Battery, battery preparation method, and electric device

Abstract

A battery, a battery preparation method, and an electric device. The battery comprises: a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector, the negative electrode active material layer comprising a binder, and the binder comprising a butadiene copolymer; and a separator, the separator comprising a base membrane and a polymer located on at least one side of the base membrane, the side of the separator provided with the polymer being arranged opposite to the side of the negative electrode sheet provided with the negative electrode active material layer, the polymer comprising a first polymer and a second polymer, the first polymer comprising an acrylate copolymer, and the second polymer comprising a butadiene copolymer.

Description

Battery, method for preparing battery, and electrical device Technical Field

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

[0002] In recent years, batteries have been widely used in energy storage systems such as hydropower, thermal, wind, and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. In batteries, the amount and cost of binders are relatively small, but they can effectively improve battery performance and are an indispensable component of batteries. Binders, as inactive materials in batteries, can bond the various components and adjacent parts together, reducing the expansion and shedding of active materials during the battery's charge and discharge processes and lowering the battery's internal resistance. However, current batteries still suffer from problems such as insufficient bonding strength, which requires further improvement.

[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, the present application proposes a battery comprising: a negative electrode plate, the negative electrode plate comprising a negative electrode current collector and a negative electrode active material layer located at least on one side of the negative electrode current collector, the negative electrode active material layer comprising a binder, the binder comprising a butadiene copolymer; and a separator, the separator comprising a base film and a polymer located at least on one side of the base film, the side of the separator provided with the polymer being disposed opposite the side of the negative electrode plate provided with the negative electrode active material layer, the polymer comprising a first polymer and a second polymer, the first polymer comprising an acrylate copolymer and the second polymer comprising a butadiene copolymer. This effectively improves the bonding strength between the separator and the negative electrode plate, thereby enhancing the structural stability of the battery during charge and discharge cycles.

[0006] In some embodiments, the monomer of the first polymer and the derivative of the monomer of the first polymer include at least a first monomer, and the structure of the first monomer is shown in Formula 1:

[0007] Wherein, R1 includes hydrogen atom or C1-C6 alkyl, R2 includes substituted or unsubstituted C1-C 15 alkyl, substituted or unsubstituted C3-C6 isobornyl, wherein the C1-C 15The substituent of the alkyl group includes a hydroxyl group or a C1-C6 alkyl group. This is beneficial to the formation of the first polymer and improves the anti-swelling ability of the first polymer.

[0008] 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, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate. Thus, the anti-swelling ability of the first polymer can be further improved.

[0009] In some embodiments, the monomer of the first polymer and the derivative of the monomer of the first polymer further include a second monomer, and the structure of the second monomer is shown in Formula 2 and / or Formula 3:

[0010] and / or,

[0011] Wherein, R3 includes hydrogen atom or C1-C 18 R4 includes a hydrogen atom or a C1-C6 alkyl group. Thus, the ionic conductivity and bonding performance of the first polymer can be improved.

[0012] In some embodiments, the second monomer includes at least one of acrylonitrile, methacrylonitrile, ethacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid, thereby further improving the ionic conductivity and bonding properties of the first polymer.

[0013] In some embodiments, the monomer of the first polymer and the derivative of the monomer of the first polymer further include a third monomer, and the structure of the third monomer is shown in Formula 4:

[0014] Wherein, R5 includes a hydrogen atom, a C1-C6 alkyl group substituted with a hydroxyl group, or a C1-C6 alkoxy group, and R6 includes a hydrogen atom or a C1-C6 alkyl group. This facilitates the formation of the first polymer and adjusts the molecular weight of the first polymer.

[0015] In some embodiments, the third monomer includes at least one of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide. Thus, the third monomer can play a role in adjusting the molecular weight of the first polymer, so that the first polymer has better adhesion.

[0016] In some embodiments, the monomers of the second polymer and the derivatives of the monomers of the second polymer include at least a fourth monomer, and the structure of the fourth monomer is shown in Formula 5:

[0017] Among them, R7, R8, R9, R 10 Each of the groups independently includes a hydrogen atom, a phenyl group, an alkenyl group, a cyano group, and a linear or branched alkyl group, thereby improving the alkali resistance and adhesion of the second polymer.

[0018] In some embodiments, the fourth monomer includes butadiene and further includes at least one of styrene, acrylonitrile, isoprene, and propylene, thereby further improving the alkali resistance and adhesion of the second polymer.

[0019] In some embodiments, the second polymer includes at least one of styrene butadiene copolymer, acrylonitrile butadiene copolymer, butadiene isoprene copolymer, and butadiene propylene copolymer, thereby further improving the bonding strength between the negative electrode plate and the separator.

[0020] In some embodiments, the Dv50 particle size of the primary particles of the first polymer is 100 nm to 200 nm, and / or the Dv50 particle size of the primary particles of the second polymer is 100 nm to 200 nm. This can improve the bonding performance between the first polymer and the second polymer.

[0021] In some embodiments, the polymer has a Dv50 particle size of 1 μm to 18 μm, thereby reducing the pore blocking of the base film by the polymer.

[0022] In some embodiments, the mass of the first polymer in the polymer is m1, the mass of the second polymer in the polymer is m2, and m1:m2 is 100:(1-100). This can further improve the adhesion of the polymer.

[0023] In some embodiments, the polymer further comprises a tackifying resin, wherein the mass of the tackifying resin in the polymer is m3, and the ratio of m1:m3 is 100:(1-15), thereby improving the initial tack of the polymer.

[0024] In some embodiments, the tackifying resin satisfies at least one of the following conditions: the tackifying resin comprises at least one of rosin resin, terpene resin, and synthetic resin; and the number average molecular weight of the tackifying resin is 5000-50000. This can further improve the initial tack of the polymer.

