Method for preparing polymer, polymer and use, separator, battery, and electrical device

Abstract

Provided are a method for preparing a polymer, a polymer and a use thereof, a separator, a battery, and an electrical device. The method for preparing a polymer comprises: mixing a polymer monomer, an initiator, and an emulsifier to obtain a mixture, wherein the polymer monomer comprises an acrylate monomer, the initiator comprises at least one of a persulfate initiator, an acyl peroxide initiator, and an azo initiator, and the emulsifier comprises an anionic emulsifier; the mixture undergoing a polymerization reaction to obtain a polymer emulsion, wherein the viscosity of the polymer emulsion at 25°C is 100-2000 mPa·s, and the solid content of the polymer emulsion is 20-60%; and granulating the polymer emulsion to obtain the polymer.

Description

Polymer preparation method, polymer and use, diaphragm, battery, electrical device Technical Field

[0001] The present disclosure relates to the field of battery technology, and in particular, to a polymer preparation method, a polymer, a separator, a battery, and an electrical device. Background Art

[0002] In recent years, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. Binders are inactive materials in batteries and are used to bond the components in the battery slurry and adjacent battery parts together. The amount and cost of binders in batteries are very small, but they can effectively improve battery performance. On the premise of meeting the bonding performance, the binder also needs to be able to withstand the swelling and corrosion of the electrolyte, as well as withstand electrochemical corrosion during charging and discharging. Therefore, there are relatively few types of polymers that can be used as battery binders, and polymers that meet the requirements still have problems such as complicated manufacturing processes, low yields, and limited application scenarios. Current polymers and their preparation methods still need to be further improved.

[0003] It should be noted that the above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art.

[0004] Application Contents

[0005] In the first aspect of the present application, a method for preparing a polymer is proposed, comprising: mixing a polymer monomer, an initiator, and an emulsifier to obtain a mixture, wherein the polymer monomer comprises an acrylate monomer; the initiator comprises at least one of a persulfate initiator, an acyl peroxide initiator, and an azo initiator; and the emulsifier comprises an anionic emulsifier; polymerizing the mixture to obtain a polymer emulsion, wherein the viscosity of the polymer emulsion at 25°C is 100mPa·s-2000mPa·s, and the solid content of the polymer emulsion is 20%-60%; and granulating the polymer emulsion to obtain the polymer. Thus, a polymer material with a moderate particle size, suitable for cold pressing, and usable as a battery binder can be prepared by a simple method.

[0006] In some embodiments, mixing the polymer monomer, initiator, and emulsifier includes: mixing the emulsifier with water to obtain a premix; bringing the premix to a first temperature, adding the polymer monomer and the initiator dropwise to the premix, and stirring to obtain the mixture. Thus, premixing can improve the dispersion uniformity of the reaction system, thereby increasing the reaction yield.

[0007] In some embodiments, the mass ratio of the polymer monomer, the initiator, and the emulsifier in the mixture is 100:(0.2-1.2):(1-12). Thus, the yield of the polymer can be improved.

[0008] In some embodiments, the first temperature is 25° C.-95° C. Thus, the dispersion effect of the premix can be improved.

[0009] In some embodiments, the stirring process satisfies at least one of the following conditions: the stirring process time is 10 min to 360 min; the stirring process speed is 10 rpm to 100 rpm. This can further improve the uniformity of the premix.

[0010] In some embodiments, the polymerizing the mixture comprises: subjecting the mixture to a heat-insulating treatment to obtain the polymer emulsion. Thus, the polymer can be obtained through the emulsion polymerization reaction.

[0011] In some embodiments, the heat preservation treatment satisfies at least one of the following conditions: the heat preservation treatment time is 10 min-480 min; the heat preservation treatment temperature is 45° C.-95° C. Thus, the reaction rate and reaction yield of the polymerization reaction can be improved.

[0012] In some embodiments, the granulation process includes a spray drying process, whereby the solid matter in the polymer emulsion can be dried into powder by the spray drying process.

[0013] In some embodiments, the spray drying process includes at least one of centrifugal spray drying, airflow spray drying, and pressure spray drying, thereby improving the yield of the granulation process and the dispersibility of the obtained particles.

[0014] In some embodiments, the centrifugal spray drying method satisfies at least one of the following conditions: an air inlet temperature of 60°C to 280°C; an air outlet temperature of 40°C to 100°C; and an atomizer linear speed of 100 m / s to 500 m / s. This can further improve the yield of the granulation process and effectively control the particle size of the polymer.

[0015] In some embodiments, the airflow spray drying includes at least one of two-fluid spray drying, three-fluid spray drying, and four-fluid spray drying, thereby facilitating the production of polymer particles with smaller particle sizes and improving particle size uniformity.

[0016] In some embodiments, the two-fluid spray drying process satisfies at least one of the following conditions: the air pressure during the two-fluid spray drying process is 0.1 MPa to 5 MPa; and the hydraulic pressure during the two-fluid spray drying process is 0.1 MPa to 100 MPa. This can further improve the particle size uniformity of the polymer particles.

[0017] In some embodiments, the three-fluid spray drying method satisfies at least one of the following conditions: the first air pressure of the three-fluid spray drying method is 0.1 MPa to 5 MPa; the second air pressure of the three-fluid spray drying method is 0.1 MPa to 5 MPa; and the hydraulic pressure of the three-fluid spray drying method is 0.05 MPa to 50 MPa. This can improve the particle size uniformity of the polymer particles.

[0018] In some embodiments, the acrylic acid ester monomer includes at least one of methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, vinyl acetate, trifluoroethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, trimethylolpropane triacrylate, and trimethylaminoethyl methacrylate. Thus, a polymer having a relatively low glass transition temperature can be obtained.

[0019] In some embodiments, the polymer monomer further includes at least one of acrylic acid, methacrylic acid, crotonic acid, heptenoic acid, acrylamide, N-hydroxymethyl acrylamide, N-butoxymethyl acrylamide, acrylonitrile, and methacrylonitrile. This can facilitate the polymerization of the polymer monomer and improve the adhesiveness and ionic conductivity of the polymer.

[0020] In some embodiments, the anionic emulsifier includes at least one of sodium dodecylsulfonate, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfate, sodium laurate, sodium stearate, and sodium palmitoleate. Thus, the polymerization reaction can be carried out in an emulsion system.

[0021] In some embodiments, the initiator satisfies at least one of the following conditions: the persulfate initiator includes at least one of potassium persulfate and ammonium persulfate; the acyl peroxide initiator includes at least one of benzoyl peroxide and dioctanoyl peroxide; and the azo initiator includes at least one of azobisisobutyronitrile and dimethyl azobisisobutyrate. Thus, the initiator can initiate a polymerization reaction of the monomer.

[0022] In some embodiments, the method further comprises drying the polymer, thereby reducing the water content of the polymer.

[0023] In some embodiments, the process further comprises: pulverizing the polymer, thereby obtaining polymer particles with a smaller particle size and a uniform and narrow particle size distribution.

[0024] In some embodiments, the pulverization process includes at least one of air flow milling, mechanical milling, sand milling, and ball milling, thereby obtaining polymer particles with a moderate particle size.

[0025] In some embodiments, the classifying linear velocity of the jet mill is 10 m / s to 80 m / s, thereby improving the pulverization effect of the pulverization process.

