Secondary battery and electronic device

Abstract

The invention provides a secondary battery and an electronic device. The secondary battery comprises an electrode assembly, the electrode assembly is of a winding structure, the electrode assembly comprises a straight part and a bent part, the electrode assembly comprises an isolating membrane, a positive pole piece and a negative pole piece, the isolating membrane comprises a base material layer and a first coating arranged on at least one surface of the base material layer, and the first coating is located at the bent part of the electrode assembly. The liquid retention amount of the isolating membrane at the straight part is LA g / cm < 2 >, the liquid retention amount of the isolating membrane at the bent part is LB g / cm < 2 >, 1.05 < = LB / LA < = 2, and 0.15 < = LB < = 0.3; the elastic modulus of the separator in the straight portion is EA GPa, the elastic modulus of the separator in the bent portion is EB GPa, 0.5 < = EB / EA < = 0.99, and 0.48 < = EB < = 0.95. The secondary battery provided by the invention has good cycle performance.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a secondary battery and an electronic device. Background Art

[0002] Secondary batteries, such as lithium-ion batteries, are widely used in fields such as smartphones, wearable devices, consumer drones, and electric vehicles due to their advantages such as high energy density, long cycle life, and no memory effect. With the widespread application of lithium-ion batteries in the above-mentioned fields, the market has increasingly higher requirements for the cycle performance of lithium-ion batteries. However, for secondary batteries with a wound structure, the bent portion at the corner usually has problems such as poor electrolyte infiltration and local lack of liquid due to the expansion of the negative electrode plate, which leads to obstructed lithium ion transmission and easily produces interface problems such as black spots and lithium precipitation during the cycle. This is especially serious in lithium-ion battery systems with high expansion (such as silicon-based negative electrode systems) and thin separator thickness at the bent portion, thereby affecting the cycle performance of the lithium-ion battery. Summary of the Invention

[0003] The purpose of this application is to provide a secondary battery and an electronic device to improve the cycle performance of the secondary battery. The specific technical solution is as follows:

[0004] The first aspect of the present application provides a secondary battery, which includes an electrode assembly, the electrode assembly is a wound structure, the electrode assembly includes a straight portion and a curved portion, the electrode assembly includes a separator, a positive electrode sheet and a negative electrode sheet, the separator includes a substrate layer and a first coating provided on at least one surface of the substrate layer, the first coating is located in the curved portion of the electrode assembly, and the liquid retention capacity of the separator in the straight portion is L A g / cm 2 , the liquid holding capacity of the isolation diaphragm at the bend is L B g / cm 2 , 1.05≤L B / L A ≤2, 0.15≤L B ≤0.3; the elastic modulus of the isolation diaphragm in the straight part is E A GPa, the elastic modulus of the isolation diaphragm at the bend is E B GPa, 0.5≤E B / E A ≤0.99, 0.48≤E B ≤0.95. This application designs the isolation membrane structure in the wound structure secondary battery so that L B / L A 、L B 、E B / E A 、E BThe value is within the scope of this application. When the volume of the negative electrode sheet expands during the charging process of the secondary battery, the isolation membrane located at the bent portion is squeezed and deformed to release the stored electrolyte, replenish the electrolyte missing in the bent portion, and buffer the expansion and deformation of the negative electrode sheet at the bent portion, reducing the volume expansion of the secondary battery, thereby improving the interface problems such as black spots and lithium plating that appear during the cycle of the secondary battery and improving the cycle performance of the secondary battery.

[0005] In some embodiments of the present application, the secondary battery satisfies at least one of the following characteristics: (1) 1.14≤L B / L A ≤1.78;(2)0.17≤L B ≤0.27; (3) 0.67≤E B / E A ≤0.93; (4) 0.65≤E B ≤0.89. Secondary batteries that meet the above characteristics are conducive to improving interface problems such as black spots and lithium deposition that occur during the cycle of secondary batteries, thereby improving the cycle performance of secondary batteries.

[0006] In some embodiments of the present application, the porosity of the isolation film in the straight portion is P A %, the porosity of the separator in the curved part is P B %, 1.05≤P B / P A ≤1.25,65≤P B ≤95. By regulating P B / P A 、P B The value of within the above range is beneficial to reducing the probability of liquid shortage in the bend during the cycle, increasing the transmission channel of lithium ions in the separator of the bend, and improving the transmission rate of lithium ions in the separator, thereby helping to improve the interface problems such as black spots and lithium deposition that appear in the secondary battery during the cycle, and improving the cycle performance of the secondary battery.

[0007] In some embodiments of the present application, 1.07≤P B / P A ≤1.21,80≤P B ≤91. By regulating P B / P A 、P B The value of within the above range is beneficial to further improve the interface problems such as black spots and lithium deposition that occur in the secondary battery during the cycle process, and improve the cycle performance of the secondary battery.

[0008] In some embodiments of the present application, the first coating layer includes an elastic material, and the weight percentage of the elastic material is 50% to 95% based on the weight of the first coating layer. By regulating the weight percentage of the elastic material within the above range, the first coating layer is effectively utilized to improve the interfacial issues such as black spots and lithium deposition that occur during the cycling of the secondary battery, thereby improving the cycling performance of the secondary battery.

[0009] In some embodiments of the present application, the elastic material includes at least one of a metal organic framework material or a porous elastic polymer, the metal organic framework material includes at least one of ZIF-8, MIL-53, MOF-74, PCN-224, UiO-66, MOF-801, MOF-200, MOF-888, MOF-767, MOF-808, MOF-253, MOF-199, MOF-505, MOF-740, MOF-841, MOF-525, MOF-210, MOF-800, MOF-701 or MOF-820, and the porous elastic polymer includes at least one of porous polyurethane, porous silicone rubber, porous polyvinyl alcohol, porous sodium polyacrylate, porous polyacrylate or porous polyacrylonitrile. The selection of the above elastic materials is conducive to improving the interface problems such as black spots and lithium precipitation that appear in the secondary battery during the cycle process, thereby improving the cycle performance of the secondary battery.

[0010] In some embodiments of the present application, the elastic material has a Dv50 value of 150 nm to 750 nm. By regulating the Dv50 value of the elastic material within this range, the fluid retention and elastic modulus of the curved separator are maintained within the ranges of the present application, thereby improving interfacial issues such as black spots and lithium deposition that may occur during the cycling of the secondary battery and enhancing the cycling performance of the secondary battery.

[0011] In some embodiments of the present application, the thickness of the first coating layer is H C μm, the thickness of the isolation film is H S μm, 0.5≤H C ≤2.5,0.05≤H C / H S ≤0.25. By adjusting H C 、H C / H S The value of within the above range is conducive to the role of the first coating layer. At the same time, the energy density of the secondary battery is high, which is conducive to improving the interface problems such as black spots and lithium deposition that occur during the cycle of the secondary battery and improving the cycle performance of the secondary battery.

[0012] In some embodiments of the present application, the first coating layer further comprises a first binder, the weight percentage of the first binder being 5% to 50% based on the weight of the first coating layer; the first binder comprises at least one of polyacrylic acid, polyacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, or polyvinylidene fluoride. Selecting such a first binder and regulating its weight percentage within the aforementioned range can help alleviate interfacial issues such as black spots and lithium deposition that may occur during the cycling of the secondary battery, thereby improving the cycling performance of the secondary battery.

[0013] In some embodiments of the present application, the secondary battery satisfies at least one of the following characteristics: (1) the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector, and the thickness of the positive electrode material layer is H P μm, 40≤H P ≤200; (2) The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector, and the thickness of the negative electrode material layer is H N μm, 25≤H N ≤100. Secondary batteries that meet the above characteristics are conducive to improving interface problems such as black spots and lithium deposition that occur during the cycle of secondary batteries, improving the cycle performance of secondary batteries, and at the same time, the energy density of secondary batteries is relatively high.

[0014] In some embodiments of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The negative electrode material layer includes a negative electrode active material, which includes a silicon-containing material. The silicon-containing material includes at least one of a silicon-carbon composite material, a silicon-oxygen composite material, or elemental silicon. The selection of such negative electrode active materials is beneficial for improving the energy density of the secondary battery, while also reducing the probability of interfacial issues such as black spots and lithium deposition during cycling, and achieving good cycling performance.

