Battery diaphragm, battery and electric equipment

Abstract

The invention relates to a battery diaphragm, a battery and electric equipment. The battery diaphragm comprises a base membrane, and a temperature-sensitive switch layer and a self-heating layer which are sequentially stacked on at least one surface of the base membrane, when the temperature is lower than the critical temperature, the conductivity of the battery diaphragm is more than 1 * 10 <-3 > S / cm; and the conductivity of the battery diaphragm is less than 1 * 10 <-4 > S / cm when the temperature is higher than the critical temperature. According to the diaphragm and the battery provided by the invention, heat can be quickly generated in a low-temperature environment to increase the temperature of the battery and improve the performance of the battery under the condition of not changing the conventional structure of a battery cell, and normal work of the battery at normal temperature and high temperature is not influenced.

Description

Technical Field

[0001] The present disclosure relates to the technical field of batteries, and particularly to a battery separator, a preparation method thereof, a battery, and an electrical device. Background Art

[0002] Lithium-ion batteries are widely used in fields such as electric vehicles and portable electronic devices due to advantages such as high energy density and long cycle life. However, in a low-temperature environment, the battery performance deteriorates significantly, such as an increase in battery internal resistance, a decrease in charge and discharge capacity, and a deterioration in rate performance. This is mainly because low temperature slows down the electrode reaction kinetics, reduces the ionic conductivity of the electrolyte, and hinders the transport of lithium ions between the positive and negative electrodes and the separator. Heating is an effective way to solve the problem of deterioration caused by too low operating environment temperature of the battery system. Currently, the commonly used battery heating methods include external heating and internal heating. The disadvantages of existing technical solutions include: (1) high energy consumption and slow response of external heating, low heating capacity and efficiency; (2) the internal heating scheme will change the internal structure of the battery itself, affect the energy density of the system, and the self-heating is uncontrollable, and there are thermal safety hazards at different temperatures. Summary of the Invention

[0003] The purpose of the present disclosure is to provide a battery separator, a preparation method thereof, a battery, and an electrical device, which can quickly generate heat to increase the battery temperature in a low-temperature environment, improve the battery performance, and do not affect the normal operation of the battery at normal temperature and high temperature without changing the conventional structure of the battery core.

[0004] To achieve the above purpose, in the first aspect of the present disclosure, a battery separator is provided, including a base film, and a temperature-sensitive switch layer and a self-heating layer sequentially stacked on at least one surface of the base film; When the temperature is below the critical temperature, the conductivity of the battery separator is 1×10 -3 S / cm or more; when the temperature is above the critical temperature, the conductivity of the battery separator is 1×10 -4 S / cm or less.

[0005] Optionally, the temperature-sensitive switch layer includes a temperature-sensitive polymer matrix and conductive particles distributed in the polymer matrix.

[0006] Optionally, the temperature-sensitive polymer in the temperature-sensitive switch layer includes one or more of poly(N-isopropylacrylamide) and its derivatives and polyhydric alcohols; Preferably, the derivative of poly(N-isopropylacrylamide) includes one or more of copolymers of N-isopropylacrylamide and acrylic acid compounds; more preferably, the acrylic acid compounds include one or more of acrylic acid, methyl methacrylate, ethyl acrylate, and butyl acrylate; more preferably, the copolymer includes one or more of N-isopropylacrylamide-acrylic acid copolymer, N-isopropylacrylamide-methyl methacrylate copolymer, N-isopropylacrylamide-ethyl acrylate copolymer, and N-isopropylacrylamide-butyl acrylate copolymer; more preferably, in the copolymer, the molar proportion of N-isopropylacrylamide structural units is 70-99 mol%, preferably 75-98 mol%; Optionally, the polyol includes one or both of polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer and polyethylene glycol-polyvinyl alcohol-polyethylene glycol triblock copolymer; Optionally, the molecular weight of the poly(N-isopropylacrylamide) is 10 4 ~10 5 g / mol; the molecular weight of the copolymer of N-isopropylacrylamide and acrylic acid compounds is 1×10 4 ~1.5×10 5 g / mol; the molecular weight of the polyol is 1×10 3 ~5×10 4 g / mol.

[0007] Optionally, the conductive particles in the thermosensitive switch layer include one or more of metal nanoparticles and conductive carbon materials; Optionally, the metal nanoparticles include one or more of silver nanoparticles, gold nanoparticles, and copper nanoparticles; The conductive carbon materials include one or more of conductive carbon black, graphene, carbon nanotubes, and activated carbon; Optionally, the particle size of the conductive particles is 1-100 nm, preferably 10-50 nm.

[0008] Optionally, in the thermosensitive switch layer, the weight ratio of the thermosensitive polymer to the conductive particles is 1-10:1, preferably 2-6:1.

[0009] Optionally, below the critical temperature, the porosity of the battery separator is 20-60%, preferably 30-50%; the surface pore size is 0.01-10 μm, preferably 0.01-1 μm; Above the critical temperature, the porosity of the battery separator is 30-80%, preferably 35-65%; the surface pore size is 0.001-1 μm, preferably 0.01-0.5 μm; Preferably, the critical temperature is 0 to -45°C, preferably -5 to -40°C.

[0010] Optionally, the self-heating layer includes a conductive heating material and a binder; Optionally, the conductive heating material includes one or more of carbon nanomaterials, metal nanowires, polyaniline, and conductive ceramics; Optionally, the carbon nanomaterials include one or more of carbon nanotubes and graphene nanosheets; optionally, the metal nanowires include one or more of silver nanowires, copper nanowires, and gold nanowires; Optionally, the binder includes a polymer binder; preferably, the polymer binder includes one or more of polyvinylidene fluoride, polyimide, polyvinyl alcohol, and polyvinyl chloride; optionally, the molecular weight of the polymer binder is 10 2 ~10 7 。

[0011] Optionally, based on the total weight of the self-heating layer, the content of the binder is 80 to 98% by weight, preferably 85 to 95% by weight; the content of the conductive heating material is 2 to 20% by weight, preferably 5 to 15% by weight.