[0025] In some embodiments, the battery further comprises a positive electrode sheet, the separator is located between the positive electrode sheet and the negative electrode sheet, the bonding force between the separator and the positive electrode sheet is a, the bonding force between the separator and the negative electrode sheet is b, (a:b) ≤ (5:1); preferably, (a:b) ≤ (2:1). This can improve the structural stability of the battery during charging and discharging.

[0026] In the second aspect of the present application, the present application proposes a method for preparing the aforementioned battery, comprising: blending an emulsifier, an initiator, and monomers constituting a first polymer in a mass ratio of (2-10): (0.2-1): 100, heating and reacting to obtain a first polymer emulsion; blending an emulsifier, an initiator, and monomers constituting a second polymer in a mass ratio of (2-10): (0.2-1): 100 to obtain a second polymer emulsion; mixing the first polymer emulsion and the second polymer emulsion, stirring, and spray drying to obtain the polymer; disposing the polymer on at least one side of a base film to obtain a separator; and disposing the side of the separator provided with the polymer opposite to the side of the negative electrode sheet provided with a negative electrode active material layer. Thus, the aforementioned battery can be prepared by a simple method.

[0027] In some embodiments, the first polymer is composed of monomers comprising a first monomer, a second monomer, and a third monomer, wherein the mass ratio of the first monomer, the second monomer, and the third monomer is 100:(1-50):(10-40). Thus, a first polymer having excellent adhesion can be obtained.

[0028] In some embodiments, the constituent monomers of the second polymer include a fourth monomer, thereby obtaining a second polymer having excellent adhesiveness.

[0029] In some embodiments, the second polymer emulsion satisfies at least one of the following conditions: a solid content of the second polymer emulsion is 30% to 60%; and a viscosity of the second polymer emulsion at 25°C is 10 mPa·s to 300 mPa·s. This facilitates obtaining polymer particles of a moderate size through spray drying.

[0030] In some embodiments, the method further comprises adding a tackifying resin to the spray slurry before spray drying, wherein the mass fraction of the tackifying resin in the spray slurry is 1%-20%. Thus, the adhesion of the polymer can be improved by adding the tackifying resin.

[0031] In some embodiments, the viscosity of the tackifying resin is 100 mPa·s to 5000 mPa·s at 25° C. This can further improve the adhesion of the polymer.

[0032] In a third aspect of the present application, an electrical device is provided, comprising the aforementioned battery and / or a battery prepared using the aforementioned method. Thus, the electrical device possesses all the features and advantages of the aforementioned battery and method for preparing the battery, and further description thereof is omitted. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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:

[0034] FIG1 is a schematic structural diagram of a battery according to one embodiment of the present application;

[0035] FIG2 is a schematic structural diagram of a battery according to another embodiment of the present application;

[0036] FIG3 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0037] FIG4 is an exploded view of the battery cell according to an embodiment of the present application shown in FIG3 ;

[0038] FIG5 is a schematic diagram of a battery module according to an embodiment of the present application;

[0039] FIG6 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0040] FIG7 is an exploded view of the battery pack shown in FIG6 according to an embodiment of the present application;

[0041] FIG8 is a schematic diagram of an electrical device using a battery as a power source according to one embodiment of the present application;

[0042] FIG9 is a partial schematic flow diagram of a method for preparing a battery according to one embodiment of the present application;

[0043] FIG10 is a schematic flow chart of a method for preparing a battery according to one embodiment of the present application.

[0044] Description of reference numerals:

[0045] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell;

[0046] 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

[0047] 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.

[0048] 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).

[0049] 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.

[0050] " 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 selected lower limit and upper limit define the boundary of special scope.The scope that this mode limits can be to include end value or not include end value, and can be combined arbitrarily, and promptly 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 parameter, it is also expected that the scope of 60-110 and 80-120 is understood to be.In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 listed, then the following scope can all be expected to: 1-3,1-4,1-5,2-3,2-4 and 2-5.In the application, unless otherwise specified, numerical range " ab " represents the abbreviation of any real number combination between a and b, and 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.

[0051] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] An adhesive needs to be placed between the separator and the electrode to tightly bond the adjacent parts together. Since the positive and negative electrode sheets and the separator bonded together adhere to and support each other, a structure with a certain thickness is formed. A structure with a certain thickness has a certain hardness. The negative electrode sheet will expand during the charge and discharge process. If the bonding force is weak, a gap will form between the positive and negative electrode sheets and the separator. The positive and negative electrode sheets and the separator cannot adhere to and support each other, resulting in a loose battery, a lower hardness, a significant increase in the internal resistance of the battery, and a worse wettability of the electrode to the electrolyte, which in turn leads to a significant reduction in the battery's cycle performance. Among them, the bonding performance between the separator and the negative electrode sheet is usually weaker than the bonding performance between the separator and the positive electrode sheet. Specifically, the surface smoothness of the negative electrode active material is higher than that of the positive electrode active material, which prevents the binder added to the negative electrode active material layer from forming a strong bond with the negative electrode active material in the negative electrode active material layer. At the same time, the negative electrode active material in the negative electrode active material layer generally has a high packing density, which makes the gaps between the negative electrode active material particles too small, which is not conducive to the binder in the negative electrode active material layer entering between the negative electrode active material particles to achieve infiltration of the negative electrode active material, and the mechanical riveting effect of the binder is poor. In addition, due to the small number of active groups on the surface of the negative electrode active material, the intermolecular force between the negative electrode active material and the binder is also weak, ultimately resulting in poor adhesion of the negative electrode active material layer and poor adhesion between the negative electrode plate and the separator. Therefore, by improving the adhesion between the separator and the negative electrode plate, the poor adhesion between the negative electrode plate and the separator can be effectively alleviated, thereby improving the wettability of the plate to the electrolyte and improving the cycle performance of the battery.

