Polymer microsphere composite material and preparation method thereof, diaphragm, battery and electric equipment

Abstract

The invention provides a polymer microsphere composite material, a diaphragm, a battery and electric equipment. The polymer microsphere composite material comprises a polymer microsphere and a shell arranged on the surface of the polymer microsphere, the shell comprises nanocellulose, and the polymer microsphere comprises polyolefin grafted with a modified polymer; the modified polymer comprises at least one of an acrylate polymer, an acrylamide polymer, an acrylonitrile polymer, a methacrylic acid polymer, a styrene polymer and a maleic anhydride polymer. The polymer microsphere composite material is used for a diaphragm coating, can provide good wettability, and solves the problem that the binding power is reduced due to swelling of a traditional adhesive layer in an electrolyte.

Description

Technical Field

[0001] This invention relates to the field of battery materials, and more particularly to a polymer microsphere composite material, a separator, a battery, and electrical equipment. Background Technology

[0002] In the field of new energy vehicles, batteries need to maintain stable performance under high-rate charge and discharge and extreme temperatures (such as low or high temperature environments); in energy storage systems, batteries need to have long-term cycle stability to adapt to frequent charge and discharge demands. As one of the core components of a battery, the performance of the separator directly affects battery safety (such as inhibiting lithium dendrite growth), cycle life (maintaining the interfacial stability between the electrodes and the electrolyte), and rate performance (the ability of the electrolyte to penetrate rapidly). Therefore, developing separator materials with both high adhesion and high wettability is key to improving the overall performance of lithium batteries.

[0003] Existing lithium-ion battery separators mainly use polyolefin-based membranes (such as polyethylene and polypropylene), which have advantages including high mechanical strength, low cost, and good chemical stability. However, these polyolefin-based membranes generally suffer from insufficient adhesion and poor electrolyte wettability. While coating with an adhesive layer (such as polyvinylidene fluoride) can enhance the adhesion between the polyolefin-based membrane and the electrode, traditional adhesive materials tend to swell after absorbing electrolyte, leading to molecular chain relaxation and breakage. This reduces the bonding strength between the separator and the electrode, causing interfacial delamination, uneven electrolyte penetration, and other problems, affecting battery safety and cycle performance. Summary of the Invention

[0004] This invention provides a polymer microsphere composite material, which is constructed by modifying polyolefin microspheres and coating them with nanofiber materials to create a polymer microsphere composite material with both high adhesion and high wettability. It can be used as a membrane coating to provide good wettability and solve the problem of decreased adhesion caused by swelling of traditional adhesive layers.

[0005] The present invention also provides a method for preparing polymer microsphere composite materials, which can prepare the above-mentioned polymer microsphere composite materials, and the preparation method is simple and easy to control.

[0006] The present invention also provides a diaphragm, which, since it comprises the above-mentioned polymer microsphere composite material or is prepared by coating, has good adhesion and wettability.

[0007] The present invention also provides a battery that, because it includes the above-mentioned separator, has good safety and cycle stability.

[0008] The present invention also provides an electrical device, which, because it includes the aforementioned battery, has stable energy output and a long service life.

[0009] In a first aspect, the present invention provides a polymer microsphere composite material, comprising: polymer microspheres and a shell disposed on the surface of the polymer microspheres, the shell comprising nanocellulose, the polymer microspheres comprising: a polyolefin grafted with a modified polymer; the modified polymer comprising at least one selected from acrylate polymers, acrylamide polymers, acrylonitrile polymers, methacrylic acid polymers, styrene polymers, and maleic anhydride polymers.

[0010] In an optional embodiment, the nanocellulose includes modified nanocellulose, which includes hydrophobic groups, including at least one of silyl, acyl, ester, and isocyanate groups.

[0011] In an optional embodiment, the particle size Dv50 of the polymer microsphere composite material is 0.1 μm-5.0 μm;

[0012] And / or, the thickness of the outer shell is 50nm-2000nm;

[0013] And / or, the nanocellulose satisfies at least one of the following conditions:

[0014] a. The average diameter of the nanocellulose is ≤50nm;

[0015] b. The average length of the nanocellulose is 50nm-3000nm;

[0016] c. The aspect ratio of the nanocellulose is 5-800.

[0017] In an optional embodiment, the particle size Dv50 of the polymer microsphere composite material is 0.5 μm-2 μm;

[0018] And / or, the nanocellulose satisfies at least one of the following conditions:

[0019] a. The average diameter of the nanocellulose is 10nm-35nm;

[0020] b. The average length of the nanocellulose is 200nm-500nm;

[0021] c. The aspect ratio of the nanocellulose is 10-30.

[0022] In an optional embodiment, the polyolefin includes at least one of polyethylene, polypropylene, oxidized polyethylene, polyethylene-polyethylene glycol block copolymer, ethylene-acrylate copolymer, and 2-bromoisobutyl ester-terminated functionalized polyethylene.

[0023] In one alternative embodiment, the modified polymer accounts for 2wt%-40wt% of the mass of the polymer microspheres.

[0024] And / or, the nanocellulose accounts for 2wt%-30wt% of the mass of the polymer microsphere composite material.

[0025] Secondly, the present invention provides a method for preparing a polymer microsphere composite material, comprising the following steps:

[0026] The coating material is mixed with an oil-in-water emulsion including the polymer microspheres, and then a second emulsification treatment is performed. During the second emulsification treatment, the coating material coats the surface of the polymer microspheres to form the shell, thereby obtaining the polymer composite microsphere material; wherein the coating material includes the nanocellulose.

[0027] In an optional embodiment, the preparation process of the oil-in-water emulsion comprising the polymer microspheres includes:

[0028] An oil-phase blend comprising an organic solvent and a polyolefin grafted with a modified polymer is mixed with an aqueous-phase blend comprising an emulsifier and water, and then subjected to a first emulsification treatment to obtain an oil-in-water emulsion of the polymer microspheres; wherein, based on the total volume of the oil-phase blend and the aqueous-phase blend, the volume percentage of the oil-phase blend is 10%-30%.

[0029] In an optional embodiment, the preparation process of the polyolefin grafted with the modified polymer includes: performing a melt extrusion process on a mixture comprising a polyolefin and a modified polymer monomer to obtain the polyolefin grafted with the modified polymer, wherein the temperature of the melt extrusion process is 160°C-220°C.

[0030] And / or, the emulsifier includes at least one of fatty alcohol polyoxyethylene ether, isomeric alcohol polyoxyethylene ether, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and Tween;

[0031] And / or, the conditions for the first emulsification treatment include:

[0032] The pressure of the first emulsification treatment is 20MPa-50MPa.

[0033] And / or, the temperature of the first emulsification treatment is 140℃-160℃.

[0034] And / or, the first emulsification process is performed under conditions of a shear stirring speed of 5000 rpm-15000 rpm.

[0035] And / or, the time for the first emulsification treatment is 10-30 min.

[0036] In one alternative implementation,

[0037] The process of mixing the coating material with the oil-in-water emulsion comprising the polymer microspheres includes:

[0038] The coating material is mixed with water to obtain a dispersion;

[0039] The dispersion is mixed with the oil-in-water emulsion comprising the polymer microspheres;

[0040] And / or, the pH of the dispersion is 4-6;

[0041] And / or, in the dispersion, the mass concentration of the coating material is 0.1%-1%.

[0042] In an optional embodiment, the conditions for the second emulsification treatment include:

[0043] The pressure of the second emulsification treatment is 10 MPa-30 MPa.

[0044] And / or, the temperature of the second emulsification treatment is 25℃-40℃.

[0045] And / or, the second emulsification process is carried out at a shear stirring speed of 5000 rpm-15000 rpm.

[0046] And / or, the second emulsification treatment time is 10-30 min.

[0047] Thirdly, the present invention provides a diaphragm comprising a polymer microsphere composite material or a polymer microsphere composite material prepared by the above preparation method.

[0048] In an alternative embodiment, the diaphragm includes a base membrane and a coating disposed on at least one side of the base membrane, the coating comprising the polymer microsphere composite material.

[0049] In an optional embodiment, the coating further includes inorganic particles; the inorganic particles include at least one selected from perovskite, metal oxides, boehmite, barium sulfate, magnesium hydroxide, aluminum hydroxide, silicon dioxide, and calcium carbonate.

[0050] And / or, the polymer microsphere composite material accounts for 10%-100% of the total mass of the polymer microsphere composite material and the inorganic particles;

[0051] And / or, the Dv50 of the inorganic particles is 0.1 μm-0.8 μm;

[0052] And / or, the thickness of the coating is 0.2μm-6μm, preferably 0.5μm-3μm;

[0053] And / or, the areal density of the coating is 0.1 g / m²-5 g / m².

