction region. Preferably, the coating weight of the active material layer 13 is 427 to 640 mg / 1540.25 mm 2 is.

[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 manganate and lithium iron phosphate, and the mass ratio of lithium manganate to lithium iron phosphate is 3.5 to 12. The higher the content of lithium manganate, the more gas is generated in the secondary battery. By controlling the mass ratio of lithium manganate to lithium iron phosphate to be 3.5 to 12, the width of the interaction region and the thickness expansion rate after storage of the secondary battery can be made appropriate.

[0044] In some embodiments, 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.

[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, 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, as the negative electrode current collector, any negative electrode current collector known in the art, such as a copper foil, a copper alloy foil, or a composite current collector, can be used. As the negative electrode active material, any negative electrode active material known in the art can be used. 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 include a conductive agent and a binder. The conductive agent includes at least one of conductive carbon black (Super-P), carbon nanotubes (CNTs), carbon fibers, or graphene. Examples of the binder include at least one of styrene butadiene rubber (SBR), polyvinyl alcohol (PVa), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or sodium carboxymethyl cellulose (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 of polyethylene, polypropylene, non-woven fabric, or 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 the solvent, TiPF 6 、TiBF 4 、TiBOB、TiA S F 6 、Ti(CF 3 SO 2 ) 2 N、TiCF 3 SO 3 、TiCTO 4 contains one or more of these lithium salts as the solute.

[0049] The housing may be any housing well-known in the art. For example, the housing may be a packaging bag sealed with a 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 secondary battery. The electronic device may be any power-using equipment using an electrochemical device. For example, the electronic device can be a mobile phone, a portable device, a notebook computer, a battery car, an electric vehicle, a steamship, a spacecraft, an electric toy, and an electric tool, etc.

[0051] In order to better explain the present application, several specific examples and comparative examples are given below. <Example 1> 9.64% lithium iron phosphate, 86.76% lithium manganate (the mass ratio of lithium manganate to lithium iron phosphate is 9), 0.6% conductive carbon paste, 1.2% conductive carbon black and 1.8% polyvinylidene fluoride are dispersed in N-methylpyrrolidone to obtain an active paste with a solid content of 67%. 88% boehmite and 12% polyvinylidene fluoride are dispersed in N-methylpyrrolidone to obtain an insulating paste with a solid content of 35%. The active paste and the insulating paste are applied to an aluminum foil to form an active coating film and an insulating coating film. The active coating film and the insulating coating film are adjacent to each other, and the thickness of the active coating film is equal to the thickness of the insulating coating film. The active coating film and the insulating coating film are dried to obtain an active material layer and an insulating layer. Then, through cold pressing, dicing, and stripping, a positive electrode sheet as shown in Figure 1 is obtained. Here, the coating weight of the active material layer is 427 mg / 1540.25 mm 2 , the consolidation 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 H / T is 0.65.

[0052] After mixing graphite, polyvinylidene fluoride and conductive carbon black, it is applied to a copper foil, and through cold pressing, dicing, and stripping, a negative electrode sheet is obtained.

[0053] The positive electrode sheet, the polyethylene separator and the negative electrode sheet are stacked in sequence, the separator is installed in the middle of the positive electrode sheet and the negative electrode sheet, and wound to obtain an electrode assembly. Next, the electrode assembly is placed in an aluminum-plastic film, injected with electrolyte, and formed 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 coating weight of the active material layer, the thickness T of the active material layer, the consolidation density of the active material layer, the thickness H of the insulating layer, and H / T is different. Among them, 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 that the content of lithium manganate, the content of lithium iron phosphate, and the thickness H of the insulating layer are different.

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

[0057] <Comparative Examples 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 consolidated density of the active material layer, and the thickness H of the insulating layer.

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

[0059] Take the positive electrode sheet, cut the positive electrode sheet horizontally with a dividing cutter, analyze the cross-section using a high-power microscope (SEM), and observe the white insulating layer, the black active material layer, and the 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] Measure the distance from the highest point of the white insulating layer to the current collector using the "dotted line mode", repeat the above steps 3 times, and obtain the thickness H of the insulating layer, which is the average value. Along the width direction of the electrode sheet, move 25 to 35 mm laterally from the edge of the black active material layer toward the back side, take 3 points to measure the distance from the surface of the white active material layer to the current collector, and then obtain the average value, that is, the thickness T of the active material layer.

