Insulating film, secondary battery and electric device

Abstract

The invention provides an insulating film, a secondary battery and an electric device. The insulating film comprises at least one layer of first film, and the first film comprises 30-60 parts by weight of PA6; 15 to 40 parts by weight of polystyrene; 5-15 parts by weight of a compatible auxiliary agent; and 10-20 parts by weight of a filler. The insulating film provided by the invention can be dissolved through by electrolyte, has good insulativity, and can still keep good mechanical properties and insulativity after being aged for a long time under high-temperature and high-humidity conditions.

Description

Technical Field

[0001] The present application relates to the field of encapsulated insulating films, and in particular to an insulating film, a secondary battery, and an electrical device. Background Art

[0002] In recent years, batteries have been widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. To prevent secondary hazards caused by electrolyte leakage, timely warning and maintenance are necessary.

[0003] As the application of lithium-ion batteries in power batteries becomes more mature, the requirements for energy density are also getting higher and higher. The degree of integration of battery cells determines the volume energy density of the battery pack. The spatial design of the battery pack is crucial to the volume energy density. The design of the battery pack not only requires high integration but also needs to be safer and more reliable. Therefore, inverted cells have become an option to make the battery pack thinner, lighter, safer and more reliable.

[0004] However, in the inverted cell solution, the sealing pins, tabs, explosion-proof valves and other locations are relatively weak and easily affected by external forces, which can easily lead to electrolyte leakage in severe cases. Since an insulating sheet is attached to the existing bottom guard plate, after the electrolyte leaks, a large amount of leaked electrolyte usually needs to flow to the drain valve position before the alarm device can be triggered, and the alarm cannot be quickly realized. Or because the overlap path is too long, the insulation resistance value does not drop to the insulation alarm threshold, and the electrolyte leakage cannot be detected. The method of detecting electrolyte leakage through gas molecules requires additional space and cost for the battery pack. Summary of the Invention

[0005] The present application is made in view of the above-mentioned problems, and its purpose is to provide an insulating material that can be dissolved and penetrated by electrolyte, and arrange the film of the insulating material at an appropriate position on the bottom guard plate. When electrolyte leakage occurs, the leaked electrolyte can dissolve and penetrate the insulating material film and leak to the metal plate of the bottom guard plate, thereby realizing a conductive circuit between the metal plate and the top cover of the battery cell and triggering an alarm, thereby realizing a rapid battery cell electrolyte leakage detection alarm.

[0006] The first aspect of the present application provides an insulating film, which includes at least one first film, wherein the first film includes 30-60 parts by weight of PA6; 15-40 parts by weight of polystyrene; 5-15 parts by weight of a compatibilizing agent; and 10-20 parts by weight of a filler.

[0007] Therefore, the present application provides the above-mentioned insulating film, which has good insulation and hydrolysis resistance and can be used as an insulating film for the bottom guard plate. In addition, the insulating film can be dissolved by the electrolyte. After dissolution, the electrolyte leaks into the box to trigger the insulation alarm.

[0008] In some embodiments, the first film comprises 40-60 parts by weight of PA6, 15-35 parts by weight of polystyrene, and 10-15 parts by weight of a compatibilizer. By setting the PA6, polystyrene, and compatibilizer contents within these ranges, the insulating film can achieve enhanced resistance to electrolyte penetration.

[0009] In some embodiments, the melt index of PA6 in the first film is 3-10 g / 10 min under the test conditions of 2.16 kg and 230° C.

[0010] In some embodiments, the polystyrene in the first film has a melt index of 3-10 g / 10 min under the test conditions of 2.16 kg and 230° C.

[0011] In some embodiments, the compatibilizer comprises an olefin polymer grafted with maleic anhydride, wherein the grafting ratio of maleic anhydride in the olefin polymer is 0.8% to 2.0%. The maleic anhydride-grafted olefin polymer as a compatibilizer can improve the compatibility between PA6 and polystyrene, thereby increasing the tensile strength and impact strength of the product.

[0012] In some embodiments, the maleic anhydride grafted olefin polymer includes a maleic anhydride grafted polypropylene-polyethylene copolymer and / or a maleic anhydride grafted hydrogenated styrene-butadiene copolymer.

[0013] In some embodiments, the filler includes one or more inorganic fillers selected from the group consisting of silica powder, talc, white carbon black, calcium carbonate, and calcium sulfate. Inorganic fillers can improve the dissolution and penetration ability of the insulating film, and can also increase the modulus of the material, thereby facilitating the film's die-cutting processability and flatness.

[0014] In some embodiments, the filler has a particle size ranging from 1250 mesh to 20000 mesh, optionally from 2500 mesh to 8000 mesh.

[0015] In some embodiments, the first film further comprises 0.2-0.4 parts by weight of an antioxidant; and 0.1-0.5 parts by weight of a lubricant.

[0016] In some embodiments, the lubricant includes at least one of erucamide, EBS amides, polyethylene wax, and silicone masterbatch.

[0017] In some embodiments, the first film further comprises: 0.5-2 parts by weight of masterbatch; and / or 10-20 parts by weight of polyester and / or polyamide fibers.

[0018] In some embodiments, the insulating film further comprises at least one fiber layer, wherein the first film and the fiber layer are arranged alternately. The fiber layer provides support for the insulating film and enhances the strength of the film.

[0019] In some embodiments, the fiber layer includes polyester fiber and / or polyamide fiber. The polyester and / or polyamide fiber layer can provide good support for the insulating film and does not hinder the flow of electrolyte.

[0020] In some embodiments, the fiber layer is a fiber web or fiber cloth.

[0021] In some embodiments, the fiber layer includes metal fibers or wires, each independently made of at least one of copper, silver, gold, and platinum. The fiber layer provides excellent support for the insulating film. Furthermore, the metal fibers or wires are conductive, allowing the insulating film to be directly bonded to the detection device, shortening the bonding distance and enabling a rapid alarm in the event of an electrolyte leak.

