Binder for secondary battery, method for producing the same, secondary battery, and power consumption device

Abstract

This application relates to the field of secondary battery technology, and particularly to a binder for secondary batteries, a method for manufacturing the same, secondary batteries, and power consumption devices. The binder includes a core layer structure and a shell layer structure provided on the surface of the core layer structure. The shell layer structure includes an acrylate copolymer, the core layer structure includes a high-rigidity polymer, and the range value of the crystallinity of the high-rigidity polymer is 32% to 94%. The core-shell structured binder includes a core layer structure of a high-rigidity polymer. In the process of cold pressing the cell, the high-rigidity polymer stabilizes the particle structure of the binder as a support, that is, the high-rigidity polymer plays a supporting role, improves the overall rigidity of the binder, and improves the size stability of the binder during cold pressing of the cell, without being completely deformed, and improves the adhesion during cold pressing of the cell, thereby improving the hardness of the cell.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the priority of the Chinese patent application with the application number 202310447245.8 filed on April 24, 2023, and all its contents are incorporated herein by reference.

[0002] This application relates to the field of secondary battery technology, and particularly to a binder for secondary batteries and its manufacturing method, secondary batteries, and power consumption devices.

Background Art

[0003] With the rapid growth of portable electronic devices, electric vehicles, etc., the demand for power batteries is also increasing. Among them, the electrical and chemical properties of batteries are attracting more and more attention.

[0004] Currently, there is a problem of openings in battery cells, that is, gaps are easily formed between the polar sheet and the separator, thereby deteriorating the cycle characteristics of the battery.

Summary of the Invention

[0005] The main object of this application is to provide a binder that improves the adhesion between the polar sheet and the separator and enhances the performance of the battery.

[0006] To achieve the above object, this application provides a binder for secondary batteries. The binder includes a core - layer structure and a shell - layer structure provided on the surface of the core - layer structure. The shell - layer structure includes an acrylate copolymer, the core - layer structure includes a high - rigidity polymer, and the range value of the crystallinity of the high - rigidity polymer is 32% - 94%.

[0007] The acrylate copolymer has good adhesion, and by using the acrylate copolymer, the adhesion between the separator and the polar sheet after cold pressing can be further improved.

[0008] Regarding the high-rigidity polymer, the range value of the crystallinity of the high-rigidity polymer is 32% - 94%, which has high strength and has the characteristics of impact resistance, heat resistance, hardness, and deterioration resistance. In the process of cold pressing of the cell, the high-rigidity polymer is not easily deformed. As can be understood, in the process of cold pressing, no deformation or little deformation occurs in the high-rigidity polymer.

[0009] The binder with a core-shell structure includes the core layer structure of the high-rigidity polymer. In the process of cold pressing of the cell, the high-rigidity polymer acts as a support to stabilize the particle structure of the binder, that is, the high-rigidity polymer plays a supporting role, improves the overall rigidity of the binder, improves the size stability of the binder during cold pressing of the cell, does not completely deform, and improves the adhesion of the cold pressing of the cell, and improves the hardness of the cell.

[0010] As can be understood, when the high-rigidity polymer of the core layer is not used as a support, the probability of the binder being crushed increases. During the process of the binder being crushed, the voids between the binders are compressed and blocked, which is disadvantageous for the penetration of the electrolyte and the transmission of ions.

[0011] Since the high-rigidity polymer is not easily deformed, the binder can maintain a certain shape during the cold pressing process, and improves the problem that the voids between the binder particles are blocked due to the deformation of the binder during the process of the binder being crushed.

[0012] Since the binder of the present application has the support of the high-rigidity polymer, during cold pressing, complete deformation of the binder particles is not likely to occur, and the voids between the binder particles are not blocked. The unblocked voids serve as a passage for electrolyte impregnation, which is advantageous for ion transmission. At the same time, it can further improve the hardness of the cell, improve the dynamic characteristics of the secondary battery, reduce the electrical and chemical impedance, and improve the cycle characteristics of the secondary battery.

[0013] As can be understood, in the process of cold pressing the cell, the core layer structure of the binder does not deform or has little deformation, reducing the probability of the binder particles being crushed. The shell layer structure contains an acrylate copolymer, and the acrylate copolymer can provide good viscosity, improving the adhesion of the cold pressing of the cell. As can be understood, in the process of cold pressing, the acrylate copolymer in the shell layer structure deforms under the extrusion force and can be inserted into the gap between the separator and the polar sheet, improving the adhesion.

[0014] Optionally, the crystallinity range of the high-rigidity polymer is 40% - 80%.

[0015] To improve the hardness of the high-rigidity polymer, preferably, the crystallinity of the high-rigidity polymer is 40% or more. At the same time, considering that if the crystallinity is too high, the process is difficult to realize, preferably, the crystallinity of the high-rigidity polymer is 80% or less.

[0016] Optionally, the high-rigidity polymer contains at least one of polyethylene, polypropylene, polystyrene, polymethyl methacrylate, and polyamide.

[0017] The high-rigidity polymer includes general engineering plastics. Engineering plastics are industrial plastics used as industrial parts or outer case materials and have good strength, impact resistance, heat resistance, hardness, and deterioration resistance. For example, it contains at least one of polyethylene, polypropylene, polystyrene, polymethyl methacrylate, and polyamide. The high-rigidity polymer of the present application can select the above-listed high-rigidity polymers. Naturally, other high-rigidity polymers other than those listed in the present application can also be selected. The crystallinity of engineering plastics is relatively high, and the general crystallinity is 32% - 94%. Using the above high-rigidity polymer as the core layer structure is advantageous for improving the cold pressing performance of the binder.

[0018] Optionally, the shape of the binder includes a spherical shape.

[0019] The spherical shape is advantageous for uniformly dispersing the paste during the stirring process and helps for uniform coating.

[0020] Optionally, the volume-based particle size distribution Dv50 of the binder is 1 μm to 15 μm, preferably, the volume-based particle size distribution Dv50 of the binder is 1 μm to 12 μm.

[0021] To improve the lithium ion (taking a lithium ion battery as an example, but other types of secondary batteries may also be applicable) permeability on the separator and the energy density of the battery, the volume-based particle size distribution Dv50 of the binder is 1 μm to 15 μm, preferably 1 μm to 12 μm.

[0022] Optionally, the ratio of the volume-based particle size distribution Dv50 of the acrylic ester copolymer to the volume-based particle size distribution Dv50 of the high-rigidity polymer is 1:(1 to 50).

[0023] To effectively adsorb the acrylic ester copolymer on the surface of the core layer structure to form a core-shell structure, the volume-based particle size distribution Dv50 of the acrylic ester copolymer is smaller than the volume-based particle size distribution Dv50 of the high-rigidity polymer. Specifically, the ratio of the volume-based particle size distribution Dv50 of the acrylic ester copolymer to the volume-based particle size distribution Dv50 of the high-rigidity polymer is 1:(1 to 50).

[0024] Optionally, the volume-based particle size distribution Dv50 of the high-rigidity polymer is 0.1 μm to 5 μm, preferably, the volume-based particle size distribution Dv50 of the high-rigidity polymer is 0.5 μm to 2 μm. And / or, the volume-based particle size distribution Dv50 of the acrylic acid ester copolymer is 100 nm to 200 nm, preferably, the volume-based particle size distribution Dv50 of the acrylic acid ester copolymer is 130 nm to 180 nm. As can be understood, in order to obtain a core-shell structure binder and further to improve the adhesiveness of the binder, the volume-based particle size distribution Dv50 of the high-rigidity polymer is 0.1 μm to 5 μm, preferably 0.5 μm to 2 μm, and the volume-based particle size distribution Dv50 of the acrylic acid ester copolymer is 100 nm to 200 nm, preferably 130 nm to 180 nm.

[0025] As can be understood, for the binder with a core-shell structure, the shell layer structure may completely cover the core layer structure, or the shell layer structure may not completely cover the shell layer structure.