[0012] Optionally, the thickness of the base film is 5 μm to 30 μm, preferably 7 μm to 25 μm; optionally, the material of the base film is selected from one or two of polyethylene and polypropylene; The single-sided thickness of the temperature-sensitive switch layer is 1 μm to 10 μm, preferably 1 to 5 μm; The single-sided thickness of the self-heating layer is 1 μm to 10 μm, preferably 1 to 5 μm; Preferably, the ratio of the single-sided thickness of the temperature-sensitive switch layer to the self-heating layer is 1:0.5 to 5, preferably 1:1 to 4; the ratio of the single-sided temperature-sensitive switch layer to the base film is 1:1 to 25, preferably 1:2 to 10; Optionally, the single-sided coating density of the temperature-sensitive switch layer is 1.0 to 5.0 g / m 2 ,the single-sided coating density of the self-heating layer is 1.0 to 5.0 g / m 2 。

[0013] Optionally, the battery separator further includes a coating layer; The coating layer is disposed on the surface of the self-heating layer away from the temperature-sensitive switch layer; and / or, the coating layer is disposed between the base film and the temperature-sensitive switch layer.

[0014] Optionally, the coating layer includes one or more of an organic coating and an inorganic coating; Optionally, the material of the organic coating includes one or more of polyvinylidene fluoride, polyimide, aramid, aramid sulfone, and polyacrylonitrile; the material of the inorganic coating includes one or more of alumina, boehmite, magnesium hydroxide, aluminum hydroxide, zirconia, and titanium dioxide; Preferably, based on the total weight of the battery separator, the content of the coating layer is 30 to 60% by weight, preferably 35 to 55% by weight; Optionally, the thickness of the coating layer is 1 μm to 5 μm, preferably 1 μm to 4 μm; the one-sided coating density of the coating layer is 1.0 to 10.0 g / m 2 , preferably 1.0 to 5.0 g / m 2 .

[0015] Optionally, at 25 °C, the total thickness of the battery separator is 7 μm to 35 μm, and the air permeability value is 100 to 300 s / 100 mL.

[0016] The second aspect of the present disclosure provides a battery, including the battery separator described in the first aspect of the present disclosure.

[0017] The third aspect of the present disclosure provides a battery, including the battery described in the second aspect of the present disclosure.

[0018] Through the above technical solutions, the present disclosure provides a battery separator and its preparation method, a battery, and an electrical device. At least one surface of the base film of the battery separator includes a stacked thermosensitive switch layer and a self-heating layer. When the internal temperature of the battery system is lower than the critical temperature, the conductivity of the battery separator is above 1×10 -3 S / cm. During the charge and discharge process, the conductivity and heat generation performance of the conductive heating material in the self-heating layer can be utilized. When an electric current passes through, Joule heat is generated, rapidly increasing the temperature of the separator and the battery system temperature, and improving the battery performance at low ambient temperatures; when the internal temperature of the battery system rises above the critical temperature, the conductivity of the battery separator is 1×10 -4Below 1 S / cm, the conductive path of the self-heating functional layer is cut off, thus ensuring the performance of the battery at higher temperatures. The present disclosure realizes self-heating by integrating a conductive heating material into the separator structure, without damaging the original structure of the battery or the battery cell, with simple process and low cost, and is suitable for large-scale industrial production and application; the temperature-sensitive switch layer of the low-temperature self-heating battery separator of the present disclosure can automatically control the on-off of the self-heating layer according to the change of the ambient temperature, ensuring that the battery automatically stops self-heating after reaching an appropriate temperature and avoiding safety problems caused by overheating; at the same time, the three-layer structure of the separator ensures that within the normal operating temperature range, the performance of the battery is not affected and the cycle life is comparable to that of a traditional separator battery; the low-temperature performance of the battery separator of the present disclosure is significantly improved: at -20°C, for a lithium-ion battery using the battery separator of the present disclosure, the discharge capacity increases and the internal resistance decreases, effectively improving the charge and discharge performance of the battery at low temperatures.

[0019] Other features and advantages of the present disclosure will be described in detail in the following specific implementation section. Brief Description of the Drawings

[0020] The drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification, and are used to explain the present disclosure together with the following specific implementation, but do not constitute a limitation to the present disclosure. In the drawings: Figure 1 It is a schematic structural diagram of the battery separator provided by the present disclosure.

[0021] Reference Signs: 1 - base film, 2 - self-heating layer, 3 - temperature-sensitive switch layer. Specific Embodiments

[0022] The following will detail the specific embodiments of the present disclosure. It should be understood that the specific embodiments described herein are only for explaining and understanding the present disclosure, and are not used to limit the present disclosure.

[0023] The first aspect of the present disclosure provides a battery separator, including a base film, and a temperature-sensitive switch layer and a self-heating layer sequentially stacked on at least one surface of the base film; When the temperature is below the critical temperature, the conductivity of the battery separator is 1×10 -3 S / cm or more; when the temperature is above the critical temperature, the conductivity of the battery separator is 1×10 -4 S / cm or less.

[0024] The present disclosure provides a battery separator, and a temperature-sensitive switch layer and a self-heating layer are stacked on at least one surface of the base film of the battery separator. When the internal temperature of the battery system is lower than the critical temperature, the conductivity of the battery separator is 1×10 - 3Above S / cm, during the charge and discharge process, the conductivity and heat generation performance of the conductive heat-generating material in the self-heating layer can be utilized. When current passes through, Joule heat is generated, rapidly increasing the temperature of the separator and the battery system temperature, and improving the battery performance at low ambient temperatures; when the internal temperature of the battery system rises above the critical temperature, the conductivity of the battery separator is 1×10 -4 S / cm or less, cutting off the conductive path of the self-heating functional layer, thus ensuring the performance of the battery at higher temperatures. The present disclosure realizes self-heating by integrating the conductive heat-generating material into the separator structure, without damaging the original structure of the battery or cell, with a simple process and low cost, suitable for large-scale industrial production and application; the temperature-sensitive switch layer of the low-temperature self-heating battery separator of the present disclosure can automatically control the on / off of the self-heating layer with the change of the ambient temperature, ensuring that the battery automatically stops self-heating after reaching the appropriate temperature, avoiding safety problems caused by overheating; at the same time, the three-layer structure of the separator ensures that within the normal operating temperature range, the various performances of the battery are not affected, and the cycle life is equivalent to that of a traditional separator battery; the low-temperature performance of the battery separator of the present disclosure is significantly improved: at -20°C, for a lithium-ion battery using the battery separator of the present disclosure, the discharge capacity increases and the internal resistance decreases, effectively improving the charge and discharge performance of the battery at low temperatures.

