Separator and preparation method therefor, battery and electrical apparatus

Abstract

A separator and a preparation method therefor, a battery and an electrical apparatus. The separator comprises a base film and a first coating, the first coating being arranged on one side of the base film, the first coating comprising dielectric material particles, and the relative dielectric constant of the dielectric material particles being 1000-10000. The separator comprises the first coating comprising the dielectric material particles having the described relative dielectric constant, thus improving the cycle performance of batteries containing same during quick charging.

Description

Isolation film and preparation method thereof, battery and electrical device

[0001] Priority information

[0002] This application claims priority and benefits of patent application 202410012603.7 filed with the State Intellectual Property Office of China on January 3, 2024, and the entire text of which is incorporated herein by reference. Technical Field

[0003] The present application belongs to the field of 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 widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As battery applications expand, the performance requirements for secondary batteries are becoming increasingly stringent, such as the requirement for fast charging capabilities. However, during fast charging, metal dendrites are easily formed on the surface of the negative electrode, resulting in reduced battery cycle performance.

[0005] Summary of the Invention

[0006] In view of the technical problems existing in the background technology, the present application provides an isolation membrane, aiming to improve the cycle performance of the battery containing the isolation membrane during the fast charging process.

[0007] In order to achieve the above-mentioned objectives, the first aspect of the present application provides an isolation membrane, which includes:

[0008] basement membrane;

[0009] A first coating layer is provided on one side of the base film, the first coating layer comprises dielectric material particles, and the relative dielectric constant of the dielectric material particles is 1000-10000.

[0010] The present application includes at least the following beneficial effects: the isolation film of the present application includes a first coating of dielectric material particles with the above-mentioned relative dielectric constant, which can improve the cycle performance of the battery containing it during the fast charging process.

[0011] In some embodiments, the relative dielectric constant of the dielectric material particles is 1500-5000. This can further improve the cycle performance of the battery during fast charging.

[0012] In some embodiments, the volume average particle size Dv50 of the dielectric material particles is 200 nm to 2000 nm, and optionally 500 nm to 1500 nm, thereby improving the cycle performance of the battery during fast charging.

[0013] In some embodiments, the dielectric material particles include at least one of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, or lithium barium lead niobate, thereby improving the cycling performance of the battery during fast charging.

[0014] In some embodiments, the dielectric material particles account for 20%-80% of the total mass of the first coating layer, and optionally 30%-70%, thereby improving the cycle performance of the battery during fast charging.

[0015] In some embodiments, the thickness of the first coating layer is 0.5 μm-2 μm, and optionally 0.8 μm-1.7 μm, thereby improving the cycle performance of the battery during fast charging.

[0016] In some embodiments, the BET specific surface area of ​​the dielectric material particles is 0.5 m 2 / g-6m 2 / g, optional 0.8m 2 / g-4m 2 / g. Thus, the cycle performance of the battery during the fast charging process can be improved.

[0017] In some embodiments, the first coating layer further includes a first binder, thereby improving the bonding performance between the first coating layer and the base film.

[0018] In some embodiments, the first binder includes at least one of polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorine-containing acrylate resin. This can improve the bonding performance between the first coating layer and the base film.

[0019] In some embodiments, the isolation film further includes a second coating layer, which is disposed on a side of the base film away from the first coating layer and includes inorganic particles, thereby improving the high temperature resistance of the isolation film.

[0020] In some embodiments, the inorganic particles include at least one of silica, alumina, zirconium dioxide, zinc oxide, magnesium oxide, sodium sulfate, barium sulfate, boehmite, or calcium carbonate, and may be selected from at least one of silica, alumina, boehmite, zirconium dioxide, or barium sulfate. This can improve the high-temperature resistance of the separator.

[0021] In some embodiments, the volume average particle size Dv50 of the inorganic particles is 0.5 μm-2.5 μm, and optionally 0.8 μm-2.3 μm, thereby improving the high temperature resistance of the isolation membrane.

[0022] In some embodiments, the thickness of the second coating layer is 0.5 μm-4 μm, and optionally 1 μm-2 μm, thereby improving the high temperature resistance of the isolation film.

[0023] In some embodiments, the inorganic particles account for 30% to 70% by mass, and optionally 40% to 60% by mass, of the total mass of the second coating layer, thereby improving the high temperature resistance of the isolation film.

[0024] In some embodiments, the second coating layer includes a second binder, thereby improving the bonding performance between the second coating layer and the base film.

[0025] In a second aspect of the present application, a method for preparing an isolation film is proposed, comprising: forming a first coating layer comprising dielectric material particles on one side of a base film to obtain an isolation film, wherein the relative dielectric constant of the dielectric material particles is 1000-10000.

[0026] Therefore, the battery using the isolation membrane obtained by this method has excellent cycle performance during the fast charging process.

[0027] In a third aspect of the present application, a battery is provided, comprising the separator described in the first aspect of the present application or the separator obtained by the method described in the second aspect of the present application. Thus, the battery has excellent cycle performance.

[0028] In the fourth aspect of the present application, the present application proposes an electrical device comprising the battery described in the third aspect of the present application.

[0029] 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

[0030] 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:

[0031] FIG1 is a schematic structural diagram of an isolation membrane according to an embodiment of the present application.

[0032] FIG2 is a schematic structural diagram of an isolation membrane according to another embodiment of the present application.

[0033] FIG3 is a schematic diagram of a battery according to an embodiment of the present application.

[0034] FIG. 4 is an exploded view of the battery shown in FIG. 3 according to an embodiment of the present application.

