Separator, manufacturing method thereof, and related secondary battery, battery module, battery pack, and power consumption device

Abstract

The present application relates to a separator, which includes two layers of substrate and a coating formed between the two layers of substrate, the coating includes inorganic particles, where 30% to 70% by weight of the inorganic particles are coated with a coating layer, and 70% to 30% by weight of the inorganic particles are not coated, based on the total weight of the inorganic particles. The separator can achieve high mechanical strength, high wettability and good interfacial bonding, and can effectively inhibit the growth of lithium dendrites, thereby improving the cycle performance of secondary batteries.

Description

[Technical Field]

[0001] The present application relates to the field of secondary battery technology, and in particular to a separator, its manufacturing method, and its associated secondary batteries, battery modules, battery packs, and power consuming devices. [Background technology]

[0002] In recent years, as the application range of lithium ion batteries becomes wider and wider, lithium ion batteries are widely used in energy storage power systems such as hydroelectric power, thermal power, wind power and solar power plants, as well as in multiple fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Due to the rapid development of lithium ion batteries, higher requirements are being placed on their energy density, cycle performance and safety performance.

[0003] In secondary battery construction, the separator is one of the key inner layer assemblies and has a significant impact on the overall performance of lithium ion batteries. However, the performance of separators used in conventional technologies needs to be further improved. Summary of the Invention

[0004] The present application has been made in view of the above-mentioned problems, and an object of the application is to provide a separator that has high mechanical strength, high wettability, and good interfacial bonding properties, and that provides a secondary battery including the separator with improved cycle performance.

[0005] In order to achieve the above object, a first aspect of the present application provides a separator, the separator comprising two layers of substrate and a coating formed between the two layers of substrate, the coating comprising inorganic particles, wherein, based on the total weight of the inorganic particles, 30 wt % to 70 wt % of the surfaces of the inorganic particles are coated with a coating layer, and 70 wt % to 30 wt % of the surfaces of the inorganic particles are uncoated.

[0006] By placing inorganic particles whose surfaces are coated with a coating layer and inorganic particles whose surfaces are not coated between the substrates in a certain ratio, the separator can be endowed with high mechanical strength and high wettability, and good interfacial bonding can be achieved, while at the same time effectively suppressing the growth of lithium dendrites.

[0007] In any embodiment, the inorganic particles are selected from at least one of Si, Si oxides, Si nitrides, Fe oxides, Fe nitrides, Fe oxyacid salts, Sn oxides, Ti oxides, Ti nitrides, Cu oxides, Cu nitrides, Mn oxides, Ge oxides, Ni oxides, ZrO, ZnO, and AlN; Optionally, the inorganic particles are selected from at least one of SiO2, Si, SiO, SnO2, ZnO, Fe2O3, NiO, CuO, TiO2, and FePO4.

[0008] In any embodiment, the particle size Dv50 of the inorganic particles is from 0.01 μm to 10 μm, optionally from 0.05 μm to 0.5 μm.

[0009] The inorganic particles of the present application can ensure better adhesion to the substrate, particularly improving the separator's breathability and ion conductivity, contributing to the battery's capacity and cycle life. The introduction of small-sized inorganic particles also significantly improves the separator's porosity, promoting lithium diffusion without significantly increasing the battery impedance.

[0010] In any of the embodiments, the material forming the coating layer is selected from at least one of polyvinylidene fluoride (PVDF), polydopamine (PDA), polyaniline (PAN), polyimide (PI), and polymethyl methacrylate (PMMA).

[0011] Coating the inorganic particles with a polymeric material that has adhesive properties can also help the particles to better adhere to the substrate surface.

[0012] In any embodiment, in the inorganic particles whose surfaces are coated with a coating layer, the mass ratio of the coating layer to the coated inorganic particles is (0.05 to 2):1, optionally (0.1 to 0.6):1.

[0013] By coating the inorganic particles with the coating layer of the above mass, the mechanical properties and wettability of the separator can be better ensured.

[0014] In any embodiment, the thickness of the coating layer is between 3 nm and 10 nm, optionally between 5 nm and 8 nm.

[0015] In any embodiment, the coating has a thickness of 1 μm to 10 μm, optionally 2 μm to 8 μm, and / or a coverage of 5 g / m 2 ~50 g / m 2 and optionally 10 g / m 2 ~20 g / m 2 and / or the thickness of the separator is 10 μm to 20 μm.

[0016] In the present application, by setting the coating thickness within the above range, the internal resistance of the battery can be better ensured within an appropriate range, making it easier for lithium ions to pass through the separator and thereby ensuring battery performance.

[0017] In any embodiment, the coating comprises 80% to 99% by weight, optionally 85% to 96.5% by weight of the inorganic particles of the present application, and / or 1% to 5% by weight of an adhesive, and / or 1% to 3% by weight of a dispersant, and / or 0.1% to 1% by weight of a thickener, all based on the total weight of the coating.

[0018] By using the various components in the above proportions, it can be better ensured that the resulting separator can achieve the technical effects of the present invention.

[0019] In either embodiment, the adhesive is selected from at least one of sodium carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR).

[0020] The adhesive can better ensure that the coating of the separator of the present invention has excellent mechanical properties and is not easily broken.

[0021] In any embodiment, the dispersing agent is selected from at least one of hydrolyzed polymaleic anhydride, acrylic block polymers, polyester block polymers, polyethylene glycol-based polyols, and polyethyleneimine derivatives.

[0022] The dispersant can ensure better dispersion uniformity among the inorganic particles.

[0023] In any embodiment, the thickening agent is selected from at least one of sodium hydroxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, polyacrylates, polyurethanes, and polyethers.

[0024] The thickener can improve the viscosity of the paint and keep the paint uniform and stable.

[0025] In any embodiment, the material forming the substrate is selected from at least one of polypropylene, polyethylene, polyamide, polyester, polytetrafluoroethylene, polyvinylidene fluoride, and polyvinyl chloride.

[0026] The substrate is a polymer type, has good mechanical strength and is chemically resistant.

[0027] In any embodiment, the thickness of the substrate is from 3 μm to 30 μm, optionally from 5 μm to 25 μm.

