Battery, method for preparing battery and power utilization device

Abstract

The invention discloses a battery, a method for preparing the battery and a power utilization device, the battery comprises a negative electrode plate, the negative electrode plate comprises 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 comprises a binder, and the binder comprises a butadiene copolymer; the isolating membrane comprises a base membrane and a polymer at least located on one side of the base membrane, the side, provided with the polymer, of the isolating membrane is opposite to the side, provided with the negative active material layer, of the negative pole piece, and the polymer comprises a first polymer and a second polymer; the first polymer comprises an acrylate copolymer, and the second polymer comprises a butadiene copolymer. Therefore, the binding power between the isolating membrane and the negative pole piece can be effectively improved, and the structural stability of the battery in the charge-discharge cycle process is improved.

Description

Technical Field

[0001] The present application 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 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. In batteries, the amount and cost of binders are relatively small, but they can effectively improve battery performance and are an indispensable and important component of batteries. As an inactive material in the battery, the binder can bond the components in the battery and adjacent parts together, reduce the expansion and shedding of active materials during the battery charging and discharging process, and reduce the internal resistance of the battery. However, there are still problems such as insufficient bonding force in current batteries, which need to be further improved.

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

[0004] In the first aspect of the present application, 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 at least located on one side of the negative electrode current collector, the negative electrode active material layer comprising a binder, the binder comprising a butadiene copolymer; a separator, the separator comprising a base film and a polymer at least located on one side of the base film, the separator having a side provided with the polymer and a side provided with the negative electrode active material layer arranged opposite to the negative electrode plate, the polymer comprising a first polymer and a second polymer, the first polymer comprising an acrylate copolymer, the second polymer comprising a butadiene copolymer. Thus, the bonding force between the separator and the negative electrode plate can be effectively improved, and the structural stability of the battery during the charge and discharge cycle can be improved.

[0005] 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:

[0006]

[0007] 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 The 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]

[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 performance 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]

[0015] 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. Thus, the formation of the first polymer is facilitated and the molecular weight of the first polymer is adjusted.

[0016] 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.

[0017] In some embodiments, 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:

[0018]

[0019] Among them, R7, R8, R9, R 10 Each of the above groups independently includes a hydrogen atom, a phenyl group, an alkenyl group, a cyano group, and a linear or branched alkyl group. Thus, the alkali resistance and adhesion of the second polymer can be improved.

[0020] 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.

[0021] In some embodiments, the second polymer includes at least one of styrene butadiene copolymer, acrylonitrile butadiene copolymer, butadiene isoprene copolymer, and butadiene propylene copolymer. Thus, the bonding force between the negative electrode plate and the separator can be further improved.

[0022] In some embodiments, 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. Thus, the bonding performance of the first polymer and the second polymer can be improved.

[0023] In some embodiments, the Dv50 particle size of the polymer is 1 μm-18 μm, thereby reducing the pore blocking of the base film by the polymer.

[0024] 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). Thus, the adhesion of the polymer can be further improved.

[0025] In some embodiments, the polymer further comprises: a tackifying resin, the mass of the tackifying resin in the polymer is m3, and m1:m3 is 100:(1-15). Thus, the initial viscosity of the polymer can be improved.

[0026] 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 5000-50000. Thus, the initial viscosity of the polymer can be further improved.

[0027] 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). Thus, the structural stability of the battery during the charge and discharge process can be improved.

[0028] In the second aspect of the present application, the present application proposes a method for preparing the aforementioned battery, comprising: mixing and stirring an emulsifier, an initiator, and a first polymer constituent monomer according to a mass ratio of (2-10): (0.2-1): 100, and heating the mixture to react to obtain a first polymer emulsion; mixing and stirring an emulsifier, an initiator, and a second polymer constituent monomer according to a mass ratio of (2-10): (0.2-1): 100 to obtain a second polymer emulsion; mixing and stirring the first polymer emulsion and the second polymer emulsion, and spray drying to obtain the polymer; setting the polymer on at least one side of the base film to obtain a separator; setting the side of the separator provided with the polymer opposite to the side of the negative electrode sheet provided with the negative electrode active material layer. Thus, the aforementioned battery can be obtained by a simple method.

