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 polysilsesquioxane, the Dv90 particle size of the polysilsesquioxane is a [mu] m, the Dv10 particle size of the polysilsesquioxane is b [mu] m, the Dv50 particle size of the polysilsesquioxane is c [mu] m, and (a-b) / c is less than or equal to 3. The secondary battery containing the isolating membrane is good in cycle performance.

Description

[0001] This application is a divisional application of the invention patent application with application number 202311594479.1, application date November 24, 2023, entitled "Separation membrane and preparation method thereof, battery and electrical device". Technical Field

[0002] This application belongs to the field of secondary battery technology, specifically relating to a separator and its preparation method, a battery, and an electrical device. Background Technology

[0003] Secondary batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles and electric cars, as well as in military equipment and aerospace and other fields.

[0004] Separator membranes are an important component of secondary batteries. However, existing separator membranes have poor heat resistance and stability, and low transport efficiency of active metal ions, resulting in poor cycle performance of secondary batteries containing them. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a separator membrane, which aims to solve the problem of poor cycle performance of batteries containing it.

[0006] To achieve the above objectives, a first aspect of this application provides a separating membrane comprising a polysilsesquioxane, wherein the polysilsesquioxane has a D... v 90 particles with a diameter of a μm, D v 10 Particle size is bμm, D v 50 Particle size is cμm, (ab) / c≤3.

[0007] This application includes at least the following beneficial effects: In this application, polysilsesquioxane is added to the separator and the particle size distribution of polysilsesquioxane is controlled. The channels and distances for the transport of active metal ions on the separator are similar, which improves the transport efficiency of active metal ions and enhances the cycle performance of the secondary battery.

[0008] In some embodiments of this application, 0.4 ≤ (ab) / c ≤ 1.5. This improves the cycle performance of the secondary battery.

[0009] In some embodiments of this application, a = 0.5-5, and optionally, a = 0.6-2.5. This improves the cycle performance of the secondary battery.

[0010] In some embodiments of this application, b = 0.05-1.5, and optionally, b = 0.1-1.3. This improves the cycle performance of the secondary battery.

[0011] In some embodiments of this application, c = 0.1-3, and optionally, c = 0.4-1.7. This improves the cycle performance of the secondary battery.

[0012] In some embodiments of this application, the polysilsesquioxane has a weight-average molecular weight of 10,000-100,000, optionally 30,000-80,000. This can improve the cycle performance of the secondary battery.

[0013] In some embodiments of this application, the density of the polysilsesquioxane is 1 g / cm³. 3 -1.3g / cm 3 1g / cm can be selected. 3 -1.2g / cm 3 This can improve the cycle performance of secondary batteries.

[0014] In some embodiments of this application, the structural formula of the polysilsesquioxane includes:

[0015]

[0016] R1 and R2 each independently include an alkyl group with 1-12 carbon atoms, an unsaturated hydrocarbon group with 1-12 carbon atoms, or a phenyl group, n = 50-1000.

[0017] This can improve the cycle performance of secondary batteries.

[0018] In some embodiments of this application, the polysilsesquioxane comprises at least one of the following structural formulas:

[0019]

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

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

[0022] In some embodiments of this application, the separator includes a base film and a coating located on at least one side of the base film, the coating comprising the polysilsesquioxane. This can improve the cycle performance of the secondary battery.

[0023] In some embodiments of this application, the thickness of the coating is 0.3 μm-3 μm, optionally 0.5 μm-2 μm. This can improve the cycle performance of the secondary battery.

[0024] In some embodiments of this application, the coating further includes an adhesive, which comprises at least one selected from 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 fluorinated acrylate resin. This can improve the cycle performance of the secondary battery.

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

[0026] In some embodiments of this application, the thickness of the base film is 4μm-20μm, optionally 5μm-18μm. This improves the cycle performance of the secondary battery.

[0027] In some embodiments of this application, the pore size of the base film is 0.02 μm-0.08 μm, optionally 0.03 μm-0.06 μm. This improves the cycle performance of the secondary battery.

[0028] In some embodiments of this application, the porosity of the base film is 30%-70%, optionally 35%-65%. This can improve the cycle performance of the secondary battery.

[0029] A second aspect of this application provides a method for preparing a separator membrane, comprising:

[0030] Prepare a separator containing polysilsesquioxane, wherein the polysilsesquioxane has a D... v 90 particles with a diameter of a μm, D v 10 Particle size is bμm, D v 50 Particle size is cμm, (ab) / c≤3.

[0031] Therefore, by using the method of this application, polysilsesquioxane is added during the preparation of the separator, and the particle size distribution of polysilsesquioxane is controlled, which improves the transport efficiency of active metal ions and enhances the cycle performance of the secondary battery.

[0032] In some embodiments of this application, a coating is prepared on at least one side of a base film to obtain a separator film, the coating comprising the polysilsesquioxane. Thus, by incorporating the polysilsesquioxane into the coating, the cycle performance of the secondary battery can be improved.

[0033] In some embodiments of this application, the polysilsesquioxane is prepared by the following method: hydrolyzing an organosiloxane monomer, adding a catalyst, and polycondensing under heating conditions to obtain the polysilsesquioxane. Thus, the polysilsesquioxane obtained through hydrolysis and polycondensation reactions can be used in separator membranes to improve the cycle performance of secondary batteries.

[0034] In some embodiments of this application, the organosiloxane monomer is hydrolyzed at a temperature of 20°C-30°C. Therefore, within this hydrolysis temperature range, the organosiloxane monomer is fully hydrolyzed, and the resulting polysilsesquioxane, when used in a separator membrane, can improve the cycle performance of the secondary battery.

[0035] In some embodiments of this application, the heating temperature is 30℃-100℃, optionally 40℃-80℃. 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 this application, the catalyst includes at least one selected from ammonia, triethylamine, sodium hydroxide, magnesium hydroxide, or ammonium hydroxide. This results in polysilsesquioxanes with uniform particle size distribution, which can improve the cycle performance of secondary batteries.