[0058] The binder in the negative electrode slurry is in a uniformly dispersed state. After the negative electrode slurry coated on one side of the negative electrode current collector is dried, part of the binder in the negative electrode active material layer formed by the negative electrode slurry will move from the side close to the negative electrode current collector to the side away from the negative electrode current collector, so that there is more binder on the surface of the negative electrode active material layer away from the negative electrode current collector after drying. When the side of the isolation membrane with the polymer is arranged opposite to the side of the negative electrode sheet with the negative electrode active material layer, the polymer on the isolation membrane and the binder in the negative electrode active material layer have a stronger interaction force. In the present application, a first polymer and a second polymer are arranged on the surface of the base film, wherein the first polymer is an acrylate copolymer and the second polymer includes a butadiene copolymer. The first polymer can effectively improve the adhesion, mechanical stability and chemical stability of the isolation membrane, and the second polymer can improve the bonding force between the polymer and the butadiene copolymer in the negative electrode active material layer, further improve the bonding performance between the isolation membrane and the negative electrode plate, alleviate the poor fitting between the isolation membrane and the negative electrode plate, inhibit the volume expansion of the negative electrode plate during the lithium insertion and extraction process, improve the structural stability of the battery during the charge and discharge cycle, and effectively improve the cycle performance of the battery.

[0059] Binder refers to a material with adhesive properties that is used to bond different substances together.

[0060] Copolymer, a polymerization reaction in which two or more monomers participate together, is called copolymerization. The polymer formed contains two or more monomer units. This type of polymer is called a copolymer, also known as an interpolymer.

[0061] In the first aspect of the present application, a battery is proposed, with reference to FIG1 , comprising: a negative electrode plate, the negative electrode plate comprising a negative electrode current collector 11 and a negative electrode active material layer 12 located at least on one side of the negative electrode current collector, the negative electrode active material layer 12 comprising a binder, the binder comprising a butadiene copolymer; and a separator, the separator comprising a base film 31 and a polymer 32 located at least on one side of the base film, the side of the separator provided with the polymer 32 being arranged opposite to the side of the negative electrode plate provided with the negative electrode active material layer 12, the polymer comprising a first polymer and a second polymer, the first polymer comprising an acrylate copolymer, and the second polymer comprising a butadiene copolymer. The combination of the first polymer and the second polymer can not only enhance the bonding strength of the polymers themselves, for example, the adhesion between the polymer and the base film, but also improve the bonding performance between the separator and the negative electrode plate.

[0062] Butadiene copolymers have the characteristics of strong alkali resistance, soft film formation, good air permeability, strong bonding strength, etc., and have good mechanical stability and chemical stability when used as binders in the negative electrode active material layer.

[0063] As an example, the butadiene copolymer binder in the negative electrode active material layer may include styrene-butadiene rubber (SBR). Furthermore, the negative electrode active material layer may also include other binders, such as at least one of polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0064] In some embodiments, the base film may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, and non-woven fabric.

[0065] By adopting the base film made of the above materials, the adhesion of the polymer on the base film can be effectively improved, thereby improving the structural stability of the isolation film.

[0066] In some embodiments, the mass of the first polymer in the polymer is m1, the mass of the second polymer in the polymer is m2, and m1:m2 is 100:(1-100).

[0067] As an example, m1:m2 can be 100:1, 100:5, 100:10, 100:15, 100:20, 100:25, 100:30, 100:35, 100:40, 100:45, 100:50, 100:55, 100:60, 100:65, 100:70, 100:75, 100:80, 100:85, 100:90, 100:95 or 100:100.

[0068] The polymer on the separator surface is composed of secondary particles formed by agglomeration of primary particles of the first polymer and primary particles of the second polymer. Both the primary particles of the first polymer and the primary particles of the second polymer have the opportunity to be exposed on the surface of the secondary particles. When the mass ratio of the first polymer to the second polymer in the polymer is within the aforementioned range, the amount of the first polymer and the second polymer exposed on the surface of the secondary particles can be controlled. The appropriate amount of the first polymer exposed on the surface of the secondary particles can improve the adhesion of the polymer on the separator surface. The appropriate amount of the second polymer exposed on the surface of the secondary particles can combine with the butadiene copolymer in the negative electrode active material layer, thereby improving the adhesion between the separator and the negative electrode plate.

[0069] In some embodiments, the monomer of the first polymer and the derivative of the monomer of the first polymer include at least a first monomer, and the structure of the first monomer is shown in Formula 1:

[0070] Wherein, R1 includes hydrogen atom or C1-C6 alkyl, R2 includes substituted or unsubstituted C1-C 15Alkyl, substituted or unsubstituted C3-C6 isobornyl, wherein C1-C 15 Substituents of the alkyl group include hydroxyl or C1-C6 alkyl.

[0071] During battery manufacturing, hot or cold pressing is required to achieve a tight bond between the separator and the electrode. The unsaturated ester group in the first monomer facilitates polymerization. The soft and hard monomers in the ester monomers form the backbone of the first polymer molecular chain segments through polymerization, giving the first polymer excellent stability and good adhesion, while also improving its anti-swelling properties.

[0072] 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.

[0073] 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, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

[0074] By using any one or more of the above first monomers, the adhesive properties and anti-swelling properties of the first polymer can be adjusted.

[0075] In some embodiments, the monomer of the first polymer and the derivative of the monomer of the first polymer further include a second monomer, and the structure of the second monomer is shown in Formula 2 and / or Formula 3:

[0076] and / or,

[0077] Wherein, R3 includes hydrogen atom or C1-C 18 R4 includes a hydrogen atom or a C1-C6 alkyl group.

[0078] 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 performance of the first polymer to the base film, and can also increase the cross-linking active sites of the first polymer, thereby improving the creep resistance and cohesive strength of the first polymer.

[0079] In some embodiments, the second monomer includes at least one of acrylonitrile, methacrylonitrile, ethacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid.