[0028] In any embodiment, the substrate is a porous membrane, the porosity of which is between 30% and 80%, optionally between 40% and 50%.

[0029] In any embodiment, the number average molecular weight of the material forming the substrate is 100,000 to 1,000,000.

[0030] A second aspect of the present application provides a method for producing a separator, the separator comprising two layers of substrate and a coating formed between the two layers of substrate, the coating comprising inorganic particles, wherein, based on the total weight of the inorganic particles, 30 wt % to 70 wt % of the surfaces of the inorganic particles are coated with a coating layer and 70 wt % to 30 wt % of the surfaces of the inorganic particles are uncoated; The method comprises: Step (1) of uniformly dispersing inorganic particles in an organic solvent to obtain a dispersion of inorganic particles; Step (2) of adding a material for forming a coating layer to the dispersion obtained in step (1) to obtain inorganic particles whose surfaces are coated with a coating layer; Step (3) is to add the inorganic particles with the surface coated with the coating layer obtained in step (2) together with the inorganic particles with the surface uncoated to an organic solvent, and then add an adhesive, a dispersant and a thickener, and then stir uniformly to obtain a coating material for coating a substrate; The coating material obtained in step (3) is uniformly applied to one substrate, and then another substrate is placed on one side of the coated substrate to obtain a separator (4).

[0031] The above method can ensure that the separator produced has the effects described in the present invention, i.e., high mechanical strength and high wettability, and can also achieve good interfacial bonding, while effectively suppressing the growth of lithium dendrites.

[0032] In any embodiment, in step (1), the weight ratio of the inorganic particles to the organic solvent is 1:(15 to 45).

[0033] The above ratio can better ensure that the inorganic particles can be in sufficient contact with the material forming the coating layer, thereby achieving uniform coating.

[0034] In any embodiment, in step (2), the weight ratio of the material forming the coating layer to the inorganic particles is (1-10):1, optionally (2-6):1.

[0035] The above weight ratio can ensure that the surfaces of all inorganic particles are sufficiently coated.

[0036] In any embodiment, in step (3), the solid content of the paint is 30% by weight to 60% by weight.

[0037] A moderate solids content can ensure that the final applied coating can achieve the required performance.

[0038] In either embodiment, the organic solvents in steps (1) and (3) can be the same or different, and optionally, the organic solvent is selected from at least one of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), and tetrahydrofuran (THF).

[0039] In any embodiment, in step (4), after covering one side of the paint-coated substrate with another substrate, hot pressing and vacuum drying are performed, and / or the hot pressing is performed in a hot press machine, where the pressure is 3 MPa to 8 MPa, and / or the temperature is 100°C to 150°C, and / or the hot pressing time is 1 minute to 10 minutes, and / or the drying temperature is 80°C to 120°C.

[0040] A third aspect of the present application provides a secondary battery, the secondary battery comprising the separator according to the first aspect of the present application or a separator produced by the method according to the second aspect of the present application.

[0041] A fourth aspect of the present application provides a battery module, the battery module including the secondary battery according to the third aspect of the present application.

[0042] A fifth aspect of the present application provides a battery pack, the battery pack including the battery module according to the fourth aspect of the present application.

[0043] A sixth aspect of the present application provides a power consumption device, the power consumption device including at least one of the secondary battery described in the third aspect of the present application, the battery module described in the fourth aspect of the present application, or the battery pack described in the fifth aspect of the present application.

[0044] The separator of the present application has excellent mechanical strength, wettability, and electrolyte absorption rate. A secondary battery using the separator of the present application has good cycle performance in both low-rate and high-rate current cycles.

[0045] Since the power consumption device of the present application includes at least one of the secondary battery, battery module or battery pack of the present application, it has at least the same advantages as the secondary battery. [Brief explanation of the drawings]

[0046] [Figure 1] FIG. 1 is a schematic diagram of a separator according to an embodiment of the present application. [Figure 2] 1 is a schematic diagram of a secondary battery according to an embodiment of the present application; [Figure 3] FIG. 3 is an exploded view of the secondary battery shown in FIG. 2 according to the embodiment of the present application. [Figure 4] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 5] 1 is a schematic diagram of a battery pack according to an embodiment of the present application. [Figure 6]FIG. 6 is an exploded view of the battery pack shown in FIG. 5 according to an embodiment of the present application. [Figure 7] 1 is a schematic diagram of a power consumption device in which a secondary battery according to an embodiment of the present application is used as a power source; DETAILED DESCRIPTION OF THE INVENTION

[0047] Hereinafter, embodiments specifically disclosing the separator, its manufacturing method, and related secondary batteries, battery modules, battery packs, and power consumption devices of the present application will be described in detail with appropriate reference to the drawings. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and redundant description of actually identical structures may be omitted. This is to avoid unnecessarily lengthening the following description and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0048] Hereinafter, embodiments specifically disclosing the separator and manufacturing method thereof, secondary battery, battery module, battery pack, and power consumption device of the present application will be described in detail with appropriate reference to the drawings. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and redundant description of actually identical structures may be omitted. This is to avoid unnecessarily lengthening the following description and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0049] The "ranges" disclosed herein are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit that define the boundaries of the particular range. Such defined ranges may or may not include the end values, and may be arbitrarily combined; i.e., any lower limit and any upper limit may be combined to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​1 and 2 and maximum range values ​​3, 4, and 5 are listed, the following ranges are also contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, a numerical range "a to b" is a shorthand expression representing all combinations of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed herein, with "0-5" merely being a shorthand notation for combinations of these numbers. Also, stating that a parameter is an integer ≧2 is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0050] Unless otherwise stated, all embodiments and optional embodiments in the present application may be combined with each other to form a new technical solution.

[0051] Unless otherwise stated, all technical features and optional technical features in the present application may be combined with each other to form a new technical solution.

[0052] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, a description of a method including steps (a) and (b) means that the method may include sequential steps (a) and (b), or sequential steps (b) and (a). For example, a description of a method mentioned above that may further include step (c) means 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.