[0061] Taking the transfer point between the white insulating layer and the gray interaction region as the starting point and the transfer point between the black active material layer and the gray interaction region as the end point along the width direction of the electrode sheet, measure the distance between the two parallel lines, that is, the width of the interaction region, using the "parallel line mode". Repeat the above steps 3 times to obtain the average value, and this average value is the width of the interaction region.

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

[0063] When the width of the interaction region is 0.5 mm or less and the frequency of tape cutting is 20,000 m / time or more, it is determined that it is within the acceptable range of the product and process, and the effect is "OK". In the reverse case, the effect of the interaction region is determined to be "NG".

[0064] Test the high-temperature storage performance of the lithium-ion batteries of Examples 1 to 18 and Comparative Examples 1 to 5.

[0065] Put the lithium-ion battery into an incubator at 25°C and let it stand for 5 minutes to keep the lithium-ion battery at a constant temperature. Charge it to 4.2 V at a constant current of 0.5C and then charge it at a constant voltage until the current reaches 0.05C, and let it stand for 30 minutes. Then, discharge it to 2.8 V at a constant current of 0.2C and let it stand for 5 minutes. As the initial thickness, test and record the thickness of the lithium-ion battery with a micrometer. Transfer the tested lithium-ion battery to an incubator at 60°C and store it for 60 days, then take it out, put it into an incubator at 25°C, and let it stand for 5 minutes to keep the lithium-ion battery at a constant temperature. Measure the thickness of the lithium-ion battery and use it as the thickness after storage.

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

[0067] Show the data and measurement results of Examples 1 to 18 and Comparative Examples 1 to 5 in Table 1.

[0068]

Table 1-1

Table 1-2

Table 1-3

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

[0070] As can be seen from Examples 3 and 12 to 17, when the thicknesses of the active material layer and the insulating layer are within an appropriate range, the influence of the mass ratio of lithium manganate to lithium iron phosphate on the high-temperature storage performance is relatively large. When the mass ratio of lithium manganate to lithium iron phosphate is smaller, the thickness expansion rate after storage is relatively small. When the masses of lithium manganate and lithium iron phosphate are relatively large, the thickness expansion rate after storage is relatively large. Also, as is clear from Example 18, when the positive electrode active material has only lithium iron phosphate, the width of the interaction region becomes large. Further, when the positive electrode active material contains only lithium iron phosphate, the drying 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. Also, because the surface tension of the lithium iron phosphate paste is high, during drying, the edge of the positive electrode active material layer shrinks, and the insulating layer paste further flows into the positive electrode active material layer and penetrates mutually with the positive electrode active material layer to form the intersection width of the interaction region.

[0071] What has been disclosed above is only a preferred embodiment of the present application, and of course, the present application cannot be limited thereby. Therefore, equivalent changes made based on the present application still belong to the scope covered by the present application.

Explanation of Reference Numerals

[0072] 10 Positive electrode sheet 11 Current collector 12 Tab 13 Active material layer 14 Insulating layer 11a First surface 11b second surface

Claims

1. A secondary battery including a positive electrode sheet, wherein the positive electrode sheet includes a current collector, a tab protruding from the current collector, an active material layer provided on at least one surface of the current collector, and an insulating layer provided along a side of the current collector adjacent to the tab and adjacent to the active material layer, wherein a ratio of a thickness of the insulating layer to a 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 secondary battery is characterized by this.

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

7.

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

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

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

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

7. The secondary battery according to claim 1, wherein a tap density of the active material layer is 2.6 to 3 g / cc.

8. The insulating layer contains inorganic particles, and the inorganic particles contain one or more of alumina, boehmite, zirconia, boron oxide, or hexagonal boron nitride. The secondary battery according to claim 1 is characterized by this.

9. The active material layer contains an active material, and the active material contains one or more of lithium nickel cobalt manganese oxide, lithium manganate, lithium iron phosphate, or lithium manganese iron phosphate. The secondary battery according to claim 1 is characterized by this.

10. The active material is composed of the lithium manganate and the lithium iron phosphate, and a mass ratio of the lithium manganate to the lithium iron phosphate is 3.5 to 12. The secondary battery according to claim 9 is characterized by this.

11. The active material is composed of the lithium manganate and the lithium iron phosphate, and a mass ratio of the lithium manganate to the lithium iron phosphate is 3.5 to 9. The secondary battery according to claim 9 is characterized by this.

12. The active material is composed of the lithium manganate and the lithium iron phosphate, and a mass ratio of the lithium manganate to the lithium iron phosphate is 3.5 to 7.

65. The secondary battery according to claim 9 is characterized by this.

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

14. An electronic device, characterized in that it includes the secondary battery according to any one of claims 1 to 13.

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