Polymer, separator, battery, and electric device

Abstract

The present invention provides a polymer, a separator, a battery, and an electric device. The polymer comprises a first polymer and a second polymer, the Dv50 particle size of the first polymer is greater than the Dv50 particle size of the second polymer, and the first polymer comprises an acrylate copolymer.

Description

Polymers, separators, batteries, and electrical devices Technical Field

[0001] The present disclosure relates to the field of battery technology, and in particular, to 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. The battery includes a positive electrode plate, a negative electrode plate and a separator. As an inactive material in the battery, the binder can bond the various components in the battery, as well as adjacent components together. For example, by providing an adhesive layer on the surface of the separator, it helps to closely bond the separator and the plate through the adhesive. The bonded positive electrode plate, negative electrode plate and separator are adhered to each other and support each other to form a structure with a certain thickness, so that the battery has a certain hardness. However, the polymer binders currently used in separators still have many problems in actual application and 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 a first aspect of the present application, a polymer is provided, comprising: a first polymer and a second polymer, wherein the first polymer has a larger Dv50 particle size than the second polymer, and the first polymer comprises an acrylic copolymer. Thus, by compounding the large-particle-size first polymer with the small-particle-size second polymer, the polymers exhibit superior bonding properties when used as adhesives on separators.

[0006] In some embodiments, the monomers of the acrylic copolymer include a first monomer, a second monomer, and a third monomer, and the monomers of the acrylic copolymer meet at least one of the following conditions: the first monomer includes ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, methacrylate At least one of isobornyl, lauryl methacrylate, vinyl acetate, trifluoroethyl methacrylate, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate; the second monomer includes at least one of acrylonitrile, methacrylonitrile, ethacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, heptenoic acid, itaconic acid, and maleic acid; and the third monomer includes at least one of acrylamide, N-hydroxymethyl acrylamide, and N-butoxymethyl acrylamide. This can lower the glass transition temperature of the first polymer, making it suitable for cold pressing.

[0007] In some embodiments, the monomers of the acrylic copolymer meet at least one of the following conditions: the first monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, isooctyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and isobornyl methacrylate; the second monomer includes at least one of acrylonitrile, methacrylonitrile, acrylic acid, and methacrylic acid; and the third monomer includes at least one of acrylamide and N-methylol acrylamide. This can lower the glass transition temperature of the first polymer, making it suitable for cold pressing.

[0008] In some embodiments, the second polymer comprises an acrylic acid ester copolymer. Thus, the first polymer and the second polymer are both acrylic acid ester copolymers, and the compatibility between the two is good, and the polymers have better bonding properties.

[0009] In some embodiments, the Dv50 particle size of the first polymer is 6 μm-12 μm, and the Dv50 particle size of the second polymer is 0.8 μm-1.5 μm. Thus, the compounding effect of the first polymer and the second polymer is better.

[0010] In some embodiments, the storage modulus of the polymer is 100 MPa-800 MPa, thereby reducing stress rebound of the polymer after pressure is applied.

[0011] In some embodiments, the second polymer includes at least one of a polyvinyl fluoride polymer and a polyvinylidene fluoride polymer, thereby improving the high temperature resistance of the polymer.

[0012] In some embodiments, the polyvinyl fluoride polymer includes at least one of polytetrafluoroethylene, polychlorotrifluoroethylene, and polyvinyl fluoride; and / or the polyvinylidene fluoride polymer includes at least one of polyvinylidene fluoride, a vinylidene fluoride-trifluoroethylene copolymer, a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-trifluoroethylene-hexafluoropropylene copolymer, a vinylidene fluoride-hexafluoropropylene-acrylic acid copolymer, and a vinylidene fluoride-hexafluoropropylene-acrylate copolymer. This can further improve the high-temperature resistance of the polymer.

[0013] In some embodiments, the polyvinylidene fluoride polymer includes at least one of polyvinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymer, thereby further improving the high temperature resistance of the polymer.

[0014] In some embodiments, the Dv50 particle size of the first polymer is 5 μm-10 μm, and the Dv50 particle size of the second polymer is 0.5 μm-4 μm. Thus, the high temperature resistance of the polymer can be improved.

[0015] In some embodiments, the storage modulus of the polymer is 300 MPa-1500 MPa, thereby reducing stress rebound of the polymer after pressure is applied.

[0016] In some embodiments, the mass fraction of the first polymer in the polymer is 50%-90%, and the mass fraction of the second polymer in the polymer is 10%-50%. Thus, the first polymer and the second polymer can jointly improve the adhesion of the polymer.

[0017] In a second aspect of the present application, the present application provides an isolation membrane comprising the aforementioned polymer. Thus, the isolation membrane has all the characteristics and advantages of the aforementioned polymer, which will not be described in detail here.

[0018] In a third aspect of the present application, a battery is provided, comprising the aforementioned separator, thereby having all the features and advantages of the aforementioned separator, which will not be described in detail here.

[0019] In a fourth 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

[0020] 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:

[0021] FIG1 is a schematic structural diagram of a battery according to one embodiment of the present application;

[0022] FIG2 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0023] FIG3 is an exploded view of the battery cell according to one embodiment of the present application shown in FIG2 ;

[0024] FIG4 is a schematic diagram of a battery module according to an embodiment of the present application;

[0025] FIG5 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0026] FIG6 is an exploded view of the battery pack shown in FIG5 according to an embodiment of the present application;

[0027] FIG7 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0028] Explanation of the reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 11 negative electrode current collector; 12 negative electrode active material layer; 21 positive electrode current collector; 22 positive electrode active material layer; 31 base film; 32 polymer; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present application in detail. Examples of the embodiments are shown in the accompanying drawings, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary lengthiness in the following description and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0030] 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).