[0029] In some embodiments, 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). Thus, a first polymer with better adhesion can be obtained.

[0030] In some embodiments, the constituent monomers of the second polymer include the fourth monomer, thereby obtaining a second polymer having better adhesion.

[0031] In some embodiments, 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-300 mPa·s. This helps to obtain a polymer with a moderate particle size through spray drying.

[0032] In some embodiments, before the spray drying, the method further comprises: adding a tackifying resin to the spray slurry, 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.

[0033] In some embodiments, the viscosity of the tackifying resin at 25° C. is 100 mPa·s to 5000 mPa·s. In this way, the adhesion of the polymer can be further improved.

[0034] In the third aspect of the present application, the present application proposes an electrical device, including the aforementioned battery, and / or a battery prepared by the aforementioned method. Therefore, the electrical device has all the features and advantages of the aforementioned battery and the method for preparing the battery, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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:

[0036] Figure 1 is a schematic structural diagram of a battery according to one embodiment of the present application;

[0037] Figure 2 is a schematic structural diagram of a battery according to another embodiment of the present application;

[0038] Figure 3 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0039] Figure 4 yes Figure 3 An exploded view of a battery cell according to an embodiment of the present application is shown;

[0040] Figure 5 is a schematic diagram of a battery module according to an embodiment of the present application;

[0041] Figure 6 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0042] Figure 7 yes Figure 6 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0043] Figure 8 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application;

[0044] Fig. 9 It is a partial schematic diagram of a method for preparing a battery according to one embodiment of the present application;

[0045] Fig.10 It is a schematic flow chart of a method for preparing a battery according to one embodiment of the present application.

[0046] Description of reference numerals:

[0047] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell;

[0048] 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

[0049] The embodiments of the present application are described in detail below, and 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 cannot be understood as limiting the present application.

[0050] 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 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).

[0051] The terms "including" and "having" in the specification and claims of the present application and any modifications thereof are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0052] " Scope " disclosed in the present application is limited in the form of lower limit and upper limit, and a 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 a special range. The scope limited in this way can be to include end values ​​or not include end values, and can be combined arbitrarily, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for a particular parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 listed, and if the maximum range values ​​3,4 and 5 are listed, the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present 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 real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it 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.

[0053] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0054] 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.

[0055] 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 indicating the number of the indicated technical features. "First feature" and "second feature" may include one or more of the features.

[0056] In the description of the present 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 examples and may be any technical feature connected by "and / or" in the present application.

[0057] 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.

[0058] Typically, a battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the battery charge and discharge process, active ions are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes of the battery from short-circuiting, while allowing ions to pass through.

[0059] An adhesive needs to be provided 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, and a structure with a certain thickness has a certain hardness. The negative electrode sheet will expand during the charging and discharging process. If the bonding force is weak, a gap will form between the positive electrode sheet, the negative electrode sheet and the separator. The positive electrode sheet, the negative electrode sheet 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 sheet 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 makes it impossible for the binder added in the negative electrode active material layer to produce a relatively strong bonding force 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 usually has a high packing density, which makes the gap 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 the 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, which ultimately leads to poor bonding of the negative electrode active material layer and poor bonding between the negative electrode plate and the separator. Therefore, by improving the bonding performance between the separator and the negative electrode plate, the poor bonding 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.

[0060] 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, in the negative electrode active material layer formed by the negative electrode slurry, part of the binder 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.

[0061] Binder refers to a material with adhesive properties that is used to bond different substances together.

[0062] 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.

[0063] In a first aspect of the present application, the present application proposes a battery, referring to Figure 1 , including: a negative electrode plate, the negative electrode plate includes a negative electrode current collector 11 and a negative electrode active material layer 12 at least located on one side of the negative electrode current collector, the negative electrode active material layer 12 includes a binder, and the binder includes a butadiene copolymer; a separator, the separator includes a base film 31 and a polymer 32 at least located on one side of the base film, the side of the separator provided with the polymer 32 is arranged opposite to the side of the negative electrode plate provided with the negative electrode active material layer 12, the polymer includes a first polymer and a second polymer, the first polymer includes an acrylate copolymer, and the second polymer includes a butadiene copolymer. By using the first polymer and the second polymer in combination, the bonding force of the polymer itself can be improved, for example, the bonding force between the polymer and the base film, and the bonding performance between the separator and the negative electrode plate can be improved.