[0026] Optionally, the ratio of the mass of the shell layer structure to the mass of the core layer structure is 1:(0.1 to 10), preferably, the ratio of the mass of the shell layer structure to the mass of the core layer structure is 1:(0.1 to 5).

[0027] In order to improve the problem that the adhesion performance of the binder decreases due to too much mass of the high-rigidity polymer, and to improve the problem that the overall hardness of the binder decreases due to too little mass of the high-rigidity polymer and affects the performance of the subsequent cells, the ratio of the mass of the shell layer structure to the mass of the core layer structure is 1:(0.1 to 10), preferably, the ratio of the mass of the shell layer structure to the mass of the core layer structure is 1:(0.1 to 5).

[0028] Optionally, the constituent monomers of the acrylic acid ester copolymer include at least two of acrylic acid ester monomers, acrylonitrile monomers, and acrylamide monomers.

[0029] The acrylic acid ester copolymer has good adhesiveness. By using the acrylic acid ester copolymer, the adhesiveness between the separator and the polar sheet after cold pressing can be further improved.

[0030] As can be understood, the acrylate monomer can improve the swelling resistance of the polymer, and can adjust the glass transition temperature of the polymer as a flexible monomer segment in the molecular segment, improve the toughness during the coating of the binder, and help to exhibit good adhesion. The acrylonitrile monomer has a strongly polar cyano group and helps to improve the ionic conductivity. The acrylamide monomer plays a role in adjusting the molecular weight.

[0031] When the constituent monomer of the acrylate copolymer contains two of the acrylate monomer, the acrylonitrile monomer, and the acrylamide monomer, it has excellent adhesion performance. When it contains the above three monomers at the same time, the performance is even more excellent.

[0032] Optionally, the acrylate monomer contains at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and / or the acrylonitrile monomer contains at least one of acrylonitrile or methacrylonitrile, and / or the acrylamide monomer contains at least one of acrylamide, N-methylolacrylamide, and N-butoxymethylacrylamide.

[0033] By using any one or more of the above acrylic ester monomers, the glass transition temperature of the polymer can be adjusted, and the swelling resistance of the polymer can be improved. The above is an enumeration of acrylic ester monomers. The acrylic ester monomer used in the present application may be the substances enumerated above, or may be other acrylic ester monomers other than the present application.

[0034] By using any one or more of the above acrylonitrile monomers, the ionic conductivity of the binder can be improved. The above is an enumeration of acrylonitrile monomers. The acrylonitrile monomer used in the present application may be the substances enumerated above, or may be other acrylonitrile monomers other than the present application.

[0035] By using any one or more of the above acrylamide monomers, it can play a role in adjusting the molecular weight, is used to adjust the molecular weight of the polymer, and helps to improve the adhesiveness when the molecular weight of the binder is within a certain range. The above is an enumeration of acrylamide monomers. The acrylamide monomer used in the present application may be the substances enumerated above, or may be other acrylamide monomers other than the present application.

[0036] Optionally, the constituent monomers of the acrylic ester copolymer include acrylic ester monomers, acrylonitrile monomers, and acrylamide monomers, and the mass ratio of the acrylic ester monomer, the acrylonitrile monomer, and the acrylamide monomer is 1:(0.01~0.8):(0.01~0.15), preferably, the mass ratio of the acrylic ester monomer, the acrylonitrile monomer, and the acrylamide monomer is 1:(0.1~0.6):(0.06~0.12).

[0037] By controlling the mass ratio of the above three monomers within the above range, the molecular weight and glass transition temperature of the polymer can be controlled, and the adhesion performance of the binder can be improved.

[0038] This application further provides a step of manufacturing an acrylic ester copolymer emulsion, a step of mixing the acrylic ester copolymer emulsion with a high-rigidity polymer and performing spray drying to obtain a binder having a core-shell structure, and provides a method for manufacturing a binder for a secondary battery.

[0039] By manufacturing an acrylic ester copolymer emulsion by an emulsion polymerization method, the acrylic ester copolymer emulsion is mixed with a high-rigidity polymer, and spray drying is performed to obtain a binder having a core-shell structure.

[0040] During spray drying, since the acrylic ester copolymer has a small particle size and viscosity, it is adsorbed and coated on the surface of high-rigidity particles having no viscosity on the surface to form a core-shell structure.

[0041] In the step of forming a binder having a core-shell structure, compared with the emulsion polymerization method, spray drying has an excellent effect of coating the acrylic ester copolymer on high-rigidity particles. At the same time, in the process of emulsion polymerization, it is difficult to control the polymerization step. By using the spray drying process to manufacture a binder having a core-shell structure, the adhesiveness of the obtained binder is better.

[0042] In the process of spray drying, the shell layer structure is formed by spherical particles depositing on the surface of the core layer structure. The spherical particles are in point contact with each other, forming passages and voids in the shell layer, which is useful for the impregnation of the electrolyte. With the support of the core layer structure, in the process of cold pressing, the probability of the binder particles being crushed is reduced, that is, the possibility of the passages and voids in the shell layer being crushed is reduced, improving the porosity of the adhesive layer, and the electrolyte can pass through the voids between the acrylic ester copolymer particles and penetrate into the binder.

[0043] At the same time, the surface of some high-rigidity polymer materials has abundant functional groups, which can improve the impregnation property of the electrolyte, accelerate the ion transmission rate, and improve the electrical and chemical properties of the battery. For example, a high-rigidity polymer composed of polymethyl methacrylate has an ester group, which can improve the impregnation of the solvent in the electrolyte. For example, the solvent in the electrolyte includes ethylene carbonate, propylene carbonate, methyl ethyl carbonate, etc.

[0044] Optionally, the step of manufacturing an acrylate copolymer emulsion comprises stirring and emulsifying water, an emulsifier, and a constituent monomer of the acrylate copolymer to obtain a preliminary emulsion of the monomer; stirring and emulsifying the emulsifier and water, adding the preliminary emulsion and an initiator under heating conditions, raising the temperature, and obtaining an acrylate copolymer emulsion.

[0045] In the step of manufacturing an acrylate copolymer emulsion, first, pre-emulsification is carried out, and then the polymerization reaction step is used to mix the monomers more uniformly. The obtained acrylate copolymer has more uniform particles and more stable performance.

[0046] The present application further provides a separator including a base film and an adhesive layer provided on at least one side of the base film, wherein the adhesive layer includes the binder for the secondary battery, or the adhesive layer includes a binder manufactured by the manufacturing method of the binder for the secondary battery.

[0047] The present application further provides a secondary battery including the separator.

[0048] The present application further provides a power consumption device including the secondary battery.

Brief Description of the Drawings

[0049] To more clearly explain the technical solutions in the embodiments of the present application or the prior art, the drawings necessary for the description of the embodiments or the prior art are briefly described below. The drawings shown below are only some embodiments of the present application. It is obvious that those skilled in the art can obtain other drawings based on the structures shown in these drawings without creative effort.

[0050]

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Figure 8

Description of Reference Numerals

[0051] 1 Battery pack 2 Upper housing 3 Lower housing 4 Battery module 5 Secondary battery 51 Housing 52 Electrode assembly 53 Top cover assembly

[0052] The realization of the object of the present application, the functional features and advantages will be further described with reference to the drawings by combining the embodiments.

Modes for Carrying Out the Invention

[0053] With reference to the drawings in the embodiments of the present application below, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only some of the embodiments of the present application, not all of them. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present application.

