Isolating membrane and preparation method thereof, battery and electric equipment

Abstract

The invention discloses an isolating membrane and a preparation method thereof, a battery and electric equipment, the isolating membrane comprises an elastic material, and the Young modulus of the elastic material is greater than or equal to 1TPa. The elastic material with high Young modulus is added into the isolating membrane, so that the cycle performance and the energy conversion efficiency of the secondary battery containing the isolating membrane are improved.

Description

Technical Field

[0001] This application belongs to the technical field of secondary batteries, and particularly relates to a separator, a preparation method thereof, a battery and an electrical device. Background Art

[0002] Secondary batteries are not only applied to energy storage power systems such as hydroelectric, thermal, wind and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles and electric cars, as well as in many fields such as military equipment and aerospace.

[0003] The separator is an important component of a secondary battery. However, under overvoltage conditions, the existing separator is prone to change from elastic deformation to plastic deformation. The aperture diameter and number of pores on the separator decrease with the increase of pressure, blocking the pores, and the passage of active metal ions is hindered, resulting in a reduction in the cycle performance and energy conversion efficiency of the battery containing it. Summary of the Invention

[0004] In view of the technical problems in the background art, this application provides a separator, aiming to solve the problems of poor cycle performance and low energy conversion efficiency of the battery containing it.

[0005] To achieve the above object, in a first aspect of this application, a separator is provided, the separator includes an elastic material, and the Young's modulus of the elastic material is greater than or equal to 1 TPa.

[0006] This application has at least the following beneficial effects: In this application, an elastic material with a high Young's modulus is added to the separator, improving the ability of the separator to resist deformation, so that during the use of the battery, under different pressures, the separator can exhibit elastic deformation and quickly return to its original state after the pressure is removed, reducing the reduction of the aperture diameter of the pores on the separator and reducing the occurrence of closed pores, enabling the normal transmission of active metal ions, and improving the cycle performance and energy conversion efficiency of the secondary battery containing it.

[0007] In some embodiments of this application, the Young's modulus of the elastic material is 1 TPa - 5.5 TPa, optionally 1.8 - 5.5 TPa, and further optionally 4.5 - 5.5 TPa. Thereby, the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0008] In some embodiments of this application, the tensile strength of the elastic material is 50 GPa - 200 GPa, optionally 170 GPa - 200 GPa. Thereby, the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0009] In some embodiments of the present application, based on the total mass of the separator membrane, the mass proportion of the elastic material is 0.1% - 1%, and optionally 0.1% - 0.5%. Thereby, the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0010] In some embodiments of the present application, the elastic material includes at least one of carbon nanotube springs or graphene sponges. Thereby, the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0011] In some embodiments of the present application, the separator membrane includes a first membrane layer and a second membrane layer provided on at least one side of the first membrane layer, and the first membrane layer includes the elastic material. Thereby, the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0012] In some embodiments of the present application, the second membrane layers are provided on both sides of the first membrane layer. Thereby, the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0013] In some embodiments of the present application, the thickness ratio of the first membrane layer to the second membrane layer is (1.5 - 17.5):1, and optionally (2.5 - 10):1. Thereby, the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0014] In some embodiments of the present application, the thickness of the first membrane layer is 15 μm - 35 μm, and optionally 20 μm - 30 μm. Thereby, the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0015] In some embodiments of the present application, the thickness of the second membrane layer is 2 μm - 10 μm, and optionally 3 μm - 8 μm. Thereby, the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0016] In some embodiments of the present application, the porosity of the separator membrane is 40% - 80%, and optionally 60% - 80%. Thereby, the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0017] The second aspect of the present application provides a method for preparing a separator membrane, including:

[0018] Preparing a separator membrane including an elastic material, and the Young's modulus of the elastic material is 1 TPa - 5.5 TPa.

[0019] Thereby, by using the method of the present application, when preparing the separator membrane, an elastic material is added, which reduces the reduction of the pore diameter on the separator membrane and reduces the occurrence of closed pore phenomena, enabling the normal transmission of active metal ions and improving the cycle performance and energy conversion efficiency of the secondary battery containing it.

[0020] In some embodiments of the present application, the elastic material is prepared by the following method:

[0021] Mix the elastic material precursor solution with a dispersant, centrifuge to discard the supernatant, and perform solvothermal treatment to remove the dispersant, obtaining an intermediate;

[0022] Dry the intermediate and calcine it under air isolation to obtain the elastic material.

[0023] Thus, the elastic material prepared by the above method, when used in the separator membrane, can improve the cycling performance and energy conversion efficiency of the secondary battery.

[0024] In some embodiments of the present application, the volume ratio of the dispersant to the elastic material precursor solution with a concentration of 1.5 mg·mL -1 is (15 - 30):1, and can be optionally (20 - 30):1. Thus, by limiting the ratio of the dispersant to the elastic material precursor, the obtained elastic material, when used in the separator membrane, can improve the cycling performance and energy conversion efficiency of the secondary battery.

[0025] In some embodiments of the present application, the rotation speed of the centrifugation is 8000 r / min - 15000 r / min, and can be optionally 10000 r / min - 15000 r / min. Thus, within the above centrifugation rotation speed range, an intermediate with a uniform particle size distribution is obtained, which is beneficial to improving the Young's modulus of the obtained elastic material and can improve the cycling performance and energy conversion efficiency of the secondary battery.

[0026] In some embodiments of the present application, the temperature of the solvothermal treatment is 150°C - 250°C, and can be optionally 150°C - 200°C. Within the above temperature range, it is beneficial to improving the Young's modulus of the obtained elastic material and can improve the cycling performance and energy conversion efficiency of the secondary battery.

[0027] In some embodiments of the present application, the heating rate of the calcination is 1°C / min - 10°C / min, and can be optionally 3°C / min - 8°C / min. Thus, the Young's modulus of the obtained elastic material can be improved, and the cycling performance and energy conversion efficiency of the secondary battery can be improved.

[0028] In some embodiments of the present application, the temperature of the calcination is 300°C - 500°C, and can be optionally 350°C - 450°C. Thus, the Young's modulus of the obtained elastic material can be improved, and the cycling performance and energy conversion efficiency of the secondary battery can be improved.

[0029] In some embodiments of the present application, the time of the calcination is 0.5 h - 3 h, and can be optionally 0.5 h - 1.5 h. Thus, the stability of the pores of the separator membrane can be improved, and the cycling performance and energy conversion efficiency of the secondary battery can be improved.

[0030] In some embodiments of the present application, it includes: preparing a first film layer, where the first film layer includes the elastic material; preparing a second film layer on at least one side of the first film layer. Thereby, the Young's modulus of the obtained elastic material can be increased, and the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0031] In some embodiments of the present application, the first film layer is prepared by electrospinning. Thereby, the stability of the pores of the separator can be improved, and the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0032] The third aspect of the present application provides a battery, which includes the separator of the first aspect of the present application or the separator prepared by the method described in the second aspect of the present application. Thereby, the battery has excellent cycle performance and energy conversion efficiency.