[0015] The second aspect of the present application provides an electronic device, which includes the secondary battery provided by the first aspect of the present application. The electronic device of the present application has a long service life and good performance.

[0016] Beneficial effects of this application:

[0017] The present application provides a secondary battery and an electronic device. The secondary battery includes an electrode assembly, which is a wound structure. The electrode assembly includes a straight portion and a curved portion. The electrode assembly includes a separator, a positive electrode sheet, and a negative electrode sheet. The separator includes a substrate layer and a first coating provided on at least one surface of the substrate layer. The first coating is located in the curved portion of the electrode assembly. The liquid retention capacity of the separator in the straight portion is L A g / cm 2 , the liquid holding capacity of the isolation diaphragm at the bend is L B g / cm2 , 1.05≤L B / L A ≤2, 0.15≤L B ≤0.3; the elastic modulus of the isolation diaphragm in the straight part is E A GPa, the elastic modulus of the isolation diaphragm at the bend is E B GPa, 0.5≤E B / E A ≤0.99, 0.48≤E B ≤0.95. This application designs the isolation membrane structure in the wound structure secondary battery so that L B / L A 、L B 、E B / E A 、E B The value is within the scope of this application. When the volume of the negative electrode sheet expands during the charging process of the secondary battery, the isolation membrane located at the bent portion is squeezed and deformed to release the stored electrolyte, replenish the electrolyte missing in the bent portion, and buffer the expansion and deformation of the negative electrode sheet at the bent portion, reducing the volume expansion of the secondary battery, thereby improving the interface problems such as black spots and lithium plating that appear during the cycle of the secondary battery and improving the cycle performance of the secondary battery.

[0018] Of course, it is not necessary to achieve all the advantages described above at the same time when implementing any product or method of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0020] Figure 1 This is a schematic diagram of the structure of the isolation membrane in the electrode assembly according to one embodiment of the present application.

[0021] Reference numerals: separator 10 , substrate layer 11 , first coating layer 12 , second coating layer 13 , curved portion 14 , straight portion 15 . DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present application and the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the embodiments described are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0023] It should be noted that, in the specific embodiments of the present application, lithium-ion batteries are used as an example of secondary batteries to explain the present application, but the secondary batteries of the present application are not limited to lithium-ion batteries.

[0024] For secondary batteries with a wound structure, the curved sections at the corners often suffer from poor electrolyte infiltration and localized electrolyte shortages due to the expansion of the negative electrode. This hinders the transmission of lithium ions and easily causes interfacial problems such as black spots and lithium deposition during the cycle, resulting in poor cycling performance of the secondary battery. Currently, increasing the thickness of the separator at the curved section can improve these problems, but this affects the energy density of the secondary battery and worsens its kinetic performance. While secondary batteries with a laminated structure can avoid interfacial problems such as black spots and lithium deposition at the curved section due to the lack of curved sections, the production cost of laminated secondary batteries is high and the process is complex.

[0025] Based on this, the first aspect of the present application provides a secondary battery, which includes an electrode assembly, the electrode assembly is a winding structure, the electrode assembly includes a straight portion and a curved portion, the electrode assembly includes a separator, a positive electrode sheet and a negative electrode sheet, the separator includes a substrate layer and a first coating provided on at least one surface of the substrate layer, the first coating is located in the curved portion of the electrode assembly, and the liquid retention capacity of the separator in the straight portion is L A g / cm 2 , the liquid holding capacity of the isolation diaphragm at the bend is L B g / cm 2 , 1.05≤L B / L A ≤2, 0.15≤L B ≤0.3, preferably, 1.14≤L B / L A ≤1.78,0.17≤L B ≤0.27; the elastic modulus of the isolation diaphragm in the straight part is E A GPa, the elastic modulus of the isolation diaphragm at the bend is E B GPa, 0.5≤E B / E A ≤0.99, 0.48≤E B ≤0.95, preferably 0.67≤E B / E A ≤0.93, 0.65≤E B ≤0.89. In the present application, the above-mentioned “first coating layer provided on at least one surface of the substrate layer” means that the first coating layer can be provided on one surface of the substrate layer along its thickness direction, or on both surfaces of the substrate layer along its thickness direction, and the first coating layer can be provided directly on the surface of the substrate layer, or on the surface of other functional coatings on the surface of the substrate layer.

[0026] For example, L B / L A The value of can be 1.05, 1.1, 1.14, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.78, 1.8, 1.9, 2.0 or a range consisting of any two values therein; B The value of can be 0.15, 0.17, 0.18, 0.20, 0.22, 0.24, 0.25, 0.26, 0.27, 0.28, 0.30 or a range consisting of any two values therein. B / E A The value of can be 0.50, 0.55, 0.60, 0.65, 0.67, 0.70, 0.75, 0.80, 0.85, 0.90, 0.93, 0.95, 0.99 or a range consisting of any two values therein; B The value of can be 0.48, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.89, 0.90, 0.95 or a range consisting of any two values therein.

[0027] The present invention designs the isolation membrane structure in the wound structure secondary battery so that the isolation membrane located at the curved portion has a larger liquid retention capacity and a smaller elastic modulus than that located at the straight portion, and regulates the L B / L A 、L B 、E B / E A 、E BThe value is within the scope of this application. When the volume of the negative electrode sheet expands during the charging process of the secondary battery, the isolation membrane located at the curved part is squeezed and deformed to release the stored electrolyte, replenish the electrolyte missing in the curved part, reduce the probability of liquid shortage in the curved part during the cycle, improve the uniformity of lithium insertion in the negative electrode sheet of the curved part, and also help to increase the transmission channel of lithium ions in the isolation membrane of the curved part, improve the transmission rate of lithium ions in the isolation membrane, and help to improve the electrolyte wettability of the positive and negative electrode sheets. In addition, the isolation membranes of the curved and straight parts have high mechanical strength and good mechanical properties, and the risk of isolation membrane breakage during the cycle of the secondary battery is low. The separator, with a relatively small elastic modulus in the curved portion, can also buffer the expansion and deformation of the negative electrode tab in the curved portion, reducing the volume expansion of the secondary battery. At the same time, the deformation of the first coating layer is moderate when squeezed, reducing the risk of coating shedding on the curved and straight portions of the separator. The risk of local shorting between the positive and negative electrode tabs due to the reduced thickness of the separator when deformed is also low. This can improve interfacial issues such as black spots and lithium deposition that occur during the cycling of the secondary battery, especially in the curved portion, and enhance the cycling performance of the secondary battery. Furthermore, placing the first coating layer in the curved portion can reduce the use of the more expensive first coating layer, reducing the production cost of the secondary battery.

[0028] When L B / L A If the value of is too small, for example, less than 1.05, the liquid retention of the separator in the curved part and the straight part does not match, and the liquid retention of the separator in the curved part is relatively small. The pressure on the curved part of the electrode assembly is greater than that on the straight part, resulting in the electrolyte being squeezed out of the curved part, insufficient liquid retention in the curved part, and localized liquid shortage. As a result, black spots and lithium precipitation in the curved part are more serious, which is not conducive to improving the cycle performance of the secondary battery. B / L A When the value of is too large, for example, greater than 2, the liquid retention of the separator in the curved part and the straight part does not match. Although the liquid retention of the separator in the curved part is larger, the porosity of the separator in the curved part is also relatively large, resulting in low local mechanical strength. During the cycle of the secondary battery, the separator in the curved part is easy to break, affecting the safety performance of the secondary battery and not conducive to improving the cycle performance of the secondary battery. When L B If the value of is too small, for example, less than 0.15, the bent part will not be able to retain enough liquid, and local liquid shortage will occur, which will lead to serious interface problems such as black spots and lithium deposition in the bent part, which is not conducive to improving the cycle performance of the secondary battery. B When the value is too large, for example greater than 0.3, although the liquid retention capacity of the bend separator is large, the porosity of the bend separator is also relatively large, resulting in low local mechanical strength and easy breakage of the bend separator, which affects the safety performance of the secondary battery and is not conducive to improving the cycle performance of the secondary battery.