[0054] Fourthly, the present invention provides a battery comprising a positive electrode, a negative electrode, and the aforementioned separator; the separator is disposed between the positive electrode and the negative electrode.

[0055] Fifthly, the present invention provides an electrical device comprising the battery described in the fifth aspect.

[0056] The polymer microsphere composite material of the present invention, through the coating of modified polyolefin microspheres and nanocellulose, is used as a separator coating, which can provide good and uniform wettability, and at the same time solve the problem of decreased adhesion caused by swelling of traditional adhesive layers in electrolyte, which is beneficial to improving the cycle performance of the battery. Attached Figure Description

[0057] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0058] Figure 1 This is a schematic diagram of the structure of a polymer microsphere composite material according to a specific embodiment of the present invention;

[0059] In the figure, 1-polymer microspheres, 2-modified polymer, 3-nanocellulose. Detailed Implementation

[0060] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] In this application, the terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0062] In this application, references to "an embodiment," "an example," or "an example" mean that a specific feature, structure, or characteristic described in connection with that embodiment, example, or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination.

[0063] To improve the adhesion and wettability of polyolefins, inorganic coatings and adhesive layers can be coated on the surface of the polyolefin base film. Inorganic coatings increase electrolyte affinity, but the wetting rate remains slow, requiring longer electrolyte replenishment times during battery wetting and cycling. Adhesive layers, due to their large volume expansion after absorbing electrolyte, experience cohesive collapse, molecular chain relaxation and breakage, leading to weakened adhesion between the separator and electrodes, poor interfacial bonding, and negatively impacting battery performance, while also posing safety risks. Furthermore, coating the base film with both adhesive and inorganic layers significantly increases the total thickness of the separator, reducing the battery's energy density.

[0064] Mixing polyolefin microspheres and nanofibers through simple physical mixing and then coating them onto the surface of a base membrane can reduce the total coating thickness. However, the physical mixing of nanofibers is prone to agglomeration, leading to uneven dispersion of nanofibers on the base membrane surface. Furthermore, nanocellulose can clog the pores of the base membrane, increasing the membrane's permeability, significantly increasing impedance, reducing ionic conductivity, and exacerbating the deterioration of battery cycle performance. However, reducing the proportion of nanocellulose does not significantly improve wettability. Therefore, simple physical mixing has certain drawbacks and risks, and does not fundamentally improve the problems of adhesion and wettability. To address these issues, the present invention provides the following technical solution:

[0065] In a first aspect, the present invention provides a polymer microsphere composite material, the structure of which is described below. Figure 1 The invention includes: polymer microspheres 1 and a shell disposed on the surface of the polymer microspheres, the shell including nanocellulose 3, the polymer microspheres including: polyolefin grafted with modified polymer 2; the modified polymer including at least one of acrylate polymers, acrylamide polymers, acrylonitrile polymers, methacrylic acid polymers, styrene polymers, and maleic anhydride polymers.

[0066] The polymer microsphere composite material of this invention exhibits excellent adhesion and wettability, making it suitable for coating diaphragms to form functional coatings. The main reasons for this include: the excellent thermodynamic compatibility between polyolefins and PP / PE diaphragm base films; during the drying process after coating, the polyolefins soften or even melt, forming physical entanglement and co-crystallization with the diaphragm base film. This is equivalent to establishing numerous "micro-anchor points" between the coating and the diaphragm substrate, preventing the coating from detaching from the smooth diaphragm surface. Furthermore, the polymer microspheres in this invention also include modified polymers, which, through grafting with polyolefins, significantly enhance the adhesion of the polymer microspheres, acting as "adhesion reinforcing elements." This further endows the polymer microsphere composite material with strong adhesion, enabling it to adhere more firmly to the electrode and diaphragm base film. Simultaneously, the polymer microspheres are coated with a shell containing nanocellulose, which rapidly adsorbs and locks the electrolyte (especially highly polar carbonate solvents) within and on the surface of the coating, forming a continuous ion-conducting electrical pathway. This greatly reduces the contact angle between the diaphragm and the electrolyte, solving the core problem of poor wettability. In addition, the outer shell containing nanocellulose encapsulates the polymer microspheres, which can form a three-dimensional network structure on the surface of the polymer microspheres. This network structure is extremely stable at high temperatures. When the polymer microspheres melt at high temperatures, it can act as a skeleton to maintain the overall shape of the diaphragm and prevent internal short circuits caused by thermal shrinkage.

[0067] In summary, the polymer microsphere composite material of the present invention includes: polymer microspheres 1 and nanocellulose 3 disposed on the surface of polymer microspheres. The polymer microspheres include polyolefins grafted with modified polymer 2. It can form a structure with polyolefin as the "trunk" and modified polymer as the "branches", achieving strong cohesion and adhesion to the electrodes. With nanocellulose as the "network", a hydrophilic and tough three-dimensional functional layer is constructed, thereby greatly improving the wettability of the membrane.

[0068] In some specific embodiments, nanocellulose includes modified or unmodified nanocellulose.

[0069] In some specific embodiments, nanocellulose includes modified nanocellulose, which includes hydrophobic groups, including at least one of silyl, acyl, ester, and isocyanate groups.

[0070] The aforementioned hydrophobic groups act as "molecular bridges," binding to nanocellulose at one end and forming a strong chemical bridge with the active groups in the polymer microspheres at the other end. This not only effectively reduces the surface energy of nanocellulose and decreases its tendency to self-aggregate due to hydrogen bonding, allowing it to be more uniformly dispersed in the coating, but also achieves an upgrade from physical coating to chemical bonding between nanocellulose and polymer microspheres, thereby significantly enhancing the interfacial strength and structural stability of the polymer microsphere composite material.

[0071] In some specific embodiments, the particle size Dv50 of the polymer microsphere composite material is 0.2 μm-5.0 μm; preferably 0.5 μm-2 μm.

[0072] Among them, polymer microsphere composite materials of the above size can be more uniformly dispersed in the coating, thus providing sufficient anchoring points.

[0073] For example, the average particle size of the polymer microsphere composite material is any value of 0.5 μm, 1.0 μm, 1.5 μm, 2.0 μm, or any range between two of them.

[0074] The particle size Dv50 of polymer microsphere composites refers to the particle size value corresponding to 50% (by volume) of the cumulative particle size distribution curve. It can be regarded as the median particle size of the material and is obtained by laser diffraction particle size distribution instrument.

[0075] In some specific embodiments, the thickness of the outer shell is 50nm-2000nm.

[0076] The outer shell of this thickness can further ensure the hydrophilicity of the polymer microsphere composite material, thereby helping to further improve the wettability of the diaphragm.

[0077] For example, the thickness of the shell is any value or a range between any two of 50 nm, 100 nm, 150 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1500 nm, 2000 nm, etc.

[0078] In some specific embodiments, the thickness of the shell can be tested through the following process: A small amount of composite microsphere powder is dispersed on conductive adhesive, gently flattened, and then a 5 nm Au / Pd conductive layer is sprayed on. In a dual-beam FIB-SEM system, a 1 µm Pt protective layer is first deposited on the top of the target microsphere using a 30 kV / 7 nA beam. Then, a 15 µm × 2 µm cross-section is cut at a 52° angle using a 30 kV / 3 nA beam. Finally, a low-current polishing with a 30 kV / 0.3 nA beam is used to remove the gallium damage layer. A 2 kV, 100 pA electron beam is used to scan the cross-section perpendicularly, and the secondary electron image resolution is ≤3 nm. At a 50 k× field of view, the polymer microspheres (lower grayscale) and the outer nanocellulose shell (higher grayscale) can be clearly distinguished. The thickness of the shell can be obtained by manually taking a vertical line segment at the inner-outer boundary of the shell and reading the value.

[0079] In some specific embodiments, nanocellulose satisfies at least one of the following conditions:

[0080] a. The average diameter of nanocellulose is ≤50nm;

[0081] b. The average length of nanocellulose is 50nm-3000nm;

[0082] c. The aspect ratio of nanocellulose is 5-800.

[0083] Among them, the nanocellulose with the above average diameter has a large specific surface area, thus providing a large number of hydrophilic sites. The nanocellulose with the above average length enables it to effectively penetrate and interweave into a network in the polymer matrix. The aspect ratio is the key to forming a three-dimensional network structure. The above aspect ratio can form a stable and dense reinforcing network while ensuring good dispersibility.

[0084] For example, the average diameter of the nanocellulose is any value of 15nm, 20nm, 25nm, 30nm, 50nm, etc., or a range between any two.

[0085] For example, the average length of the nanocellulose is any value or a range between any two of 50 nm, 200 nm, 300 nm, 400 nm, 500 nm, 1000 nm, 2000 nm, 3000 nm, etc.