[0033] The fourth aspect of the present application provides an electrical device, which includes the battery described in the third aspect.

[0034] The additional aspects and advantages of the present application will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present application. Description of the Drawings

[0035] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0036] Figure 1 is a schematic structural diagram of a battery according to an embodiment of the present application;

[0037] Figure 2 is a schematic structural diagram of a battery module according to an embodiment of the present application;

[0038] Figure 3 is a schematic structural diagram of a battery pack according to an embodiment of the present application;

[0039] Figure 4 is Figure 3 exploded view of;

[0040] Figure 5 is a schematic diagram of an embodiment of an electrical device using the battery as a power source.

[0041] Description of the Reference Numerals:

[0042] 1: Battery pack; 2: Upper box body; 3: Lower box body; 4: Battery module; 5: Battery cell. Detailed implementation manners

[0043] The embodiments of the technical solutions of the present application will be described in detail below. The following embodiments are only used to illustrate the technical solutions of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0044] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments may be included in at least one embodiment of the present application. The phrase appears at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein may be combined with other embodiments.

[0045] For the sake of brevity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, each separately disclosed point or single numerical value itself can be used as a lower limit or an upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recited.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0047] With the technological development and demand improvement of electric vehicles and rechargeable mobile devices, secondary batteries, as representatives in the new energy field, have also witnessed rapid development in related research work. Secondary batteries have a small volume and weight, making them convenient to carry and use; they have a relatively high specific energy, can provide a larger energy storage capacity, and lithium-ion batteries have no memory effect, so they do not need to be fully discharged before recharging. Therefore, secondary batteries have broad application prospects.

[0048] The separator is an important component of a secondary battery. It is a thin film with a microporous structure and plays two main roles: on the one hand, it separates the positive electrode plate and the negative electrode plate of the battery to prevent the positive electrode plate and the negative electrode plate from contacting and forming a short circuit; on the other hand, the micropores of the separator can allow active metal ions (such as lithium ions, sodium ions, etc.) to pass through, forming a charge and discharge circuit. However, existing separators are prone to transform from elastic deformation to plastic deformation under overvoltage conditions. The aperture and quantity of the pores on the separator decrease with the increase of pressure, clogging the pores, and preventing the passage of active metal ions, resulting in a reduction in the cycle performance and energy conversion efficiency of the battery containing it.

[0049] In this application, an elastic material with a high Young's modulus is added to the separator, which improves the ability of the separator to resist deformation. During the use of the battery, under different pressures and temperatures, the separator can exhibit elastic deformation and quickly return to its original state after the pressure is removed. This reduces the decrease in the aperture of the pores on the separator and the occurrence of closed pore phenomena, enabling the normal transmission of active metal ions and enhancing the cycle performance and energy conversion efficiency of the secondary battery containing it.

[0050] The separator disclosed in the embodiments of this application is applicable to secondary batteries, and the batteries disclosed in the embodiments of this application can be used in electrical equipment that uses the battery as a power source or various energy storage systems that use the battery as an energy storage element. The electrical equipment can include, but is not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, battery cars, electric vehicles, ships, spacecraft, etc. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spaceships, etc.

[0051] In a first aspect of this application, a separator is proposed. The separator includes an elastic material, and the Young's modulus of the elastic material is greater than or equal to 1 TPa.

[0052] This application has at least the following beneficial effects: Adding an elastic material with a Young's modulus greater than or equal to 1 TPa to the separator can significantly improve the ability of the separator to resist deformation. During the use of the battery, under different pressures and temperatures, the separator can exhibit elastic deformation and quickly return to its original state after the pressure is removed. This reduces the decrease in the aperture of the pores on the separator and the occurrence of closed pore phenomena, enabling active metal ions (such as lithium ions, sodium ions) to pass through the separator normally and enhancing the cycle performance and energy conversion efficiency of the secondary battery containing it.

[0053] It is understandable that an elastic material refers to a material that can return to its original state after the external force is removed, can undergo elastic deformation under the action of an external force, and return to its original state after the external force is withdrawn.

[0054] For example, in the embodiments of the present application, the elastic modulus of the elastic material can be 1 TPa - 15 TPa, 1.2 TPa - 5.3 TPa, 1.5 TPa - 5 TPa, 2 TPa - 4.5 TPa, 2.5 TPa - 4 TPa, 3 TPa - 3.5 TPa, etc. It is understandable that 1 TPa = 10 3 GPa = 10 6 MPa = 10 12 Pa. In some other embodiments of the present application, the Young's modulus of the elastic material is 1.8 - 5.5 TPa, for example 4.5 - 5.5 TPa.

[0055] It is understandable that the "Young's modulus of the elastic material" is a physical quantity that describes the ability of the elastic material to resist deformation. According to Hooke's law, within the elastic limit of an object, stress is proportional to strain, and the ratio is called the Young's modulus of the material. The magnitude of the Young's modulus marks the rigidity of the material. The larger the Young's modulus, the less likely it is to deform. The "Young's modulus of the elastic material" can be measured by instruments and methods well-known in the art. For example, in the compression modulus test of the in-situ expansion analysis system (Yuaneng Technology SWE2110):

[0056] ① Sample preparation steps:

[0057] Number of sample layers: > 20 layers;

[0058] Sample area: 50 * 60 mm 2 ;

[0059] Packaging requirements: Vacuum packaging with aluminum-plastic film, and the sample is airtight;

[0060] ② Test steps:

[0061] On the reference line, adjust the position of the limiter according to the thickness of the test sample;

[0062] Select the room temperature compression experiment in the experimental scheme column;

[0063] Test parameter settings: Test speed ≤ 5 mm / min, maximum test pressure ≤ 50000 N;

[0064] Place the sample in the test area, prepare to start the test, and export the test data.

[0065] In some embodiments of the present application, the tensile strength of the elastic material is 50 GPa - 200 GPa. For example, the tensile strength of the elastic material can be 50 GPa - 199 GPa, 60 GPa - 190 GPa, 70 GPa - 180 GPa, 80 GPa - 170 GPa, 90 GPa - 160 GPa, 100 GPa - 150 GPa, 110 GPa - 140 GPa, 120 GPa - 130 GPa, etc. Thus, controlling the tensile strength of the elastic material within the range of 50 GPa - 200 GPa can improve the strength and stability of the separator membrane, reduce the probability of short circuit between the positive electrode plate and the negative electrode plate in the secondary battery, improve the transport efficiency of active metal ions, and enhance the cycle performance and energy conversion efficiency of the secondary battery. In other embodiments of the present application, the tensile strength of the elastic material is 170 GPa - 200 GPa.