[0029] When E B / EA If the value of is too small, for example, less than 0.5, the elastic modulus of the separator of the curved part and the straight part do not match, the elastic modulus of the separator of the curved part is low, and the mechanical strength is low. When the separator of the curved part is squeezed, the deformation of the first coating is large, and it extends more along the length and width of the separator, which can easily cause the straight part coating to fall off. At the same time, the thickness of the separator of the curved part is reduced too much, which can easily cause local short circuit of the positive and negative electrodes, thereby affecting the safety performance and cycle performance of the secondary battery. When E B / E A When the value of is too large, for example, greater than 0.99, the elastic modulus of the separator at the bend is large. When the separator at the bend is squeezed, the deformation is too small, which is not conducive to releasing the electrolyte stored inside and replenishing it to the liquid-deficient area at the bend. The bend of the electrode assembly is prone to liquid deficiency, and interface problems such as black spots and lithium deposition are more serious. At the same time, it is also unable to buffer the expansion and deformation of the negative electrode sheet at the bend, which is not conducive to improving the cycle performance of the secondary battery. When E B If the value of is too small, for example, less than 0.48, the elastic modulus of the bend separator is low, the mechanical strength is low, and when the bend separator is squeezed, the deformation is too large. The thickness of the bend separator is low, which can easily lead to local short circuit of the positive and negative electrodes, thereby affecting the safety and cycle performance of the secondary battery. B When the value is too large, for example greater than 0.95, the elastic modulus of the separator at the bend is too large. When the separator at the bend is squeezed, the deformation is too small, which is not conducive to releasing the electrolyte stored inside and replenishing it to the liquid-deficient area at the bend. The bend of the electrode assembly is prone to liquid deficiency, and interface problems such as black spots and lithium deposition are more serious. At the same time, it is also unable to buffer the expansion and deformation of the negative electrode sheet at the bend, which is not conducive to improving the cycle performance of the secondary battery.

[0030] Therefore, the present invention designs the isolation membrane structure in the wound structure secondary battery so that L B / L A 、L B 、E B / E A 、E B The value of is within the scope of this application, which can improve the interface problems such as black spots and lithium deposition that occur in the secondary battery during the cycle process, improve the cycle performance of the secondary battery, and at the same time have a low preparation cost.

[0031] In the present application, the positive electrode sheet, the separator and the negative electrode sheet are wound to form an electrode assembly of a wound structure, and the electrode assembly includes a curved portion and a straight portion. The curved portion refers to the curved portion formed by the positive electrode sheet, the separator and the negative electrode sheet during the winding process, and the straight portion refers to the straight portion formed by the positive electrode sheet, the separator and the negative electrode sheet during the winding process. For example, the winding direction of the electrode assembly is defined as W, the width direction is defined as X, and the thickness direction is defined as Y. It should be understood that the above definition of direction is for the convenience of describing the purpose of this application. Figure 1 As shown, the separator 10 in the electrode assembly includes a substrate layer 11 and a first coating layer 12 and a second coating layer 13 provided on both surfaces of the substrate layer 11. The first coating layer 12 is located at a curved portion 14 of the electrode assembly, and the second coating layer 13 is located at a straight portion 15 of the electrode assembly.

[0032] In some embodiments, 0.075≤L A ≤0.29. For example, L A The value of can be 0.075, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, 0.29 or a range consisting of any two values therein.

[0033] In some embodiments, 0.48≤E A ≤1.9. For example, E A The value of can be 0.48, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or a range consisting of any two values therein.

[0034] In some embodiments of the present application, the porosity of the isolation film in the straight portion is P A %, the porosity of the separator in the curved part is P B %, 1.05≤P B / P A ≤1.25,65≤P B ≤95, preferably, 1.07≤P B / P A ≤1.21,80≤P B ≤91. For example, P B / P A The value of can be 1.05, 1.07, 1.08, 1.10, 1.12, 1.15, 1.18, 1.20, 1.21, 1.22, 1.25 or a range consisting of any two values therein; B The value of can be 65, 68, 70, 72, 75, 78, 80, 82, 85, 88, 90, 91, 92, 95 or a range consisting of any two of them. B / P A 、P BWhen the value of is within the above range, the storage space for the electrolyte in the separator of the curved part is larger, and there are more transmission channels for lithium ions. When the volume of the negative electrode sheet expands during the charging process of the secondary battery, the separator located at the curved part is squeezed to release more electrolyte, which is supplemented to the area where the electrolyte is lacking in the curved part, thereby reducing the probability of liquid shortage in the curved part during the cycle, and is also beneficial to increasing the transmission rate of lithium ions in the separator. At the same time, the separator has high mechanical strength and good mechanical properties, and the risk of fracture during the cycle of the secondary battery is low, which is beneficial to improving the interface problems such as black spots and lithium plating that appear in the cycle of the secondary battery, and improving the cycle performance of the secondary battery.

[0035] In some embodiments, 52≤P A ≤90.5. For example, P A The value of can be 52, 55, 58, 60, 62, 65, 68, 70, 72, 75, 78, 80, 82, 85, 88, 90.5 or a range consisting of any two values therein.

[0036] In some embodiments of the present application, the first coating layer includes an elastic material, and the mass percentage of the elastic material is 50% to 95% based on the mass of the first coating layer. For example, the mass percentage of the elastic material can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or a range consisting of any two of these values. By regulating the mass percentage of the elastic material within the above range, it is beneficial to make the liquid retention and elastic modulus of the bending portion isolation membrane within the scope of this application, play the role of the first coating layer, reduce the probability of liquid shortage in the bending portion during the cycle, increase the transmission channel of lithium ions in the bending portion isolation membrane, increase the transmission rate of lithium ions in the isolation membrane, and also help to buffer the expansion and deformation of the negative electrode sheet of the bending portion, reduce the volume expansion of the secondary battery, thereby helping to improve the interface problems such as black spots and lithium precipitation that appear in the secondary battery during the cycle, and improve the cycle performance of the secondary battery.

[0037] The elastic material of the present application is applied to the first coating to enable L B / L A 、L B 、E B / E A 、E BThe value of is within the scope of this application. In some embodiments of the present application, the elastic material includes at least one of a metal organic framework (MOF) material or a porous elastic polymer, wherein the metal organic framework (MOF) material is a crystalline material with a porous structure formed by self-assembly of metal ions or metal clusters and organic ligands. The above-mentioned metal organic framework material includes at least one of ZIF-8, MIL-53, MOF-74, PCN-224, UiO-66, MOF-801, MOF-200, MOF-888, MOF-767, MOF-808, MOF-253, MOF-199, MOF-505, MOF-740, MOF-841, MOF-525, MOF-210, MOF-800, MOF-701 or MOF-820, and the specific composition and chemical formula are shown in Table 1. The porous elastic polymer includes at least one of porous polyurethane, porous silicone rubber, porous polyvinyl alcohol, porous sodium polyacrylate, porous polyacrylate, or porous polyacrylonitrile. The use of these elastic materials can help alleviate interfacial issues such as black spots and lithium deposition that can occur during the cycling of secondary batteries, thereby improving the cycling performance of the secondary batteries.

[0038] Table 1

[0039]

[0040]

[0041] In some embodiments of the present application, the Dv50 of the elastic material is 150nm to 750nm. For example, the Dv50 of the elastic material can be 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm or a range consisting of any two of these values. By regulating the Dv50 of the elastic material within the above range, it is beneficial to make the liquid retention and elastic modulus of the bending portion isolation membrane within the scope of this application, reduce the probability of liquid shortage in the bending portion during the cycle, buffer the expansion deformation of the negative electrode sheet of the bending portion, reduce the volume expansion of the secondary battery, and at the same time reduce the probability of agglomeration of the elastic material during the preparation process, so that the components in the first coating are evenly distributed, improve the processing performance of the isolation membrane, and reduce the preparation cost of the isolation membrane, thereby helping to improve the interface problems such as black spots and lithium precipitation that appear in the secondary battery during the cycle, and improve the cycle performance of the secondary battery. In this application, Dv50 refers to the particle size at which the volume accumulation reaches 50% from the smallest particle size in the volume-based particle size distribution of the material.