[0064] Butadiene copolymers have the characteristics of strong alkali resistance, soft film formation, good air permeability, strong bonding force, etc., and have good mechanical stability and chemical stability when used as a binder in the negative electrode active material layer.

[0065] 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).

[0066] In some embodiments, the base film may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, and non-woven fabrics.

[0067] 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.

[0068] 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).

[0069] 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.

[0070] The polymer on the surface of the isolation membrane is a secondary particle formed by the aggregation of the primary particles of the first polymer and the 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 regulated. The appropriate amount of the first polymer exposed on the surface of the secondary particles can improve the adhesion of the polymer on the surface of the isolation membrane. The appropriate amount of the second polymer exposed on the surface of the secondary particles can be combined with the butadiene copolymer in the negative electrode active material layer to improve the adhesion between the isolation membrane and the negative electrode plate.

[0071] 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:

[0072]

[0073] Wherein, R1 includes a hydrogen atom or a C1-C6 alkyl group, and R2 includes a 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.

[0074] In the manufacturing process of the battery, a hot pressing process or a cold pressing process is required to make the isolation film and the pole piece bond tightly. The first monomer includes an unsaturated ester group, which is conducive to the polymerization of the monomer, and the soft and hard monomers in the ester monomer can form the skeleton of the first polymer molecular chain segment through polymerization, so that the first polymer has excellent stability and good adhesion, and at the same time helps to improve the anti-swelling performance of the first polymer.

[0075] 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.

[0076] 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.

[0077] By using any one or more of the above first monomers, the adhesive property and anti-swelling property of the first polymer can be adjusted.

[0078] 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:

[0079]

[0080] Wherein, R3 includes hydrogen atom or C1-C 18 R4 includes a hydrogen atom or a C1-C6 alkyl group.

[0081] 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 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.

[0082] In some embodiments, the second monomer includes at least one of acrylonitrile, methacrylonitrile, ethacrylonitrile, acrylic acid, methacrylic acid, butenoic acid, and heptenoic acid.

[0083] By using any one or more of the above second monomers, the bonding properties of the first polymer can be adjusted, wherein the monomer containing a cyano group can also improve the ionic conductivity of the first polymer.

[0084] 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:

[0085]

[0086] 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.

[0087] 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.

[0088] In some embodiments, the third monomer includes at least one of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide.

[0089] Using any one or more of the 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.

[0090] Test of ester, carboxyl, acrylamide, carbonyl, amide and cyano groups in organic polymer structure: Test according to the national standard GB / T 6040-2002 General Rules for Infrared Spectroscopy Analysis Methods. Use the tablet transmission method to press the sample into KBr tablets, and deduct the KBr background blank by the transmission method to obtain the sample test spectrum (resolution: 4cm -1 , wave number range: 400cm -1 -4000cm -1 ).

[0091] In some embodiments, 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:

[0092]

[0093] 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.

[0094] 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 bonding force of the second polymer.

[0095] In some embodiments, the fourth monomer includes butadiene, and further includes at least one of styrene, acrylonitrile, isoprene, and propylene.

[0096] By using any one or more of the fourth monomers mentioned above, the alkali resistance and adhesion of the second polymer can be improved.

[0097] In some embodiments, the second polymer includes at least one of styrene butadiene copolymer, acrylonitrile butadiene copolymer, butadiene isoprene copolymer, butadiene propylene copolymer.

[0098] The use of at least one of the above-mentioned butadiene copolymers can effectively improve the bonding performance between the isolation membrane and the negative electrode plate.

[0099] In some embodiments, the binder in the negative active material layer may have the same chemical composition as the second polymer.

[0100] 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.