[0086] For example, the aspect ratio of nanocellulose is any value or a range between any two of 5, 12, 15, 20, 25, 50, 70, 100, 150, 200, 300, 400, 500, 600, 700, 800, etc.

[0087] In some specific embodiments, the particle size Dv50 of the polymer microsphere composite material is 0.5 μm-2 μm. This preferred range of polyolefin microspheres forms a more suitable intercalation with the microstructure of the membrane surface.

[0088] In some specific embodiments, nanocellulose satisfies at least one of the following conditions:

[0089] a. The average diameter of nanocellulose is 10nm-35nm;

[0090] b. The average length of nanocellulose is 200nm-500nm;

[0091] c. The aspect ratio of nanocellulose is 10-30.

[0092] Among them, the nanocellulose with the above average diameter has a larger specific surface area, thus providing more hydrophilic sites. The nanocellulose with the above average length allows it to more effectively penetrate and interweave into a network in the polymer matrix, and the above aspect ratio can further ensure good dispersibility while forming a stable and dense reinforcing network.

[0093] In some specific embodiments, the polyolefin includes at least one of polyethylene, polypropylene, oxidized polyethylene, polyethylene-polyethylene glycol block copolymer, ethylene-acrylate copolymer, and 2-bromoisobutyl ester-terminated functionalized polyethylene.

[0094] The above-described embodiments can precisely control the melting point, flexibility, and reactivity of the polymer core by selecting different types of polyolefins, thereby adapting to different diaphragm base membranes (such as different types of PE / PP) and processing technologies (such as different drying temperatures).

[0095] In some specific embodiments, the weight-average molecular weight of the polymer microspheres is 0.1w-5w.

[0096] Molecular weight directly affects the melt flowability and bonding properties of polymer microspheres. The above embodiments control the weight-average molecular weight of polymer microspheres between 0.1w and 5w, which ensures that the polymer microspheres have suitable melt flowability at appropriate drying temperatures, achieving both firm anchoring with the base film and maintaining the structural integrity of the coating.

[0097] For example, the weight-average molecular weight of the polymer microspheres can be any value of 0.5w, 1w, 2w, 3w, 4w, 5w, or any range between two of them.

[0098] In some implementations, the molecular weight of the polymer microspheres can be determined by gel permeation chromatography (GPC).

[0099] In some specific embodiments, the modified polymer accounts for 2wt%-40wt% of the polymer microspheres.

[0100] When the content of modified polymer is within the above range, it can significantly improve the adhesion of polymer microsphere composite materials, while not excessively covering the surface of polyolefin, thus affecting its anchoring effect with the membrane base film.

[0101] For example, the modified polymer accounts for a percentage of the polymer microsphere mass of any one of the following values ​​or any range between two: 2 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 40 wt%.

[0102] In some specific embodiments, nanocellulose accounts for 2wt% to 30wt% of the polymer microsphere composite material.

[0103] When the content of nanocellulose is within the above range, a more complete three-dimensional network can be formed on the surface of polymer microspheres, further improving the wettability and thermal stability of polymer microsphere composites, without adversely affecting the processing flowability of polymer microsphere composites.

[0104] For example, the proportion of nanocellulose in the total mass of the composite material can be any value or a range between any two of the following: 2 wt%, 3 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%.

[0105] The proportions of polyolefins, modified polymers, and nanocellulose in the total mass of the composite material were tested using the following method: The dried sample was placed in a TGA instrument and heated at a preset heating rate under an inert atmosphere, while simultaneously recording the TGA curve and DTG curve; the decomposition temperature range of each component was determined by the starting and ending temperatures of the weight loss step on the TGA curve, and the specific component mass percentage (W) was calculated based on the ratio of the sample mass loss (Δm) to the initial mass (m0) within this range, using the formula W=(Δm / m0)×100%.

[0106] Secondly, the present invention provides a method for preparing a polymer microsphere composite material, comprising the following steps:

[0107] The coating material is mixed with an oil-in-water emulsion including polymer microspheres, and then a second emulsification treatment is performed. During the second emulsification treatment, the coating material coats the surface of the polymer microspheres to form a shell, thereby obtaining a polymer composite microsphere material; wherein the coating material includes nanocellulose.

[0108] The above preparation method includes an oil-in-water emulsion of polymer microspheres and a coating material including nanocellulose. The second emulsification treatment can promote the nanocellulose to form a tough outer shell on the polymer microspheres.

[0109] In some embodiments, the preparation process of an oil-in-water emulsion including polymer microspheres includes:

[0110] An oil-phase blend comprising an organic solvent and a polyolefin grafted with a modified polymer is mixed with an aqueous-phase blend comprising an emulsifier and water, and then subjected to a first emulsification treatment to obtain an oil-in-water emulsion of polymer microspheres; wherein, based on the total volume of the oil-phase blend and the aqueous-phase blend, the volume percentage of the oil-phase blend is 10%-30%.

[0111] The above embodiments can prepare an oil-in-water emulsion containing polymer microspheres, which is beneficial for further coating of nanocellulose.

[0112] For example, based on the total volume of the oil phase blend and the aqueous phase blend, the volume percentage of the oil phase blend is any value of 10%, 15%, 20%, 25%, 30%, or any range between both.

[0113] For example, organic solvents include, but are not limited to, dichloromethane, ethyl acetate, n-hexane, etc.

[0114] In some embodiments, the preparation process of the polyolefin grafted with the modified polymer includes: performing a melt extrusion process on a mixture comprising a polyolefin and a modified polymer monomer to obtain a polyolefin grafted with the modified polymer, wherein the melt extrusion process is performed at a temperature of 160°C-220°C.

[0115] In the above embodiments, polyolefins and modified polymer monomers are subjected to melt extrusion treatment, which causes the modified polymer monomers to undergo a grafting reaction on the surface or molecular chain of the polyolefin, thereby generating polyolefins grafted with modified polymers in situ.

[0116] It is understood that the melt extrusion process includes adding an initiator to obtain a mixture of polyolefin, modified polymer monomer, and initiator before melt extrusion. In the above embodiments, through melt extrusion, under high temperature and shear, the initiator decomposes to generate free radicals, which initiate the grafting reaction of monomers on the surface or molecular chain of polyolefin microspheres, thereby generating polyolefin grafted with modified polymer in situ.

[0117] In some specific embodiments, the initiator includes azobisisobutyronitrile and / or benzoyl peroxide.

[0118] In some specific embodiments, the initiator accounts for 0.01 wt% to 0.1 wt% of the mass of the mixture. Initiator content within this range ensures that the grafting reaction proceeds at a moderate and controllable rate, achieving an optimal balance between high grafting efficiency and low byproduct formation. Exemplarily, the initiator mass percentage is any one of 0.01 wt%, 0.03 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, or a range between any two.

[0119] In some specific embodiments, a free radical modifier is added prior to the melt extrusion process to obtain a mixture comprising polyolefin, modified polymer monomer, initiator, and free radical modifier; exemplary, the free radical modifier comprises diphenyl ditelluride and / or dodecyl mercaptan.

[0120] In some specific embodiments, the mass percentage of the free radical modifier is 0.01wt%-0.1wt% based on the mass of the mixture; for example, the mass percentage of the free radical modifier is any value or a range between any two of 0.01wt%, 0.03wt%, 0.05wt%, 0.08wt%, 0.1wt%, etc.

[0121] In some implementations, the melt extrusion process is carried out using a twin-screw extruder.

[0122] For example, the temperature of the melt extrusion process is any value or a range of any two of the following: 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C.

[0123] In some embodiments, the emulsifier includes at least one of fatty alcohol polyoxyethylene ether, isomeric alcohol polyoxyethylene ether, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and Tween. These emulsifiers can significantly reduce the interfacial tension between oil and water, making it easier to disperse the polymer melt into fine droplets under mechanical shear force, requiring less energy to maintain this dispersion, preventing polymer melt agglomeration, and better achieving the uniform distribution and directional coating of nanocellulose in polymer microspheres.

[0124] For example, the emulsifier accounts for any value of 1 wt%, 3 wt%, 5 wt%, 8 wt%, etc., or any range between both, of the mass of the oil-in-water emulsion of the polymer microspheres.

[0125] In some embodiments, the conditions for the first emulsification treatment include:

[0126] The pressure of the first emulsification treatment is 20MPa-50MPa.

[0127] And / or, the temperature of the first emulsification treatment is 140℃-160℃.

[0128] And / or, the first emulsification process is carried out under shear stirring speeds of 5000 rpm to 15000 rpm.

[0129] And / or, the first emulsification treatment time is 10-30 min.