[0066] It can be understood that the "tensile strength of the elastic material" is a well-known definition in the art and can be measured by well-known instruments and methods in the art. For example, a CMT5305 series electronic universal testing machine can be used to test the tensile strength:

[0067] The test is carried out in accordance with the provisions of Standard GB / T1040.3—2006. A specimen with a width of 15 mm is used, the initial distance between the clamps is 50 mm, and the test speed is 2 mm / min. The force value is read, and the calculation formula is as follows:

[0068] σ = F / A

[0069] σ: Tensile strength, unit is megapascal (MPa) or (N / mm 2 );

[0070] F: The measured corresponding load, unit is Newton (N);

[0071] A: The original cross-sectional area of the specimen, unit is square millimeter (mm 2 )。

[0072] In some embodiments of the present application, based on the total mass of the separator membrane, the mass proportion of the elastic material is 0.1% - 1%. For example, based on the total mass of the separator membrane, the mass proportion of the elastic material can be 0.1% - 0.99%, 0.2% - 0.9%, 0.3% - 0.8%, 0.4% - 0.7%, 0.5% - 0.6%, etc. Specifically, controlling the mass proportion of the elastic material in the separator membrane within the above range is sufficient to improve the anti-deformation ability and strength of the separator membrane, and will not affect other aspects of the performance of the separator membrane, making the separator membrane have good electrical insulation, and can improve the cycle performance and energy conversion efficiency of the battery containing it. In some other embodiments of the present application, based on the total mass of the separator membrane, the mass proportion of the elastic material is 0.1% - 0.5%.

[0073] In some embodiments of the present application, the elastic material includes at least one of carbon nanotube springs or graphene sponges. Specifically, the above elastic material can significantly improve the ability of the separator membrane to resist deformation, so that during the use of the battery, under different pressures and temperatures, the separator membrane can exhibit elastic deformation, and after the pressure is removed, the separator membrane can quickly return to its original state, reducing the reduction of the pore diameter on the separator membrane and reducing the occurrence of closed pore phenomena, reducing the occurrence of closed pore phenomena on the separator membrane, enabling active metal ions to pass through the separator membrane for normal transmission, and improving the cycle performance and energy conversion efficiency of the secondary battery containing it.

[0074] It can be understood that the carbon nanotube spring is a spring made by processing carbon nanotubes (CNT). In the scanning electron microscope image, the morphology of the carbon nanotube spring is spring-shaped. In the carbon nanotube spring, the torsion and strong deformation of the carbon nanotube molecules significantly enhance the van der Waals force between the carbon nanotube molecules, making it have the characteristic of high Young's modulus. Since the helical part can be straightened and unfolded, the carbon nanotube spring can withstand a considerable strain before breaking and has the ability of reversible deformation, and can withstand a 6% reversible tensile strain. The component of the graphene sponge is carbon, also known as graphene aerogel. The graphene sponge is a three-dimensional porous network structure formed by the cross-linking of graphene sheets, can be arbitrarily adjusted in shape, has high elasticity, and can still return to its original state after being compressed by 80%.

[0075] In some embodiments of the present application, in some embodiments of the present application, the separator membrane includes a first membrane layer and a second membrane layer provided on at least one side of the first membrane layer, and the first membrane layer includes the elastic material. Thus, the elastic material of the embodiment of the present application is used in the first membrane layer, and the second membrane layer can use the materials commonly used for separator membranes in the art. Thus, by using the first membrane layer and the second membrane layer in combination, the influence of the addition of the elastic material on the insulation performance of the separator membrane can be reduced, and the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0076] It can be understood that the material of the second film layer is not limited in this application, as long as it is an insulating material, for example, it may include at least one of alumina ceramics, glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, polyimide, polytetrafluoroethylene, and aramid film.

[0077] In some embodiments of this application, second film layers are provided on both sides of the first film layer. In this way, the elastic material is clamped between at least two second film layers, which can reduce the influence of the elastic material on other properties of the separator membrane, reduce the influence of the elastic material in the first film layer on the ionic conductivity of the separator membrane, enable the separator membrane to have good ionic and electronic insulation, and can improve the cycle performance and energy conversion efficiency of the battery containing it.

[0078] In some embodiments of this application, the thickness ratio of the first film layer to the second film layer is (1.5 - 17.5):1. For example, the thickness ratio of the first film layer to the second film layer can be (1.5 - 17.4):1, (2 - 14):1, (3 - 13):1, (4 - 12):1, (5 - 11):1, (6 - 10):1, (7 - 9):1, etc. Thus, controlling the thickness ratio of the first film layer to the second film layer within the above range is sufficient to improve the anti-deformation ability and strength of the separator membrane, and will not affect other properties of the separator membrane, enabling the separator membrane to have good electronic insulation and can improve the cycle performance and energy conversion efficiency of the battery containing it. In some other embodiments of this application, the thickness ratio of the first film layer to the second film layer is (2.5 - 10):1.

[0079] In some embodiments of this application, the thickness of the first film layer is 15μm - 35μm. For example, the thickness of the first film layer can be 15μm - 34μm, 16μm - 33μm, 17μm - 32μm, 18μm - 31μm, 20μm - 30μm, 21μm - 29μm, 22μm - 28μm, 23μm - 27μm, 25μm - 26μm, etc. Controlling the thickness of the first film layer containing the elastic material within the range of 15μm - 35μm can improve the anti-deformation ability and strength of the separator membrane, and will not affect other properties of the separator membrane, enabling the separator membrane to have good electronic insulation and can improve the cycle performance and energy conversion efficiency of the battery containing it. In some other embodiments of this application, the thickness of the first film layer is 20μm - 30μm.

[0080] In some embodiments of the present application, the thickness of the second film layer is 2 μm - 10 μm. For example, the thickness of the second film layer can be 2 μm - 9.9 μm, 3 μm - 9 μm, 4 μm - 8 μm, 5 μm - 7 μm, 6 μm - 7 μm, etc. Thus, by controlling the thickness of the second film layer within the range of 2 μm - 10 μm, the anti-deformation ability and strength of the separator can be improved, and it will not affect other properties of the separator. The separator has good electrical insulation, which can improve the cycle performance and energy conversion efficiency of the battery containing it. In some other embodiments of the present application, the thickness of the second film layer is 3 μm - 8 μm.

[0081] In some embodiments of the present application, the porosity of the separator is 40% - 80%. For example, the porosity of the separator can be 40% - 79%, 45% - 75%, 50% - 70%, 55% - 65%, 60% - 65%, etc. Thus, by controlling the porosity of the separator within the above range and adding an elastic material to the separator, the ability of the separator to resist deformation can be significantly improved. During the use of the battery, under different pressures and temperatures, the separator can exhibit elastic deformation, and after the pressure is removed, the separator can quickly return to its original state, reducing the reduction of the pore diameter on the separator and reducing the occurrence of closed pores. The occurrence of closed pores in the separator is reduced, so that the porosity of the separator can be maintained at 40% - 80% for a long time, and active metal ions can pass through the separator for normal transmission, improving the cycle performance and energy conversion efficiency of the secondary battery containing it. In some other embodiments of the present application, the porosity of the separator is 60% - 80%.