[0026] In some embodiments, the pulverizing section of the mechanical mill includes a rotor and a stator, and the pulverizing section satisfies at least one of the following conditions: (1) a gap exists between the rotor and the stator, and the width of the gap is 50 μm-5000 μm; (2) the rotor is a conical structure composed of multiple groups of ceramic modules, the ceramic modules are toothed blade groups, and the angle between the side line and the bottom line of the rotor is 65°-80°; (3) the stator is conical, and the outer surface of the stator is embedded with a serrated ceramic lining, and the angle between the side line and the bottom line of the stator is 65°-80°. In this way, the pulverizing effect of the pulverizing process can be improved.

[0027] In some embodiments, the grinding media of the sand mill includes zirconium oxide beads, and the particle size of the zirconium oxide beads is 0.1 mm to 3 mm. This can improve the pulverization effect of the pulverization process.

[0028] In a second aspect of the present application, a polymer is provided, wherein the polymer is prepared by the aforementioned method. Thus, the polymer has all the features and advantages of the aforementioned method, which will not be described in detail here.

[0029] In some embodiments, the polymer has a Dv50 particle size of 2 μm to 50 μm, which makes it suitable for various application scenarios.

[0030] In some embodiments, the water content of the polymer powder is less than or equal to 3%, which is conducive to long-term storage and use.

[0031] In some embodiments, the polymer has a glass transition temperature of less than or equal to 45° C. Thus, the polymer can exhibit a fluid state at a relatively low temperature.

[0032] In the third aspect of the present application, the present application proposes the use of the polymer prepared by the aforementioned method as a binder. Therefore, when used as a binder, the polymer has all the characteristics and advantages of the aforementioned polymers, which will not be repeated here.

[0033] In a fourth aspect of the present application, a membrane is provided, comprising the aforementioned polymer. Thus, the membrane has all the features and advantages of the aforementioned polymer, which will not be described in detail here.

[0034] In a fifth aspect of the present application, a battery is provided, comprising the aforementioned separator. Thus, the battery has all the features and advantages of the aforementioned separator, which will not be described in detail here.

[0035] In a sixth aspect of the present application, the present application provides an electrical device comprising the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0037] FIG1 is a schematic flow diagram of a method for preparing a polymer according to one embodiment of the present application;

[0038] FIG2 is a schematic flow diagram of a method for preparing a polymer according to another embodiment of the present application;

[0039] FIG3 is a schematic flow diagram of a method for preparing a polymer according to another embodiment of the present application;

[0040] FIG4 is a schematic flow diagram of a method for preparing a polymer according to another embodiment of the present application;

[0041] FIG5 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0042] FIG6 is an exploded view of the battery cell according to one embodiment of the present application shown in FIG5 ;

[0043] FIG7 is a schematic diagram of a battery module according to an embodiment of the present application;

[0044] FIG8 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0045] FIG9 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG8 ;

[0046] FIG10 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0047] Description of reference numerals:

[0048] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell;

[0049] 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0050] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0051] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0052] The terms "include" and "have" in the description and claims of this application and any variations thereof are open expressions, that is, including the contents specified in this application but not excluding other contents.

[0053] " scope " disclosed in the application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0054] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0055] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0056] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the technical features indicated. "First feature" and "second feature" may include one or more of the features.

[0057] In the description of this application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for example, and may be any technical feature connected by "and / or" in this application.

[0058] When the adhesion between the positive and negative electrode plates and the separator is insufficient, gaps can easily form between the battery's plates and separator, significantly increasing the battery's internal resistance and leading to poor battery cycle performance. Applying a binder to the separator surface can improve the poor contact between the separator and the plates. Taking polyvinylidene fluoride (PVDF) binders as an example, due to the pores in the structure of the separator and the plates, when the electrode assembly is pressed through a hot pressing process, the temperature of the hot pressing process exceeds the binder's glass transition temperature, which can cause the binder to be in a relatively soft state and deform with the pressure. As the pressure acts on the binder, parts of the binder can penetrate into the pores of the separator and the plates, bonding the separator and the binder together, creating a mechanical interlocking effect and achieving the bonding function. However, fluorine-containing binders are relatively expensive, which significantly increases the cost of the battery. Furthermore, PVDF binders require a hot pressing process to achieve a tight bond between the separator and the plates, which reduces battery production efficiency and generates additional energy consumption, failing to meet the needs of increasing battery production speed and reducing energy consumption.

[0059] In order to increase the speed and reduce the energy consumption of battery production lines, the hot pressing process is gradually being replaced by the cold pressing process, which uses the original battery process to improve the bonding strength between the electrode and the diaphragm. Specifically, the cold pressing process of battery electrodes refers to the process of shaping the wound battery cells to reduce the elasticity of the battery cells, improve the qualified rate of the core assembly and the consistency of the thickness of the finished battery cells. Since the ambient temperature of the cold pressing process is relatively low, an adhesive with a lower glass transition temperature is required to achieve effective bonding between the electrode and the diaphragm. Acrylic polymers can be used as adhesives in the cold pressing process because of their low glass transition temperature.

[0060] When synthesizing polymer materials through emulsion polymerization, granulation can be used to obtain granular polymer materials. Furthermore, since the particle size of emulsion-type acrylic polymers is 100-200 nm, direct coating onto the diaphragm by scraping can lead to pore blockage or insufficient adhesion due to the small particle size. Granulation can also help obtain polymers with larger particle sizes. When granulating acrylic polymer emulsions, due to the strong intermolecular forces of acrylic polymers, particles often agglomerate, preventing effective granulation.

[0061] In the present application, by optimizing the raw material ratio of the acrylic polymer and the viscosity and solid content of the polymer emulsion, the primary particles in the acrylic polymer emulsion can be granulated to form secondary particle balls through a relatively simple process, thereby obtaining acrylic particles with a moderate particle size and less agglomeration between particles. When the acrylic polymer in the present application is used as a binder on the surface of the diaphragm, the diaphragm has a better affinity for the electrolyte and the electrolyte has better wettability to the diaphragm, that is, the diaphragm has a longer wetting length in the electrolyte, which is more conducive to the transmission of metal active ions and the internal resistance of the battery is smaller. At the same time, the diaphragm and the electrode are more tightly attached, which can reduce polarization loss, extend the cycle life of the battery, and improve the utilization rate of the battery.

[0062] In the first aspect of this application, a method for preparing a polymer is proposed, which can be used to prepare a polymer material with a moderate particle size, suitable for cold pressing, and usable as a battery binder by a simple method. Referring to Figure 1, it includes:

[0063] S100: Mixing polymer monomers, initiators, and emulsifiers

[0064] In some embodiments, in this step, a mixture is obtained by mixing polymer monomers, an initiator, and an emulsifier.

[0065] Emulsifiers are substances that can transform mutually incompatible oil and water into an emulsion that is difficult to separate. Emulsifiers are usually surfactants that have both hydrophilic polar groups and hydrophobic (lipophilic) non-polar groups.

[0066] Initiators are substances that can initiate polymerization reactions of monomers. For example, free radical initiators are compounds that readily decompose into free radicals (i.e., primary free radicals) upon exposure to heat. They can be used to initiate free radical polymerization and copolymerization reactions of olefins and dienes.