[0022] In some embodiments, the diameter of the metal wire is less than or equal to 50 μm. In some optional embodiments, the diameter of the metal wire is in the range of 5 μm-50 μm.

[0023] In some embodiments, the insulating film includes two layers of the first films and one layer of the fiber layer, wherein the fiber layer is located between the two layers of the first films.

[0024] In some embodiments, the insulating film further includes at least one second film, which is an electrolyte-resistant insulating film. The insulating film comprises the first film, the fiber layer, and the second film, which are sequentially arranged. Further including the electrolyte-resistant second film further enhances the insulating properties of the insulating film and prevents secondary hazards caused by electrolyte leakage that penetrates the insulating film and then leaks into other components of the secondary battery.

[0025] In some embodiments, the fiber layer has a thickness of 5 μm to 50 μm.

[0026] In some optional embodiments, the fiber layer has a thickness of 10 μm-50 μm, optionally 10 μm-30 μm.

[0027] In some embodiments, the thickness of the first film is 100 μm-475 μm.

[0028] In some embodiments, the time for the first film to be dissolved through by the electrolyte under the conditions of a thickness of 100-475 μm and a temperature of 35±5° C. is ≤5 h, optionally ≤4 h, and further optionally ≤2.5 h.

[0029] In some embodiments, the electrolyte includes at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, ethylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0030] The second aspect of the present application also provides a secondary battery, which includes a bottom protective plate, which includes an insulating layer and a metal plate in contact with the insulating layer, the insulating layer having an opening that penetrates the thickness of the insulating layer, and the side of the opening facing the metal plate is provided with an insulating film of the first aspect of the present application that closes the opening.

[0031] Therefore, the secondary battery provided by the present application can realize a rapid electrolyte leakage alarm.

[0032] In an optional embodiment, the secondary battery is a secondary battery with inverted cells.

[0033] A third aspect of the present application provides an electrical device comprising the secondary battery described above.

[0034] The insulating film of the present application has excellent insulating properties and maintains good mechanical properties after aging at 85°C / 85% RH. Furthermore, the insulating film of the present application can be dissolved through by electrolyte. In some preferred embodiments, the first insulating film having a thickness of 100-475 μm has a dissolution time of less than or equal to 2 hours at 35±2°C when the leakage volume is ≥10 ml, enabling rapid alarm of electrolyte leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is an enlarged schematic diagram of the structure of the bottom guard plate of one embodiment of the present application.

[0036] Figure 2 Schematic diagram of an electrical device including the secondary battery of the present application as a power source.

[0037] In the accompanying drawings, which are not necessarily drawn to scale, reference numerals are as follows: 10 insulation testing equipment, 11 pressure strip, 12 electrolyte-intolerant insulating film, 13 opening, 14 metal plate, 15 insulating layer, 16 MPP, 17 sheet, 18 separator, 19 cell cover, 20 cell. DETAILED DESCRIPTION

[0038] Below, the embodiments of the insulating film, bottom guard plate and secondary battery of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0039] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0041] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0042] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0043] Unless otherwise specified, the terms used in this application have the common meanings generally understood by those skilled in the art.

[0044] Unless otherwise specified, the values of the parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in this application.

[0045] In a secondary battery with inverted cells, the inverted cell poles, explosion-proof valves, and sealing pins are oriented downward to avoid thermal runaway thermal shock to the upper cover of the battery pack body. However, there is a risk of electrolyte leakage when these components are subjected to the weight of the cell or external compression. In conventional secondary batteries with inverted cells, electrolyte leakage is usually alarmed by an insulation detection device in the drain valve of the battery device. However, since the drain valve is usually located far away from the cell, a large amount of electrolyte needs to be leaked, usually more than 1L, before it can flow to the drain valve position to be detected. This process usually takes a long time and cannot achieve a quick alarm. In order to shorten the insulation detection time, the inventor designed to connect the insulation detection equipment between the cell top cover and the bottom guard plate to shorten the overlap path after the electrolyte leaks. However, the shoulder molding provides a fulcrum for the cell shoulder, and below it is an insulating layer, such as PC, PP, PET, PI, etc., which have properties such as resistance to electrolyte corrosion, high weather resistance and insulation. Therefore, when the electrolyte leaks, it cannot dissolve through the insulation layer, and the electrolyte cannot quickly connect to the bottom guard plate, so it is impossible to use insulation detection to alarm and alert the driver and passengers.

[0046] To this end, the present application proposes an insulating film that is not resistant to electrolyte, see Figure 1 , which schematically illustrates the structure of the bottom guard plate for an inverted secondary battery cell with an electrolyte-intolerant insulating film proposed in this application. The electrolyte-intolerant insulating film 12 is disposed below the bead 11 on the shoulder of the bottom guard plate. An insulating layer 15 having openings 13 is disposed between the bead 11 and the electrolyte-intolerant insulating film 12. When the vehicle is impacted or squeezed, causing the cell electrolyte to leak, the electrolyte leaks from the openings 13 onto the electrolyte-intolerant insulating film 12, dissolving through the film in a relatively short period of time and seeping into the metal plate 14 of the bottom guard plate. This forms a conductive circuit between the top cover 19 and the metal plate 14, thereby triggering the insulation detection device 10 to generate an alarm.

[0047] Plastic films typically used for liquid battery packaging require electrical insulation, a certain level of mechanical strength, weather resistance (e.g., aging resistance, oxidation resistance), and electrolyte resistance. Some polymers are soluble in organic solvents but not electrolyte-resistant. However, these polymers often lack sufficient insulation, weather resistance, and mechanical properties, making them unsuitable for battery packaging.

[0048] To this end, the present application provides an insulating film that meets the insulation performance, mechanical properties and weather resistance, and meets the requirements of electrolyte dissolution, including a bottom protective plate of the insulating film, and a secondary battery and an electrical device with an inverted battery cell including the bottom protective plate.

[0049] Insulation film

[0050] Based on this, the first aspect of the present application provides an insulating film comprising at least one first film layer, the first film comprising: 30-60 parts by weight of PA6; 15-40 parts by weight of polystyrene; 5-15 parts by weight of a compatibilizing agent; and 10-20 parts by weight of a filler.