[0031] 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.

[0032] In the description of this application, regardless of whether the word "about" or "approximately" is used, all numbers disclosed herein are approximate values. The value of each number may vary by less than 10% or by a reasonable difference considered by a person skilled in the art, such as 1%, 2%, 3%, 4% or 5%.

[0033] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] In the description of this application, "same chemical composition" should be understood in a broad sense, that is, the main components of the two have the same chemical composition, or the chemical composition of the two is basically the same, and may have errors within the allowable range in the field that are understandable to those skilled in the art or contain impurities within the allowable range.

[0039] In this application, the writing order of each step does not mean a strict execution order and 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. Unless otherwise specified, all steps of this application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), indicating that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0040] Typically, a battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the battery's charge and discharge process, active ions are embedded and released back and forth between the positive and negative electrode sheets. The electrolyte conducts active ions between the positive and negative electrode sheets. The separator is arranged between the positive and negative electrode sheets, mainly to prevent the positive and negative electrodes of the battery from short-circuiting, while allowing ions to pass through. The negative electrode sheet will expand and contract in volume during the battery's charge and discharge process. When the bonding force between the separator and the sheet is weak, gaps will form between the positive and negative electrode sheets and the separator due to expansion and contraction, resulting in the positive and negative electrode sheets and the separator being unable to adhere to and support each other, ultimately causing the battery to become loose, the hardness to decrease, and the internal resistance to increase significantly, which in turn leads to a significant reduction in the battery's cycle performance. Therefore, improving the bonding effect between the separator and the sheet is critical to improving the battery's cycle performance.

[0041] The polymer binders currently used in isolation membranes typically have a unimodal particle size distribution. Polymer binders with a unimodal particle size distribution have a narrow particle size distribution, and the polymer particles are relatively close in size, resulting in a large number of unfilled gaps between the polymer particles. The packing density of the polymer particles is low, and the number of contact sites per unit area cannot be effectively increased, resulting in poor polymer bonding performance. In addition, there may be a problem of too few contact sites due to the small particle size of the polymer particles, and stress rebound after pressure is applied due to the large particle size of the polymer particles. Stress rebound can cause gaps to form between the isolation membrane and the adjacent electrode, or even complete separation, resulting in a significant decrease in the number of effective contact sites per unit area and a decrease in bonding performance.

[0042] Acrylate copolymers have a low glass transition temperature and are suitable for cold pressing. To provide a certain level of structural strength and good intercalation between the electrode and the substrate, the particles of the acrylic copolymer used must be larger. However, excessively large particle sizes result in fewer contact points per unit area, preventing further improvement in bonding performance.

[0043] In the present application, an acrylic polymer is used as the first polymer. The acrylic polymer has excellent bonding properties, low manufacturing costs and good electrolyte wettability. By compounding a first polymer with a larger particle size with a second polymer with a smaller particle size, the second polymer can fully fill the gaps between the first polymers, so that the polymer reaches the maximum packing density. When the aforementioned polymer is used as a binder on the isolation membrane, for example, when used as a binder on the surface of the base film, the number of effective contact sites per unit area can be increased during the pressure bonding process between the electrode and the isolation membrane, and the generation of holes that do not form effective contact can be reduced. The binder on the isolation membrane can better infiltrate the surface structure of the electrode, and a mechanical chain effect occurs between the isolation membrane and the electrode, so that the polymer as a whole achieves a better embedding effect. At the same time, the second polymer that fills the gaps between the first polymers can also reduce the stress rebound of the polymer as a whole after pressure is applied, so that the bonding effect after pressure is maintained, and the battery also has higher hardness and large clamp cycle performance.

[0044] The hardness of the battery is affected by the bonding force between the isolation membrane and the electrode. Specifically, if the bonding force between the isolation membrane and the electrode is good and no rebound occurs, the overall hardness of the battery is good; if the bonding force between the isolation membrane and the electrode is poor, the adhesive on the isolation membrane cannot be well embedded with the electrode, and the battery will exhibit problems such as soft cells and openings.

[0045] The large-clamp cycle performance of the battery is also affected by the bonding force between the isolation membrane and the electrode. Specifically, during the transmission of lithium ions, the electrode will undergo cyclic expansion. When the bonding force between the isolation membrane and the electrode is better, the fit between the electrode and the isolation membrane will be more stable, reducing the occurrence of adverse phenomena such as the separation membrane and the electrode falling off, and maintaining the stability of lithium ion transmission. When the bonding force between the isolation membrane and the electrode is poor, the cycle performance of the battery will deteriorate.

[0046] Cold pressing is a process that shapes wound battery cells at a lower temperature than hot pressing. This reduces cell elasticity, improves assembly yield, and improves the thickness consistency of finished cells. Compared to hot pressing, cold pressing offers greater process consistency and production efficiency.

[0047] In some embodiments, the first polymer and the second polymer can both be acrylic polymers. In this case, the materials of the first polymer and the second polymer are the same or similar, and the Dv50 particle size of the second polymer is smaller than the Dv50 particle size of the first polymer, that is, the particle sizes of the first polymer and the second polymer are different.