[0067] In some embodiments, mixing the polymer monomer, initiator, and emulsifier includes: mixing the emulsifier with water to obtain a premix; allowing the premix to reach a first temperature, adding the polymer monomer and initiator dropwise to the premix, and stirring to obtain a mixture.

[0068] The emulsifier and water are mixed to form an emulsion, that is, the emulsifier forms micelles in the aqueous phase. After the polymer is added, most of the micelles will be solubilized with polymer monomers and initiators, which will help the subsequent emulsion polymerization reaction to occur.

[0069] In some embodiments, the first temperature may be between 25°C and 95°C.

[0070] As an example, the first temperature may be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, or 95°C.

[0071] By adding the polymer monomer and the initiator at the first temperature, the solubilization of the polymer monomer in the micelles is facilitated, thereby improving the efficiency of the polymerization reaction.

[0072] In some embodiments, the stirring process may satisfy at least one of the following conditions: the stirring process time may be 10 min-360 min; the stirring process rotation speed may be 10 rpm-100 rpm.

[0073] In some embodiments, the polymer monomer may include an acrylate monomer. The ester group of the acrylate monomer can improve the anti-swelling ability of the polymer and, as a flexible monomer segment in the molecular chain segment, can adjust the glass transition temperature of the polymer, thereby helping to adjust the glass transition temperature of the polymer within a suitable range.

[0074] In some embodiments, the acrylic acid ester monomer includes at least one of methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, vinyl acetate, trifluoroethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, trimethylolpropane triacrylate, and trimethylaminoethyl methacrylate. Thus, a polymer having a relatively low glass transition temperature can be obtained.

[0075] In some embodiments, the polymer may be a polymer formed by polymerizing one monomer, for example, an acrylate polymer; or a copolymer formed by polymerizing multiple monomers, for example, an acrylate copolymer.

[0076] Copolymer, a polymerization reaction in which two or more monomers participate together is called a copolymerization reaction. The polymer formed contains two or more monomer units. This type of polymer is called a copolymer or an interpolymer.

[0077] Acrylate copolymers are a general term for polymers produced by the copolymerization of acrylate monomers and other comonomers. Acrylate copolymers have good adhesion, and using them improves the bonding between the diaphragm and the electrode after cold pressing.

[0078] As an example, the acrylic ester copolymer may be formed by copolymerizing an acrylic ester monomer and an olefin monomer. For example, the copolymer may include an ethylene-methyl acrylate-glycidyl methacrylate terpolymer.

[0079] In some embodiments, the polymer monomer may further include at least one of acrylic acid, methacrylic acid, crotonic acid, heptenoic acid, acrylamide, N-hydroxymethyl acrylamide, N-butoxymethyl acrylamide, acrylonitrile, and methacrylonitrile.

[0080] The unsaturated carboxyl groups in the polymer monomers are conducive to the polymerization of the monomers, so that in the process of pressing the diaphragm and the electrode using the cold pressing process, the carboxyl groups can form a binding force with the functional groups on the electrode and diaphragm materials, thereby improving the bonding effect.

[0081] The unsaturated amide groups in the polymer monomers can play a role in regulating molecular weight and also have good adhesion.

[0082] The unsaturated cyano group in the polymer monomer helps to improve the ionic conductivity and adhesion of the polymer.

[0083] In some embodiments, the emulsifier may include an anionic emulsifier, wherein the anionic emulsifier may include at least one of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfate, sodium laurate, sodium stearate, and sodium palmitoleate.

[0084] In some embodiments, the initiator may meet at least one of the following conditions: the persulfate initiator includes at least one of potassium persulfate and ammonium persulfate; the acyl peroxide initiator includes at least one of benzoyl peroxide and dioctanoyl peroxide; the azo initiator includes at least one of azobisisobutyronitrile and dimethyl azobisisobutyrate.

[0085] In some embodiments, the mass ratio of the polymer monomer, the initiator, and the emulsifier in the mixture can be 100:(0.2-1.2):(1-12), thereby increasing the yield of the polymer.

[0086] S200: Allow the mixture to polymerize

[0087] In some embodiments, in this step, the mixture is heated so that the initiator initiates emulsion polymerization of the monomers inside the micelles to obtain a polymer emulsion.

[0088] Emulsion polymerization is a process in which monomers are dispersed in water with the help of emulsifiers and mechanical stirring to form an emulsion, and then an initiator is added to initiate monomer polymerization.

[0089] In some embodiments, the viscosity of the polymer emulsion may be 100 mPa·s to 2000 mPa·s, and the solid content of the polymer emulsion may be 20% to 60%.

[0090] As an example, the viscosity of the polymer emulsion can be 100 mPa·s, 150 mPa·s, 200 mPa·s, 250 mPa·s, 300 mPa·s, 350 mPa·s, 400 mPa·s, 450 mPa·s, 500 mPa·s, 550 mPa·s, 600 mPa·s, 650 mPa·s, 700 mPa·s, 750 mPa·s, 800 mPa·s, 850 mPa·s, 900 mPa·s, 950 mPa·s, 1000 mPa·s, 1050 mPa·s. a·s, 1100mPa·s, 1150mPa·s, 1200mPa·s, 1250mPa·s, 1300mPa·s, 1350mPa·s, 1400mPa·s, 1450mPa·s, 1500mPa·s, 155 0mPa·s, 1600mPa·s, 1650mPa·s, 1700mPa·s, 1750mPa·s, 1800mPa·s, 1850mPa·s, 1900mPa·s, 1950mPa·s or 2000mPa·s.

[0091] As an example, the polymer emulsion may have a solids content of 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 60%.

[0092] As an example, the viscosity of the polymer emulsion can be measured using a rotary Brookfield viscometer, specifically, using a 62# rotor, at 25°C.

[0093] When the viscosity and solid content of the polymer emulsion are within the aforementioned ranges, the polymer emulsion is easily ejected during the granulation process, thereby improving the granulation effect. When the viscosity and solid content of the polymer emulsion are outside the aforementioned ranges, the polymer emulsion is difficult to eject, which is not conducive to granulation.

[0094] In some embodiments, in order to meet the process requirements of subsequent granulation treatment, such as spray drying treatment, the polymer emulsion may be subjected to viscosity reduction treatment and / or the solid content of the polymer emulsion may be adjusted before the granulation treatment.

[0095] In some embodiments, allowing the mixture to undergo polymerization reaction includes: performing a heat preservation treatment on the mixture to obtain a polymer emulsion.

[0096] In some embodiments, the heat preservation treatment satisfies at least one of the following conditions: the heat preservation treatment time is 10 min to 480 min; and the heat preservation treatment temperature is 45° C. to 95° C. Thus, the reaction rate and reaction yield of the polymerization reaction can be improved.

[0097] S300: Granulation of polymer emulsion

[0098] In some embodiments, when the polymer material is synthesized by emulsion polymerization, a granulation process is required to obtain a granular polymer material, for example, to obtain a powder of the polymer material.

[0099] In some embodiments, the granulation process may include a spray drying process.