[0080] By using any one or more of the above-mentioned second monomers, the adhesive properties of the first polymer can be adjusted. Among them, the monomer containing a cyano group can also improve the ionic conductivity of the first polymer.

[0081] In some embodiments, the monomer of the first polymer and the derivative of the monomer of the first polymer further include a third monomer, and the structure of the third monomer is shown in Formula 4:

[0082] Wherein, R5 includes a hydrogen atom, a C1-C6 alkyl group substituted with a hydroxyl group, or a C1-C6 alkoxy group, and R6 includes a hydrogen atom or a C1-C6 alkyl group.

[0083] The structure of the third monomer includes an unsaturated amide group, which is beneficial to the polymerization of the monomer. This type of monomer plays a role in regulating the molecular weight and also has good adhesion and anti-swelling properties.

[0084] In some embodiments, the third monomer includes at least one of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide.

[0085] The use of any one or more third monomers mentioned above can play a role in regulating the molecular weight, so as to adjust the molecular weight of the polymer. The molecular weight of the first polymer is helpful to improve the adhesion within a certain range.

[0086] 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 ).

[0087] In some embodiments, the monomers of the second polymer and the derivatives of the monomers of the second polymer include at least a fourth monomer, and the structure of the fourth monomer is shown in Formula 5:

[0088] Among them, R7, R8, R9, R 10 Each independently includes a hydrogen atom, a phenyl group, an alkenyl group, a cyano group, and a linear or branched alkyl group.

[0089] The structure of the fourth monomer includes an unsaturated double bond, which is beneficial to the polymerization of the monomer and improves the strong alkali resistance and adhesion of the second polymer.

[0090] In some embodiments, the fourth monomer includes butadiene, and further includes at least one of styrene, acrylonitrile, isoprene, and propylene.

[0091] By using any one or more of the fourth monomers mentioned above, the alkali resistance and adhesion of the second polymer can be improved.

[0092] In some embodiments, the second polymer includes at least one of styrene butadiene copolymer, acrylonitrile butadiene copolymer, butadiene isoprene copolymer, and butadiene propylene copolymer.

[0093] The use of at least one of the above-mentioned butadiene copolymers can effectively improve the bonding performance between the separator and the negative electrode plate.

[0094] In some embodiments, the binder in the negative active material layer may have the same chemical composition as the second polymer.

[0095] In some embodiments, the primary particles of the first polymer have a Dv50 particle size of 100 nm to 200 nm, and / or the primary particles of the second polymer have a Dv50 particle size of 100 nm to 200 nm.

[0096] As an example, the Dv50 particle size of the primary particles of the first polymer can be 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 130 nm, 135 nm, 140 nm, 145 nm, 150 nm, 155 nm, 160 nm, 165 nm, 170 nm, 175 nm, 180 nm, 185 nm, 190 nm, 195 nm or 200 nm.

[0097] As an example, the Dv50 particle size of the primary particles of the second polymer can be 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 130 nm, 135 nm, 140 nm, 145 nm, 150 nm, 155 nm, 160 nm, 165 nm, 170 nm, 175 nm, 180 nm, 185 nm, 190 nm, 195 nm or 200 nm.

[0098] The particle size of polymer beads 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 beads. When synthesizing polymer materials through emulsion polymerization, granulation treatment can be used to obtain granular polymer materials, which helps to obtain polymers with a particle size of micrometers.

[0099] In some embodiments, the polymer has a Dv50 particle size of 1 μm to 18 μm.

[0100] As an example, the Dv50 particle size of the polymer can be 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm.

[0101] The polymer particles are secondary particles formed by the agglomeration of primary particles of a first polymer and primary particles of a second polymer. In this way, the first polymer acts as a skeleton, providing the polymer with higher bonding force and structural stability. The second polymer forms a binding force with the functional groups of the binder in the negative electrode active material layer, thereby improving the bonding effect between the isolation membrane and the negative electrode plate.

[0102] It is understood that polymer particles can be obtained after the polymer latex of the first polymer and the second polymer are mixed and spray-dried, wherein the primary particles of the first polymer and the second polymer are mixed together to constitute the spray-dried polymer secondary particles.

[0103] When the Dv50 particle size of the polymer is within the aforementioned range, it can not only improve the problem of polymer blocking the base membrane pores and increase the permeability of metal active ions on the isolation membrane, but also improve the problem of the thick coating formed by the polymer coating on the base membrane affecting the battery energy density.

[0104] The Dv50 particle size indicates that among the sample particles, 50% of the total volume of the particles have a particle size larger than this value, and another 50% of the total volume of the particles have a particle size smaller than this value; Dv50 can represent the median particle size of the sample.

[0105] The volume particle size distribution Dv50 of the polymer can be measured using methods known in the art. For example, GB / T 19077-2016 can be used for characterization testing using a Malvern laser particle size analyzer, such as a Malvern Mastersizer-3000.

[0106] In some embodiments, primary particles of the polymer can be obtained by emulsion polymerization, and secondary particles of the polymer can be obtained by spray drying the primary particles in the polymer emulsion. After cleaning and removing impurities from the primary particles in the polymer emulsion, the Dv50 particle size thereof can be measured using a laser particle size analyzer.

[0107] In some embodiments, the polymer may further include: a tackifying resin, the mass of the tackifying resin in the polymer is m3, and m1:m3 is 100:(1-15).

[0108] As an example, m1:m3 may be 100:1, 100:5, 100:7, 100:9, 100:10, 100:12, or 100:15.