[0025] In the present disclosure, a temperature-sensitive switch layer and a self-heating layer can be provided on one surface of the base film, or a temperature-sensitive switch layer and a self-heating layer can be provided on each of the two surfaces of the base film.

[0026] In a specific embodiment, as Figure 1 shown, temperature-sensitive switch layers 3 and self-heating layers 2 are provided in a stacked manner on each of the two surfaces of the base film 1. It can be set as needed.

[0027] In the present disclosure, the "critical temperature" is based on the temperature within the battery system.

[0028] In a preferred embodiment, the temperature-sensitive switch layer includes a temperature-sensitive polymer matrix and conductive particles distributed in the polymer matrix; when the temperature within the battery system is lower than the critical temperature, the molecular chains of the temperature-sensitive polymer with temperature-sensitive characteristics in the temperature-sensitive switch layer automatically contract, and the conductive particles come into contact with each other to form a conductive path, such that the conductivity of the temperature-sensitive switch layer is 1×10 -3 S / cm or more; when the temperature within the battery system rises above the critical temperature, the molecular chains of the temperature-sensitive polymer with temperature-sensitive characteristics in the temperature-sensitive switch layer stretch, and the conductive particles are separated from each other, such that the conductivity of the temperature-sensitive switch layer is 1×10 -4 S / cm or less, cutting off the conductive path of the self-heating functional layer.

[0029] In one embodiment, the thermosensitive polymer in the thermosensitive switch layer includes one or more of poly(N-isopropylacrylamide) and its derivatives and polyhydric alcohols; the types of thermosensitive polymers in this embodiment have an effective response to temperature changes, and can effectively control the opening and closing of the conductive path above and below the critical temperature, improving the low-temperature performance of the battery and the safety of the battery at normal and high temperatures.

[0030] In one embodiment, the derivatives of poly(N-isopropylacrylamide) include one or more of copolymers of N-isopropylacrylamide and acrylic acid compounds; preferably, the acrylic acid compounds include one or more of acrylic acid, methyl methacrylate, ethyl acrylate, and butyl acrylate; preferably, the copolymers include one or more of N-isopropylacrylamide-acrylic acid copolymer, N-isopropylacrylamide-methyl methacrylate copolymer, N-isopropylacrylamide-ethyl acrylate copolymer, and N-isopropylacrylamide-butyl acrylate copolymer; The polyhydric alcohols include one or two of polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer and polyethylene glycol-polyvinyl alcohol-polyethylene glycol triblock copolymer; using the types of thermosensitive polymers provided in this embodiment can achieve a better thermosensitive self-switching effect.

[0031] In a specific embodiment, in the copolymer, the molar proportion of N-isopropylacrylamide structural units is 80-99 mol%, preferably 90-98 mol%; The molecular weight of the poly(N-isopropylacrylamide) is 1×10 4 ~10 5 g / mol; the molecular weight of the copolymer of N-isopropylacrylamide and acrylic acid compound is 1×10 4 ~1.5×10 5 g / mol; the molecular weight of the polyhydric alcohol is 1×10 3 ~5×10 4 g / mol. The thermosensitive polymer with the properties provided in this embodiment can ensure that the thermosensitive switch layer has an excellent thermosensitive self-switching effect.

[0032] In one embodiment, the conductive particles in the thermosensitive switch layer include one or more of metal nanoparticles and conductive carbon materials. The types of conductive particles provided in this embodiment have excellent conductive effects.

[0033] In a specific embodiment, the metal nanoparticles include one or more of silver nanoparticles, gold nanoparticles, and copper nanoparticles; The conductive carbon materials include one or more of conductive carbon black, graphene, carbon nanotubes, and activated carbon.

[0034] In a specific embodiment, the particle size of the conductive particles is 1 to 100 nm, preferably 10 to 50 nm. The conductive particles have good conductive effects and are easy to be uniformly dispersed.

[0035] In a preferred embodiment, in the thermosensitive switch layer, the weight ratio of the thermosensitive polymer to the conductive particles is 1 to 10:1, including but not limited to 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and the ranges formed by any two values; preferably 2 to 6:1. By controlling the weight ratio of the thermosensitive polymer to the conductive particles, the critical temperature of the thermosensitive switch layer can be adjusted. When the weight ratio of the thermosensitive polymer to the conductive particles is within the range of this embodiment, especially within the preferred range, the effect of the thermosensitive switch layer is better, and the performance of the battery is also effectively improved.

[0036] In one embodiment, when the temperature is below the critical temperature, the porosity of the battery separator is 20 to 60%, preferably 30 to 50%; the surface pore diameter is 0.01 to 10 μm (i.e., 10 nm to 10 μm), preferably 0.01 to 1 μm; when the temperature is above the critical temperature, the porosity of the battery separator is 30 to 80%, preferably 35 to 65%; the surface pore diameter is 0.001 to 1 μm (i.e., 1 nm to 1 μm), preferably 0.001 to 0.5 μm; the structure of the thermosensitive switch layer that shrinks or expands above and below the critical temperature provided by the present disclosure can ensure the opening and closing of the conductive path. In the battery separator of the present disclosure, since the porosity and pore diameter of the base film and the self-heating layer do not change significantly with temperature, while the porosity and pore diameter of the thermosensitive switch layer change significantly with temperature; therefore, the change trend of the thermosensitive switch layer can be represented by testing the overall porosity and pore diameter of the battery separator above and below the critical temperature.

[0037] In a specific embodiment, the critical temperature is 0 to -45 °C, preferably -5 to -40 °C. Controlling the critical temperature within the range of this embodiment, especially within the preferred range, can have the effect of improving the performance of the battery under general low-temperature conditions. The critical temperature can be obtained by testing with the temperature-Ohmic impedance method.

[0038] In one embodiment, the self-heating layer includes a conductive heating material and a binder.

[0039] In one embodiment, the conductive heating material in the self-heating layer includes one or more of carbon nanomaterials, metal nanowires, polyaniline, and conductive ceramics.

[0040] In a specific embodiment, the carbon nanomaterials include one or more of carbon nanotubes and graphene nanosheets; the metal nanowires include one or more of silver nanowires, copper nanowires, and gold nanowires. The conductive heating material provided by this embodiment has a high heating efficiency and can quickly increase the internal temperature of the battery from a low temperature (such as -20°C) to above 0°C, meeting the rapid start-up requirements of the battery.