[0054] Hereinafter, embodiments of the binder of the present application, its manufacturing method, and a separator, an electrode assembly, a battery cell, a battery, and a power consumption device including the binder will be described in detail with reference to the drawings as appropriate. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and overlapping descriptions of substantially the same structures may be omitted. This is to prevent the following description from becoming unnecessarily redundant and to facilitate the understanding of those skilled in the art. Also, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0055] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of a specific range. A range defined in such a way may or may not include the values at both ends, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, it is understood that ranges of 60 - 110 and 80 - 120 are also contemplated. Also, if the minimum range values 1 and 2 are listed, and the maximum range values 3, 4, and 5 are listed, ranges of 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5 are all contemplated. In this application, unless otherwise explained, the numerical range "a - b" means an abbreviated representation of any combination of real numbers between a and b, and both a and b are real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are all listed in this specification, and "0 - 5" is only an abbreviated representation of combinations of these numerical values. Also, when a certain parameter is expressed as an integer ≧2, it corresponds to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0056] All embodiments and selectable embodiments of this application can, unless otherwise specified, be combined with each other to form new technical solutions.

[0057] All technical features and selectable technical features of this application can, unless otherwise explained, be combined with each other to form new technical solutions.

[0058] All steps of the present application can be carried out in sequence or randomly, preferably in sequence, unless otherwise specified. For example, when the method includes steps (a) and (b), the method may include steps (a) and (b) carried out in sequence, or steps (b) and (a) carried out in sequence. For example, when it is said that the method may further include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0059] There is a problem with the opening in the battery cell, that is, a gap is easily formed between the polar sheet and the separator, thereby deteriorating the cycle characteristics of the battery.

[0060] For example, polyvinylidene fluoride is widely used as the most common binder for separators, but at present, polyvinylidene fluoride is costly. Coating the surface of the separator of a secondary battery with a polyvinylidene fluoride polymer can partially solve the problem of the high-temperature shrinkage of the separator. Cold pressing is performed on the wound cell. However, ordinary polyvinylidene fluoride is a homopolymer with a crystallinity of about 50%, and the adhesive force with the positive and negative electrode sheets is insufficient, and the problem of the opening of the cell always occurs, and the requirements for the coating performance of the separator in a power secondary battery cannot be met.

[0061] That is, coating the surface of the separator of the battery with a polyvinylidene fluoride polymer can partially solve the problem of the high-temperature shrinkage of the separator. Cold pressing is performed on the wound cell. However, ordinary polyvinylidene fluoride is a homopolymer with a crystallinity of about 50%, and the adhesive force with the positive and negative electrode sheets is insufficient, and the problem of the opening of the cell always occurs. When an opening occurs in the cell, a gap is formed between the polar sheet and the separator, the structure of the whole cell becomes loose, the hardness of the cell decreases, and the cycle characteristics of the cell are affected.

[0062] The cell is formed by adhering a positive electrode sheet, a negative electrode sheet, and a separator. The cell has a certain hardness. That is, the integrally adhered positive electrode sheet, negative electrode sheet, and separator are bonded to each other and supported by each other, thus forming a structure with a certain thickness. The structure with a certain thickness has a certain hardness. However, during the charge and discharge process, the negative electrode expands. If the adhesive force is weak, a gap is formed between the positive electrode sheet or the negative electrode sheet and the separator. The positive and negative electrode sheets and the separator cannot be bonded to each other and supported by each other, resulting in looseness in the cell, a decrease in hardness. At this time, the power characteristics of the cell deteriorate. For example, the rate performance deteriorates, and at the same time, the cycle performance deteriorates. For example, in an electric vehicle, when the battery cell becomes loose, the charging speed of the battery slows down, and at the same time, the cycle performance of the battery deteriorates, directly leading to a shortening of the battery life. In an electric vehicle, it is necessary to frequently replace the battery, increasing the cost for consumers in the electric vehicle.

[0063] Based on this, the present application provides a binder for a secondary battery. The binder includes a core layer structure and a shell layer structure provided on the surface of the core layer structure. The shell layer structure includes an acrylate copolymer, and the core layer structure includes a high-rigidity polymer. The range value of the crystallinity of the high-rigidity polymer is 32% - 94%.

[0064] A binder is a material having adhesive performance and is used to adhere different substances.

[0065] The core-shell structure refers to a structure composed of a central core and a shell covering the outer layer.

[0066] The core layer structure is the structure located inside and covered by the outer shell in the core-shell structure.

[0067] The shell layer structure is the structure located outside and covering the surface of the core layer structure in the core-shell structure.

[0068] The core-shell structure can be observed by a transmission electron microscope. Specifically, since the materials of the core-shell structure are different, a contrast difference (weight thickness contrast) occurs between the core layer structure part and the shell layer structure part in the transmission electron microscope image. The weight thickness contrast results from the difference in the thickness and mass of different regions on the sample surface, leading to a contrast difference. The scattering ability of electrons for each part of the sample is different, and the number of transmitted electrons passing through the objective lens is also different. Therefore, there is a difference in the intensity of the electron beam. The region with strong scattering and few transmitted electrons has a dark image, and vice versa, the image is bright.

[0069] Regarding the acrylic ester copolymer, the acrylic ester copolymer is a general term for polymers produced by copolymerizing an acrylic ester monomer and other comonomers.

[0070] The structure of the acrylic ester monomer has an acrylic ester group, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate.

[0071] The acrylic ester copolymer has good adhesiveness. By using the acrylic ester copolymer, the adhesiveness between the separator and the polar sheet after cold pressing can be further improved.

[0072] Regarding crystallinity, crystallinity is used to represent the proportion of the crystalline region in the polymer. A crystal is a regular arrangement of molecular chains.

[0073] The crystallinity can be measured using the DSC (Differential Scanning Calorimetry) method. For example, the method for measuring the crystallinity of polypropylene is as follows. The crystallinity is determined using the DSC method, and a unified numerical value is used for the heat of fusion ΔH0 of a completely crystalline polymer to reduce the influence on the measurement results of the sample. The specific operation is as follows. Under the protection of nitrogen gas with a flow rate of 20 mL / min, 5 mg of the sample is taken and placed in a DSC (Differential Scanning Calorimetry (DSC) apparatus: SDT2960 type, TA Instruments, USA). The temperature is raised from room temperature to 210 °C at a rate of 15 °C / min, and the thermal history is removed by holding at a constant temperature for 5 min. Then, cooling is started at a constant rate to room temperature at a cooling rate of 5 °C / min. The process is recorded and the crystallinity is calculated.

[0074] For high-rigidity polymers, the range of the crystallinity of high-rigidity polymers is 32% - 94%. They have high strength and properties such as impact resistance, heat resistance, hardness, and resistance to deterioration. For example, they include polyethylene, polypropylene, etc. High-rigidity polymers are lighter in specific gravity than inorganic particles and can improve the battery energy density.

[0075] During the cold pressing process of the cell, the high-rigidity polymer is not easily deformed. As can be understood, no deformation or only minor deformation occurs in the high-rigidity polymer during the cold pressing process. As can be understood, the range of the cold pressing force during the cold pressing process is 1 MPa - 10 Mpa. Within this range, no deformation or only minor deformation occurs in the high-rigidity polymer.

[0076] The core-shell structure binder includes the core layer structure of the high-rigidity polymer. During the cold pressing process of the cell, the high-rigidity polymer acts as a support to stabilize the particle structure of the binder. That is, the high-rigidity polymer plays a supporting role, improves the overall rigidity of the binder, improves the size stability of the binder during the cold pressing of the cell, prevents it from being completely deformed, and improves the adhesion force during the cold pressing of the cell, thereby improving the hardness of the cell.

[0077] As can be understood, when the high-rigidity polymer of the core layer is not used as a support, the probability of the binder being crushed increases. During the process of the binder being crushed, the voids between the binders are compressed and blocked, which is disadvantageous for the penetration of the electrolyte and the transmission of ions.

[0078] Since the high-rigidity polymer is difficult to deform, the binder can maintain a certain shape during the cold pressing process, improving the problem that the voids between the binder particles are blocked due to the deformation of the binder during the process of the binder being crushed.

[0079] Since the binder of the present application has the support of the high-rigidity polymer, during cold pressing, complete deformation of the binder particles is less likely to occur, and the voids between the binder particles will not be blocked. The unblocked voids serve as passages for electrolyte impregnation, which is advantageous for ion transmission. At the same time, it can further improve the hardness of the cell, improve the dynamic characteristics of the secondary battery, reduce the electrical and chemical impedance, and improve the cycle characteristics of the secondary battery.

