Separator, electrochemical device, and electric device

Abstract

The invention relates to a diaphragm, an electrochemical device and an electric device, and belongs to the technical field of electrochemical energy storage. The diaphragm provided by the invention comprises a base material and a functional coating arranged on at least one side surface of the base material, the functional coating comprises a functional material, and the functional material is of a core-shell structure and comprises a core layer and a shell layer; the core layer comprises a metal-organic framework material, and the shell layer comprises silicon dioxide and a basic oxide. According to the diaphragm, the functional material is introduced into the functional coating, so that electrolyte decomposition can be effectively inhibited, the interface chemical stability of the diaphragm and the electrolyte is improved, the cycle life of the battery is prolonged, and the high-rate performance of the battery is improved.

Description

Technical Field

[0001] This application belongs to the field of electrochemical energy storage technology, specifically relating to diaphragms, electrochemical devices, and electrical devices. Background Technology

[0002] Lithium-ion batteries have become one of the most important energy storage devices, with safety, cycle life, and rate performance being key performance indicators. The separator, as a crucial component of the battery, is of paramount importance. Traditional polyolefin (such as PP / PE) separators have poor thermal stability and are prone to shrinkage at high temperatures, leading to short circuits. To address this issue, inorganic ceramic particles are often coated or laminated onto polymer separators. While this can improve thermal stability and electrolyte wettability to some extent, it catalyzes the oxidative decomposition of the electrolyte, resulting in gas generation, corrosion of electrode materials, and rapid capacity decay and shortened cycle life. Summary of the Invention

[0003] The purpose of this application is to overcome the problems existing in the prior art and to provide a diaphragm, an electrochemical device, and an electrical device.

[0004] This application is implemented through the following technical solution: This application provides a diaphragm, including a substrate and a functional coating disposed on at least one surface of the substrate. The functional coating includes a functional material, which has a core-shell structure, including a core layer and a shell layer. The core layer includes a metal-organic framework material, and the shell layer includes silicon dioxide and an alkaline oxide.

[0005] In some embodiments, the alkaline oxide includes at least one of MgO, CaO, ZnO, and Al2O3.

[0006] In some embodiments, the mass of the alkaline oxide is 3% to 15% of the mass of the functional material.

[0007] In some embodiments, the average particle size of the alkaline oxide is 1 nm to 10 nm.

[0008] In some embodiments, the average particle size of the metal-organic framework material is 50 nm to 200 nm.

[0009] In some embodiments, the thickness of the shell layer is 10nm-50nm.

[0010] In some embodiments, the metal-organic framework material includes at least one of ZIF-8, ZIF-67, ZIF-90, ZIF-65, and ZIF-11.

[0011] In some embodiments, the functional coating further includes an adhesive.

[0012] In some embodiments, the mass ratio of the functional material to the adhesive is (5:95) to (40:60).

[0013] In some embodiments, the adhesive includes at least one of polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylate, and acrylonitrile copolymer.

[0014] In some embodiments, the substrate includes at least one of polypropylene (PP), polyethylene (PE), polyphenylene sulfide, polyimide, aramid, and fiber.

[0015] In some embodiments, the thickness of the substrate is 4 μm - 12 μm.

[0016] In some embodiments, the thickness of the functional coating is 1 μm-10 μm.

[0017] Another aspect of this application provides an electrochemical device, including the diaphragm described in this application.

[0018] In some embodiments, the electrochemical device includes a positive electrode, a negative electrode, and the membrane described in this application, with the membrane disposed between the positive electrode and the negative electrode.

[0019] In another aspect, this application provides an electrical device, including the electrochemical device described in this application.

[0020] This application has the following beneficial effects: The present application provides a separator by introducing a functional coating containing functional materials on at least one side of a substrate. The functional materials have a core-shell structure, with the core layer comprising a metal-organic framework material and the shell layer comprising silicon dioxide and alkaline oxides. This can inhibit electrolyte decomposition, improve the interfacial chemical stability between the separator and the electrolyte, and enhance the cycle life and high-rate performance of the battery. Attached Figure Description

[0021] Figure 1 This is a SEM image of the diaphragm in Embodiment 1 of this application. Detailed Implementation

[0022] In the description of this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0023] In the description of this application, the use of terms such as "first," "second," etc., is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0024] Throughout the description of this application, references to "some embodiments," "partial embodiments," "one embodiment," "another embodiment," "a specific embodiment," or "partial embodiment" mean that at least one embodiment or example in this application includes the specific features, structures, materials, or characteristics described in that embodiment or example.