[0100] Spray drying is a granulation process in which a polymer emulsion is sprayed and then dried under thermal influence. Specifically, spray drying involves three stages: atomization of the polymer emulsion, contact of the droplets with hot air, and gas-solid separation. Spray drying process conditions need to be adjusted according to the viscosity and solids content of the polymer emulsion. For example, the appropriate inlet and outlet air temperatures, as well as the spray velocity of the spray device, must be controlled during spray drying to ensure optimal atomization of the polymer emulsion, improve contact and mixing efficiency between the droplets and the hot air, and thus increase the spray drying yield.

[0101] In some embodiments, the spray drying process may include at least one of centrifugal spray drying, air flow spray drying, and pressure spray drying.

[0102] In some embodiments, the centrifugal spray drying can meet at least one of the following conditions: the inlet air temperature of the centrifugal spray drying is 60°C-280°C; the outlet air temperature of the centrifugal spray drying is 40°C-100°C; the atomizer linear speed of the centrifugal spray drying is 100m / s-500m / s.

[0103] Centrifugal spray drying uses a centrifugal atomizer located at the top of the drying tower to atomize the polymer emulsion into fine mist droplets. Relying on the kinetic energy of atomization, the droplets are sprayed into the hot air flow. The water in the mist droplets is instantly vaporized and evaporated, and discharged from the drying tower by the exhaust and dust removal system. The dry powder product falls to the bottom of the tower to obtain the powder of the polymer material.

[0104] When the air inlet temperature of the centrifugal spray drying is within the above range, the solvent residue after volatilization is moderate, and the dried polymer material is not easy to melt or decompose due to absorbing heat from the solvent, resulting in the product sticking to the wall and being unable to collect the material or the product deteriorating. It is also not easy to cause concentration and viscosity due to excessive solvent, and then cause the polymer emulsion to stick to the wall or stick to the wall, resulting in product agglomeration and reduced yield.

[0105] When the outlet air temperature of the centrifugal spray dryer is within the above range, the polymer material in a dry or semi-dry state is not likely to continue to absorb heat due to the lack of solvent protection, causing the polymer material to become coked, melted or decomposed, nor will it stick together into a mass or aggregate and adhere to the bottom of the drying chamber due to being still in a semi-dry state.

[0106] When the linear velocity of the atomizer is within the above range, the amount of solvent that needs to be evaporated and the amount of heat that needs to be absorbed by the mist droplets is moderate, and the mist droplets are less likely to stick to the wall or agglomerate.

[0107] In some embodiments, the airflow spray drying may include at least one of two-fluid spray drying, three-fluid spray drying, and four-fluid spray drying.

[0108] In some embodiments, the two-fluid spray drying process can meet at least one of the following conditions: the air pressure of the two-fluid spray drying process is 0.1 MPa-5 MPa; the hydraulic pressure of the two-fluid spray drying process is 0.1 MPa-100 MPa. This can further improve the particle size uniformity of the polymer particles.

[0109] Two-fluid spray drying refers to the process of passing polymer emulsion and gas through a two-fluid nozzle, using high-speed airflow to spray the liquid to form mist or droplet-shaped liquid particles. The hot air flow in the drying tower instantly vaporizes and evaporates the water, which is then discharged from the drying tower by the exhaust and dust removal system, and the dry powder product falls to the bottom of the tower.

[0110] The working principle of two-fluid spray drying can be divided into two parts: the air flow part and the liquid part. The air flow part refers to the use of compressed air or other gases to accelerate the air flow to a high speed, and then spray it out through the outlet of the nozzle. At the outlet of the nozzle, the air flow will form a high-speed air flow beam, and the air flow beam will spray the polymer emulsion; the liquid part refers to the polymer emulsion passing through the liquid outlet of the nozzle and spraying it into the air flow beam. During this process, the polymer emulsion will be sheared into small particles, forming mist or droplet-shaped droplets.

[0111] In some embodiments, three-fluid spray drying can meet at least one of the following conditions: a first air pressure of 0.1 MPa to 5 MPa; a second air pressure of 0.1 MPa to 5 MPa; and a hydraulic pressure of 0.05 MPa to 50 MPa. This can improve the particle size uniformity of the polymer particles.

[0112] In some embodiments, the principles of three-fluid spray drying, four-fluid spray drying and two-fluid spray drying are similar, except that the nozzle structure is different, that is, the air flow and liquid are mixed at the nozzle outlet through different pipes to form mist-like or droplet-like droplets of the polymer emulsion.

[0113] Since acrylic polymer emulsions themselves have the characteristic of easily absorbing water, when acrylic polymers are coated on the surface of the diaphragm, the moisture in the polymer will cause the internal resistance of the battery to increase, and decompose to produce gas during the charge and discharge cycle, which in turn leads to many defects such as battery bulging. Therefore, the water content in the polymer can be reduced by drying treatment.

[0114] In some embodiments, referring to FIG2 , the method for preparing a polymer may further include:

[0115] S500: Drying of polymers

[0116] In some embodiments, in this step, the water content of the polymer may be reduced by drying.

[0117] In some embodiments, a freezing step can freeze wet materials, such as polymers containing a certain amount of water, into a solid state at a relatively low temperature. The water can then be sublimed directly into a gaseous state under vacuum, bypassing the liquid phase. Pure cold-pressed diaphragm binders have properties such as a low glass transition temperature (Tg) and easy water absorption. To further reduce the binder's water content and facilitate mechanical pulverization and granulation, this solution uses a freezing process to further freeze-dry the spray-dried binder. Controlling the freezing temperature, vacuum level, and time further removes bound and unbound water, while reducing the water content and, consequently, the viscosity of the solid binder.

[0118] In some embodiments, the drying process includes freeze-drying process, and the freeze-drying process satisfies at least one of the following conditions: the temperature of the freeze-drying process can be (-1)°C-(-80)°C; the time of the freeze-drying process can be 2h-50h; the vacuum degree of the freeze-drying process can be 2Pa-45Pa.

[0119] After the granulation treatment of the acrylic polymer emulsion, the obtained polymer material still shows agglomeration and caking phenomena, and when the particle size requirements of the polymer material are high, the agglomeration and caking phenomena in the polymer can be alleviated by pulverization treatment, thereby improving the particle size uniformity of the polymer material.

[0120] In some embodiments, referring to FIG3 , the method for preparing a polymer may further include:

[0121] S400: crushing of polymers

[0122] In some embodiments, in this step, a pulverization process is performed to obtain polymer particles with a smaller particle size and a uniform and narrow particle size distribution.

[0123] In some embodiments, the pulverization process may include at least one of air flow milling, mechanical milling, sand milling, and ball milling.

[0124] In some embodiments, the classifying linear velocity of the jet mill may be 10 m / s to 80 m / s.

[0125] Jet milling involves cooling, filtering, and drying compressed air before injecting it through nozzles into a supersonic jet flow into a grinding chamber, fluidizing the material. Inside the grinding chamber, the accelerated material converges at the intersection of jets from several nozzles, creating intense collisions, friction, and shearing, resulting in ultrafine grinding. Jet milling requires controlling parameters such as grinding pressure, air consumption, and feed size.

[0126] In some embodiments, the crushing part of the mechanical mill can be composed of a rotor and a stator, and the crushing part meets at least one of the following conditions: there is a gap between the rotor and the stator, and the width of the gap is 50μm-5000μm; the rotor is a conical structure composed of multiple groups of ceramic modules, the ceramic modules are toothed knife groups, and the angle between the side line and the bottom line of the rotor is 65°-80°; the stator is conical, and the outer surface of the stator is embedded with a serrated ceramic lining, and the angle between the side line and the bottom line of the stator is 65°-80°.