[0041] In a specific embodiment, the binder includes a polymer binder; preferably, the polymer binder includes one or more of polyvinylidene fluoride, polyimide, polyvinyl alcohol, and polyvinyl chloride; optionally, the molecular weight of the polymer binder is 10 2 ~10 7 。

[0042] In a preferred embodiment, based on the total weight of the self-heating layer, the content of the binder is 80 to 98% by weight, including but not limited to 80% by weight, 82% by weight, 84% by weight, 86% by weight, 88% by weight, 90% by weight, 92% by weight, 94% by weight, 96% by weight, 98% by weight, and the range formed by any two values; preferably 85 to 95% by weight; the content of the conductive heating material is 2 to 20% by weight, preferably 5 to 15% by weight. By setting the self-heating layer according to the component content in this embodiment, especially according to the preferred component content, more excellent self-heating performance can be exerted, and the battery heating rate can be increased.

[0043] In one embodiment, the material of the base film is selected from one or more of polyethylene and polypropylene. The base film can adopt conventional types in the art.

[0044] In one embodiment, the thickness of the base film is 5 μm to 30 μm, including but not limited to 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, and the range formed by any two values; preferably 7 μm to 25 μm; The single-sided thickness of the temperature-sensitive switch layer is 1 μm to 10 μm, including but not limited to 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, and the range formed by any two values; preferably 1 to 5 μm; The single-sided thickness of the self-heating layer is 1 μm to 10 μm, including but not limited to 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, and the range formed by any two values; preferably 1 to 5 μm; When the single-sided thicknesses of the base film, the temperature-sensitive switch layer, and the self-heating layer are within the range of this embodiment, especially within the preferred range, it can play the role of improving the electrical performance of the system by low-temperature heating while taking into account normal operation at room temperature and high temperature.

[0045] In a preferred embodiment, the ratio of the thickness of the thermosensitive switch layer on one side to the self-heating layer is 1:0.5 to 5, including but not limited to 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, and the range composed of any two values; preferably 1:1 to 4; the ratio of the thickness of the thermosensitive switch layer on one side to the base film is 1:1 to 25, including but not limited to 1:1, 1:2, 1:4, 1:6, 1:8, 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, 1:22, 1:24, 1:25, and the range composed of any two values; preferably 1:2 to 10. The battery separator with the thickness ratio in this embodiment, especially with the preferred thickness ratio, can play the role of improving the electrical performance of the system by low-temperature heating while taking into account normal operation at room temperature and high temperature.

[0046] In one embodiment, the one-sided coating density of the thermosensitive switch layer is 1.0 to 5.0 g / m 2 , including but not limited to 1 g / m 2 , 2 g / m 2 , 3 g / m 2 , 4 g / m 2 , 5 g / m 2 and the range composed of any two values; preferably 1.5 to 4 g / m 2 ; the one-sided coating density of the self-heating layer is 1.0 to 5.0 g / m 2 , including but not limited to 1 g / m 2 , 2 g / m 2 , 3 g / m 2 , 4 g / m 2 , 5 g / m 2 and the range composed of any two values; preferably 1.5 to 4 g / m 2 . The thermosensitive switch layer and the self-heating layer with the coating density in this embodiment, especially the preferred coating density, can have excellent low-temperature heat generation effect.

[0047] In a specific embodiment, the battery separator can be prepared by a method including the following steps: S1. Coating the thermosensitive switch layer slurry on at least one surface of the base film through a first coating treatment, and then performing a first drying treatment to obtain a first product; the thermosensitive switch layer is provided on at least one surface of the base film in the first product; the thermosensitive switch layer solution includes a thermosensitive polymer, conductive particles, and a first solvent; the first coating treatment can adopt a spin coating method; S2. Coat the self-heating layer slurry on the surface of the temperature-sensitive switch layer of the first product through a second coating process, and then perform a second drying process to obtain a second product. At least one surface of the base film of the second product is provided with a temperature-sensitive switch layer and a self-heating layer arranged in a stacked manner; the self-heating layer slurry includes a conductive heating material, a binder, and a second solvent; the second coating process can adopt a doctor blade coating method.

[0048] In one embodiment, the first solvent includes one or more of ethanol, ethylene glycol, propylene glycol, and isopropyl alcohol; the second solvent includes one or more of N-methylpyrrolidone, N-ethylpyrrolidone, N-propylpyrrolidone, and dimethylformamide.

[0049] In one embodiment, in the temperature-sensitive switch layer slurry, the total content of the temperature-sensitive polymer and the conductive particles is 70-98% by weight, preferably 75-90% by weight; optionally, the weight ratio of the temperature-sensitive polymer to the conductive particles is 1-10:1, preferably 2-6:1; in the self-heating layer slurry, the total content of the conductive heating material and the binder is 70-98% by weight, preferably 75-90% by weight; optionally, the weight ratio of the conductive heating material to the binder is 1:1-20, preferably 1:1-10.

[0050] In a specific embodiment, the conditions of the first drying process include: the temperature is 50-90 °C, and the time is 0.5-6 h; the conditions of the second drying process include: the temperature is 60-120 °C, and the time is 0.5-6 h.

[0051] In a specific embodiment, in step S2, it further includes: dissolving the electrothermal material and the binder in the second solvent, and ultrasonically dispersing for 2-6 h to form the uniform self-heating layer slurry.

[0052] In a specific embodiment, the base film can be obtained through ordinary commercial channels or prepared by known methods. Including but not limited to: performing a melt extrusion process and a biaxial stretching process on the polymer raw material of the base film; the temperature of the melt extrusion can be adjusted according to the properties of the polymer raw material (for example, the melt extrusion temperature of polyethylene particles can be 140-200 °C, and the melt extrusion temperature of polypropylene can be 170-220 °C), and the conditions of the biaxial stretching process can be adjusted according to the required thickness of the base film.

[0053] In a specific embodiment, the battery separator further includes a coating layer; The coating layer is disposed on the surface of the self-heating layer away from the temperature-sensitive switch layer; and / or, the coating layer is disposed between the base film and the temperature-sensitive switch layer. The coating layer can be provided as needed, and has effects such as increasing thermal stability and improving the liquid absorption and retention capacity of the separator; in the present disclosure, the coating layer can be prepared by a conventional process.

[0054] In a specific embodiment, the coating layer includes one or more of an organic coating and an inorganic coating; Optionally, the material of the organic coating includes one or more of polyvinylidene fluoride, polyimide, aramid, polysulfone aramid, and polyacrylonitrile; the material of the inorganic coating includes one or more of alumina, boehmite, magnesium hydroxide, aluminum hydroxide, zirconia, and titanium dioxide; conventional types in the art can be used.