[0048] In some embodiments, the first polymer can be an acrylic copolymer, and the Dv50 particle size of the acrylic copolymer is larger. The second polymer can be a polyvinyl fluoride polymer and / or a polyvinylidene fluoride polymer, and the Dv50 particle size of the polyvinyl fluoride polymer and the polyvinylidene fluoride polymer is smaller. At this time, the particle size of the second polymer is smaller than the particle size of the first polymer, that is, the particle size and material of the first polymer and the second polymer are different.

[0049] The swelling of the polymer will lead to problems such as increased volume expansion and electrode pulverization during the battery charging and discharging process, further causing the AC impedance of the electrode to increase, the reversible capacity to decay faster, and the cycle stability to deteriorate.

[0050] In some embodiments, the isolation film may include a base film and a polymer located on at least one side of the base film; in other embodiments, the polymer may be located on two opposite surfaces of the base film.

[0051] In a first aspect of the present application, a polymer is provided, comprising: a first polymer and a second polymer, wherein the first polymer has a larger Dv50 particle size than the second polymer, and the first polymer comprises an acrylic copolymer. When used as a binder on a separator, the large-particle-size first polymer is compounded with the small-particle-size second polymer. The small-particle-size second polymer fills the gaps between the large-particle-size first polymer, thereby increasing the number of contact points per unit area between the polymers and adjacent structures, achieving a superior bonding effect.

[0052] In some embodiments, the monomers of the acrylic copolymer include a first monomer, a second monomer, and a third monomer, thereby lowering the glass transition temperature of the first polymer, making the polymer suitable for cold pressing.

[0053] In some embodiments, the first monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, vinyl acetate, trifluoroethyl methacrylate, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

[0054] During battery manufacturing, hot pressing or cold pressing is required to achieve a tight bond between the separator and the electrode. To increase the speed and reduce the energy consumption of battery production lines, hot pressing is gradually being replaced by cold pressing, leveraging existing battery manufacturing processes to improve the bond between the electrode and separator. Cold pressing involves shaping wound battery cells to reduce their elasticity, improve the assembly yield, and increase the consistency of the finished cell thickness. Because the cold pressing process operates at relatively low ambient temperatures, an adhesive with a relatively low glass transition temperature is required to achieve effective bonding between the electrode and separator.

[0055] The unsaturated ester group in the first monomer facilitates polymerization, resulting in excellent stability and strong adhesion for the acrylic copolymer. The ester group in the first monomer also enhances the polymer's anti-swelling ability. The polymerization of the soft and hard monomers in the first monomer also modulates the polymer's glass transition temperature, helping to keep the polymer's glass transition temperature within a suitable range. This helps ensure that the acrylic copolymer has a lower glass transition temperature, enabling its use as a binder in cold pressing processes.

[0056] By using any one or more of the above first monomers, the adhesive properties and anti-swelling properties of the acrylic copolymer can be adjusted.

[0057] In some embodiments, the first monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, isooctyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and isobornyl methacrylate.

[0058] In some embodiments, the second monomer includes at least one of acrylonitrile, methacrylonitrile, ethacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, heptenoic acid, itaconic acid, and maleic acid.

[0059] The second monomer contains an unsaturated double bond, which is beneficial to the polymerization of the monomer. It also has carboxyl and / or cyano functional groups. The carboxyl and cyano groups can form binding forces with the functional groups on the base film to improve the adhesion between the acrylic copolymer and the base film, and can also increase the cross-linking active sites of the acrylic copolymer, thereby improving the creep resistance and cohesive strength of the acrylic copolymer.

[0060] In some embodiments, the second monomer includes at least one of acrylonitrile, methacrylonitrile, acrylic acid, and methacrylic acid.

[0061] In some embodiments, the third monomer includes at least one of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide.

[0062] The structure of the third monomer includes an unsaturated amide group, which is beneficial to the polymerization of the monomer. This type of monomer can play a role in regulating the molecular weight and also has good adhesion and anti-swelling properties.

[0063] The molecular weight of the acrylic ester copolymer is helpful to improve the adhesion within a certain range. The use of any one or more of the above-mentioned third monomers can play a role in regulating the molecular weight, thereby regulating the molecular weight of the acrylic ester copolymer.

[0064] In some embodiments, the third monomer includes at least one of acrylamide and N-methylol acrylamide.

[0065] The test of ester, carboxyl, acrylamide, carbonyl, amide and cyano groups in the organic polymer structure is carried out according to the national standard GB / T 6040-2002 General Rules for Infrared Spectroscopy Analysis. The sample is pressed into a KBr pellet using the pellet transmission method. The KBr background blank is subtracted by the transmission method to obtain the sample test spectrum (resolution: 4 cm -1 , wave number range: 400cm -1 -4000cm -1 ).

[0066] In some embodiments, the second polymer comprises an acrylate copolymer.

[0067] When the first polymer and the second polymer are both acrylic copolymers, the manufacturing costs of the first polymer and the second polymer are relatively low, and the compatibility between the first polymer and the second polymer is relatively good. When used as an adhesive on the surface of the base film, the mixing effect of the two is relatively good. The second polymer with a smaller particle size can better fill the gaps in the first polymer with a larger particle size, thereby increasing the packing density of the polymer, so that the polymer has better bonding properties under both hot pressing and cold pressing processes.

[0068] As an example, the first polymer and the second polymer can have the same chemical composition.

[0069] In some embodiments, when the first polymer and the second polymer are both acrylic copolymers, the Dv50 particle size of the first polymer is 6 μm-12 μm, and the Dv50 particle size of the second polymer is 0.8 μm-1.5 μm.