[0037] In some embodiments of this application, the organosiloxane monomer comprises:

[0038]

[0039] R3 includes any one of methyl or ethyl, and R4 includes any one of methyl, ethyl, phenyl, vinyl, allyl, and dodecyl. This yields polysilsesquioxane with a uniform particle size distribution, which can improve the cycle performance of secondary batteries.

[0040] In some embodiments of this application, the organosiloxane monomer includes at least one selected from methyltrimethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, dodecyltrimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, phenyltriethoxysilane, dodecyltriethoxysilane, vinyltriethoxysilane, or allyltriethoxysilane. This results in polysilsesquioxanes with uniform particle size distribution, which can improve the cycle performance of secondary batteries.

[0041] A third aspect of this application provides a battery comprising the separator described in the first aspect of this application or a separator prepared using the method described in the second aspect of this application. Therefore, the battery exhibits excellent cycle performance.

[0042] The fourth aspect of this application provides an electrical device that includes the battery described in the third aspect.

[0043] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0044] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0045] Figure 1 This is a schematic diagram of the structure of a battery according to one embodiment of this application;

[0046] Figure 2 This is a schematic diagram of the structure of a battery module according to one embodiment of this application;

[0047] Figure 3 This is a schematic diagram of the structure of a battery pack according to one embodiment of this application;

[0048] Figure 4 yes Figure 3 Exploded view;

[0049] Figure 5 This is a schematic diagram of one embodiment of an electrical device that uses a battery as a power source;

[0050] Figure 6 This is a particle size distribution diagram of the polysilsesquioxane in Example 1 of this application;

[0051] Figure 7 This is a scanning electron microscope image of the polysilsesquioxane of Example 1 of this application.

[0052] Explanation of reference numerals in the attached figures:

[0053] 1: Battery pack; 2: Upper casing; 3: Lower casing; 4: Battery module; 5: Individual battery cell. Detailed Implementation

[0054] The embodiments of the technical solution of this application are described in detail below. These embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore merely examples and should not be used to limit the scope of protection of this application.

[0055] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0056] For the sake of brevity, this article only discloses some specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0058] With the technological development and increasing demand for electric vehicles and rechargeable mobile devices, secondary batteries, as a representative of the new energy field, have seen rapid development in related research. Secondary batteries are small in size and weight, making them easy to carry and use; they have high specific energy, providing greater energy storage capacity; and lithium-ion batteries have no memory effect, eliminating the need for complete discharge and recharging. Therefore, secondary batteries have broad application prospects.

[0059] The separator is a crucial component of a rechargeable battery. It is a thin film with a microporous structure, serving two main functions: firstly, it separates the positive and negative electrodes, preventing short circuits caused by contact between them; secondly, the 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 of 130℃-150℃, they undergo severe shrinkage, resulting in low transport efficiency of active metal ions and poor cycle performance in rechargeable batteries containing them.

[0060] In this application, polysilsesquioxane is added to the separator, and the particle size distribution ((ab) / c) 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 separator. When the separator shrinks due to heat, the uniform polysilsesquioxane particles come into rapid contact and are squeezed together, which can provide a force opposite to the shrinkage direction of the separator, thereby reducing the degree of shrinkage of the separator and enhancing its resistance to deformation, thus 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 ​​this application is within the above-mentioned range, with uniform particle size and uniform spacing between the polysilsesquioxane particles, making the separator relatively flat. The channels and distances for the transport of active metal ions on the separator are similar, which improves the transport efficiency of active metal ions and enhances the cycle performance of the secondary battery.

[0061] The separator disclosed in this application is applicable to secondary batteries, and the battery disclosed in this application can be used in electrical devices that use batteries as a power source or in 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, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0062] A first aspect of this application discloses a separator membrane comprising a polysilsesquioxane, wherein the polysilsesquioxane has a D... v 90 particles with a diameter of a μm, D v 10 Particle size is bμm, D v 50 Particle size is cμm, (ab) / c≤3.

[0063] This application includes at least the following beneficial effects: Adding polysilsesquioxane to the separator and controlling the particle size distribution of the polysilsesquioxane improves the heat resistance and stability of the separator. On the one hand, polysilsesquioxane possesses excellent heat resistance, high mechanical strength and hardness, good chemical stability, and is insoluble in organic solvents. When the separator shrinks due to heat, the uniform polysilsesquioxane particles rapidly contact and compress, providing a force opposite to the direction of separator shrinkage, thereby reducing the degree of separator shrinkage and enhancing its resistance to deformation, thus reducing the probability of short circuits between the positive and negative electrodes in the secondary battery. On the other hand, the polysilsesquioxane particles in this application are uniform in size and spacing, resulting in a relatively flat separator, enhanced permeability, and similar channels and distances for the transport of active metal ions on the separator, improving the transport efficiency of active metal ions and enhancing the cycle performance of the secondary battery.

[0064] It is understood that the polysilsesquioxane of this application embodiment has dual organic and inorganic characteristics, 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. Silicon carbon materials that can resist oxygen degradation are deposited on the surface of the separator, reducing oxygen contact and slowing down heat transfer, thereby playing a flame retardant role and further improving the heat resistance of the battery.

[0065] It is understood that, in the embodiments of this application, D v 90% particle size refers to the particle size corresponding to a cumulative volume distribution percentage of 90%, meaning that particles smaller than this size account for 90% of the total particle volume; D v 50% particle size refers to the particle size at which the cumulative volume distribution percentage reaches 50%, meaning that particles larger than this size account for 50% of the total particle volume, and particles smaller than this size also account for 50% of the total particle volume. v The particle size of 10 refers to the particle size corresponding to a cumulative volume distribution percentage of 10%, that is, the volume content of particles smaller than this size accounts for 10% of all particles. The above three particle size values ​​can be determined using instruments and methods known in the art, such as referring to the standard GB / T 19077-2016 and using a laser particle size analyzer (e.g., Malvern Master Size 3000).