[0082] It can be understood that the "porosity of the separator" is a well-known definition in the art and can be measured by well-known instruments and methods in the art. For example, it can be tested by the mercury intrusion method using a Micromeritics AutoPore V 9600 device, and the GB / T21650.2 - 2008 "Determination of pore size distribution and porosity of solid materials by mercury intrusion method and gas adsorption method - Part 2: Gas adsorption method for analysis of mesopores and macropores" standard is referred to during the test.

[0083] The second aspect of the present application provides a method for preparing a separator, including:

[0084] S10: Prepare a separator including an elastic material, and the Young's modulus of the elastic material is greater than or equal to 1 TPa.

[0085] Using the method of the present application, when preparing the separator, adding an elastic material reduces the reduction of the pore diameter on the separator and reduces the occurrence of closed pores, enabling the normal transmission of active metal ions and improving the cycle performance and energy conversion efficiency of the secondary battery containing it.

[0086] In some embodiments of the present application, the elastic material is prepared by the following method:

[0087] S200: Mix the elastic material precursor solution with a dispersant, centrifuge to discard the supernatant, and perform solvent heat treatment to remove the dispersant, obtaining an intermediate;

[0088] S201: Dry the intermediate and calcine it in an airtight manner to obtain the elastic material.

[0089] It can be understood that in step S200, particles with too small particle sizes in the precursor solution are removed by centrifugation, so that the elastic material precursor has a suitable particle size, which is convenient for subsequently bending it into a spring shape and improving the Young's modulus of the prepared elastic material; in the presence of a dispersant, the solvent heat treatment can bend the elastic material precursor in the precursor solution into a spring shape, and the calcination in step S201 can strengthen the spring-shaped elastic material; the elastic material prepared by the above method, when used in the separator membrane, can improve the cycle performance and energy conversion efficiency of the secondary battery.

[0090] In some embodiments of the present application, the volume ratio of the dispersant to the elastic material precursor solution with a concentration of 1.5 mg·mL -1 is (15 - 30):1. For example, the volume ratio of the dispersant to the elastic material precursor solution with a concentration of 1.5 mg·mL -1 can be (15 - 29):1, (16 - 28):1, (17 - 27):1, (18 - 26):1, (19 - 25):1, (20 - 24):1, (21 - 23):1, etc. Thus, by limiting the ratio of the dispersant to the elastic material precursor, an elastic material bent into a spring shape can be obtained, so that the Young's modulus of the elastic material is high. When the obtained elastic material is used in the separator membrane, the cycle performance and energy conversion efficiency of the secondary battery can be improved. In some other embodiments of the present application, the volume ratio of the dispersant to the elastic material precursor solution with a concentration of 1.5 mg·mL -1 is (20 - 30):1.

[0091] It can be understood that when the elastic material precursor solution is a suspension of carbon nanotubes, the obtained elastic material is a carbon nanotube spring; when the elastic material precursor liquid is a suspension solution of graphene, the obtained elastic material is a graphene sponge (graphene spring).

[0092] In some embodiments of the present application, the rotational speed of centrifugation is 8000 r / min - 15000 r / min. For example, the rotational speed of centrifugation can be 8000 r / min - 14000 r / min, 8500 r / min - 13500 r / min, 9000 r / min - 13000 r / min, 10000 r / min - 12000 r / min, 11000 r / min - 12000 r / min, etc. Within the above range of centrifugation rotational speeds, particles with too small particle sizes in the precursor solution can be removed, enabling the elastic material precursor to have a suitable particle size, facilitating its subsequent bending into a spring shape, enhancing the Young's modulus of the prepared elastic material, and improving the cycle performance and energy conversion efficiency of the secondary battery. In some other embodiments of the present application, the rotational speed of centrifugation is 10000 r / min - 15000 r / min.

[0093] In some embodiments of the present application, the temperature of the solvothermal treatment is 150°C - 250°C. For example, the temperature of the solvothermal treatment can be 150°C - 249°C, 160°C - 240°C, 170°C - 230°C, 180°C - 220°C, 190°C - 210°C, etc. Within the above range of solvothermal treatment temperatures, the elastic material precursor in the precursor solution can be bent into a spring shape, enhancing the Young's modulus of the prepared elastic material, and improving the cycle performance and energy conversion efficiency of the secondary battery. In some other embodiments of the present application, the temperature of the solvothermal treatment is 150°C - 200°C.

[0094] In some embodiments of the present application, the heating rate of the calcination is 1°C / min - 10°C / min. For example, the heating rate of the calcination can be 1°C / min - 9.9°C / min, 2°C / min - 9°C / min, 3°C / min - 8°C / min, 4°C / min - 7°C / min, 5°C / min - 6°C / min, etc. Thus, within the above range of heating rates, the spring-like structure of the elastic material can be strengthened, the Young's modulus of the obtained elastic material can be increased, and the cycle performance and energy conversion efficiency of the secondary battery can be improved. In some other embodiments of the present application, the heating rate of the calcination is 3°C / min - 8°C / min.

[0095] In some embodiments of the present application, the calcination temperature is 300°C - 500°C. For example, the calcination temperature can be 300°C - 490°C, 310°C - 480°C, 330°C - 470°C, 350°C - 450°C, 360°C - 440°C, 380°C - 420°C, 400°C - 410°C, etc. Thus, by controlling the calcination temperature within the above range, the spring-like structure of the elastic material can be strengthened, the Young's modulus of the obtained elastic material can be increased, and the cycle performance and energy conversion efficiency of the secondary battery can be improved. In some other embodiments of the present application, the calcination temperature is 350°C - 450°C.

[0096] In some embodiments of the present application, the calcination time is 0.5h - 3h. For example, the calcination time can be 0.5h - 2.9h, 0.7h - 2.8h, 0.9h - 2.6h, 1h - 2.5h, 1.3h - 2.3h, 1.5h - 2h, 1.7h - 1.9h, etc. Thus, by controlling the calcination time within the above range, the spring-like structure of the elastic material can be strengthened, the Young's modulus of the obtained elastic material can be increased, and the cycle performance and energy conversion efficiency of the secondary battery can be improved. In some other embodiments of the present application, the calcination time is 0.5h - 1.5h.

[0097] In some embodiments of the present application, the method includes:

[0098] S101: Prepare a first film layer, and the first film layer includes the elastic material;

[0099] S102: Prepare a second film layer on at least one side of the first film layer.

[0100] The elastic material of the embodiments of the present application is used in the first film layer, and the second film layer can use the materials of the commonly used separator films in the art. By using the first film layer and the second film layer in combination, the anti-deformation ability and strength of the separator film can be improved, and it will not affect other aspects of the performance of the separator film, so that the separator film has good electrical insulation, and the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0101] In some embodiments of the present application, in step S101, the first film layer is prepared by electrospinning. Thus, the stability of the pores of the separator film can be improved, and the cycle performance and energy conversion efficiency of the secondary battery can be improved.