[0080] As can be understood, during the cold pressing process of the cell, the core layer structure of the binder does not deform or has little deformation, reducing the probability of the binder particles being crushed. The shell layer structure contains an acrylate copolymer, and the acrylate copolymer can provide good viscosity, improving the adhesion during the cold pressing of the cell.

[0081] In the above 32% - 94%, the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As specific examples, the endpoint values in the examples and 32%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 94%, etc., and the range values between any two of the above endpoint values are included, but not limited thereto.

[0082] In one embodiment, the range value of the crystallinity of the high-rigidity polymer includes 40% - 80%.

[0083] To improve the hardness of the high-rigidity polymer, preferably, the crystallinity of the high-rigidity polymer is 40% or more. At the same time, considering that if the crystallinity is too high, the process is difficult to realize, preferably, the crystallinity of the high-rigidity polymer is 80% or less.

[0084] In the above 40% - 80%, the value includes the minimum value and the maximum value of this range, and each value between this minimum value and the maximum value. As specific examples, the endpoint values in the examples and 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc., and the range values between any two of the above endpoint values are included, but not limited thereto.

[0085] In one embodiment, the high-rigidity polymer includes at least one of polyethylene, polypropylene, polystyrene, polymethyl methacrylate, and polyamide.

[0086] The high-rigidity polymer includes general engineering plastics. Engineering plastics are industrial plastics used as industrial parts or outer case materials, and have good strength, impact resistance, heat resistance, hardness, and deterioration resistance. For example, it includes at least one of polyethylene, polypropylene, polystyrene, polymethyl methacrylate, and polyamide. The high-rigidity polymer of the present application can select the above-listed high-rigidity polymers. Naturally, other high-rigidity polymers other than those listed in the present application can also be selected. The crystallinity of engineering plastics is relatively high, and the general crystallinity is 32% - 94%. Using the above high-rigidity polymer as the core layer structure is advantageous for improving the cold pressing performance of the binder.

[0087] In one embodiment, the shape of the binder includes a spherical shape.

[0088] The spherical shape is advantageous for uniformly dispersing in the process of stirring the paste and helps for uniform coating.

[0089] In one embodiment, the volume-based particle size distribution Dv50 of the binder is 1 μm to 15 μm, preferably, the volume-based particle size distribution Dv50 of the binder is 1 μm to 12 μm.

[0090] Regarding Dv50, in the sample particles, the particle size of 50% of the total volume of particles is larger than this value, and the particle size of the other 50% of the total volume of particles is smaller than this value. Dv50 represents the particle size value in the sample.

[0091] The volume-based particle size distribution Dv50 of the binder can be measured using methods known in the art. As an example, referring to GB / T 19077-2016, a characteristic evaluation test can be performed using a Malvern laser particle size analyzer, for example, measurement can be performed using an apparatus such as Malvern's Mastersizer-3000.

[0092] In order to improve the lithium ion (taking a lithium ion battery as an example, but it may also be other types of secondary batteries) permeability on the separator and the energy density of the battery, the volume-based particle size distribution Dv50 of the binder is 1 μm to 15 μm, preferably 1 μm to 12 μm.

[0093] In the above 1 μm to 15 μm, the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As specific examples, the endpoint values in the examples and 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc., and the range values between any two of the above endpoint values are included, but not limited thereto.

[0094] In the above 1 μm to 15 μm, the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As specific examples, the endpoint values in the examples and 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc., and the range values between any two of the above endpoint values are included, but not limited thereto.

[0095] Theoretically, the volume-based particle size distribution Dv50 of the acrylate copolymer in the binder and the volume-based particle size distribution Dv50 of the high-rigidity polymer can be obtained after measurement with a transmission electron microscope and a scanning electron microscope.

[0096] The size of the core layer structure can be measured from the binder image obtained with a transmission electron microscope, and the size of the shell layer particles can be measured from the image obtained with a scanning electron microscope.

[0097] In one embodiment, the ratio of the volume-based particle size distribution Dv50 of the acrylate copolymer to the volume-based particle size distribution Dv50 of the high-rigidity polymer is 1:(1 to 50).

[0098] In order to effectively adsorb the acrylate copolymer on the surface of the core layer structure to form a core-shell structure, the volume-based particle size distribution Dv50 of the acrylate copolymer is smaller than the volume-based particle size distribution Dv50 of the high-rigidity polymer. Specifically, the ratio of the volume-based particle size distribution Dv50 of the acrylate copolymer to the volume-based particle size distribution Dv50 of the high-rigidity polymer is 1:(1 to 50).

[0099] In the above 1:(1 to 50), the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As specific examples, the end point values in the examples and 1:1, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, etc., and the range values between any two of the above end point values are included, but not limited thereto.

[0100] In one embodiment, the volume-based particle size distribution Dv50 of the high-rigidity polymer is 0.1 μm to 5 μm, preferably, the volume-based particle size distribution Dv50 of the high-rigidity polymer is 0.5 μm to 2 μm, and / or the volume-based particle size distribution Dv50 of the acrylate copolymer is 100 nm to 200 nm, preferably, the volume-based particle size distribution Dv50 of the acrylate copolymer is 130 nm to 180 nm.

[0101] As can be understood, in order to obtain a binder having a core-shell structure and further to improve the adhesiveness of the binder, the volume-based particle size distribution Dv50 of the high-rigidity polymer is 0.1 μm to 5 μm, preferably 0.5 μm to 2 μm, and the volume-based particle size distribution Dv50 of the acrylate copolymer is 100 nm to 200 nm, preferably 130 nm to 180 nm.

[0102] In the above 0.1 μm to 5 μm, the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As specific examples, the endpoint values in the examples and 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc., and the range values between any two of the above endpoint values are included, but not limited thereto.

[0103] In the above 0.5 μm to 2 μm, the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As specific examples, the endpoint values in the examples and 0.5 μm, 0.7 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.7 μm, 1.9 μm, 2 μm, etc., and the range values between any two of the above endpoint values are included, but not limited thereto.

[0104] In the above 100 nm to 200 nm, the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As specific examples, the endpoint values in the examples and 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 18 nm, 190 nm, 200 nm, etc., and the range values between any two of the above endpoint values are included, but not limited thereto.

[0105] In the above 130 nm to 180 nm, the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As specific examples, the endpoint values in the examples and 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 18 nm, etc., and the range values between any two of the above endpoint values are included, but not limited thereto.

[0106] As can be understood, the binder with a core-shell structure may have the shell layer structure completely covering the core layer structure, or the shell layer structure may not completely cover the shell layer structure, and it is not specifically limited.

[0107] In one embodiment, the ratio of the mass of the shell layer structure to the mass of the core layer structure is 1:(0.1 to 10), and preferably, the ratio of the mass of the shell layer structure to the mass of the core layer structure is 1:(0.1 to 5).

[0108] Regarding the measurement method of the mass ratio, in the manufacturing process of the binder, when recording the mass of the highly rigid polymer for manufacturing the core layer structure input in the manufacturing process as m and the mass of the acrylate copolymer for manufacturing the shell layer structure as n, the mass ratio of the core layer structure to the shell layer structure is m:n.

[0109] In order to improve the problem that the adhesion performance of the binder decreases due to too much mass of the highly rigid polymer, and to improve the problem that the overall hardness of the binder decreases due to too little mass of the highly rigid polymer and affects the performance of subsequent cells, the ratio of the mass of the shell layer structure to the mass of the core layer structure is 1:(0.1 to 10), and preferably, it is 1:(0.1 to 5).

[0110] In the above 1:(0.1 to 10), the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value, and specific examples include the endpoint values in the examples and 1:0.1, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc., and the range values between any two of the above endpoint values, but are not limited thereto. In the above 1:(0.1 to 5), the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value, and specific examples include the endpoint values in the examples and 1:0.1, 1:1, 1:2, 1:3, 1:4, 1:5, etc., and the range values between any two of the above endpoint values, but are not limited thereto.