[0109] When two polymer materials come into contact with each other, multiple forces, including strong forces such as chemical bonds, as well as weak forces such as hydrogen bonds and dispersion forces, will be generated between the atoms and molecules in adjacent polymers. For polymers, their viscosity is affected by dispersion forces, their own polarity, and hydrogen bonding. When m1:m3 is within the aforementioned range, after the tackifying resin contacts the first polymer and the second polymer, mutual chain diffusion and chain entanglement will occur between the tackifying resin and the first polymer and the second polymer. Through diffusion and entanglement, the tackifying resin is connected to the surfaces of the first polymer and the second polymer, and the polymer chain segments have high mobility. Since the initial viscosity of the polymer is strongly correlated with the mobility of the polymer chain segments, the polymers can quickly wet the contacting surfaces under relatively small external pressure, achieving molecular-level contact, thereby allowing countless intermolecular forces to generate sufficient bonding strength, and the overall bonding performance of the polymers is significantly improved.

[0110] In some embodiments, the tackifying resin satisfies at least one of the following conditions: the tackifying resin includes at least one of rosin resin, terpene resin, and synthetic resin; and the number average molecular weight of the tackifying resin is 5,000-50,000.

[0111] As an example, the rosin resin may include at least one of gum rosin, tall oil rosin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, esterified rosin, and maleated rosin; the terpene resin may include at least one of α-terpene resin, β-terpene resin, and terpene phenolic resin; the synthetic resin may include at least one of C5 petroleum resin, C9 petroleum resin, C5 / C9 copolymer petroleum resin, dicyclopentadiene resin, alkylphenolic resin, and xylene resin.

[0112] As an example, the tackifying resin may have a number average molecular weight of 5,000, 6,000, 7,000, 8,000, 9,000, 10,000, 12,000, 15,000, 18,000, 20,000, 22,000, 25,000, 28,000, 30,000, 32,000, 35,000, 38,000, 40,000, 42,000, 45,000, 48,000, or 50,000.

[0113] The chain diffusion and chain entanglement of polymer materials are related to their number average molecular weight. When the number average molecular weight of the tackifying resin is within the aforementioned range, the number average molecular weight of the tackifying resin is moderate, which is conducive to the diffusion and entanglement of chain segments, and the strength after entanglement is higher.

[0114] In some embodiments, the battery may further include: a positive electrode sheet, a separator located between the positive electrode sheet and the negative electrode sheet, the bonding force between the separator and the positive electrode sheet is a, the bonding force between the separator and the negative electrode sheet is b, (a:b)≤(5:1).

[0115] As an example, (a:b) can be 5:1, 4:1, 3:1, 2:1 or 1:1.

[0116] When (a:b) is within the aforementioned range, the bonding force between the isolation membrane and the positive electrode sheet and the negative electrode sheet is relatively high, which can effectively inhibit the expansion of the negative electrode sheet during the charge and discharge process. The positive electrode sheet, the negative electrode sheet and the isolation membrane are adhered to each other and support each other, which helps the battery maintain structural stability, makes the electrode sheet more wettable to the electrolyte, and improves the battery's cycle performance.

[0117] The adhesion between the separator and the electrode can be tested using methods known in the art. As an example, the electrode and separator can be overlapped and placed on a hot press. The hot press parameters are set to: temperature of 25°C, pressure of 7t, time of 15s, and pressing to obtain a bonded separator / electrode sample; the separator / electrode sample is cut into 150mm×20mm rectangular splines. The electrode side of the above rectangular spline is attached to a steel plate using double-sided tape. At one end of the rectangular spline, the separator and the electrode are separated by a length of 2cm in the longitudinal direction to prepare a test specimen. The steel plate is kept horizontal and fixed 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 is fixed with the upper clamp of the universal testing machine and connected to a tensile testing machine. The test conditions are set to a tensile rate of 20mm / min and a horizontal pull of 10cm. After the tension stabilizes, record the tension value and obtain the bonding force between the isolation film and the electrode through the ratio of the tension value to the sample width.

[0118] [Positive electrode]

[0119] As an example, referring to FIG. 2 , the positive electrode current collector 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 .

[0120] 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.).

[0121] 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.

[0122] 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 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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).

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] In some embodiments, the positive active material layer may further optionally include a binder.

[0136] 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.

[0137] In some embodiments, the positive active material layer may further optionally include a conductive agent.

[0138] 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.

[0139] 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.

[0140] [Negative electrode]

[0141] 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.

[0142] 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.

[0143] 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.).

[0144] 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.

[0145] 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.

[0146] 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)).

[0147] 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.

[0148] [Electrolytes]

[0149] 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.

[0150] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] In some embodiments, the battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0156] 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.

[0157] The present application has no particular limitation on the shape of the battery, which can be cylindrical, square, or any other shape. For example, FIG3 shows a battery cell 5 with a square structure as an example.

[0158] In some embodiments, referring to Figure 4, 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.

[0159] 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.

[0160] Figure 5 shows an example battery module 4. Referring to Figure 5 , 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.

[0161] 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.

[0162] 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.

[0163] Figures 6 and 7 illustrate an example battery pack 1. Referring to Figures 6 and 7 , 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.

[0164] In a second aspect of the present application, the present application proposes a method for preparing the aforementioned battery, referring to FIG9 and FIG10 , comprising:

[0165] S100: Mixing and stirring the emulsifier, initiator, and monomers constituting the first polymer, and heating the mixture for reaction

[0166] In some embodiments, the emulsifier, initiator, and monomers constituting the first polymer are blended and stirred in a mass ratio of (2-10):(0.2-1):100, and heated for reaction, thereby obtaining a first polymer emulsion through emulsion polymerization, and the yield of the first polymer can be increased.

[0167] 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.

[0168] 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.

[0169] An initiator is a substance that can initiate polymerization of monomers. For example, free radical initiators, which are compounds that readily decompose into free radicals (i.e., primary free radicals) upon exposure to heat, can be used to initiate free radical polymerization and copolymerization of olefinic and diene monomers.

[0170] In some embodiments, the 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.

[0171] In some embodiments, the initiator may include at least one of the following: a persulfate initiator including at least one of potassium persulfate and ammonium persulfate; an acyl peroxide initiator including at least one of benzoyl peroxide and dioctanoyl peroxide; and an azo initiator including at least one of azobisisobutyronitrile and dimethyl azobisisobutyrate.