[0127] The gap width between the rotor and the stator, i.e. the spacing, can be changed by adjusting the number and thickness of the spacers.

[0128] The rotor can be a conical structure composed of three groups of ceramic modules. Specifically, the three groups of ceramic modules constituting the rotor are all toothed knife groups, among which the topmost toothed knife group can be composed of 90 knives to achieve the effect of coarse crushing, and the middle and bottom toothed knife groups can be composed of 120 knives to achieve the effect of fine crushing.

[0129] Mechanical grinding uses a rotating body (such as a hammer, plate, etc.) rotating at supersonic speed around a horizontal or vertical axis to violently impact the material, causing it to collide with a fixed body or with each other, thereby grinding the material. Mechanical grinding requires controlling parameters such as the rotor diameter and speed.

[0130] In some embodiments, the grinding media of the sand mill may include zirconia beads, and the particle size of the zirconia beads may be 0.1 mm to 3 mm.

[0131] Sand milling uses a pump to pump a solid-liquid mixture, pre-dispersed and moistened in a mixer, into a drum. The material and the grinding media within the drum are agitated by a high-speed rotating disperser, creating a more intense collision, friction, and shearing effect between the solid particles and the grinding media, accelerating the grinding of particles and dispersing aggregates. The ground and dispersed material is separated from the grinding media by a dynamic separator and discharged through a discharge pipe.

[0132] Ball milling is a process that uses friction and wear between steel balls and the material in the mill to gradually grind the material to the required particle size. The working process of a ball mill is generally divided into two stages: grinding and grading.

[0133] In some embodiments, referring to FIG. 4 , the polymer may be frozen to a temperature below the glass transition temperature or the brittle temperature by freeze-drying, and then pulverized by pulverizing.

[0134] Under low temperature conditions, the hardness and brittleness of polymers increase, and during the cooling process, uneven shrinkage occurs at various locations inside the polymer, generating internal stress. Under the action of this stress, microcracks appear in weak parts of the polymer and the bonding strength of the internal tissue decreases. Therefore, under a small external force, the internal cracks expand rapidly and break.

[0135] As an example, during the crushing process, liquid nitrogen can be used as a cold source. The temperature of liquid nitrogen can reach (-196)°C, so it can be adjusted according to the brittle point of the polymer. Using liquid nitrogen as a medium can achieve ultra-low temperature crushing, reduce explosion and oxidation, etc.

[0136] Those skilled in the art will understand that, in the specific implementation of the above method, the writing order of each step does not mean a strict execution order, and thus does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic.

[0137] In a second aspect of the present application, a polymer is provided, which is prepared by the aforementioned method. Thus, the polymer has all the features and advantages of the aforementioned method, which will not be described in detail here.

[0138] In some embodiments, the polymer may have a Dv50 particle size of 2 μm to 50 μm.

[0139] As an example, the Dv50 particle size of a polymer can be measured using a laser particle size analyzer (Malvern 3000, MasterSizer 3000) using a helium-neon red light source as the primary light source. Place 1g of the sample to be tested in a clean small beaker, add a drop of surfactant, and add 20ml of deionized water. Ultrasonicate at 53kHz / 120W for 5 minutes to ensure complete dispersion of the sample. Turn on the laser particle size analyzer, clean the optical system, and automatically measure the background. Stir the ultrasonicated solution to ensure uniform dispersion, place it in the sample cell as required, and begin particle size measurement. The measurement results are then read from the instrument.

[0140] In some embodiments, the polymer after the pulverization process may have a Dv50 particle size of 2 μm to 10 μm.

[0141] In some embodiments, the polymer powder has a moisture content of less than or equal to 3%.

[0142] As an example, the test of the moisture content of polymer powder can refer to: "GB / T 2914-2008 Plastics / Determination of volatile matter (including water) of vinyl chloride homopolymer and copolymer resins" Method A / Oven method, sample size 5g.

[0143] In some embodiments, the moisture content of the polymer powder after drying may be less than or equal to 2%.

[0144] In some embodiments, the polymer has a glass transition temperature of less than or equal to 45°C.

[0145] In some embodiments, the glass transition temperature of the polymer may be less than or equal to 35° C. Thus, the polymer may exhibit a fluid state at a relatively low temperature.

[0146] As an example, the glass transition temperature test of a polymer can refer to the following: weigh 6±0.05 mg of sample into an aluminum crucible, shake it flat, and cover it with a lid. The test is performed using a Netzsch DSC 3500 Sirius measuring instrument; the atmosphere is nitrogen, the purge gas rate is 50 mL / min, and the protective gas rate is 100 mL / min; the heating conditions are: the heating rate is 10°C / min, and the temperature range is (-70)°C to 200°C.

[0147] The glass transition temperature (Tg) is the temperature at which a polymer changes from an elastic state to a glassy state. It refers to the transition temperature of an amorphous polymer (including the non-crystalline portion of a crystalline polymer) from the glassy state to the elastic state, or vice versa. It is the lowest temperature at which the macromolecular segments of an amorphous polymer can move freely, and is usually denoted by Tg. Above the Tg, a polymer exhibits elasticity and a certain degree of fluidity; below the Tg, a polymer exhibits brittleness. The Tg can be measured using methods commonly used in the art, such as differential scanning calorimetry (DSC) as described in GB / T 19466.2.

[0148] In the third aspect of the present application, the present application proposes the use of the polymer prepared by the aforementioned method as a binder. Therefore, when used as a binder, the polymer has all the characteristics and advantages of the aforementioned polymers, which will not be repeated here.

[0149] In some embodiments, the aforementioned polymer may serve as a binder on the surface of the base film in the separator.

[0150] In a fourth aspect of the present application, a membrane is provided, comprising the aforementioned polymer. Thus, the membrane has all the features and advantages of the aforementioned polymer, which will not be described in detail here.

[0151] In some embodiments, the separator includes a separator and a bonding layer located at least on one side of the base film, and the bonding layer may contain the aforementioned polymer.

[0152] In some embodiments, when the aforementioned polymer is applied as a binder to the surface of the base film, the polymer becomes non-sticky at a certain temperature, facilitating the winding and unwinding of the separator. However, after being wound with the positive and negative electrode sheets and then subjected to a cold pressing process, the polymer exhibits excellent adhesion, allowing the positive and negative electrode sheets to adhere tightly to each other with the separator. By applying the aforementioned binder to the base film of the separator, the bonding performance between the electrode sheets and the binder can be improved, improving the opening problem of the battery cell pre-cold pressing process, thereby improving the hardness of the electrode assembly and the cycle performance of the battery.

[0153] The present application has no particular limitation on the type of diaphragm, and any porous structure diaphragm with good chemical stability and mechanical stability can be selected.

[0154] In some embodiments, the base membrane is made of at least one of fiberglass, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.

[0155] In a fifth aspect of the present application, a battery is provided, comprising the aforementioned separator. Thus, the battery has all the features and advantages of the aforementioned separator, which will not be described in detail here.

[0156] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts the active ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0157] [Positive electrode]

[0158] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector.