[0042] In some embodiments of the present application, the thickness of the first coating layer is H C μm, the thickness of the isolation film is HS μm, 0.5≤H C ≤2.5,0.05≤H C / H S ≤0.25. For example, H C The value of can be 0.5, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0, 2.2, 2.5 or a range consisting of any two values therein. C / H S The value of can be 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25 or a range consisting of any two of these values. C 、H C / H S The value of is within the above range, which is conducive to the role of the first coating, so that the liquid retention capacity and elastic modulus of the bending portion isolation membrane are within the scope of this application, and is also conducive to the transmission of lithium ions in the isolation membrane. At the same time, the energy density of the secondary battery is high, the mechanical strength of the isolation membrane is high, and the risk of breakage during the secondary battery cycle is low. The risk of local short circuit between the positive electrode sheet and the negative electrode sheet is also low, which is conducive to improving the interface problems such as black spots and lithium plating that appear in the secondary battery cycle, and improving the cycle performance of the secondary battery.

[0043] In some embodiments, 2≤H S ≤20. For example, H S The value of can be 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 or a range consisting of any two values therein.

[0044] In some embodiments of the present application, the first coating layer also includes a first binder, and the mass percentage of the first binder is 5% to 50% based on the mass of the first coating layer. For example, the mass percentage of the first binder can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or a range consisting of any two of these values. By regulating the mass percentage of the first binder within the above range, it is beneficial to play the role of the first coating layer, so that the liquid retention and elastic modulus of the bending portion isolation membrane are within the scope of this application, and it is also beneficial to reduce the risk of the first coating layer falling off during the cycle, thereby helping to improve the interface problems such as black spots and lithium precipitation that appear in the secondary battery during the cycle, and improving the cycle performance of the secondary battery.

[0045] In some embodiments of the present application, the first binder includes at least one of polyacrylic acid, polyacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, or polyvinylidene fluoride. Selecting such a first binder can help alleviate interfacial issues such as black spots and lithium deposition that may occur during the cycling of the secondary battery, thereby improving the cycling performance of the secondary battery.

[0046] In some embodiments, the separator includes a substrate layer and a second coating disposed on at least one surface of the substrate layer, the second coating being located on the flat portion of the electrode assembly, and the second coating may be at least one of an inorganic layer, a polymer layer, or a solid electrolyte layer.

[0047] In some embodiments, the inorganic layer includes ceramic particles and an inorganic layer binder. The application is not particularly limited to ceramic particles. For example, ceramic particles can include but are not limited to at least one of silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. The application is not particularly limited to inorganic layer binders. For example, inorganic layer binders can include but are not limited to at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber or polyvinylidene fluoride. In some embodiments, the polymer layer includes a polymer, and the material of the polymer can include but is not limited to at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene). In some embodiments, the solid electrolyte layer includes a solid electrolyte, which may include but is not limited to at least one of an oxide solid electrolyte, a sulfide solid electrolyte, or a polymer solid electrolyte. The oxide solid electrolyte may include but is not limited to at least one of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLTO), lithium aluminum germanium phosphate (LAGP), or lithium phosphorus oxynitride (LiPON). The sulfide solid electrolyte may include but is not limited to Li 10 GeP2S 12 (LGPS type), Li6PS5X (X=Cl, Br, I) or Li2S-P2S5 system, the polymer solid electrolyte may include but is not limited to at least one of polyethylene oxide (PEO), polyacrylonitrile, polymethyl methacrylate, polyvinyl chloride or polyvinylidene fluoride.

[0048] In some embodiments, the thickness of the second coating is H T μm, the thickness of the isolation film is H S μm, 0.5≤H T ≤2.5,0.05≤H T / H S ≤0.25. For example, H T The value of can be 0.5, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0, 2.2, 2.5 or a range consisting of any two values therein.T / H S The value of can be 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, or a range consisting of any two of these values. In some embodiments, the thickness of the first coating layer is the same as that of the second coating layer.

[0049] The present application does not particularly limit the separator substrate layer, as long as the purpose of the present application can be achieved. For example, the substrate layer can be a non-woven fabric or composite film having a porous structure, and the material of the substrate layer can include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.

[0050] The present application does not impose any particular restrictions on the method for preparing the isolation membrane, as long as the purpose of the present application can be achieved. For example, the preparation of the isolation membrane may include but is not limited to the following steps: dividing the substrate layer into a curved portion and a straight portion according to the position of the isolation membrane in the electrode assembly after winding. Evenly mixing the elastic material and the first binder to obtain a first coating slurry. Prepare a second coating slurry. Evenly apply the first coating slurry on one surface of the curved portion of the substrate layer, and evenly apply the second coating slurry on one surface of the straight portion of the substrate layer, and dry them to obtain the first coating and the second coating. Then repeat the above steps on the other surface of the substrate layer to obtain an isolation membrane with the first coating and the second coating provided on both sides.

[0051] In the present application, elastic materials with different Dv50 values can be obtained by mechanical crushing (e.g., ball milling). For example, the Dv50 value of the elastic material can be controlled by regulating the ball milling time. When other conditions remain unchanged, a longer ball milling time decreases the Dv50 value of the elastic material; a shorter ball milling time increases the Dv50 value of the elastic material.

[0052] In this application, L can be controlled by adjusting the porosity of the substrate layer. A Value, P A For example, when other conditions remain unchanged, the porosity of the substrate layer increases, L A The value increases, P A The value increases; the porosity of the substrate layer decreases, L A The value decreases, P A The composition of the second coating also affects L A Value, E A Value, P A value.

[0053] In this application, L can be controlled by adjusting the Dv50 of the elastic material and the mass percentage of the elastic material in the first coating. BValue, E B Value, P B For example, when other conditions remain unchanged, the Dv50 of the elastic material increases, L B The value increases, E B The value decreases, P B The value increases; the Dv50 of the elastic material decreases, L B The value decreases, E B The value increases, P B When other conditions remain unchanged, the mass percentage of the elastic material in the first coating increases, L B The value increases, E B The value decreases, P B The value increases; the mass percentage of the elastic material in the first coating decreases, L B The value decreases, E B The value increases, P B The type of elastic material also affects L B Value, E B Value, P B L can be controlled by adjusting the porosity of the substrate layer. B Value, P B When other conditions remain unchanged, the porosity of the substrate layer increases, L B The value increases, P B The value increases; the porosity of the substrate layer decreases, L B The value decreases, P B It is understood that L can also be adjusted by adjusting the coating quality of the first coating on the surface of the curved portion of the substrate layer. B The above coating quality can be adjusted by adjusting the coating thickness and / or coating area of the first coating layer.

[0054] In this application, H can be adjusted by adjusting the coating surface density and compaction density of the first coating. C For example, when other conditions remain unchanged, the coating surface density of the first coating increases, H C Increase; the coating surface density of the first coating decreases, H C When other conditions remain unchanged, the compaction density of the first coating increases, H C Decreases; the compaction density of the first coating decreases, H C Increase.

[0055] In some embodiments of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector, and the thickness of the positive electrode material layer is H. P μm, 40≤H P ≤200. For example, H PThe value of can be 40, 60, 80, 100, 120, 140, 160, 180, 200 or a range consisting of any two of these values. P The value of is within the above range, which can increase the volume proportion of the positive electrode active material in the electrode assembly and improve the energy density of the secondary battery. At the same time, when used with the isolation membrane of the present application, the isolation membrane of the curved portion can store more electrolyte, which is more conducive to reducing the probability of liquid shortage in the curved portion during the cycle, improving the electrolyte wettability of the positive electrode sheet, and buffering the expansion of the positive electrode sheet, thereby helping to improve the interface problems such as black spots and lithium plating that appear in the secondary battery during the cycle, and improving the cycle performance and energy density of the secondary battery.