[0070] As an example, the first polymer may have a Dv50 particle size of 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, or 12 μm.

[0071] As an example, the second polymer may have a Dv50 particle size of 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, or 1.5 μm.

[0072] When the Dv50 particle size of the first and second polymers falls within the aforementioned range, the smaller second polymer can better fill the voids in the larger first polymer, resulting in a better blend of the first and second polymers. The overall particle size of the mixed polymers is more moderate, effectively reducing stress rebound and clogging of the basement membrane pores after cold or hot pressing. The Dv50 particle size represents the size at which 50% of the sample's total volume has a particle size larger than this value, while another 50% has a particle size smaller than this value. Dv50 can represent the sample's median particle size.

[0073] The volume particle size distribution Dv50 of the polymer can be tested using methods well known in the art. As an example, you can refer to GB / T 19077-2016 and use a Malvern laser particle size analyzer for characterization testing, such as using instruments such as Malvern's Mastersizer-3000 for testing. Specifically, a laser particle size analyzer (Malvern 3000, MasterSizer 3000) can be used for testing, and the main light source uses a helium-neon red light source. Take a clean small beaker and add 1g of the sample to be tested, add a drop of surfactant, add 20ml of deionized water, and ultrasonicate at 53KHz / 120W for 5min to ensure that the sample is completely dispersed. Turn on the laser particle size analyzer, clean the optical path system, and automatically test the background. Stir the ultrasonicated solution to be tested to make it evenly dispersed, put it into the sample cell as required, and start measuring the particle size. The measurement results can be read from the instrument.

[0074] It should be noted that when the polymer includes a first polymer and a second polymer, the particle size distribution peak of the polymer will show a bimodal peak, and the peak values ​​of the bimodal peaks correspond to the Dv50 particle size of the second polymer (the peak with a smaller particle size) and the Dv50 particle size of the first polymer (the peak with a larger particle size), respectively. At this time, the Dv50 particle size of the polymer is larger than the Dv50 particle size of the second polymer and smaller than the Dv50 particle size of the first polymer.

[0075] In some embodiments, when the first polymer and the second polymer are both acrylic copolymers, the storage modulus of the polymers is 100 MPa-800 MPa.

[0076] As an example, the storage modulus of the polymer may be 100 MPa, 200 MPa, 300 MPa, 400 MPa, 500 MPa, 600 MPa, 700 MPa, or 800 MPa.

[0077] When the storage modulus of the polymer is within the aforementioned range, the stress rebound of the polymer after hot pressing or cold pressing or the blockage of the pore structure of the basement membrane can be reduced.

[0078] The storage modulus of a polymer can be measured using methods known in the art. For example, a polymer is pressed into a sample measuring 10 mm × 10 mm × 4 mm using a mold. The storage modulus of the sample is measured using a Perkin Elmer DMA 8000 in single cantilever mode, at a frequency of 1 Hz, an amplitude of 0.5 mm, and a temperature of 25°C.

[0079] In some embodiments, the second polymer includes at least one of a polyvinyl fluoride polymer and a polyvinylidene fluoride polymer.

[0080] When the second polymer is the aforementioned fluorine-containing polymer, it exhibits superior chemical corrosion resistance, high-temperature resistance, and electrochemical stability, thereby improving the overall chemical stability and high-temperature resistance of the polymer. Furthermore, due to the high crystallinity and interfacial resistance of the aforementioned fluorine-containing polymer, its affinity for liquid electrolytes is poor, preventing the electrolyte from properly wetting the second polymer. By mixing a first polymer with relatively poor electrolyte wetting with a second polymer, the resulting polymer exhibits excellent electrolyte wetting while also combining the other advantages of both the first and second polymers.

[0081] In some embodiments, the polyfluoroethylene polymer includes at least one of polytetrafluoroethylene, polychlorotrifluoroethylene, and polyvinyl fluoride, thereby further improving the high temperature resistance and chemical stability of the polymer.

[0082] In some embodiments, the polyvinylidene fluoride polymer includes at least one of polyvinylidene fluoride, a vinylidene fluoride-trifluoroethylene copolymer, a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-trifluoroethylene-hexafluoropropylene copolymer, a vinylidene fluoride-hexafluoropropylene-acrylic acid copolymer, and a vinylidene fluoride-hexafluoropropylene-acrylate copolymer. This can further improve the high temperature resistance and chemical stability of the polymer.

[0083] In some embodiments, the polyvinylidene fluoride polymer includes at least one of polyvinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymer, thereby further improving the high temperature resistance of the polymer.

[0084] In some embodiments, when the first polymer is an acrylic copolymer and the second polymer is the aforementioned fluorine-containing polymer, the Dv50 particle size of the first polymer is 5 μm-10 μm, and the Dv50 particle size of the second polymer is 0.5 μm-4 μm.

[0085] As an example, the first polymer may have a Dv50 particle size of 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, or 10 μm.

[0086] As an example, the second polymer may have a Dv50 particle size of 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, or 4 μm.

[0087] When the Dv50 particle size of the first polymer and the second polymer is within the aforementioned range, the second polymer with smaller particle size can better fill the gaps in the first polymer with larger particle size, the compounding effect of the first polymer and the second polymer is better, and the overall particle size of the polymer after mixing is relatively moderate, thereby effectively reducing stress rebound and blockage of the basement membrane pores after cold pressing or hot pressing processes.