[0159] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0160] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one side of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0161] In some embodiments, when the battery is a lithium ion battery, the positive electrode active material may be a positive electrode active material for lithium ion batteries known in the art.

[0162] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as 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. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. The modified compounds of the above materials may be modified by doping and / or surface coating the materials.

[0163] The battery's charge and discharge processes involve the intercalation and deintercalation of lithium, leading to different molar Li contents at different discharge states. The molar Li contents listed in this application for the positive electrode active materials refer to the initial state of the material, i.e., the state before addition. When the positive electrode active material is used in a battery system, the molar Li content will change after charge and discharge cycles.

[0164] In some embodiments, when the battery is a sodium ion battery, the positive electrode active material may be a positive electrode active material for sodium ion batteries known in the art.

[0165] As an example, the positive electrode active material may include at least one of the following materials: a sodium transition metal oxide, a polyanion compound, a Prussian blue-type sodium compound, and their respective modified compounds. However, this application is not limited to these materials; other conventional materials that can be used as battery positive electrode active materials may also be used. The modified compounds of the above materials may be modified by doping and / or surface coating.

[0166] In some embodiments, the transition metal in the sodium transition metal oxide may be at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu. The chemical formula of the sodium transition metal oxide may satisfy Na xMO2, wherein M includes at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu, and 0<x≤1.

[0167] In some embodiments, the polyanionic compound may be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. Among them, the transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include at least one of P, S, and Si; n represents (YO4) n- valence.

[0168] In some embodiments, the polyanionic compound can also be a compound having sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds of anion units and halogen anions. The transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include at least one of P, S, and Si, and n represents (YO4) n- The halogen may include at least one of F, Cl, and Br.

[0169] In some embodiments, the polyanionic compound may also be a compound having sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. M may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, Y may include at least one of P, S and Si, and n represents (YO4) n- valence state, Z represents a transition metal, m represents (ZO y ) m+ The halogen may include at least one of F, Cl, and Br.

[0170] As an example, the polyanionic compound may satisfy the chemical formula NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' includes at least one of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0171] In some embodiments, the Prussian blue compound may be a compound having sodium ions, transition metal ions and cyanide ions (CN -The transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.

[0172] As an example, a Prussian blue-like compound may satisfy the chemical formula Na a Me b Me' c (CN)6, wherein Me and Me' each independently include at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0<a≤2, 0<b<1, and 0<c<1.

[0173] The battery's charge and discharge processes are accompanied by the deintercalation and consumption of Na, resulting in different molar contents of Na at different discharge states. The molar contents of Na in the positive electrode active materials listed in this application refer to the initial state of the material, i.e., the state before the materials are added. The molar contents of Na will change after the positive electrode active materials are applied to the battery system and undergo charge and discharge cycles.

[0174] In the list of positive electrode active materials in this application, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0175] In some embodiments, the positive active material layer may further optionally include a binder.

[0176] As an example, the binder 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 fluorine-containing acrylate resin.

[0177] In some embodiments, the positive active material layer may further optionally include a conductive agent.

[0178] As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0179] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0180] [Negative electrode]

[0181] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0182] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0183] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0184] In some embodiments, the negative electrode active material may adopt the negative electrode active material for batteries known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials include at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0185] In some embodiments, the negative electrode active material layer may further include a binder. The binder may include at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0186] In some embodiments, the negative electrode active material layer may further include a conductive agent, which includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0187] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0188] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0189] [Electrolytes]

[0190] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0191] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0192] In some embodiments, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0193] In some embodiments, the solvent includes at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0194] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0195] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0196] In some embodiments, the battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0197] In some embodiments, the battery outer packaging may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the battery outer packaging may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0198] The present application has no particular limitation on the shape of the battery, which can be cylindrical, square, or any other shape. For example, FIG5 shows a battery cell 5 with a square structure as an example.

[0199] In some embodiments, referring to Figure 6, the outer packaging may include a shell 51 and a top cover assembly 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the diaphragm can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0200] In some embodiments, batteries may be assembled into a battery module. The number of batteries contained in the battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0201] Figure 7 shows an example battery module 4. Referring to Figure 7 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0202] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0203] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0204] Figures 8 and 9 illustrate an example battery pack 1. Referring to Figures 8 and 9 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0205] In a sixth aspect of the present application, the present application provides an electrical device comprising the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be described in detail here.

[0206] Batteries, battery modules, or battery packs can be used as power sources or energy storage units for electrical devices. Electrical devices may include, but are not limited to, mobile devices (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, satellites, and energy storage systems.

[0207] As an electrical device, a battery, battery module or battery pack can be selected according to its usage requirements.

[0208] Figure 10 shows an example of an electric device. This device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery, a battery pack or battery module can be used.

[0209] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0210] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0211] Example 1

[0212] emulsion synthesis

[0213] The monomers include: 65 wt% n-butyl acrylate, 5 wt% trimethylolpropane triacrylate, 2 wt% acrylic acid, 3 wt% 2-hydroxyethyl acrylate, 20 wt% acrylonitrile, and 5 wt% acrylamide; the initiator is ammonium persulfate; and the emulsifier is sodium lauryl sulfate. The mass ratio of the monomers, initiator, and emulsifier is 100:1:1.

[0214] All emulsifiers, 30% of the total monomer weight, and 30% of the total initiator weight were added to a reactor, and water was added with stirring at 30 rpm. After stirring at room temperature for 1 hour, the temperature was raised to 60°C over 1 hour. Maintaining the stirring speed at 30 rpm, the remaining monomers and initiator were added to the reactor at a constant rate over 3 hours. After the additions were completed, the reaction mixture was incubated for 4 hours and the pH was adjusted to 5-8 to obtain a polymer emulsion having a viscosity of 1500 mPa·s at 25°C. The weight ratio of water to other components in the polymer emulsion was 50:50, and the solids content of the polymer emulsion was 50%.

[0215] Centrifugal spray drying

[0216] The polymer emulsion was transferred to a centrifugal spray buffer stirring tank at 60 rpm and stirred for 2 hours to complete the batching. The spray dryer was turned on and set to an inlet air temperature of 200°C, an outlet air temperature of 80°C, and an atomizer speed of 15,000 rpm (atomizing disk diameter of 180 mm, corresponding to a linear velocity of 141 m / s). After stabilization, the feed pump was turned on at a feed rate of 2,000 kg / h. The slurry was dried in the centrifugal spray dryer to obtain a polymer powder.

[0217] Example 2

[0218] Example 2 is consistent with Example 1, except that the polymer powder in Example 1 is conveyed to the hopper of the air flow mill, the air flow mill is turned on, the grinding gas pressure is adjusted to 5 bar, the classifying wheel linear speed is 38.6 m / s (classifying wheel diameter 315, rotation speed 3000 rpm), and the material is collected by a dust collector to obtain a crushed polymer.

[0219] Example 3

[0220] The difference between Example 3 and Example 1 is that the monomers in Example 3 include: 40 wt% of methyl methacrylate, 40 wt% of lauryl methacrylate, 3 wt% of acrylic acid, 2 wt% of 2-hydroxyethyl acrylate, 5 wt% of trimethylolpropane triacrylate, and 20 wt% of acrylonitrile, and the viscosity of the polymer emulsion at 25°C is 100 mPa·s.