[0102] It can be understood that during electrospinning, the elastic material of the embodiments of the present application can be mixed with a solvent and a polymer material, and then fibers are formed under the stretching action of electrostatic force. After the evaporation of the solvent or the cooling of the melt, it is solidified to form a fiber layer. This preparation method is efficient, low-cost, the formed separator has strong adaptability, good pore stability, and can improve the cycle performance and energy conversion efficiency of secondary batteries.

[0103] It can be understood that during electrospinning, at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, polyimide, polytetrafluoroethylene, and aramid film can be added to improve the comprehensive performance of the separator.

[0104] The third aspect of the present application provides a battery, which includes the separator of the first aspect of the present application or the separator prepared by the method of the second aspect. Thus, the battery has excellent cycle life and energy conversion efficiency.

[0105] A battery refers to a battery that can be activated by charging after discharging and can be used continuously.

[0106] It can be understood that the battery proposed in the present application can be a lithium-ion battery or a sodium-ion battery.

[0107] Generally, a battery includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. During the charge and discharge process of the battery, active metal ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The separator is arranged between the positive electrode plate and the negative electrode plate to play a role in isolation. The electrolyte plays a role in conducting active metal ions between the positive electrode plate and the negative electrode plate.

[0108] [Positive electrode plate]

[0109] The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

[0110] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0111] In some embodiments of the present application, the positive electrode tab includes a positive electrode current collector, and the positive electrode current collector can be a metal foil, a foam metal, or a composite current collector. For example, as the metal foil, aluminum or stainless steel with a silver surface treatment, stainless steel, copper, aluminum, carbon electrodes, carbon, nickel, or titanium, etc. can be used. The composite current collector can include a polymer material substrate layer and a metal layer. The foam metal can be foam nickel, foam copper, foam aluminum, foam alloy, etc. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0112] In some embodiments of the present application, the positive electrode tab may further include a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material. The specific type of the positive electrode active material is not limited, and active materials known in the art that can be used for the positive electrode of a battery can be used, and those skilled in the art can select according to actual needs.

[0113] When the battery is a lithium-ion battery, by way of example, the positive electrode active material may include, but is not limited to, at least one of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their modified compounds. These materials can all be obtained through commercial channels.

[0114] When the battery is a sodium-ion battery, by way of example, the positive electrode active material may include, but is not limited to, at least one of layered transition metal oxides, polyanion compounds, and Prussian blue analogs.

[0115] As an example of the above-mentioned layered transition metal oxides, for example, the following can be listed:

[0116] Na 1-x Cu h Fe k Mn l M 1 m O 2-y where M 1is at least one of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn, and Ba, 0 < x ≤ 0.33, 0 < h ≤ 0.24, 0 ≤ k ≤ 0.32, 0 < l ≤ 0.68, 0 ≤ m < 0.1, h + k + l + m = 1, 0 ≤ y < 0.2;

[0117] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 is at least one of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn, and Ba, 0 < z ≤ 0.1;

[0118] Na a Li b Ni c Mn d Fe e O2, where 0.67 < a ≤ 1, 0 < b < 0.2, 0 < c < 0.3, 0.67 < d + e < 0.8, b + c + d + e = 1.

[0119] As an example of the above polyanion compound, for example, the following can be listed:

[0120] A 1 f M 3 g (PO4) i O j X 1 3-j , where A 1 is at least one of H, Li, Na, K, and NH4, M 3 is at least one of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, and Zn, X 1 is at least one of F, Cl, and Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2;

[0121] Na n M 4 PO4X 2 , where M 4 is at least one of Mn, Fe, Co, Ni, Cu, and Zn, X 2 is at least one of F, Cl, and Br, 0 < n ≤ 2;

[0122] Na p M 5 q (SO4)3, where M 5is at least one of Mn, Fe, Co, Ni, Cu, and Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0123] Na s Mn t Fe 3-t (PO4)2(P2O7), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2, or 3.

[0124] As an example of the above-mentioned Prussian blue analogues, for example, the following can be listed:

[0125] A u M 6 v [M 7 (CN)6] w ·xH2O, where A is H + 、NH4 + 、at least one of alkali metal cations and alkaline earth metal cations, M 6 and M 7 are each independently at least one of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A is H + 、Li + 、Na + 、K + 、NH4 + 、Rb + 、Cs + 、Fr + 、Be 2+ 、Mg 2+ 、Ca 2+ 、Sr 2+ 、Ba 2+ and Ra 2+ at least one of, M 6 and M 7 are each independently cations of at least one transition metal element among Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, and W.

[0126] During the charge and discharge process of the battery, the deintercalation and consumption of Li or Na will occur, and the molar content of Li or Na is different when the battery is discharged to different states. In the examples of the positive electrode materials in this application, the molar content of Li or Na is the initial state of the material, that is, the state before feeding. When the positive electrode material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li or Na will change.

[0127] In the examples of the positive electrode materials in this application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will show fluctuations.

[0128] The modified compounds of the above materials can be doping modification and / or surface coating modification of the materials.

[0129] The positive electrode active material layer usually also optionally includes a binder, a conductive agent, and other optional additives.

[0130] As an example, the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, SuperP (SP), graphene, and carbon nanofibers.

[0131] As an example, the binder can include at least one of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0132] [Positive electrode plate]

[0133] In some embodiments of the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one side of the negative electrode current collector.

[0134] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0135] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0136] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery well-known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0137] In some embodiments, the negative electrode active material layer may also optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0138] In some embodiments, the negative electrode active material layer may also optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0139] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0140] In some embodiments, the negative electrode plate can be prepared by the following method: dispersing the components for preparing the negative electrode plate, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0141] [Electrolyte]

[0142] The electrolyte may include an electrolyte salt and a solvent.

[0143] As an example, when the battery is a lithium-ion battery, the electrolyte lithium salt may include at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate) borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluoro bis(oxalate) phosphate (LiDFOP), and lithium tetrafluoro bis(oxalate) phosphate (LiTFOP).

[0144] As an example, when the battery is a sodium-ion battery, the electrolyte sodium salt includes at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium bis(oxalate) borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate, and sodium bis(trifluoromethylsulfonyl)imide.

[0145] As an example, the solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0146] In some embodiments of the present application, the electrolyte solution further includes additives. For example, the additives may include negative electrode film-forming additives, or may include positive electrode film-forming additives, or may also include additives that can improve certain battery performance, such as additives for improving battery overcharge performance, additives for improving battery high-temperature performance, and additives for improving battery low-temperature performance.

[0147] The embodiments of the present application do not particularly limit the shape of the battery cell, which may be cylindrical, square, or any other arbitrary shape. As Figure 1 is a battery cell 5 with a square structure as an example.