[0025] In the description of this application, a list of items connected by the terms “one of,” “one of,” “a kind of,” or other similar terms may mean any one of the listed items; a list of items connected by the term “at least one of” may mean any combination of the listed items.

[0026] In the description of this application, numerical ranges are referred to. Unless otherwise specified, such numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and can be combined with any other point or single value or with other lower or upper limits to form a range not explicitly stated.

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. The embodiments of this application may omit unnecessary detailed descriptions. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0028] This application provides a diaphragm, including a substrate and a functional coating disposed on at least one surface of the substrate. The functional coating includes a functional material, which has a core-shell structure, including a core layer and a shell layer. The core layer includes a metal-organic framework material, and the shell layer includes silicon dioxide and an alkaline oxide.

[0029] The present application provides a separator by introducing a functional coating containing functional materials on at least one side of a substrate. Specifically, the functional materials have a core-shell structure, with the core layer comprising a metal-organic framework material and the shell layer comprising silicon dioxide and alkaline oxides. This structure can inhibit electrolyte decomposition, improve the interfacial chemical stability between the separator and the electrolyte, and enhance the cycle life and high-rate performance of the battery.

[0030] Specifically, metal-organic framework materials possess a regular and ordered pore structure and excellent electrolyte affinity, which can promote uniform lithium-ion transport and inhibit dendrite growth. Coating its surface with silica can simultaneously ensure ion conductivity and thermal stability. Furthermore, introducing alkaline oxides into the shell can neutralize the acidic sites on the SiO2 surface, thereby inhibiting the catalytic decomposition of the electrolyte at the separator interface, reducing HF generation and electrode erosion, and thus significantly improving the battery's cycle life and coulombic efficiency.

[0031] It should be noted that the basic oxides mentioned in this application refer to oxides that are basic, such as amphoteric oxides that are both acidic and basic.

[0032] In some embodiments, the alkaline oxide includes at least one of MgO, CaO, ZnO, and Al2O3.

[0033] In some embodiments, the mass of the alkaline oxide is 3% to 15% of the mass of the functional material.

[0034] For example, the mass of the alkaline oxide is 3% to 15% of the mass of the functional material, such as 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or within any two of the above values.

[0035] In some embodiments, the average particle size of the alkaline oxide is 1 nm to 10 nm.

[0036] For example, the average particle size of the alkaline oxide may be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm, or within the range of any two of the above values.

[0037] This study found that a suitable content of basic oxides and an average particle size can effectively neutralize the acidic sites on the SiO2 surface without blocking the channels of the metal-organic framework material and silica, thereby ensuring ion transport.

[0038] In some embodiments, the average particle size of the metal-organic framework material is 50 nm to 200 nm.

[0039] For example, the average particle size of the metal-organic framework material may be 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm or 200nm, or within the range of any two of the above values.

[0040] In some embodiments, the thickness of the shell layer is 10nm-50nm.

[0041] For example, the thickness of the shell layer may be 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm or 50nm, or within the range of any two of the above values.

[0042] The shell layer of this application includes silicon dioxide and alkaline oxide. The silicon dioxide coating layer provides excellent thermal dimensional stability, prevents high-temperature short circuits, and, combined with a stable interface, improves the overall safety performance of the battery. The nanoscale alkaline oxide loaded on it can effectively neutralize the acidic sites on the surface of silicon dioxide, so that the separator has excellent thermal stability, ionic conductivity and interfacial chemical stability.

[0043] In some embodiments, the shell layer includes a silica coating layer and an alkaline oxide loaded on the surface of the silica coating layer.

[0044] In some embodiments, the thickness of the shell refers to the thickness of the silica coating.