[0130] For example, the pressure of the first emulsification treatment is any value or a combination of any two of 20 MPa, 30 MPa, 40 MPa, 50 MPa, etc. The temperature of the first emulsification treatment is any value or a combination of any two of 140°C, 150°C, 160°C, etc. The shear stirring speed of the first emulsification treatment is any value or a combination of any two of 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, 10000 rpm, 12000 rpm, 15000 rpm, etc. The time of the first emulsification treatment is any value or a combination of any two of 10 min, 20 min, 30 min, etc.

[0131] By adjusting at least one parameter among the pressure, temperature, shear stirring speed, and time of the first emulsification treatment, the size and surface properties of polymer microspheres can be controlled. This not only provides an ideal core morphology and interface environment for the shell coating, but also benefits the integrity and stability of the shell coating, thereby further improving the wettability of the diaphragm.

[0132] In some embodiments, the process of mixing the coating material with an oil-in-water emulsion comprising polymer microspheres includes:

[0133] The coating material is mixed with water to obtain a dispersion;

[0134] The dispersion is mixed with an oil-in-water emulsion comprising polymer microspheres.

[0135] Among them, the aqueous dispersion of nanocellulose is more likely to form an O / W emulsion, which can further promote the binding of nanocellulose and polymer microspheres to form a stable shell.

[0136] In some implementations, the pH of the dispersion is 4-6.

[0137] The pH value of the dispersion protonates the nanocellulose, reducing its charge and thus making hydrophobic interactions and hydrogen bonds dominant. This makes it easier for the nanocellulose to be adsorbed onto hydrophobic surfaces or to bind to the surface of microspheres through hydrogen bonds.

[0138] For example, the pH value of the dispersion is any value of 4, 5, 6, etc., or a range of any combination of both.

[0139] In some embodiments, the mass concentration of the coating material in the dispersion is 0.1%-1%.

[0140] The mass concentration of the coating material can control the adsorption kinetics, coverage, and integrity of the intermolecular interaction network at the microsphere interface, directly affecting the density and thickness of the shell. This embodiment helps to control the microstructure of the shell at the nanoscale by adjusting the mass concentration of the coating material, thereby improving the wettability of the membrane.

[0141] For example, the mass concentration of the coating material in the dispersion is any one of 0.1%, 0.5%, 0.8%, 1%, or any range between two of these values.

[0142] In other embodiments, the conditions for the second emulsification treatment include:

[0143] The pressure for the second emulsification treatment is 10 MPa-30 MPa.

[0144] And / or, the temperature of the second emulsification treatment is 25℃-40℃.

[0145] And / or, the second emulsification process is carried out at a shear stirring speed of 5000 rpm-15000 rpm.

[0146] And / or, the second emulsification treatment time is 10-30 min.

[0147] The above embodiments control at least one parameter among the pressure, temperature, shear stirring speed, and time of the second emulsification treatment to better coat the nanocellulose onto the surface of the polymer microspheres to form a shell, while controlling the thickness of the shell.

[0148] For example, the pressure of the second emulsification treatment is any value or a combination of any two of 10 MPa, 15 MPa, 20 MPa, 25 MPa, 30 MPa, etc. The temperature of the second emulsification treatment is any value or a combination of any two of 25°C, 30°C, 35°C, 40°C, etc. The shear stirring speed of the second emulsification treatment is any value or a combination of any two of 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, 10000 rpm, 12000 rpm, 15000 rpm, etc. The time of the second emulsification treatment is any value or a combination of any two of 10 min, 15 min, 20 min, 25 min, 30 min, etc.

[0149] In some embodiments, a modification treatment is included prior to the addition of nanocellulose, the modification treatment comprising the following steps:

[0150] Modified nanocellulose is prepared by adding a modifier to a dispersion of cellulose raw materials and catalyst, stirring at 20℃-50℃ for 0.5-3h, washing, filtering, and drying.

[0151] The above methods have mild and easily controllable reaction conditions. By adjusting the amount of catalyst and modifier, the grafting rate of the modifying groups can be controlled, thereby precisely controlling the surface properties and reactivity of nanocellulose.

[0152] For example, after adding the modifier, the mixture is stirred at any value or in any range between 20°C, 25°C, 30°C, 35°C, 40°C, 50°C, etc.

[0153] For example, a modifier is added and stirred at 20°C-50°C for any value or any range between two of the following: 0.5h, 1h, 1.5h, 2h, 2.5h, 3h.

[0154] In some specific embodiments, the modifier includes at least one of γ-aminopropyltriethoxysilane, methyltrimethoxysilane (MTMS), octyltriethoxysilane (OTES), hexadecyltrimethoxysilane, acetic anhydride, propionic anhydride, butyric anhydride, phthalic anhydride, octanoic anhydride, lauric anhydride, palmitic anhydride, succinic anhydride, maleic anhydride, acetyl chloride, vinyl acetate, octadecyl isocyanate, toluene diisocyanate, diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), etc., including a dispersion of cellulose raw material and catalyst, γ-aminopropyltriethoxysilane is added, stirred at 20℃-50℃ for 0.5-3h, washed, filtered, and dried to obtain modified nanocellulose.

[0155] In some specific embodiments, the catalyst includes at least one of 2,2,6,6-tetramethylpiperidine oxide, inositol hexaphosphate, sodium hydroxide, tetrabutylammonium bromide, transaminase, lipase, and ammonia. These catalysts exhibit good catalytic activity at temperatures between 20°C and 50°C, avoiding problems such as depolymerization of nanocellulose, self-polymerization of modifiers, or destruction of functional groups that may occur at high temperatures.

[0156] In some specific implementations, the mass ratio of cellulose raw material, catalyst, and modifier is 5-6:3-5:1-2.

[0157] The above proportions of raw materials can ensure a rapid and complete reaction while minimizing byproducts.

[0158] Thirdly, the present invention provides a diaphragm comprising a polymer microsphere composite material or a polymer microsphere composite material prepared by the above preparation method.

[0159] Because the diaphragm comprises the aforementioned polymer microsphere composite material, it exhibits good adhesion and wettability.

[0160] In some embodiments, the separator includes a base membrane and a coating disposed on at least one side of the base membrane, the coating comprising a polymer microsphere composite material. Because the separator contains the polymer microsphere composite material, it possesses both high adhesion and high wettability, which is beneficial for improving the cycle performance of the battery.

[0161] In some implementations, the coating comprises inorganic particles.

[0162] Inorganic particles, with their higher melting point, are incorporated into the coating and applied to the membrane surface to form a protective layer. These inorganic particles act as a physical support framework, maintaining the membrane's shape and integrity even when the polymer matrix melts at high temperatures, preventing contact between the positive and negative electrodes. Furthermore, the uniform distribution of high-hardness inorganic particles within the coating effectively enhances the membrane's puncture resistance, making it more resistant to lithium dendrite penetration and reducing the risk of short circuits caused by dendrite growth.

[0163] In some specific embodiments, the inorganic particles include at least one of perovskite, metal oxides, boehmite, barium sulfate, magnesium hydroxide, aluminum hydroxide, silicon dioxide, and calcium carbonate. Perovskite offers high functional designability; by adjusting its elemental composition, specific functions, such as high lithium-ion selective conduction, can be achieved. Metal oxides possess high hardness, good puncture resistance, and excellent chemical stability, which is beneficial for further improving the puncture strength of the separator. Boehmite has moderate hardness, causing minimal wear on equipment and coating rollers, and its low density requires less usage, resulting in relatively low cost. Barium sulfate has a higher density, effectively enhancing the mechanical strength of the separator, while its chemical inertness helps inhibit electrolyte decomposition, thereby further improving the cycle stability of the battery. Magnesium hydroxide absorbs heat when heated, thus helping to reduce the internal temperature of the battery and delay thermal runaway; simultaneously, the magnesium oxide produced by its decomposition forms a good heat insulation layer, further enhancing battery safety. Aluminum hydroxide, similar to magnesium hydroxide, can improve battery thermal stability through endothermic decomposition. Its decomposition product, aluminum oxide, can also neutralize free hydrofluoric acid (HF) in the electrolyte, inhibiting cell gas buildup and further extending battery cycle life. Silica is low-cost and environmentally friendly; its abundant hydroxyl groups significantly improve the wettability of the separator to the electrolyte and enhance ion conduction efficiency, thereby further improving the battery's rate performance. Calcium carbonate, as a low-cost filler, effectively reduces separator manufacturing costs, while its inherent thermal stability provides basic thermal protection for the separator.

[0164] In some specific embodiments, the perovskite includes at least one of CaTiO3, SrTiO3, BaTiO3, Bi4Ti3O3, and LaBO3 (where B is Co, Ni, etc.).

[0165] In some specific embodiments, the metal oxide includes at least one selected from HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, and SiC.