[0101] As an example, the Dv50 particle size of the primary particles of the first polymer can be 100nm, 105nm, 110nm, 115nm, 120nm, 125nm, 130nm, 135nm, 140nm, 145nm, 150nm, 155nm, 160nm, 165nm, 170nm, 175nm, 180nm, 185nm, 190nm, 195nm or 200nm.

[0102] As an example, the Dv50 particle size of the primary particles of the second polymer can be 100nm, 105nm, 110nm, 115nm, 120nm, 125nm, 130nm, 135nm, 140nm, 145nm, 150nm, 155nm, 160nm, 165nm, 170nm, 175nm, 180nm, 185nm, 190nm, 195nm or 200nm.

[0103] The particle size of polymer beads in emulsion polymers is usually nanometer-level. 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 polymer materials are synthesized by emulsion polymerization, granulation treatment can be used to obtain granular polymer materials, which helps to obtain polymers with a particle size of micrometer level.

[0104] In some embodiments, the polymer has a Dv50 particle size of 1 μm to 18 μm.

[0105] 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.

[0106] The polymer particles are secondary particles formed by agglomerating primary particles of a first polymer and primary particles of a second polymer. In this way, the first polymer acts as a skeleton to provide the polymer with higher bonding force and structural stability, and the second polymer forms a binding force with the functional groups of the binder in the negative electrode active material layer to improve the bonding effect between the isolation membrane and the negative electrode plate.

[0107] It is understandable 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 secondary particles of the polymer after spray drying.

[0108] When the Dv50 particle size of the polymer is within the aforementioned range, it can not only improve the problem of polymer blocking the pores of the base membrane and increase the permeability of metal active ions on the isolation membrane, but also improve the problem of affecting the battery energy density due to the thick coating formed by the polymer coating on the base membrane.

[0109] The Dv50 particle size indicates that among the sample particles, 50% of the total volume of the particles have a particle size greater than this value, and another 50% of the total volume of the particles have a particle size less than this value; Dv50 can represent the median particle size of the sample.

[0110] The volume particle size distribution Dv50 of the polymer can be tested by a method known in the art. As an example, GB / T 19077-2016 can be referred to, and a Malvern laser particle size analyzer can be used for characterization testing, such as a Malvern Mastersizer-3000 or other instrument.

[0111] 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 can be measured by a laser particle size analyzer.

[0112] 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).

[0113] As an example, m1:m3 may be 100:1, 100:5, 100:7, 100:9, 100:10, 100:12, or 100:15.

[0114] When two polymer materials are in 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 occur between the atoms and molecules in adjacent polymers. For polymers, their viscosity is affected by dispersion forces, self-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 surface of the first polymer and the second polymer, and the polymer chain segments have high mobility. Since the initial viscosity of the polymer has a strong correlation with the activity of the polymer chain segments, the polymer can quickly wet the contacting surface under a small external pressure, achieving molecular-level contact, so that countless intermolecular forces produce sufficient bonding strength, and the overall bonding performance of the polymer is significantly improved.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] The chain diffusion and chain entanglement of the polymer material are related to its 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 the chain segments, and the strength after entanglement is relatively high.

[0119] In some embodiments, the battery may further include: a positive electrode plate, a separator located between the positive electrode plate and the negative electrode plate, the bonding force between the separator and the positive electrode plate is a, the bonding force between the separator and the negative electrode plate is b, (a:b)≤(5:1).

[0120] As examples, (a:b) can be 5:1, 4:1, 3:1, 2:1, or 1:1.

[0121] 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 and support each other, which helps the battery maintain structural stability, making the electrode sheet more wettable to the electrolyte and improving the battery's cycle performance.

[0122] The bonding force between the isolation film and the pole piece can be tested by methods known in the art. As an example, the pole piece and the isolation film can be overlapped and placed on a hot press. The parameters of the hot press are set as follows: temperature is 25°C, pressure is 7t, time is 15s, and the bonding isolation film / pole piece sample is obtained by pressing; the isolation film / pole piece sample is cut into a rectangular spline of 150mm×20mm. The pole piece side of the above rectangular spline is pasted on the steel plate by double-sided tape, and the isolation film and the pole piece are separated by a length of 2cm in the length direction at one end of the rectangular spline to obtain a test specimen. Keep the steel plate horizontal and fix it with the lower clamp of the universal testing machine (Xie Qiang Instrument Manufacturing (Shanghai) Co., Ltd., Model CTM2100), fix the peeled end of the isolation film as described above with the upper clamp of the universal testing machine, and connect it to the tensile machine. Set the test conditions to a tensile rate of 20mm / min and a horizontal pull of 10cm. After the tension is stable, 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.

