Separator and preparation method therefor, battery, and electric device

Abstract

A separator and a preparation method therefor, a battery, and an electric device. The separator comprises polysilsesquioxane, the polysilsesquioxane having a Dv90 particle size of aμm, a Dv10 particle size of bμm, and a Dv50 particle size of cμm, where (a-b) / c≤3. A secondary battery containing the separator has good cycling performance.

Description

Isolation film and preparation method thereof, battery and electrical equipment

[0001] Priority information

[0002] This application claims priority and benefits of patent application 202311594479.1 filed with the State Intellectual Property Office of China on November 24, 2023, and the entire text of which is incorporated herein by reference. Technical Field

[0003] The present application belongs to the technical field of secondary batteries, and specifically relates to an isolation membrane and a preparation method thereof, a battery, and an electrical device. Background Art

[0004] Secondary batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as in military equipment, aerospace and other fields.

[0005] The separator is an important component of the secondary battery. However, the existing separators have poor heat resistance and stability, and low transmission efficiency of active metal ions, resulting in poor cycle performance of the secondary battery containing the separator.

[0006] Summary of the Invention

[0007] In view of the technical problems existing in the background technology, the present application provides an isolation membrane, aiming to solve the problem of poor cycle performance of batteries containing the isolation membrane.

[0008] In order to achieve the above-mentioned object, the first aspect of the present application provides an isolation film, wherein the isolation film comprises polysilsesquioxane, wherein the D v 90particle size is aμm, D v 10 Particle size is b μm, D v 50Particle size is cμm, (ab) / c≤3.

[0009] The present application includes at least the following beneficial effects: In the present application, polysilsesquioxane is added to the isolation membrane and the particle size distribution of the polysilsesquioxane is controlled, so that the channels and distances for the transmission of active metal ions on the isolation membrane are similar, thereby improving the transmission efficiency of the active metal ions and enhancing the cycle performance of the secondary battery.

[0010] In some embodiments of the present application, 0.4≤(ab) / c≤1.5, thereby improving the cycle performance of the secondary battery.

[0011] In some embodiments of the present application, a=0.5-5, optionally, a=0.6-2.5, thereby improving the cycle performance of the secondary battery.

[0012] In some embodiments of the present application, b = 0.05-1.5, optionally, b = 0.1-1.3, thereby improving the cycle performance of the secondary battery.

[0013] In some embodiments of the present application, c=0.1-3, optionally, c=0.4-1.7, thereby improving the cycle performance of the secondary battery.

[0014] In some embodiments of the present application, the weight average molecular weight of the polysilsesquioxane is 10,000-100,000, and can be 30,000-80,000, thereby improving the cycle performance of the secondary battery.

[0015] In some embodiments of the present application, the density of the polysilsesquioxane is 1 g / cm 3 -1.3g / cm 3 , optional 1g / cm 3 -1.2g / cm 3 Thus, the cycle performance of the secondary battery can be improved.

[0016] In some embodiments of the present application, the structural formula of the polysilsesquioxane includes:

[0017] Wherein, R1 and R2 each independently include an alkyl group of 1-12 carbon atoms, an unsaturated hydrocarbon group of 1-12 carbon atoms or a phenyl group, and n=50-1000.

[0018] This can improve the cycle performance of the secondary battery.

[0019] In some embodiments of the present application, the polysilsesquioxane comprises at least one of the following structural formulas:

[0020] Wherein, Ph represents phenyl, and n=50-1000.

[0021] This can improve the cycle performance of the secondary battery.

[0022] In some embodiments of the present application, the separator includes a base film and a coating located on at least one side of the base film, wherein the coating includes the polysilsesquioxane, thereby improving the cycle performance of the secondary battery.

[0023] In some embodiments of the present application, the thickness of the coating is 0.3 μm-3 μm, and optionally 0.5 μm-2 μm, thereby improving the cycle performance of the secondary battery.

[0024] In some embodiments of the present application, the coating further comprises a binder, wherein the binder comprises at least one of polyacrylic acid, polyacrylate, polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorine-containing acrylate resin. Thus, the cycle performance of the secondary battery can be improved.

[0025] In some embodiments of the present application, the mass ratio of the polysilsesquioxane to the binder is (5-25): 1, and can be optionally (8-20): 1. This can improve the cycle performance of the secondary battery.

[0026] In some embodiments of the present application, the thickness of the base film is 4 μm-20 μm, and optionally 5 μm-18 μm, thereby improving the cycle performance of the secondary battery.

[0027] In some embodiments of the present application, the pore size of the base film is 0.02 μm-0.08 μm, and optionally 0.03 μm-0.06 μm, thereby improving the cycle performance of the secondary battery.

[0028] In some embodiments of the present application, the porosity of the base film is 30%-70%, and optionally 35%-65%, thereby improving the cycle performance of the secondary battery.

[0029] A second aspect of the present application provides a method for preparing an isolation membrane, comprising:

[0030] Preparation of a release film containing polysilsesquioxane, wherein the polysilsesquioxane has a D v 90particle size is aμm, D v 10 Particle size is b μm, D v 50Particle size is cμm, (ab) / c≤3.

[0031] Therefore, by adopting the method of the present application, polysilsesquioxane is added during the preparation of the separator, and the particle size distribution of the polysilsesquioxane is controlled, thereby improving the transmission efficiency of active metal ions and enhancing the cycle performance of the secondary battery.

[0032] In some embodiments of the present application, a coating is prepared on at least one side of a base film to obtain a separator, wherein the coating includes the polysilsesquioxane. Thus, by disposing the polysilsesquioxane in the coating, the cycle performance of the secondary battery can be improved.

[0033] In some embodiments of the present application, the polysilsesquioxane is prepared by hydrolyzing an organosiloxane monomer, adding a catalyst, and polycondensing under heating conditions to obtain the polysilsesquioxane. The polysilsesquioxane obtained through the hydrolysis and polycondensation reactions is used in a separator to improve the cycling performance of a secondary battery.

[0034] In some embodiments of the present application, the hydrolysis temperature of the organosiloxane monomer is 20° C.-30° C. Therefore, within the above hydrolysis temperature range, the organosiloxane monomer is fully hydrolyzed, and the obtained polysilsesquioxane is used in the separator to improve the cycle performance of the secondary battery.

[0035] In some embodiments of the present application, the heating temperature is 30° C.-100° C., optionally 40° C.-80° C. Within the above heating temperature range, polysilsesquioxane with uniform particle size distribution can be obtained, which can improve the cycle performance of the secondary battery.

[0036] In some embodiments of the present application, the catalyst includes at least one of ammonia water, triethylamine, sodium hydroxide, magnesium hydroxide, or ammonium hydroxide. Thus, a polysilsesquioxane with uniform particle size distribution can be obtained, which can improve the cycle performance of the secondary battery.