[0045] In some embodiments, the metal-organic framework material includes at least one of ZIF-8, ZIF-67, ZIF-90, ZIF-65, and ZIF-11.

[0046] In some embodiments, the mass of the metal-organic framework material is 40%-80% of the mass of the functional material.

[0047] In some embodiments, the mass of the silicon dioxide is 15%-55% of the mass of the functional material.

[0048] It should be noted that this application does not impose any particular restrictions on the preparation method of core-shell structured functional materials, and conventional coating methods can be used for preparation.

[0049] In some embodiments, the preparation method of the functional material includes the following steps: hydrolyzing tetraethyl orthosilicate (TEOS) to coat the surface of metal-organic framework material particles with a SiO2 layer to obtain coated particles, dispersing the obtained coated particles in a solvent, adding the metal salt corresponding to the basic oxide and a precipitant, stirring and reacting to obtain the functional material.

[0050] In some embodiments, the precipitant includes at least one of NaOH and ammonia.

[0051] It should be noted that the thickness of the SiO2 layer, i.e., the thickness of the functional material shell, can be adjusted by changing the amount of tetraethyl orthosilicate added. The content and average particle size of the basic oxide can be adjusted by changing the concentration or amount of the metal salt corresponding to the basic oxide. The average particle size of the metal-organic framework material can be adjusted by adding metal-organic framework materials with different average particle sizes or by adjusting the parameters used in its preparation.

[0052] In some embodiments, the functional coating further includes an adhesive.

[0053] In some embodiments, the mass ratio of the functional material to the binder is (5:95) to (40:60).

[0054] This study found that when the ratio of functional materials to binders is within the above-mentioned range, the functional coating can have good film-forming properties and be firmly bonded to the substrate, thereby improving the structural stability of the diaphragm.

[0055] In some embodiments, the adhesive includes at least one of polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylate, and acrylonitrile copolymer.

[0056] In some embodiments, the substrate includes at least one of polypropylene (PP), polyethylene (PE), polyphenylene sulfide, polyimide, aramid, and fiber.

[0057] In some embodiments, the thickness of the substrate is 4μm-12μm.

[0058] In some embodiments, the thickness of the functional coating is 1 μm-10 μm.

[0059] In some embodiments, the preparation method of the diaphragm includes the following steps: dissolving the binder and functional particles in a solvent, stirring evenly to obtain a functional coating slurry, coating the functional coating slurry onto at least one side surface of a substrate, and drying to obtain the diaphragm.

[0060] Another aspect of this application provides an electrochemical device, including the diaphragm described in this application.

[0061] The electrochemical device described in this application includes any device in which an electrochemical reaction occurs to interconvert chemical energy and electrical energy, and specific, non-limiting examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0062] In some embodiments, the electrochemical device includes a positive electrode, a negative electrode, and the membrane described in this application, with the membrane disposed between the positive electrode and the negative electrode.

[0063] In some embodiments, the positive electrode may include a positive current collector and a positive electrode material layer disposed on at least one side of the positive current collector.

[0064] In some embodiments, the positive current collector is a metal foil or a composite current collector. In some embodiments, the metal foil is an aluminum foil. The composite current collector may include a metal foil substrate and a conductive layer disposed on at least one side of the metal foil substrate.

[0065] In some embodiments, the conductive layer may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fiber, carbon nanofiber, graphitized carbon sheet, carbon tube, carbon nanotube, activated carbon, and mesoporous carbon.

[0066] In some embodiments, the positive electrode material layer may include a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent.

[0067] In some embodiments, the positive electrode active material is selected from LiCoO2, LiNiO2, and LiNi x Mn y O2, Li 1+ z Ni x Mn y Co 1-x-y O2, LiNi x Co y Al z The group consisting of O2, LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, Li2MnO3, LiFeO2, LiFePO4, LiMnPO4, and combinations thereof, wherein each x is independently 0.2 to 0.9; each y is independently 0.1 to 0.45; and each z is independently 0 to 0.2. The positive electrode active material of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as positive electrode active materials.