[0035] FIG5 is a schematic diagram of a battery module according to an embodiment of the present application.

[0036] FIG6 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0037] FIG. 7 is an exploded view of the battery pack shown in FIG. 6 according to an embodiment of the present application.

[0038] FIG8 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0039] Description of reference numerals:

[0040] 10 Isolation film; 100 Base film; 200 First coating layer; 300 Second coating layer; 1 Battery cell; 11 Housing; 12 Electrode assembly; 13 Cover plate; 2 Battery module; 3 Battery pack; 31 Upper case; 32 Lower case. DETAILED DESCRIPTION

[0041] 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.

[0042] 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.

[0043] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0045] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0047] Currently, judging by market developments, the application of secondary batteries is becoming increasingly widespread. They are not only used in energy storage 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, and electric vehicles, as well as in military equipment and aerospace, among other fields.

[0048] As the application scope of secondary batteries becomes wider and wider, the requirements for their performance are becoming increasingly stringent, such as the requirement for them to have fast charging capabilities. Currently, during the fast charging process of secondary batteries, the desolvation rate of solvated active ions and the diffusion rate in the active ion SEI membrane affect the fast charging performance of the battery. Especially during high-current charging, the difference in active ion concentration between the bulk and surface phases of the negative electrode active material will lead to an increase in the local active ion concentration. When the active ions break through the nucleation barrier on the surface of the negative electrode active material, metal dendrites will be generated. Due to the excellent conductivity of metals, active ions will preferentially gather near the dendrites and be reduced to form metal dendrites. These metal lithium deposits may bypass the isolation membrane to form a micro-short circuit with the positive electrode, causing problems such as battery storage, self-discharge, leakage current, and even piercing the isolation membrane, leading to serious problems such as short circuit.

[0049] The isolation membrane disclosed in the embodiments of the present application is applicable to lithium-ion batteries and sodium-ion batteries, and the battery 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, electric tools, battery-powered vehicles, 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.

[0050] In the first aspect of the present application, an isolation film is proposed. Referring to Figure 1, the isolation film 10 includes a base film 100 and a first coating 200. The first coating 200 is arranged on one side of the base film 100. The first coating 200 includes dielectric material particles, and the relative dielectric constant of the dielectric material particles is 1000-10000.

[0051] In this application, "dielectric material particles" refer to materials that exhibit excellent insulating properties in an electric field, which can separate charges and store electrical energy without losing charge.

[0052] The isolation film 10 of the present application includes a first coating layer 200 of dielectric material particles with the above-mentioned relative dielectric constant, which can improve the cycle performance of the battery containing the isolation film 10 during the fast charging process.

[0053] The process by which the above-mentioned dielectric material particles exert their performance is speculated as follows: the isolation membrane 10 of the present application includes a first coating 200 of dielectric material particles with the above-mentioned relative dielectric constant. During the charging process of the battery containing the isolation membrane 10, the dielectric material particles are under the action of the electric field, and the positive and negative charge centers in the material will be separated, generating a reverse electric field inside. The reverse electric field generated by the dielectric material particles makes the surface of the negative electrode plate in contact with the first coating 200 of the isolation membrane 10 negatively charged, and thus may attract the active ions gathered on the surface of the negative electrode plate to be evenly distributed, thereby reducing the risk of active ions gathering on the surface of the negative electrode plate to generate metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process.

[0054] In some embodiments of the present application, the relative dielectric constant of the dielectric material particles is 1000-10000, for example, 1000-9500, 1500-9000, 2000-8500, 2500-8000, 3000-7500, 3500-7000, 4000-6500, 4500-6000, 5000-5500, etc. In other embodiments of the present application, the relative dielectric constant of the first dielectric material particles is 1500-5000.

[0055] In the present application, the relative dielectric constant of dielectric material particles refers to the relative dielectric constant at room temperature (25±5° C.), which has a well-known meaning in the art and can be tested using instruments and methods known in the art. For example, the first coating 200 of the isolation membrane 10 can be scraped to powder, and the obtained powder is heated to 1000°C in an oxygen-containing atmosphere and kept warm for 1 hour for sintering, and water is added for filtration and separation to obtain dielectric material particles, and then the dielectric material particles are prepared into circular samples (the sample preparation process includes: adding 40g of adhesive (the adhesive is compounded by acrylic acid (PAA) emulsion and alcohol amine plasticizer, and its decomposition temperature is less than 300°C) to 200g of the dielectric material particles to be tested, and after fully stirring, slowly adding it to an automatic roller press (the roller press is a double-roll roller press, the rollers are made of stainless steel and the surface is polished; the gap between the two rollers is adjustable in the range of 0.5mm to 2mm), and rolling it into a raw porcelain cake with a thickness of 1mm±0.15mm, and it is qualified if there is no color difference on the surface, uniform cross-section, and no obvious stratification; then the raw porcelain cake is placed on a sheet punching machine (the pressing plate of the sheet punching machine is circular and the size is Under the pressure plate (made of stainless steel with a polished surface), 10 thin circular ceramic pieces with a diameter of 11±1 mm are punched out; (2) debinding: the thin circular ceramic piece obtained in step (1) is placed on a clean and flat zirconia or alumina support plate, and placed in a muffle furnace together with the support plate, and debinding is performed by heating the ceramic piece to 300°C at a heating rate of 0.3°C / min and then keeping the temperature for 6 hours; after the front debinding is completed, the thin circular ceramic piece is taken out and replaced with the back side facing up, and the above operation is repeated for the back debinding; (3) silver coating: the thin circular ceramic piece after debinding in step (2) is placed on a clean and flat zirconia or alumina support plate, and the silver paste is evenly applied to the front of the thin circular ceramic piece using a fine brush, The silver paste is a high-temperature sintering conductive silver paste. The silver paste is applied in a one-way manner for 2-3 times, with a thickness of 80μm to 100μm. (4) Silver burning: first, the silver layer on the side of the thin circular porcelain piece after silver coating in step (3) is gently scraped off with a blade, and then the thin circular porcelain piece after silver coating is placed in a muffle furnace together with a firing plate. Silver burning is performed at a heating rate of 5℃ / min and after heating to 800℃ and keeping warm for 2h. After the front side silver burning is completed, the thin circular porcelain piece and the firing plate are taken out, and steps (3) and (4) are repeated to silver burn the back side. After that, the capacitance C is tested by an LCR meter and calculated according to the formula: relative dielectric constant ε=(C×d) / (ε0×A). C represents capacitance, in farads (F); d represents sample thickness, in cm; A represents sample area, in cm 2 ;ε0 represents the dielectric constant of vacuum, ε0=8.854×10 -14 F / cm. In this application, the test conditions may be 1 kHz, 1.0 V, and 25 ± 5°C. The test standard may be in accordance with GB / T 11297.11-2015.