[0051] In the present application, PA6, or nylon 6, is a polymer formed by the polymerization of caprolactam. PA6 has good mechanical properties and is a raw material commonly used in the preparation of films. PA6 has a certain solubility in organic solvents. Polystyrene (PS) refers to a polymer synthesized from styrene monomers through a free radical addition polymerization reaction. Polystyrene has good electrical insulation and resistance to chemical corrosion (i.e., it is difficult to dissolve in organic solvents), but has poor toughness and insufficient impact resistance. The present application combines the two in the above-mentioned ratio to form the matrix of the insulating film, which can meet the requirements of mechanical strength and insulation performance, and can also be dissolved through by the electrolyte in a relatively short time, thereby realizing a rapid alarm for electrolyte leakage.

[0052] In this application, a compatibilizer refers to an agent that helps two incompatible polymers combine together through intermolecular bonding forces, thereby forming a stable blend. The compatibilizer helps PA6 and polystyrene combine through intermolecular forces to form a stable blend.

[0053] In this application, fillers refer to solid substances added to materials to improve physical properties or reduce material costs, and generally do not adversely interact with the material components. In this application, the addition of fillers can reduce the amount of polymer used. Furthermore, the addition of fillers can further shorten the time it takes for the film to dissolve when it encounters the electrolyte.

[0054] The above components are combined within the specified dosage range to provide the insulating film with excellent insulation properties and hydrolysis resistance. The film exhibits sufficient mechanical properties in PCT high-temperature and high-pressure accelerated aging (i.e., a sample is placed in a 100% RH saturated water vapor and pressure environment for a period of time, such as typically 8 hours, 12 hours, or 24 hours) or double 85 aging (i.e., a sample is placed under 85°C, 85% RH conditions for a certain period of time, such as 1000 hours or 1200 hours). These tests meet the requirements for insulating films used in underbody panels. Furthermore, the insulating film can be dissolved through by the electrolyte in the event of an electrolyte leak, thereby reducing the insulation resistance to the alarm threshold and achieving a rapid alarm. The addition of fillers, antioxidants, and lubricants to the film can further improve the material's service life and processing performance.

[0055] In some embodiments, the amount of PA6 in the first film is 40-60 parts by weight; the amount of polystyrene is 15-35 parts by weight; and the amount of the compatibilizer is 10-15 parts by weight. The content of PA6 and polystyrene in the first film can vary within a certain range. By setting the content of PA6 and polystyrene within the above range, the insulating film can have a better resistance to electrolyte penetration and can be dissolved by the electrolyte more quickly at room temperature to achieve a rapid electrolyte leakage alarm. Exemplarily, the weight of PA6 can be 30, 35, 38, 40, 42, 45, 48, 50, 52, 55, 60 parts by weight, or a value within a range consisting of any numerical values. In some optional embodiments, the amount of PA6 in the first film is 30-50 parts by weight, 35-45 parts by weight, 35-50 parts by weight, 40-50 parts by weight, or 40-45 parts by weight. For example, the weight of polystyrene can be 20, 25, 28, 30, 32, 35, 40 parts by weight, or any range thereof. In some optional embodiments, the amount of polystyrene in the first film is 15-30 parts by weight, 20-34 parts by weight, or 20-30 parts by weight. For example, the amount of compatibilizer used is 5, 8, 10, 12, 14, 15 parts by weight, or any range thereof.

[0056] In some embodiments, the melt index of PA6 in the first film is 3-10 g / 10 min under the test conditions of 2.16 kg and 230° C.

[0057] PA6 has a melt index within the above range, exhibiting a balance between organic solvent solubility and mechanical properties. For example, the melt index of PA6 tested at 230°C (2.16 kg) can be 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, or 9 g / 10 min, or any range thereof.

[0058] Melt flow index, also known as melt flow rate, is an important indicator used to measure the fluidity of plastics or other thermoplastic materials under specified temperature and pressure conditions. The melt flow index of the polymer component in this application can be determined using the standard ISO 1133 method.

[0059] The present application has no particular restriction on the source of PA6, for example, it can be a commercially available product, such as: DuPont 70G33, Yuehua YH3400, YH400, Xinhui Meida M3400, BASF B33, B36, B40, DSM F130, F132, F136, Japan Ube 1013B, etc.

[0060] The polystyrene in the first film is not particularly limited. In some embodiments, the polystyrene in the first film has a melt index of 3-10 g / 10 min at a test temperature of 2.16 kg and 230° C. The melt index of the polystyrene is within the above range and has balanced insulating properties. For example, the melt index of the polystyrene can be 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, 9 g / 10 min, or any range thereof at a test temperature of 2.16 kg and 230° C.

[0061] The present application does not particularly limit the source of polystyrene, for example, it can be a commercially available product, such as: HIPS476L, PS143E of BASF-YPC, GGPPS 630A of Dow Chemical, PG80 of Chimei, HP825 of Formosa Chemicals and Fibre Corporation, PS5112 of LyondellBasell, PS125 of Sabic, etc., but not limited thereto.

[0062] According to a specific embodiment, the compatibilizing agent includes an olefin polymer grafted with maleic anhydride. As a compatibilizing agent, the olefin polymer grafted with maleic anhydride can improve the compatibility between PA6 and polystyrene and increase the tensile strength and impact strength of the product.

[0063] In some specific embodiments, the maleic anhydride grafted olefin polymer includes a maleic anhydride grafted polypropylene-polyethylene copolymer and / or a maleic anhydride grafted hydrogenated styrene-butadiene copolymer.

[0064] In some more specific embodiments, the grafting rate of maleic anhydride in the hydrocarbon polymer is 0.8% to 2.0%, optionally 0.8% to 1.7%, and particularly 0.8% to 1.4%. For example, the grafting rate can be 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 any range therebetween.