[0123] [Positive electrode]

[0124] As an example, refer to Figure 2 The positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer 22 is disposed on any one or both of the two opposite surfaces of the positive electrode current collector 21 .

[0125] 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.).

[0126] 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.

[0127] 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 NCM811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of lithium-containing phosphates with olivine structure may include, but are not limited to, 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 doping modification and / or surface coating modification of the materials.

[0128] The battery will be accompanied by Li deintercalation and consumption during the charge and discharge process, and the molar content of Li is different when the battery is discharged to different states. In the list of positive electrode active materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li will change after the charge and discharge cycle.

[0129] In some embodiments, when the battery is a sodium ion battery, the positive electrode active material may be a positive electrode active material for a sodium ion battery known in the art.

[0130] As an example, the positive electrode active material may include at least one of the following materials: sodium transition metal oxides, polyanion compounds, and Prussian blue sodium compounds 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 can also be used. The modified compounds of the above materials can be doping modification and / or surface coating modification of the materials.

[0131] 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.

[0132] 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 state.

[0133] In some embodiments, the polyanionic compound may 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.

[0134] In some embodiments, the polyanionic compound may also be a compound having sodium ions, tetrahedral (YO4) n- Anion unit, polyhedral 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, and m represents (ZO y ) m+ The halogen may include at least one of F, Cl, and Br.

[0135] As an example, the polyanionic compound may satisfy the chemical formula NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, referred to 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).

[0136] 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.

[0137] 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.

[0138] The battery will be accompanied by Na deintercalation and consumption during the charge and discharge process, and the molar content of Na is different when the battery is discharged to different states. In the list of positive electrode active materials in this application, the molar content of Na is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Na will change after the charge and discharge cycle.

[0139] In the list of positive electrode active materials in this application, the molar content of O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

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

[0141] 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.

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

[0143] 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.

[0144] In some embodiments, the positive electrode sheet can be prepared in the following manner: 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.

[0145] [Negative electrode]

[0146] 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.

[0147] 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 disposed on any one or both of the two facing surfaces of the negative electrode current collector.

[0148] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one side 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.).

[0149] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery 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 oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials include at least one of elemental tin, tin oxide compounds, 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.

[0150] 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.

[0151] 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)).

[0152] In some embodiments, the negative electrode sheet can be prepared in the following manner: 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 collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0153] [Electrolytes]

[0154] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0155] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0156] 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 dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0157] In some embodiments, the solvent includes at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0158] In some embodiments, the electrolyte may further include additives, such as 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, additives that improve battery high or low temperature performance, etc.

[0159] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0160] In some embodiments, the battery may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0161] In some embodiments, the outer packaging of the battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0162] The present application has no particular limitation on the shape of the battery, which may be cylindrical, square or any other shape. Figure 3 The battery cell 5 is a square structure as an example.

[0163] In some embodiments, reference Figure 4, the outer packaging may include a shell 51 and a top cover assembly 53. Among them, 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 form 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.

[0164] 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 according to the application and capacity of the battery module.

[0165] Figure 5 4 is an example of a battery module. Figure 5 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0166] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0167] 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 according to the application and capacity of the battery pack.

[0168] Figure 6 and Figure 7 1 is a battery pack 1 as an example. Figure 6 and Figure 7 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0169] In the second aspect of the present application, the present application proposes a method for preparing the aforementioned battery, referring to Fig. 9 and Fig.10 ,include:

[0170] S100: Mix and stir the emulsifier, initiator, and monomers constituting the first polymer, and heat to react

[0171] In some embodiments, 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 to react, thereby obtaining a first polymer emulsion through emulsion polymerization, and the yield of the first polymer can be increased.

[0172] 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 the polymerization of the monomers.