[0056] In some embodiments of the present application, the volume average particle size Dv50 of the dielectric material particles is 200 nm-2000 nm, for example, 300 nm-1900 nm, 400 nm-1800 nm, 500 nm-1700 nm, 600 nm-1600 nm, 700 nm-1500 nm, 800 nm-1400 nm, 900 nm-1300 nm, 1000 nm-1200 nm, 1000 nm-1100 nm, etc. Thus, the cycle performance of the battery during the fast charging process can be further improved.

[0057] The process by which the dielectric material particles of the above-mentioned particle size exert their performance is speculated as follows: The dielectric material particles of the particle size of the present application can, on the one hand, exert their excellent reverse electric field effect, and thus may attract the active ions gathered on the surface of the negative electrode to be evenly distributed, thereby reducing the risk of active ions gathering on the surface of the negative electrode to produce metal dendrites, thereby further improving the cycle performance of the battery containing it during the fast charging process. On the other hand, the use of dielectric material particles of this particle size in the first coating 200 can avoid the dielectric material particles blocking the pores of the base film 100 and reducing the transmission of active ions. In other embodiments of the present application, the volume average particle size Dv50 of the dielectric material particles is 500nm-1500nm.

[0058] In this application, the volume average particle size Dv50 of the dielectric material particles refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50%. The test method for the volume average particle size Dv50 of the dielectric material particles in the isolation film is as follows:

[0059] (1) The separator 10 is heated to 1000° C. in an oxygen-containing atmosphere and kept at this temperature for 1 hour for sintering, and then water is added and filtered;

[0060] (2) Referring to the standard GB / T 19077-2016, a laser particle size analyzer (e.g., Malvern Master Size 3000) is used to measure the volume average particle size Dv50 of the filtered substance, i.e., the dielectric material particles.

[0061] In some embodiments of the present application, the dielectric material particles include at least one of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, or lithium lead barium niobate. Thus, such dielectric material particles can further improve the cycling performance of batteries containing them during fast charging.

[0062] The process by which the dielectric material particles of the above composition exert their performance is speculated as follows: the dielectric material particles of the above composition can exert excellent reverse electric field effects. The reverse electric field generated by the dielectric material particles makes the surface of the negative electrode plate in contact with the first coating 200 of the isolation membrane 10 negatively charged, and thus may attract the active ions gathered on the surface of the negative electrode plate to be evenly distributed, thereby reducing the risk of active ions gathering on the surface of the negative electrode plate and generating metal dendrites, thereby further improving the cycle performance of the battery containing it during the fast charging process.

[0063] The present application has no particular limitation on the type of the base film 100 , and any known porous structure base film with good chemical stability and mechanical stability can be selected.

[0064] In some embodiments, the base film 100 may be made of at least one of fiberglass, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The base film 100 may be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0065] In some embodiments of the present application, the mass proportion of the dielectric material particles is 20%-80% based on the total mass of the first coating layer 200, for example, 25%-75%, 30%-70%, 35%-65%, 40%-60%, 45%-55%, 50%-55%, etc. Thus, adding the above-mentioned amount of dielectric material particles to the first coating layer 200 can further improve the cycling performance of the battery containing the dielectric material particles during the fast charging process.

[0066] The process by which the dielectric material particles of the above content exert their performance is speculated as follows: by adding the dielectric material particles of the above content to the first coating 200, an excellent counter-electric field effect can be exerted. The counter-electric field generated by the dielectric material particles makes the surface of the negative electrode plate in contact with the first coating 200 of the isolation membrane 10 appear negatively charged, thereby possibly attracting the active ions gathered on the surface of the negative electrode plate to be evenly distributed, thereby reducing the risk of active ions gathering on the surface of the negative electrode plate and generating metal dendrites, thereby further improving the cycle performance of the battery containing it during the fast charging process. In other embodiments of the present application, based on the total mass of the first coating 200, the mass of the dielectric material particles accounts for 30%-70%.