[0065] When the grafting rate of maleic anhydride in the maleic anhydride-grafted olefin polymer is within the above range, a lower grafting rate of maleic anhydride is beneficial to shortening the dissolution time of the material, and a higher grafting rate of maleic anhydride is beneficial to the compatibility of PA6 and PS materials.

[0066] In some embodiments, the compatibilizer has a mass melt index of 0.1-10 g / 10 min, optionally 0.5-8 g / 10 min, under 2.16 kg test conditions. For example, it is 0.1 g / 10 min, 0.5 g / 10 min, 1 g / 10 min, 2 g / 10 min, 5 g / 10 min, 8 g / 10 min, 10 g / 10 min, or the like, or any range of values. When the melt index of the compatibilizer is within the above range, it is easy to blend with the two matrix polymers, promotes the mutual compatibility of the two matrix polymers, and forms a blend with relatively uniform properties.

[0067] Compatibilizers can be commercially available products, for example, Kraton's RP6670 (1.1% maleic anhydride grafting rate), MD6684 (1.05% maleic anhydride grafting rate), FG1901 (1.7% maleic anhydride grafting rate), FG1924 (1.0% maleic anhydride grafting rate), FG1652 (1.5% maleic anhydride grafting rate), etc.

[0068] In some embodiments, the amount of the filler is 10-20 parts by weight. Exemplarily, the amount of the filler is 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 parts by weight, or any range thereof. Alternatively, the amount of the filler is 15-20 parts by weight.

[0069] The filler is an inorganic filler. The inorganic filler may include one or more of talc, calcium carbonate, silica powder, white carbon black, barium sulfate, etc. Optionally, the inorganic filler includes calcium carbonate and / or barium sulfate.

[0070] Inorganic fillers can improve the dissolution and penetration ability of insulating films, and can also increase the modulus of the material, which is beneficial to the film's die-cutting processability and lamination flatness.

[0071] In some embodiments, the particle size of the filler is in the range of 1250 mesh to 20000 mesh. For example, the particle size of the filler can be 1250 mesh, 1500 mesh, 2000 mesh, 2500 mesh, 3000 mesh, 3500 mesh, 4000 mesh, 5000 mesh, 6000 mesh, 7000 mesh, 8000 mesh, 9000 mesh, 10000 mesh, 15000 mesh, 20000 mesh, or any range thereof. Alternatively, the particle size of the filler is in the range of 2500 mesh to 8000 mesh.

[0072] In some embodiments, the first film further comprises 0.2-0.4 parts by weight of an antioxidant; and 0.1-0.5 parts by weight of a lubricant.

[0073] In this application, antioxidants are substances that block the adverse effects of oxygen, helping to capture and neutralize free radicals. Antioxidants are used to slow down the oxidative aging of insulating films and extend their service life.

[0074] In this application, lubricants are used to reduce friction between polymer materials, improve the fluidity of plastic melts, prevent polymer materials from adhering to equipment during processing, and ensure the surface finish of the finished product. In some embodiments, the antioxidant is used in an amount of 0.2-0.4 parts by weight. Exemplary amounts include 0.2, 0.3, or 0.4 parts by weight, or any range thereof.

[0075] The present application does not particularly limit the type of antioxidant. For example, the antioxidant is a mixture of phosphite antioxidant 168 and hindered phenol antioxidant 1010 in a ratio of 1:1.

[0076] Antioxidants can delay the oxidative aging of insulating films, improve the anti-aging properties of materials, such as double 85 aging, PCT aging performance, and extend service life.

[0077] In some embodiments, the amount of the lubricant is 0.1-0.5 parts by weight. Exemplarily, the amount of the lubricant is 0.1, 0.2, 0.3, 0.4, 0.5 parts by weight, or any range thereof.

[0078] In some specific embodiments, the lubricant includes at least one of erucamide, EBS amides, polyethylene wax, and silicone masterbatch. In more specific embodiments, the lubricant is silicone masterbatch. Using these lubricants can effectively reduce material sticking to equipment during film formation, as well as friction between fillers and polymers, improve melt fluidity, and prevent polymer adhesion to equipment during processing.

[0079] According to the present application, the components of the first film may further include other additives. In some embodiments, in the insulating film, the first film further includes 0.5-2 parts by weight of masterbatch; and / or 10-20 parts by weight of polyester and / or polyamide fiber.

[0080] The masterbatch is mainly used to provide color for the film. Exemplarily, the weight portion of the masterbatch can be 0.5, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2 parts by weight, or any value within a range consisting of these values.

[0081] In some specific embodiments, the masterbatch includes one or more of Cabot 6269, aniline black, Cabot 660R, and Cabot 2014.

[0082] Polyester fiber is a synthetic fiber made from organic dibasic acid and diol by chemical polycondensation, and has excellent shape retention. Polyamide fiber is a thermoplastic resin with repeating amide groups on the main chain of the molecule. When polyester and / or polyamide fibers are added to the first film in the above-mentioned addition amount, they play a supporting role, which is beneficial to enhance the strength of the film, while not affecting the electrolyte dissolving the polymer matrix around the fiber and passing through the film. Exemplarily, the weight parts of polyester and / or polyamide may be 10, 12, 14, 16, 18, 20 parts by weight, or a value within a range consisting of any numerical values. Polyester and / or polyamide can be commercially available products. Exemplarily, it can be a woven cloth formed by fiber yarn with a fiber diameter of 10 μm, such as textile yarn purchased from Jin Zili New Materials, but is not limited thereto.

[0083] The insulating film of the present application may include only one first film, or may include two or more first films with different compositions.

[0084] In addition, in some embodiments, the insulating film further comprises at least one fiber layer, and the first film and the fiber layer are arranged alternately. The fiber layer provides support for the insulating film and enhances the strength of the film.