[0166] In some specific embodiments, the polymer microsphere composite material accounts for 10%-100% of the total mass of the polymer microsphere composite material and inorganic particles.

[0167] The above-mentioned mass ratio of polymer microsphere composite material and inorganic particles ensures that the polymer is always the "skeleton" and main body of the coating, while the inorganic particles are the functional particles "embedded" in it. The polymer is responsible for providing flexibility, while the inorganic particles provide stiffness and strength. The two work together to make the coating both flexible enough to cope with the bending stress in the manufacturing process of battery winding and stacking, and can also appropriately improve the overall puncture strength and tensile strength through the dispersed inorganic particles.

[0168] For example, the proportion of polymer microsphere composite material to the total mass of polymer microsphere composite material and inorganic particles is any value or a range between any two of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc.

[0169] In some specific implementations, the Dv50 of the inorganic particles is 0.1 μm-0.8 μm.

[0170] Inorganic particles within the above size range are less prone to settling and clumping, ensuring the continuity and stability of subsequent coating processes.

[0171] For example, the Dv50 of inorganic particles is any value or a range between any two of 0.1 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, etc.

[0172] In an optional embodiment, the inorganic particles include at least one of perovskite, metal oxides, boehmite, barium sulfate, magnesium hydroxide, aluminum hydroxide, silicon dioxide, and calcium carbonate.

[0173] In some specific embodiments, the coating thickness is 0.2μm-6μm, preferably 0.5μm-3μm.

[0174] For example, the thickness of the coating is any value of 0.2μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, etc., or a range between any two.

[0175] The coating thickness mentioned above can reduce additional obstruction to the ion transport path, maintaining the high porosity and low resistance of the membrane.

[0176] In some specific embodiments, the areal density of the coating is 0.1 g / m² to 5 g / m².

[0177] Among them, the above-mentioned surface density of the coating can ensure that the coating can play its full role, ensure its adhesion and wettability, and at the same time ensure that the volumetric energy density and gravimetric energy density of the battery are within a suitable range.

[0178] For example, the areal density of the coating is any value or a range between 0.1 g / m², 0.5 g / m², 1 g / m², 2 g / m², 3 g / m², 4 g / m², 5 g / m², etc. In some specific embodiments, the areal density of the coating is 0.2 g / m²-1.5 g / m²;

[0179] In some specific implementations, the base film includes, but is not limited to, PP and PE.

[0180] In some specific embodiments, the thickness of the base film is 1μm-30μm, and the porosity is 20-80%.

[0181] In some specific embodiments, the coating coverage on the base film is 5%-100%.

[0182] In some specific embodiments, the coating is applied by methods including but not limited to the following: spraying, roller coating, dot coating, dip coating, and scraping coating.

[0183] Fourthly, the present invention provides a battery comprising a positive electrode, a negative electrode, and the aforementioned separator; the separator is disposed between the positive electrode and the negative electrode.

[0184] The present invention does not specifically limit the composition and material of the positive and negative electrode sheets of the battery. Exemplarily, the negative electrode sheet includes a current collector and a negative electrode active material layer located on at least one surface of the current collector. The negative electrode active material layer includes hard carbon material, conductive agent, binder and dispersant. The conductive agent can be selected from at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotube, metal powder and graphene. The binder can be selected from at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide imide, polyvinyl alcohol and sodium polyacrylate. The dispersant can be selected from at least one of sodium carboxymethyl cellulose, triethylhexyl phosphate and sodium dodecyl sulfate. The negative electrode current collector can be a conventional negative electrode current collector in the art, such as copper foil.

[0185] The aforementioned positive electrode sheet includes a current collector and a positive electrode active material layer located on at least one surface of the current collector. The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese phosphate, lithium iron phosphate, and lithium manganese iron phosphate. The conductive agent includes the aforementioned hard carbon material and, optionally, at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotubes, metal powder, and graphene. The binder may be selected from at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate. The material of the positive electrode current collector may be selected from any one or more of copper foil, titanium foil, tin foil, chromium foil, and composite foils of the above metals.

[0186] For example, the battery described above can be prepared by a method including the following process: stacking a positive electrode, a separator, and a negative electrode in sequence to obtain a battery cell, or stacking a positive electrode, a separator, and a negative electrode in sequence and then winding them to obtain a battery cell; placing the battery cell in a battery packaging film (such as an aluminum-plastic film), injecting electrolyte into the outer packaging and sealing it to obtain the battery of the present invention.

[0187] Exemplarily, the battery further includes an electrolyte comprising an organic solvent and an electrolyte salt. The organic solvent serves as a medium for ion transport in the electrochemical reaction and can be any organic solvent known in the art for use in battery electrolytes. Exemplarily, the organic solvent can be at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butenyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0188] Fifthly, the present invention provides an electrical device comprising the battery of the fifth aspect.

[0189] In some implementations, the battery includes any one of a single cell, a battery module, or a battery pack.

[0190] It should be noted that the above-mentioned electrical equipment can be any equipment that conventionally requires electricity, such as, but not limited to, computers, electric vehicles, air conditioners, refrigerators, washing machines, microwave ovens, printers, fax machines, etc.

[0191] To further understand the present invention, the technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0192] Unless otherwise specified, all reagents involved in the embodiments of this invention are commercially available products and can be purchased through commercial channels. The model of the high-speed shear dispersion emulsifier is FA25.

[0193] Example 1

[0194] This example provides a polymer microsphere composite material comprising: polymer microspheres and a shell (shell thickness of 800 nm) disposed on the surface of the polymer microspheres, the shell comprising modified nanocellulose, the polymer microspheres comprising polyolefin grafted with modified polymer, the polyolefin being polyethylene microspheres, and the modified polymer being polymethyl methacrylate; based on the total mass of the polymer microspheres as 100%, polymethyl methacrylate accounts for 20 wt%, and polyethylene microspheres account for 80 wt%; the Dv50 of the polymer microsphere composite material is 2.5 μm.

[0195] The hydrophobic group of the modified nanocellulose is silane, with an average diameter of 20 nm and an average length of 200 μm. Other parameters are shown in Table 1.

[0196] Its preparation method includes the following steps:

[0197] 1) Based on the total mass of the added materials as 100%, 50 wt% of nanocellulose raw material and 40 wt% of γ-aminopropyltriethoxysilane were thoroughly mixed in 10 wt% water, stirred at 30°C for 2 hours, washed with deionized water, filtered and dried to obtain modified nanocellulose. The modified nanocellulose had an average diameter of 20 nm and an average length of 200 nm.

[0198] 2) By mass, 80 parts of polyethylene granules, 20 parts of methyl methacrylate, and 0.04 parts of azobisisobutyronitrile were blended at room temperature. The mixture was then fed into a twin-screw extruder, and the extruder temperature was set to 210°C for granulation to obtain polymethyl methacrylate-modified polyethylene masterbatch. The masterbatch was dried at room temperature under ventilation, and then ground, dispersed, and sieved in liquid nitrogen to obtain polymer granules. The polymer granules were added to dichloromethane to form an oil-phase blend, wherein the polymer granules accounted for 20 wt% of the mass of dichloromethane. Sodium dodecyl sulfate was added to water to obtain an aqueous-phase blend. The oil-phase blend and the aqueous-phase blend were mixed at a volume ratio of 2:8, wherein the amount of sodium dodecyl sulfate accounted for 5 wt% of the polymer granules. The mixture was then subjected to a first emulsification treatment using a high-speed shear dispersion emulsifier. The first emulsification treatment was carried out at 150°C, 35 MPa, and sheared and stirred at 10,000 rpm for 20 minutes to obtain an oil-in-water emulsion of polymer microspheres.

[0199] 3) Modified nanocellulose is added to water, wherein the mass concentration of modified nanocellulose is 0.5 wt%, and the pH value of the system is adjusted to 5 to obtain a coating material. The oil-in-water emulsion of the coating material and polymer microspheres is added to a high-speed shear dispersion emulsifier, wherein the modified nanocellulose accounts for 15 wt% of the mass of the polymer microspheres, and a second emulsification treatment is performed. The first emulsification treatment is specifically performed at 30℃ and 20 MPa, with shearing and stirring at 10000 rpm for 20 min. After washing and filtration, the polymer microsphere composite material is obtained.

[0200] The above-mentioned polymer composite microsphere material is used to prepare a membrane, including the following steps:

[0201] A coating was prepared by dispersing polymer composite microspheres and boehmite (Dv50=0.5μm) in deionized water at a mass ratio of 5:5.

[0202] The coating is applied to a PE membrane substrate with a porosity of 40% using a roller coating process, forming a coating layer. The thickness of the PE membrane substrate is 9 μm, the thickness of the coating is 2 μm, and the areal density of the coating is 1.2 g / m³. 2 The coated diaphragm is obtained by drying at 70°C.