[0088] It should be noted that when the polymer includes a first polymer and a second polymer, the particle size distribution peak of the polymer will show a bimodal peak, and the peak values ​​of the bimodal peaks correspond to the Dv50 particle size of the second polymer (the peak with a smaller particle size) and the Dv50 particle size of the first polymer (the peak with a larger particle size), respectively. At this time, the Dv50 particle size of the polymer is larger than the Dv50 particle size of the second polymer and smaller than the Dv50 particle size of the first polymer.

[0089] In some embodiments, the mass fraction of the first polymer in the polymer is 50%-90%, and the mass fraction of the second polymer in the polymer is 10%-50%. Thus, the polymer has good bonding properties and high temperature resistance.

[0090] In some embodiments, the polymer has a storage modulus of 300 MPa-1500 MPa.

[0091] As an example, the storage modulus of the polymer can be 300 MPa, 400 MPa, 500 MPa, 600 MPa, 700 MPa, 800 MPa, 900 MPa, 1000 MPa, 1100 MPa, 1200 MPa, 1300 MPa, 1400 MPa, or 1500 MPa.

[0092] Compared to acrylic copolymers, polyvinyl fluoride and polyvinylidene fluoride polymers have smaller particle sizes and higher modulus. By properly blending the first and second polymers, the overall modulus of the polymer can be controlled within an appropriate range, thereby reducing stress rebound after hot or cold pressing or clogging of the basement membrane pore structure.

[0093] As an example, the mass fraction of the first polymer in the polymer is 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%.

[0094] As an example, the mass fraction of the second polymer in the polymer is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%.

[0095] When the mass fractions of the first polymer and the second polymer in the polymer are within the aforementioned range, the particle size of the first polymer is larger, and a better mechanical linkage effect can be achieved between the larger first polymer and the surface structure of the electrode, so that the battery has better hardness and internal adhesion; at the same time, an appropriate amount of the second polymer can fully fill the gaps in the first polymer with a larger particle size, increase the number of effective contact sites per unit area between the isolation membrane and the electrode, and improve the adhesion.

[0096] In some embodiments, the aforementioned acrylic copolymer can be obtained by emulsion polymerization. Specifically, the constituent monomers of the acrylic copolymer, an initiator, and an emulsifier can be mixed to obtain a mixture, the mixture can be polymerized to obtain a polymer emulsion, and the polymer emulsion can be granulated to obtain the acrylic copolymer. The acrylic copolymer monomers can include the aforementioned first monomer, second monomer, and third monomer, with the mass ratio of the first monomer, second monomer, and third monomer being 100:(10-60):(5-20).

[0097] In some embodiments, when the second polymer is at least one of a polyvinyl fluoride polymer and a polyvinylidene fluoride polymer, the aforementioned second polymer can be obtained by an emulsion polymerization method. Specifically, the constituent monomers, initiator, and emulsifier of the polymer can be mixed to obtain a mixture, and the mixture can be polymerized to obtain a polymer emulsion. The polymer emulsion is granulated to obtain the second polymer.

[0098] As an example, when the second polymer is polyvinylidene fluoride, the constituent monomers of the second polymer are mainly VDF monomer (vinylidene fluoride); when the second polymer is a vinylidene fluoride-hexafluoropropylene copolymer, the constituent monomers of the second polymer are VDF monomer and HFP monomer (hexafluoropropylene), and the mass ratio of the two is (50:50)-(80:20).

[0099] The particle size of polymer spheres in emulsion polymers is usually nanometer-scale. If they are directly scraped onto the base film, pore blockage or insufficient adhesion may occur due to the small particle size of the polymer spheres. When synthesizing polymer materials through emulsion polymerization, granulation treatment can be used to obtain granular polymer materials, which helps to obtain polymers with larger particle sizes.

[0100] In some embodiments, the granulation process comprises airflow spray drying, and in particular, the airflow spray drying comprises two-fluid spray drying.

[0101] 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.

[0102] 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.

[0103] As an example, when the first polymer and the second polymer are both acrylic copolymers, the two-fluid spray drying parameters of the polymer emulsion of the first polymer are as follows: the air pressure of the two-fluid spray drying is 0.1MPa-30MPa, and the hydraulic pressure of the two-fluid spray drying is 0.1MPa-20MPa; the two-fluid spray drying parameters of the polymer emulsion of the second polymer are as follows: the air pressure of the two-fluid spray drying is 10MPa-50MPa, and the hydraulic pressure of the two-fluid spray drying is 0.1MPa-20MPa.

[0104] As an example, when the first polymer is an acrylic copolymer and the second polymer is at least one of a polyvinyl fluoride polymer and a polyvinylidene fluoride polymer, the two-fluid spray drying parameters of the polymer emulsion of the first polymer are as follows: the air pressure of the two-fluid spray drying is 0.1MPa-30MPa, and the hydraulic pressure of the two-fluid spray drying is 0.1MPa-20MPa; the two-fluid spray drying parameters of the polymer emulsion of the second polymer are as follows: the air pressure of the two-fluid spray drying is 10MPa-50MPa, and the hydraulic pressure of the two-fluid spray drying is 0.1MPa-20MPa.

[0105] In some embodiments, the first polymer and the second polymer powders can be prepared separately by granulation and then mixed to obtain the aforementioned polymers. Alternatively, the mixing can be performed when preparing the binder slurry.