[0067] In the present application, the method for testing the mass proportion of dielectric material particles in the first coating 200 in the isolation film 10 includes: scraping powder on the first coating 200 in the isolation film 10, and subjecting the sample to a thermal gravimetric test. The test conditions are: oxygen atmosphere, heating from 25°C to 500°C, and a heating rate of 5° / min. The corresponding ordinate on the thermal gravimetric curve corresponding to 500°C (thermal gravimetric (TG) curve, whose ordinate is weight percentage and the abscissa is temperature) is the mass proportion of dielectric material particles.

[0068] In some embodiments of the present application, the thickness of the first coating 200 is 0.5μm-2μm, for example, 0.6μm-1.9μm, 0.7μm-1.8μm, 0.8μm-1.7μm, 0.9μm-1.6μm, 1μm-1.5μm, 1.1μm-1.4μm, 1.2μm-1.3μm. In other embodiments of the present application, the thickness of the first coating 200 is 0.8μm-1.7μm. Thus, providing a first coating 200 having this thickness on one side of the base film 100 can further improve the cycle performance of the battery containing it during the fast charging process.

[0069] In this application, the thickness test method of the first coating 200 includes: first, cutting the isolation film 10 to be tested into a 6mm×6mm test sample, clamping the test sample with two pieces of conductive and thermally conductive copper foil, and fixing the test sample and the copper foil with double-sided tape, pressing with a 400g flat iron block for 1 hour to make the gap between the test sample and the copper foil as small as possible, then trimming the edges with scissors and sticking them on a sample table with conductive glue, with the sample slightly protruding from the edge of the sample table. Then put the sample table into the sample holder, lock it, turn on the power of the IB-19500CP argon ion cross-section polisher and evacuate to 10Pa -4 Pa, set the argon flow rate to 0.15 MPa and the voltage to 8 kV, and the polishing time to 2 hours, adjust the sample stage to the swing mode and start polishing. After polishing, use a ZEISS Sigma300 scanning electron microscope to obtain the ion polishing cross-sectional morphology (CP) image of the sample to be tested, and the thickness of the first coating 200 can be obtained.

[0070] In some embodiments of the present application, the BET specific surface area of ​​the dielectric material particles is 0.5 m 2 / g-6m 2 / g, for example 1m 2 / g-5.5m 2 / g,1.5m 2 / g-5m 2 / g,2m 2 / g-4.5m 2 / g,2.5m 2 / g-4m 2 / g,3m 2 / g-3.5m 2 Therefore, the use of dielectric material particles with such a specific surface area in the first coating 200 can further improve the cycle performance of the battery containing the dielectric material particles during the fast charging process.

[0071] The process of the dielectric material particles of the above specific surface area exerting their performance is speculated as follows: the dielectric material particles of the above specific surface area range can exert excellent reverse electric field effects. The reverse electric field generated by the dielectric material particles makes the surface of the negative electrode sheet in contact with the first coating 200 of the isolation membrane 10 negatively charged, thereby attracting the active ions gathered on the surface of the negative electrode sheet to be evenly distributed, thereby reducing the risk of active ions gathering on the surface of the negative electrode sheet to produce metal dendrites, thereby further improving the cycle performance of the battery containing it during the fast charging process. In other embodiments of the present application, the BET specific surface area of ​​the dielectric material particles is 0.8m 2 / g-4m 2 / g.

[0072] In this application, the BET specific surface area of ​​the dielectric material particles is a well-known meaning in the art and can be tested using instruments and methods well-known in the art. For example, the isolation film 10 is first cut into an area of ​​5cm*5cm, and then the sample is heated to 1000°C in an oxygen-containing atmosphere and kept warm for 1h for sintering, and then water is added for filtration and separation to obtain dielectric material particles. Then, referring to GB / T19587-2017, the filtered sample is tested using the nitrogen adsorption specific surface area analysis test method, and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis test can be performed using the Tri-Star 3020 specific surface area pore size analyzer from Micromeritics, USA.

[0073] In some embodiments of the present application, the first coating layer 200 further includes a first binder. For example, the first binder includes at least one of polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorine-containing acrylate resin. This improves the adhesion between the first coating layer 200 and the base film 100, prevents the separator 10 from shedding powder during use, and improves battery cycle performance.

[0074] In some embodiments of the present application, referring to FIG2 , the isolation film 10 further includes a second coating layer 300. The second coating layer 300 is disposed on a side of the base film 100 away from the first coating layer 200. The second coating layer 200 includes inorganic particles. Thus, by disposing the second coating layer 300 including inorganic particles on a side of the base film 100 away from the first coating layer 200 including dielectric material particles, the high-temperature resistance of the isolation film 10 can be significantly improved.

[0075] As an example, the inorganic particles include at least one of silica, alumina, zirconium dioxide, zinc oxide, magnesium oxide, sodium sulfate, barium sulfate, boehmite or calcium carbonate, and can be selected from at least one of silica, alumina, boehmite, zirconium dioxide or barium sulfate.

[0076] In some embodiments of the present application, the volume average particle size Dv50 of the inorganic particles is 0.5 μm to 2.5 μm, for example, 0.8 μm to 2.3 μm, 1 μm to 2.1 μm, 1.2 μm to 2 μm, 1.5 μm to 1.8 μm, or 1.6 μm to 1.7 μm. Thus, by adding inorganic particles of the above-mentioned particle size to the second coating 300, not only can the high-temperature resistance of the isolation membrane 10 be improved, but also pore blockage in the base film 100 can be avoided, which can reduce active ion transmission. In other embodiments of the present application, the volume average particle size Dv50 of the inorganic particles is 0.8 μm to 2.3 μm.