[0148] In some embodiments, the battery cell may include an outer package. The outer package is used to encapsulate the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0149] In some embodiments, the outer package may include a housing and a cover plate. The housing may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing has an opening communicating with the receiving cavity, and the cover plate can be disposed on the opening to close the receiving cavity.

[0150] The positive electrode plate, the negative electrode plate and the separator can be formed into an electrode assembly by a winding process or a stacking process. The electrode assembly is encapsulated in the receiving cavity. The number of electrode assemblies included in the battery cell can be one or several, which can be adjusted according to requirements.

[0151] In some embodiments, the outer package of the battery cell may include a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0152] The outer package of the battery cell may also include a soft package, such as a pouch soft package. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0153] In some embodiments, the battery cells can be assembled into a battery module. The number of battery cells included in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0154] Figure 2 is the battery module 4 as an example. Refer to Figure 2 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0155] The battery module 4 may further include a housing having a receiving space, and a plurality of battery cells 5 are received in the receiving space. In some embodiments, the above battery module can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0156] Figure 3 and 4 is the battery pack 1 as an example. Refer to Figure 3 and 4 , in the battery pack 1, it may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be disposed on the lower box body 3 to form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any way.

[0157] The fourth aspect of the present application provides an electrical device, which includes the battery described in the third aspect. Specifically, the battery can serve as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (such as mobile phones, laptops), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships, satellites, and energy storage systems.

[0158] Figure 5 is an example of an electrical device. The electrical device includes a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0159] Another example of an electrical device may include a mobile phone, a tablet computer, a laptop. This type of electrical device usually requires a thin and light design and can use a battery as the power source.

[0160] In order to make the technical problems, technical solutions, and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail in combination with embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way constitutes a limitation to the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0161] Embodiment 1

[0162]

Preparation of Separator Membrane

[0163] (1) Preparation of Elastic Material

[0164] Add a certain amount of ethanol to an aqueous solution of carbon nanotubes (1.5 mg·mL -1 ), with V(ethanol):V(aqueous solution of carbon nanotubes) = 30:1, centrifuge at 12000 r / min for 10 times;

[0165] Perform solvothermal treatment in a Teflon-lined autoclave at a temperature of 180 °C for 12 h;

[0166] Immerse in acetone and ethanol (volume ratio 1:1), and then slowly add water to the system until the sponge solidifies;

[0167] Slowly remove about 1 / 3 of the solvent volume through an inverted bottle. Then, add water to cover the sponge again and repeat every 6 h for 15 - 20 times to remove the dispersants ethanol and acetone;

[0168] Perform low-temperature freeze-drying;

[0169] In an argon - protected atmosphere, it is heated to 400 °C at a rate of 5 °C / min and held for 1 h to prepare carbon nanotube springs.

[0170] (2) Preparation of the separator

[0171] Preparation of the first film layer:

[0172] Preparation of the polyimide solution:

[0173] ① Dissolve 4,4'-diaminodiphenylmethane (MDA) in the N - methylpyrrolidone (NMP) solvent;

[0174] ② Under the condition of controlling the temperature at 15 °C and magnetic stirring, add equimolar amounts of pyromellitic dianhydride (PMDA) in batches;

[0175] ③ Slowly and evenly add the carbon nanotube springs to the mixed solution in the previous step and ultrasonicate for 2 h;

[0176] ④ Add polyimide to the above - mentioned solution to prepare a polyimide solution, and prepare a separator by electrospinning;

[0177] Electrospinning preparation method:

[0178] Set the voltage at 20 KV, the rotation speed at 200 r / min, the feeding speed at 0.001 mm / s, the distance from the needle tip to the receiver at 20 cm, swing at the central position with an amplitude of 30 cm and a swing speed of 0.5 mm / s, the temperature at 30 °C, and the humidity at 65%. After electrospinning, dry it in an oven at 120 °C for 12 h, then place it in a muffle furnace, heat it in air to 350 °C at a rate of 3 °C / min, hold for 2 h, and cool to room temperature to obtain the first film layer.

[0179] Preparation of the second film layer:

[0180] Dissolve the LA132 binder (acrylonitrile - based copolymer) in deionized water with a mass ratio of 25:1, slowly add alumina powder while controlling the rotation speed at 3000 rpm, and the mass ratio of alumina powder to the LA132 binder is 100:13, then stir for 12 h to prepare a ceramic slurry;

[0181] Coat the above - mentioned ceramic slurry on both sides of the first film layer, dry it in an oven at 60 °C for 12 h to prepare a separator, and the thickness of the separator is 35 μm and the porosity is 70%. The specific implementation parameters are shown in Table 1.

[0182]

Preparation of the positive electrode plate

[0183] Polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive agent carbon black, and N-methylpyrrolidone (NMP) were mixed at a mass ratio of 1.2:58.38:0.42:40 and stirred thoroughly to prepare a positive electrode paste. The positive electrode paste was uniformly coated on the positive electrode current collector aluminum foil at a loading of 200 g / m 2 . After drying, cold pressing, and slitting, a positive electrode plate was obtained.

[0184]

Preparation of negative electrode plate

[0185] Artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were added to deionized water at a mass ratio of 96.2:1.0:1.6:1.2 and stirred thoroughly to prepare a negative electrode paste (solid content: 63%). The negative electrode paste was uniformly coated on the negative electrode current collector copper foil at a loading of 98 g / m 2 . After drying, cold pressing, and slitting, a negative electrode plate was obtained.

[0186]

Preparation of electrolyte

[0187] At 25 °C, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at a volume ratio of 1:1:1 to obtain a mixed solvent, and then LiPF6 was dissolved in the above mixed solvent to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.

[0188] The above positive electrode plate, separator, and negative electrode plate were stacked and wound in sequence and formed into an electric core; the electric core was placed in an outer package, and the prepared electrolyte was added. After processes such as encapsulation, standing, formation, and aging, a battery was obtained.

[0189] Examples 2-19 were the same as Example 1 except for the parameters (see Table 1).

[0190] Example 20

[0191]

Preparation of separator

[0192] (1) Preparation of elastic material

[0193] A certain amount of ethanol was added to an aqueous solution of carbon nanotubes (1.5 mg·mL -1 ), with V(ethanol):V(aqueous solution of carbon nanotubes) = 30:1, and centrifuged at 12000 r / min for 10 times;

[0194] Solvothermal treatment was carried out in a Teflon-lined autoclave at a temperature of 180 °C for 12 h;

[0195] Immerse it in acetone and ethanol (volume ratio 1:1), and then slowly add water to the system until the sponge solidifies;

[0196] Slowly remove about 1 / 3 of the solvent volume through an inverted bottle. Then, add water to cover the sponge again and repeat every 6 h for 15 - 20 times to remove the dispersants ethanol and acetone;

[0197] Perform low-temperature freeze-drying;

[0198] In an argon-protected atmosphere, heat it to 400 °C at a rate of 5 °C / min and hold for 1 h to prepare carbon nanotube springs.