[0053] Unless otherwise specified, the terms "comprise" and "comprises" used in this application may be open-ended or closed-ended. For example, the terms "comprise" and "comprises" may further include or include other components not listed, or may include or include only the listed components.

[0054] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any one of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0055] Unless otherwise stated, all embodiments and optional embodiments in the present application may be combined with each other to form a new technical solution.

[0056] Unless otherwise stated, all technical features and optional technical features in the present application may be combined with each other to form a new technical solution.

[0057] Unless otherwise stated, all operations in this application are carried out at ambient temperature (25°C) and atmospheric pressure (101 kPa).

[0058] According to the inventor's research, conventional technologies involve coating inorganic particles with a coating material and then coating the resulting separator on a substrate. While the resulting separator has excellent mechanical properties and wettability, the resulting secondary battery lacks resistance to lithium dendrites and exhibits poor cycle performance. Without being bound by any theory, it is believed that because the inorganic particles are currently completely coated, lithium dendrites cannot directly contact and react with the inorganic particles after growth, resulting in a reduced dendrite resistance of the separator. The inventor's unexpected discovery was that by coating a substrate with a mixture of inorganic particles whose surfaces are coated with a coating layer and inorganic particles whose surfaces are uncoated, the resulting separator achieves high mechanical strength, high wettability, and good interfacial bonding (especially electrolyte absorption), effectively inhibiting lithium dendrite growth and thereby improving the cycle performance of the secondary battery.

[0059] Therefore, a first aspect of the present application provides a separator, the separator comprising two layers of substrate and a coating formed between the two layers of substrate, the coating comprising inorganic particles, wherein, based on the total weight of the inorganic particles, 30 wt % to 70 wt % of the surfaces of the inorganic particles are coated with a coating layer, and 70 wt % to 30 wt % of the surfaces of the inorganic particles are uncoated.

[0060] In some embodiments, the coating comprises inorganic particles, wherein 40% to 60% by weight, optionally 45% to 55% by weight, of the surfaces of the inorganic particles are coated with the coating layer, and 60% to 40% by weight, optionally 55% to 45% by weight, of the surfaces of the inorganic particles are uncoated, based on the total weight of the inorganic particles.

[0061] The separator containing the two-layer substrate of the present application prevents direct contact of inorganic particles with the positive and negative electrodes, thereby avoiding the occurrence of many side reactions. These side reactions consume lithium and reduce battery capacity and cycle life. Compared to conventional separators with inorganic particle coatings on both sides, the sandwich structure of the separator is more stable.

[0062] The separator of the present application can further improve the performance of a secondary battery if it satisfies the above design conditions and, optionally, further satisfies one or more of the following conditions:

[0063] In some embodiments, the inorganic particles are selected from at least one of Si, Si oxides, Si nitrides, Fe oxides, Fe nitrides, Fe oxyacid salts, Sn oxides, Ti oxides, Ti nitrides, Cu oxides, Cu nitrides, Mn oxides, Ge oxides, Ni oxides, ZrO, ZnO, and AlN; Optionally, the inorganic particles are selected from at least one of SiO2, Si, SiO, SnO2, ZnO, Fe2O3, NiO, CuO, TiO2, and FePO4, which have good mechanical strength, high electrochemical stability, and excellent wettability with respect to the electrolyte, thereby ensuring better realization of the technical effects of the present invention.

[0064] In some embodiments, the inorganic particles are selected from at least one of SiO2, Fe2O3, SnO2, TiO2, and CuO. Silicon dioxide undergoes a lithium absorption reaction, absorbing Li dendrites in a timely manner and preventing further growth of Li dendrites. Ferric oxide can undergo an alloying reaction with lithium dendrites, resulting in a high specific capacity, good stability, and low electronic conductivity, which is beneficial for lithium dendrite consumption and reduces the internal resistance of the separator. Titanium dioxide can undergo an intercalation reaction with lithium dendrites to produce lithium titanate, which has a high theoretical capacity and a stable structure, and the oxide structure does not change significantly after lithium absorption. Copper oxide undergoes a conversion reaction with lithium to produce amorphous Li2O and nano-sized metallic copper particles. The resulting nano-sized copper particles can further react with Li2O to produce oxide, resulting in high specific capacity and good cycle performance.

[0065] In some embodiments, the inorganic particles have a particle size Dv50 of 0.01 μm to 10 μm, optionally 0.05 μm to 0.5 μm, and further optionally 0.08 μm to 0.3 μm. When the particle size of the inorganic particles of the present application is within the above range, the inorganic particles can be better adhered to the substrate, particularly improving the separator's breathability and ion conductivity, contributing to the battery's capacity and cycle life. The introduction of small-sized inorganic particles also significantly improves the separator's porosity, promoting lithium diffusion without significantly increasing battery impedance.

[0066] Dv50 has a meaning known in the art and can be measured using instruments and methods known in the art, for example, GB / T 19077-2016 Laser Diffraction Particle Size Distribution Method, using a laser particle size analyzer (e.g., Master Size 3000).

[0067] In some embodiments, the material forming the coating layer is selected from at least one of polyvinylidene fluoride (PVDF), polydopamine (PDA), polyaniline (PAN), polyimide (PI), and polymethyl methacrylate (PMMA). Coating inorganic particles with a polymeric material having adhesive properties can also improve the adhesion of the particles to the substrate surface.

[0068] In some embodiments, the number average molecular weight of the material forming the coating layer is 10,000 to 1,000,000, optionally 15,000 to 100,000, and further optionally 20,000 to 80,000.

[0069] In this application, the number average molecular weight is measured by gel permeation chromatography (GPC) method according to GB / T 21863-2008 "Gel permeation chromatography (GPC) with tetrahydrofuran washes".

[0070] In some embodiments, in inorganic particles whose surfaces are coated with a coating layer, the mass ratio of the coating layer to the coated inorganic particles is (0.05-2):1, optionally (0.1-0.6):1, and further optionally (0.35-0.55):1.

[0071] In some embodiments, the weight ratio of the coating layer to all inorganic particles is (0.05-0.5):1, optionally (0.1-0.4):1, and further optionally (0.15-0.35):1, where it should be understood that the weight of all inorganic particles does not include the weight of the coating layer.