[0106] In a second aspect of the present application, the present application provides an isolation membrane comprising the aforementioned polymer. Thus, the isolation membrane has all the characteristics and advantages of the aforementioned polymer, which will not be described in detail here.

[0107] In some embodiments, referring to FIG. 1 , the isolation film may include a base film 31 and a polymer 32 located on at least one side of the base film 31 ; in other embodiments, the polymer 32 may be located on two opposite surfaces of the base film 31 .

[0108] In some embodiments, the base film may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, and non-woven fabric.

[0109] By adopting a base film made of the above-mentioned material, the adhesion of the polymer on the base film can be effectively improved, thereby improving the structural stability of the isolation membrane.

[0110] In a third aspect of the present application, a battery is provided, comprising the aforementioned separator, thereby having all the features and advantages of the aforementioned separator, which will not be described in detail here.

[0111] During the battery's charge and discharge processes, active ions are embedded in and extracted from the positive and negative electrodes. The electrolyte conducts these 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.

[0112] [Positive electrode]

[0113] The positive electrode sheet includes a positive electrode current collector 21 and a positive electrode active material layer 22 disposed on at least one side of the positive electrode current collector 21 . The positive electrode active material layer 22 includes a positive electrode active material.

[0114] As an example, referring to FIG. 3 , the positive electrode current collector 21 has two surfaces facing each other in its thickness direction, and the positive electrode active material layer 22 is provided on either or both of the two facing surfaces of the positive electrode current collector 21 .

[0115] 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.).

[0116] 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.

[0117] 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. Among them, the lithium transition metal oxide may include lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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 x MO2, wherein M includes at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu, and 0<x≤1.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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).

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] In some embodiments, the positive active material layer may further optionally include a binder.

[0131] 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.

[0132] In some embodiments, the positive active material layer may further optionally include a conductive agent.

[0133] 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.

[0134] 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.

[0135] [Negative electrode]

[0136] The negative electrode sheet includes a negative electrode current collector 11 and a negative electrode active material layer 12 disposed on at least one side of the negative electrode current collector 11 . The negative electrode active material layer 12 includes a negative electrode active material.

[0137] As an example, the negative electrode current collector 11 has two surfaces facing each other in its thickness direction, and the negative electrode active material layer 12 is provided on either or both of the two facing surfaces of the negative electrode current collector 11 .

[0138] 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.).

[0139] In some embodiments, the negative electrode active material may adopt negative electrode active materials for batteries that are well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, 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.

[0140] In some embodiments, the negative active material layer may further optionally include a binder.

[0141] As an example, the binder in the negative electrode active material layer 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).

[0142] In some embodiments, the negative active material layer may further optionally include a conductive agent.

[0143] As an example, the conductive agent includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0144] 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)).

[0145] 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.

[0146] [Electrolytes]

[0147] 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.

[0148] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0153] In some embodiments, the battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0154] 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.

[0155] In some embodiments, the battery may include at least one of a battery cell, a battery module, and a battery pack.

[0156] The present application has no particular limitation on the shape of the battery, which can be cylindrical, square, or any other shape. For example, FIG2 shows a square-structured battery cell 5 as an example.

[0157] In some embodiments, referring to Figure 3, 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 isolation membrane 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.

[0158] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0159] Figure 4 shows an example battery module 4. In the battery module 4, multiple battery cells 5 can be arranged in sequence along the length of the battery module 4. Of course, they can also be arranged in any other manner. The multiple battery cells 5 can further be fixed using fasteners.

[0160] 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.

[0161] 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.

[0162] Figures 5 and 6 illustrate an example battery pack 1. The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed 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.

[0163] In a fourth 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.

[0164] The power-consuming device may include at least one of the battery cells, battery modules, and battery packs provided in this application. The battery cells, battery modules, and battery packs may be used as power sources for the power-consuming device, or as energy storage units for the power-consuming device. The power-consuming device may include mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (refer to FIG. 7 , such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0165] As an electrical device, a battery cell, battery module or battery pack can be selected according to its usage requirements.

[0166] The present invention will be described below by way of specific examples. It should be noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, they are determined according to the techniques or conditions described in the literature in this area or according to the product specifications. Reagents or instruments not specified by manufacturer are all commercially available conventional products.

[0167] Example 1

[0168] 1. Preparation of polymer:

[0169] Preparation of the first polymer:

[0170] (1) Synthesis of polymer emulsion: According to the mass ratio of the first monomer, the second monomer, and the third monomer, ethyl acrylate, acrylic acid, and acrylamide, a total of 1000 g were weighed respectively. The monomers were mixed evenly. In a 5L four-necked flask equipped with a mechanical stirrer, a thermometer, and a condenser, 1000 g of the mixed monomers, 20 g of the emulsifier sodium dodecylbenzenesulfonate, 5 g of the initiator potassium persulfate, and 1200 g of deionized water were added. Emulsification was carried out at high speed stirring for 30 minutes. Under nitrogen protection, the temperature was raised to 80°C and the reaction was carried out for 4 hours. The temperature was then lowered to below 40°C, the pH was adjusted to neutral, and the material was filtered to obtain a polymer emulsion.

[0171] (2) The polymer emulsion is spray-dried to obtain a binder for the isolation film. The conditions of the two-fluid spray-drying process are: inlet air temperature 110°C, outlet air temperature 50°C, air pressure 5MPa, and hydraulic pressure 3MPa.