[0055] In a preferred embodiment, based on the total weight of the battery separator, the content of the coating layer is 30 to 60% by weight, including but not limited to 30% by weight, 35% by weight, 40% by weight, 45% by weight, 50% by weight, 55% by weight, 60% by weight, and the range composed of any two values; preferably 35 to 55% by weight; Optionally, the thickness of the coating layer is 1 μm to 5 μm, including but not limited to 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, and the range composed of any two values; preferably 1 μm to 4 μm; the single-sided coating density of the coating layer is 1.0 to 10.0 g / m 2 , including but not limited to 1 g / m 2 , 2 g / m 2 , 3 g / m 2 , 4 g / m 2 , 5 g / m 2 , 6 g / m 2 , 7 g / m 2 , 8 g / m 2 , 9 g / m 2 , 10 g / m 2 and the range composed of any two values; preferably 1.0 to 5.0 g / m 2 . Setting the coating layer according to this embodiment has effects such as increasing thermal stability and improving the liquid absorption and retention ability of the separator.

[0056] In a specific embodiment, under normal temperature test conditions (at 25 °C), the total thickness of the battery separator is 7 μm to 35 μm, including but not limited to 7 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, and the ranges formed by any two values; the porosity is 30% to 80%, including but not limited to 30%, 40%, 50%, 60%, 70%, 80%, and the ranges formed by any two values; the pore size is 1 nm to 10 μm, including but not limited to 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, and the ranges formed by any two values; the air permeability value is 100 to 300 s / 100 mL, including but not limited to 100 s / 100 mL, 150 s / 100 mL, 200 s / 100 mL, 250 s / 100 mL, 300 s / 100 mL, and the ranges formed by any two values; preferably, the total thickness of the battery separator is 8 μm to 30 μm, the porosity is 35% to 75%, the average pore size is 1 nm to 5 μm, and the air permeability value is 100 to 260 s / 100 mL.

[0057] The second aspect of the present disclosure provides a battery, including the battery separator described in the first aspect of the present disclosure.

[0058] The battery provided by the present disclosure includes but is not limited to metal ion batteries such as lithium ion batteries, sodium ion batteries, zinc ion batteries, calcium ion batteries, and magnesium ion batteries.

[0059] The battery provided by the present disclosure may also be a conventional structure in the art. In the present disclosure, the assembly of the battery may be a conventional process in the art. Specifically, the battery of the present disclosure may include a battery cell form, a battery module form, and a battery pack form. The battery cell includes a housing, an electrode core, and an electrolyte. The housing forms a receiving space, and the electrode core and the electrolyte are disposed in the receiving space. The electrode core may include a positive electrode, a negative electrode, and the battery separator. The positive electrode, the negative electrode, and the separator are arranged in a stacked or wound manner. In some embodiments, the battery cells may be assembled into a battery module. The number of battery cells included in the battery module may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module. In some embodiments, the battery module may further be assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack. The positive electrode, negative electrode, electrolyte, etc. of the battery of the present disclosure may be of conventional types in the art.

[0060] The third aspect of the present disclosure provides an electrical device, including the battery described in the second aspect of the present disclosure.

[0061] In the present disclosure, the electrical equipment may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, etc. The vehicle may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid electric vehicle or a range-extended electric vehicle, etc. The spacecraft includes an airplane, a rocket, a space shuttle, a spaceship, etc. The electric toy includes a fixed or mobile electric toy, for example, a game console, an electric vehicle toy, an electric ship toy, an electric airplane toy, etc.

[0062] In some embodiments, the electrical equipment is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical equipment for the battery, a battery pack or a battery module may be adopted.

[0063] The present disclosure will be further described in detail below through embodiments. The raw materials used in the embodiments can all be obtained through commercial channels.

[0064] In the following embodiments, the battery separator includes a base film, and a thermosensitive switch layer and a self-heating layer that are sequentially laminated on two surfaces of the base film; wherein, the single-sided thickness, coating surface density, composition and other parameters of the two thermosensitive switch layers are the same; the single-sided thickness, coating surface density, composition and other parameters of the two self-heating layers are also the same.

[0065] In the following embodiments and comparative examples, the porosity (P) of the battery separator is calculated by the following formula (1): P=(1-m / (ρ×V))×100% formula (1); In formula (1): P represents the porosity of the sample, in %; m represents the measured mass of the sample, unit: g; V represents the volume of the sample, in mm 3 ; ρ represents the true density of polyolefin (including polyethylene and / or polypropylene), wherein, the true density value of polyethylene is 0.96 g / m 3 , and the true density value of polypropylene is 0.905 g / m 3 (select the corresponding ρ value based on the type of the base film); The average pore size of the battery separator is measured by a bubble pressure method pore size analyzer; The air permeability value of the battery separator is measured by a Wang Yan air permeability meter.

[0066] Example 1 (1) Preparation of the base film: Melting and extruding polyethylene particles at 150 °C, and making a polyethylene base film with a thickness of 12 μm through a biaxial stretching process; (2) Preparation of the thermosensitive switch layer: Poly(N-isopropylacrylamide) (a thermosensitive polymer with a molecular weight of 20,000) and silver nanoparticles (conductive particles with a particle size of 38 nm) were mixed at a mass ratio of 5:1 and dissolved in ethanol (the first solvent) to form a thermosensitive switch layer slurry. The solution was coated on the base film layer (both surfaces were coated) by spin coating (the first coating treatment), and dried at 60 °C (the first drying treatment) to form a thermosensitive switch layer with a single-sided thickness of 2 μm; (3) Preparation of the self-heating layer: 10 g of carbon nanotubes (conductive heating material) and 90 g of polyvinylidene fluoride (binder with a molecular weight of 100,000) were dissolved in N-methylpyrrolidone (the second solvent), and ultrasonically dispersed for 2 hours to form a uniform slurry (self-heating layer slurry). The slurry was coated on the surface of the thermosensitive switch layer (the surface of each thermosensitive switch layer on both sides of the base film was coated) by knife coating (the second coating treatment), and dried at 80 °C (the second drying treatment) to form a self-heating functional layer with a single-sided thickness of 2 μm.