[0072] In some embodiments, the coating layer has a thickness of 3 nm to 10 nm, optionally 5 nm to 8 nm.

[0073] In the present application, the thickness of the coating layer can be measured by a scanning electron microscope (SEM), and the measured value is the average value of multiple measurements (for example, 10 to 100).

[0074] In some embodiments, the coating has a thickness of 1 μm to 10 μm, optionally 2 μm to 8 μm, and / or a coverage of 5 g / m 2 ~50 g / m 2 and optionally 10 g / m 2 ~20 g / m 2 and / or the thickness of the separator is 10 μm to 20 μm, and optionally 12 μm to 18 μm. In this specification, unless otherwise specified, the coating weight is the coating weight measured after the coating has dried, and the measurement method is known to those skilled in the art. For example, the coating weight can be calculated by measuring the mass of the coating applied per unit area.

[0075] In the present application, by setting the coating thickness within the above range, the internal resistance of the battery can be better ensured within an appropriate range, making it easier for lithium ions to pass through the separator and thereby ensuring battery performance.

[0076] In some embodiments, the coating comprises 80% to 99% by weight, optionally 85% to 95% by weight, of the inorganic particles of the present application, and / or 1% to 5% by weight, optionally 1.2% to 3.0% by weight, of an adhesive, and / or 1% to 3% by weight, optionally 1.2% to 2.5% by weight, of a dispersant, and / or 0.1% to 1% by weight, optionally 0.4% to 1.5% by weight, of a thickener, all based on the total weight of the coating. It should be understood that the inorganic particles include inorganic particles whose surfaces are uncoated and inorganic particles whose surfaces are coated with a coating layer.

[0077] In some embodiments, the adhesive is selected from at least one of sodium carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR), optionally, the adhesive is sodium carboxymethyl cellulose (CMC).

[0078] In some embodiments, the dispersing agent is selected from at least one of hydrolyzed polymaleic anhydride (CAS number 26099-09-02), acrylic block polymers, polyester block polymers, polyethylene glycol-based polyols, and polyethyleneimine derivatives.

[0079] In some embodiments, the relative molecular weight of the hydrolyzed polymaleic anhydride is 400 to 800, and the number average molecular weight of the acrylic block polymer, polyester block polymer, polyethylene glycol polyol and polyethyleneimine derivative is generally 50,000 to 1,000,000, optionally 60,000 to 800,000.

[0080] In some embodiments, the thickening agent is selected from at least one of sodium hydroxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, polyacrylates, polyurethanes, and polyethers.

[0081] The separator of the present application has excellent hydrophilicity, which solves the problem of poor affinity with highly polar electrolytes, and can absorb and retain the electrolyte. Furthermore, by improving the heat resistance and mechanical properties of the separator, the electrical performance and safety of the battery can also be improved.

[0082] In this application, in addition to the above components, the coating may further contain other additives, such as a surfactant to reduce the surface tension of the paint and improve the affinity between the separator and the paint, examples of which include fluorocarbon-based surfactants, silane-based surfactants, and polyol-based surfactants. A conductive agent is used to enhance the conduction of lithium ions, and carbon nanotubes are often used to improve conductivity and strengthen the PVDF skeleton structure.

[0083] In some embodiments, the material forming the substrate is selected from at least one of polypropylene, polyethylene, polyamide, polyester, polytetrafluoroethylene, polyvinylidene fluoride, and polyvinyl chloride.

[0084] In some embodiments, the thickness of the substrate is between 3 μm and 30 μm, optionally between 5 μm and 25 μm, and further optionally between 6 μm and 10 μm.

[0085] In some embodiments, the substrate is a porous membrane, the porosity of which is between 30% and 80%, optionally between 40% and 50%.

[0086] In some embodiments, the number average molecular weight of the material forming the substrate is 100,000 to 1,000,000.

[0087] During multiple charge / discharge cycles of a lithium metal battery, lithium dendrites inevitably form. These dendrites grow and eventually penetrate the separator, eventually contacting the coating. The separator of the present application includes a two-layer substrate and a coating formed between the two substrate layers. The coating contains inorganic particles with some of their surfaces uncoated, which can react with the lithium dendrites to consume the lithium generated, thereby inhibiting the growth of lithium dendrites and preventing short circuits in the battery. At the same time, the coating also contains inorganic particles with a coating layer on their surfaces, which can increase the specific surface area and micropores of the separator, thereby further improving the separator's liquid absorption, retention, and wettability, as well as increasing the number of contact sites and conduction paths. This further enhances ionic conductivity, shortens the conduction distance, reduces concentration polarization, and further improves the battery's fast charging performance.

[0088] A second aspect of the present application provides a method for producing a separator, the separator comprising two layers of substrate and a coating formed between the two layers of substrate, the coating comprising inorganic particles, wherein, based on the total weight of the inorganic particles, 30 wt % to 70 wt % of the surfaces of the inorganic particles are coated with a coating layer and 70 wt % to 30 wt % of the surfaces of the inorganic particles are uncoated; The method comprises: Step (1) of uniformly dispersing inorganic particles in an organic solvent to obtain a dispersion of inorganic particles; Step (2) of adding a material for forming a coating layer to the dispersion obtained in step (1) to obtain inorganic particles whose surfaces are coated with a coating layer; Step (3) is to add the inorganic particles with the surface coated with the coating layer obtained in step (2) together with the inorganic particles with the surface uncoated to an organic solvent, and then add an adhesive, a dispersant and a thickener, and then stir uniformly to obtain a coating material for coating a substrate; The coating material obtained in step (3) is uniformly applied to one substrate, and then another substrate is placed on one side of the coated substrate to obtain a separator (4).

[0089] In some embodiments, in step (1), the weight ratio of the inorganic particles to the organic solvent is 1:(15-45), optionally 1:(16-30).

[0090] In some embodiments, in step (2), the weight ratio of the material forming the coating layer used to the inorganic particles is (1-10):1, optionally (2-6):1.

[0091] In some embodiments, in step (2), a material for forming a coating layer is added to the dispersion obtained in step (1), and the mixture is stirred uniformly, centrifuged, dried, and polished.