[0172] Preparation of the second polymer:

[0173] The second polymer uses the same polymer emulsion as the first polymer, except that the conditions of the two-fluid spray drying process are: inlet air temperature 110°C, outlet air temperature 50°C, air pressure 15MPa, and hydraulic pressure 5.5MPa.

[0174] 2. Preparation of batteries

[0175] (1) Preparation of isolation membrane

[0176] A commercially available PE microporous film with a thickness of 7 μm and an average pore size of 80 nm (from Zhuogao Electronic Technology Co., Ltd.) was used as the base membrane. The first polymer and the second polymer prepared above were mixed in a mass ratio of 80:20 as a binder in deionized water to obtain a binder slurry (solid content of 20%). The binder slurry was sprayed on both surfaces of the base membrane and dried to remove the solvent. The coating density of the polymer on the base membrane was 1.5 g / m 2 , and obtain an isolation film.

[0177] (2) Preparation of positive electrode sheet

[0178] 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.

[0179] (3) Preparation of negative electrode sheet

[0180] 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 a negative electrode slurry (solid content of 63%). 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.

[0181] (4) Preparation of electrolyte

[0182] 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.

[0183] (5) Battery assembly

[0184] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, wound, and cold-pressed (during which the separator is bonded to the electrode sheet) 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 battery is obtained.

[0185] The differences between other examples and comparative examples and Example 1 are shown in Table 1. Specifically, the mass ratio of the first polymer to the second polymer in Examples 2-3 is different from that in Example 1; the particle size of the first polymer in Examples 4-5 is different from that in Example 1; the particle size of the second polymer in Examples 6-7 is different from that in Example 1; the second polymer in Examples 8-14 is polyvinylidene fluoride, wherein the mass ratio of the first polymer to the second polymer in Examples 9-10 is different from that in Example 8; the particle size of the first polymer in Examples 11-12 is different from that in Example 8; the particle size of the second polymer in Examples 13-14 is different from that in Example 8; in Comparative Example 1, only the first polymer in Example 1 is used as a binder; in Comparative Example 2, only the second polymer in Example 1 is used as a binder; and in Comparative Example 3, polyvinylidene fluoride is used as a binder.

[0186] Table 1

[0187] The first polymer and the second polymer in the above examples and comparative examples were tested as follows. The test methods are as follows. The test results are shown in Table 2:

[0188] 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.

[0189] The polymers in the above examples and comparative examples were tested as follows. The mass ratio of the first polymer to the second polymer in the polymer was 80:20. The test results are shown in Table 2. The test method is as follows:

[0190] Swelling performance test: (1) Dissolution: Mix 10g of polymer powder and 90g of N-methylpyrrolidone (NMP), stir and dissolve at 40℃ for 5h to obtain polymer glue; (2) Film preparation: Pour the stirred polymer glue into a polytetrafluoroethylene drying tray, bake at 70℃ for 7 days to obtain a dry film; (3) Swelling degree test: Take a dry film of about 1g, with a thickness of 2mm, weigh its exact mass and record it as M1, immerse it in electrolyte, and bake it in a 70℃ oven. After 24 hours, the sample was taken out and allowed to stand for 1 hour, then wiped clean and its mass M2 was weighed. The swelling degree of the polymer was calculated according to the mass swelling degree = (M2-M1) / M1×100%. The electrolyte preparation method was as follows: ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were mixed in a mass ratio of 3:5:2 to obtain an electrolyte solvent, and the electrolyte solvent was prepared with lithium hexafluorophosphate (LiPF6) to form an electrolyte with a molar concentration of LiPF6 of 1 mol / L.

[0191] Tap density test: The mass per unit volume of the powder in the container after being tapped under specified conditions; Pt = (m-m0) / V, where Pt is the tap density of the powder, in g / cm 3 ; m is the total mass of the measuring cylinder and the sample, in g; m0 is the weight of the measuring cylinder, in g; V is the tapped volume of the powder, in cm 3 .

[0192] The specific test method refers to the national standards: GB / T5162-2006 Determination of tap density of metal powders & GBT24533-2009 Graphite-based negative electrode materials for lithium-ion batteries. Fix the graduated cylinder containing the powder on a mechanical vibration device. The motor drives the mechanical vibration device to vibrate vertically up and down. The powder is gradually vibrated. After reaching the set number of times, the vibration is stopped and the volume of the graduated cylinder is read. According to the definition of density: mass divided by volume, the density of the powder after tapping is calculated.

[0193] Storage modulus test: The polymer was pressed into a sample with a size of 10 mm × 10 mm × 4 mm using a mold. The test conditions were: single cantilever mode, frequency 1 Hz, amplitude 0.5 mm, temperature 25°C, and a Perkin Elmer DMA 8000 was used to measure the storage modulus of the sample.

[0194] The batteries in the above embodiments and comparative examples were tested as follows. The test results are shown in Table 2. The test method is as follows:

[0195] Cold Press Bonding Test: The battery negative electrode sheet and separator were stacked and placed on a hot press. The press parameters were set at 25°C, 7 tons of pressure, and 15 seconds. A bonded separator / negative electrode sheet sample was produced. The separator / electrode sheet sample was cut into 150 mm x 20 mm rectangular strips. The negative electrode sheet side of the strip was attached to a steel plate using double-sided tape. At one end of the strip, the separator and negative electrode sheet were separated by 2 cm along the length to produce the test specimen. The steel plate was held horizontally and secured with the lower clamp of a universal testing machine (Xie Qiang Instrument Manufacturing (Shanghai) Co., Ltd., Model CTM2100). The peeled end of the separator, as described above, was secured with the upper clamp of the universal testing machine and connected to a tensile testing machine. The test conditions were set at a tensile rate of 20 mm / min and a horizontal pull of 10 cm. After the tensile force stabilized, the tensile force was recorded. The ratio of the tensile force to the sample width was used to determine the separator / negative electrode sheet bond strength.