[0037] In some embodiments of the present application, the organosiloxane monomer includes:

[0038] Wherein, R3 includes any one of methyl and ethyl, and R4 includes any one of methyl, ethyl, phenyl, vinyl, allyl, and dodecyl. Thus, a polysilsesquioxane with uniform particle size distribution can be obtained, which can improve the cycle performance of the secondary battery.

[0039] In some embodiments of the present application, the organosiloxane monomer includes at least one of methyltrimethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, dodecyltrimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, phenyltriethoxysilane, dodecyltriethoxysilane, vinyltriethoxysilane, or allyltriethoxysilane. This can produce a polysilsesquioxane with a uniform particle size distribution, which can improve the cycling performance of a secondary battery.

[0040] The third aspect of the present application provides a battery comprising the separator described in the first aspect of the present application or the separator prepared by the method described in the second aspect of the present application, thereby having excellent cycle performance.

[0041] A fourth aspect of the present application provides an electrical device comprising the battery described in the third aspect.

[0042] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0044] FIG1 is a schematic structural diagram of a battery according to an embodiment of the present application;

[0045] FIG2 is a schematic structural diagram of a battery module according to an embodiment of the present application;

[0046] FIG3 is a schematic structural diagram of a battery pack according to an embodiment of the present application;

[0047] FIG4 is an exploded view of FIG3 ;

[0048] FIG5 is a schematic diagram of an embodiment of an electric device using a battery as a power source;

[0049] FIG6 is a particle size distribution diagram of polysilsesquioxane of Example 1 of the present application;

[0050] FIG7 is a scanning electron microscope image of the polysilsesquioxane of Example 1 of the present application.

[0051] Explanation of reference numerals: 1: battery pack; 2: upper case; 3: lower case; 4: battery module; 5: battery cell. DETAILED DESCRIPTION

[0052] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0053] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0054] For the sake of clarity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art 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-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0056] With the technological advancements and increasing demand for electric vehicles and rechargeable mobile devices, secondary batteries, as a representative of the new energy sector, have seen rapid growth in research. Secondary batteries offer a wide range of applications due to their compact size and weight, making them easy to carry and use. Their high specific energy content allows for greater energy storage capacity, and lithium-ion batteries exhibit no memory effect, requiring no full discharge and recharge.

[0057] The separator is a crucial component of a secondary battery. It is a thin film with a microporous structure that serves two primary functions: first, it separates the positive and negative electrodes of the battery, preventing contact and short circuits. Second, the separator's micropores allow active metal ions (such as lithium and sodium ions) to pass through, forming a charge-discharge circuit. However, existing separators suffer from poor heat resistance and stability. At temperatures between 130°C and 150°C, separators shrink significantly, resulting in low transport efficiency for active metal ions and poor cycling performance for secondary batteries containing them.

[0058] In the present application, polysilsesquioxane is added to the isolation membrane, and the particle size distribution of the polysilsesquioxane ((ab) / c) is controlled. On the one hand, polysilsesquioxane has excellent heat resistance, high mechanical strength and hardness, good chemical stability, and is insoluble in organic solvents, which improves the heat resistance and stability of the isolation membrane. When the isolation membrane shrinks due to heat, the uniform polysilsesquioxane particles quickly contact and squeeze each other, which can provide a force opposite to the shrinkage direction of the isolation membrane, thereby reducing the degree of shrinkage of the isolation membrane, thereby enhancing the deformation resistance of the isolation membrane and reducing the probability of short circuit between the positive and negative electrodes in the secondary battery; on the other hand, the polysilsesquioxane (ab) / c of ​​the present application is within the above range, the particle size is uniform, and the spacing between the polysilsesquioxane particles is uniform, making the isolation membrane relatively flat, and the channels and distances for the transmission of active metal ions on the isolation membrane are similar, thereby improving the transmission efficiency of active metal ions and improving the cycle performance of the secondary battery.

[0059] The isolation membrane disclosed in the embodiments of the present application is suitable for secondary batteries, and the batteries disclosed in the embodiments of the present application can be used in electrical devices that use batteries as power sources or various energy storage systems that use batteries as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0060] In a first aspect, the present application provides an isolation film, wherein the isolation film comprises polysilsesquioxane, wherein the D v 90particle size is aμm, D v 10 Particle size is b μm, D v 50Particle size is cμm, (ab) / c≤3.

[0061] The present application includes at least the following beneficial effects: adding polysilsesquioxane to the isolation membrane and controlling the particle size distribution of the polysilsesquioxane. On the one hand, polysilsesquioxane has excellent heat resistance, high mechanical strength and hardness, good chemical stability, and is insoluble in organic solvents, which improves the heat resistance and stability of the isolation membrane. When the isolation membrane shrinks due to heat, the uniform polysilsesquioxane particles quickly contact and squeeze each other, which can provide a force opposite to the shrinkage direction of the isolation membrane, thereby reducing the degree of shrinkage of the isolation membrane, thereby enhancing the deformation resistance of the isolation membrane and reducing the probability of short circuit between the positive and negative electrodes in the secondary battery; on the other hand, the polysilsesquioxane particles of the present application are uniform in size and uniformly spaced, making the isolation membrane relatively flat, enhancing the air permeability of the isolation membrane, and the channels and distances for the transmission of active metal ions on the isolation membrane are similar, thereby improving the transmission efficiency of active metal ions and improving the cycle performance of the secondary battery.

[0062] It can be understood that the polysilsesquioxane of the embodiment of the present application has dual organic and inorganic properties, and has properties such as high wear resistance, high hardness, and high melting point. Compared with general organosilicon polysiloxanes, it has higher heat resistance and lower surface energy. The silicon-carbon material that can resist oxygen degradation is deposited on the surface of the isolation membrane, reducing oxygen contact and slowing down heat transfer, thereby achieving a flame retardant effect, thereby further improving the heat resistance of the battery.

[0063] It is understandable that, in the embodiment of the present application, D v The 90 particle size refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 90%, that is, the volume content of particles smaller than this particle size accounts for 90% of all particles; D v The 50 particle size refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50%, that is, the volume content of particles larger than this particle size accounts for 50% of all particles, and the volume content of particles smaller than this particle size also accounts for 50% of all particles. v The particle size 10 refers to the particle size corresponding to the cumulative volume distribution percentage reaching 10%, that is, the volume content of particles smaller than this particle size accounts for 10% of all particles; the above three particle size values ​​can be measured using instruments and methods known in the art, for example, with reference to the standard GB / T 19077-2016, using a laser particle size analyzer (e.g., Malvern Master Size 3000) for measurement.