[0085] In some embodiments, the fiber layer includes polyester fibers and / or polyamide fibers. Optionally, the fiber layer is a fiber mesh or fiber cloth. Similarly, the polyester and / or polyamide fiber layer can provide good support for the insulating film without hindering the flow of electrolyte. To facilitate the flow of electrolyte through the fiber layer, the fiber density should not be too high. For example, the fiber cloth can be a sparse woven cloth. The term "sparse" is a degree term indicating the relative fiber density in the fiber cloth. Those skilled in the art will understand that the "sparse woven cloth" referred to here refers to the fiber density of the woven cloth when it does not hinder the electrolyte from passing through the woven cloth quickly. When selecting different fibers (such as different materials or different fineness, etc.), it is relatively easy to determine the appropriate fiber density. For example, the mesh size of the fiber cloth can be 50-200 mesh, for example 50, 100, 150, or 200 mesh. In a preferred embodiment, the mesh size of the fiber cloth is 100 mesh.

[0086] The present application does not particularly limit the diameter of the polyester and polyamide fibers in the fiber layer. Considering the overall thickness of the insulating film, the diameter of the polymer fiber should not be too large, and can be 10 μm to 50 μm for example. For example, the diameter of the polymer fiber can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or a value within a range consisting of any numerical values. Optionally, the diameter of the polymer fiber can be 10-30 μm, in particular 10-20 μm.

[0087] In some embodiments, the fiber layer may be one or more layers. The fiber layer has a thickness of less than 50 μm, optionally 10 μm to 50 μm, and particularly 30 to 50 μm. Exemplarily, the fiber layer has a thickness of 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any range thereof.

[0088] In other embodiments, the fiber layer comprises metal fibers or wires. Optionally, the metal used includes at least one of copper, silver, gold, and platinum. Copper wires or copper fibers are preferred. On the one hand, the fiber layer provides good support for the insulating film. On the other hand, the metal fibers or wires are conductive, allowing the insulating film to be directly bonded to the detection device, shortening the bonding distance and enabling a rapid alarm in the event of an electrolyte leak.

[0089] The metal fibers or wires can be arranged in a mesh pattern, in parallel lines, or in other arrangements. In this embodiment, at least a portion of the metal fibers or wires at the edge of the insulating film contacts the bottom guard plate. When the electrolyte leaks, the electrolyte only dissolves through the upper first insulating film (it does not need to completely dissolve through the entire insulating film), and an alarm is activated by connecting the metal wires or fibers to the metal plate of the bottom guard plate. This arrangement allows for faster alarm times and high efficiency and sensitivity in detecting electrolyte leaks.

[0090] The present application does not place any particular restriction on the diameter of the metal fibers or metal wires in the fiber layer. Considering the overall thickness of the insulating film, the diameter of the metal fibers or metal wires is not easy to be too large. In some embodiments, the diameter of the metal fibers or metal wires is less than or equal to 50 μm. Optionally, the diameter of the metal fibers or metal wires is in the range of 5 μm-50 μm. Exemplarily, the diameter of the metal fibers or metal wires may be 10-30 μm. Exemplarily, the diameter of the metal fibers or metal wires may be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, or a value within a range consisting of any numerical values. Optionally, the diameter of the metal fibers or metal wires may be 15-25 μm.

[0091] In one embodiment, the insulating film includes two layers of the first film and one fiber layer. The two layers of the first film and one fiber layer are alternately arranged, i.e., the two layers of the first film are located on both sides of the fiber layer. Thus, the fiber layer is wrapped in the insulating first film, resulting in the insulating film having excellent insulation properties.

[0092] In some embodiments, when the fiber layer comprises metal fibers or wires, the insulating film further comprises at least one second film, which is an electrolyte-resistant insulating film. This electrolyte-resistant second film further enhances the insulating film's insulation properties and prevents electrolyte leakage from dissolving through the insulating film and subsequently leaking into other components of the secondary battery, potentially causing secondary hazards. In one embodiment, when the fiber layer comprises metal fibers or wires, when the leaked electrolyte dissolves through the first insulating film, it contacts the metal fibers or wires, further connecting to the metal plate of the bottom cover plate to form a loop, triggering an alarm. This shortens the time required for the electrolyte to dissolve through the insulating layer and improves battery safety. In one specific embodiment, the insulating film comprises the first film, the fiber layer, and the second film, arranged in sequence, with the surface of the first film facing the interior of the battery. When the fiber layer comprises metal fibers or wires, the second film does not need to dissolve through. In the event of an electrolyte leak, the upper first film dissolves through and contacts the metal layer of the interlayer, signaling the electrolyte leak through the metal layer. The present application has no particular limitation on the thickness of the second film, which can be adjusted according to the overall thickness requirement of the insulating film.

[0093] The present application does not particularly limit the material of the second film; any film that meets the requirements for mechanical properties, insulation properties, and hydrolysis and electrolyte resistance can be used. For example, the substrate of the second film can be a nylon film, a polypropylene film, a polycarbonate film, or the like. The second film can also include fillers, antioxidants, lubricants, and optionally additives such as UV inhibitors, masterbatches, and polyester and / or polyamide fibers.

[0094] Exemplarily, the second film may include 83-89 parts by weight of a blended modified product of PA and PS; 10-15 parts by weight of a filler; 0.2-0.4 parts by weight of an antioxidant; and 0.1-0.5 parts by weight of a lubricant, wherein the ratio of PA to PS in the blended modified product of PA and PS is in the range of 2:1-3:1.

[0095] Illustratively, the thickness of the second film may be 10 μm-500 μm, for example, 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, or any value within a range thereof.

[0096] In some embodiments, the thickness of the first film is 100-475 μm, optionally, the thickness of the first film is 100-200 μm. For example, the thickness of the first film can be 100 μm, 125 μm, 150 μm, 175 μm, 200 μm, 225 μm, 250 μm, 275 μm, 300 μm, 325 μm, 350 μm, 375 μm, 400 μm, 425 μm, 450 μm, 475 μm, or any range thereof.

[0097] In embodiments including a fiber layer, the fiber layer has a thickness within the above-defined range, providing suitable processing properties for the insulating film and enabling the insulating film to achieve conductivity after being dissolved through by the electrolyte, allowing it to overlap with the detection device on the bottom guard plate to achieve a rapid alarm. The thickness of the first film, within the above-defined range, allows the first film to be quickly dissolved through by the electrolyte at room temperature, achieving a rapid alarm.