[0172] In some embodiments, the constituent monomers of the first polymer may include the aforementioned first monomer, second monomer, and third monomer, wherein the mass ratio of the first monomer, the second monomer, and the third monomer may be 100:(1-50):(10-40), so that the first polymer has better adhesion while combining the respective advantages of the first monomer, the second monomer, and the third monomer.

[0173] S200: Mixing and stirring the emulsifier, initiator, and monomers constituting the second polymer

[0174] In some embodiments, the emulsifier, initiator, and monomers constituting the second polymer are blended and stirred in a mass ratio of (2-10):(0.2-1):100 to obtain a second polymer emulsion by emulsion polymerization, and the yield of the second polymer can be increased.

[0175] In some embodiments, the constituent monomers of the second polymer include a fourth monomer.

[0176] In some embodiments, the second polymer emulsion satisfies at least one of the following conditions: a solid content of the second polymer emulsion is 30%-60%; and a viscosity of the second polymer emulsion at 25° C. is 10 mPa·s-300 mPa·s.

[0177] In some embodiments, the emulsifier may include at least one of sodium fatty acid and sodium disproportionated rosin acid.

[0178] In some embodiments, the initiator may include at least one of p-menthane hydroperoxide, pinane hydroperoxide, and dicumyl peroxide.

[0179] In some embodiments, the emulsifier and initiator used in preparing the second polymer emulsion can refer to the substances used in preparing the first polymer emulsion, and will not be described in detail here.

[0180] When the viscosity and solid content of the second polymer emulsion are within the aforementioned ranges, it is beneficial to the ejection of the polymer emulsion during the granulation process, thereby improving the effect of the granulation process.

[0181] 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.

[0182] S300: The first polymer emulsion and the second polymer emulsion are mixed and stirred, and the polymer is obtained by spray drying.

[0183] In some embodiments, in this step, after the first polymer emulsion and the second polymer emulsion prepared above are mixed, they are spray-dried to form polymer particles with a moderate particle size.

[0184] When polymer materials are synthesized by emulsion polymerization, the particle size of the polymer spheres in the emulsion polymer is usually nanometer-scale. If it is directly scraped onto the base film, pore blockage or insufficient adhesion may occur due to the small particle size of the polymer spheres. A polymer composed of the first polymer and the second polymer is obtained through granulation treatment, such as spray drying.

[0185] Spray drying, through mechanical action, disperses the material to be dried (a mixture of the first polymer emulsion and the second polymer emulsion) into very fine mist-like particles (increasing the water evaporation area and accelerating the drying process). Most of the water is removed at the moment of contact with hot air, and the solid matter in the material is dried into powder.

[0186] In some embodiments, the method further comprises, before spray drying, adding a tackifying resin to the spray slurry, wherein the mass fraction of the tackifying resin in the spray slurry is 1%-20%.

[0187] As an example, the mass fraction of the tackifying resin in the spray slurry can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0188] In some embodiments, the viscosity of the tackifying resin at 25° C. is 100 mPa·s to 5000 mPa·s.

[0189] S400: Disposing a polymer on at least one side of the base film

[0190] In some embodiments, the polymer may be dissolved in a solvent to prepare a slurry, which is then sprayed onto at least one surface of the base film and dried to remove the solvent, thereby obtaining the isolation film.

[0191] In some embodiments, the polymer may be disposed on opposite surfaces of the base film.

[0192] S500: The side of the separator provided with the polymer is arranged opposite to the side of the negative electrode plate provided with the negative electrode active material layer.

[0193] In some embodiments, since the binder in the negative electrode active material layer and part of the polymer are composed of the same substance, by arranging the side of the isolation membrane where the polymer is provided and the side of the negative electrode plate where the negative electrode active material layer is provided opposite to each other, the bonding performance between the negative electrode plate and the isolation membrane can be further improved after the two are in contact with each other.

[0194] Those skilled in the art will understand that, in the above-mentioned method of a specific embodiment, 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.

[0195] In a third aspect of the present application, an electrical device is provided, comprising the aforementioned battery and / or a battery prepared using the aforementioned method. Thus, the electrical device possesses all the features and advantages of the aforementioned battery and method for preparing the battery, and further description thereof is omitted.

[0196] The electrical device includes at least one of the batteries, battery modules, or battery packs provided in this application. The batteries, battery modules, or battery packs can be used as a power source for the electrical device or as an energy storage unit for the electrical device.

[0197] In some embodiments, electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (refer to Figure 8, 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 and satellites, energy storage systems, etc., but are not limited to these.

[0198] As an electrical device, a battery, battery module or battery pack can be selected according to its usage requirements.

[0199] 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.

[0200] Example 1

[0201] 1. Preparation of polymer

[0202] (1) Preparation of the first polymer emulsion

[0203] Weigh 1000g of the first monomer, ethyl acrylate, the second monomer, and the third monomer, acrylamide, respectively, in a mass ratio of 100:25:20. Mix the monomers thoroughly. Add 1000g of the mixed monomers, 32g of the emulsifier sodium dodecylbenzenesulfonate, 10g of the initiator potassium persulfate, and 1200g of deionized water to a 5L four-necked flask equipped with a mechanical stirrer, a thermometer, and a condenser. Emulsify at high speed for 30 minutes. Under nitrogen, heat to 80°C, react for 4 hours, cool to below 40°C, adjust the pH to neutral, and filter the product. This yields a first polymer emulsion.