[0066] It is understood that (ab) / c can be interpreted as the particle size distribution span of polysilsesquioxane, a measure of the width of the particle size distribution. The closer the span is to 0, the more uniform the particle size and the higher the dimensional consistency. In the embodiments of this 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. Within the above range, the spacing between polysilsesquioxane particles is uniform, making the separator membrane relatively flat, enhancing the air permeability of the separator membrane, and the channels and distances for the transport of active metal ions on the separator membrane are similar, improving the transport efficiency of active metal ions and enhancing the cycle performance of the secondary battery. In some other embodiments of this application, 0.4 ≤ (ab) / c ≤ 1.5.

[0067] In some embodiments of this 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., thereby, the D of the polysilsesquioxane... v Particle sizes 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 transport efficiency of active metal ions. Furthermore, it can reduce the probability of polysilsesquioxane clogging the micropores on the separator, thus improving the cycle performance of the secondary battery. In some other embodiments of this application, a = 0.6-2.5.

[0068] In some embodiments of this 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 10. Particle sizes 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, improve the transport efficiency of active metal ions, and further reduce the probability of polysilsesquioxane clogging the micropores on the separator, thus improving the cycle performance of the secondary battery. In some other embodiments of this application, b = 0.1-1.3.

[0069] In some embodiments of this 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... v50. Particle sizes 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, improve the transport efficiency of active metal ions, and further reduce the probability of polysilsesquioxane clogging the micropores on the separator, thus improving the cycle performance of the secondary battery. In some other embodiments of this application, c = 0.4-1.7.

[0070] In some embodiments of this 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. Therefore, when the weight-average molecular weight of the polysilsesquioxane is within the above range, a polysilsesquioxane with uniform particle size distribution can be obtained, improving the heat resistance and stability of the separator, reducing the probability of short circuits between the positive and negative electrodes in the secondary battery, and improving the transport efficiency of active metal ions. Furthermore, it can reduce the probability of the polysilsesquioxane clogging the micropores on the separator, thus improving the cycle performance of the secondary battery. In other embodiments of this application, the weight-average molecular weight of the polysilsesquioxane is 30,000-80,000.

[0071] It is understood that "weight-average molecular weight of polysilsesquioxane" has a well-known meaning in the art and can be determined using instruments and methods well-known in the art. For example, it can be obtained by the following method:

[0072] The determination was performed using gel permeation chromatography, in accordance with standard GB / T21863-2008. Specifically, in the embodiments of this application, the following method was used: an ultra-high performance polymer chromatograph (UHPLC) was employed; the detector was an ACQUITY differential refractive index detector.

[0073] 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 and cleaning solution: isopropanol; Pre-column: PLgel 10 μm Mini MIX-B Guard (size: 50 mm × 4.6 mm × 2); Analytical phase: PLgel 10 μm Mini MIX-B (size: 250 mm × 4.6 mm); Standards: polystyrene sleeve; Run time: 30 min; Detector: ACQUITY differential refractive index (RI) detector; Column oven temperature: 90 °C; Detector temperature: 55 °C.

[0074] Sample testing: a. Preparation of standard and test samples: Weigh 0.002 g to 0.004 g of standard / test sample and add 2 mL of mobile phase liquid to prepare a 0.1% to 0.5% mixed standard solution, and place it in the refrigerator for >8 h; b. Standard solution / sample testing: Edit the sample group to be tested, select the established sample group method, and after the baseline stabilizes, click the run queue to start testing the samples;

[0075] Data processing: Based on the relationship between retention time and molecular weight, a calibration curve is established using a chemical workstation, and the sample spectrum is integrated and quantified. The chemical workstation automatically generates molecular weight and molecular weight distribution results.

[0076] In some embodiments of this application, the density of the polysilsesquioxane is 1 g / cm³. 3 -1.3g / cm 3 For example, the density of the polysilsesquioxane can be 1 g / cm³. 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 Therefore, the density of polysilsesquioxane is within the above range, which is relatively low. Using it in separators can reduce battery weight and increase energy density. In addition, while meeting heat resistance requirements, it can improve the air permeability of the separator, and the cycle performance of batteries using this separator will also be improved.

[0077] It is understandable that the "density of polysilsesquioxane" refers to the mass per unit "actual volume of solid material (excluding open and closed pores and interparticle pores)" in a dense state. It can be obtained through the following method:

[0078] The determination is carried out in accordance with the standard GB / T24586: a certain mass of sample is weighed and placed in a true density tester. The test system is sealed, and helium gas is introduced according to the procedure. The pressure of the gas in the sample chamber and the expansion chamber is detected, and the true volume is calculated according to Bohr's law (PV=nRT). The density is calculated based on this volume and mass. National standard: GB / T24586 Determination of apparent density, true density and porosity of iron ore.

[0079] In some embodiments of this application, the structural formula of the polysilsesquioxane includes:

[0080]

[0081] R1 and R2 each independently include an alkyl group with 1-12 carbon atoms, an unsaturated hydrocarbon group with 1-12 carbon atoms, or a phenyl group, n = 50-1000.

[0082] For example, R1 and R2 each independently include alkyl groups with 1-12 carbon atoms, alkyl groups with 2-11 carbon atoms, alkyl groups with 3-10 carbon atoms, alkyl groups with 4-9 carbon atoms, alkyl groups with 5-8 carbon atoms, alkyl groups with 6-7 carbon atoms, etc.; R1 and R2 each independently include unsaturated hydrocarbon groups with 1-12 carbon atoms, unsaturated hydrocarbon groups with 2-11 carbon atoms, unsaturated hydrocarbon groups with 3-10 carbon atoms, unsaturated hydrocarbon groups with 4-9 carbon atoms, unsaturated hydrocarbon groups with 5-8 carbon atoms, unsaturated hydrocarbon groups with 6-7 carbon atoms, etc. The polysilsesquioxane with the above-mentioned structure improves the heat resistance and stability of the separator, reduces the probability of short circuits between the positive and negative electrodes in the secondary battery, and improves the transport efficiency of active metal ions. In addition, it can reduce the probability of polysilsesquioxane clogging the micropores on the separator, thus improving the cycle performance of the secondary battery.