[0173] Emulsifiers are a type of substance 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.

[0174] An initiator is a substance that can initiate polymerization of monomers. For example, a free radical initiator refers to a class of compounds that are easily decomposed into free radicals (i.e., primary free radicals) by heat, and can be used to initiate free radical polymerization and copolymerization of olefin and diene monomers.

[0175] 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.

[0176] In some embodiments, the initiator may include at least one of the following: a persulfate initiator includes at least one of potassium persulfate and ammonium persulfate; an acyl peroxide initiator includes at least one of benzoyl peroxide and dioctanoyl peroxide; an azo initiator includes at least one of azobisisobutyronitrile and dimethyl azobisisobutyrate.

[0177] 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.

[0178] S200: Mix and stir the emulsifier, initiator, and monomers constituting the second polymer

[0179] In some embodiments, the emulsifier, the initiator, and the monomers constituting the second polymer are blended and stirred in a mass ratio of (2-10):(0.2-1):100, thereby obtaining a second polymer emulsion through emulsion polymerization, and the yield of the second polymer can be increased.

[0180] In some embodiments, the constituent monomers of the second polymer include a fourth monomer.

[0181] In some embodiments, 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-300 mPa·s.

[0182] In some embodiments, the emulsifier may include at least one of sodium fatty acid and sodium disproportionated rosin acid.

[0183] In some embodiments, the initiator may include at least one of p-menthane hydroperoxide, pinane hydroperoxide, and dicumyl peroxide.

[0184] 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.

[0185] When the viscosity and solid content of the second polymer emulsion are within the aforementioned ranges, it is beneficial to the spraying of the polymer emulsion during the granulation process, thereby improving the effect of the granulation process.

[0186] As an example, the viscosity of the polymer emulsion can be tested using a rotary Brookfield viscometer, specifically, using a 62# rotor at 25°C.

[0187] S300: Mixing the first polymer emulsion and the second polymer emulsion and stirring them, spray drying them to obtain a polymer

[0188] In some embodiments, after the first polymer emulsion and the second polymer emulsion prepared above are mixed in this step, they are spray-dried to obtain polymer particles with a moderate particle size.

[0189] When a polymer material is synthesized by emulsion polymerization, the particle size of the polymer beads 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 beads. A polymer composed of the first polymer and the second polymer is obtained by a granulation process, such as spray drying.

[0190] 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), removes most of the water at the moment of contact with hot air, and dries the solid matter in the material into powder.

[0191] 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%.

[0192] 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%.

[0193] In some embodiments, the viscosity of the tackifying resin at 25° C. is 100 mPa·s to 5000 mPa·s.

[0194] S400: Disposing a polymer on at least one side of the base film

[0195] In some embodiments, the polymer may be dissolved in a solvent to prepare a slurry, and the slurry may be sprayed on at least one surface of the base film, and the isolation film may be obtained after drying to remove the solvent.

[0196] In some embodiments, the polymer may be disposed on opposite sides of the base film.

[0197] 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.

[0198] In some embodiments, since the binder in the negative electrode active material layer and part of the components in the polymer are the same substance, by arranging the side of the isolation membrane where the polymer is provided opposite to the side of the negative electrode pole piece where the negative electrode active material layer is provided, after the two are in contact with each other, the bonding performance between the negative electrode pole piece and the isolation membrane can be further improved.

[0199] Those skilled in the art will appreciate that, in the above method of a specific embodiment, the order in which the steps are written does not imply a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of the steps should be determined by their functions and possible internal logic.

[0200] In the third aspect of the present application, the present application proposes an electrical device, including the aforementioned battery, and / or a battery prepared by the aforementioned method. Therefore, the electrical device has all the features and advantages of the aforementioned battery and the method for preparing the battery, which will not be described in detail here.

[0201] The electric device includes at least one of the battery, battery module, or battery pack provided in the present application. The battery, battery module, or battery pack can be used as a power source for the electric device, or as an energy storage unit for the electric device.

[0202] In some embodiments, the power-consuming device may include a mobile device (e.g., a mobile phone, a laptop computer, etc.), an electric vehicle (see 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 not limited to these.