[0077] In this application, the volume average particle size Dv50 of the inorganic particles refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50%. The test method for the volume average particle size Dv50 of the inorganic particles in the isolation film is as follows:

[0078] (1) After the second coating layer of the isolation membrane is powdered, the temperature is raised to 350°C in an oxygen-containing atmosphere and kept at this temperature for 1 hour for sintering, and then water is added and filtered;

[0079] (2) Referring to the standard GB / T 19077-2016, a laser particle size analyzer (e.g., Malvern Master Size 3000) is used to measure the volume average particle size Dv50 of the filtered material, i.e., the inorganic particles.

[0080] In some embodiments of the present application, the thickness of the second coating layer 300 is 0.5 μm-4 μm, for example, 0.6 μm-3.9 μm, 0.7 μm-3.6 μm, 0.8 μm-3.5 μm, 0.9 μm-3.2 μm, 1 μm-3 μm, 1.2 μm-2.8 μm, 1.5 μm-2.5 μm, 1.8 μm-2.2 μm, 1.8 μm-2 μm, etc. Thus, by providing the second coating layer 300 of this thickness on one side of the base film 100, the high temperature resistance of the isolation film 10 can be significantly improved. In other embodiments of the present application, the thickness of the second coating layer 300 is 1 μm-2 μm.

[0081] In this application, the thickness test method of the second coating 300 includes: first, cutting the isolation film to be tested into a 6mm×6mm test sample, clamping the test sample with two pieces of conductive and thermally conductive copper foil, and fixing the test sample and the copper foil with double-sided tape, pressing with a 400g flat iron block for 1 hour to make the gap between the test sample and the copper foil as small as possible, then trimming the edges with scissors and sticking them on the sample table with conductive glue, with the sample slightly protruding from the edge of the sample table. Then put the sample table into the sample holder, lock it, turn on the power of the IB-19500CP argon ion cross-section polisher and evacuate to 10Pa -4Pa, set the argon flow rate to 0.15 MPa and the voltage to 8 kV, and the polishing time to 2 hours, adjust the sample stage to the swing mode and start polishing. After polishing, use a ZEISS Sigma300 scanning electron microscope to obtain the ion polishing cross-sectional morphology (CP) image of the sample to be tested, and the thickness of the second coating 300 can be obtained.

[0082] In some embodiments of the present application, the inorganic particles comprise 30% to 70% by weight of the second coating layer 300, for example, 35% to 65%, 40% to 60%, 45% to 55%, 50% to 55%, etc. Thus, by controlling the inorganic particles in the second coating layer 300 within the above range, the high-temperature resistance of the separator 10 can be significantly improved. In other embodiments of the present application, the inorganic particles comprise 40% to 60% by weight of the second coating layer 300.

[0083] In the present application, the method for testing the mass proportion of inorganic particles in the second coating 200 in the isolation membrane 10 includes: scraping powder on the second coating 300 in the isolation membrane 10, and subjecting the sample to a thermal gravimetric test. The test conditions are: oxygen atmosphere, heating from 25°C to 350°C, and a heating rate of 5° / min. The corresponding vertical coordinate on the thermal gravimetric curve corresponding to 350°C (thermal gravimetric (TG) curve, whose vertical coordinate is weight percentage and the horizontal coordinate is temperature) is the mass proportion of the inorganic particles.

[0084] In some embodiments of the present application, the second coating layer 300 further includes a second binder. For example, the second binder includes at least one of polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorine-containing acrylate resin. This improves the adhesion between the second coating layer 300 and the base film 100, prevents the separator 10 from shedding during use, and improves battery cycle performance.

[0085] In the second aspect of the present application, a method for preparing an isolation film is proposed, comprising: forming a first coating layer comprising dielectric material particles on one side of a base film to obtain an isolation film, wherein the relative dielectric constant of the dielectric material particles is 1000-10000.

[0086] Therefore, the present application can improve the cycle performance of the battery containing the dielectric material during the fast charging process by forming a first coating layer including dielectric material particles with the above-mentioned relative dielectric constant on one side of the base film.

[0087] The process by which the above-mentioned dielectric material particles exert their performance is speculated as follows: the isolation membrane of the present application includes a first coating layer of dielectric material particles with the above-mentioned relative dielectric constant. During the charging process of the battery containing the isolation membrane, the dielectric material particles are under the action of the electric field, and the positive and negative charge centers in the material will be separated, generating a reverse electric field inside. The reverse electric field generated by the dielectric material particles makes the surface of the negative electrode plate in contact with the first coating layer of the isolation membrane negatively charged, and thus may attract the active ions gathered on the surface of the negative electrode plate to be evenly distributed, thereby reducing the risk of active ions gathering on the surface of the negative electrode plate to generate metal dendrites, thereby improving the cycle performance of the battery containing it during the fast charging process.

[0088] In some embodiments of the present application, the following steps may be employed: dielectric material particles are mixed with a first binder and a solvent such as deionized water to prepare a first slurry, the first slurry is then coated on one side of a base film, and dried to obtain an isolation film having a first coating.

[0089] In some further embodiments of the present application, the following steps may be employed: dielectric material particles are mixed with a first binder and a solvent, such as deionized water, to prepare a first slurry, the first slurry is then coated on one side of a base film, and after drying, a first coating layer comprising dielectric material particles is formed on one side of the base film, the isolation film is then flipped over, and a second slurry comprising inorganic particles, a second binder, and deionized water solvent is coated on the side of the base film away from the first coating layer, and after drying, a second coating layer comprising inorganic particles is formed on the other side of the base film.