[0083] In some embodiments of this application, the polysilsesquioxane comprises at least one of the following structural formulas:

[0084]

[0085] Where Ph represents phenyl, and n = 50-1000.

[0086] 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 can be equal or unequal.

[0087] Therefore, the polysilsesquioxane with the above-mentioned structure improves the heat resistance and stability of the separator, reduces the probability of short circuits between the positive and negative electrodes in the secondary battery, improves the transport efficiency of active metal ions, and reduces the probability of polysilsesquioxane clogging the micropores on the separator, thus improving the cycle performance of the secondary battery.

[0088] In some embodiments of this application, the separator includes a base film and a coating located on at least one side of the base film, the coating including the polysilsesquioxane. Therefore, by incorporating polysilsesquioxane into the coating, the probability of polysilsesquioxane clogging the micropores of the base film can be reduced. Furthermore, the inclusion of polysilsesquioxane in the coating forms a heat-resistant coating. When the base film shrinks due to heat, the uniform polysilsesquioxane particles in the coating rapidly contact and compress, providing a force opposite to the shrinkage direction of the separator, thereby reducing the degree of shrinkage and enhancing the separator's resistance to deformation, thus reducing the probability of short circuits between the positive and negative electrodes in the secondary battery. The uniform spacing between the polysilsesquioxane particles makes the separator relatively flat, enhancing its permeability. Moreover, the channels and distances for the transport of active metal ions on the separator are similar, improving the transport efficiency of active metal ions and enhancing the cycle performance of the secondary battery.

[0089] In some embodiments of this application, the thickness of the coating is 0.3μm-3μm. For example, the coating thickness can be 0.3μm-2.9μm, 0.5μm-2.7μm, 0.7μm-2.5μm, 1μm-2.3μm, 1.3μm-2μm, or 1.5μm-2.8μm. Thus, with the coating thickness within the above range, when the base film shrinks due to heat, the uniform polysilsesquioxane particles in the coating rapidly contact and compress, providing a force opposite to the shrinkage direction of the separator, thereby reducing the degree of separator shrinkage, enhancing the separator's resistance to deformation, and reducing the probability of short circuits between the positive and negative electrodes in the secondary battery. The uniform spacing between the polysilsesquioxane particles makes the separator relatively flat, enhancing its permeability. Furthermore, the channels and distances for active metal ions to transport on the separator are similar, improving the transport efficiency of active metal ions and enhancing the cycle performance of the secondary battery. In other embodiments of this application, the thickness of the coating is 0.5 μm to 2 μm.

[0090] In some embodiments of this application, the coating further includes an adhesive, which 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 fluorinated acrylate resin. Therefore, by adding the above-mentioned adhesive, polysilsesquioxane can be firmly fixed onto the base film, reducing the probability of polysilsesquioxane detachment, decreasing the probability of short circuits between the positive and negative electrodes in the secondary battery, improving the transport efficiency of active metal ions, and enhancing the cycle performance of the secondary battery.

[0091] In some embodiments of this application, the mass ratio of the polysilsesquioxane to the binder is (5-25):1. For example, the mass ratio of 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, by controlling the mass ratio of polysilsesquioxane to the binder within the above range, the polysilsesquioxane can be firmly fixed to the base film, reducing the probability of polysilsesquioxane detachment, decreasing the probability of short circuits between the positive and negative electrodes in the secondary battery, improving the transport efficiency of active metal ions, and enhancing the cycle performance of the secondary battery. In other embodiments of this application, the mass ratio of the polysilsesquioxane to the binder is (8-20):1.

[0092] In some embodiments of this application, the thickness of the base film is 4μm-20μm. For example, the thickness of the base film can be 4μm-19μm, 5μm-18μm, 6μm-17μm, 7μm-16μm, 8μm-15μm, 9μm-14μm, 10μm-13μm, 11μm-12μm, etc. Thus, controlling the thickness of the base film within the above range improves the transport efficiency of active metal ions and enhances the cycle performance of the secondary battery. In other embodiments of this application, the thickness of the base film is 5μm-18μm.

[0093] In some embodiments of this application, the pore size of the base membrane is 0.02 μm-0.08 μm. For example, the pore size of the base membrane can be 0.02 μm-0.079 μm, 0.03 μm-0.07 μm, 0.04 μm-0.07 μm, 0.04 μm-0.06 μm, 0.04 μm-0.05 μm, etc. Controlling the pore size of the base membrane within the above range can reduce the probability of polysilsesquioxane clogging the micropores of the base membrane, improve the transport efficiency of active metal ions, and enhance the cycle performance of the secondary battery. In other embodiments of this application, the pore size of the base membrane is 0.03 μm-0.06 μm.

[0094] In some embodiments of this 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%. Controlling the porosity of the base membrane within these ranges reduces the probability of polysilsesquioxane clogging the micropores of the base membrane, improves the transport efficiency of active metal ions, and enhances the cycle performance of the secondary battery. In other embodiments of this application, the porosity of the base membrane is 35%-65%.

[0095] A second aspect of this application provides a method for preparing a separator membrane, comprising:

[0096] S10: Prepare a separator containing polysilsesquioxane, wherein the polysilsesquioxane has a D v 90 particles with a diameter of a μm, D v 10 Particle size is bμm, D v 50 Particle size is cμm, (ab) / c≤3.