[0204] (2) Preparation of the second polymer emulsion

[0205] A total of 100 g of the fourth monomer of butadiene and styrene with a mass ratio of 70:30 was weighed, and in a 1L stainless steel polymerization kettle, 180 g of deionized water, 1.5 g of emulsifier sodium fatty acid, 0.06 g of initiator para-menthane hydroperoxide, and 0.02 g of electrolyte potassium chloride were added. The mixture was stirred for 20 minutes, and then 30 g of styrene monomer was added. The kettle was covered, nitrogen was introduced to replace the air in the kettle, and then vacuumed. 70 g of butadiene was added under vacuum, and a circulating cold bath was started. The polymerization reaction temperature was controlled at 5°C. After reacting for 5 hours, stirring was stopped and the second polymer emulsion was obtained after venting.

[0206] (3) According to the weight ratio of the first polymer to the second polymer being 100:30, the first polymer emulsion and the second polymer emulsion were weighed, stirred and mixed evenly, and then the adhesive for the isolation film was prepared by a spray drying process. The conditions of the spray drying process were: inlet air temperature of 110°C, outlet air temperature of 50°C, and air pressure of 0.5 kPa.

[0207] 2. Preparation of batteries

[0208] (1) Preparation of isolation membrane

[0209] 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 membrane. The polymer prepared as described 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 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.

[0210] (2) Preparation of positive electrode sheet

[0211] 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.

[0212] (3) Preparation of negative electrode sheet

[0213] 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 (solid content 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.

[0214] (4) Preparation of electrolyte

[0215] 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.

[0216] (5) Battery assembly

[0217] 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.

[0218] The differences between Examples 2-24 and Comparative Examples 1-3 and Example 1 are shown in Tables 1-1 and 1-2. Examples 15-20 differ from Example 1 in that a tackifying resin is added to the mixture of the first polymer emulsion and the second polymer emulsion before spray drying. Examples 21 and 22 differ from Example 1 in the mass ratio of the first polymer to the second polymer. Examples 23 and 24 differ from Example 1 in that only the first and third monomers are used in Example 23, and only the first and second monomers are used in Example 24. The total monomer mass in Examples 23 and 24 remains the same as in Example 1.

[0219] The difference between Comparative Example 1 and Example 1 is that polyacrylic acid is selected as the binder when preparing the negative electrode slurry.

[0220] The difference between Comparative Example 2 and Example 1 is that only the first polymer emulsion is used to prepare the polymer.

[0221] The difference between Comparative Example 3 and Example 1 is that only the second polymer emulsion is used to prepare the polymer.

[0222] Table 1-1

[0223] Table 1-2

[0224] The adhesion test was conducted on the separators, positive electrode sheets, and negative electrode sheets in Examples 1-24 and Comparative Examples 1-3. The test results are shown in Table 2. The test conditions are as follows:

[0225] The electrode and separator were overlapped and placed on a hot press. The press parameters were set at 25°C, 7t pressure, and 15s. Bonded separator / electrode samples were obtained. The separator / electrode samples were cut into 150mm x 20mm rectangular strips. The electrode side of the strips was attached to a steel plate using double-sided tape. At one end of the strips, the separator and electrode were separated by 2cm along the length to produce test specimens. 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 20mm / min and a horizontal pull of 10cm. 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 bond strength between the separator and electrode.

[0226] The batteries in Examples 1-24 and Comparative Examples 1-3 were subjected to cycle performance tests. The test results are shown in Table 2. The test conditions are as follows:

[0227] 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 2.5V. The obtained discharge capacity was recorded as the initial capacity C0. Repeat the above steps for the same battery and record the discharge capacity Cn of the battery after the nth cycle at the same time. The battery capacity retention rate P after each cycle is n =(C n / C0)×100%. The difference in cycle performance can be reflected by the battery capacity retention rate after 500 cycles.

[0228] Table 2

[0229] In Examples 1-24, by optimizing the composition of the polymer in the adhesive coating on the isolation membrane, while making the isolation membrane have better adhesion to the electrode, the bonding performance between the isolation membrane and the negative electrode is further effectively improved by matching the polymer with the binder in the negative electrode active material layer, so that the bonding force between the isolation membrane and the positive electrode and the negative electrode is better, and the difference between the two is small, thereby effectively alleviating the poor bonding between the negative electrode and the isolation membrane, and the positive electrode, the negative electrode and the isolation membrane are bonded to each other and support each other, thereby improving the wettability of the electrode to the electrolyte, the internal resistance of the battery is low, and the volume expansion of the negative electrode during the lithium insertion and extraction process is effectively suppressed, and the cycle performance of the battery is effectively improved.

[0230] In Comparative Example 1, since a binder that does not contain a butadiene copolymer is used in the negative electrode active material layer, the bonding strength between the second polymer and the binder in the negative electrode active material layer cannot be improved. The bonding strength between the negative electrode active material layer and the separator is too weak, and the volume expansion of the negative electrode plate during lithium insertion and extraction cannot be effectively suppressed. The plate has poor wettability to the electrolyte, and the battery cycle performance is poor.

[0231] In Comparative Example 2, the polymer on the surface of the base film does not contain the first polymer. Although the bonding force between the isolation membrane and the positive electrode sheet and the negative electrode sheet is slightly different, the bonding force between the isolation membrane and the positive electrode sheet and the negative electrode sheet is poor. The positive electrode sheet, the negative electrode sheet and the isolation membrane cannot adhere to each other and support each other, resulting in a loose battery, lower hardness, a significant increase in the internal resistance of the battery, poor wettability of the electrode to the electrolyte, and poor battery cycle performance.

[0232] In Comparative Example 3, since the polymer on the surface of the base film does not contain the second polymer, the bonding force between the polymer and the butadiene copolymer in the negative electrode active material layer cannot be improved. The bonding force between the negative electrode active material layer and the isolation membrane is too small, and the volume expansion of the negative electrode plate during the lithium insertion and extraction process cannot be effectively suppressed. The plate has poor wettability to the electrolyte, and the battery cycle performance is poor.