[0203] As an electrical device, a battery, a battery module or a battery pack can be selected according to its usage requirements.

[0204] The scheme of the present application is described below by specific examples. It should be noted that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are specified in the examples, the technology or conditions described in the literature in this area or the product instructions are used. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be obtained commercially.

[0205] Example 1

[0206] 1. Preparation of polymer

[0207] (1) Preparation of the first polymer emulsion

[0208] According to the mass ratio of the first monomer, the second monomer, and the third monomer of 100:25:20, weigh 1000g of the first monomer ethyl acrylate, the second monomer acrylonitrile, and the third monomer acrylamide respectively. Mix the monomers evenly. Add 1000g of mixed monomers, 32g of emulsifier sodium dodecylbenzene sulfonate, 10g of initiator potassium persulfate, and 1200g of deionized water to a 5L four-necked flask equipped with a mechanical stirrer, a thermometer, and a condenser, and stir and emulsify at high speed for 30min. Under nitrogen protection, heat to 80°C for 4h, cool to below 40°C, adjust the pH to neutral, and filter the material. Obtain the first polymer emulsion.

[0209] (2) Preparation of the Second Polymer Emulsion

[0210] Weigh a total of 100 g of the fourth monomer of butadiene and styrene in a mass ratio of 70:30, add 180 g of deionized water, 1.5 g of emulsifier sodium fatty acid, 0.06 g of initiator hydroperoxide, and 0.02 g of electrolyte potassium chloride into a 1L stainless steel polymerization kettle, stir for 20 minutes, then add 30 g of styrene monomer, cover the kettle, introduce nitrogen to replace the air in the kettle, then evacuate, add 70 g of butadiene under vacuum, start a circulating cold bath, control the polymerization reaction temperature at 5°C, react for 5 hours, stop stirring, and obtain a second polymer emulsion after venting.

[0211] (3) According to the weight ratio of the first polymer to the second polymer of 100:30, the first polymer emulsion and the second polymer emulsion were weighed, stirred and mixed evenly, and then spray-dried to obtain a binder for the isolation film. The conditions of the spray-drying process were: an inlet air temperature of 110° C., an outlet air temperature of 50° C., and an air pressure of 0.5 kPa.

[0212] 2. Preparation of batteries

[0213] (1) Preparation of isolation membrane

[0214] 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 film. The polymer prepared as described above was stirred and mixed evenly in deionized water to obtain a slurry (solid content of 20%). The slurry was sprayed on both surfaces of the base film and dried to remove the solvent. The coating density of the polymer on the base film was 1.5 g / m 2 , and obtain an isolation film.

[0215] (2) Preparation of positive electrode sheet

[0216] Polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive agent carbon black, and N-methylpyrrolidone (NMP) were mixed in a mass ratio of 1.2:58.38:0.42:40, and then stirred and mixed 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.

[0217] (3) Preparation of negative electrode sheet

[0218] 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 and mixed thoroughly to prepare negative electrode slurry (solid content 63%). 2 The loading amount is coated on the negative electrode collector copper foil, and then dried, cold pressed and cut to obtain the negative electrode sheet.

[0219] (4) Preparation of electrolyte

[0220] 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 mixed solvent to obtain an electrolyte, in which the concentration of LiPF6 is 1 mol / L.

[0221] (5) Battery assembly

[0222] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in order, and cold-pressed (during which the separator and the electrode sheet are bonded) to obtain a battery cell; the battery cell is placed in an outer package, and the above-prepared electrolyte is added. After packaging, standing, formation, aging and other processes, a battery is obtained.

[0223] The differences between Examples 2-24 and Comparative Examples 1-3 and Example 1 are shown in Tables 1-1 and 1-2, wherein 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. The difference between Examples 21 and 22 and Example 1 is the mass ratio of the first polymer to the second polymer; the difference between Examples 23 and 24 and Example 1 is that only the first monomer and the third monomer are used in Example 23, and only the first monomer and the second monomer are used in Example 24, and the total mass of the monomers in Examples 23 and 24 remains the same as that in Example 1.