[0098] In the above embodiment of the sandwich structure of two first films and one fiber layer, the total thickness of the insulating film is 240 μm-1000 μm.

[0099] In some embodiments, the time it takes for the first film to be dissolved through by the electrolyte is ≤ 5 hours, optionally ≤ 4 hours, or optionally ≤ 2.5 hours, at a thickness of 100-475 μm and a temperature of 35±5°C. Dissolution through the electrolyte within this time frame enables timely alarming of electrolyte leakage, effectively preventing secondary hazards caused by electrolyte leakage.

[0100] The electrolyte can dissolve through the first film after contact with the first film. In some optional embodiments, the electrolyte includes at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, ethylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0101] Preparation method of insulating film

[0102] The insulating film provided in the present application can be prepared by any suitable method. For example, the insulating film provided in the present application can be prepared by the following method. Add components such as PA6, polystyrene, compatibilizer, filler, antioxidant and lubricant to a high-speed dispersant according to the required weight parts, mix and stir (for example, 120 seconds) to obtain a mixture. Discharge the mixture from the main feed port. If polyester and / or polyamide fibers are contained, discharge the polyester and / or polyamide fibers from the side feed port. Granulate the granules by extrusion granulation through a twin-screw extruder. The extruder temperature is controlled between 220°C and 245°C. The process parameters of extrusion granulation include: zone one temperature of 220-230°C, zone two temperature of 220-230°C, zone three temperature of 225-240°C, zone four temperature of 230-245°C, zone five temperature of 230-245°C, die head temperature of 235-245°C, and main engine speed of 350-600 rpm. The granulated material is then passed through a cast film stretching device to prepare first film products of different thicknesses.

[0103] In some embodiments, the insulating film further includes at least one fiber layer. A preparation method may include preparing a multilayer film by subjecting the aforementioned granulated material and fiber layer raw materials to a multilayer co-extrusion cast film stretching apparatus. For example, the upper and lower layers of the fiber layer may be the first film, or the upper layer of the fiber layer may be the first film, and the lower layer may be the second film. Co-extrusion cast film stretching may be used to produce film products of varying thicknesses, with the fiber layer serving as the intermediate layer. The second film may be obtained by similar methods using granulated material.

[0104] The term "melt index" as used herein has the conventional meaning in the art and is a numerical value indicating the fluidity of a polymer material during processing. The melt index test method is to first allow the polymer material to be tested to melt into a fluid within a certain time (e.g., 10 minutes) at a certain temperature and pressure (different standards for various materials), and then measure the amount of grams (g) that flows out through a 2.095mm diameter tube. The larger the value, the better the processing fluidity of the plastic material, and vice versa. The melt index test standard can be GB / T3682, ASTM D 1238, ISO1133, etc. The measuring instrument for this test standard can be a melt index index meter (such as MeltIndexer), and the unit is g / 10min.

[0105] The term "grafting rate" herein has the conventional meaning in the art, and refers to the ratio of the amount of monomer or polymer branches attached to the graft copolymer to the total amount of the initially charged monomer or polymer branches to be grafted in the graft copolymerization reaction. The calculation formula is:

[0106] Grafting rate = [mass of grafted monomer / (mass of grafted monomer+mass of grafted monomer homopolymer)]*100%.

[0107] Bottom guard plate

[0108] The second aspect of the present application discloses a bottom protective plate of a secondary battery, wherein the bottom protective plate comprises an insulating layer having a groove therein, and the groove is filled with the insulating film according to the first aspect of the present application.

[0109] Figure 1 An example of a bottom guard plate is schematically shown, wherein the size and relative size of each part are exaggerated or reduced to clearly show the relative position relationship of each part. Figure 1 The bottom guard plate includes a bead 11 and an insulating layer 15. The insulating layer 15 has an opening 13. The opening 13 is located below the bead 11. The above-mentioned electrolyte-inresistant insulating film 12 is provided below the opening 13. The inverted battery cell 20 is supported by the bead 11, and the battery cell top cover 19 is partially in contact with the bead 11. The battery cell pole (not shown) is welded to the bar 17. The wiring harness isolation plate 18 separates the battery cell from the bottom guard plate to prevent the battery from short-circuiting. The MMP 16 is a foam material that plays a supporting role. The insulation detection device 10 electrically connects the battery top cover 19 and the metal plate 14 of the bottom guard plate.

[0110] By placing an electrolyte-intolerant insulating film 12 below the opening 13, electrolyte leakage can be dissipated through the insulating film, allowing the electrolyte to overlap the metal plate of the bottom guard plate, forming a conductive circuit between the cell top cover 19 and the metal plate 14, thereby achieving a rapid alarm. Furthermore, placing the opening 13 below the bead 11 can shorten the path of the electrolyte overlapping the metal plate of the bottom guard plate, thereby achieving a faster alarm.

[0111] secondary batteries

[0112] In addition, the secondary battery of the present application will be described below with reference to the drawings as appropriate.

[0113] In one embodiment of the present application, a secondary battery is provided. The secondary battery includes the bottom guard plate provided in the second aspect of the present application. In an optional embodiment, the secondary battery is a secondary battery with inverted cells.

[0114] The term "secondary battery" mentioned herein refers to a battery cell, a battery module, or a battery pack. Each of these is described below.

[0115] Typically, a secondary battery cell consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0116] The present application has no particular restrictions on the positive electrode sheet, negative electrode sheet, electrolyte and separator, and any liquid battery containing an organic electrolyte is applicable to the present invention.

[0117] In some embodiments, the electrolyte solution includes an electrolyte salt and a solvent.