[0092] In some embodiments, in step (2), the stirring rotation speed is 500 rpm to 1000 rpm, optionally 700 rpm to 900 rpm, and optionally the stirring time is 1 hour to 6 hours, optionally 2 hours to 4 hours.

[0093] In some embodiments, in step (2), the centrifuge rotation speed is 8000 rpm to 15000 rpm, optionally 9000 rpm to 12000 rpm. As can be seen, after centrifugation, the centrate is collected and dried.

[0094] In some embodiments, in step (2), the drying temperature is 80 to 180°C, optionally 100 to 150°C, and the drying time may be 2 to 24 hours, optionally 5 to 15 hours.

[0095] In some embodiments, the particle size of the polishing is set to 1 μm to 10 μm, and optionally 2 μm to 8 μm. It should be understood that the polishing in step (2) is performed to prevent the inorganic particles from agglomerating, and does not change the particle size of the inorganic particles added earlier. Therefore, in some embodiments, the particle size of the polishing in step (2) is set to be larger than the particle size of the inorganic particles. In some embodiments, in step (3), the solids content of the paint is 30% to 60% by weight, optionally 40% to 50% by weight.

[0096] The solids content of the paint can be tested in the following manner.

[0097] Take a paint weighing M1, put it in an oven and leave it to dry at 120°C for 48 hours. After drying, the weight is M2, and the solid content is M2 / M1 x 100%.

[0098] In some embodiments, in step (3), the stirring rotation speed is 500 rpm to 1000 rpm, optionally 700 rpm to 900 rpm, and optionally the stirring time is 0.5 hours to 5 hours, optionally 1.5 hours to 4 hours.

[0099] In step (3), the amounts of the adhesive, dispersant and thickener used are as described above.

[0100] In some embodiments, the organic solvents in steps (1) and (3) can be the same or different, and optionally, the organic solvent is selected from at least one of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), and tetrahydrofuran (THF).

[0101] In some embodiments, in step (4), the coating of the paint may be carried out by a coating method commonly used in the art, such as blade coating.

[0102] In some embodiments, in step (4), one side of the paint-coated substrate is covered with another substrate, followed by hot pressing and vacuum drying.

[0103] In some embodiments, in step (4), the hot pressing is performed in a hot press machine, wherein the pressure is 3 MPa to 8 MPa, optionally 4 MPa to 6 MPa; the temperature is 100°C to 150°C, optionally 110°C to 140°C; the hot pressing time is 1 minute to 10 minutes, optionally 2 minutes to 8 minutes; and optionally, the drying temperature is 80°C to 120°C, optionally 90°C to 110°C.

[0104] In some embodiments, in step (4), vacuum drying is carried out for 6 hours to 15 hours, optionally for 8 hours to 13 hours. In the present application, it should be understood that "vacuum drying" refers to drying carried out at a pressure lower than atmospheric pressure, which may be 0 to 100 KPa absolute, optionally less than 75 KPa.

[0105] In this specification, the inorganic particles used in step (1) may be understood to be inorganic particles having no surface coating, and similarly, the other substrate used in step (4) is a substrate having no coating applied to its surface.

[0106] Herein, the two types of substrates used in step (4) are the same or different substrates, and optionally are the same substrates. secondary battery

[0107] A secondary battery refers to a battery that can be continuously used by activating the active material through charging after the battery has been discharged.

[0108] A secondary battery generally includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. During the charge and discharge process, active ions travel back and forth between the positive and negative electrodes, intercalating and deintercalating. The separator is placed between the positive and negative electrodes to separate them. The electrolyte conducts ions between the positive and negative electrodes. [Positive electrode]

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

[0110] For example, the positive electrode current collector has two surfaces that face each other in the thickness direction thereof, and the positive electrode film layer is disposed on either one or both of the two facing surfaces of the positive electrode current collector.

[0111] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, an aluminum foil may be used as the metal foil. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0112] In some embodiments, the positive electrode active material may be a positive electrode active material for batteries well known in the art. For example, the positive electrode active material may include at least one of a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and a modified compound of each. However, the present application is not limited to these materials, and other conventional materials usable as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Here, examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO), lithium nickel oxide (e.g., LiNiO), lithium manganese oxide (e.g., LiMnO, LiMnO), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3O2(NCM 333 (may be abbreviated as >), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (may be abbreviated as "LiNi") 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (may be abbreviated as "LiNi") 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (may be abbreviated as "LiNi") 0.8 Co 0.1 Mn 0.1 O2(NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O2) and modified compounds thereof, etc. Examples of the lithium-containing phosphate having an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0113] In some embodiments, the mass percentage of the positive electrode active material in the positive electrode membrane layer is 75% to 99%, optionally 80% to 97%.

[0114] In some embodiments, the positive electrode membrane layer optionally further comprises an adhesive. For example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0115] In some embodiments, the mass percentage of the adhesive in the positive electrode membrane layer is 0.1% to 10%, optionally 0.5% to 2.5%.

[0116] In some embodiments, the positive electrode membrane layer optionally further comprises a conductive agent, which may include, by way of example, at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0117] In some embodiments, the mass percentage of the conductive agent in the positive electrode membrane layer is 0.05% to 10%, optionally 0.5% to 3%.

[0118] In some embodiments, the positive electrode plate can be manufactured by the following method: The components for manufacturing the positive electrode plate, such as the positive electrode active material, conductive agent, adhesive, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, which is then applied to a positive electrode current collector, followed by drying, cold pressing, and other processes to obtain the positive electrode plate. [Negative electrode]

[0119] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0120] For example, the negative electrode current collector has two surfaces that face each other in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two facing surfaces of the negative electrode current collector.

[0121] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, a copper foil may be used as the metal foil. The composite current collector may include a polymeric base layer and a metal layer formed on at least one surface of the polymeric substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymeric substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0122] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries well known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of silicon elemental, silicon oxide, silicon carbon composite, silicon nitrogen composite, and silicon alloy. The tin-based material may be selected from at least one of tin elemental, tin oxide, and tin alloy. However, the present application is not limited to these materials, and other conventional materials usable as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination.