[0056] In this application, the H can be controlled by adjusting the coating surface density and compaction density of the positive electrode material layer. P For example, when other conditions remain unchanged, the coating surface density of the positive electrode material layer increases, H P Increase; the coating surface density of the positive electrode material layer decreases, H P When other conditions remain unchanged, the compaction density of the positive electrode material layer increases, H P Decreases; the compaction density of the positive electrode material layer decreases, H P Increase.

[0057] In some embodiments of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, and the thickness of the negative electrode material layer is H. N μm, 25≤H N ≤100. For example, H N The value of can be 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 or a range consisting of any two of them. N The value of is within the above range, which can increase the volume proportion of the negative electrode active material in the electrode assembly and improve the energy density of the secondary battery. At the same time, when used with the isolation membrane of the present application, the isolation membrane of the curved portion can store more electrolyte, which is more conducive to reducing the probability of liquid shortage in the curved portion during the cycle, improving the electrolyte wettability of the negative electrode sheet, and buffering the expansion of the negative electrode sheet, thereby helping to improve the interface problems such as black spots and lithium plating that appear in the secondary battery during the cycle, and improving the cycle performance and energy density of the secondary battery.

[0058] In this application, the H can be controlled by adjusting the coating surface density and compaction density of the negative electrode material layer. N For example, when other conditions remain unchanged, the coating surface density of the negative electrode material layer increases, H N Increase; the coating surface density of the negative electrode material layer decreases, H Ndecreases. When other conditions remain unchanged, as the compaction density of the negative electrode material layer increases, H N decreases; as the compaction density of the negative electrode material layer decreases, H N increases.

[0059] In some embodiments of the present application, the negative electrode tab includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The negative electrode material layer includes a negative electrode active material, the negative electrode active material includes a silicon-containing material, and the silicon-containing material includes at least one of a silicon-carbon composite material, a silicon-oxygen composite material (SiOx(0 < x ≤ 2)), or elemental silicon. The mass ratio of silicon element to carbon element in the silicon-carbon composite material can be 1:(0.4 to 3). Selecting the above negative electrode active material is beneficial to improving the energy density of the secondary battery, and at the same time, the probability of interface problems such as black spots and lithium deposition during the cycling process is relatively low, and the cycling performance is good.

[0060] In some embodiments, based on the mass of the negative electrode active material, the mass percentage content of the silicon-containing material is 5% to 100%. For example, the mass percentage content of the silicon-containing material can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, 80%, 90%, 100%, or a range composed of any two of these values.

[0061] In some embodiments, the negative electrode active material further includes a negative electrode active material other than the silicon-containing material. Based on the mass of the negative electrode active material, the mass percentage content of the negative electrode active material other than the silicon-containing material is 0% to 95%. For example, the mass percentage content of the negative electrode active material other than the silicon-containing material can be 0%, 10%, 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, 80%, 90%, 95%, or a range composed of any two of these values. The present application does not particularly limit the type of the negative electrode active material other than the silicon-containing material, as long as the object of the present application can be achieved. For example, the negative electrode active material other than the silicon-containing material may include at least one of natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithium titanate Li4Ti5O 12 , Li-Al alloy, or metallic lithium.

[0062] In the present application, the electrode assembly includes a positive electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector. The above-mentioned "positive electrode material layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be disposed on one surface of the positive electrode current collector along its own thickness direction, or on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of the positive electrode current collector or a partial area of the positive electrode current collector. This application is not particularly limited, as long as the purpose of this application can be achieved.

[0063] The present application has no particular restrictions on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, it can include aluminum foil, aluminum alloy foil, or a composite current collector (such as an aluminum-carbon composite current collector). The present application has no particular restrictions on the thickness of the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector can be 6μm to 25μm.

[0064] The positive electrode material layer of the present application includes a positive electrode active material, and the positive electrode active material includes a substance that can reversibly embed and extract active ions such as lithium ions. The positive electrode material layer can be one layer or more layers, and each layer in the multilayer positive electrode material layer can contain the same or different positive electrode active materials. The present application has no special restrictions on the positive electrode active material, as long as the purpose of the present application can be achieved. For example, the positive electrode active material may include but is not limited to lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium iron manganese phosphate or lithium titanate. The above-mentioned lithium nickel cobalt manganese oxide may include LiNi 0.95 Co 0.03 Mn 0.02 O2(Ni95),LiNi 0.91 Co 0.03 Mn 0.06 O2(Ni91), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622),LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523) or LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 At least one of O2 (NCM111).

[0065] The positive electrode material layer of the present application also includes a positive electrode conductor and a positive electrode binder. The present application has no particular restrictions on the positive electrode conductor and the positive electrode binder in the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the positive electrode conductor may include but is not limited to at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metal materials or conductive polymers, and the conductive carbon black may include but is not limited to at least one of acetylene black or Ketjen black. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and / or nano-carbon fibers. The above-mentioned metal materials may include but are not limited to metal powder and / or metal fibers, specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver. The above-mentioned conductive polymers may include but are not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. For example, the positive electrode binder may include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber, or polyvinylidene fluoride. The present application does not particularly limit the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder in the positive electrode material layer. Those skilled in the art may select the ratio according to actual needs, as long as the purpose of the present application can be achieved.

[0066] Optionally, the positive electrode sheet may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode material layer. This application does not particularly limit the composition of the conductive layer, and it can be a conductive layer commonly used in the art. For example, the conductive layer includes a conductive layer conductive agent and a conductive layer binder. This application does not particularly limit the conductive layer conductive agent and the conductive layer binder in the conductive layer. For example, the conductive layer conductive agent can be at least one of the above-mentioned positive electrode conductive agents, and the conductive layer binder can be at least one of the above-mentioned positive electrode binders.

[0067] In the present application, the electrode assembly includes a negative electrode plate. The negative electrode plate includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The above-mentioned "negative electrode material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its own thickness direction, or on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of the surface of the negative electrode current collector, or it can be a partial area of the surface of the negative electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved.

[0068] The present application does not particularly limit the negative electrode current collector, as long as it can achieve the purpose of this application. For example, it can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a composite current collector. For example, the composite current collector can be a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, or a titanium-copper composite current collector. The present application does not particularly limit the thickness of the negative electrode current collector, as long as it can achieve the purpose of this application. For example, the thickness of the negative electrode current collector can be 4μm to 15μm.

[0069] The negative electrode material layer of the present application may further include a negative electrode conductive agent and a negative electrode binder. For example, the negative electrode conductive agent may be at least one of the above-mentioned positive electrode conductive agents, and the negative electrode binder may be at least one of the above-mentioned positive electrode binders. The present application does not particularly limit the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder in the negative electrode material layer. Those skilled in the art may select the ratio based on actual needs, as long as the purpose of the present application can be achieved.

[0070] Optionally, the negative electrode plate may further include a conductive layer, which is positioned between the negative electrode current collector and the negative electrode material layer. This application does not particularly limit the composition of the conductive layer, and it may be any conductive layer commonly used in the art. For example, the conductive layer may include a conductive agent and a conductive binder. This application does not particularly limit the conductive agent and the conductive binder in the conductive layer. For example, the conductive agent may be at least one of the above-mentioned positive electrode conductive agents, and the conductive binder may be at least one of the above-mentioned positive electrode binders.

[0071] In the present application, the secondary battery further includes an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent.

[0072] The present application does not specifically limit the lithium salt, as long as the objectives of the present application can be achieved. For example, the lithium salt may include, but is not limited to, at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalatoborate) (LiBOB), or lithium difluoroborate. The present application does not specifically limit the content of the lithium salt in the electrolyte, as long as the objectives of the present application can be achieved.

[0073] The present application has no particular limitation on the non-aqueous solvent, as long as the purpose of the present application can be achieved. For example, the non-aqueous solvent may include but is not limited to at least one of carbonate compounds, carboxylate compounds, ether compounds or other organic solvents.