[0067] Example 2 (1) Preparation of the base film: Polypropylene was used, melt-extruded and uniaxially stretched at 160 °C to prepare a polypropylene base film with a thickness of 12 μm; (2) Preparation of the thermosensitive switch layer: A copolymer of poly(N-isopropylacrylamide) and methyl methacrylate (a thermosensitive polymer with a molecular weight of 34,000, and the molar proportion of N-isopropylacrylamide structural units in the copolymer was 78 mol%) and gold nanoparticles (conductive particles with a particle size of 43 nm) were mixed at a mass ratio of 4:1 and dissolved in ethanol (the first solvent) to form a thermosensitive switch layer solution. The solution was coated on the base film layer (both surfaces were coated) by spin coating (the first coating treatment), and dried at 70 °C (the first drying treatment) to form a thermosensitive switch layer with a single-sided thickness of 2 μm; (3) Preparation of the self-heating layer: 15 g of graphene nanosheets (conductive heating material) and 85 g of polyvinylidene fluoride (binder with a molecular weight of 100,000) were dissolved in N-methylpyrrolidone (the second solvent), and ultrasonically dispersed for 3 hours to form a uniform slurry (self-heating layer slurry). The slurry was coated on the thermosensitive switch layer (the surface of each thermosensitive switch layer on both sides of the base film was coated) by knife coating (the second coating treatment), and dried at 90 °C (the second drying treatment) to form a self-heating functional layer with a single-sided thickness of 2 μm.

[0068] Examples 3 to 13 Referring to the preparation method in Example 1, the differences from Example 1 are as follows: The battery separator was prepared according to the conditions listed in Tables 1 to 3 below, and the rest of the process was the same as that in Example 1.

[0069] Example 14 Referring to the preparation method in Example 1, the difference from Example 1 is as follows: The thermosensitive polymer (poly(N-isopropylacrylamide)) in the thermosensitive switch layer is replaced with a polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer (molecular weight of 25000), and the remaining process is the same as that in Example 1.

[0070] Example 15 Referring to the preparation method in Example 1, the difference from Example 1 is as follows: Coating layers are respectively provided on the surfaces of the two self-heating layers away from the thermosensitive switch layer, including the following steps: spraying alumina powder slurry with a D50 particle size of 800 nm onto the surface of the self-heating layer to form an inorganic ceramic coating; based on the total weight of the battery separator, the content of the coating layer is 36% by weight; The thickness of the coating layer is 2.0 μm; the single-sided coating density of the coating layer is 3.0 g / m 2 .

[0071] Comparative Example 1 A traditional polypropylene separator (purchased from Xingyuan New Materials Technology Co., Ltd.) with a thickness of 16 μm is used.

[0072] Comparative Example 2 This comparative example refers to the preparation method in Example 1, and the difference from Example 1 is as follows: The thermosensitive switch layer is not provided, and the self-heating layer is directly attached to the base film; the remaining process is the same as that in Example 1.

[0073] The structural parameters of each functional layer of the battery separator and data such as separator properties in the above examples and comparative examples are listed in Tables 1 to 3 below.

[0074] Table 1

[0075] Table 2

[0076] Table 3

[0077] Test Example 1 The critical temperature of the temperature-sensitive switch layer obtained by the above diaphragm preparation process, as well as the conductivity and structural parameters above and below the critical temperature, were tested. The method for testing the critical temperature is as follows: Cut out a diaphragm sample of appropriate size (100 mm in length and 100 mm in width), and place it in a thermostatic chamber that can precisely control the temperature; Connect the two ends of the diaphragm to the test leads of a digital multimeter to ensure good contact. Set the starting temperature of the heating device to -30 °C, and let the sample stabilize at this temperature for 10 min to allow the diaphragm to reach thermal equilibrium, and record the resistance value at this time. Slowly increase the temperature at a rate of 0.5 °C / min, and record the temperature and the corresponding resistance value every 1 minute. Observe the change in the resistance value. When the resistance value undergoes an obvious mutation, record the temperature at this time, which is taken as the critical temperature at which the temperature-sensitive switch layer conducts. The above operations were repeated three times and the average value was taken to obtain the critical temperature of the diaphragm sample.

[0078] The porosity of the battery diaphragm above and below the critical temperature was calculated as follows: Weigh a sample of a certain volume using an electronic balance; Then calculate via the formula: P=(1 - m / (ρ×V))×100%; where P represents the porosity of the specimen, in %; m represents the measured mass of the specimen, in g; V represents the volume of the specimen, in mm 3 ; ρ represents the true density of polyolefin (including polyethylene and / or polypropylene), where the true density value of polyethylene is 0.96 g / m 3 , and the true density value of polypropylene is 0.905 g / m 3 ; The pore size was obtained by testing with a pore size analyzer; The conductivity was obtained by testing with a conductivity tester. The test results are listed in Table 4 below.

[0079] Table 4

[0080] It can be seen from the data in Table 4 that: The battery diaphragm of Comparative Example 1 is a traditional polypropylene diaphragm, and the battery diaphragm of Comparative Example 2 does not have a temperature-sensitive switch layer. The battery diaphragms in Comparative Examples 1 - 2 do not have a temperature mutation point, that is, there is no critical temperature; The battery diaphragms provided in Examples 1 - 15 have a critical temperature at which the conductivity undergoes a mutation. Below the critical temperature, the conductivity of the battery diaphragm is relatively high, achieving a conductive path; While above the critical temperature, the porosity and pore size of the battery diaphragm are significantly higher than those below the critical temperature, and the conductivity is also lower than 10 -4 , indicating that when the temperature in the battery system rises above the critical temperature, the polymer unfolds and closes the conductive path; Comparing Examples 3 - 4 with Examples 5 - 6, in Examples 3 - 4, the weight ratio of the thermosensitive polymer to the conductive particles in the thermosensitive switch layer is within the optimized range provided by the present disclosure (1 - 10:1). The critical temperature of Examples 3 - 4 is higher than that of Examples 5 - 6, indicating that the thermosensitive switch layer of Examples 3 - 4 is more sensitive to low temperatures. As the ambient temperature decreases, the thermosensitive switch layer of Examples 3 - 4 can achieve self - heating earlier; and the conductivity below the critical temperature of Examples 3 - 4 is higher, with better conductivity. Comparing Examples 3 - 4 with Example 1, in Example 1, the weight ratio of the thermosensitive polymer to the conductive particles in the thermosensitive switch layer is within the further preferred range provided by the present disclosure (2 - 6:1). The critical temperature in Example 1 is higher than that of Examples 3 - 4, indicating that the low - temperature heating performance of the thermosensitive switch layer in Example 1 is better; and the conductivity below the critical temperature of the thermosensitive switch layer in Example 1 is higher, with better conductivity. Comparing Example 1 with Examples 11 - 12, in Example 1, the ratio of the single - sided thermosensitive switch layer to the base film thickness is within the preferred range provided by the present disclosure (1:2 - 10). The critical temperature of Example 1 is higher than that of Examples 11 - 12, indicating that the thermosensitive switch layer in Example 1 is more sensitive to low temperatures and has better low - temperature heating performance; and the conductivity of the thermosensitive switch layer in Example 1 at the critical temperature is higher, with better conductivity. Comparing Example 1 with Example 13, the single - sided coating density of the thermosensitive switch layer in Example 1 is within the preferred range provided by the present disclosure (1.5 - 4 g / m 2 ). The critical temperature in Example 1 is higher than that of Example 13, indicating that the thermosensitive switch layer in Example 1 is more sensitive to low temperatures and has better low - temperature heating performance; and the conductivity below the critical temperature in Example 1 is higher, with better conductivity.