[0118] The present application does not particularly limit the electrolyte salt and can be selected according to the specific battery type. In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0119] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0120] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0121] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0122] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0123] The bottom guard plate of the inverted-cell secondary battery includes the aforementioned insulating film and has an alarm circuit for the metal plate connecting the top cover and the bottom guard plate. By detecting the resistance in the circuit, an alarm can be generated in the event of electrolyte leakage. This application does not specifically limit the specific structure of the inverted-cell secondary battery.

[0124] In addition, the present application also provides an electrical device, which includes the secondary battery provided in the present application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0125] Figure 2 The power consumption device is taken as an example, and the power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0126] Example

[0127] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0128] The test methods involved in this application are as follows:

[0129] Tensile strength (MPa): tested using the standard ISO527-3 method;

[0130] Elongation at break (%): tested using the standard ISO 527-3 method.

[0131] PCT high temperature and high pressure aging test: The standard adopted is the GB / T362891-2018 method. The test conditions are: 0.2Mpa, relative humidity and 100% (121°C) for 8h, 12h or 24h. The data of a certain period of time under this test condition is equivalent to the data of a certain period of time under double 85 aging conditions. For example, 12 hours of PCT high temperature and high pressure aging is equivalent to 1000 hours of double 85 aging.

[0132] Double 85 accelerated aging test: The samples are placed at 85℃, 85% RH for 1000h or 1200h before subsequent testing.

[0133] Tensile strength (double 85 aging) (MPa): tested using ISO527-3 method, test conditions: test speed 50mm / min.

[0134] Elongation at break (double 85 aging) (%): tested using ISO527-3 method, test conditions: test speed is 10 mm / min.

[0135] Dissolution time (h): At a specific temperature, add electrolyte to an insulating film of a certain thickness, observe whether the insulating film dissolves, and record the dissolution time.

[0136] Melt flow rate (230°C, 2.16 kg) (g / 10 min): tested using the standard ISO 1133 method.

[0137] Withstand voltage leakage current (mA): tested according to IEC 60243. Test conditions: room temperature (25°C), test voltage: 2700VDC, test time: 60s.

[0138] Insulation resistance (MΩ): Tested using an insulation resistance meter in accordance with GB / T 31838.4-2019. Test voltage: 1000V DC, test time: 60s, test conditions: room temperature (25°C).

[0139] Test equipment:

[0140] Insulation resistance meter: Model TH9302, Manufacturer: Xiechuang Measurement

[0141] Micro-controlled electronic universal testing machine: Model: KT23, Manufacturer: Guangdong Qiya

[0142] Aging chamber: Model: HW-01, Manufacturer: Dongguan Aibo Instruments

[0143] The processing equipment used in the following examples:

[0144] Twin-screw extruder: Model: ZE26GP, Manufacturer: KraussMaffei

[0145] Multi-layer co-extrusion cast film stretching equipment: Model TR75AFS extruder, manufacturer: Bandera

[0146] Example 1

[0147] First film granulation: 50 parts by weight of PA6 (Xinhui Meida M3400), 30 parts by weight of polystyrene (HIPS476L), 10 parts by weight of a compatibilizer (Kateng FG1901), 10 parts by weight of a filler (talc), 0.2 parts by weight of an antioxidant (BSF 1076), and 0.5 parts by weight of a lubricant (Ethylene bisstearamide (EBS) from Guangzhou Kaiye) were added to a high-speed disperser and mixed for 120 seconds to produce a mixture. The mixture was then discharged from the main feed port and extruded through a twin-screw extruder to produce granules. The extruder temperature was controlled at 225°C. The extrusion granulation process parameters included: zone 1 temperature of 210°C, zone 2 temperature of 220°C, zone 3 temperature of 230°C, zone 4 temperature of 230°C, zone 5 temperature of 220°C, die head temperature of 225°C, and main engine speed of 300 rpm.

[0148] Insulation film: The granules and 50 μm thick polyester fiber cloth (100 mesh) were processed through a multi-layer coextrusion cast film stretching machine to produce a 0.25 mm thick insulation film product. The insulation film consisted of two layers of equal thickness, a first film, and an interlayer polyester fiber layer. The insulation film was produced using a single-screw extruder with the following process parameters: temperature: 225°C, extrusion film width: 1.25 cm.

[0149] Test Example 1: Dissolution Time Test

[0150] Electrolyte was dripped onto the film of Example 1 at various temperatures to conduct dissolution tests. The electrolyte used was RI9T2 electrolyte from Kaixin Battery. The state of the insulating film was visually observed, and the dissolution time was recorded in Table 1 below.

[0151] Table 1

[0152] Dissolution time 40℃ 25℃ 0℃ -10℃ -20℃ Example 1 15min 30min 75min 13h 15h

[0153] It can be seen from the above test results that the insulating film of Example 1 is not resistant to electrolyte dissolution, and has a short dissolution time at a temperature of 0-40° C., which can achieve a rapid alarm.

[0154] Test Example 2: PCT accelerated aging test

[0155] The film of Example 1 was subjected to performance tests at room temperature and after PCT aging for 12 hours and 24 hours, respectively. The test results are shown in Table 2 below.

[0156] Table 2

[0157]

[0158] The test results above demonstrate that after 24 hours of PCT aging, the mechanical properties of the insulating film of Example 1, such as tensile strength, elongation at break, and elastic modulus, show little change, demonstrating that the insulating film of Example 1 exhibits high aging resistance. Furthermore, after 24 hours of PCT aging, the insulating film of Example 1 exhibited a withstand voltage leakage current of less than 1 mA and an insulation resistance significantly greater than 500Ω, meeting the electrical performance requirements for insulating films used in underbody panels.

[0159] Example 2

[0160] First film granulation: 30 parts by weight of PA6 (Xinhui Meida M3400), 35 parts by weight of polystyrene (HIPS476L), 15 parts by weight of a compatibilizer (Katone FG1901), 19 parts by weight of a filler (talc), 0.2 parts by weight of an antioxidant (BSF 1076), 0.5 parts by weight of a lubricant (Guangzhou Kaiye, ethylene bisstearamide (EBS)) and 0.5 parts by weight of a masterbatch (Cabot 6269) were added to a high-speed dispersant, and the mixture was mixed and stirred for 120 seconds to obtain a mixture; the mixture was discharged from a main feeding port and extruded and granulated through a twin-screw extruder to obtain granules, wherein the extruder temperature was controlled at 225°C. The process parameters of extrusion granulation include: zone 1 temperature 210°C, zone 2 temperature 220°C, zone 3 temperature 230°C, zone 4 temperature 230°C, zone 5 temperature 220°C, die head temperature 225°C, and main engine speed 300 rpm.