[0064] It can be understood that (ab) / c can be interpreted as the particle size distribution span of polysilsesquioxane, which is a measure of the particle size distribution width of polysilsesquioxane. The closer the span is to 0, the more uniform the particle size and the higher the size consistency. In the embodiment of the present application, for example, the value of (ab) / c can be 0.01-3, 0.1-2.9, 0.2-2.8, 0.4-2.5, 0.7-2.3, 1-2, 1.3-1.8, 1.5-1.5, etc. When (ab) / c is within the above range, the polysilsesquioxane particles are evenly spaced, making the isolation membrane relatively flat, enhancing the permeability of the isolation membrane, and the channels and distances for the transmission of active metal ions on the isolation membrane are similar, thereby improving the transmission efficiency of active metal ions and improving the cycle performance of the secondary battery. In other embodiments of the present application, 0.4≤(ab) / c≤1.5.

[0065] In some embodiments of the present application, a=0.5-5. For example, a can be 0.5-4.9, 0.7-4.5, 1-4, 1.3-3.8, 1.5-3.5, 1.8-3.3, 2-3, 2.5-2.8, etc. Thus, the D of the polysilsesquioxane is v A particle size of 90 in the range of 0.5 μm to 5 μm can improve the heat resistance and stability of the separator, reduce the probability of short circuits between the positive and negative electrodes in the secondary battery, and improve the transmission efficiency of active metal ions. Furthermore, it can reduce the probability of polysilsesquioxane clogging the micropores in the separator, thereby improving the cycle performance of the secondary battery. In other embodiments of the present application, a = 0.6-2.5.

[0066] In some embodiments of the present application, b=0.05-1.5, for example, b can be 0.05-1.49, 0.1-1.45, 0.2-1.4, 0.3-1.3, 0.4-1.2, 0.5-1.1, 0.6-1, 0.7-0.9, 0.8-0.9, etc. Specifically, the D of the polysilsesquioxane v A particle size in the range of 0.05 μm to 1.5 μm can improve the heat resistance and stability of the separator, reduce the probability of short circuits between the positive and negative electrodes in the secondary battery, and improve the transmission efficiency of active metal ions. Furthermore, it can reduce the probability of polysilsesquioxane clogging the micropores in the separator, thereby improving the cycle performance of the secondary battery. In other embodiments of the present application, b = 0.1-1.3.

[0067] In some embodiments of the present application, c=0.1-3. For example, c can be 0.1-2.9, 0.3-2.7, 0.5-2.5, 0.7-2.3, 1-2, 1.2-1.8, 1.5-1.7, etc. Specifically, the D of the polysilsesquioxane vA particle size of 50 in the range of 0.1 μm to 3 μm can improve the heat resistance and stability of the separator, reduce the probability of short circuits between the positive and negative electrodes in the secondary battery, and improve the transmission efficiency of active metal ions. In addition, it can reduce the probability of polysilsesquioxane clogging the micropores in the separator, thereby improving the cycle performance of the secondary battery. In other embodiments of the present application, c = 0.4-1.7.

[0068] In some embodiments of the present application, the weight average molecular weight of the polysilsesquioxane is 10,000-100,000. For example, the weight average molecular weight of the polysilsesquioxane can be 10,000-99,000, 15,000-95,000, 20,000-90,000, 30,000-80,000, 40,000-70,000, 50,000-60,000, etc. Thus, when the weight average molecular weight of the polysilsesquioxane is within the above range, a polysilsesquioxane with a uniform particle size distribution can be obtained, thereby improving the heat resistance and stability of the separator, reducing the probability of short circuit between the positive and negative electrodes in the secondary battery, and improving the transmission efficiency of active metal ions. In addition, the probability of polysilsesquioxane clogging the micropores on the separator can be reduced, thereby improving the cycle performance of the secondary battery. In other embodiments of the present application, the weight average molecular weight of the polysilsesquioxane is 30,000-80,000.

[0069] It is understood that the "weight average molecular weight of polysilsesquioxane" is a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be obtained by the following method:

[0070] The determination was made by referring to the standard GB / T 21863-2008 gel permeation chromatography. Specifically, in the embodiments of the present application, the determination was made in the following manner: using an ultra-high performance polymer chromatograph: ACQUITY APC; and using an ACQUITY differential refractive index detector.

[0071] Parameter settings: injection volume: 0 μL to 50 μL (depending on sample concentration); pump flow rate: 0.2 mL / min; mobile phase: 30 mol / L LiBr in NMP (N-methylpyrrolidone) solution; sealing cleaning liquid: isopropanol; pre-column: PLgel10umMiniMIX-BGuard (size: 50 mm × 4.6 mm × 2); analytical phase: PLgel10umMiniMIX-B (size: 250 mm × 4.6 mm); standard: polystyrene sleeve; running time: 30 min; detector: ACQUITY differential refractive index (RI) detector; column oven temperature: 90°C; detector temperature: 55°C.

[0072] Sample testing: a. Standard and test sample preparation: Weigh 0.002g to 0.004g of standard and test sample, respectively, and add 2mL of mobile phase to prepare a 0.1% to 0.5% standard mixture. Refrigerate for >8 hours. b. Standard solution / sample testing: Edit the sample group to be tested, select the established sample group method, wait for the baseline to stabilize, click Run Queue, and start testing the samples.

[0073] Data processing: Based on the relationship between retention time and molecular weight, a calibration curve was established using the chemical workstation, and the sample spectrum was integrated and quantified. The chemical workstation automatically generated molecular weight and molecular weight distribution results.

[0074] In some embodiments of the present application, the density of the polysilsesquioxane is 1 g / cm 3 -1.3g / cm 3 For example, the density of the polysilsesquioxane can be 1 g / cm 3 -1.29g / cm 3 , 1.05g / cm 3 -1.25g / cm 3 , 1.08g / cm 3 -1.23g / cm 3 , 1.1g / cm 3 -1.2g / cm 3 , 1.15g / cm 3 -1.18g / cm 3 Etc., thus, the density of polysilsesquioxane is within the above range and is relatively low. Using it on the isolation membrane can reduce the weight of the battery and increase the energy density. In addition, under the premise of meeting the heat resistance requirements, the permeability of the isolation membrane can be improved, and the cycle performance of the battery using the isolation membrane will also be improved.

[0075] It is understood that the density of polysilsesquioxane refers to the mass per unit of actual volume of solid matter (excluding open and closed pores and interparticle pores) in a dense state. It can be obtained by the following method:

[0076] Determination was performed according to the reference standard GB / T24586: a certain mass of sample was weighed and placed in a true density tester. The test system was sealed, and helium was introduced according to the program. The pressure of the gas in the sample chamber and the expansion chamber was detected, and the true volume was calculated according to Bohr's law (PV=nRT). The density was calculated based on this volume and mass. National standard: GB / T24586 Determination of apparent density, true density and porosity of iron ore.