[0068] In some embodiments, the positive electrode active material is Li 1+x Ni a Mn b Co c Al (1-a-b-c) O2; where -0.2≤x≤0.2, 0≤a<1, 0≤b<1, 0≤c<1 and a+b+c≤1.

[0069] In some embodiments, the positive electrode binder includes at least one of polyvinylidene fluoride (PVDF), poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polyvinyl butyral, polyvinylpyrrolidone (PVP), acrylic acid-acrylonitrile-acrylamide copolymer, and acrylic acid-acrylonitrile-acrylate copolymer. The positive electrode binder of this application is not limited to the above materials, but also includes other materials that can be used as battery positive electrode binders.

[0070] In some embodiments, the positive electrode conductive agent may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon nanotubes, carbon nanotubes, activated carbon, and mesoporous carbon. The positive electrode conductive agent in this application is not limited to the above materials, but also includes other materials that can be used as positive electrode conductive agents in batteries.

[0071] In some embodiments, the negative electrode sheet may include a negative current collector and a negative active material layer disposed on at least one side of the negative current collector.

[0072] In some embodiments, the negative current collector is a metal foil or a composite current collector. In some embodiments, the metal foil is a copper foil. The composite current collector may include a metal foil substrate and a conductive layer disposed on at least one side of the metal foil substrate. In some embodiments, the conductive layer may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon nanotubes, activated carbon, and mesoporous carbon.

[0073] In some embodiments, the negative electrode active material layer includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent.

[0074] In some embodiments, the negative electrode active material may include natural graphite particles, synthetic graphite particles, hard carbon, soft carbon, mesophase carbon microspheres (MCMB), Sn, SnO2, SnO, Li4Ti5O12 The negative electrode active material is selected from at least one of LTO, Si material, silicon-carbon (Si-C) composite material, silicon-nitrogen (Si-N) composite material, and silicon-oxygen (Si-O) composite material. The negative electrode active material of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as negative electrode active materials for batteries.

[0075] In some embodiments, the negative electrode binder may include at least one of the following: polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, polyacrylamide, styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylic acid-acrylonitrile-acrylamide copolymer, acrylic acid-acrylonitrile-acrylate copolymer, acrylonitrile-butadiene rubber, nitrile rubber, acrylonitrile-styrene-butadiene copolymer, acryloyl rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyepoxychloropropane, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, carboxymethyl chitosan, polyester, polyamide, polyether, polyimide, polycarboxylic acid ester, polycarboxylic acid, polyurethane, alginate, fluorinated polymer, chlorinated polymer, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropylene. The negative electrode binder of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as battery negative electrode binders.

[0076] In some embodiments, the negative electrode conductive agent may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon nanotubes, activated carbon, and mesoporous carbon. The negative electrode conductive agent of this application is not limited to the above materials, but also includes other materials that can be used as battery negative electrode conductive agents.

[0077] In some embodiments, the electrochemical device includes an electrolyte, which may include at least one of a gel electrolyte, a solid electrolyte, and a liquid electrolyte.

[0078] In some embodiments, the liquid electrolyte may include a non-aqueous solvent and a lithium salt.

[0079] It should be noted that this application does not have any special requirements for organic solvents and lithium salts, and non-aqueous solvents and lithium salts commonly used in the art can be used.

[0080] In some embodiments, the lithium salt may include at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate.

[0081] In some embodiments, the non-aqueous solvent may be at least one of carbonate compounds, carboxylic acid ester compounds, and ether compounds.

[0082] In another aspect, this application provides an electrical device, including the electrochemical device described in this application.

[0083] The electrical device used in this application is not particularly limited and can be any electrical device known in the prior art. According to some embodiments of this application, the electrical device includes, but is not limited to, mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robot dogs, industrial robots, and embodied intelligent robots.