[0123] In some embodiments, the negative plate may be a metallic lithium sheet.

[0124] In some embodiments, the mass percentage of the negative electrode active material in the negative electrode film layer is 75% to 99%, optionally 80% to 97%.

[0125] In some embodiments, the negative electrode membrane layer optionally further comprises an adhesive. For example, the adhesive may be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0126] In some embodiments, the mass percentage of the adhesive in the negative electrode membrane layer is 0.1% to 3.5%, optionally 0.5% to 2.5%.

[0127] In some embodiments, the negative electrode film layer optionally further comprises a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0128] In some embodiments, the mass percentage of the conductive agent in the negative electrode membrane layer is 0.04% to 5%, optionally 0.5% to 3%.

[0129] In some embodiments, the negative electrode membrane layer optionally further comprises other auxiliary agents, such as a thickener (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0130] In some embodiments, the negative electrode plate can be manufactured by the following method: The components for manufacturing the negative electrode plate, such as the negative electrode active material, conductive agent, adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, which is then applied to a negative electrode current collector, followed by drying, cold pressing, and other processes to obtain the negative electrode plate. [Electrolyte]

[0131] The electrolyte serves to conduct ions between the positive and negative electrodes. The present application does not specifically limit the type of electrolyte, and it can be selected according to needs. For example, the electrolyte may be liquid, gel, or all solid.

[0132] In some embodiments, the electrolyte is a liquid and includes an electrolyte salt and a solvent.

[0133] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)borate, and lithium tetrafluoro(oxalato)phosphate.

[0134] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl 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, sulfolane, dimethyl sulfone, ethyl methyl sulfone, and diethyl sulfone.

[0135] In some embodiments, the solvent may be an ether solvent, such as dimethyl ether tetraethylene glycol (TEGDME), ethylene glycol dimethyl ether (DME), or 1,3-dioxolane (DOL).

[0136] In some embodiments, the solvent may be a non-aqueous solvent (organic solvent), such as a chain alkyl ester such as methyl propionate, a chain phosphate triester such as trimethyl phosphate, a nitrile solvent such as 3-methoxypropionitrile, or a branched compound having an ether bond, typified by a dendritic compound.

[0137] In some embodiments, the solvent is a fluorine-based solvent, for example, H(CF2)2OCH3, C4F9OCH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, or a linear (perfluoroalkyl) alkyl ether such as CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, i.e., 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyldecafluoropentyl methyl ... ethyl ether, 4-trifluoromethyldecafluoropentyl ethyl ether, 4-trifluoromethyldecafluoropentyl propyl ether, 5-trifluoromethyldodecafluorohexyl methyl ether, 5-trifluoromethyldodecafluorohexyl ethyl ether, 5-trifluoromethyldodecafluorohexyl propyl ether, 6-trifluoromethyltetradecafluoroheptyl methyl ether, 6-trifluoromethyltetradecafluoroheptyl ethyl ether, 6-trifluoromethyltetradecafluoroheptyl propyl ether, 7-trifluoromethylhexadecafluorooctyl methyl ether, 7-trifluoromethylhexadecafluorooctyl ethyl ether, 7-trifluoromethylhexadecafluorooctyl propyl ether, etc. Also, a mixture of two or more of the above ether solvents may be used.

[0138] In some embodiments, the concentration of the electrolyte salt in the non-aqueous electrolyte solution is, for example, 0.3 mol / L (moles per liter) or more, optionally 0.7 mol / L or more, optionally 1.7 mol / L or less, and further optionally 1.2 mol / L or less.

[0139] In some embodiments, the electrolyte solution optionally further includes additives. For example, the additives may include a negative electrode film-forming additive and a positive electrode film-forming additive, and may further include additives that can improve some battery performance, such as an additive that improves the overcharge performance of the battery or an additive that improves the high-temperature or low-temperature characteristics of the battery.

[0140] In some embodiments, the positive and negative electrode plates and separator may be wound or stacked to form an electrode assembly.

[0141] In some embodiments, the secondary battery may include an exterior packaging, which may be used to package the electrode assembly and electrolyte.

[0142] In some embodiments, the exterior of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The exterior of the secondary battery may be a flexible package, such as a bag-type flexible package. The flexible package may be made of plastic, such as polypropylene, polybutylene terephthalate, or polybutylene succinate.

[0143] In the present application, there is no particular limitation on the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, Fig. 2 shows an example of a secondary battery 5 having a rectangular structure.

[0144] In some embodiments, referring to FIG. 3 , the exterior may include a housing 51 and a cover plate 53. Here, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates surround and form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided to cover the opening and close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. An electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be selected by those skilled in the art according to actual specific needs.

[0145] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, with the specific number being selectable by those skilled in the art based on the application and capacity of the battery module.

[0146] Fig. 4 shows an example of a battery module 4. Referring to Fig. 4, in the battery module 4, the plurality of secondary batteries 5 may be arranged in order along the vertical direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fastened with fasteners.

[0147] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in the accommodating space.

[0148] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0149] 5 and 6 show an example of a battery pack 1. Referring to FIGS. 5 and 6, the battery pack 1 may include a battery case and a plurality of battery modules 4 installed in the battery case. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 is provided to cover the lower case 3 and may form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery case in any manner.

[0150] The present application also provides a power consuming device including at least one of a secondary battery, a battery module, or a battery pack according to the present application. The secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, mobile equipment (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0151] The power consumption device may be a secondary battery, a battery module, or a battery pack, depending on the requirements of the use.

[0152] 7 shows an example of a power consumption device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, which may employ a battery pack or a battery module to meet the high power and high energy density requirements of secondary batteries.