[0077] In some embodiments of the present application, the structural formula of the polysilsesquioxane includes:

[0078] Wherein, R1 and R2 each independently include an alkyl group of 1-12 carbon atoms, an unsaturated hydrocarbon group of 1-12 carbon atoms or a phenyl group, and n=50-1000.

[0079] For example, R1 and R2 each independently include an alkyl group of 1 to 12 carbon atoms, an alkyl group of 2 to 11 carbon atoms, an alkyl group of 3 to 10 carbon atoms, an alkyl group of 4 to 9 carbon atoms, an alkyl group of 5 to 8 carbon atoms, an alkyl group of 6 to 7 carbon atoms, etc.; R1 and R2 each independently include an unsaturated hydrocarbon group of 1 to 12 carbon atoms, an unsaturated hydrocarbon group of 2 to 11 carbon atoms, an unsaturated hydrocarbon group of 3 to 10 carbon atoms, an unsaturated hydrocarbon group of 4 to 9 carbon atoms, an unsaturated hydrocarbon group of 5 to 8 carbon atoms, an unsaturated hydrocarbon group of 6 to 7 carbon atoms, etc. unsaturated hydrocarbon groups, etc.; n = 50-999, n = 100-950, n = 200-900, n = 300-800, n = 400-700, n = 500-600, etc. Thus, the polysilsesquioxane of the above structural formula is used to improve the heat resistance and stability of the separator, reduce the probability of short circuit between the positive electrode and the negative electrode in the secondary battery, and improve the transmission efficiency of active metal ions. In addition, the probability of polysilsesquioxane clogging the micropores on the separator can be reduced, thereby improving the cycle performance of the secondary battery.

[0080] In some embodiments of the present application, the polysilsesquioxane comprises at least one of the following structural formulas:

[0081] Wherein, Ph represents phenyl, and n=50-1000.

[0082] For example, n=50-999, n=100-950, n=200-900, n=300-800, n=400-700, n=500-600, etc. It can be understood that the values ​​of n in the above structural formulas are independent of each other and may be equal or unequal.

[0083] Therefore, the use of polysilsesquioxane with the above-mentioned structural formula improves the heat resistance and stability of the isolation membrane, reduces the probability of short circuit between the positive and negative pole pieces in the secondary battery, and improves the transmission efficiency of active metal ions. In addition, it can reduce the probability of polysilsesquioxane clogging the micropores on the isolation membrane, thereby improving the cycle performance of the secondary battery.

[0084] In some embodiments of the present application, the isolation membrane includes a base membrane and a coating located on at least one side of the base membrane, wherein the coating includes the polysilsesquioxane. Thus, by placing the polysilsesquioxane in the coating, the probability of the polysilsesquioxane clogging the micropores of the base membrane can be reduced. Furthermore, the coating includes the polysilsesquioxane to form a heat-resistant coating. When the base membrane shrinks due to heat, the uniform polysilsesquioxane particles in the coating quickly contact and squeeze each other, providing a force opposite to the shrinkage direction of the isolation membrane, thereby reducing the degree of shrinkage of the isolation membrane, thereby enhancing the isolation membrane's deformation resistance and reducing the probability of short circuits between the positive and negative electrode sheets in the secondary battery. The polysilsesquioxane particles are evenly spaced, making the isolation membrane relatively flat and enhancing the permeability of the isolation membrane. Furthermore, the channels and distances for the transmission of active metal ions on the isolation membrane are similar, thereby improving the transmission efficiency of the active metal ions and enhancing the cycle performance of the secondary battery.

[0085] In some embodiments of the present application, the coating has a thickness of 0.3 μm to 3 μm. For example, the coating may have a thickness of 0.3 μm to 2.9 μm, 0.5 μm to 2.7 μm, 0.7 μm to 2.5 μm, 1 μm to 2.3 μm, 1.3 μm to 2 μm, or 1.5 μm to 2.8 μm. Therefore, when the coating thickness is within the above range, when the base film shrinks due to heat, the uniform polysilsesquioxane particles in the coating quickly contact and squeeze each other, providing a force opposite to the shrinkage direction of the separator, thereby reducing the degree of shrinkage of the separator, thereby enhancing the separator's deformation resistance and reducing the probability of short circuits between the positive and negative electrode sheets in the secondary battery. The uniform spacing between the polysilsesquioxane particles makes the separator relatively flat, enhancing the permeability of the separator. Furthermore, the channels and distances for active metal ions to be transmitted on the separator are similar, thereby improving the transmission efficiency of the active metal ions and enhancing the cycle performance of the secondary battery. In other embodiments of the present application, the thickness of the coating is 0.5 μm-2 μm.

[0086] In some embodiments of the present application, the coating further comprises a binder, wherein the binder comprises at least one of polyacrylic acid, polyacrylate, polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorine-containing acrylate resin. Thus, by adding the above-mentioned binder, the polysilsesquioxane can be firmly fixed to the base film, reducing the probability of the polysilsesquioxane falling off, reducing the probability of short circuits between the positive and negative electrodes in the secondary battery, improving the transmission efficiency of active metal ions, and enhancing the cycle performance of the secondary battery.

[0087] In some embodiments of the present application, the mass ratio of the polysilsesquioxane to the binder is (5-25):1. For example, the mass ratio of the polysilsesquioxane to the binder can be (5-24):1, (7-21):1, (10-20):1, (12-19):1, (13-18):1, (15-17):1, etc. Thus, the mass ratio of the polysilsesquioxane to the binder is controlled within the above range, which can firmly fix the polysilsesquioxane on the base film, reduce the probability of polysilsesquioxane falling off, reduce the probability of short circuit between the positive electrode and the negative electrode in the secondary battery, improve the transmission efficiency of the active metal ions, and enhance the cycle performance of the secondary battery. In other embodiments of the present application, the mass ratio of the polysilsesquioxane to the binder is (8-20):1.

[0088] In some embodiments of the present application, the thickness of the base film is 4 μm-20 μm. For example, the thickness of the base film can be 4 μm-19 μm, 5 μm-18 μm, 6 μm-17 μm, 7 μm-16 μm, 8 μm-15 μm, 9 μm-14 μm, 10 μm-13 μm, 11 μm-12 μm, etc. Thus, the thickness of the base film is controlled within the above range, thereby improving the transmission efficiency of active metal ions and enhancing the cycle performance of the secondary battery. In other embodiments of the present application, the thickness of the base film is 5 μm-18 μm.

[0089] In some embodiments of the present application, the pore size of the base membrane is 0.02μm-0.08μm. For example, the pore size of the base membrane can be 0.02μm-0.079μm, 0.03μm-0.07μm, 0.04μm-0.07μm, 0.04μm-0.06μm, 0.04μm-0.05μm, etc. The pore size of the base membrane is controlled within the above range, which can reduce the probability of polysilsesquioxane blocking the micropores of the base membrane, improve the transmission efficiency of active metal ions, and enhance the cycle performance of the secondary battery. In other embodiments of the present application, the pore size of the base membrane is 0.03μm-0.06μm.