[0084] To better illustrate the purpose, technical solution, and advantages of this application, the following detailed description will be provided in conjunction with specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0085] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0086] Example 1 This embodiment provides a diaphragm, the preparation method of which includes the following steps: (1) Preparation of functional materials S1. Dissolve 1.2 g of zinc nitrate hexahydrate in 40 mL of methanol to obtain solution A. Dissolve 2.5 g of 2-methylimidazole in 40 mL of methanol to obtain solution B. Quickly pour solution B into solution A and stir vigorously at room temperature for 24 hours. After the reaction is complete, collect the white precipitate by centrifugation, wash it three times with methanol, and dry it in a vacuum drying oven at 60℃ for 12 hours to obtain ZIF-8 nanoparticles. S2. Disperse 0.1 g of the obtained ZIF-8 particles in a mixed solution of 40 mL ethanol and 10 mL ultrapure water, add 1 mL concentrated ammonia (28 wt%), sonicate for 30 minutes to ensure full dispersion, slowly add 0.2 mL LTEOS under mechanical stirring, and continue the reaction at room temperature for 6 hours. After the reaction is complete, collect the product by centrifugation, wash three times with ethanol, and dry at 60 °C to obtain ZIF-8@SiO2 core-shell particles; S3. Disperse 0.1 g of the obtained ZIF-8@SiO2 core-shell particles in 50 mL of ethanol, add 5 mL of 0.1 mol / L Mg(NO3)2 solution, stir at room temperature for 2 hours, then slowly add 3 mL of 0.1 mol / L NaOH solution at a rate of 1 mL / min using a micro-injection pump, and react at 50 °C for 3 hours. After the reaction is completed, collect the product by centrifugation, wash three times each with deionized water and ethanol, and dry in a vacuum drying oven at 60 °C for 6 hours to obtain the functional material; wherein the functional material has a core-shell structure, the core layer includes ZIF-8, and the shell layer includes silicon dioxide and MgO supported on the surface of the silicon dioxide.

[0087] (2) Preparation of the diaphragm 0.3 g of PVDF powder was dissolved in 5 g of NMP solvent and magnetically stirred until completely transparent. 0.2 g of the resulting functional material composite powder was added, and the mixture was mechanically stirred at high speed for 6 hours to form a uniform and stable slurry. The slurry was then uniformly coated onto the surface of a PP substrate using a doctor blade and dried in a vacuum drying oven at 70°C for 12 hours to obtain a separator. The thickness of the functional coating on the separator was 6 μm, and the thickness of the PP substrate was 5 μm. The SEM image of the separator obtained in this embodiment is shown below. Figure 1 As shown.

[0088] Examples 2-6 This embodiment provides a diaphragm, which differs from Embodiment 1 in that the amount of Mg(NO3)2 solution added is adjusted to achieve the parameters in Table 1.

[0089] Examples 7-10 This embodiment provides a diaphragm, which differs from Embodiment 1 in that the amount of TEOS added is adjusted to achieve the parameters in Table 1.

[0090] Examples 11-14 This embodiment provides a diaphragm, which differs from Embodiment 1 in that the concentrations of solution A and solution B are adjusted to achieve the parameters in Table 1.

[0091] Example 15 This embodiment provides a membrane, which differs from Embodiment 1 in that the Mg(NO3)2 solution is replaced with an equimolar amount of Zn(NO3)2 solution, while all other aspects are the same as in Embodiment 1, resulting in a membrane with a ZnO shell.

[0092] Example 16 This embodiment provides a diaphragm, which differs from Embodiment 1 in that the metal-organic framework material is not ZIF-8, but ZIF-67.

[0093] Comparative Example 1 This embodiment provides a diaphragm, which differs from Embodiment 1 in that it uses ZIF-8 nanoparticles as the functional material; that is, the functional material does not include a shell layer.

[0094] Comparative Example 2 This embodiment provides a diaphragm, which differs from Embodiment 1 in that it uses ZIF-8@SiO2 core-shell particles; that is, the shell layer of the functional material does not contain the alkaline oxide MgO.

[0095] Comparative Example 3 This embodiment provides a diaphragm, which differs from Embodiment 1 in that it does not contain step S2, i.e., the functional material does not include silicon dioxide.

[0096] Comparative Example 4 This embodiment provides a diaphragm, which differs from Embodiment 1 in that no functional coating is provided on the surface of the PP substrate; that is, the diaphragm in this embodiment is a PP substrate.