[0090] In a third aspect of the present application, the present application proposes a battery, which includes the isolation membrane described in the first aspect of the present application or the isolation membrane obtained by the method described in the second aspect of the present application.

[0091] A battery is a battery that can be recharged to activate the active materials after discharge and continue to be used.

[0092] 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 process, active ions are embedded in and released from the positive and negative electrodes. The separator is placed between the positive and negative electrodes (when the positive electrode sheet, separator, and negative electrode sheet are stacked, the first coating on the separator contacts the negative electrode sheet) to provide isolation. The electrolyte conducts ions between the positive and negative electrodes.

[0093] 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.

[0094] 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.

[0095] In some embodiments of the present application, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may 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 (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0096] In some embodiments of the present application, the positive electrode active material may be a positive electrode active material for batteries known in the art.

[0097] As an example, when the positive electrode plate is used in a lithium-ion battery, the positive electrode active material may adopt a positive electrode active material for lithium-ion batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.80 Co 0.15 Al 0.05 O2) or at least one of its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, or a composite material of lithium iron manganese phosphate and carbon.

[0098] For example, when the positive electrode plate is used in a sodium ion battery, the positive electrode active material may be a positive electrode active material known in the art for use in sodium ion batteries. For 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, or a Prussian blue analog.

[0099] Examples of the layered transition metal oxides include:

[0100] Na 1-x Cu h Fe k Mn l M 1 m O 2-y , where M 1 Including at least one of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn or 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;

[0101] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 including at least one of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn or Ba, 0 <z≤0.1;

[0102] 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。

[0103] Examples of the above polyanion compounds include, for example:

[0104] A 1 f M 3 g (PO4) i O j X 1 3-j , where A 1 includes at least one of H, Li, Na, K, or NH4, M 3 includes at least one of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, or Zn, X 1 is at least one of F, Cl, or Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2;

[0105] Na n [[ID=२८]]M 4 PO4X 2 , where M 4 includes at least one of Mn, Fe, Co, Ni, Cu, or Zn, X 2 is at least one of F, Cl, or Br, 0 < n ≤ 2;

[0106] Na p M 5 q (SO4)3, where M 5 includes at least one of Mn, Fe, Co, Ni, Cu, or Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0107] Na s Mn t Fe 3-t [[ID=५५]](PO4)2(P2O7), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2, or 3.

[0108] Examples of the above Prussian blue analogs include, for example:

[0109] A u M 6 <00०००९०>[M[[ID=६७]]<0000०९१>(CN)6][[ID=६९]] w ·xH2O, where A includes H + 、NH4 + 、alkali metal cation or alkaline earth metal cation, M 6 and M ८००००९६>each independently includes at least one of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A includes H+ 、Li + 、Na + , K + NH4 + , Rb + 、Cs + 、Fr + 、Be 2+ Mg 2+ , Ca 2+ 、Sr 2+ 、Ba 2+ or Ra 2+ At least one of M 6 and M 7 Each independently includes at least a cation of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, or W.

[0110] 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 positive electrode active materials listed in this application refers to the material's initial state, i.e., the state before the materials are added. When the positive electrode active materials are used in a battery system, the molar content of Li or Na will change after charge and discharge cycles.

[0111] In the list of positive electrode active materials in this application, the molar content of oxygen is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of oxygen will fluctuate.

[0112] In some embodiments of the present application, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorine-containing acrylate resin.

[0113] In some embodiments of the present application, based on the total mass of the active material layer, the mass proportion of the binder is 0.5%-3%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0114] In some embodiments of the present application, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0115] In some embodiments of the present application, based on the total mass of the active material layer, the mass proportion of the conductive agent is 0.8%-4%, for example, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0116] In some embodiments of the present application, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0117] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0118] 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.

[0119] In some embodiments of the present application, 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.).

[0120] In some embodiments of the present application, 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, and titanates. The silicon-based material may include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, or silicon alloys. The tin-based material may include at least one of elemental tin, tin oxides, or tin alloys. When the battery is a lithium-ion battery, lithium titanate is used as the titanate; when the battery is a sodium-ion battery, sodium titanate is used as the titanate. 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.

[0121] In some embodiments of the present application, the negative electrode active material layer may further optionally include a binder. The binder may include 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), or carboxymethyl chitosan (CMCS).

[0122] In some embodiments of the present application, the negative electrode active material layer may further include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0123] In some embodiments of the present application, the negative electrode active material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0124] In some embodiments of the present application, 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 collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0125] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0126] The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or solid.

[0127] In some embodiments of the present application, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0128] In some embodiments of the present application, when the battery is a lithium ion battery, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, or lithium tetrafluorooxalatophosphate.

[0129] In some embodiments of the present application, when the battery is a sodium ion battery, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate or sodium bis(trifluoromethylsulfonyl)imide.

[0130] In some embodiments of the present application, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone or diethyl sulfone.

[0131] In some embodiments of the present application, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0132] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0133] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0134] The present application has no particular limitation on the shape of the battery, which can be cylindrical, square, or any other shape. For example, FIG3 shows a square-structured battery cell 1 as an example.

[0135] In some embodiments, referring to Figure 4, the outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0136] In some embodiments, batteries may be assembled into a battery module. The number of batteries contained in the battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0137] Figure 5 shows an example battery module 2. Referring to Figure 5 , within the battery module 2, multiple battery cells 1 may be arranged sequentially along the length of the battery module 2. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 1 may be secured together using fasteners.

[0138] Optionally, the battery module 2 may further include a housing having an accommodation space, and the plurality of battery cells 1 are accommodated in the accommodation space.