[0090] In some embodiments of the present application, the porosity of the base membrane is 30%-70%. For example, the porosity of the base membrane can be 30%-69%, 35%-65%, 40%-60%, 45%-55%, or 50%-55%. Thus, controlling the porosity of the base membrane within the above range can reduce the probability of polysilsesquioxane clogging the micropores of the base membrane, thereby improving the transmission efficiency of active metal ions and enhancing the cycle performance of the secondary battery. In other embodiments of the present application, the porosity of the base membrane is 35%-65%.

[0091] A second aspect of the present application provides a method for preparing an isolation membrane, comprising:

[0092] S10: preparing an isolation film containing polysilsesquioxane, wherein the D v 90particle size is aμm, D v 10 Particle size is b μm, D v 50Particle size is cμm, (ab) / c≤3.

[0093] According to the method of the present application, polysilsesquioxane is added during the preparation of the isolation membrane, and the particle size distribution of the polysilsesquioxane is controlled. On the one hand, polysilsesquioxane has excellent heat resistance, high mechanical strength and hardness, good chemical stability, and is insoluble in organic solvents, which improves the heat resistance and stability of the isolation membrane. When the isolation membrane shrinks due to heat, the uniform polysilsesquioxane particles quickly contact and squeeze each other, which can provide a force opposite to the shrinkage direction of the isolation membrane, thereby reducing the degree of shrinkage of the isolation membrane, thereby enhancing the deformation resistance of the isolation membrane and reducing the probability of short circuit between the positive and negative electrodes in the secondary battery. On the other hand, the polysilsesquioxane particles of the present application are uniform in size and uniformly spaced, making the isolation membrane relatively flat and enhancing the air permeability of the isolation membrane. In addition, the channels and distances for the transmission of active metal ions on the isolation membrane are similar, thereby improving the transmission efficiency of the active metal ions and improving the cycle performance of the secondary battery.

[0094] In some embodiments of the present application, including:

[0095] S100: preparing a coating on at least one side of a base film to obtain a release film, wherein the coating comprises the polysilsesquioxane.

[0096] By the above method, by setting polysilsesquioxane in the coating, the probability of polysilsesquioxane clogging the micropores of the base membrane can be reduced, and the coating includes polysilsesquioxane to form a heat-resistant coating. When the base membrane shrinks due to heat, the uniform polysilsesquioxane particles in the coating quickly contact and squeeze each other, which can provide a force opposite to the shrinkage direction of the isolation membrane, thereby reducing the degree of shrinkage of the isolation membrane, thereby enhancing the deformation resistance of the isolation membrane and reducing the probability of short circuit between the positive and negative electrode sheets in the secondary battery; the polysilsesquioxane particles are evenly spaced, making the isolation membrane relatively flat, enhancing the air permeability of the isolation membrane, and the channels and distances for the transmission of active metal ions on the isolation membrane are similar, thereby improving the transmission efficiency of the active metal ions and enhancing the cycle performance of the secondary battery.

[0097] In some embodiments of the present application, the polysilsesquioxane is prepared by the following method:

[0098] S101: hydrolyzing the organosiloxane monomer, adding a catalyst, and polycondensing under heating conditions to obtain polysilsesquioxane.

[0099] Thus, the polysilsesquioxane obtained through hydrolysis and polycondensation reaction has a uniform particle size distribution (i.e., (ab) / c is small) and is used in the isolation membrane, which can enhance the deformation resistance of the isolation membrane and reduce the probability of short circuit between the positive and negative pole pieces in the secondary battery; and the particle size of the polysilsesquioxane is uniform, and the spacing between the polysilsesquioxane particles is uniform, so that the isolation membrane is relatively flat, and the channels and distances for the transmission of active metal ions on the isolation membrane are similar, thereby improving the transmission efficiency of the active metal ions and enhancing the cycle performance of the secondary battery.

[0100] In some embodiments of the present application, the hydrolysis temperature of the organosiloxane monomer is 20°C-30°C. For example, the hydrolysis temperature can be 20°C-29°C, 21°C-28°C, 22°C-27°C, 23°C-26°C, 24°C-25°C, etc. Thus, within the above hydrolysis temperature range, the organosiloxane monomer is fully hydrolyzed, and the resulting polysilsesquioxane can be used in a separator to improve the cycle performance of a secondary battery.

[0101] In some embodiments of the present application, the heating temperature is 30°C-100°C. For example, the heating temperature can be 30°C-99°C, 35°C-95°C, 40°C-90°C, 45°C-85°C, 50°C-80°C, 55°C-75°C, 60°C-70°C, etc. Within the above heating temperature range, a polysilsesquioxane with a uniform particle size distribution can be obtained, which can improve the cycle performance of the secondary battery. In some embodiments of the present application, the heating temperature is 40°C-80°C.

[0102] Specifically, the organosiloxane monomer first hydrolyzes to form silanols, releasing alcohols to form a mixed solution. The alcohols increase the solubility of the organosiloxane monomer in the solution. Next, under the action of a catalyst, the silanols begin to condense, forming Si-O-Si bonds between the silanols, further forming a network structure, at which point nucleation begins. Finally, these nuclei continuously absorb silanols from the solution, continuing to grow until they become polysilsesquioxanes. The nucleation and nucleus growth processes compete with each other, and the reaction temperature influences both processes. When nucleation dominates, more nuclei are produced, resulting in a smaller polysilsesquioxane particle size; when nucleus growth dominates, the final microsphere size is larger. Increasing the temperature accelerates the reaction, resulting in the production of more nuclei at the beginning of the reaction, consuming more silanols. This limits the growth of nuclei in the later stages, resulting in a smaller polysilsesquioxane particle size. The heating temperature is controlled within the range of 30°C-100°C, which can reduce (ab) / c, promote the uniformity of the polysilsesquioxane particle size, and improve the cycle performance of the secondary battery.

[0103] In some embodiments of the present application, the catalyst includes at least one of ammonia, triethylamine, sodium hydroxide, magnesium hydroxide, or ammonium hydroxide. Thus, the catalyst can continuously and efficiently catalyze the polycondensation of hydrolyzed organosiloxane monomers, thereby obtaining polysilsesquioxanes with uniform particle size distribution, thereby improving the cycle performance of secondary batteries.

[0104] In some embodiments of the present application, the organosiloxane monomer includes:

[0105] Wherein, R3 includes any one of methyl and ethyl, and R4 includes any one of methyl, ethyl, phenyl, vinyl, allyl, and dodecyl. Thus, the above-mentioned organosiloxane monomer can be hydrolyzed and polycondensed to obtain a polysilsesquioxane with uniform particle size distribution, which can improve the cycle performance of secondary batteries.