[0111] In one embodiment, the constituent monomers of the acrylic acid ester copolymer include at least two of acrylic acid ester monomers, acrylonitrile monomers, and acrylamide monomers.

[0112] The acrylic acid ester monomer contains an acrylic acid ester group in the structure of the acrylic acid ester monomer. For example, its structural formula is JPEG2025517838000002.jpg20170, where R1 contains a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and R2 contains an alkyl group having 1 to 12 carbon atoms. In one embodiment, the acrylic acid ester monomer includes methyl acrylate, ethyl acrylate, n-butyl acrylate, etc.

[0113] The acrylonitrile monomer contains an unsaturated cyano group in the structure of the acrylonitrile monomer. For example, its structural formula is JPEG2025517838000003.jpg17170, and here, R3 contains a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. In one embodiment, the acrylonitrile monomer includes acrylonitrile, methacrylonitrile, etc.

[0114] The acrylamide monomer contains an unsaturated amide group in the structure of the acrylamide monomer. For example, its structural formula is JPEG2025517838000004.jpg22170, where R4 contains a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R5 contains a hydrogen atom, an alkyl group having 1 to 6 carbon atoms substituted with a hydroxyl group, or an alkoxy group having 1 to 6 carbon atoms. In one embodiment, the acrylamide monomer includes acrylamide, N-methylol acrylamide, N-butoxymethyl acrylamide, etc.

[0115] As can be understood, the acrylic acid ester monomer can improve the swelling resistance of the polymer, and can adjust the glass transition temperature of the polymer as a flexible monomer segment in the molecular segment, improve the toughness during the coating of the binder, and help to exhibit a good adhesion effect.

[0116] Acrylonitrile-based monomers have a highly polar cyano group and are useful for improving ionic conductivity.

[0117] Acrylamide-based monomers play a role in regulating the molecular weight.

[0118] When the constituent monomers of the acrylate copolymer include two of acrylate monomers, acrylonitrile-based monomers, and acrylamide-based monomers, for example, when including acrylate monomers and acrylonitrile-based monomers, and acrylate monomers and acrylamide-based monomers, the adhesion performance is excellent. When including the above three monomers simultaneously, the performance is even more excellent.

[0119] In one embodiment, the acrylate monomer includes at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate, and / or the acrylonitrile-based monomer includes at least one of acrylonitrile or methacrylonitrile, and / or the acrylamide-based monomer includes at least one of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide.

[0120] By using any one or more of the above acrylic acid ester monomers, the glass transition temperature of the polymer can be adjusted, and the swelling resistance of the polymer can be improved. The above is an enumeration of acrylic acid ester monomers. The acrylic acid ester monomers used in this application may be the substances enumerated above, or may be other acrylic acid ester monomers other than this application.

[0121] By using any one or more of the above acrylonitrile monomers, the ionic conductivity of the binder can be improved. The above is an enumeration of acrylonitrile monomers. The acrylonitrile monomers used in this application may be the substances enumerated above, or may be other acrylonitrile monomers other than this application.

[0122] By using any one or more of the above acrylamide monomers, it can play a role in adjusting the molecular weight, is used to adjust the molecular weight of the polymer, and helps to improve the adhesiveness when the molecular weight of the binder is within a certain range. The above is an enumeration of acrylamide monomers. The acrylamide monomers used in this application may be the substances enumerated above, or may be other acrylamide monomers other than this application.

[0123] In one embodiment, the constituent monomers of the acrylic acid ester copolymer include acrylic acid ester monomers, acrylonitrile monomers, and acrylamide monomers, and the mass ratio of the acrylic acid ester monomers, acrylonitrile monomers, and acrylamide monomers is 1:(0.01~0.8):(0.01~0.15), preferably, the mass ratio of the acrylic acid ester monomers, acrylonitrile monomers, and acrylamide monomers is 1:(0.1~0.6):(0.06~0.12).

[0124] By controlling the mass ratio of the above three monomers within the above range, the molecular weight and glass transition temperature of the polymer can be controlled, and the adhesion performance of the binder can be improved.

[0125] In the case of the above 1:(0.01 to 0.8):(0.01 to 0.15), the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. Specific examples include the endpoint values in the examples and 1:0.01:0.01, 1:0.1:0.01, 1:0.4:0.01, 1:0.8:0.01, 1:0.01:0.05, 1:0.01:0.1, 1:0.01:0.15, 1:0.1:0.01, 1:0.1:0.05, 1:0.1:0.15, 1:0.4:0.01, 1:0.4:0.05, 1:0.4:0.15, 1:0.8:0.01, 1:0.8:0.05, 1:0.8:0.15, etc., and the range values between any two of the above endpoint values, but are not limited thereto.

[0126] In the case of the above 1:(0.1 to 0.6):(0.06 to 0.12), the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. Specific examples include the endpoint values in the examples and 1:0.1:0.06, 1:0.4:0.06, 1:0.6:0.06, 1:0.1:0.1, 1:0.1:0.12, etc., and the range values between any two of the above endpoint values, but are not limited thereto.

[0127] In one embodiment, the present application provides a method for manufacturing a binder for a secondary battery, further including the steps of manufacturing an acrylate copolymer emulsion, mixing the acrylate copolymer emulsion and a high-rigidity polymer, and performing spray drying to obtain a core-shell structured binder.

[0128] In spray drying, due to mechanical action, the material to be dried (a mixture of an acrylate copolymer emulsion and a high-rigidity polymer) is dispersed into very fine mist-like fine particles, brought into contact with hot air (which increases the evaporation area of moisture and accelerates the drying process), and most of the moisture is instantaneously removed, drying the solid substances in the material into powder.

[0129] A core-shell structured binder is obtained by the process of spray drying.

[0130] During spray drying, since the acrylic ester copolymer has a small particle size and viscosity, it adsorbs onto the surface of high-rigidity particles without viscosity and is coated to form a core-shell structure.

[0131] In the step of forming a binder with a core-shell structure, compared with the emulsion polymerization method, spray drying has an excellent effect of coating the acrylic ester copolymer on high-rigidity particles. At the same time, in the process of emulsion polymerization, it is difficult to control the polymerization step. Using the spray drying process to manufacture a binder with a core-shell structure, the adhesiveness of the obtained binder is even better.

[0132] In the process of spray drying, the shell layer structure is formed by spherical particles depositing on the surface of the core layer structure. The spherical particles are in point contact with each other, forming passages and voids in the shell layer, which is helpful for the impregnation of the electrolyte. With the support of the core layer structure, in the process of cold pressing, the probability of the binder particles being crushed is reduced, that is, the possibility of the passages and voids in the shell layer being crushed is reduced, improving the porosity of the adhesive layer, and the electrolyte can pass through the voids between the acrylic ester copolymer particles and penetrate into the binder.

[0133] As is understood, many of the conventional separators for secondary batteries are polyolefin separators. The multilayer separator has the function of closing pores at high temperatures to block ion transmission, ensuring the safety of the battery. The PP (polypropylene) layer on the surface of the separator further improves the antioxidant ability of the separator. Such a multilayer polyolefin composite separator improves the cycle characteristics and safety of the battery to a certain extent compared with the conventional single-layer separator. However, the polyolefin separator still has the characteristics of poor impregnation of the electrolyte and low thermal decomposition temperature, and it is gradually becoming difficult for the performance of the multilayer polyolefin separator to meet the growing social needs.

[0134] The high-rigidity polymer of the present application has a low density, excellent thermal stability and chemical stability. At the same time, the surfaces of some high-rigidity polymer materials have abundant functional groups, which can improve the impregnation property of the electrolyte, accelerate the ion transmission rate and improve the electrical and chemical properties of the battery. For example, the high-rigidity polymer composed of polymethyl methacrylate has an ester group and can improve the impregnation of the solvent in the electrolyte. For example, the solvents in the electrolyte include ethylene carbonate, propylene carbonate, methyl ethyl carbonate, etc.