[0074] Above-mentioned carbonate compound can include but not limited to at least one in linear carbonate compound, cyclic carbonate compound or fluorinated carbonate compound.Above-mentioned linear carbonate compound can include but not limited to at least one in dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC) or methyl ethyl carbonate (MEC).Above-mentioned cyclic carbonate compound can include but not limited to at least one in ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or vinyl ethylene carbonate (VEC). The fluorocarbonate compound may include, but is not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The carboxylate compound may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerolactone, or caprolactone. The above-mentioned ether compound may include but is not limited to at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran. The above-mentioned other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate or trioctyl phosphate. The present application does not particularly limit the content of the non-aqueous solvent in the electrolyte, as long as the purpose of the present application can be achieved.

[0075] The secondary battery also includes a shell for accommodating the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte, as well as other components known in the field of secondary batteries. This application does not limit the above-mentioned other components. This application does not particularly limit the shell, and it can be a shell known in the art, as long as it can achieve the purpose of this application. For example, the shell can be a hard shell or a flexible shell. The material of the hard shell can be metal. This application does not limit the type of metal, and a metal hard shell known in the art can be used, as long as it can achieve the purpose of this application. The flexible shell can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0076] The secondary battery of the present application is not particularly limited and may include any device that generates an electrochemical reaction. In some embodiments, the secondary battery may include, but is not limited to, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0077] The preparation process of the secondary battery of this application is well known to those skilled in the art and is not particularly limited in this application. For example, the preparation process of the secondary battery may include, but is not limited to, the following steps: stacking the positive electrode sheet, separator, negative electrode sheet, and separator in sequence, and winding and folding them as needed to obtain a wound electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain a secondary battery. In addition, as needed, overcurrent protection elements, guide plates, etc. may be placed in the housing to prevent pressure buildup and overcharging and discharging within the secondary battery.

[0078] The second aspect of the present application provides an electronic device, which includes the secondary battery provided by the first aspect of the present application. The electronic device of the present application has a long service life and good performance.

[0079] The electronic device of the present application is not particularly limited and can be any electronic device known in the art. In some embodiments, the electronic device can include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0080] Example

[0081] The following examples and comparative examples are provided to more specifically illustrate the embodiments of the present invention. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0082] Test methods and equipment:

[0083] L A 、L B test

[0084] After the lithium-ion battery was discharged to 3V at 0.2C, the separator was disassembled and cleaned with dimethyl carbonate (DMC) and dried at 60°C. The separator sample (size 2cm×2cm, area S1cm) located on the straight part of the electrode assembly was cut. 2 ), place the isolation membrane sample in a drying oven and dry it to constant weight, weigh its mass, and record it as m1g. Prepare the electrolyte, in an argon atmosphere glove box with a water content of less than 10ppm, mix ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and vinylene carbonate (VC) in a mass ratio of 20:30:20:28:2 to obtain a basic solvent, add lithium salt LiPF6 and stir evenly to obtain an electrolyte. Among them, based on the total mass of the electrolyte, the mass percentage of lithium salt LiPF6 is 8%, and the remainder is the base solvent. Immerse the dried isolation membrane sample in the above electrolyte to ensure complete immersion. After soaking for 10 minutes, take out the isolation membrane sample from the electrolyte, use filter paper to absorb the excess electrolyte on the surface, and weigh the mass of the isolation membrane sample, and record it as m2g. Calculate the liquid retention L of the isolation membrane in the flat part by the following formula A :L A (g / cm 2 )=(m2-m1) / S1.

[0085] Using the same test method as above, cut the separator sample located at the bend of the electrode assembly, and record the area as S2cm 2 The mass of the separator sample after drying is recorded as m3g, and the mass after absorbing the electrolyte is recorded as m4g. The liquid retention amount L of the separator at the bend is calculated by the following formula B :L B (g / cm 2 )=(m4-m3) / S2.

[0086] E A 、E B test

[0087] After the lithium-ion battery was discharged to 3V at 0.2C, the isolation membrane was disassembled to obtain the isolation membrane. After the isolation membrane was cleaned with dimethyl carbonate (DMC), it was dried at 60°C. The elastic modulus of the isolation membrane was tested by a nanoindentation tester. Along the thickness direction of the isolation membrane, the pressure head was used to apply pressure to any position on the surface of the straight part of the isolation membrane perpendicular to the thickness direction, and the pressure head load displacement was set to 0.5μm. During the loading process, the surface of the isolation membrane undergoes elastic deformation, and the elastic modulus at this point is calculated based on the load-displacement curve during the elastic deformation recovery process of the unloading process: E=σ / ε, where σ is the stress within the elastic range and ε is the strain within the elastic range. The test was conducted 10 times at different positions on the straight part of the isolation membrane, and the average value was calculated as the elastic modulus E of the isolation membrane on the straight part. AThe same test method as above is used to test the surface of the separator bend perpendicular to the thickness direction 10 times, and the average value is calculated as the elastic modulus E of the separator at the bend. B .

[0088] P A 、P B test

[0089] After the lithium-ion battery was discharged at 0.2C to 3V, the separator was disassembled and cleaned with dimethyl carbonate (DMC) and dried at 60°C. A test sample with an area of S3 was punched out at any position on the flat part of the separator.

[0090] Apparent volume test: The thickness of the test sample is recorded as h1, then the apparent volume of the test sample V S =S3×h1.

[0091] True volume test: The test principle is to apply the Archimedean principle of gas displacement through the gas displacement method, and use the Bohr law (PV=nRT) of inert gas with small molecular diameter under certain conditions to measure the true volume of the sample being tested. The test sample is placed in the true density tester, the test system is sealed, and helium is introduced. The gas pressure in the sample chamber and the expansion chamber is detected, and then the following formula is obtained according to Bohr's law: (1) P1(V cell -V samp )=n c RT a ;(2)P a V exp =n e RT a When the valve of the closed test system is opened, the pressure drops to P2, and then the following is satisfied: (3) P2 (V cell -V samp +V exp )=n c RT a +n e RT a The true volume of the test sample is V samp Calculate by the following formula: (4) V samp =(V cell -V exp )×(P2-P a ) / (P1-P2). Where n c is the molar mass of the gas in the sample cup; n e is the molar mass of the gas in the expanding gas; R is the ideal gas constant; T a is the ambient temperature; V cell is the volume of the sample cup; V samp is the true volume of the sample; V expis the volume of the expansion chamber; P1 is the gas pressure in the sample chamber; P2 is the equilibrium pressure after the gas diffuses throughout the system; P a is the pressure of the gas in the expansion chamber.

[0092] The porosity P of the separator in the straight portion is calculated by the following formula: A :P A (%) = (apparent volume of the test sample - true volume of the test sample) / apparent volume of the test sample × 100%. Using the same test method as above, the apparent volume and true volume of the sample at the bend of the isolation membrane are tested to calculate the porosity P of the isolation membrane at the bend. B .

[0093] Dv50 testing of elastic materials

[0094] After the lithium-ion battery is discharged to 3V at 0.2C, the separator is disassembled to obtain the separator, which is cleaned with dimethyl carbonate (DMC) and then dried at 60°C. A separator sample with a size of 2cm×2cm is cut from the curved part of the separator, and the curved separator sample is placed in an ethanol solvent to ensure complete immersion. The sample is soaked for 10 minutes, and then ultrasonically dissolved for 5 minutes. The separator is then removed to obtain a mixed solution containing the elastic material of the first coating of the curved part. The obtained mixed solution is tested using a laser particle size analyzer (model MS3000) in accordance with the national standard "Particle Size Distribution Laser Diffraction Method" (GB / T19077-2016) to obtain the Dv50 of the elastic material.

[0095] Thickness test

[0096] After the lithium-ion battery was discharged at 0.2C to 3V, the separator, positive electrode sheet, and negative electrode sheet were disassembled and cleaned with dimethyl carbonate (DMC) and then dried at 60°C. The cross-sections of the separator, positive electrode sheet, and negative electrode sheet along the thickness direction were polished with argon ions. Then, a scanning electron microscope (SEM) was used to observe and measure the thickness of the first coating, separator, positive electrode material layer, and negative electrode material layer at three locations of the cross-section. The average value was calculated to obtain the thickness of the first coating H. C , the thickness of the isolation film H S , the thickness of the positive electrode material layer H P , the thickness of the negative electrode material layer H N .