[0106] In some embodiments of the present application, the organosiloxane monomer includes at least one of methyltrimethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, dodecyltrimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, phenyltriethoxysilane, dodecyltriethoxysilane, vinyltriethoxysilane, or allyltriethoxysilane. Thus, the organosiloxane monomer can be hydrolyzed and polycondensed to obtain a polysilsesquioxane with a uniform particle size distribution, thereby improving the cycling performance of a secondary battery.

[0107] Specifically, taking R3 and R4 as methyl groups as an example, the hydrolysis and polycondensation reaction process of the organosiloxane monomer is as follows:

[0108] As the above-mentioned base membrane, the present application has no special restrictions and any well-known porous structure base membrane with electrochemical stability and mechanical stability can be selected according to actual needs. For example, it can include a single-layer or multi-layer film containing at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, polyimide, polytetrafluoroethylene, and aramid membrane.

[0109] The third aspect of the present application provides a battery comprising the separator described in the first aspect of the present application or the separator prepared by the method described in the second aspect, thereby having an excellent cycle life.

[0110] A battery is a battery that can be recharged to activate the active materials after discharge and continue to be used.

[0111] It is understandable that the battery proposed in this application can be a lithium-ion battery or a sodium-ion battery.

[0112] Typically, a battery consists of a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the battery's charge and discharge processes, active metal ions are inserted and removed between the positive and negative electrode sheets. The separator is placed between the positive and negative electrode sheets to provide isolation. The electrolyte conducts the active metal ions between the positive and negative electrode sheets.

[0113] [Positive electrode]

[0114] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0115] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0116] In some embodiments of the present application, the positive electrode plate includes a positive electrode current collector, which can be a metal foil, a metal foam 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 electrode, carbon, nickel or titanium, etc. can be used. The composite current collector may include a polymer material base and a metal layer. The foam metal may be nickel foam, copper foam, aluminum foam, alloy foam, etc. The composite current collector can be formed by forming a metal material (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.).

[0117] In some embodiments of the present application, the positive electrode plate 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 battery positive electrodes can be used. Those skilled in the art can select according to actual needs.

[0118] When the battery is a lithium-ion battery, as an example, the positive electrode active material may include, but is not limited to, at least one of a lithium transition metal oxide, an olivine-structured lithium-containing phosphate, 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 olivine-structured lithium-containing phosphates 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 iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their modified compounds. These materials can all be obtained through commercial channels.

[0119] When the battery is a sodium ion battery, as an example, the positive electrode active material may include, but is not limited to, at least one of a layered transition metal oxide, a polyanion compound, and a Prussian blue analog.

[0120] Examples of the layered transition metal oxides include:

[0121] Na 1-x Cu h Fe k Mn l M 1 m O 2-y , where M 1 is 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;

[0122] 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;

[0123] Na a Li b Ni c Mn d Fe e O2, of which 0.67 <a≤1,0<b<0.2,0<c<0.3,0.67<d+e<0.8,b+c+d+e=1。

[0124] Examples of the polyanionic compound include:

[0125] 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, X1 is at least one of F, Cl, and Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2;

[0126] 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;

[0127] Na p M 5 q (SO4)3, where M 5 is at least one of Mn, Fe, Co, Ni, Cu, and Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0128] 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.

[0129] As an example of the above Prussian blue analogues, for example, the following can be listed:

[0130] 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 + [[ID=6​​​​​​​​​​​​​​​​​​​​​Each independently represents a cation of at least one transition metal element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, and W.

[0131] The battery's charge and discharge processes are accompanied by the intercalation and deintercalation of Li or Na, and the molar content of Li or Na varies when the battery is discharged to different states. The molar content of Li or Na in the examples of the present application regarding the positive electrode materials is the initial state of the material, i.e., the state before the materials are added. When the positive electrode material is used in a battery system, the molar content of Li or Na will change after charge and discharge cycles.

[0132] In the examples of the present application regarding the positive electrode materials, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0133] The modified compounds of the above materials may be doping-modified and / or surface-coated modified materials.

[0134] The positive electrode active material layer may also optionally include a binder, a conductive agent, and other optional auxiliary agents.

[0135] As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene, and carbon nanofibers.

[0136] As an example, the adhesive may 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).

[0137] [Positive electrode]

[0138] 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.

[0139] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0140] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0141] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is 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, 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 traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0142] In some embodiments, the negative electrode active material layer may further 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).

[0143] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0144] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0145] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0146] [Electrolyte]

[0147] The electrolyte solution may include an electrolyte salt and a solvent.

[0148] 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 bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0149] As an example, when the battery is a sodium ion battery, the electrolyte sodium salt includes at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethylsulfonyl)imide.

[0150] 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).

[0151] In some embodiments of the present application, the electrolyte further includes additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives capable of improving certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance.

[0152] The embodiment of the present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square or any other shape. FIG1 shows a battery cell 5 with a square structure as an example.

[0153] In some embodiments, the battery cell may include an outer packaging for encapsulating the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0154] In some embodiments, the outer packaging may include a housing and a cover. The housing may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. The housing may have an opening communicating with the receiving cavity, and the cover may be positioned over the opening to seal the receiving cavity.

[0155] The positive electrode sheet, negative electrode sheet, and separator can be wound or laminated to form an electrode assembly. The electrode assembly is encapsulated in the housing. The number of electrode assemblies contained in a battery cell can include one or more, which can be adjusted according to demand.

[0156] In some embodiments, the outer packaging of the battery cell may include a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0157] The outer packaging of the battery cell may also include a soft bag, such as a bag-type soft bag. The material of the soft bag may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0158] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain multiple batteries, and the specific number may be adjusted according to the application and capacity of the battery module.

[0159] Figure 2 shows an example battery module 4. Referring to Figure 2 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0160] The battery module 4 may further include a housing having a housing space, wherein a plurality of battery cells 5 are housed in the housing space. In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0161] Figures 3 and 4 illustrate an example battery pack 1. Referring to Figures 3 and 4 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0162] In a fourth aspect, the present application provides an electrical device comprising the battery described in the third aspect. Specifically, the battery can serve as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., 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.

[0163] FIG5 shows an example of an electric device, which includes a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0164] As another example, electric devices may include mobile phones, tablet computers, and laptop computers. These electric devices are generally required to be lightweight and thin, and may use batteries as power sources.

[0165] 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 with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0166] Example 1

[0167]

Isolation film preparation

[0168] (1) Preparation of polysilsesquioxane

[0169] In a 5L flask equipped with a stirrer, a thermometer and a reflux condenser, 3000g of deionized water and 2g of hydrochloric acid were added, stirring was started and 315.5g of methyltrimethoxysilane was added. After the hydrolysis reaction at 25°C for 1h, 10g of triethylamine was added and the heating reaction was continued for 12h to obtain a white viscous solution. The solution was washed with deionized water until neutral, then dried and ground to obtain polysilsesquioxane.