[0139] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0140] Figures 6 and 7 illustrate an example battery pack 3. Referring to Figures 6 and 7 , the battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box comprises an upper case 31 and a lower case 32. The upper case 31 can be positioned over the lower case 32 to form an enclosed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0141] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0142] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0143] Figure 8 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0144] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0145] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0146] Example 1

[0147] 1. Preparation of positive electrode sheet

[0148] The positive electrode active material is lithium nickel cobalt manganese oxide (NCM523, namely LiNi 0.5 Co 0.2 Mn 0.3 O2), binder polyvinylidene fluoride PVDF, conductive agent acetylene black according to the weight ratio of 98:1:1, add N-methylpyrrolidone (NMP) as solvent, stir the slurry in vacuum until it is uniform, and obtain positive electrode slurry. Then, the obtained positive electrode slurry is heated at 14 mg / cm 2 The surface density of the film was coated on both sides of the 13μm aluminum foil with a doctor blade, and then dried at 140℃, cold pressed, and cut to obtain the positive electrode sheet.

[0149] 2. Preparation of negative electrode sheet

[0150] The negative electrode active material artificial graphite, conductive agent acetylene black, composite binder SBR (styrene butadiene rubber), and dispersant sodium carboxymethyl cellulose (CMC-Na) were dissolved in deionized water at a weight ratio of 97:1:1:1, stirred and mixed to prepare a negative electrode slurry, and the negative electrode slurry was heated at 15.4 mg / cm 2 The surface density of the film is coated on both sides of the 5μm copper foil with a doctor blade. After drying, cold pressing and slitting, the negative electrode sheet is obtained.

[0151] 3. Preparation of electrolyte

[0152] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:7 to obtain an organic solvent, LiPF6 was dissolved in the above solvent, and stirred evenly to obtain an electrolyte with a concentration of 1 mol / L.

[0153] 4. Isolation film

[0154] The dielectric material particles of barium titanate are mixed with the adhesive polyvinylidene fluoride and deionized water to obtain a first slurry, which is coated on one side of the PE base film and then dried to remove moisture to obtain an isolation membrane (one side of the isolation membrane has a first coating layer including dielectric material particles, and the thickness of the first coating layer is 1.5 μm).

[0155] 5. Preparation of secondary batteries

[0156] The positive electrode sheet, separator, and negative electrode sheet are stacked in order (the first coating of dielectric material particles on the separator is adjacent to the negative electrode sheet), with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound to form a bare cell. The bare cell is then placed in an outer packaging, injected with the aforementioned electrolyte, and packaged to form a lithium-ion battery.

[0157] The preparation methods of the lithium-ion batteries of Examples 2-13 and Comparative Examples 1-2 are the same as those of Example 1, except that the process of preparing the isolation membrane is different, as shown in Table 1.

[0158] Table 1

[0159] The preparation method of the lithium-ion batteries of Examples 14-21 and Comparative Example 3 is the same as that of Example 1, except that the process of preparing the isolation membrane is different, specifically comprising: mixing dielectric material particles barium titanate with an adhesive polyvinylidene fluoride and deionized water to obtain a first slurry, mixing boehmite with an adhesive polyvinylidene fluoride and deionized water to obtain a second slurry, and then coating the second slurry on one side of the PE base film, drying (forming a first coating layer including a dielectric material on one side of the isolation membrane, and the first coating layer has a thickness of 1.5 μm), coating the second slurry on the other side of the PE base film, and then drying (forming a second coating layer including inorganic particles on the other side of the isolation membrane, and the second coating layer has a thickness of 1.5 μm), and cutting to obtain the isolation membrane, as shown in Table 2.

[0160] Table 2

[0161] The lithium deposition and cycle performance of the batteries of Examples 1-13 and Comparative Examples 1-3 were characterized, and the characterization results are shown in Table 3. The lithium deposition and cycle performance of the batteries of Examples 14-21 and the high temperature resistance of the isolation membrane were characterized, and the characterization results are shown in Table 5.

[0162] (1) Test of lithium deposition on negative electrode:

[0163] The battery was charged to 4.4V at 4C conditions, allowed to stand for 5 minutes, and then discharged to 2.8V at 1C conditions and allowed to stand for 5 minutes. The above charge and discharge process was cycled for 500 cycles, and then the negative electrode was disassembled. The surface of the disassembled negative electrode was scanned under vacuum conditions using backscattered electron diffraction (EBSD) technology (the scanning angle of the scanning electron microscope (SEM) used was 70 degrees), and the lithium deposition area signal and the non-lithium deposition area signal were collected respectively. The lithium deposition area ratio = the intensity of the lithium deposition area signal / (the intensity of the lithium deposition area signal + the signal intensity of the non-lithium deposition area).

[0164] (2) Cyclic performance test:

[0165] At 25°C, the battery was charged at a constant current rate of 2C to a cut-off voltage of 4V, and then discharged at a rate of 1C to a cut-off voltage of 2.8V. The initial capacity was recorded as C0. Then, the battery was charged according to the strategy shown in Table 4 and discharged at a rate of 1C. The discharge capacity of each cycle was recorded as C0. n , until the battery capacity retention rate (capacity retention rate = C n The cycle number is recorded. The greater the number of cycles, the better the cycle performance of the secondary battery.