[0135] In one embodiment, the steps of manufacturing an acrylate copolymer emulsion include: stirring and emulsifying water, an emulsifier, and the constituent monomers of the acrylate copolymer to obtain a preliminary emulsion of the monomers; stirring and emulsifying the emulsifier and water, adding the preliminary emulsion and an initiator under heating conditions, raising the temperature, and obtaining an acrylate copolymer emulsion.

[0136] The preliminary emulsion is a solution obtained by preliminarily emulsifying the monomers. Emulsification is the action of uniformly dispersing a liquid into another liquid in which the liquid is in the form of very tiny droplets that do not dissolve in each other. Mixing and stirring water, an emulsifier, and the constituent monomers of the acrylate copolymer disperses the constituent monomers of the acrylate copolymer in water under the action of the emulsifier.

[0137] Regarding emulsion polymerization, emulsion polymerization is the process of dispersing monomers in water by an emulsifier and mechanical stirring to form an emulsion, and then adding an initiator to initiate the polymerization of the monomers.

[0138] Regarding the emulsifier, the emulsifier is a substance that converts oil and water that do not dissolve in each other into an emulsion that is difficult to separate. The emulsifier is generally a surfactant that has both the properties of a hydrophilic polar group and a hydrophobic (lipophilic) non-polar group.

[0139] Regarding the initiator, an initiator is a substance that can initiate a polymerization reaction in a monomer. For example, a radical initiator refers to a compound that can be easily decomposed by heat to form radicals (i.e., primary radicals), and can be used to initiate radical polymerization and copolymerization reactions of olefin-based and diene-based monomers.

[0140] In the step of manufacturing an acrylate copolymer emulsion, first perform preliminary emulsification, and then use the step of polymerization reaction to mix the monomers more uniformly. The obtained acrylate copolymer has more uniform particles and more stable performance. In the process of spray drying, it helps the acrylate copolymer particles to be effectively arranged on the core layer structure.

[0141] As can be understood, in the specific operation process, test operations can be carried out using two containers. Add water, an emulsifier, and the constituent monomers of the acrylate copolymer to the first container, stir and emulsify to obtain a preliminary emulsion of the monomers. Add more emulsifier and water to the second container, stir and emulsify, and add the above-mentioned preliminary emulsion and initiator solution under heating conditions, raise the temperature to obtain an acrylate copolymer emulsion.

[0142] For example, in one embodiment, the volume-based particle size distribution Dv50 of the acrylate copolymer obtained by emulsion polymerization is between 0.1 μm and 0.11 μm, the particle size is relatively uniform, and the volume-based particle size distribution Dv50 of the high-rigidity polymer is in the range of about 1 μm ± 0.2 μm. Through the spray drying process, the acrylate copolymer can be effectively adhered to the surface of the high-rigidity polymer.

[0143] The embodiments of the present application further provide a separator including a base film and an adhesive layer provided on at least one side of the base film, the adhesive layer includes the binder for the secondary battery, or the adhesive layer includes a binder manufactured by the manufacturing method of the binder for the secondary battery.

[0144] The embodiments of the present application further provide a secondary battery including the separator.

[0145] The secondary battery includes forms such as a battery module, a battery cell, and a battery pack. When the secondary battery is a battery cell, the battery cell includes the above-mentioned separator. When the secondary battery is a battery module, the battery module includes the above-mentioned separator. When the secondary battery is a battery pack, the battery pack includes the above-mentioned separator.

[0146] An embodiment of the present application further provides a power consumption device including the secondary battery.

[0147] Also, the electrode assembly, battery cell, battery, and power consumption device of the present application will be described below with reference to the drawings as appropriate.

[0148] In one embodiment of the present application, an electrode assembly is provided.

[0149] Generally, the electrode assembly includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. In the charge and discharge process of the battery, active ions reciprocate between the positive electrode sheet and the negative electrode sheet for insertion and desorption. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is installed between the positive electrode sheet and the negative electrode sheet, mainly playing a role in preventing short circuit between the positive and negative electrodes, and at the same time allowing ions to pass through. The separator is the above-mentioned improved separator of the present application.

[0150] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector.

[0151] As an example, the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is provided on one or both of the two opposite surfaces of the positive electrode current collector.

[0152] In some embodiments, a metal foil or a composite current collector can be used for the positive electrode current collector. As the metal foil, for example, an aluminum foil can be used. The composite current collector can include a polymer base material layer and a metal layer formed on at least one surface of the polymer base material layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material base (such as a base of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0153] In some embodiments, when the electrode assembly is a lithium-ion battery, a known positive electrode active material for a battery can be used as the positive electrode active material. As an example, the positive electrode active material may include at least one of a lithium-containing phosphate having an olivine structure, a lithium transition metal oxide, and a modified compound of each of them. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of the lithium transition metal oxide are lithium cobalt oxide (e.g., LiCoO 2 ), lithium nickel oxide (e.g., LiNiO 2 ), lithium manganese oxide (e.g., LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (abbreviation NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (abbreviation NCM 523 ), LiNi 0.5 Co 0.25 Mn0.25 O 2 (Abbreviation: NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (Abbreviation: NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Abbreviation: NCM 811 ))、lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and at least one of its modified compounds etc. may be included, but not limited thereto. As the lithium-containing phosphate with olivine structure, for example, lithium iron(II) phosphate (e.g., LiFePO 4 (Abbreviation: LFP)), a composite material of lithium iron(II) phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon may be included, but not limited thereto.

[0154] In some embodiments, the positive electrode film layer can optionally further include a binder. As an example, the binder can 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.

[0155] In some embodiments, the positive electrode film layer can optionally further include a conductive agent. As an example, the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0156] In some embodiments, the positive electrode sheet can be manufactured by the following method. Components for manufacturing the positive electrode sheet, such as a positive electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode paste. The positive electrode paste is applied to a positive electrode current collector, and through steps such as drying and cold pressing, a positive electrode sheet can be obtained.

[0157] The negative electrode sheet includes a negative electrode active material and a negative electrode film layer provided on at least one surface of the negative electrode current collector and the negative electrode current collector.

[0158] As an example, the negative electrode current collector has two surfaces facing each other in its own thickness direction, and the negative electrode film layer is provided on either one or both of the two opposing surfaces of the negative electrode current collector.

[0159] In some embodiments, a metal foil or a composite current collector can be used as the negative electrode current collector. As the metal foil, for example, a copper foil can be used. The composite current collector can include a polymer base material layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base (such as a base of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0160] In some embodiments, known anode active materials for batteries can be used as the anode active material. As an example, the anode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as the anode active material of the battery may be used. These anode active materials may be used alone or in combination of two or more.

[0161] In some embodiments, the anode film layer can optionally further include a binder. The binder can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0162] In some embodiments, the anode film layer can optionally further include a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0163] In some embodiments, the anode film layer further includes other auxiliaries such as a thickener (for example, sodium carboxymethyl cellulose (CMC-Na)) optionally.

[0164] In some embodiments, the negative electrode sheet can be manufactured in the following manner. Components for manufacturing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode paste. The negative electrode paste is applied to a negative electrode current collector, and through steps such as drying and cold pressing, a negative electrode sheet can be obtained.

[0165] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The present application does not particularly limit the type of electrolyte, and it can be selected as needed.

[0166] In some embodiments, an electrolytic solution is used as the electrolyte. The electrolytic solution contains an electrolyte salt and a solvent.

[0167] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(oxalate)borate, lithium difluorooxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0168] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl 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, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0169] In some embodiments, the electrolytic solution further selectively contains additives. For example, the additives may include a negative electrode film-forming additive and a positive electrode film-forming additive, and further may include additives that can improve specific characteristics of the battery, such as additives that improve the overcharge characteristics of the battery, additives that improve the high-temperature or low-temperature characteristics of the battery, and the like.