[0170] (2) Preparation of isolation membrane

[0171] A commercially available PE (polyethylene) polymer microporous film with a thickness of 7 μm and an average pore size of 0.08 μm (from Zhuogao Electronic Technology Co., Ltd.) was used as the base film. 150 g of the polysilsesquioxane and polyacrylic acid binder obtained in step (1) were added to 850 g of deionized water in a mass ratio of 10:1 and stirred to obtain a slurry. The slurry was coated on the base film and dried in an oven. The coating density of the polysilsesquioxane and binder on the base film was 0.5 g / m 2 , and then rolled up to finally obtain the isolation film. The specific implementation parameters are shown in Table 1.

[0172]

Positive electrode preparation

[0173] Polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive carbon black, and N-methylpyrrolidone (NMP) were mixed in a mass ratio of 1.2:58.38:0.42:40 and stirred thoroughly to prepare a positive electrode slurry. 2 The loading amount is evenly coated on the positive electrode current collector aluminum foil, and then dried, cold pressed and cut to obtain the positive electrode sheet.

[0174]

Negative electrode sheet preparation

[0175] Artificial graphite, conductive agent acetylene black, binder styrene butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na) were added into deionized water in a mass ratio of 96.2:1.0:1.6:1.2, and stirred thoroughly to prepare a negative electrode slurry (solid content of 63%). 2 The loading amount is coated on the negative electrode current collector copper foil, and then dried, cold pressed and cut to obtain the negative electrode sheet.

[0176]

Electrolyte preparation

[0177] At 25°C, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent, and then LiPF6 is dissolved in the above mixed solvent to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0178] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in order to form a battery cell; the battery cell is placed in an outer package, and the prepared electrolyte is added. After packaging, standing, forming, aging and other processes, a battery is obtained.

[0179] Except for the parameters that are different from those of Example 1 (see Table 1), Example 2-37 is the same as Example 1 in other respects.

[0180] Example 38

[0181]

Isolation film preparation

[0182] (1) Preparation of polysilsesquioxane

[0183] In a 5L flask equipped with a stirrer, a thermometer and a reflux condenser, 3000g of deionized water and 2g of hydrochloric acid were added, stirring was started and 315.5g of methyltrimethoxysilane was added. After the hydrolysis reaction at 25°C for 1h, 10g of triethylamine was added and the heating reaction was continued for 12h to obtain a white viscous solution. The solution was washed with deionized water until neutral, then dried and ground to obtain polysilsesquioxane.

[0184] (2) Preparation of isolation membrane

[0185] The polysilsesquioxane, polyethylene and other raw materials obtained in step (1) are pretreated according to the formula and then transported to the extrusion system. 2) Casting: The pretreated raw materials are melted and plasticized in the extrusion system and then extruded from the die head to form a melt isolation membrane. The melt is cast to form a base membrane with a specific crystalline structure. 3) Heat treatment: The base membrane is heat-treated to obtain a hard elastic film. 4) Stretching: The hard elastic film is cold-stretched and hot-stretched to form a nanoporous membrane. 5) Slitting: The nanoporous membrane is cut into finished membranes. The thickness of the isolation membrane is 8μm, the average pore size is 0.08μm, and the porosity is 50%.

[0186] The rest of the preparation method is the same as that in Example 1.

[0187] Except for the parameters that are different from those of Example 38 (see Table 1), Examples 39-46 are the same as Example 38.

[0188] The parameters of the isolation membranes of Examples 1-46 and Comparative Examples 1-2 of the present application are shown in Table 1. The isolation membrane of Comparative Example 1 adopts a commercially available PE (polyethylene) polymer microporous film with a thickness of 7 μm and an average pore size of 0.08 μm (from Zhuogao Electronic Technology Co., Ltd.).

[0189] Table 1

[0190] In Table 1, “ / ” indicates that no addition was made.

[0191] The structural formulas of the polysilsesquioxanes used in the examples and comparative examples in Table 1 are shown in Table 2.

[0192] Table 2

[0193] Performance testing:

[0194] 1. Determination of polysilsesquioxane particle size

[0195] According to the standard GB / T 19077-2016, the laser particle size analyzer (such as Malvern Master Size 3000) was used to measure the D and B of polysilsesquioxane. v 90 particle size, D v 10 particle size, D v 50 particle size.

[0196] Figure 6 is a particle size distribution diagram of Example 6 of the present application, and it can be obtained that a=0.93, b=0.49, c=0.68, (ab) / c=0.647. It can be seen that the polysilsesquioxane prepared in Example 6 of the present application has a uniform particle size distribution and a uniform particle size.

[0197] 2. The polysilsesquioxane prepared in Example 1 was subjected to a scanning electron microscope, and Figure 7 was obtained. It can be seen that the polysilsesquioxane prepared in Example 1 of the present application has a uniform particle size distribution and a uniform particle size.

[0198] 3. Determination of weight average molecular weight of polysilsesquioxane

[0199] Ultra-high performance polymer chromatograph: ACQUITY APC; detector: ACQUITY differential refractive index detector.

[0200] Parameter settings: injection volume: 0 μL to 50 μL (depending on sample concentration); pump flow rate: 0.2 mL / min; mobile phase: 30 mol / L LiBr in NMP (N-methylpyrrolidone) solution; sealing cleaning liquid: isopropanol; pre-column: PLgel10umMiniMIX-BGuard (size: 50 mm × 4.6 mm × 2); analytical phase: PLgel10umMiniMIX-B (size: 250 mm × 4.6 mm); standard: polystyrene sleeve; running time: 30 min; detector: ACQUITY differential refractive index (RI) detector; column oven temperature: 90°C; detector temperature: 55°C.

[0201] Sample testing: a. Standard and test sample preparation: Weigh 0.002g to 0.004g of standard and test sample, respectively, and add 2mL of mobile phase to prepare a 0.1% to 0.5% standard mixture. Refrigerate for >8 hours. b. Standard solution / sample testing: Edit the sample group to be tested, select the established sample group method, wait for the baseline to stabilize, click Run Queue, and start testing the samples.

[0202] Data processing: Based on the relationship between retention time and molecular weight, a calibration curve was established using the chemical workstation, and the sample spectrum was integrated and quantified. The chemical workstation automatically generated molecular weight and molecular weight distribution results.

[0203] 4. Polysilsesquioxane Density Determination

[0204] Weigh a sample of a specified mass and place it in a true density tester. Close the test system, introduce helium according to the program, and measure the pressure of the gas in the sample chamber and expansion chamber. The true volume is then calculated according to Bohr's law (PV = nRT). The density is then calculated based on this volume and mass. National Standard: GB / T 24586 Determination of Apparent Density, True Density, and Porosity of Iron Ore.