[0224] The difference between Comparative Example 1 and Example 1 is that polyacrylic acid is selected as the binder when preparing the negative electrode slurry.

[0225] The difference between Comparative Example 2 and Example 1 is that only the first polymer emulsion is used to prepare the polymer.

[0226] The difference between Comparative Example 3 and Example 1 is that only the second polymer emulsion is used to prepare the polymer.

[0227] Table 1-1

[0228]

[0229]

[0230] Table 1-2

[0231]

[0232]

[0233] The isolation films, positive electrode sheets, and negative electrode sheets in Examples 1-24 and Comparative Examples 1-3 were subjected to adhesion tests. The test results are shown in Table 2. The test conditions are as follows:

[0234] The pole piece and the isolation film are overlapped and placed on a hot press. The parameters of the hot press are set as follows: temperature is 25°C, pressure is 7t, time is 15s, and the bonded isolation film / pole piece sample is obtained by pressing; the isolation film / pole piece sample is cut into a rectangular spline of 150mm×20mm. The pole piece side of the above rectangular spline is pasted on the steel plate by double-sided tape, and the isolation film and the pole piece are separated by a length of 2cm in the length direction at one end of the rectangular spline to obtain a test sample. The steel plate is kept horizontal and fixed with the lower clamp of the universal testing machine (Xieqiang Instrument Manufacturing (Shanghai) Co., Ltd., model CTM2100), and the peeled end of the isolation film as described above is fixed with the upper clamp of the universal testing machine and connected to the tensile machine. The test conditions are set to a tensile rate of 20mm / min and a horizontal pull of 10cm. After the tension is stable, the tension value is recorded, and the bonding force between the isolation film and the pole piece is obtained by the ratio of the tension value to the sample width.

[0235] The battery in Examples 1-24 and Comparative Examples 1-3 was subjected to a cycle performance test. The test results are shown in Table 2. The test conditions are as follows:

[0236] At 25°C, the prepared battery was charged to 3.65V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.65V, left for 5 minutes, and then discharged to 2.5V at 1 / 3C. The obtained discharge capacity was recorded as the initial capacity C0. The above steps were repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle was recorded at the same time. The battery capacity retention rate P after each cycle was n =(C n / C0)×100%. The battery capacity retention rate after 500 cycles can be used to reflect the difference in cycle performance.

[0237] Table 2

[0238]

[0239]

[0240] In Examples 1-24, by optimizing the composition of the polymer in the bonding 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 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 electrode and the negative electrode electrode is better, and the difference between the two is small, so that the poor fitting between the negative electrode electrode and the isolation membrane is effectively alleviated, the positive electrode electrode, the negative electrode electrode and the isolation membrane are mutually bonded and supported, the wettability of the electrode to the electrolyte is improved, the internal resistance of the battery is low, and the volume expansion of the negative electrode electrode during the lithium insertion and extraction process is effectively suppressed, and the cycle performance of the battery is effectively improved.

[0241] In Comparative Example 1, since a binder without butadiene copolymer is used in the negative electrode active material layer, the bonding force between the second polymer and the binder 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 lithium insertion and extraction cannot be effectively suppressed. The plate has poor wettability to the electrolyte and the battery has poor cycle performance.

[0242] 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 and support each other, resulting in a loose battery, a lower hardness, a significantly increased internal resistance of the battery, a worse wettability of the electrode to the electrolyte, and poor battery cycle performance.

[0243] 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.

[0244] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery, characterized in that: 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, characterized in that 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, characterized in that 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, characterized in that: 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, characterized in that 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, characterized in that: 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, characterized in that 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, characterized in that: 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, characterized in that 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that Further including: The tackifying resin has a mass of m3 in the polymer, and m1:m3 is 100:(1-15).

15. The battery according to claim 14, characterized in that 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, characterized in that: 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, characterized in that: 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 separator; 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, characterized in that 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, characterized in that The constituent monomers of the second polymer include a fourth monomer.

20. The method according to any one of claims 17 to 19, characterized in that: 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, characterized in that: 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, characterized in that The viscosity of the tackifying resin at 25° C. is 100 mPa·s-5000 mPa·s.

23. An electrical device, characterized in that: 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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