[0203] Example 2

[0204] The difference between the polymer microsphere composite material and Example 1 is that polymethyl methacrylate is replaced with polyethyl acrylate, and the Dv50 of the polymer microsphere composite material is 2.5 μm.

[0205] The preparation method differs from that in Example 2 in that methyl methacrylate is replaced with ethyl acrylate, while the rest is the same as in Example 2.

[0206] Example 3

[0207] The difference between the polymer microsphere composite material and Example 2 is that, based on the total mass of polymer microspheres as 100%, the proportion of ethyl polyacrylate is 2wt% and the proportion of polyethylene microspheres is 98wt%; the Dv50 of the polymer microsphere composite material is 0.1μm.

[0208] The preparation method differs from that in Example 2 in that, in step 2), 98 parts of polyethylene particles, 2 parts of ethyl acrylate, and 0.04 parts of azobisisobutyronitrile are blended at room temperature, and the oil phase blend and the water phase blend are mixed at a volume ratio of 1:9. The rest is the same as in Example 2.

[0209] Example 4

[0210] The difference between the polymer microsphere composite material and Example 2 is that, based on the total mass of polymer microspheres as 100%, the proportion of ethyl polyacrylate is 40wt% and the proportion of polyethylene microspheres is 60wt%; the Dv50 of the polymer microsphere composite material is 50μm.

[0211] The preparation method differs from that in Example 2 in that, in step 2), 60 parts of polyethylene particles, 40 parts of ethyl acrylate, and 0.04 parts of azobisisobutyronitrile are blended at room temperature, and the oil phase blend and the water phase blend are mixed at a volume ratio of 3:7. The rest is the same as in Example 2.

[0212] Example 5

[0213] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 1.5 μm.

[0214] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that the temperature of the first emulsification treatment is 140°C and the pressure is 20 MPa, while the rest is the same as in Example 2.

[0215] Example 6

[0216] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 3.5 μm.

[0217] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that the temperature of the first emulsification treatment is 160°C and the pressure is 50 MPa, while the rest is the same as in Example 2.

[0218] Example 7

[0219] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 1 μm.

[0220] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that the shear stirring speed of the first emulsification treatment is 5000 rpm, while the rest is the same as in Example 2.

[0221] Example 8

[0222] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 2.7 μm.

[0223] The preparation method of the polymer microsphere composite material differs from that in Example 2 in that the shear stirring speed of the first emulsification treatment is 15,000 rpm, while the rest is the same as in Example 2.

[0224] Example 9

[0225] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 1.2 μm.

[0226] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that the first emulsification treatment time is 10 min, while the rest is the same as in Example 2.

[0227] Example 10

[0228] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 4.5 μm.

[0229] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that the first emulsification treatment time is 30 min, while the rest is the same as in Example 2.

[0230] Example 11

[0231] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 2.5 μm and a shell thickness of 500 nm.

[0232] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that, in step 3), modified nanocellulose is added to water, wherein the mass concentration of modified nanocellulose is 0.1 wt%, the pH value of the system is adjusted to 5, and the coating material is obtained. The rest is the same as in Example 2.

[0233] Example 12

[0234] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 3.5 μm and a shell thickness of 1500 nm.

[0235] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that, in step 3), modified nanocellulose is added to water, wherein the mass concentration of modified nanocellulose is 1 wt%, the pH value of the system is adjusted to 5, and the coating material is obtained. The rest is the same as in Example 2.

[0236] Example 13

[0237] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 2.05 μm and a shell thickness of 50 nm.

[0238] The preparation method of the polymer microsphere composite material differs from that in Example 2 in that, in step 3), the oil-in-water emulsion of the coating material and the polymer microspheres is added to a high-speed shear dispersion emulsifier, wherein the modified nanocellulose accounts for 2 wt% of the polymer microsphere mass, and the rest is the same as in Example 2.

[0239] Example 14

[0240] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 4 μm and a shell thickness of 2000 nm.

[0241] The preparation method of the polymer microsphere composite material differs from that in Example 2 in that, in step 3), the oil-in-water emulsion of the coating material and the polymer microspheres is added to a high-speed shear dispersion emulsifier, wherein the modified nanocellulose accounts for 30 wt% of the polymer microsphere mass, and the rest is the same as in Example 2.

[0242] Example 15

[0243] The difference between the polymer microsphere composite material and Example 2 is that the average diameter of the modified nanocellulose is 50 nm, the Dv50 of the polymer microsphere composite material is 3.5 μm, and the shell thickness is 1500 nm.

[0244] The preparation method of the polymer microsphere composite material differs from that in Example 2 in that the average diameter of the modified nanocellulose is 50 nm, while the rest is the same as in Example 2.

[0245] Example 16

[0246] The polymer microsphere composite material differs from that in Example 2 in that the average length of the modified nanocellulose is 50 μm, the Dv50 of the polymer microsphere composite material is 2.5 μm, and the shell thickness is 500 nm.

[0247] The preparation method of the polymer microsphere composite material differs from that in Example 2 in that the average length of the modified nanocellulose is 50 μm, while the rest is the same as in Example 2.

[0248] Example 17

[0249] The difference between the polymer microsphere composite material and Example 2 is that the average length of the modified nanocellulose is 3000 μm, the Dv50 of the polymer microsphere composite material is 3.5 μm, and the shell thickness is 1500 nm.

[0250] The preparation method of the polymer microsphere composite material differs from that in Example 2 in that the average length of the modified nanocellulose is 3000 μm, while the rest is the same as in Example 2.

[0251] Example 18

[0252] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 2.5 μm and a shell thickness of 500 nm.

[0253] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that the temperature of the second emulsification treatment is 25°C and the pressure is 10 MPa, while the rest is the same as in Example 2.

[0254] Example 19

[0255] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 3.2 μm and a shell thickness of 1200 nm.

[0256] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that the temperature of the second emulsification treatment is 40°C and the pressure is 30 MPa, while the rest is the same as in Example 2.

[0257] Example 20

[0258] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 2.3 μm and a shell thickness of 300 nm.

[0259] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that the shear stirring speed of the second emulsification treatment is 5000 rpm, while the rest is the same as in Example 2.

[0260] Example 21

[0261] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 3.3 μm and a shell thickness of 1300 nm.

[0262] The preparation method of the polymer microsphere composite material differs from that in Example 2 in that the shear stirring speed of the second emulsification treatment is 15,000 rpm, while the rest is the same as in Example 2.

[0263] Example 22

[0264] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 2.4 μm and a shell thickness of 400 nm.

[0265] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that the second emulsification treatment time is 10 min, while the rest is the same as in Example 2.

[0266] Example 23

[0267] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 3.3 μm and a shell thickness of 1300 nm.

[0268] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that the second emulsification treatment time is 30 min, while the rest is the same as in Example 2.

[0269] Example 24

[0270] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 3.6 μm and a shell thickness of 1600 nm.

[0271] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that, in step 3), modified nanocellulose is added to water, wherein the mass concentration of modified nanocellulose is 0.5 wt%, the pH value of the system is adjusted to 4, and the coating material is obtained. The rest is the same as in Example 2.

[0272] Example 25

[0273] The difference between the polymer microsphere composite material and Example 2 is that the polymer microsphere composite material has a Dv50 of 2.3 μm and a shell thickness of 300 nm.

[0274] The preparation method of the polymer microsphere composite material differs from that of Example 2 in that, in step 3), modified nanocellulose is added to water, wherein the mass concentration of modified nanocellulose is 0.5 wt%, and the pH value of the system is adjusted to 6 to obtain the coating material. The rest is the same as in Example 2.

[0275] Example 26

[0276] The polymer microsphere composite material is the same as in Example 2. A diaphragm is prepared using the above polymer composite microsphere material. The difference from Example 2 is that the polymer composite microsphere material and boehmite (Dv50 = 0.5 μm) are dispersed in deionized water at a mass ratio of 1:9 to prepare a coating. This coating is then applied to a PE diaphragm substrate with a porosity of 40% using a roller coating process to form a coating layer. The thickness of the PE diaphragm substrate is 9 μm, the coating thickness is 0.2 μm, and the areal density of the coating is 0.1 g / m³. 2The membrane with a coating was dried at 70°C, and the rest was the same as in Example 2.

[0277] Example 27

[0278] The polymer microsphere composite material is the same as in Example 2. A diaphragm is prepared using the above polymer composite microsphere material. The difference from Example 2 is that the polymer composite microsphere material and boehmite (Dv50 = 0.5 μm) are dispersed in deionized water at a mass ratio of 10:0 to prepare a coating. This coating is then applied to a PE diaphragm substrate with a porosity of 40% using a roller coating process to form a coating layer. The thickness of the PE diaphragm substrate is 9 μm, the coating thickness is 6 μm, and the areal density of the coating is 5 g / m³. 2 The membrane with a coating was dried at 70°C, and the rest was the same as in Example 2.