[0221] Example 4

[0222] The difference between Example 4 and Example 1 is that the monomers in Example 4 include: 60 wt% of n-butyl acrylate, 5 wt% of trimethylolpropane triacrylate, 2 wt% of acrylic acid, 8 wt% of 2-hydroxyethyl acrylate, and 25 wt% of acrylonitrile, and the viscosity of the polymer emulsion at 25°C is 1000 mPa·s.

[0223] Example 5

[0224] The difference between Example 5 and Example 1 is that the monomers in Example 5 include: 60 wt% of n-butyl acrylate, 5 wt% of trimethylolpropane triacrylate, 2 wt% of acrylic acid, 8 wt% of 2-hydroxyethyl acrylate, 15 wt% of acrylonitrile, and 10 wt% of acrylamide, and the viscosity of the polymer emulsion at 25°C is 2000 mPa·s.

[0225] Example 6

[0226] The difference between Example 6 and Example 1 is that in Example 6, the weight ratio of water to other components in the polymer emulsion is 80:20, and the solid content of the polymer emulsion is 20%.

[0227] Example 7

[0228] The difference between Example 7 and Example 1 is that in Example 7, the weight ratio of water to other components in the polymer emulsion is 60:40, and the solid content of the polymer emulsion is 40%.

[0229] Example 8

[0230] The difference between Example 8 and Example 1 is that in Example 8, the weight ratio of water to other components in the polymer emulsion is 40:60, and the solid content of the polymer emulsion is 60%.

[0231] Comparative Example 1

[0232] The difference between Comparative Example 1 and Example 1 is that the monomers in Comparative Example 1 include: 55 wt% ethyl acrylate, 5 wt% trimethylolpropane triacrylate, 40 wt% acrylonitrile, and the viscosity of the polymer emulsion at 25°C is 80 mPa·s.

[0233] Comparative Example 2

[0234] The difference between Comparative Example 2 and Example 1 is that the monomers in Comparative Example 2 include: 55 wt% ethyl acrylate, 5 wt% trimethylolpropane triacrylate, 20 wt% acrylonitrile, and 20 wt% acrylamide, and the viscosity of the polymer emulsion at 25°C is 2100 mPa·s.

[0235] Comparative Example 3

[0236] The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, the ratio of water to other ingredients is 82:18, and the solid content of the polymer emulsion is 18%.

[0237] Comparative Example 4

[0238] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 4, the ratio of water to other ingredients is 39:61, and the solid content of the polymer emulsion is 61%.

[0239] The polymers in Examples 1-8 and Comparative Examples 1-4 were placed on a separator and assembled into a battery, as follows:

[0240] Preparation of diaphragm

[0241] A commercially available PE microporous film with a thickness of 7 μm and an average pore size of 80 nm (from Zhuo Gao Electronic Technology Co., Ltd.) was used as the base film. The polymer prepared above was stirred and mixed uniformly in deionized water to obtain a slurry (solid content of 20%). The slurry was sprayed onto both surfaces of the substrate and dried to remove the solvent. The coating density of the coating composition on the substrate was 1.5 g / m 2 , and obtain a diaphragm.

[0242] Preparation of positive electrode

[0243] Polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive carbon black, and N-methylpyrrolidone (NMP) were mixed in a mass ratio of 1.2:58.38:0.42:40 and stirred thoroughly to prepare a positive electrode slurry. 2 The loading amount is evenly coated on the positive electrode current collector aluminum foil, and then dried, cold pressed and cut to obtain the positive electrode sheet.

[0244] Preparation of negative electrode sheet

[0245] Artificial graphite, conductive agent acetylene black, binder styrene butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na) were added into deionized water in a mass ratio of 96.2:1.0:1.6:1.2, and stirred thoroughly to prepare negative electrode slurry. 2 The loading amount is coated on the negative electrode current collector copper foil, and then dried, cold pressed and cut to obtain the negative electrode sheet.

[0246] Preparation of electrolyte

[0247] At 25°C, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent, and then LiPF6 is dissolved in the above mixed solvent to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0248] Battery preparation

[0249] The positive electrode sheets, separators, and negative electrode sheets are stacked in sequence, wound, and cold-pressed (during which the separators and the electrodes are bonded) to obtain a battery cell; the battery cell is placed in an outer package, and the above-prepared electrolyte is added. After packaging, standing, formation, aging, and other processes, a secondary battery is obtained.

[0250] The following tests were performed on the polymers, separators, and batteries in Examples 1-8 and Comparative Examples 1-4. The test results are shown in Table 1:

[0251] Test method:

[0252] 1. Viscosity of polymer emulsion: tested using a rotary Brookfield viscometer, specifically, using a 62# rotor at 25°C.

[0253] 2. Solid content of polymer emulsion: The solid content was tested using a halogen moisture meter (Mettler HE 53) with a sample size of 1 g and a temperature of 120°C.

[0254] 3. Glass transition temperature Tg test of polymer

[0255] 6 ± 0.05 mg of sample was weighed into an Al crucible, shaken flat, and covered with a lid. The crucible was tested using a Netzsch DSC 3500 Sirius measuring instrument. The atmosphere was nitrogen, the purge gas rate was 50 mL / min, and the shielding gas rate was 100 mL / min. The heating conditions were: a heating rate of 10°C / min, and a temperature range of -70 to 200°C.

[0256] 4. Polymer particle size test

[0257] The analysis was performed using a laser particle size analyzer (Malvern 3000, MasterSizer 3000) using a helium-neon red light source as the primary light source. In a clean small beaker, add 1g of the sample to be tested, a drop of surfactant, and 20ml of deionized water. Ultrasonication was performed at 53kHz / 120W for 5 minutes to ensure complete dispersion of the sample. The laser particle size analyzer was turned on, the optical system was cleaned, and the background was automatically measured. The ultrasonicated sample solution was stirred to ensure uniform dispersion, then placed in the sample cell as required, and the particle size measurement was started. The measurement results were then read from the instrument.

[0258] 5. Moisture content of polymer powder: refer to GB / T 2914-2008 Plastics / Determination of volatile matter (including water) of vinyl chloride homopolymer and copolymer resins Method A / Oven method, sample size is 5g.

[0259] 6. Diaphragm wetted length:

[0260] The diaphragm was cut into samples with a width of 5 mm and a length of 100 mm. The two ends of the sample were fixed and placed horizontally. 0.5 mg of electrolyte was dropped in the center of the sample. After 1 minute, a photo was taken and the length of the electrolyte diffusion was measured to obtain the wetting length of the diaphragm. In order to ensure the accuracy of the test results, 10 samples were taken for testing, and the test results were obtained by calculating the average value. The electrolyte can be prepared as follows: ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a mass ratio of 30:50:20 to obtain an organic solvent, and fully dried LiPF6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0261] 7. Battery cycle performance: At 25 ° C, the prepared battery was charged at a constant current of 1 / 3C to 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C, left for 5 minutes, and then discharged at 1 / 3C to 2.0V. The obtained discharge capacity was recorded as the initial capacity C0. Repeat the above steps for the same battery and record the discharge capacity C of the battery after the nth cycle. n , then the battery capacity retention rate P after each cycle n =C n / C0×100%, using the battery capacity retention rate P under 500 cycles 500 Characterize the cycle performance.