[0170] In some embodiments, the electrode assembly further includes a separator. The present application does not particularly limit the type of the separator, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0171] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, and are not particularly limited.

[0172] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be manufactured into an electrode assembly through a winding process or a lamination process.

[0173] In some embodiments, the electrode assembly can include an exterior material. The exterior material is used to enclose the above electrode assembly and electrolyte.

[0174] In some embodiments, the exterior material of the electrode assembly may be a rigid case such as a rigid plastic case, an aluminum case, or a steel case. The exterior material of the electrode assembly may also be a soft pack such as a pouch-type soft pack. The material of the soft pack may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0175] This application does not particularly limit the shape of the electrode assembly, and it may be cylindrical, rectangular, or any other arbitrary shape. For example, FIG. 3 shows a secondary battery 5 with a rectangular structure as an example.

[0176] In some embodiments, referring to FIG. 4, the exterior material can include a housing 51 and a cover plate 53. The housing 51 includes a bottom plate and side plates connected to the bottom plate, and a receiving cavity surrounded by the bottom plate and the side plates is formed. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can cover the opening to seal the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form a secondary battery 52 through a winding process or a lamination process. The secondary battery 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the secondary battery 52. The number of secondary batteries 52 included in the secondary battery 5 may be one or more, and those skilled in the art can select according to specific actual requirements.

[0177] In some embodiments, the electrode assembly can be assembled into a battery module, and the number of electrode assemblies included in the battery module may be one or more. The specific number can be selected by those skilled in the art according to the use and capacity of the battery module.

[0178] FIG. 5 shows a battery module 4 as an example. Referring to FIG. 5, in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other arbitrary manner. Also, the plurality of secondary batteries 5 can be fixed by fastening means.

[0179] Optionally, the battery module 4 may further include an outer case having a receiving space for accommodating a plurality of secondary batteries 5.

[0180] In some embodiments, the battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0181] FIGS. 6 and 7 show a battery pack 1 as an example. Referring to FIGS. 6 and 7, the battery pack 1 can include a battery case and a plurality of battery modules 4 installed in the battery case. The battery case includes an upper housing 2 and a lower housing 3. The upper housing 2 can cover the lower housing 3 and form a sealed space for accommodating the battery module 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0182] Further, the present application further provides a power consumption device including at least one of the electrode assembly, battery module, or battery pack according to the present application. The electrode assembly, battery module, or battery pack may be used as a power source of the power consumption device or as an energy storage element of the power consumption device. The power consumption device can include, but is not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships, satellites, energy storage systems, etc.

[0183] As the power consumption device, the electrode assembly, battery module, or battery pack can be selected according to its usage requirements.

[0184] FIG. 8 shows a power consumption device as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of high output and high energy density of the electrode assembly of the power consumption device, a battery pack or a battery module can be used.

[0185] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is generally required to be lightweight and thin, and an electrode assembly can be used as a power source.

[0186] Examples Hereinafter, examples of the present application will be described. The examples described below are exemplary and are merely for explaining the present application, and should not be understood as limiting the present application. When specific techniques or conditions are not shown in the examples, they are carried out according to the techniques or conditions described in the literature in this field or according to the product manuals. When the manufacturer of the reagent or equipment used is not described, all are commercially available general products.

[0187] Example 1 Production of Acrylic Acid Ester Copolymer Production Example 1 (1) Add 150 g of deionized water and 3.6 g of sodium dodecyl sulfate to a 500 ml three-necked flask, stir well for 15 min to emulsify, and in a mass ratio of 1:0.01:0.08, add 91.74 g of ethyl acrylate, an acrylic acid ester monomer, 0.92 g of acrylonitrile, an acrylonitrile monomer, and 7.34 g of N-methylolacrylamide, an acrylamide monomer in sequence. The total amount of monomers is 100 g. Stir well for 60 min to obtain a preliminary emulsion of the monomers, take it out and prepare for use.

[0188] (2) Add 100 ml of deionized water and 0.15 g of sodium dodecylbenzenesulfonate to a 500 ml three-necked flask, heat to 75 °C, emulsify at a rotation speed of 2000 r / min for 15 min. After the system is sufficiently emulsified, slowly drop the pre-emulsion and initiator solution prepared in the previous step (dissolve 0.2 g of potassium persulfate as the initiator in 30 g of deionized water to form a solution). After the dropping is completed, raise the temperature to 90 °C and keep it for 0.5 h for a holding reaction. Cool to 40 °C, adjust the pH to 7 using ammonia water, then stop stirring, filter, and discharge to obtain an acrylate copolymer emulsion. The volume-based particle size distribution Dv50 of the acrylate copolymer is 0.1 μm ± 0.01 μm (the volume-based particle size distribution Dv50 of the polymer with a shell layer structure in each example is 0.1 μm ± 0.01 μm).

[0189] Production Examples 2 to 10 Based on Production Example 1, change the types and mass ratios of the monomers to be input to obtain Production Examples 2 to 10.

[0190] Production of Binder Example 1 Disperse 100 g of the acrylate copolymer emulsion (containing 100 g of the acrylate copolymer) in Production Example 1 and 100 g of polypropylene particles with a volume-based particle size distribution Dv50 of 1 μm at high speed for 60 min. After uniformly stirring, spray-dry to obtain a binder with a core-shell structure. The parameters of the spray drying are an intake air temperature of 110 °C and an exhaust air temperature of 50 °C.

[0191] Examples 2 to 31 Based on Example 1, adjust the types, mass ratios of the polymers in the core layer structure and the shell layer structure, the volume-based particle size distribution Dv50 of the core layer structure, and the volume-based particle size distribution Dv50 of the binder to obtain Examples 2 to 31.

[0192] Comparative Example 1 Based on Example 1, adjust the mass ratio value of the mass of the shell layer structure to the mass of the core layer structure to 1:0, that is, there is no core layer structure, and Comparative Example 1 is obtained.

[0193] Manufacture of Cells and Manufacture of Batteries 1. Manufacture of Separator A commercially available PE porous film with a thickness of 7 μm and an average pore diameter of 80 nm (obtained from Zhuogao Electronic Technology Co., Ltd.) is used as the base material. The binder manufactured by the above method is uniformly stirred and mixed in deionized water to obtain a paste (solid content: 20%). The paste is uniformly coated on both sides of the base material and dried to remove the solvent. The coating density of the coating composition on the base material is 1.5 g / m 2 and a separator is obtained.

[0194] 2. Manufacture of Positive Electrode Sheet A positive electrode paste is manufactured by sufficiently stirring and uniformly mixing polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), carbon black as a conductive agent, and N-methylpyrrolidone (NMP) at a mass ratio of 1.2:58.38:0.42:40. The positive electrode paste is uniformly coated on an aluminum foil of a positive electrode current collector at a loading amount of 200 g / m 2 and then, through drying, cold pressing, and cutting, a positive electrode sheet is obtained.

[0195] 3. Manufacture of Negative Electrode Sheet Artificial graphite, acetylene black as a conductive agent, styrene-butadiene rubber (SBR) as a binder, and sodium carboxymethyl cellulose (CMC-Na) as a thickener are added to deionized water at a mass ratio of 96.2:1.0:1.6:1.2 and sufficiently stirred and uniformly mixed to manufacture a negative electrode paste (solid content: 63%). The negative electrode paste is coated on a copper foil of a negative electrode current collector at a loading amount of 98 g / m 2 and then, through drying, cold pressing, and cutting, a negative electrode sheet is obtained.

[0196] 4. Manufacture of Electrolyte At 25°C, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed at a volume ratio of 1:1:1 to obtain a mixed solvent. Next, LiPF 6 is dissolved in the above mixed solvent to obtain an electrolyte, and LiPF 6The concentration is 1 mol / L.