[0196] Large fixture cycle performance test:

[0197] A clamp force of 10000N was applied to the outside of the battery cell, and a cycle test was performed under this state. The test steps were as follows: at 25°C, the battery prepared in the embodiment 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. The above steps were repeated for the same battery, and the discharge capacity C of the battery after the nth cycle was recorded at the same time. n , then the battery capacity retention rate P after each cycle n =(C n / C0)×100%. The difference in cycle performance can be reflected by the battery capacity retention rate after 500 cycles.

[0198] Battery cell hardness test:

[0199] Place the battery cell on a table with both ends level, with a 12cm wide hollowed-out area in the middle. Allow the cell to lie naturally flat and measure the deviation of the cell center from the horizontal reference line to assess the cell's hardness. The greater the deviation of the cell center from the horizontal reference line, the worse the cell's hardness.

[0200] Table 2

[0201] The test results show that in Examples 1-14, by compounding the particle sizes of the first and second polymers, the second polymer can fully fill the gaps between the first polymers, achieving maximum packing density. When the aforementioned polymers are used as binders on the surface of the base film, the binder on the separator can better penetrate the surface structure of the electrode, achieving a better embedding effect and excellent bonding performance for the polymers as a whole. Furthermore, the second polymer filling the gaps between the first polymers can also reduce stress rebound of the polymers as a whole after pressure is applied, maintaining the bonding effect after pressure, and achieving high battery hardness and long-clamp cycle performance.

[0202] Comparative Example 1 uses only acrylic copolymers with larger particle sizes as binders. The gaps between the binders are large, the anti-swelling performance is poor, the stress rebound of the binder after pressure is applied is large, and the hardness of the battery core is poor.

[0203] In Comparative Example 2, only acrylic acid ester copolymer with a smaller particle size is used as the binder. The binder can provide too few contact sites, has poor anti-swelling performance, and has poor bonding performance.

[0204] In Comparative Example 3, only polyvinylidene fluoride with a smaller particle size is used as the binder. The storage modulus of the binder is large, the stress rebound of the binder after pressure is applied is large, and the hardness of the battery cell is poor.

[0205] 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 polymer, wherein include: a first polymer and a second polymer, wherein the Dv50 particle size of the first polymer is greater than the Dv50 particle size of the second polymer, and the first polymer comprises an acrylic copolymer.

2. The polymer according to claim 1, wherein The monomers of the acrylic ester copolymer include a first monomer, a second monomer, and a third monomer, and the monomers of the acrylic ester copolymer meet at least one of the following conditions: The first monomer comprises at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, vinyl acetate, trifluoroethyl methacrylate, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate; The second monomer comprises at least one of acrylonitrile, methacrylonitrile, ethacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, heptenoic acid, itaconic acid, and maleic acid; The third monomer includes at least one of acrylamide, N-methylol acrylamide and N-butoxymethyl acrylamide.

3. The polymer according to claim 2, wherein The monomers of the acrylic copolymer meet at least one of the following conditions: The first monomer comprises at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, isooctyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and isobornyl methacrylate; The second monomer includes at least one of acrylonitrile, methacrylonitrile, acrylic acid, and methacrylic acid; The third monomer includes at least one of acrylamide and N-methylol acrylamide.

4. The polymer according to any one of claims 1 to 3, wherein The second polymer includes an acrylic copolymer.

5. The polymer according to claim 4, wherein The Dv50 particle size of the first polymer is 6 μm-12 μm, and the Dv50 particle size of the second polymer is 0.8 μm-1.5 μm.

6. The polymer according to claim 4 or 5, wherein The storage modulus of the polymer is 100 MPa-800 MPa.

7. The polymer according to any one of claims 1 to 3, wherein The second polymer includes at least one of a polyvinyl fluoride polymer and a polyvinylidene fluoride polymer.

8. The polymer according to claim 7, wherein The polyfluoroethylene polymer includes at least one of polytetrafluoroethylene, polychlorotrifluoroethylene, and polyvinyl fluoride; and / or, The polyvinylidene fluoride polymer includes at least one of polyvinylidene fluoride, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-acrylic acid copolymer, and vinylidene fluoride-hexafluoropropylene-acrylate copolymer.

9. The polymer according to claim 7 or 8, wherein The polyvinylidene fluoride polymer includes at least one of polyvinylidene fluoride and polyvinylidene fluoride-hexafluoropropylene copolymer.

10. The polymer according to any one of claims 7 to 9, wherein The Dv50 particle size of the first polymer is 5 μm-10 μm, and the Dv50 particle size of the second polymer is 0.5 μm-4 μm.

11. The polymer according to any one of claims 7 to 10, wherein The storage modulus of the polymer is 300 MPa-1500 MPa.

12. The polymer according to any one of claims 1 to 11, wherein The mass fraction of the first polymer in the polymer is 50%-90%, and the mass fraction of the second polymer in the polymer is 10%-50%.

13. A separator, wherein: The polymer comprises the polymer according to any one of claims 1 to 12.

14. A battery, wherein: The isolation film according to claim 13 is included.

15. An electrical device, wherein: Including the battery according to claim 14.

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