[0279] Example 28

[0280] The polymer microsphere composite material differs from that in Example 2 in that the nanocellulose is not modified, but otherwise it is the same as in Example 2.

[0281] Example 29

[0282] The difference between the polymer microsphere composite material and Example 2 is that the hydrophobic group of the modified nanocellulose is an acyl group.

[0283] The preparation method differs from that in Example 2 in that, in step 1), based on the total mass of the added materials as 100%, 50 wt% of nanocellulose raw material and 40 wt% of acetyl chloride are thoroughly mixed in water, stirred at 30°C for 2 hours, washed with deionized water, filtered and dried to obtain modified nanocellulose. The rest is the same as in Example 2.

[0284] Example 30

[0285] The difference between the polymer microsphere composite material and Example 2 is that the hydrophobic group of the modified nanocellulose is an ester group.

[0286] The preparation method differs from that in Example 2 in that, in step 1), based on the total mass of the added materials as 100%, 50 wt% of nanocellulose raw material and 40 wt% of acetic anhydride are thoroughly mixed in water, stirred at 30°C for 2 hours, washed with deionized water, filtered and dried to obtain modified nanocellulose. The rest is the same as in Example 2.

[0287] Example 31

[0288] The difference between the polymer microsphere composite material and Example 2 is that the hydrophobic group of the modified nanocellulose is an isocyanate group.

[0289] The preparation method differs from that in Example 2 in that, in step 1), based on the total mass of the added materials as 100%, 50 wt% of nanocellulose raw material and 40 wt% of octadecyl isocyanate are thoroughly mixed in water, stirred at 30°C for 2 hours, washed with deionized water, filtered and dried to obtain modified nanocellulose, and the rest is the same as in Example 2.

[0290] Comparative Example 1

[0291] The difference from Example 2 is that the diaphragm does not contain polymer microsphere composite material. Specifically, polyvinylidene fluoride (PVDF) with a Dv50 of 2.0 μm is used instead of polymer microsphere composite material. PVDF is coated onto one side of the base membrane using a roller coating method, with a coating thickness of 6 μm and a coating areal density of 5 g / m³. 2 .

[0292] Comparative Example 2

[0293] The difference from Comparative Example 1 is that PVDF and boehmite were blended at a mass ratio of 5:5, and an alumina coating was applied to one side of the base film by roller coating. The coating thickness was 1.5 μm, and the areal density of the coating was 0.8 g / m³. 2 .

[0294] Comparative Example 3

[0295] The difference from Comparative Example 1 is that PVDF and boehmite were blended at a mass ratio of 9:1, and an alumina coating was applied to one side of the base film by roller coating. The coating thickness was 0.2 μm, and the areal density of the coating was 0.1 g / m³. 2 .

[0296] Comparative Example 4

[0297] The difference between this example and Example 2 is that a polymer microsphere mixture is provided, which is a physical mixture of polymer microspheres and modified nanocellulose, and has a non-coated structure.

[0298] The preparation method differs from Example 2 in that, in step 3), modified nanocellulose is added to water at a concentration of 0.08 wt%, and the pH of the system is adjusted to 3.5 to obtain a coating material. The coating material and the oil-in-water emulsion of the polymer microspheres are then added to a high-speed shear dispersion emulsifier, where the modified nanocellulose accounts for 1.9 wt% of the polymer microspheres. A second emulsification treatment is performed. The first emulsification treatment is specifically carried out at 24°C, 9 MPa, and shear-stirred at 4500 rpm for 9 minutes. After washing and filtration, the polymer microsphere mixture is obtained. Other steps are the same as in Example 2.

[0299] Comparative Example 5

[0300] The difference between this example and Example 2 is that a polymer microsphere mixture is provided, which is a physical mixture of polymer microspheres and modified nanocellulose, and has a non-coated structure.

[0301] The preparation method differs from that in Example 2 in that, in step 3), modified nanocellulose is added to water, wherein the mass concentration of modified nanocellulose is 1.1 wt%, and the pH of the system is adjusted to 6.4 to obtain a coating material. The oil-in-water emulsion of the coating material and polymer microspheres is added to a high-speed shear dispersion emulsifier, wherein the modified nanocellulose accounts for 31 wt% of the mass of the polymer microspheres, and a second emulsification treatment is performed. The first emulsification treatment is specifically carried out at 42°C and 32 MPa, with shearing and stirring at 15500 rpm for 32 min. After washing and filtration, a polymer microsphere mixture is obtained, and the rest is the same as in Example 2.

[0302] Comparative Example 6

[0303] The difference between this example and Example 2 is that a polymer microsphere mixture is provided. The polymer microsphere mixture is a physical mixture of polymer microspheres and modified nanocellulose, with a non-coated structure and a mass ratio of polymer microspheres to modified nanocellulose of 8.5:1.5.

[0304] The difference between its preparation method and that of Example 2 is that...

[0305] 1) Based on the total mass of the added materials as 100%, 50 wt% of nanocellulose raw material and 40 wt% of γ-aminopropyltriethoxysilane were thoroughly mixed in 10 wt% water, stirred at 30°C for 2 hours, washed with deionized water, filtered and dried to obtain modified nanocellulose. The modified nanocellulose had an average diameter of 20 nm and an average length of 200 nm.

[0306] 2) 100 parts of polyethylene granules and 0.04 parts of azobisisobutyronitrile were blended at room temperature. The mixture was then fed into a twin-screw extruder, and the extruder temperature was set to 210°C for granulation to obtain polyethylene masterbatch modified with ethyl acrylate. The masterbatch was dried at room temperature under ventilation, and then ground, dispersed, and sieved in liquid nitrogen to obtain polymer granules. The polymer granules were added to dichloromethane to form an oil-phase blend, wherein the mass percentage of polymer granules was 20 wt% based on the mass of dichloromethane. Sodium dodecyl sulfate was added to water to obtain an aqueous-phase blend. The oil-phase blend and the aqueous-phase blend were mixed at a volume ratio of 2:8, wherein the amount of sodium dodecyl sulfate was 5 wt% of the polymer granules. The mixture was then subjected to a first emulsification treatment using a high-speed shear dispersion emulsifier. The first emulsification treatment was carried out at 150°C, 35 MPa, and sheared and stirred at 10,000 rpm for 20 minutes. The mixture was then filtered and dried to obtain polymer microspheres.

[0307] 3) Modified nanocellulose and polymer microspheres were mechanically blended at a mass ratio of 1.5:8.5 to obtain a polymer microsphere mixture. Other steps were the same as in Example 2.

[0308] Comparative Example 7

[0309] The difference between this example and Example 2 is that a polymer microsphere mixture is provided, which is a physical mixture of polymer particles and modified nanocellulose, and has a non-coated structure.

[0310] The preparation method differs from that in Example 2 in that, in step 2), the oil phase blend and the water phase blend are mixed at a volume ratio of 0.5:9.5, and after the first emulsification treatment, an aqueous dispersion containing polymer particles is obtained. The rest is the same as in Example 2.

[0311] Comparative Example 8

[0312] The difference between this example and Example 2 is that a polymer microsphere mixture is provided, which is a physical mixture of polymer particles and modified nanocellulose, and has a non-coated structure.

[0313] The preparation method differs from that in Example 2 in that, in step 2), the oil phase blend and the water phase blend are mixed at a volume ratio of 3.5:6.5, and after the first emulsification treatment, an oil-in-water emulsion containing polymer particles is obtained. The rest is the same as in Example 2.

[0314] Application examples

[0315] The battery is manufactured by including the following steps:

[0316] 1) At a temperature of 20~45°C, graphite, carbon black, sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 100:1:1.6:3.3. Deionized water and N-methylpyrrolidone (NMP) are added and stirred evenly to prepare a negative electrode slurry. This slurry is then coated onto copper foil using a continuous coating device. Normal drying and rolling are then initiated until the compaction density reaches 1.6 g / cm³. 3 Repeat the above operations when brushing the electrode sheet; cut the copper foil graphite sheet of the above negative electrode to a suitable size to form a surface density of 230 g / m³. 2 The negative electrode sheet.

[0317] 2) Lithium iron phosphate, carbon nanotubes (CNTs), carbon black, and PVDF were mixed in a mass ratio of 100:0.3:0.5:2.5, and NMP was added. The mixture was stirred until homogeneous to prepare a positive electrode slurry. This slurry was then simultaneously coated onto aluminum foil using a continuous coating device to obtain the corresponding dimensions and an areal density of 500 g / m². 2 The positive electrode, lithium iron phosphate, is matched with the negative electrode.