[0081] Battery test examples The battery diaphragms obtained from the above examples and comparative examples were assembled into batteries according to the following steps: Using lithium iron phosphate as the positive electrode material, graphite as the negative electrode material, and a 1 mol / L solution of lithium hexafluorophosphate in carbonate as the electrolyte, the prepared battery diaphragm was assembled with the positive and negative electrode sheets into a lithium - ion battery.

[0082] At room temperature (25°C) and low temperature (-20°C) environments, charge - discharge tests were respectively carried out on the batteries. The test methods and conditions include: 0.5C discharge capacity: With a fixture, under a restraint force of 2000 N, charge at 0.5C CCCV (constant current constant voltage) to 3.8 V, and discharge at 0.5C CC (constant current) to 2.0 V, cycle three times, and take the last discharge capacity as the 0.5C discharge capacity; Battery internal resistance DCR test: The DCR value is obtained according to the ratio of the change in the last discharge voltage ΔV to the current.

[0083] The test results are listed in Table 5 below.

[0084] Table 5

[0085] It can be seen from the data in Table 5 that: The battery separator of Comparative Example 1 is a traditional polypropylene separator, and the battery separator of Comparative Example 2 does not have a thermosensitive switch layer. The 0.5C discharge capacity / room temperature capacity of the separators obtained in Comparative Examples 1-2 is relatively low, the increase rate of the battery internal resistance DCR is relatively high, and the battery temperature rise in 2.5 minutes is also relatively low; compared with Comparative Examples 1-2, the batteries using the battery separators provided in Examples 1-15 of the present disclosure have better battery performance and temperature rise performance at low temperatures; Comparing Examples 3-4 with Examples 5-6, the weight ratio of the thermosensitive polymer to the conductive particles in the thermosensitive switch layer in Examples 3-4 is within the optimized range provided by the present disclosure (1-10:1). The 0.5C discharge capacity / room temperature capacity of the lithium-ion batteries using the battery separators of Examples 3-4 is higher, the increase rate of the battery internal resistance DCR is lower, and the battery temperature rise in 2.5 minutes is higher, indicating that the batteries using the separators obtained in Examples 3-4 have better battery performance and temperature rise performance at low temperatures; Comparing Examples 3-4 with Example 1, the weight ratio of the thermosensitive polymer to the conductive particles in the thermosensitive switch layer in Example 1 is within the further preferred range provided by the present disclosure (2-6:1). The 0.5C discharge capacity / room temperature capacity of the lithium-ion batteries using the battery separator of Example 1 is higher, the increase rate of the battery internal resistance DCR is lower, and the battery temperature rise in 2.5 minutes is higher, indicating that the batteries using the separator obtained in Example 1 have better battery performance and temperature rise performance at low temperatures; Comparing Example 1 with Examples 7-8, the contents of the binder and the conductive heating material in the self-heating layer in Examples 7-8 are within the preferred range provided by the present disclosure (85-95 wt% binder and 5-15 wt% conductive heating material). The 0.5C discharge capacity / room temperature capacity of the lithium-ion batteries using the battery separator in Example 1 is higher, the increase rate of the battery internal resistance DCR is lower, and the battery temperature rise in 2.5 minutes is higher, indicating that the batteries using the separator obtained in Example 1 have better battery performance and temperature rise performance at low temperatures; Comparing Example 1 with Examples 9 - 10, for the single-sided thermosensitive switch layer: single-sided self-heating layer thickness ratio in Example 1 is within the preferred range provided in the present disclosure (1:1 - 4). The 0.5C discharge capacity / room temperature capacity of the lithium-ion battery using the battery separator in Example 1 is higher, the increase rate of the battery internal resistance DCR is lower, and the battery temperature rise in 2.5 min is higher, indicating that the battery using the separator obtained in Example 1 has better battery performance and temperature rise performance at low temperatures; Comparing Example 1 with Examples 11 - 12, for the single-sided thermosensitive switch layer: base film thickness ratio of the battery separator in Example 1 is within the preferred range provided in the present disclosure (1:2 - 10). The 0.5C discharge capacity / room temperature capacity of the lithium-ion battery using the battery separator in Example 1 is higher, the increase rate of the battery internal resistance DCR is lower, and the battery temperature rise in 2.5 min is higher, indicating that the battery using the separator obtained in Example 1 has better battery performance and temperature rise performance at low temperatures; Comparing Example 1 with Example 13, the single-sided coating density of the thermosensitive switch layer and the single-sided coating density of the self-heating layer in Example 1 are both within the preferred range provided in the present disclosure (both within the range of 1.5 - 4 g / m 2 range). The 0.5C discharge capacity / room temperature capacity of the lithium-ion battery using the battery separator in Example 1 is higher, the increase rate of the battery internal resistance DCR is lower, and the battery temperature rise in 2.5 min is higher, indicating that the battery using the separator obtained in Example 1 has better battery performance and temperature rise performance at low temperatures.

[0086] The preferred embodiments of the present disclosure have been described in detail above. However, the present disclosure is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0087] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, they can be combined in any suitable manner without conflict. To avoid unnecessary repetition, the present disclosure will not describe various possible combination methods separately.