[0262] Table 1

[0263] As can be seen from Table 1, the viscosity of the polymer emulsion in Comparative Example 1 is too low, the glass transition temperature of the obtained polymer is too low, the electrolyte resistance is poor, and the bonding stability of the bonding coating formed by the polymer on the surface of the base film is poor, resulting in poor battery cycle performance; the viscosity of the polymer emulsion in Comparative Example 2 is too large, the Dv50 diameter of the obtained polymer is too large, the bonding coating formed by the polymer on the surface of the base film is too thick, and the electrolyte wettability of the diaphragm is poor, resulting in poor battery cycle performance; the solid content of the polymer emulsion in Comparative Example 3 is too low, the production energy consumption increases, and the water content of the powder of the obtained polymer powder is too high, the polymer is easy to agglomerate, and the coating quality of the bonding coating formed by the polymer on the surface of the base film is poor, resulting in poor bonding stability of the bonding coating and poor battery cycle performance; the solid content of the polymer emulsion in Comparative Example 4 is too high, the Dv50 diameter of the obtained polymer is too large, the bonding coating formed by the polymer on the surface of the base film is too thick, and the electrolyte wettability of the diaphragm is poor, resulting in poor battery cycle performance.

[0264] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a polymer, wherein: include: Mixing a polymer monomer, an initiator, and an emulsifier to obtain a mixture, wherein the polymer monomer includes an acrylate monomer; the initiator includes at least one of a persulfate initiator, an acyl peroxide initiator, and an azo initiator; and the emulsifier includes an anionic emulsifier; Allowing the mixture to undergo a polymerization reaction to obtain a polymer emulsion, wherein the viscosity of the polymer emulsion at 25° C. is 100 mPa·s-2000 mPa·s, and the solid content of the polymer emulsion is 20%-60%; The polymer emulsion is granulated to obtain the polymer.

2. The method according to claim 1, wherein: The mixing of the polymer monomer, the initiator and the emulsifier comprises: mixing the emulsifier with water to obtain a premix; The premix is ​​kept at a first temperature, and the polymer monomer and the initiator are added dropwise into the premix, and stirred to obtain the mixture; Optionally, the mass ratio of the polymer monomer, the initiator and the emulsifier in the mixture is 100:(0.2-1.2):(1-12).

3. The method according to claim 2, wherein: The first temperature is 25°C-95°C.

4. The method according to claim 2 or 3, wherein: The stirring process satisfies at least one of the following conditions: The stirring time is 10min-360min; The rotation speed of the stirring process is 10 rpm-100 rpm.

5. The method according to any one of claims 1 to 4, wherein: The step of causing the mixture to undergo a polymerization reaction comprises: The mixture is subjected to a heat preservation treatment to obtain the polymer emulsion.

6. The method according to claim 5, wherein: The heat preservation treatment satisfies at least one of the following conditions: The heat preservation treatment time is 10min-480min; The temperature of the heat preservation treatment is 45°C-95°C.

7. The method according to any one of claims 1 to 6, wherein: The granulation process includes a spray drying process.

8. The method according to claim 7, wherein: The spray drying process includes at least one of centrifugal spray drying, air flow spray drying, and pressure spray drying.

9. The method according to claim 8, wherein: The centrifugal spray drying satisfies at least one of the following conditions: The inlet air temperature of the centrifugal spray drying is 60°C-280°C; The outlet air temperature of the centrifugal spray drying is 40°C-100°C; The linear speed of the atomizer of the centrifugal spray drying is 100m / s-500m / s.

10. The method according to claim 8, wherein: The airflow spray drying includes at least one of two-fluid spray drying, three-fluid spray drying, and four-fluid spray drying.

11. The method according to claim 10, wherein: The two-fluid spray drying satisfies at least one of the following conditions: The air pressure of the two-fluid spray drying is 0.1MPa-5MPa; The hydraulic pressure of the two-fluid spray drying is 0.1 MPa-100 MPa.

12. The method according to claim 10, wherein: The three-fluid spray drying satisfies at least one of the following conditions: The first gas pressure of the three-fluid spray drying is 0.1MPa-5MPa; The second gas pressure of the three-fluid spray drying is 0.1MPa-5MPa; The hydraulic pressure of the three-fluid spray drying is 0.05 MPa-50 MPa.

13. The method according to any one of claims 1 to 12, wherein: The initiator satisfies at least one of the following conditions: The persulfate initiator includes at least one of potassium persulfate and ammonium persulfate; The acyl peroxide initiator comprises: at least one of benzoyl peroxide and dioctanoyl peroxide; The azo initiator includes at least one of azobisisobutyronitrile and dimethyl azobisisobutyrate.

14. The method according to any one of claims 1 to 13, wherein: The acrylic acid ester monomers include at least one of methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, vinyl acetate, trifluoroethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, trimethylolpropane triacrylate, and trimethylamineethyl methacrylate.

15. The method according to any one of claims 1 to 14, wherein: The polymer monomer further includes at least one of acrylic acid, methacrylic acid, crotonic acid, heptenoic acid, acrylamide, N-hydroxymethyl acrylamide and N-butoxymethyl acrylamide, acrylonitrile and methacrylonitrile.

16. The method according to any one of claims 1 to 15, wherein: The anionic emulsifier includes at least one of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfate, sodium laurate, sodium stearate, and sodium palmitoleate.

17. The method according to any one of claims 1 to 16, wherein: Further including: The polymer is dried.

18. The method according to any one of claims 1 to 17, wherein: Further including: The polymer is subjected to a pulverization treatment.

19. The method according to claim 18, wherein: The pulverizing process includes at least one of air flow milling, mechanical milling, sand milling and ball milling.

20. The method according to claim 19, wherein: The classification linear speed of the air flow mill is 10m / s-80m / s.

21. The method according to claim 19, wherein: The pulverizing part of the mechanical mill includes a rotor and a stator, and the pulverizing part satisfies at least one of the following conditions: (1) There is a gap between the rotor and the stator, and the width of the gap is 50 μm-5000 μm; (2) The rotor is a conical structure composed of multiple groups of ceramic modules, the ceramic modules are toothed blade groups, and the angle between the side line and the bottom line of the rotor is 65°-80°; (3) The stator is conical, and a serrated ceramic lining is embedded on the outer surface of the stator. The angle between the side line and the bottom line of the stator is 65°-80°.

22. The method according to claim 19, wherein: The grinding media of the sand mill includes zirconium oxide beads, and the particle size of the zirconium oxide beads is 0.1 mm-3 mm.

23. A polymer, wherein The polymer is prepared by the method according to any one of claims 1 to 22.

24. The polymer according to claim 23, wherein The Dv50 particle size of the polymer is 2 μm-50 μm.

25. The polymer according to claim 23 or 24, wherein The water content of the polymer powder is less than or equal to 3%.

26. The polymer according to any one of claims 23 to 25, wherein The polymer has a glass transition temperature of less than or equal to 45°C.

27. Use of a polymer prepared by the method according to any one of claims 1 to 22 as a binder.

28. A diaphragm, wherein: Comprising the polymer described in any one of claims 23-26.

29. A battery, wherein: Comprising the diaphragm of claim 28.

30. An electrical device, wherein: Comprising the battery of claim 29.

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