[0199] (2) Preparation of the separator

[0200] Preparation of the first film layer:

[0201] Preparation of the polyimide solution:

[0202] ① Dissolve 4,4'-diaminodiphenylmethane (MDA) in the N-methylpyrrolidone (NMP) solvent;

[0203] ② Under the conditions of controlling the temperature at 15 °C and magnetic stirring, add an equimolar amount of pyromellitic dianhydride (PMDA) in batches;

[0204] ③ Slowly and uniformly add the carbon nanotube springs to the mixed solution in the previous step and sonicate for 2 h;

[0205] ④ Add polyimide to the above solution to prepare a polyimide solution, and prepare a separator by electrospinning;

[0206] Electrospinning preparation method:

[0207] Set the voltage at 20 KV, the rotation speed at 200 r / min, the feeding speed at 0.001 mm / s, the distance from the needle tip to the receiver at 20 cm, swing at the central position with a swing amplitude of 30 cm and a swing speed of 0.5 mm / s, the temperature at 30 °C, and the humidity at 65%. After electrospinning, dry it in an oven at 120 °C for 12 h, then place it in a muffle furnace, heat it to 350 °C at a rate of 3 °C / min in air, hold for 2 h, and cool to room temperature to obtain the first film layer, i.e., the separator, with a thickness of 35 μm and a porosity of 70%.

[0208] The remaining preparation methods are the same as those in Example 1.

[0209] Examples 21 - 23 are the same as Example 20 except for the parameters (see Table 1).

[0210] Comparative Example 1

[0211]

Preparation of the separator

[0212] Preparation of the first film layer:

[0213] Preparation of polyimide solution:

[0214] ① Dissolve 4,4'-diaminodiphenylmethane (MDA) in N-methylpyrrolidone (NMP) solvent;

[0215] ② Under the condition of controlling the temperature at 15°C and magnetic stirring, add isophthalic tetracarboxylic dianhydride (PMDA) in batches with an equal amount of substance;

[0216] ③ Add polyimide to the above solution to prepare a polyimide solution, and prepare a separator by electrospinning;

[0217] Preparation method by electrospinning:

[0218] Set the voltage at 20 KV, the rotation speed at 200 r / min, the feeding speed at 0.001 mm / s, the distance from the needle tip to the receiver at 20 cm, swing at the central position with a swing amplitude of 30 cm and a swing speed of 0.5 mm / s, the temperature at 30°C, and the humidity at 65%. After electrospinning, dry it in an oven at 120°C for 12 h, then place it in a muffle furnace, heat it up to 350°C at a rate of 3°C / min in air, keep it warm for 2 h, and cool it to room temperature to obtain the first film layer.

[0219] Preparation of the second film layer:

[0220] Dissolve LA132 binder (acrylonitrile copolymer) in deionized water with a mass ratio of 25:1, slowly add alumina powder while controlling the rotation speed at 3000 rpm, and the mass ratio of alumina powder to LA132 binder is 100:13, then stir for 12 h to prepare a ceramic slurry;

[0221] Coat the two sides of the first film layer with the above ceramic slurry, dry it in an oven at 60°C for 12 h to prepare a separator, and the thickness of the separator is 35 μm and the porosity is 70%.

[0222] The remaining preparation methods are the same as those in Example 1.

[0223] Comparative Example 2

[0224] Preparation of the first film layer:

[0225] Preparation of polyimide solution:

[0226] ① Dissolve 4,4'-diaminodiphenylmethane (MDA) in N-methylpyrrolidone (NMP) solvent;

[0227] ② Under the condition of controlling the temperature at 15°C and magnetic stirring, add isophthalic tetracarboxylic dianhydride (PMDA) in batches with an equal amount of substance;

[0228] ③ Slowly and evenly add commercially available carbon nanotubes to the mixed solution from the previous step, and ultrasonicate for 2 h;

[0229] ④ Add polyimide to the above solution to prepare a polyimide solution, and prepare a separator by electrospinning;

[0230] Electrospinning preparation method:

[0231] Set the voltage to 20 KV, the rotation speed to 200 r / min, the feeding speed to 0.001 mm / s, the distance from the needle tip to the receiver to 20 cm, swing at the central position, the swing amplitude to 30 cm, the swing speed to 0.5 mm / s, the temperature to 30 °C, and the humidity to 65%. After electrospinning is completed, dry in an oven at 120 °C for 12 h, then place it in a muffle furnace, heat it to 350 °C at a rate of 3 °C / min in air, hold for 2 h, and cool to room temperature to obtain the first film layer.

[0232] Preparation of the second film layer:

[0233] Dissolve the LA132 binder (acrylonitrile copolymer) in deionized water with a mass ratio of 25:1, slowly add alumina powder while controlling the rotation speed at 3000 rpm, and the mass ratio of alumina powder to the LA132 binder is 100:13. Then stir for 12 h to prepare a ceramic slurry;

[0234] Coat the above ceramic slurry on both sides of the first film layer, and dry in an oven at 60 °C for 12 h to prepare a separator. The thickness of the separator is 35 μm and the porosity is 70%.

[0235] The remaining preparation methods are the same as those in Example 1.

[0236] The parameters of the separators in Examples 1-23 and Comparative Examples 1-2 of this application are shown in Table 1.

[0237] Table 1

[0238]

[0239]

[0240] In Table 1, " / " means not added.

[0241] Performance test:

[0242] 1. Young's modulus test of elastic materials

[0243] Measure using an in-situ swelling analysis system (Yueneng Technology SWE2110)

[0244] ① Specimen preparation steps:

[0245] Number of specimen layers: > 20 layers;

[0246] Specimen area: 50 * 60 mm 2 ;

[0247] Packaging requirements: Vacuum packaging with aluminum-plastic film, and the sample should be airtight;

[0248] ② Test steps:

[0249] On the reference line, adjust the position of the limiter according to the thickness of the test sample;

[0250] Select the room temperature compression test in the experimental plan column;

[0251] Test parameter settings: Test speed ≤ 5 mm / min, maximum test pressure ≤ 50000 N;

[0252] Place the sample in the test area, prepare to start the test, and export the test data.

[0253] 2. Test steps for the tensile strength determination of elastic materials: Place the sample in a CMT5305 series electronic universal testing machine and conduct the test according to the provisions of GB / T 1040.3—2006. Use a specimen with a width of 15 mm, an initial distance between the clamps of 50 mm, and a test speed of 2 mm / min. Read the force value, and the calculation formula is as follows. σ = F / A

[0254] σ: Tensile strength, unit is megapascal (MPa) or (N / mm 2 );

[0255] F: Measured corresponding load, unit is newton (N);

[0256] A: Original cross-sectional area of the specimen, unit is square millimeter (mm 2 ).