[0318] 3) Dissolve 1 mol of lithium salt-LiPF6 in 1 L of organic solvent (the volume ratio of ethylene carbonate to diethyl carbonate is 1:1) to obtain the electrolyte.

[0319] 4) The prepared positive electrode, separator and negative electrode are stacked alternately and injected with electrolyte to assemble a battery with a designed capacity of 120Ah.

[0320] Performance testing

[0321] 1) Wet bond strength: The samples obtained by hot pressing the separator and positive electrode prepared in the examples and comparative examples are immersed in the electrolyte for 12 hours, and then the wet bond peel strength between the separator and the electrode is obtained by testing the 180° peel between the separator and the electrode.

[0322] 2) Diffusion area test: Use a high-precision syringe to draw 20μL of electrolyte and smoothly inject it onto the diaphragm surface, and calculate the electrolyte diffusion area over 3 minutes.

[0323] 3) Core hardness test: The core is preheated at 90℃ for 300s, then hot-pressed at 1.5MPa for 60s. After hot pressing, the maximum bending force at three points of the core is tested. The core that has been hot-pressed is then assembled in the shell or packaged in an aluminum-plastic film. After being immersed in electrolyte for 24h, the core is disassembled and taken out to test the maximum bending force at three points.

[0324] 4) 45℃ Cyclic Test: Under conditions of 45±1℃, the battery is subjected to a charge-discharge cycle test at 1.0C charge and 1.0C discharge. The steps are as follows: rest for 30 minutes; charge at 1.0C constant current to 3.8V, then charge at constant voltage to 0.05C cutoff; rest for 30 minutes; discharge at 1.0C constant current to 2.0V, which constitutes one cycle. Repeat this step and record the number of cycles when the battery capacity retention rate is 85%, which is recorded as the battery's cycle life. Take 5 batteries from each group and take the average value.

[0325] The test results are summarized in Table 2.

[0326] Table 1:

[0327]

[0328] Note: In Table 1, the proportion of polymer composite microspheres is the ratio of polymer composite microspheres to the total of inorganic particles and polymer composite microspheres.

[0329] Table 2:

[0330]

[0331] As shown in Table 2, Comparative Examples 1-3, which did not contain polymer microsphere composite materials and only used PVDF, had poor adhesion and wettability of the separator, resulting in reduced battery cycle performance.

[0332] When the polymer microsphere composite material in Comparative Examples 4-6 was replaced with a physical mixture of polymer microspheres and modified nanocellulose, the adhesion and wettability of the separator were poor, resulting in a decrease in the cycle performance of the battery.

[0333] When the polymer microsphere composite material in Comparative Examples 7-8 was replaced with a physical mixture of polymer particles and modified nanocellulose, the adhesion and wettability of the separator were poor, resulting in reduced battery cycle performance.

[0334] Examples 1-31, by using nanocellulose to coat polyolefin microspheres to form a shell and introducing grafted modified polymers into the polyolefin microspheres, can construct a separator coating with both high adhesion and high wettability, which can improve the cycle performance of the battery.

[0335] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A polymeric microsphere composite material, characterized by, Comprise: Polymer microspheres and a shell provided on the surface of the polymer microspheres, the shell comprising nanocellulose, the polymer microspheres comprising: polyolefin grafted with modified polymer, the modified polymer comprising at least one of acrylate polymer, acrylamide polymer, acrylonitrile polymer, methacrylic polymer, styrene polymer, maleic anhydride polymer.

2. The polymeric microsphere composite of claim 1, wherein, The nanocellulose comprises modified nanocellulose, the modified nanocellulose comprising a hydrophobic group, the hydrophobic group comprising at least one of silane group, acyl group, ester group, isocyanate group.

3. The polymeric microsphere composite of claim 1 or 2, wherein, The particle size Dv50 of the polymer microsphere composite material is 0.1-5.0 microns; And / or, the thickness of the shell is 50-2000 nm; And / or, the nanocellulose satisfies at least one of the following conditions: a. The average diameter of the nanocellulose is ≤50 nm; b. The average length of the nanocellulose is 50-3000 nm; c. The aspect ratio of the nanocellulose is 5-800.

4. The polymeric microsphere composite of claim 3, wherein, The particle size Dv50 of the polymer microsphere composite material is 0.5-2 microns; And / or, the nanocellulose satisfies at least one of the following conditions: a. The average diameter of the nanocellulose is 10-35 nm; b. The average length of the nanocellulose is 200-500 nm; c. The aspect ratio of the nanocellulose is 10-30.

5. The polymeric microsphere composite of claim 1 or 2, wherein, The polyolefin comprises at least one of polyethylene, polypropylene, oxidized polyethylene, polyethylene-polyethylene glycol block copolymer, ethylene-acrylate copolymer, 2-bromoisobutyrate end-functionalized polyethylene, and methylstyrene-terminated polypropylene.

6. The polymeric microsphere composite of claim 1 or 2, wherein, The modified polymer accounts for 2wt%-40wt% of the mass of the polymer microspheres; And / or, the nanocellulose accounts for 2wt%-30wt% of the mass of the polymer microsphere composite material.

7. A method of producing a polymeric microsphere composite material as claimed in any one of claims 1 to 6, characterised in that, Comprise the following steps: Mix the coating material with the oil-in-water emulsion comprising the polymer microspheres, and then perform a second emulsification treatment, during which the coating material is coated on the surface of the polymer microspheres to form the shell, thereby obtaining the polymer composite microsphere material; wherein the coating material comprises the nanocellulose.

8. The preparation method according to claim 7, characterized in that, The preparation process of the oil-in-water emulsion comprising the polymer microspheres comprises: Mix the oil phase blend comprising the organic solvent and the polyolefin grafted with the modified polymer with the water phase blend comprising the emulsifier and water, and then perform a first emulsification treatment to obtain the oil-in-water emulsion of the polymer microspheres; wherein the volume ratio of the oil phase blend is 10%-30% based on the total volume of the oil phase blend and the water phase blend.

9. The production method according to claim 8, characterized by, The preparation process of the polyolefin grafted with the modified polymer comprises: melt extrusion treatment of the mixture material comprising the polyolefin and the modified polymer monomer to obtain the polyolefin grafted with the modified polymer, the temperature of the melt extrusion treatment being 160-220°C; And / or, the emulsifier comprises at least one of fatty alcohol polyoxyethylene ether, isomeric alcohol polyoxyethylene ether, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and Tween; And / or, the first emulsification treatment includes: The pressure of the first emulsification treatment is 20 MPa-50 MPa, And / or, the temperature of the first emulsification treatment is 140℃-160℃, And / or, the first emulsification treatment is carried out under the condition that the shearing stirring speed is 5000 rpm-15000 rpm, And / or, the time of the first emulsification treatment is 10-30 min.

10. The method of any one of claims 7-9, wherein, The process of mixing the coating material with the oil-in-water emulsion including the polymer microspheres includes: Mixing the coating material and water to obtain a dispersion; Mixing the dispersion and the oil-in-water emulsion including the polymer microspheres; And / or, the pH value of the dispersion is 4-6; And / or, the mass concentration of the coating material in the dispersion is 0.1%-1%; And / or, the second emulsification treatment includes: The pressure of the second emulsification treatment is 10 MPa-30 MPa, And / or, the temperature of the second emulsification treatment is 25℃-40℃, And / or, the second emulsification treatment is carried out under the condition that the shearing stirring speed is 5000 rpm-15000 rpm, And / or, the time of the second emulsification treatment is 10-30 min.

11. A diaphragm characterized by, The polymer microsphere composite material prepared by the preparation method of any one of claims 1-6.

12. The diaphragm of claim 11, wherein, The separator includes a base film and a coating layer arranged on at least one side of the base film, and the coating layer includes the polymer microsphere composite material.

13. The diaphragm of claim 12, wherein, The coating layer further includes inorganic particles; the inorganic particles include at least one of perovskite, metal oxide, boehmite, barium sulfate, magnesium hydroxide, aluminum hydroxide, silicon dioxide, and calcium carbonate; And / or, the proportion of the polymer microsphere composite material in the total mass of the polymer microsphere composite material and the inorganic particles is 10%-100%; And / or, the Dv50 of the inorganic particles is 0.1 μm-0.8 μm; And / or, the thickness of the coating layer is 0.2 μm-6 μm; And / or, the areal density of the coating layer is 0.1 g / m²-5 g / m².

14. A battery, characterized by The battery includes a positive electrode sheet, a negative electrode sheet, and the separator of any one of claims 11-13; the separator is arranged between the positive electrode sheet and the negative electrode sheet.

15. An electrical device, characterized by The battery includes the battery of claim 14.

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