[0233] 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 battery, wherein: include: A negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active material layer at least located on one side of the negative electrode current collector, the negative electrode active material layer comprising a binder, and the binder comprising a butadiene copolymer; A separator, the separator comprising a base film and a polymer at least on one side of the base film, the side of the separator provided with the polymer being arranged opposite to the side of the negative electrode sheet provided with the negative electrode active material layer, The polymer includes a first polymer and a second polymer, the first polymer includes an acrylic ester copolymer, and the second polymer includes a butadiene copolymer.

2. The battery according to claim 1, wherein The monomer of the first polymer and the derivative of the monomer of the first polymer include at least a first monomer, and the structure of the first monomer is shown in Formula 1: Wherein, R1 includes a hydrogen atom or a C1-C6 alkyl group, and R2 includes a substituted or unsubstituted C1-C 15 alkyl, substituted or unsubstituted C3-C6 isobornyl, wherein the C1-C 15 Substituents of the alkyl group include hydroxyl or C1-C6 alkyl.

3. The battery according to claim 2, wherein 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, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

4. The battery according to any one of claims 1 to 3, wherein: The monomer of the first polymer and the derivative of the monomer of the first polymer further include a second monomer, and the structure of the second monomer is shown in Formula 2 and / or Formula 3: and / or, Wherein, R3 includes hydrogen atom or C1-C 18 R4 includes a hydrogen atom or a C1-C6 alkyl group.

5. The battery according to claim 4, wherein The second monomer includes at least one of acrylonitrile, methacrylonitrile, ethacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid.

6. The battery according to any one of claims 1 to 5, wherein: The monomer of the first polymer and the derivative of the monomer of the first polymer further include a third monomer, and the structure of the third monomer is shown in Formula 4: Among them, R5 includes a hydrogen atom, a C1-C6 alkyl group or a C1-C6 alkoxy group substituted with a hydroxyl group, and R6 includes a hydrogen atom or a C1-C6 alkyl group.

7. The battery according to claim 6, wherein The third monomer includes at least one of acrylamide, N-methylol acrylamide and N-butoxymethyl acrylamide.

8. The battery according to any one of claims 1 to 7, wherein: The monomer of the second polymer and the derivative of the monomer of the second polymer include at least a fourth monomer, and the structure of the fourth monomer is shown in Formula 5: Among them, R7, R8, R9, R 10 Each independently includes a hydrogen atom, a phenyl group, an alkenyl group, a cyano group, and a linear or branched alkyl group.

9. The battery according to claim 8, wherein The fourth monomer includes butadiene, and further includes at least one of styrene, acrylonitrile, isoprene, and propylene.

10. The battery according to claim 8 or 9, wherein The second polymer includes at least one of styrene butadiene copolymer, acrylonitrile butadiene copolymer, butadiene isoprene copolymer, and butadiene propylene copolymer.

11. The battery according to any one of claims 1 to 10, wherein: The Dv50 particle size of the primary particles of the first polymer is 100 nm-200 nm, and / or the Dv50 particle size of the primary particles of the second polymer is 100 nm-200 nm.

12. The battery according to any one of claims 1 to 11, wherein: The polymer has a Dv50 particle size of 1 μm to 18 μm.

13. The battery according to any one of claims 1 to 12, wherein: The mass of the first polymer in the polymer is m1, the mass of the second polymer in the polymer is m2, and m1:m2 is 100:(1-100).

14. The battery according to claim 13, wherein It further comprises: a tackifying resin, wherein the mass of the tackifying resin in the polymer is m3, and m1:m3 is 100:(1-15).

15. The battery according to claim 14, wherein The tackifying resin satisfies at least one of the following conditions: The tackifying resin includes at least one of rosin resin, terpene resin and synthetic resin; The number average molecular weight of the tackifying resin is 5000-50000.

16. The battery according to any one of claims 1 to 15, wherein: The polymer further comprises: a positive electrode sheet, the separator is located between the positive electrode sheet and the negative electrode sheet, the bonding force between the separator and the positive electrode sheet is a, the bonding force between the separator and the negative electrode sheet is b, (a:b)≤(5:1); Preferably, (a:b)≤(2:1).

17. A method for preparing a battery according to any one of claims 1 to 16, wherein: include: The emulsifier, the initiator, and the monomers constituting the first polymer are mixed and stirred in a mass ratio of (2-10):(0.2-1):100, and heated for reaction to obtain a first polymer emulsion; The emulsifier, the initiator, and the monomers constituting the second polymer are mixed and stirred in a mass ratio of (2-10):(0.2-1):100 to obtain a second polymer emulsion; The first polymer emulsion and the second polymer emulsion are mixed and stirred, and spray-dried to obtain the polymer; Disposing the polymer on at least one side of a base film to obtain a release film; The side of the separator provided with the polymer is arranged opposite to the side of the negative electrode plate provided with the negative electrode active material layer.

18. The method according to claim 17, wherein: The constituent monomers of the first polymer include a first monomer, a second monomer, and a third monomer, wherein the mass ratio of the first monomer, the second monomer, and the third monomer is 100:(1-50):(10-40).

19. The method according to claim 17 or 18, wherein: The constituent monomers of the second polymer include a fourth monomer.

20. The method according to any one of claims 17 to 19, wherein: The second polymer emulsion satisfies at least one of the following conditions: The solid content of the second polymer emulsion is 30%-60%; The viscosity of the second polymer emulsion at 25° C. is 10 mPa·s to 300 mPa·s.

21. The method according to any one of claims 17 to 20, wherein: The method further comprises before the spray drying: adding a tackifying resin to the spray slurry, wherein the mass fraction of the tackifying resin in the spray slurry is 1%-20%.

22. The method according to claim 21, wherein: The viscosity of the tackifying resin at 25° C. is 100 mPa·s-5000 mPa·s.

23. An electrical device, wherein: A battery comprising the battery described in any one of claims 1 to 16, and / or a battery prepared by the method described in any one of claims 17 to 22.

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