[0153] The beneficial effects of the present application are further illustrated below with reference to examples. [Example]

[0154] The following describes examples of the present application. The examples described below are illustrative and are used only to interpret the present application, and should not be understood as limiting the present application. In the examples, specific techniques or conditions are not specified, but are carried out according to the techniques or conditions described in the technical literature or product instructions. Reagents or equipment used without a specified manufacturer are all common products that can be purchased commercially. Example 1 [Separator manufacturing]

[0155] Step 1: 5 g of SiO2 (Dv50 = 100 nm) was uniformly dispersed in 100 g of N-methylpyrrolidone (NMP), and after 2 h of ultrasonic dispersion, a uniform dispersion was obtained. Step 2: 20 g of polyvinylidene fluoride (PVDF, Mn = 30,000) was added to the dispersion obtained in Step 1 and stirred for 3 h (rotation speed 800 rpm) until uniformly dispersed. The resulting solution was centrifuged (rotation speed 10,000 rpm), dried (120 °C, 12 h), and ball milled (particle size of the ball mill is 5 μm) to obtain SiO2 particles with a surface coated with polyvinylidene fluoride, weighing 7.5 g. Step 3: Add the SiO2 with the surface coated with polyvinylidene fluoride obtained in Step 2 together with 5 g of uncoated SiO2 to NMP, and add 0.2 g of carboxymethyl cellulose (CMC), 0.2 g of hydrolyzed polymaleic anhydride, and 0.1 g of sodium hydroxymethyl cellulose. Stir with a magnetic force (rotation speed 800 rpm) for 2 hours to obtain a coating material for coating the substrate, with a solid content of 46%. Step 4: The coating material obtained in Step 3 is uniformly coated onto a 7 μm thick polypropylene (PP) film (porosity 40%) by blade coating, and another 7 μm thick polypropylene film is placed on one side of the coated film, followed by hot pressing (temperature 120°C, pressure 5 MPa, 5 minutes) and vacuum drying (100°C, 12 hours) to obtain the separator of the present application, with a thickness of 17 μm, where the coating thickness is 3 μm and the coating amount is 13 g / m2 is. Example 2

[0156] The method for producing the separator was basically the same as in Example 1, except that silicon dioxide was replaced with ferric oxide (Dv50 = 100 nm). Example 3

[0157] The method for producing the separator was basically the same as in Example 1, except that silicon dioxide was replaced with tin dioxide (Dv50 = 100 nm). Example 4

[0158] The manufacturing method is basically the same as that in Example 1, except that silicon dioxide is replaced with titanium dioxide (Dv50 = 100 nm). Example 5

[0159] The method for producing the separator was basically the same as in Example 1, except that silicon dioxide was replaced with copper oxide (Dv50 = 100 nm). Example 6

[0160] The manufacturing method is basically the same as that of Example 1, except that 4 g of SiO2 is used in step 1 and 6 g of SiO2 is used in step 2. Example 7

[0161] The method for producing the separator was basically the same as in Example 1, except that 6 g of SiO2 was used in step 1 and 4 g of SiO2 was used in step 2. Example 8

[0162] The manufacturing method is basically the same as that in Example 1, except that 3 g of SiO2 is used in step 1 and 7 g of SiO2 is used in step 2. Example 9

[0163] The method for producing the separator was basically the same as in Example 1, except that 7 g of SiO2 was used in step 1 and 3 g of SiO2 was used in step 2. Comparative Example 1

[0164] The manufacturing method is basically the same as that of Example 1, except that the inorganic particles in the coating material are all SiO2 whose surfaces are coated with polyvinylidene fluoride. Comparative Example 2

[0165] The manufacturing method of the separator was basically the same as in Example 1, except that the inorganic particles in the coating material used were all uncoated SiO2. Comparative Example 3

[0166] The manufacturing method of the separator is basically the same as in Example 1, except that the separator does not include a coating. [Performance test]

[0167] Separator tensile strength (Transverse Direction, TD) test

[0168] The separator to be tested in accordance with ASTM D882-09 was cut to a size of 10 mm wide and ≥ 150 mm long, and pulled at a rate of 500 mm / min using a universal tensile tester. The maximum load value at the time of specimen breakage was obtained, and then this was divided by the cross-sectional area of ​​the separator (specimen width × substrate thickness) to calculate the tensile strength of the separator.

[0169] Separator peel strength test

[0170] A 20 mm wide standard tape (31B, purchased from Nitto) was applied to the coated surface of the separator (for testing purposes, the separator in this case consisted of only one layer of polypropylene film with a coating applied thereon) at a fixed stress (2 kg, 300 mm / min) using a roll press machine, and a 180-degree peel test was performed at a speed of 300 mm / min using a tensile tester. Peel force values ​​were obtained at 50 points over test distances of 50 mm to 120 mm, and the average value was calculated.

[0171] Separator wettability test

[0172] The test separator (for testing purposes, the separator here includes only one layer of polypropylene film with a coating applied thereon) was cut to a size of 50 mm x 50 mm, and 1 mL of standard electrolyte (1 M LiPF6 dissolved in ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a weight ratio of 1:1:1) was dropped onto one side of the separator coating, and the angle between the droplet and the separator was observed using a contact angle meter.

[0173] Separator electrolyte absorption rate test

[0174] The separator was immersed in the electrolyte (1 M LiPF6 dissolved in ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) (weight ratio 1:1:1)) for 60 minutes, removed every 10 minutes, dried, and then the separator weight was measured. The electrolyte absorption rate was calculated as (separator weight after absorbing electrolyte - initial separator weight) / initial separator weight. The higher the electrolyte absorption rate, the better the separator's wettability.

[0175] The test results are shown in Table 1.

[0176] [Table 1]

[0177] As can be seen from Table 1, the separator of the present application has mechanical strength, wettability, and electrolyte absorption rate that are equal to or greater than those of separators of conventional technology. [Separator discharge rate test]

[0178] 1) A discharge rate test was conducted using a CR2025 button battery. The battery's positive electrode current collector was aluminum foil, the positive electrode active material was lithium iron phosphate, and the weight ratio of lithium iron phosphate:conductive carbon black:PVDF adhesive was 8:1:1. The negative electrode used was a lithium sheet, the electrolyte used was 250 μL of 1 M LiPF6 (the weight ratio of ethylene carbonate (EC):diethyl carbonate (DEC) in the solvent was 1:1), and the separator was the same as that used in the above examples and comparative examples.