[0097] In the examples and comparative examples, the types of metal-organic framework materials and their average particle size, the thickness of the functional material shell, the types of basic oxides and their average particle size, and the percentage of the mass of basic oxides to the mass of the functional material in wt% are shown in Table 1. The average particle size of the metal-organic framework material was obtained by SEM. Specifically, the functional material was separated from the membrane, and the outer shell of the functional material was removed by ultrasonication to obtain the metal-organic framework material. The MOF powder was ultrasonically dispersed in ethanol or water, dropped onto a silicon wafer or conductive adhesive, dried, and then sputtered with gold. Three to five different fields of view with good particle dispersion and representativeness were selected, and at least 100 or more independent particles were measured to obtain the average particle size.

[0098] The thickness of the functional material's shell was obtained using SEM, identifying particles whose cross-sections were exposed due to fracture, folding, or being located at an edge. Multiple measurements were taken from individual particles, and statistical analysis was performed on multiple particles. For a single particle's cross-section, the shell thickness was measured at equal angular intervals (e.g., every 45 or 90 degrees) along the normal to the core-shell boundary, with 4-8 measurements taken for each particle. The average value was taken as the shell thickness for that particle. Measurements were performed on at least 30-50 different particles. All these measurements (the average value of each particle) were then averaged to obtain the average shell thickness of the material.

[0099] The average particle size of the alkaline oxides was obtained by SEM, using a method similar to that used to observe the thickness of the functional material shell. At least 30-50 different alkaline oxide particles were measured using SEM. Then, all these measurements (the average value of each particle) were averaged to obtain the average particle size of the alkaline oxides.

[0100] The percentage (wt%) of basic oxides in the functional material was obtained via ICP. The functional material was digested using a strong oxidizing acid (such as concentrated nitric acid, aqua regia, hydrofluoric acid, etc.) under high temperature and pressure (microwave digestion apparatus) to ensure all elements were converted into detectable ionic states and entered the solution. The completely digested solution was transferred to a volumetric flask and diluted to the precise volume with dilute acid to obtain the test solution. The concentration of the target element in the test solution was calculated by detecting the intensity of the characteristic signal of the target element and comparing it with a standard curve of known concentrations. At least three independent digestions and tests were performed on the same sample, and the average value was taken.

[0101] Table 1. Parameters of the negative electrode active material and all-solid-state battery in the embodiments. Thermal stability tests were conducted on the diaphragms of the examples and comparative examples. The test method was as follows: the diaphragm samples were placed in a forced-air drying oven at 150°C for 0.5 hours, and their dimensional changes were measured. The thermal shrinkage rate was calculated (thermal shrinkage rate = (initial diameter - diameter after heating) / initial diameter × 100%). The test results are shown in Table 2.

[0102] The separators from the examples and comparative examples were used to fabricate secondary batteries for performance testing. The preparation methods for the secondary batteries are as follows: (1) Preparation of positive electrode: The active material LiNi 0.6 Co 0.2 Mn 0.2O2 (NCM622), conductive agent acetylene black, and binder PVDF are mixed in a mass ratio of 96:2:2 in an appropriate amount of N-methylpyrrolidone (NMP) solvent and stirred at high speed until a uniform slurry is formed. The slurry is then uniformly coated on both sides of an aluminum foil current collector using a precision coating machine. The slurry is dried in a 120°C vacuum oven and rolled and punched to the designed size (540mm wide and 1080mm long). The slurry is then accurately weighed to ensure the positive electrode active material loading of the single cell.

[0103] (2) Preparation of negative electrode sheet: Artificial graphite, conductive agent acetylene black, thickener CMC and binder SBR are mixed in deionized water at a mass ratio of 96:1:1:2 to prepare a slurry. The slurry is then coated on both sides of the copper foil current collector using a coating machine. After drying and rolling, it is cut into the corresponding size (60 mm wide and 1080 mm long).

[0104] (3) Assembly of secondary batteries: The positive and negative electrode sheets are wound, packaged, injected with liquid, formed and capacity tested to make secondary batteries.