[0097] Cyclic performance test

[0098] At 25°C, the lithium-ion battery was charged at a constant current of 4C to a voltage of 4.53V, then charged at a constant voltage of 4.53V to a current of 0.05C, and then discharged at a constant current of 0.5C to a voltage of 3.0V. The above charge and discharge steps were repeated three times. The discharge capacity of the lithium-ion battery at the third cycle was measured and recorded as the initial discharge capacity. The above charge and discharge steps were continued for a total of 600 cycles, and the discharge capacity at the 600th cycle was measured. Cycle capacity retention (%) = discharge capacity at the 600th cycle / initial discharge capacity × 100%.

[0099] After the 600th cycle, the lithium-ion battery was charged at a constant current of 4C to a voltage of 4.53V, and then charged at a constant voltage of 4.53V to a current of 0.05C, so that the lithium-ion battery was in 100% SOC (state of charge). The lithium-ion battery was disassembled to obtain the negative electrode plate, and the surface state of the curved portion of the negative electrode plate was observed. The area on the surface of the curved portion of the negative electrode plate where no lithium deposition and black spots appeared was golden yellow, the lithium deposition area was off-white, and the black spot area was dark purple and reddish. Based on the total area of the single-sided negative electrode material layer, the area ratio of lithium deposition and black spots on the surface of the curved portion of the negative electrode plate of 10 lithium-ion batteries was counted for each embodiment and comparative example, and the average value was calculated as the area ratio of lithium deposition and black spots after the cycle.

[0100] The lithium-ion batteries in the examples and comparative examples of the present application have a discharge cut-off voltage of 3 V and a charge cut-off voltage of 4.53 V. It is understood that when the voltage range marked on the outer packaging of the lithium-ion battery is 3.0 V to 4.53 V, the charge cut-off voltage is 4.53 V and the discharge cut-off voltage is 3.0 V.

[0101] Example 1-1

[0102] <Preparation of Separator>

[0103] A 5 μm thick polyethylene porous polymer film (manufacturer: Celgard Separator Co., Ltd., USA) was used as the separator substrate layer. The substrate layer was divided into curved and straight sections based on the position of the separator in the electrode assembly after winding.

[0104] The elastic material ZIF-8 (Dv50 is shown in Table 2) and the first binder polyacrylic acid are mixed in a mass ratio of 80:20, ethanol is added as a solvent, and the mixture is evenly mixed under the action of a vacuum mixer to obtain a first coating slurry with a solid content of 75wt%. The ceramic particle boehmite and the inorganic layer binder polyacrylic acid are mixed in a mass ratio of 80:20, deionized water is added as a solvent, and the mixture is evenly mixed under the action of a vacuum mixer to obtain a second coating slurry with a solid content of 75wt%. The first coating slurry is evenly coated on one surface of the curved portion of the substrate layer, and the second coating slurry is evenly coated on one surface of the straight portion of the substrate layer. After drying at 90°C, the first coating and the second coating are obtained, both of which have a thickness of 1μm, wherein the coating surface density of the first coating is 0.5mg / cm 2 The coating surface density of the second coating is 0.5 mg / cm 2 Then, the above steps are repeated on the other surface of the substrate layer to obtain a release film with the first coating layer and the second coating layer on both sides.

[0105] <Preparation of positive electrode sheet>

[0106] The positive electrode active material lithium cobalt oxide (LiCoO2), the positive electrode conductive agent conductive carbon black (Super P), and the positive electrode binder polyvinylidene fluoride are mixed in a mass ratio of 97.9:0.9:1.2, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt%. After vacuum stirring, the positive electrode slurry is obtained. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm and dried at 90°C to obtain a positive electrode sheet with a single-sided positive electrode material layer. The above steps are then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode material layer. After drying at 90°C, the sheet is cold pressed, cut into pieces, and the tabs are welded to obtain a positive electrode sheet with a specification of 74mm×867mm for use. The thickness of the single-sided positive electrode material layer is shown in Table 3, and the compacted density of the positive electrode material layer is 4.3g / cm 3 .

[0107] <Preparation of negative electrode sheet>

[0108] Artificial graphite (a negative electrode active material), a silicon-carbon composite material (a silicon-to-carbon mass ratio of 1:1), styrene-butadiene rubber (a negative electrode binder), and acetylene black (a negative electrode conductive agent) were mixed in a mass ratio of 82.4:15:1.4:1.2. Deionized water was added as a solvent to form a slurry with a solid content of 45 wt%. The mixture was stirred evenly in a vacuum mixer to obtain a negative electrode slurry. The negative electrode slurry was evenly coated on one surface of a 6 μm thick negative electrode current collector copper foil and dried at 90°C to obtain a negative electrode sheet coated on one side with a negative electrode material layer. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode sheet coated on both sides with a negative electrode material layer. After drying at 90°C, the sheet was cold pressed, cut into pieces, and the tabs were welded to obtain a negative electrode sheet with a size of 78 mm × 875 mm for future use. The thickness of the single-sided negative electrode material layer is shown in Table 3, and the compacted density of the negative electrode material layer is 1.7 g / cm 3 .

[0109] <Preparation of Electrolyte>

[0110] In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and vinylene carbonate (VC) were uniformly mixed in a mass ratio of 20:30:20:28:2 to obtain a base solvent. LiPF6 was then added and stirred to obtain an electrolyte. The mass percentage of the lithium salt LiPF6, based on the total mass of the electrolyte, was 8%, with the remainder being the base solvent.

[0111] <Preparation of lithium-ion batteries>

[0112] The positive electrode sheet, separator, negative electrode sheet, and separator are stacked in order, with the separator positioned between the positive and negative electrode sheets to provide isolation, and then wound to form an electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, dehydrated at 80°C, and injected with the prepared electrolyte. The lithium-ion battery is obtained through vacuum packaging, standing, forming, and shaping processes, wherein the upper limit of the formation voltage is 4.53V, the formation temperature is 85°C, and the formation time is 60 minutes.

[0113] Example 1-2 to Example 1-16

[0114] Except for adjusting the corresponding preparation parameters according to Table 2, the rest is the same as Example 1-1. Among them, the Dv50 of the elastic material is controlled by adjusting the ball milling time; the porosity of the substrate layer of Example 1-5, Example 1-6, and Example 1-15 changes, P A 、P B 、L A 、L B As shown in Table 1.

[0115] Example 2-1 to Example 2-7

[0116] Except for adjusting the corresponding preparation parameters according to Table 3, the rest is the same as Example 1-1. The thickness H of the first coating layer is controlled by adjusting the coating surface density of the first coating layer. C By adjusting the coating surface density of the second coating layer, the thickness of the second coating layer is made the same as that of the first coating layer; by adjusting the coating surface density of the positive electrode material layer, the thickness H of the positive electrode material layer is adjusted. P The thickness H of the negative electrode material layer can be controlled by adjusting the coating surface density of the negative electrode material layer. N ; The molar ratio of silicon element to oxygen element in the silicon-oxygen composite material of Example 2-7 is 1:1.

[0117] Comparative Example 1

[0118] Except that the following preparation method was used for <Preparation of Isolation Film>, the rest was the same as Example 1-1.

[0119] <Preparation of Separator>

[0120] A 5μm thick polyethylene porous polymer film (manufacturer: Celgard Membrane Co., Ltd., USA) was used as the separator substrate layer. Ceramic boehmite particles and polyacrylic acid, an inorganic layer binder, were mixed in a mass ratio of 80:20, deionized water was added as a solvent, and the mixture was mixed evenly in a vacuum mixer to obtain a second coating slurry with a solid content of 75wt%. The second coating slurry was evenly coated on one surface of the substrate layer (both the curved and straight portions) and dried at 90°C to obtain a second coating layer with a thickness of 1μm. The coating surface density of the second coating layer was 0.5mg / cm. 2 The above steps are then repeated on the other surface of the substrate layer to obtain a release film with a second coating layer on both sides.