[0205] 5. Thermal shrinkage test of isolation film

[0206] Sample preparation: The isolation film prepared above was punched into samples with a width of 50 mm and a length of 100 mm using a punching machine. Five parallel samples were placed on A4 paper, and then the A4 paper containing the samples was placed on corrugated paper with a thickness of 1 mm to 5 mm.

[0207] Sample test: Set the temperature of the blast oven to 150°C. After the temperature reaches the set temperature and stabilizes for 30 minutes, place the A4 paper placed on the corrugated paper into the blast oven and start timing. After the set time (1 hour in the embodiment of this application) is reached, measure the length and width of the isolation film, and mark the values ​​as m and n, respectively.

[0208] Calculation of thermal shrinkage: longitudinal (MD) thermal shrinkage = [(100-m) / 100] × 100%, transverse (TD) thermal shrinkage = [(50-n) / 50] × 100%, and the average value of 5 parallel samples is taken as the test result.

[0209] 6. Secondary battery capacity retention test (cycle performance)

[0210] At 25°C, charge at a constant current of 1 / 3C to 3.6V, then charge at a constant voltage of 3.6V to a current of 0.05C. After 5 minutes, discharge at 1 / 3C to 2.5V. The resulting capacity is recorded as the initial capacity C0. Repeat these steps and simultaneously record the discharge capacity C1000 of the secondary battery after the 1000th cycle. The secondary battery capacity retention rate after 1000 cycles, P1000, = C1000 / C0 × 100%. The results are shown in Table 3.

[0211] Table 3

[0212] As can be seen from Table 3, in Examples 1-46 of the present application, polysilsesquioxane was added to the separator and the particle size distribution of the polysilsesquioxane was controlled. The separator had a small shrinkage rate and excellent battery cycle performance. Compared with Examples 1-46, the separator of Comparative Example 1 did not add polysilsesquioxane and used a polyethylene film. In Comparative Example 2, the particle size distribution of the polysilsesquioxane was not within the range of ≤3, the thermal shrinkage rate of the separator was significantly increased, and the battery cycle performance was significantly reduced. It can be seen that the separators of the examples of the present application have good heat resistance and stability, and the battery cycle life is excellent.

[0213] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A separation film, wherein: The isolation film includes polysilsesquioxane, wherein D v 90 particle size is aμm, D v 10 Particle size is b μm, D v 50Particle size is cμm, (ab) / c≤3.

2. The isolation film according to claim 1, wherein: 0.4≤(ab) / c≤1.

5.

3. The isolation film according to claim 1 or 2, wherein: a=0.5-5, optionally, a=0.6-2.

5.

4. The isolation film according to any one of claims 1 to 3, wherein: b=0.05-1.5, optionally, b=0.1-1.

3.

5. The isolation film according to any one of claims 1 to 4, wherein: c=0.1-3, optionally, c=0.4-1.

7.

6. The isolation film according to any one of claims 1 to 5, wherein: The weight average molecular weight of the polysilsesquioxane is 10,000-100,000, and can be optionally 30,000-80,000.

7. The isolation film according to any one of claims 1 to 6, wherein: The density of the polysilsesquioxane is 1 g / cm 3 -1.3g / cm 3 , optional 1g / cm 3 -1.2g / cm 3 .

8. The isolation film according to any one of claims 1 to 7, wherein: The structural formula of the polysilsesquioxane includes: Wherein, R1 and R2 each independently include an alkyl group of 1-12 carbon atoms, an unsaturated hydrocarbon group of 1-12 carbon atoms or a phenyl group, and n=50-1000.

9. The isolation film according to any one of claims 1 to 8, wherein: The polysilsesquioxane comprises at least one of the following structural formulas: Wherein, Ph represents phenyl, and n=50-1000.

10. The isolation film according to any one of claims 1 to 9, wherein: The isolation film includes a base film and a coating layer located on at least one side of the base film, wherein the coating layer includes the polysilsesquioxane.

11. The isolation film according to claim 10, wherein: The thickness of the coating is 0.3 μm-3 μm, and can be optionally 0.5 μm-2 μm.

12. The isolation film according to claim 10 or 11, wherein: The coating also includes a binder, which includes at least one of polyacrylic acid, polyacrylate, polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer or fluorine-containing acrylate resin.

13. The isolation film according to claim 12, wherein: The mass ratio of the polysilsesquioxane to the binder is (5-25):1, and can be optionally (8-20):

1.

14. The isolation film according to any one of claims 10 to 13, wherein: At least one of the following conditions is met: The thickness of the base film is 4 μm-20 μm, and can be 5 μm-18 μm; The pore size of the base film is 0.02 μm-0.08 μm, and can be 0.03 μm-0.06 μm; The porosity of the base film is 30%-70%, and can be optionally 35%-65%.

15. A method for preparing an isolation film, wherein: include: Preparation of a polysilsesquioxane-containing isolation film, wherein the polysilsesquioxane has a D v 90 particle size is aμm, D v 10 Particle size is b μm, D v 50Particle size is cμm, (ab) / c≤3.

16. The method according to claim 15, wherein: include: A coating is prepared on at least one side of the base film to obtain a release film, wherein the coating includes the polysilsesquioxane.

17. The method according to claim 15 or 16, wherein: The polysilsesquioxane is prepared by the following method: The organosiloxane monomer is hydrolyzed, a catalyst is added, and polycondensation is carried out under heating conditions to obtain polysilsesquioxane.

18. The method according to claim 17, wherein: The temperature for hydrolyzing the organosiloxane monomer is 20°C-30°C.

19. The method according to claim 17 or 18, wherein: The heating temperature is 30°C-100°C, and can be optionally 40°C-80°C.

20. The method according to any one of claims 17 to 19, wherein: The catalyst includes at least one of ammonia water, triethylamine, sodium hydroxide, magnesium hydroxide or ammonium hydroxide.

21. The method according to any one of claims 17 to 20, wherein: The organosiloxane monomers include: Among them, R3 includes any one of methyl and ethyl, and R4 includes any one of methyl, ethyl, phenyl, vinyl, allyl, and dodecyl.

22. The method according to any one of claims 17 to 21, wherein: The organosiloxane monomer includes at least one of methyltrimethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, dodecyltrimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, phenyltriethoxysilane, dodecyltriethoxysilane, vinyltriethoxysilane or allyltriethoxysilane.

23. A battery, wherein: An isolation film comprising the isolation film described in any one of claims 1 to 14 or an isolation film prepared by the method described in any one of claims 15 to 22.

24. An electrical device, wherein: Comprising the battery of claim 23.

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