[0088] Furthermore, any combination can be made among various different embodiments of the present disclosure, as long as it does not violate the idea of the present disclosure, and it should also be regarded as the content disclosed by the present disclosure.

Claims

1. A battery separator, characterized in that, It includes a base film, and a thermosensitive switch layer and a self-heating layer that are sequentially stacked on at least one surface of the base film; When the temperature is below the critical temperature, the conductivity of the battery separator is 1×10 -3 S / cm or more; when the temperature is above the critical temperature, the conductivity of the battery separator is 1×10 -4 S / cm or less.

2. The battery separator according to claim 1, characterized in that, The thermosensitive switch layer includes a thermosensitive polymer matrix and conductive particles distributed in the polymer matrix.

3. The battery separator according to claim 2, characterized in that, The thermosensitive polymer in the thermosensitive switch layer includes one or more of poly(N-isopropylacrylamide) and its derivatives and polyhydric alcohols; Preferably, the derivatives of poly(N-isopropylacrylamide) include one or more of copolymers of N-isopropylacrylamide and acrylic acid compounds; Further preferably, the acrylic acid compounds include one or more of acrylic acid, methyl methacrylate, ethyl acrylate, and butyl acrylate; Further preferably, the copolymers include one or more of N-isopropylacrylamide-acrylic acid copolymer, N-isopropylacrylamide-methyl methacrylate copolymer, N-isopropylacrylamide-ethyl acrylate copolymer, and N-isopropylacrylamide-butyl acrylate copolymer; Further preferably, in the copolymer, the molar proportion of the N-isopropylacrylamide structural unit is 70-99 mol%, preferably 75-98 mol%; Optionally, the polyhydric alcohol includes one or two of polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer and polyethylene glycol-polyvinyl alcohol-polyethylene glycol triblock copolymer; Optionally, the molecular weight of the poly(N-isopropylacrylamide) is 10 4 ~10 5 g / mol; the molecular weight of the copolymer of N-isopropylacrylamide and an acrylic acid compound is 1×10 4 ~1.5×10 5 g / mol; the molecular weight of the polyol is 1×10 3 ~5×10 4 g / mol.

4. The battery separator according to claim 2, characterized in that, The conductive particles in the thermosensitive switch layer include one or more of metal nanoparticles and conductive carbon materials; Optionally, the metal nanoparticles include one or more of silver nanoparticles, gold nanoparticles, and copper nanoparticles; The conductive carbon materials include one or more of conductive carbon black, graphene, carbon nanotubes, and activated carbon; Optionally, the particle size of the conductive particles is 1-100 nm, preferably 10-50 nm.

5. The battery separator according to claim 2, characterized in that, In the thermosensitive switch layer, the weight ratio of the thermosensitive polymer to the conductive particles is 1-10:1, preferably 2-6:

1.

6. The battery separator according to claim 1, characterized in that, Below the critical temperature, the porosity of the battery separator is 20-60%, preferably 30-50%; the surface pore size is 0.01-10 μm, preferably 0.01-1 μm; Above the critical temperature, the porosity of the battery separator is 30-80%, preferably 35-65%; the surface pore size is 0.001-1 μm, preferably 0.01-0.5 μm; Preferably, the critical temperature is 0 to -45 °C, preferably -5 to -40 °C.

7. The battery separator according to claim 1, characterized in that, The self-heating layer includes a conductive heating material and a binder; Optionally, the conductive heating material includes one or more of carbon nanomaterials, metal nanowires, polyaniline, and conductive ceramics; Optionally, the carbon nanomaterials include one or more of carbon nanotubes and graphene nanosheets; Optionally, the metal nanowires include one or more of silver nanowires, copper nanowires, and gold nanowires; Optionally, the binder includes a polymer binder; preferably, the polymer binder includes one or more of polyvinylidene fluoride, polyimide, polyvinyl alcohol, and polyvinyl chloride; optionally, the molecular weight of the polymer binder is 10 2 ~10 7 .

8. The battery separator according to claim 7, wherein Based on the total weight of the self-heating layer, the content of the binder is 80-98% by weight, preferably 85-95% by weight; the content of the conductive heating material is 2-20% by weight, preferably 5-15% by weight.

9. The battery separator according to claim 1, wherein The thickness of the base film is 5 μm to 30 μm, preferably 7 μm to 25 μm; optionally, the material of the base film is selected from one or both of polyethylene and polypropylene; The single-sided thickness of the temperature-sensitive switch layer is 1 μm to 10 μm, preferably 1 to 5 μm; The single-sided thickness of the self-heating layer is 1 μm to 10 μm, preferably 1 to 5 μm; Preferably, the ratio of the single-sided thickness of the temperature-sensitive switch layer to the self-heating layer is 1:0.5 to 5, preferably 1:1 to 4; the ratio of the single-sided temperature-sensitive switch layer to the base film is 1:1 to 25, preferably 1:2 to 10; Optionally, the single-sided coating density of the temperature-sensitive switch layer is 1.0~5.0 g / m 2 , and the single-sided coating density of the self-heating layer is 1.0~5.0 g / m 2 .

10. The battery separator according to claim 1, characterized in that, The battery separator further includes a coating layer; The coating layer is disposed on the surface of the self-heating layer away from the temperature-sensitive switch layer; and / or, the coating layer is disposed between the base film and the temperature-sensitive switch layer.

11. The battery separator according to claim 10, characterized in that, The coating layer includes one or more of an organic coating and an inorganic coating; Optionally, the material of the organic coating includes one or more of polyvinylidene fluoride, polyimide, aramid, arsulfone aramid, and polyacrylonitrile; the material of the inorganic coating includes one or more of alumina, boehmite, magnesium hydroxide, aluminum hydroxide, zirconia, and titanium dioxide; Preferably, based on the total weight of the battery separator, the content of the coating layer is 30 to 60% by weight, preferably 35 to 55% by weight; Optionally, the thickness of the coating layer is 1 μm to 5 μm, preferably 1 μm to 4 μm; the single-sided coating density of the coating layer is 1.0 to 10.0 g / m 2 , preferably 1.0 to 5.0 g / m 2 .

12. The battery separator according to claim 1, wherein At 25 °C, the total thickness of the battery separator is 7 μm to 35 μm, and the air permeability value is 100 to 300 s / 100 mL.

13. A battery, characterized in that, Comprising the battery separator according to any one of claims 1 to 12.

14. An electrical device, characterized in that, Comprising the battery according to claim 13.

Images