[0105] The secondary batteries obtained in the examples and comparative examples were subjected to the following performance tests: Cyclic performance: Constant current charge-discharge test was performed at 1C rate, voltage range 2.5-4.2V.

[0106] Rate performance: Discharge tests were conducted at 0.2C, 0.5C, 1C, 2C, and 5C rates, and then returned to 0.2C.

[0107] The test results are shown in Table 2 below.

[0108] Table 2. Performance test results of all-solid-state batteries in the examples and comparative examples. As shown in Table 2, introducing a functional coating containing functional materials on at least one side of the membrane substrate, the functional materials having a core-shell structure, the core layer including metal-organic framework materials, and the shell layer including silicon dioxide and alkaline oxides, can inhibit electrolyte decomposition, improve the interfacial chemical stability between the membrane and the electrolyte, and produce a cell with high initial discharge specific capacity, and high capacity retention rate at high rate (5C) discharge compared to low rate (0.2C) discharge, and low high-temperature thermal shrinkage rate of the membrane.

[0109] The functional material in Comparative Example 1 does not include a shell layer, resulting in a battery cell with low initial discharge specific capacity, low capacity retention rate at high rate (5C) discharge relative to low rate (0.2C) discharge, and high high-temperature thermal shrinkage rate of the separator, approaching 10%. The functional material in Comparative Example 2 does not contain the alkaline oxide MgO in its shell layer, resulting in a battery cell with low initial discharge specific capacity, low capacity retention rate at high rate (5C) discharge relative to low rate (0.2C) discharge, and high high-temperature thermal shrinkage rate of the separator, approaching 10%. 5%; Comparative Example 3 does not include silicon dioxide in its functional materials, resulting in a low initial discharge specific capacity of the battery cell, a low capacity retention rate at high rate (5C) discharge relative to low rate (0.2C) discharge, and a high high-temperature thermal shrinkage rate of 15% for the separator; Comparative Example 4 uses commercial PP separator substrate, which has poor thermal stability, resulting in a low initial discharge specific capacity of the battery cell, a low capacity retention rate at high rate (5C) discharge relative to low rate (0.2C) discharge, and a high high-temperature thermal shrinkage rate of the separator, exceeding 16%.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A diaphragm, characterized in that, The invention includes a substrate and a functional coating disposed on at least one surface of the substrate. The functional coating includes a functional material having a core-shell structure, comprising a core layer and a shell layer. The core layer comprises a metal-organic framework material, and the shell layer comprises silicon dioxide and an alkaline oxide.

2. The diaphragm according to claim 1, characterized in that, The alkaline oxide includes at least one of MgO, CaO, ZnO, and Al2O3.

3. The diaphragm according to claim 1, characterized in that, The mass of the alkaline oxide is 3% to 15% of the mass of the functional material; and / or, the average particle size of the alkaline oxide is 1 nm to 10 nm.

4. The diaphragm according to claim 1, characterized in that, The average particle size of the metal-organic framework material is 50 nm to 200 nm.

5. The diaphragm according to claim 1, characterized in that, The thickness of the shell is 10nm-50nm.

6. The diaphragm according to claim 1, characterized in that, The metal-organic framework material includes at least one of ZIF-8, ZIF-67, ZIF-90, ZIF-65, and ZIF-11.

7. The diaphragm according to claim 1, characterized in that, The functional coating also includes an adhesive; the mass ratio of the functional material to the adhesive is (5:95)-(40:60).

8. The diaphragm according to claim 7, characterized in that, The adhesive includes at least one of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene), styrene-butadiene rubber, sodium carboxymethyl cellulose, polyacrylic acid, polyacrylate, and acrylonitrile copolymer. And / or, the substrate comprises at least one of polypropylene, polyethylene, polyphenylene sulfide, polyimide, aramid, and fiber; And / or, the thickness of the substrate is 4μm-12μm; And / or, the thickness of the functional coating is 1μm-10μm.

9. An electrochemical device, characterized in that, Includes the diaphragm as described in any one of claims 1-8.

10. An electrical appliance, characterized in that, Includes the electrochemical device as described in claim 9.

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