[0097] Using the method of this application, polysilsesquioxane is added during the preparation of the separator, and the particle size distribution of 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 separator. When the separator shrinks due to heat, the uniform polysilsesquioxane particles come into rapid contact and are squeezed together, which can provide a force opposite to the shrinkage direction of the separator, thereby reducing the degree of shrinkage of the separator and enhancing its resistance to deformation, thus reducing the probability of short circuit between the positive and negative electrodes in the secondary battery. On the other hand, the polysilsesquioxane particles of this application are uniform in size and spacing, making the separator relatively flat, enhancing its permeability, and the channels and distances for the transport of active metal ions on the separator are similar, improving the transport efficiency of active metal ions and enhancing the cycle performance of the secondary battery.

[0098] Some embodiments in this application include:

[0099] S100: A coating is prepared on at least one side of the base film to obtain an isolation film, said coating comprising the polysilsesquioxane.

[0100] By incorporating polysilsesquioxane into the coating, the probability of polysilsesquioxane clogging the micropores of the base membrane can be reduced. The coating, including polysilsesquioxane, forms a heat-resistant coating. When the base membrane shrinks due to heat, the uniform polysilsesquioxane particles in the coating rapidly contact and compress, providing a force opposite to the shrinkage direction of the separator, thereby reducing the degree of separator shrinkage and enhancing its resistance to deformation. This reduces the probability of short circuits between the positive and negative electrodes in the secondary battery. The uniform spacing between the polysilsesquioxane particles makes the separator relatively flat, enhancing its permeability. Furthermore, the channels and distances for active metal ions to transport on the separator are similar, improving the transport efficiency of active metal ions and enhancing the cycle performance of the secondary battery.

[0101] In some embodiments of this application, the polysilsesquioxane is prepared by the following method:

[0102] S101: Hydrolyze organosiloxane monomers, add catalysts, and polycondense under heating conditions to obtain polysilsesquioxane.

[0103] Therefore, the polysilsesquioxane obtained through hydrolysis and condensation reactions has a uniform particle size distribution (i.e., small (ab) / c). When used in separators, it can enhance the separator's resistance to deformation and reduce the probability of short circuits between the positive and negative electrodes in secondary batteries. Furthermore, the uniform particle size and spacing of the polysilsesquioxane particles make the separator relatively flat. The channels and distances for the transport of active metal ions on the separator are similar, which improves the transport efficiency of active metal ions and enhances the cycle performance of secondary batteries.

[0104] In some embodiments of this application, the hydrolysis temperature of the organosiloxane monomer is 20℃-30℃. For example, the hydrolysis temperature can be 20℃-29℃, 21℃-28℃, 22℃-27℃, 23℃-26℃, 24℃-25℃, etc. Therefore, within the above-mentioned hydrolysis temperature range, the organosiloxane monomer is fully hydrolyzed, and the resulting polysilsesquioxane, when used in a separator membrane, can improve the cycle performance of the secondary battery.

[0105] In some embodiments of this application, the heating temperature is 30℃-100℃. For example, the heating temperature can be 30℃-99℃, 35℃-95℃, 40℃-90℃, 45℃-85℃, 50℃-80℃, 55℃-75℃, 60℃-70℃, etc. 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. In some embodiments of this application, the heating temperature is 40℃-80℃.

[0106] Specifically, organosiloxane monomers first hydrolyze to generate silanols, simultaneously releasing alcohols to form a mixed solution. The alcohols increase the solubility of the organosiloxane monomers in the solution. Then, under the action of a catalyst, the silanols begin to condense, forming Si-O-Si bonds between them, further building a network structure, at which point nucleation begins. Finally, these nuclei continuously absorb silanols from the solution and continue to grow until they become polysilsesquioxanes. The nucleation and nucleus growth processes are competitive, and the reaction temperature affects both processes. When nucleation dominates, more nuclei are generated, resulting in smaller final polysilsesquioxane particle sizes; when nucleus growth dominates, the final microspheres have larger particle sizes. Increasing the temperature intensifies the reaction, generating more nuclei and consuming more silanols in the initial stages, thus limiting nucleus growth in later stages and resulting in smaller final polysilsesquioxane particle sizes. By controlling the heating temperature within the range of 30℃-100℃, the (ab) / c ratio can be reduced, promoting uniform particle size of polysilsesquioxane and improving the cycle performance of secondary batteries.

[0107] In some embodiments of this application, the catalyst includes at least one selected from ammonia, triethylamine, sodium hydroxide, magnesium hydroxide, or ammonium hydroxide. Therefore, the above catalyst can continuously and efficiently catalyze the polycondensation of hydrolyzed organosiloxane monomers, yielding polysilsesquioxanes with uniform particle size distribution, thereby improving the cycle performance of secondary batteries.

[0108] In some embodiments of this application, the organosiloxane monomer comprises:

[0109]

[0110] R3 includes any one of methyl or ethyl, and R4 includes any one of methyl, ethyl, phenyl, vinyl, allyl, and dodecyl. Therefore, the above organosiloxane monomers can be hydrolyzed and polycondensed to obtain polysilsesquioxanes with uniform particle size distribution, which can improve the cycle performance of secondary batteries.

[0111] In some embodiments of this application, the organosiloxane monomer includes at least one selected from methyltrimethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, dodecyltrimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, phenyltriethoxysilane, dodecyltriethoxysilane, vinyltriethoxysilane, or allyltriethoxysilane. Therefore, the above-mentioned organosiloxane monomers can be hydrolyzed and polycondensed to obtain polysilsesquioxanes with uniform particle size distribution, which can improve the cycle performance of secondary batteries.

[0112] Specifically, taking R3 as methyl and R4 as methyl as an example, the hydrolysis and condensation reaction process of organosiloxane monomers is as follows:

[0113]

[0114] As the base membrane mentioned above, this application does not have any particular limitations. Any well-known porous structure base membrane with electrochemical and mechanical stability can be selected according to actual needs. For example, it may 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 film.