[0166] (3) Test of high temperature resistance of isolation film:

[0167] At 25°C, charge the battery at a constant current rate of 0.33C to a cut-off voltage of 4V (100% SOC), then heat it to 100°C at a heating rate of 5°C / min, let it sit for 1 hour, then heat it to 105°C at a heating rate of 5°C / min, let it sit for 30 minutes, and continue to heat it by 5°C at a heating rate of 5°C / min. Keep it for 30 minutes after each 5°C increase until the battery cell fails (battery cell explosion or fire is considered a battery cell failure), and record the temperature at the moment of battery cell failure.

[0168] Table 4

[0169] Table 3

[0170] Conclusion: Compared with Comparative Example 1-2, the first coating layer of the isolation membrane of the battery of Example 1-13 contains dielectric material particles with a relative dielectric constant of 1000-10000; no dielectric material particles are added to the isolation membrane of the battery of Comparative Example 1, and the dielectric material particles of the first coating layer in the isolation membrane of the battery of Comparative Example 2 use aluminum oxide particles with a relative dielectric constant of 70. It can be seen from the data in Table 3 that the lithium plating area of ​​the negative electrode sheet of the battery of Example 1-13 after cycle disassembly is significantly smaller than that of Comparative Example 1-2, and the cycle performance of the battery of Example 1-13 is also higher than that of Comparative Example 1-2. This shows that the use of dielectric material particles with a relative dielectric constant of 1000-10000 in the first coating layer of the isolation membrane of the present application can not only reduce the risk of lithium plating during the fast charging process, but also improve the cycle performance of the battery during the fast charging process.

[0171] Table 5

[0172] Conclusion: Compared with Comparative Example 3, the first coating layer of the isolation membrane of the battery of Example 14-21 contains dielectric material particles with a relative dielectric constant of 1000-10000, and the second coating layer contains inorganic particles; the dielectric material particles of the first coating layer of the battery of Comparative Example 3 use aluminum oxide particles with a relative dielectric constant of 70, and the second coating layer contains inorganic particles. It can be seen from the data in Table 5 that the lithium plating area of ​​the negative electrode sheet of the battery of Example 14-21 after cycle disassembly is significantly smaller than that of Comparative Example 3, and the cycle performance of the battery of Example 14-21 is also higher than that of Comparative Example 3. At the same time, the isolation membrane of the battery of Example 14-21 has higher high temperature resistance. This shows that the isolation membrane of the present application uses dielectric material particles with a relative dielectric constant of 1000-10000 in the first coating layer and inorganic particles in the second coating layer, which can not only reduce the risk of lithium plating during the fast charging process, but also improve the cycle performance of the battery during the fast charging process, and can also improve the high temperature resistance of the isolation membrane.

[0173] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An isolation film, wherein, Comprising: Base film; A first coating provided on one side of the base film, the first coating comprising dielectric material particles having a relative dielectric constant of 1000 - 10000.

2. The separator film according to claim 1, wherein The relative dielectric constant of the dielectric material particles is 1500 - 5000.

3. The separator according to claim 1 or 2, wherein The volume average particle size Dv50 of the dielectric material particles is 200 nm - 2000 nm.

4. The separator film according to any one of claims 1-3, wherein, The volume average particle size Dv50 of the dielectric material particles is 500 nm - 1500 nm.

5. The separator film according to any one of claims 1-4, wherein, The dielectric material particles include at least one of barium titanate, lead titanate, lithium niobate, lead zirconate titanate, lead metaniobate, or barium lithium lead niobate.

6. The separator according to any one of claims 1-5, wherein, Based on the total mass of the first coating, the mass percentage of the dielectric material particles is 20% - 80%.

7. The separator according to any one of claims 1-6, wherein, Based on the total mass of the first coating, the mass percentage of the dielectric material particles is 30% - 70%.

8. The separator according to any one of claims 1-7, wherein The thickness of the first coating is 0.5 μm - 2 μm.

9. The separator film according to any one of claims 1-8, wherein, The BET specific surface area of the dielectric material particles is 0.5 m 2 / g - 6 m 2 / g.

10. The separator film according to any one of claims 1-9, wherein, The first coating further includes a first binder.

11. The separator according to claim 10, wherein The first binder includes at least one of polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, vinylidene fluoride - tetrafluoroethylene - propylene terpolymer, vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene terpolymer, tetrafluoroethylene - hexafluoropropylene copolymer, or fluorinated acrylate resin.

12. The separator film according to any one of claims 1 to 11, wherein, Further comprising a second coating provided on the side of the base film away from the first coating, the second coating comprising inorganic particles.

13. The separator film according to claim 12, wherein, The inorganic particles include at least one of silicon dioxide, aluminum oxide, zirconium dioxide, zinc oxide, magnesium oxide, sodium sulfate, barium sulfate, boehmite, or calcium carbonate.

14. The separator film according to claim 12 or 13, wherein, The volume average particle size Dv50 of the inorganic particles is 0.5 μm - 2.5 μm.

15. The separator film according to any one of claims 12-14, wherein The thickness of the second coating is 0.5 μm - 4 μm.

16. The separator according to any one of claims 12-15, wherein, Based on the total mass of the second coating, the mass percentage of the inorganic particles is 30% - 70%.

17. The separator film according to any one of claims 12-16, wherein, The second coating includes a second binder.

18. A method for preparing a separator membrane, wherein, Comprising: Forming a first coating comprising dielectric material particles on one side of a base film to obtain a separator film, the dielectric material particles having a relative dielectric constant of 1000 - 10000.

19. A battery, wherein, Comprising the separator film according to any one of claims 1 - 17 or the separator film obtained by the method according to claim 18.

20. An electrical device, wherein, Comprising the battery according to claim 19.

Images