[0179] 2) Charging conditions: The battery was charged at room temperature in constant current-constant voltage (CC-CV) mode. First, the battery was charged at a fixed current of 0.1 C in CC mode until the voltage rose to 3.65 V. Then, the battery was switched to CC mode, with the cutoff current set to 0.02 C, and the battery was fully charged.

[0180] 3) Discharge conditions: The cells were discharged in constant current mode to 2.5 V at different discharge rates (C-rate: 0.1 C / 1 C / 3 C) and cycled for 20 cycles.

[0181] 4) The coulombic efficiency (discharge capacity / charge capacity*100%) at different discharge rates after 200 cycles was calculated and recorded, and the specific results are shown in Table 2 below.

[0182] [Table 2]

[0183] As shown in Table 2, the coulombic efficiency of the secondary batteries using the separators of the present application was superior to that of the secondary batteries using the separators of the comparative examples, which indicates that the dendrite resistance and cycle performance of the separator were both significantly improved in both low-rate and high-rate current cycles.

[0184] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves similar functions and effects within the scope of the technical solution of the present application is considered to be within the technical scope of the present application. Furthermore, various modifications that a person skilled in the art may make to the embodiments without departing from the spirit of the present application, and other forms formed by combining some of the components of the embodiments are also considered to be within the scope of the present application. [Explanation of symbols]

[0185] 1 battery pack, 2 upper case, 3 lower case, 4 battery module, 5 secondary battery, 51 housing, 52 electrode assembly, 53 top cover assembly, A coating, B substrate.

Claims

1. A separator comprising: two layers of substrate and a coating formed between the two layers of substrate; the coating comprises inorganic particles; and, based on the total weight of the inorganic particles, 30 wt % to 70 wt % of the surfaces of the inorganic particles are coated with a coating layer and 70 wt % to 30 wt % of the surfaces of the inorganic particles are uncoated; a material forming the substrate is selected from at least one of polypropylene, polyethylene, polyamide, polyester, polytetrafluoroethylene, polyvinylidene fluoride, and polyvinyl chloride; A separator, wherein the material forming the coating layer is selected from at least one of polyvinylidene fluoride (PVDF), polydopamine (PDA), polyaniline (PAn), polyimide (PI), and polymethyl methacrylate (PMMA).

2. The material forming the inorganic particles is Si, Si oxide, Si nitride, Fe oxide, Fe nitride, Fe oxyacid salt, Sn oxide, Ti oxide, Ti nitride, Cu oxide, Cu nitride, Mn oxide, Ge oxide, Ni oxide, ZrO ２ 2. The separator according to claim 1, wherein the material is selected from at least one of AlN, ZnO, and ZnO.

3. 2. The separator according to claim 1, wherein the particle diameter Dv50 of the inorganic particles is 0.01 μm to 10 μm.

4. 2. The separator according to claim 1, wherein the inorganic particles having surfaces coated with a coating layer have a mass ratio of the coating layer to the coated inorganic particles of (0.05-2):

1.

5. The separator according to claim 1, wherein the coating layer has a thickness of 3 nm to 10 nm.

6. the thickness of the coating is between 1 μm and 10 μm; The coating weight is 5 g / m ２ Up to 50 g / m ２ and The separator according to claim 1, wherein the separator has a thickness of 10 μm to 20 μm.

7. The coating comprises 80% to 99% by weight of inorganic particles; 1% to 5% by weight of an adhesive; 1% to 3% by weight of a dispersant; 0.1% to 1% by weight of a thickener, all based on the total weight of the coating; the adhesive is selected from at least one of sodium carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR); the dispersant is selected from at least one of hydrolyzed polymaleic anhydride, acrylic block polymer, polyester block polymer, polyethylene glycol polyol, and polyethyleneimine derivative; 2. The separator according to claim 1, wherein the thickener is selected from at least one of sodium hydroxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, polyacrylate, polyurethane, and polyether.

8. The thickness of the substrate is 3 μm to 30 μm, the substrate is a porous membrane, and its porosity is 30% to 80%; 2. The separator according to claim 1, wherein the material forming the substrate has a number average molecular weight of 100,000 to 1,000,000.

9. A method for producing a separator, the separator comprising two layers of substrate and a coating formed between the two layers of substrate, the coating comprising inorganic particles, wherein, based on the total weight of the inorganic particles, 30 wt % to 70 wt % of the inorganic particles have surfaces coated with a coating layer and 70 wt % to 30 wt % of the inorganic particles have surfaces that are not coated; The method comprises: Step (1) of uniformly dispersing inorganic particles in an organic solvent to obtain a dispersion of inorganic particles; Step (2) of adding a material for forming a coating layer to the dispersion obtained in step (1) to obtain inorganic particles whose surfaces are coated with a coating layer; Step (3) is to add the inorganic particles with the surface coated with the coating layer obtained in step (2) together with the inorganic particles with the surface uncoated to an organic solvent, and then add an adhesive, a dispersant and a thickener, and then stir uniformly to obtain a coating material for coating a substrate; and (4) uniformly coating one substrate with the coating material obtained in step (3), and then covering one side of the substrate coated with the coating material with another substrate to obtain a separator. a material forming the substrate is selected from at least one of polypropylene, polyethylene, polyamide, polyester, polytetrafluoroethylene, polyvinylidene fluoride, and polyvinyl chloride; The method, wherein the material forming the coating layer is selected from at least one of polyvinylidene fluoride (PVDF), polydopamine (PDA), polyaniline (PAn), polyimide (PI), and polymethyl methacrylate (PMMA).

10. The method comprises: (a) in step (1), the weight ratio of the inorganic particles to the organic solvent is 1:(15-45); (b) in step (2), the weight ratio of the material forming the coating layer to the inorganic particles is (1 to 10):1; (c) in step (3), the solid content of the paint is 30% by weight to 60% by weight; (d) the organic solvents in steps (1) and (3) may be the same or different; and The method according to claim 9, wherein in step (4), one or more of the following are satisfied: (e) covering one side of the substrate coated with the paint with another substrate, and then hot pressing and vacuum drying.

11. A secondary battery comprising the separator according to claim 1.

12. A power consuming device comprising the secondary battery of claim 11.

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