[0115] A third aspect of this application provides a battery comprising the separator described in the first aspect of this application or the separator prepared by the method described in the second aspect. Therefore, the battery exhibits excellent cycle life.

[0116] A battery is a device that can be recharged after being discharged, allowing its active materials to be reactivated and continue to be used.

[0117] It is understood that the battery proposed in this application can be a lithium-ion battery or a sodium-ion battery.

[0118] Typically, a battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During charging and discharging, active metal ions repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, serves as a barrier. The electrolyte, acting as a conductor for the active metal ions, lies between the positive and negative electrodes.

[0119] [Positive electrode plate]

[0120] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive active material layer includes a positive active material.

[0121] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0122] In some embodiments of this application, the positive electrode includes a positive current collector, which may be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, carbon electrodes, carbon, nickel, or titanium may be used. The composite current collector may include a polymer material substrate and a metal layer. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, 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.).

[0123] In some embodiments of this application, the positive electrode sheet may further include a positive electrode active material layer, which includes a positive electrode active material. The specific type of the positive electrode active material is not limited, and any active material known in the art that can be used for the positive electrode of a battery can be used. Those skilled in the art can select according to actual needs.

[0124] 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 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 oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, 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, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and their modified compounds. All of these materials are commercially available.

[0125] 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 layered transition metal oxides, polyanionic compounds, and Prussian blue analogues.

[0126] Examples of the aforementioned layered transition metal oxides include:

[0127] Na 1-x Cu h Fe k Mn l M 1 m O 2-y M 1 It 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;

[0128] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 It is at least one of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn and Ba, 0 <z≤0.1;

[0129] 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。

[0130] Examples of the above polyanionic compounds include, for example:

[0131] 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;

[0132] 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;

[0133] 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;

[0134] 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.

[0135] Examples of the above Prussian blue analogs include, for example:

[0136] A u M 6 v [M 7 (CN)6] w ·xH2O, where A is H + 、NH4 + 、an alkali metal cation, and an alkaline earth metal cation, 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 them, M 6 and M 7 Each is an independent cation of at least one transition metal element selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, and W.

[0137] During the charging and discharging process, Li or Na undergoes insertion / extraction and consumption, resulting in varying molar contents of Li or Na at different discharge states. In the examples of cathode materials in this application, the molar contents of Li or Na refer to the initial state of the material, i.e., the state before feeding. When the cathode material is applied to the battery system, the molar contents of Li or Na will change after charge-discharge cycles.

[0138] In the examples of cathode materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0139] The modified compounds for the above materials can be used to modify the materials by doping and / or by surface coating.

[0140] The positive electrode active material layer may also optionally include a binder, a conductive agent, and other optional additives.

[0141] As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, SuperP(SP), graphene, and carbon nanofibers.

[0142] 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).

[0143] [Positive electrode plate]

[0144] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector.

[0145] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0146] 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0147] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. 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 oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional 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.

[0148] In some embodiments, the negative electrode active material layer may 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).

[0149] In some embodiments, the negative electrode active material layer may 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.

[0150] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0151] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0152] Electrolyte

[0153] Electrolytes may include electrolyte salts and solvents.

[0154] 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(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0155] 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 dioxalate borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

[0156] As an example, the solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl 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), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0157] In some embodiments of this application, the electrolyte also includes additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance.

[0158] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. Figure 1 The example shown is a square-structured battery cell 5.

[0159] In some embodiments, the battery cell may include an outer packaging. This outer packaging is used to encapsulate the positive electrode, the negative electrode, and the electrolyte.

[0160] In some embodiments, the outer packaging may include a shell and a cover. The shell may include a base plate and side plates attached to the base plate, the base plate and side plates enclosing a receiving cavity. The shell has an opening communicating with the receiving cavity, and the cover can be placed over the opening to close the receiving cavity.

[0161] The positive electrode, negative electrode, and separator can be formed into an electrode assembly through a winding or stacking process. The electrode assembly is encapsulated within the receiving cavity. The number of electrode assemblies contained in a single battery cell can be one or more, and can be adjusted as needed.

[0162] In some implementations, the outer packaging of a battery cell may include a rigid shell, such as a rigid plastic shell, an aluminum shell, or a steel shell.

[0163] The outer packaging of a battery cell may also include a pouch, such as a bag-type pouch. The material of the pouch may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0164] In some implementations, individual battery cells can be assembled into battery modules, and the number of batteries contained in a battery module can be multiple, with the specific number adjustable according to the application and capacity of the battery module.

[0165] Figure 2 This is battery module 4, used as an example. (See reference...) Figure 2 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other way. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0166] The battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are housed. In some embodiments, the battery modules may also be assembled into a battery pack, the number of battery modules contained in the battery pack being adjustable according to the application and capacity of the battery pack.

[0167] Figure 3 and 4 This is battery pack 1 as an example. (See reference...) Figure 3 and 4The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0168] A fourth aspect of this application provides an electrical device that includes 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 and satellites, and energy storage systems.

[0169] Figure 5 This is an example of an electrical appliance. The electrical appliance includes pure electric vehicles, hybrid electric vehicles, or plug-in hybrid electric vehicles.

[0170] Another example of a power-consuming device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and may use batteries as their power source.

[0171] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0172] Example 1

[0173] [Preparation of the isolation membrane]

[0174] (1) Preparation of polysilsesquioxane

[0175] In a 5L flask equipped with a stirrer, thermometer, and reflux condenser, 3000g of deionized water and 2g of hydrochloric acid were added. Stirring was started and 315.5g of methyltrimethoxysilane was added. After hydrolysis at 25°C for 1 hour, 10g of triethylamine was added, and the reaction was continued to be heated for 12 hours to obtain a white viscous solution. The solution was washed with deionized water until neutral, then dried and ground to obtain polysilsesquioxane.