[0121] Comparative Example 2

[0122] Except that the following preparation method was used for <Preparation of Isolation Film>, the rest was the same as Example 1-1.

[0123] <Preparation of Separator>

[0124] A 5 μm thick polyethylene porous polymer film (manufacturer: Celgard Membrane Co., Ltd., USA) was used as the separator substrate layer. The elastic material ZIF-8 (Dv50 is shown in Table 2) and the first binder polyacrylic acid were mixed in a mass ratio of 80:20, and ethanol was added as a solvent. The mixture was mixed evenly under the action of a vacuum mixer to obtain a first coating slurry with a solid content of 75 wt%. The first coating slurry was evenly coated on one surface of the substrate layer (on both the curved and straight parts), and dried at 90°C to obtain a first coating layer with a thickness of 1 μm. The coating surface density of the first coating layer was 0.5 mg / cm 2 Then, the above steps are repeated on the other surface of the substrate layer to obtain a release film with the first coating layer on both sides.

[0125] Comparative Examples 3 to 6

[0126] The preparation parameters were adjusted according to Table 2, and the rest were the same as those in Example 1-1. The Dv50 of the elastic material was adjusted by adjusting the ball milling time.

[0127] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 2 and 3.

[0128]

[0129] From Examples 1-1 to 1-16 and Comparative Examples 1 to 6, it can be seen that the present invention designs the isolation membrane structure in the wound structure secondary battery so that L B / L A 、L B 、E B / E A 、E B The value of is within the scope of this application, the cycle capacity retention rate of the lithium ion battery is greater, and the area of lithium plating and black spots after cycling is smaller, indicating that the cycle performance of the lithium ion battery of this application is good. B / L A 、L B 、E B / E A 、E B At least one of the values is outside the scope of this application, the cycle capacity retention rate of the lithium-ion battery is smaller, and the area of lithium plating and black spots after cycling accounts for a larger proportion, indicating that the cycle performance of the lithium-ion battery is poor.

[0130] The Dv50 of the elastic material can affect the cycling performance of lithium-ion batteries. As can be seen from Examples 1-1 to 1-4 and 1-16, when the Dv50 of the elastic material is within the range of this application, the lithium-ion battery's cycling capacity retention rate is high, and the area of lithium plating and black spots after cycling is small, indicating that the lithium-ion battery of this application has good cycling performance.

[0131] The mass percentages of the elastic material and the first binder affect the cycling performance of the lithium-ion battery. As can be seen from Examples 1-1, 1-5, and 1-8, when the mass percentages of the elastic material and the first binder are within the ranges of this application, the lithium-ion battery exhibits a high cycling capacity retention rate and a low percentage of lithium plating and black spot areas after cycling, indicating good cycling performance for the lithium-ion battery of this application.

[0132] The types of elastic material and first binder affect the cycling performance of lithium-ion batteries. As can be seen from Examples 1-1, 1-9, and 1-14, using elastic materials and first binders within the scope of this application results in a high cycling capacity retention rate for lithium-ion batteries, and a low percentage of lithium plating and black spot areas after cycling, indicating good cycling performance for the lithium-ion batteries of this application.

[0133] Table 3

[0134]

[0135] H C and H C / H S The value of will affect the cycle performance of lithium-ion batteries. From Examples 1-1, 2-1 to 2-4, it can be seen that when H C and H C / H S When the value of is within the range of this application, the cycle capacity retention rate of the lithium-ion battery is large, and the area of lithium deposition and black spots after cycling accounts for a small proportion, indicating that the cycle performance of the lithium-ion battery of this application is good and the energy density is high.

[0136] H P and H N The value of will affect the cycle performance of lithium-ion batteries. From Examples 1-1, 2-5 and 2-6, it can be seen that when H P and H N When the value of is within the range of this application, the cycle capacity retention rate of the lithium-ion battery is large, and the area of lithium deposition and black spots after cycling accounts for a small proportion, indicating that the cycle performance of the lithium-ion battery of this application is good and the energy density is high.

[0137] The type of negative electrode active material affects the cycling performance of lithium-ion batteries. As can be seen from Examples 1-1 and 2-7, using negative electrode active materials within the scope of this application results in a higher cycling capacity retention rate for lithium-ion batteries, and a lower percentage of lithium plating and black spot areas after cycling, indicating good cycling performance for the lithium-ion batteries of this application.

[0138] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article comprising a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, or article.

[0139] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0140] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A secondary battery comprising an electrode assembly, wherein the electrode assembly is a wound structure and comprises a straight portion and a curved portion. The electrode assembly includes a separator, a positive electrode sheet and a negative electrode sheet. The separator includes a substrate layer and a first coating provided on at least one surface of the substrate layer. The first coating is located at the curved portion of the electrode assembly. The liquid retention capacity of the separator in the straight portion is L A g / cm 2 The liquid holding capacity of the separator in the bending part is L B g / cm 2 , 1.05≤L B / L A ≤2, 0.15≤L B ≤0.3; the elastic modulus of the isolation membrane in the straight portion is E A GPa, the elastic modulus of the isolation diaphragm at the bent portion is E B GPa, 0.5≤E B / E A ≤0.99, 0.48≤E B ≤0.

95.

2. The secondary battery according to claim 1, wherein The secondary battery satisfies at least one of the following characteristics: (1)1.14≤L B / L A ≤1.78; (2)0.17≤L B ≤0.27； (3)0.67≤E B / AND A ≤0.93; (4)0.65≤E B ≤0.89。 3. The secondary battery according to claim 1, wherein The porosity of the separator in the straight portion is P A %, the porosity of the separator in the curved portion is P B %, 1.05≤P B / P A ≤1.25,65≤P B ≤95.

4. The secondary battery according to claim 3, wherein 1.07≤P B / P A ≤1.21,80≤P B ≤91。 5. The secondary battery according to claim 1, wherein The first coating layer includes an elastic material, and based on the mass of the first coating layer, the mass percentage of the elastic material is 50% to 95%.

6. The secondary battery according to claim 5, wherein The elastic material includes at least one of a metal organic framework material or a porous elastic polymer, the metal organic framework material includes at least one of ZIF-8, MIL-53, MOF-74, PCN-224, UiO-66, MOF-801, MOF-200, MOF-888, MOF-767, MOF-808, MOF-253, MOF-199, MOF-505, MOF-740, MOF-841, MOF-525, MOF-210, MOF-800, MOF-701 or MOF-820, and the porous elastic polymer includes at least one of porous polyurethane, porous silicone rubber, porous polyvinyl alcohol, porous sodium polyacrylate, porous polyacrylate or porous polyacrylonitrile.

7. The secondary battery according to claim 5, wherein The Dv50 of the elastic material is 150 nm to 750 nm.

8. The secondary battery according to any one of claims 1 to 7, wherein The thickness of the first coating is H C μm, the thickness of the isolation film is H S μm, 0.5≤H C ≤2.5,0.05≤H C / H S ≤0.

25.

9. The secondary battery according to any one of claims 1 to 7, wherein The first coating layer further comprises a first binder, and based on the mass of the first coating layer, the mass percentage of the first binder is 5% to 50%; The first binder includes at least one of polyacrylic acid, polyacrylate, methyl acrylate, ethyl acrylate, butyl acrylate or polyvinylidene fluoride.

10. The secondary battery according to any one of claims 1 to 7, wherein The secondary battery satisfies at least one of the following characteristics: (1) The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector, wherein the thickness of the positive electrode material layer is H P μm, 40≤H P ≤200; (2) The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector, and the thickness of the negative electrode material layer is H N μm, 25≤H N ≤100.

11. The secondary battery according to any one of claims 1 to 7, wherein The negative electrode plate includes a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector, the negative electrode material layer includes a negative electrode active material, the negative electrode active material includes a silicon-containing material, and the silicon-containing material includes at least one of a silicon-carbon composite material, a silicon-oxygen composite material or elemental silicon. 12 . An electronic device comprising the secondary battery according to claim 1 .

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