[0161] Preparation of insulating film: The above-mentioned granulated material and polyester fiber cloth with a thickness of 25 μm are prepared into an insulating film product with a thickness of 0.5 mm through a multi-layer co-extrusion cast film stretching device, wherein the insulating film includes two layers of first film and an interlayer metal fiber layer, the thickness of the first film is 0.24 mm, and the thickness of the fiber layer is 0.025 mm.

[0162] Examples 3-9

[0163] The preparation methods of the insulating films of Examples 3-9 are similar to those of Example 2, except that the weight fractions of the components used are different. See Table 3 below for details.

[0164] Comparative Example 1

[0165] PA6 was not added to the components of the first film. The weight proportions of other components are detailed in Table 3. The film was prepared by referring to the preparation method of Example 2.

[0166] Comparative Example 2

[0167] No compatibilizer was added to the components of the first film. The weight percentages of other components are detailed in Table 3. The film was prepared by referring to the preparation method of Example 2.

[0168] The specific formulas of the insulating films of Examples 2-9 and Comparative Examples 1-2 are shown in Table 3 below, in parts by weight.

[0169] Table 3

[0170]

[0171] The insulation films of Examples 2-9 and Comparative Examples 1-2 were subjected to performance tests, and the test results are shown in Table 4 below.

[0172] Table 4

[0173]

[0174]

[0175] The test results above show that the insulating film of Comparative Example 1, which does not contain PA6, requires a longer dissolution time. The insulating film of Comparative Example 2 exhibits a significant decrease in tensile strength and elongation at break after aging with double 85, failing to meet technical requirements and exhibiting poor aging resistance. Examples 2-9 of the present application exhibit excellent resistance to double 85 aging and shorter dissolution times.

[0176] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An insulating film, characterized in that: The insulating film includes at least one first film, and the first film includes: 30-60 parts by weight of PA6; 15-40 parts by weight of polystyrene; 5-15 parts by weight of a compatibilizing agent; 10-20 parts by weight of filler.

2. The insulating film according to claim 1, wherein The amount of PA6 in the first film is 40-60 parts by weight; the amount of polystyrene is 15-35 parts by weight; and the amount of the compatibilizing agent is 10-15 parts by weight.

3. The insulating film according to claim 1 or 2, characterized in that: The melt index of PA6 in the first film is 3-10 g / 10 min under the test conditions of 2.16 kg and 230° C.

4. The insulating film according to any one of claims 1 to 3, characterized in that The polystyrene in the first film has a melt index of 3-10 g / min under test conditions of 2.16 kg and 230° C.

5. The insulating film according to any one of claims 1 to 4, characterized in that The compatibility aid comprises an olefin polymer grafted with maleic anhydride, wherein the grafting rate of maleic anhydride in the olefin polymer is 0.8%-2.0%.

6. The insulating film according to any one of claims 5, wherein The maleic anhydride grafted olefin polymer includes maleic anhydride grafted polypropylene-polyethylene copolymer and / or maleic anhydride grafted hydrogenated styrene-butadiene copolymer.

7. The insulating film according to any one of claims 1 to 6, characterized in that: The filler includes one or more inorganic fillers selected from the group consisting of silicon micropowder, talc, white carbon black, calcium carbonate, and calcium sulfate.

8. The insulating film according to any one of claims 1 to 7, characterized in that: The first film further comprises: 0.2-0.4 parts by weight of an antioxidant; 0.1-0.5 parts by weight of lubricant.

9. The insulating film according to any one of claims 8, wherein The lubricant includes at least one of erucamide, EBS amides, polyethylene wax, and silicone masterbatch.

10. The insulating film according to any one of claims 1 to 9, characterized in that: The first film further comprises: 0.5-2 parts by weight of masterbatch; and / or 10-20 parts by weight of polyester and / or polyamide fibers.

11. The insulating film according to any one of claims 1 to 10, characterized in that: The insulating film further includes at least one fiber layer, and the first film and the fiber layer are alternately arranged.

12. The insulating film according to claim 11, wherein The fiber layer includes polyester fibers and / or polyamide fibers.

13. The insulating film according to claim 11, wherein The fiber layer includes metal fibers or metal wires, and the materials of the metal fibers and the metal wires independently include at least one of copper, silver, gold, and platinum.

14. The insulating film according to any one of claims 11 to 13, characterized in that: The insulating film includes two layers of the first films and one layer of the fiber layer, wherein the fiber layer is located between the two layers of the first films.

15. The insulating film according to claim 13, wherein The insulating film further includes at least one second film, which is an electrolyte-resistant insulating film; the insulating film includes the first film, the fiber layer, and the second film arranged in sequence.

16. The insulating film according to any one of claims 11 to 15, characterized in that: The thickness of the fiber layer is 5 μm-50 μm.

17. The insulating film according to any one of claims 1 to 16, characterized in that: The thickness of the first film is 100 μm-475 μm.

18. The insulating film according to claim 1-17, characterized in that: The time it takes for the first film to be dissolved through by the electrolyte is ≤5h under the conditions of a thickness of 100μm-475μm and a temperature of 35±5°C.

19. A secondary battery, characterized in that: The secondary battery includes a bottom protective plate, which includes an insulating layer and a metal plate in contact with the insulating layer. The insulating layer has an opening that penetrates the thickness of the insulating layer. The side of the opening facing the metal plate is provided with an insulating film according to any one of claims 1-18 that closes the opening.

20. An electrical device, characterized in that: The secondary battery according to claim 19 is included.

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