[0176] (2) Preparation of the separating membrane

[0177] A commercially available PE (polyethylene) polymer microporous film (from Zhuogao Electronic Technology Co., Ltd.) with a thickness of 7 μm and an average pore size of 0.08 μm 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 at a mass ratio of 10:1 and stirred until homogeneous to obtain a slurry. The slurry was coated onto the base film and dried in an oven. The coating density of the polysilsesquioxane and binder on the base film was 0.5 g / m². 2 Then, the film is wound up to obtain the release film. Specific implementation parameters are shown in Table 1.

[0178] [Preparation of Positive Electrode Sheet]

[0179] A positive electrode slurry was prepared by thoroughly mixing polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive agent carbon black, and N-methylpyrrolidone (NMP) at a mass ratio of 1.2:58.38:0.42:40. The positive electrode slurry was then subjected to a 200 g / m³ concentration. 2 The loading is uniformly coated on the positive current collector aluminum foil, and then dried, cold-pressed and cut to obtain the positive electrode sheet.

[0180] [Preparation of negative electrode sheet]

[0181] 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. The mixture was thoroughly stirred and mixed to prepare a negative electrode slurry (solid content 63%). This negative electrode slurry was then subjected to a concentration of 98 g / m³. 2 The loading amount is coated on the negative electrode current collector copper foil, and then dried, cold pressed and slit to obtain the negative electrode sheet.

[0182] Electrolyte preparation

[0183] 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. LiPF6 is then dissolved in the above mixed solvent to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0184] The positive electrode, separator, and negative electrode are stacked and wound in sequence to form a battery cell. The battery cell is placed in an outer packaging, and the electrolyte prepared above is added. After processes such as encapsulation, standing, formation, and aging, a battery is obtained.

[0185] Examples 2-37 are the same as Example 1 except for the parameters (see Table 1).

[0186] Example 38

[0187] [Preparation of the isolation membrane]

[0188] (1) Preparation of polysilsesquioxane

[0189] In a 5L flask equipped with a stirrer, thermometer, and reflux condenser, 3000g of deionized water and 2g of hydrochloric acid were added. Stirring was started and 315.5g of methyltrimethoxysilane was added. After hydrolysis at 25°C for 1 hour, 10g of triethylamine was added, and the reaction was continued to be heated for 12 hours to obtain a white viscous solution. The solution was washed with deionized water until neutral, then dried and ground to obtain polysilsesquioxane.

[0190] (2) Preparation of the separating membrane

[0191] The raw materials obtained in step (1), such as polysilsesquioxane and polyethylene, are pretreated according to the formula and then transported to the extrusion system. 2) Casting: The pretreated raw materials are melt-plasticized in the extrusion system and then extruded from the die to form a melt isolation film. The melt is cast to form a base film with a specific crystalline structure. 3) Heat treatment: The base film 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 films. The isolation film has a thickness of 8 μm, an average pore size of 0.08 μm, and a porosity of 50%.

[0192] The remaining preparation methods are the same as in Example 1.

[0193] Examples 39-46 are identical to Example 38 except for the parameters (see Table 1).

[0194] The parameters of the separators in Examples 1-46 and Comparative Examples 1-2 of this application are shown in Table 1. The separator in Comparative Example 1 is 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.).

[0195] Table 1

[0196]

[0197]

[0198]

[0199] In Table 1, " / " indicates that no addition is made.

[0200] The structural formulas of the polysilsesquioxanes used in each of the embodiments and comparative examples in Table 1 are shown in Table 2.

[0201] Table 2

[0202]

[0203]

[0204]

[0205]

[0206]

[0207] Performance testing:

[0208] 1. Particle size determination of polysilsesquioxane

[0209] Referring to standard GB / T 19077-2016, a laser particle size analyzer (e.g., Malvern Master Size 3000) was used to determine the D of polysilsesquioxane. v 90 particle size, D v 10 particle size, D v 50 particle size.

[0210] Figure 6 The particle size distribution diagram for Example 6 of this application shows that a = 0.93, b = 0.49, c = 0.68, and (ab) / c = 0.647. It can be seen that the polysilsesquioxane prepared in Example 6 of this application has a uniform particle size distribution and uniform particle size.

[0211] 2. Scanning electron microscopy was performed on the polysilsesquioxane prepared in Example 1 to obtain... Figure 7 As can be seen, the polysilsesquioxane prepared in Example 1 of this application has a uniform particle size distribution and uniform particle size.

[0212] 3. Determination of the weight-average molecular weight of polysilsesquioxanes

[0213] The instrument used is an ACQUITY APC ultra-high performance polymer chromatograph; the detector used is an ACQUITY differential refractive index detector.

[0214] 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 and cleaning solution: isopropanol; Pre-column: PLgel 10 μm Mini MIX-B Guard (size: 50 mm × 4.6 mm × 2); Analytical phase: PLgel 10 μm Mini MIX-B (size: 250 mm × 4.6 mm); Standards: polystyrene sleeve; Run time: 30 min; Detector: ACQUITY differential refractive index (RI) detector; Column oven temperature: 90 °C; Detector temperature: 55 °C.

[0215] Sample testing: a. Preparation of standard and test samples: Weigh 0.002 g to 0.004 g of standard / test sample and add 2 mL of mobile phase liquid to prepare a 0.1% to 0.5% mixed standard solution, and place it in the refrigerator for >8 h; b. Standard solution / sample testing: Edit the sample group to be tested, select the established sample group method, and after the baseline stabilizes, click the run queue to start testing the samples;

[0216] Data processing: Based on the relationship between retention time and molecular weight, a calibration curve is established using a chemical workstation, and the sample spectrum is integrated and quantified. The chemical workstation automatically generates molecular weight and molecular weight distribution results.