[0257] 3. Test for the capacity retention rate of secondary batteries (cycling performance)

[0258] At 25 °C, charge at a constant current of 1 / 3C to 3.6V, then charge at a constant voltage of 3.6V until the current is 0.05C, let it stand for 5 min, and then discharge at 1 / 3C to 2.5V. The obtained capacity is recorded as the initial capacity C0. Repeat the above steps and record the discharge capacity C1000 of the secondary battery after the 1000th cycle at the same time. Then the capacity retention rate P1000 of the secondary battery after 1000 cycles = C1000 / C0 × 100%, and the results are shown in Table 2.

[0259] 4. Test for the energy conversion efficiency of secondary batteries

[0260] At 25 °C, the test steps for the energy conversion efficiency are shown in Table 2: Among them, Rest represents the static treatment, DP represents the constant power discharge, and CP represents the constant power charge. The results are shown in Table 3.

[0261] Table 2

[0262]

[0263]

[0264] Energy conversion efficiency = Energy of discharge in item 12) / Energy of charge in item 8) × 100%.

[0265] Table 3

[0266] Retention rate of cycle capacity at 25°C Energy conversion efficiency at 25°C Example 1 92.1％ 96.2％ Example 2 91.3％ 95.7％ Example 3 91.6％ 95.9％ Example 4 68.2％ 81.2％ Example 5 92.0％ 96.1％ Example 6 91.8％ 95.9％ Example 7 91.4％ 95.5％ Example 8 91.1％ 95.4％ Example 9 92.0％ 95.9％ Example 10 90.9％ 94.8％ Example 11 90.5％ 94.6％ Example 12 91.8％ 95.9％ Example 13 91.3％ 95.3％ Example 14 89.5％ 91.8％ Example 15 88.3％ 90.7％ Example 16 91.8％ 95.7％ Example 17 91.1％ 95.3％ Example 18 85.1％ 90.4％ Example 19 85％ 89.7％ Example 20 87.5％ 92.2％ Example 21 89.1％ 92.3％ Example 22 87.3％ 92.1％ Example 23 89.0％ 93.9％ Comparative Example 1 61.5％ 63.4％ Comparative Example 2 64.6％ 65.3％

[0267] As can be seen from Table 3, in Examples 1 - 23 of the present application, by controlling the Young's modulus of the elastic material in the separator, the ability of the separator to resist deformation is improved, such that during the use of the battery, under different pressures, the separator can exhibit elastic deformation, and after the pressure is removed, it quickly returns to its original state, reducing the reduction of the pore diameter on the separator and the occurrence of closed - pore phenomena, enabling the normal transmission of active metal ions, and enhancing the cycle performance and energy conversion efficiency of the secondary battery containing it. In Comparative Example 1, no elastic material is added, and in Comparative Example 2, the Young's modulus of the elastic material is not within the scope of the present application. The cycle performance and energy conversion efficiency of the battery are significantly lower than those of Examples 1 - 23. It can be seen that the separator provided by the present application can improve the closed - pore phenomenon and enhance the cycle performance and energy conversion efficiency of the secondary battery containing it.

[0268] Finally, it should be noted that: the above - mentioned embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent substitution on some or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be covered within the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. An isolation film, characterized in that, The separator membrane includes an elastic material, and the Young's modulus of the elastic material is greater than or equal to 1 TPa.

2. The isolation film according to claim 1, characterized in that, The Young's modulus of the elastic material is 1 TPa - 5.5 TPa, optionally 1.8 - 5.5 TPa, and further optionally 4.5 - 5.5 TPa.

3. The isolation film according to claim 1 or 2, characterized in that, The tensile strength of the elastic material is 50 GPa - 200 GPa, optionally 170 GPa - 200 GPa.

4. The isolation film according to any one of claims 1-3, characterized in that, Based on the total mass of the separator membrane, the mass percentage of the elastic material is 0.1% - 1%, optionally 0.1% - 0.5%.

5. The isolation film according to any one of claims 1-4, characterized in that, The elastic material includes at least one of carbon nanotube springs or graphene sponges.

6. The isolation film according to any one of claims 1-5, characterized in that, The separator membrane includes a first membrane layer and a second membrane layer provided on at least one side of the first membrane layer, and the first membrane layer includes the elastic material.

7. The isolation film according to claim 6, characterized in that, The second membrane layer is provided on both sides of the first membrane layer.

8. The isolation film according to claim 6 or 7, characterized in that, The thickness ratio of the first membrane layer to the second membrane layer is (1.5 - 17.5):1, optionally (2.5 - 10):

1.

9. The isolation film according to claims 6-8, characterized in that, The thickness of the first membrane layer is 15 μm - 35 μm, optionally 20 μm - 30 μm.

10. The isolation film according to any one of claims 6-9, characterized in that, The thickness of the second membrane layer is 2 μm - 10 μm, optionally 3 μm - 8 μm.

11. The isolation film according to any one of claims 1-10, characterized in that, The porosity of the separator membrane is 40% - 80%, optionally 60% - 80%.

12. A method for preparing an isolation film, characterized in that, Comprising: Preparing a separator membrane including an elastic material, and the Young's modulus of the elastic material is greater than or equal to 1 TPa.

13. The method according to claim 12, characterized in that, The elastic material is prepared by the following method: Mixing an elastic material precursor solution with a dispersant, centrifuging to discard the supernatant, and performing solvothermal treatment to remove the dispersant to obtain an intermediate; Drying the intermediate and calcining it under air isolation to obtain the elastic material.

14. The method according to claim 13, characterized in that, The volume ratio of the dispersant to the elastic material precursor solution with a concentration of 1.5 mg·mL -1 is (15 - 30):1, and may be optionally (20 - 30):

1.

15. The method according to claim 13 or 14, characterized in that, The rotation speed of the centrifugation is 8000 r / min - 15000 r / min, optionally 10000 r / min - 15000 r / min.

16. The method according to any one of claims 13-15, characterized in that, The temperature of the solvothermal treatment is 150°C - 250°C, optionally 150°C - 200°C.

17. The method according to any one of claims 13-16, characterized in that, Satisfying at least one of the following conditions: The heating rate of the calcination is 1°C / min - 10°C / min, optionally 3°C / min - 8°C / min; The temperature of the calcination is 300°C - 500°C, optionally 350°C - 450°C; The time of the calcination is 0.5 h - 3 h, optionally 0.5 h - 1.5 h.

18. The method according to any one of claims 12 - 17, wherein, Comprising: Preparing a first membrane layer, and the first membrane layer includes the elastic material; Preparing a second membrane layer on at least one side of the first membrane layer.

19. The method according to claim 18, wherein, The first membrane layer is prepared by electrospinning.

20. A battery, wherein, Comprising the separator membrane according to any one of claims 1 - 11, or the separator membrane prepared by the method according to any one of claims 12 - 19.

21. An electrical device, wherein, Comprising the battery according to claim 20.

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