[0217] 4. Determination of density of polysilsesquioxane

[0218] A certain mass of sample is weighed and placed in a true density tester. The test system is sealed, and helium gas is introduced according to the procedure. The pressure of the gas in the sample chamber and the expansion chamber is detected, and the true volume is calculated according to Bohr's law (PV = nRT). The density is then calculated based on this volume and mass. National standard: GB / T24586 Determination of apparent density, true density and porosity of iron ore.

[0219] 5. Heat shrinkage rate test of the release film

[0220] Sample preparation: The above-prepared separator is punched into samples with a width of 50 mm and a length of 100 mm using a punching machine. Five parallel samples are placed on A4 paper, and then the A4 paper containing the samples is placed on corrugated paper with a thickness of 1 mm to 5 mm.

[0221] Sample testing: Set the temperature of the forced-air drying oven to 150℃. After the temperature reaches the set temperature and stabilizes for 30 minutes, place the A4 paper placed on the corrugated paper into the forced-air drying oven and start timing. After the set time is reached (1 hour in this embodiment), measure the length and width of the isolation film, and mark the values ​​as m and n respectively.

[0222] Calculation of heat shrinkage rate: Longitudinal (MD) heat shrinkage rate = [(100-m) / 100]×100%, Transverse (TD) heat shrinkage rate = [(50-n) / 50]×100%, take the average value of 5 parallel samples as the test result.

[0223] 6. Secondary battery capacity retention test (cycle performance)

[0224] At 25℃, the battery was charged to 3.6V at a constant current of 1 / 3C, then charged to 0.05C at a constant voltage of 3.6V. After resting for 5 minutes, it was discharged to 2.5V at 1 / 3C. The resulting capacity was recorded as the initial capacity C0. The above steps were repeated, and the discharge capacity C1000 of the secondary battery after 1000 cycles was recorded. The capacity retention rate of the secondary battery after 1000 cycles was P1000 = C1000 / C0 × 100%, as shown in Table 3.

[0225] Table 3

[0226]

[0227]

[0228] As shown in Table 3, in Examples 1-46 of this application, the addition of polysilsesquioxane to the separator and the control of the particle size distribution of polysilsesquioxane resulted in a smaller shrinkage rate of the separator and excellent battery cycle performance. Compared with Examples 1-46, Comparative Example 1 did not add polysilsesquioxane to the separator and used a polyethylene film, while Comparative Example 2 had a polysilsesquioxane particle size distribution not within the ≤3 range, resulting in a significantly increased thermal shrinkage rate of the separator and a significantly reduced battery cycle performance. Therefore, the separators used in the embodiments of this application exhibit good heat resistance and stability, and the battery has an excellent cycle life.

[0229] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A separating membrane, characterized in that, The separator membrane comprises polysilsesquioxane, the D of which is... v 90 particles with a diameter of a μm, D v 10 Particle size is bμm, D v 50 Particle size is cμm, (ab) / c≤3.

2. The separator membrane according to claim 1, characterized in that, 0.4≤(ab) / c≤1.

5.

3. The separator according to claim 1 or 2, characterized in that, a = 0.5-5, or alternatively, a = 0.6-2.

5.

4. The separator membrane according to any one of claims 1-3, characterized in that, b = 0.05-1.5, or alternatively, b = 0.1-1.

3.

5. The separator membrane according to any one of claims 1-4, characterized in that, c = 0.1-3, or optionally, c = 0.4-1.

7.

6. The separator membrane according to any one of claims 1-5, characterized in that, The weight-average molecular weight of the polysilsesquioxane is 10,000-100,000, and can be selected as 30,000-80,000.

7. The separator membrane according to any one of claims 1-6, characterized in that, The density of the polysilsesquioxane is 1 g / cm³. 3 -1.3g / cm 3 1g / cm 3 -1.2g / cm 3 .

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

9. The separator membrane according to any one of claims 1-8, characterized in that, The polysilsesquioxane comprises at least one of the following structural formulas: Where Ph represents phenyl, and n = 50-1000.

10. The separator membrane according to any one of claims 1-9, characterized in that, The isolation membrane includes a base membrane and a coating located on at least one side of the base membrane, the coating including the polysilsesquioxane.

11. The separator membrane according to claim 10, characterized in that, The thickness of the coating is 0.3μm-3μm, and can be selected as 0.5μm-2μm.

12. The separator according to claim 10 or 11, characterized in that, The coating further includes an adhesive, 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 fluorinated acrylate resin.

13. The separator membrane according to claim 12, characterized in that, The mass ratio of the polysilsesquioxane to the binder is (5-25):1, and can be optionally (8-20):

1.

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

15. A method for preparing a separating membrane, characterized in that, include: Prepare a separator containing polysilsesquioxane, wherein the polysilsesquioxane has a D... v 90 particles with a diameter of a μm, D v 10 Particle size is bμm, D v 50 Particle size is cμm, (ab) / c≤3.

16. The method according to claim 15, characterized in that, include: A coating is prepared on at least one side of the base film to obtain an isolation film, the coating comprising the polysilsesquioxane.

17. The method according to claim 15 or 16, characterized in that, 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, characterized in that, The temperature at which the organosiloxane monomer is hydrolyzed is 20℃-30℃.

19. The method according to claim 17 or 18, characterized in that, The heating temperature is 30℃-100℃, and can be selected as 40℃-80℃.

20. The method according to any one of claims 17-19, characterized in that, The catalyst includes at least one of ammonia, triethylamine, sodium hydroxide, magnesium hydroxide, or ammonium hydroxide.

21. The method according to any one of claims 17-20, characterized in that, The organosiloxane monomer includes: R3 includes any one of methyl or ethyl, and R4 includes any one of methyl, ethyl, phenyl, vinyl, allyl, and dodecyl.

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

23. A battery, characterized in that, The separator includes the separator according to any one of claims 1-14 or the separator prepared by any one of claims 15-22.

24. An electrical appliance, characterized in that, Includes the battery as described in claim 23.

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