[0197] 5. Manufacture of secondary battery The above positive electrode sheet, separator, and negative electrode sheet are laminated and wound in sequence, and cold press molding is performed (during which the separator and the polar sheet are adhered), a cell is obtained, the cell is placed in an exterior material, the above-prepared electrolyte is added, sealed, left standing, formed, aged, etc., and a secondary battery is obtained through these processes.

[0198] Performance test 1. Cold press adhesion: The negative electrode sheet and the separator of the battery are overlapped and placed on a hot press machine. The parameters of the hot press machine are set to a temperature of 25°C, a pressure of 10 t, and a time of 30 s, and pressure is applied to obtain a adhered separator / positive electrode sheet sample. The separator / negative electrode sheet sample is cut into a rectangular strip of 150 mm × 20 mm. One side of the polar sheet of the above rectangular strip is pasted to a steel plate with double-sided tape. At one end of the rectangular strip, the separator and the polar sheet are separated by 2 cm in the length direction to create a test sample.

[0199] The steel plate is held horizontally and fixed with the lower clamp of a universal testing machine (manufactured by Xieqiang Instrument Manufacturing (Shanghai) Co., Ltd., model number CTM2100). The peeling end of the above separator is fixed with the upper clamp of the universal testing machine and connected to a tensile machine. The measurement conditions are set to a tensile speed of 20 mm / min and a horizontal tensile of 10 cm. After the tensile force is stable, the value of the tensile force is recorded, and the adhesion force between the separator and the polar sheet is obtained based on the ratio of the value of the tensile force to the sample width.

[0200] 2. Cell hardness: The cell is placed on a platform with both ends horizontal, the width of the central hollow part is fixed at 12 cm, the cell is placed flat naturally, and the width by which the center position of the cell deviates from the horizontal reference line is measured, thereby evaluating the hardness of the cell.

[0201] 3. EIS data: Using the CHI660D electrochemical workstation of Shanghai Chenhua Company, a sinusoidal voltage signal with a small amplitude and a frequency of W1 is applied to the battery system. The system generates a sinusoidal current response with a frequency of W2. The change in the ratio of the excitation voltage to the response current is the impedance spectrum of the electrochemical system. In the measurement of alternating current impedance, the measurement frequency range is 10 mHz to 100 kHz, and the amplitude is 5 mV. Through measurement, information such as the real part and imaginary part of the impedance at different frequencies can be obtained.

[0202] 4. Cycle characteristics of lithium-ion batteries: Using the LAND battery measurement system, at 25°C, the manufactured battery is charged to 3.65 V at a constant current of 1 / 3C, and then charged at a constant voltage of 3.65 V until the current reaches 0.05C. After standing for 5 minutes, it is discharged to 2.5 V at 1 / 3C. The obtained discharge capacity is used as the initial capacity C0. The above steps are repeated for the same battery, and at the same time, the discharge capacity Cn of the battery after 500 cycles is recorded. The battery capacity retention rate Pn after each cycle is Pn = (Cn / C0) × 100%. The difference in cycle characteristics can be represented by the battery capacity retention rate at a specific number of cycles.

[0203] Manufacturing parameter table of acrylate copolymer emulsion

Table 1

[0204] Manufacturing parameter table of binder

Table 2-1

Table 2-2

Table 2-3

[0205] As can be seen from the above data, a binder including a shell layer structure of an acrylate copolymer and a core layer structure of a high-rigidity polymer can be applied to a battery, improving the adhesion of cold pressing of the cell, improving the cell hardness, simultaneously helping to reduce the electrical and chemical impedance, and improving the cycle characteristics of the secondary battery.

[0206] The above are only preferred embodiments of the present application, not limiting the scope of the patent of the present application. Under the application concept of the present application, any equivalent structural transformation carried out using the content of the specification and drawings of the present application, or direct / indirect application to other related technical fields is included within the protection scope of the patent of the present application.

Claims

1. A binder for a secondary battery, comprising a core layer structure and a shell layer structure provided on the surface of the core layer structure, the shell layer structure containing an acrylate copolymer, the core layer structure containing a high-rigidity polymer, and the range value of the crystallinity of the high-rigidity polymer being 32% to 94%.

2. The binder for a secondary battery according to Claim 1, wherein the range of the crystallinity of the high-rigidity polymer is 40% to 80%.

3. The binder for a secondary battery according to Claim 1 or 2, wherein the high-rigidity polymer contains at least one of polyethylene, polypropylene, polystyrene, polymethyl methacrylate, and polyamide.

4. The binder for a secondary battery according to any one of Claims 1 to 3, wherein the shape of the binder includes a spherical shape.

5. The binder for a secondary battery according to any one of Claims 1 to 4, wherein the volume-based particle size distribution Dv50 of the binder is 1 μm to 15 μm, and preferably, the volume-based particle size distribution Dv50 of the binder is 1 μm to 12 μm.

6. The binder for a secondary battery according to any one of Claims 1 to 5, wherein the ratio of the volume-based particle size distribution Dv50 of the acrylate copolymer to the volume-based particle size distribution Dv50 of the high-rigidity polymer is 1:(1 to 50).

7. The volume-based particle size distribution Dv50 of the high-rigidity polymer is 0.1 μm to 5 μm, and preferably, the volume-based particle size distribution Dv50 of the high-rigidity polymer is 0.5 μm to 2 μm, and / or the volume-based particle size distribution Dv50 of the acrylate copolymer is 100 nm to 200 nm, and preferably, the volume-based particle size distribution Dv50 of the acrylate copolymer is 130 nm to 180 nm. The binder for a secondary battery according to Claim 6.

8. The binder for a secondary battery according to any one of Claims 1 to 7, wherein the ratio of the mass of the shell layer structure to the mass of the core layer structure is 1:(0.1 to 10), and preferably, the ratio of the mass of the shell layer structure to the mass of the core layer structure is 1:(0.1 to 5).

9. The binder for a secondary battery according to any one of Claims 1 to 8, wherein the constituent monomers of the acrylate copolymer contain at least two of acrylate monomers, acrylonitrile monomers, and acrylamide monomers.

10. The acrylic ester monomer includes at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate, and / or the acrylonitrile monomer includes at least one of acrylonitrile or methacrylonitrile, and / or the acrylamide monomer includes at least one of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide. The binder for a secondary battery according to claim 9.

11. The constituent monomers of the acrylic ester copolymer include an acrylic ester monomer, an acrylonitrile monomer, and an acrylamide monomer. The mass ratio of the acrylic ester monomer, the acrylonitrile monomer, and the acrylamide monomer is 1:(0.01 - 0.8):(0.01 - 0.15), and preferably, the mass ratio of the acrylic ester monomer, the acrylonitrile monomer, and the acrylamide monomer is 1:(0.1 - 0.6):(0.06 - 0.12). The binder for a secondary battery according to any one of claims 1 to 10.

12. A method for manufacturing a binder for a secondary battery according to any one of claims 1 to 11, including the step of manufacturing an acrylic ester copolymer emulsion, and the step of mixing the acrylic ester copolymer emulsion and a high-rigidity polymer and performing spray drying to obtain a binder having a core-shell structure. A method for manufacturing a binder for a secondary battery.

13. The step of manufacturing an acrylic ester copolymer emulsion is the step of stirring and emulsifying water, an emulsifier, and the constituent monomers of the acrylic ester copolymer to obtain a preliminary emulsion of the monomers, A step of emulsifying an emulsifier and water by stirring, adding the pre-emulsion and an initiator under heating conditions, raising the temperature, and obtaining an acrylate copolymer emulsion, which is included in the method for manufacturing a binder for a secondary battery according to claim 12.

14. A separator including a base film and an adhesive layer provided on at least one side of the base film, wherein the adhesive layer includes the binder for a secondary battery according to any one of claims 1 to 11. Or, the adhesive layer includes a binder manufactured by the method for manufacturing a binder for a secondary battery according to claim 12 or 13.

15. A secondary battery including the separator according to claim 14.

16. A power consumption device including the secondary battery according to claim 15.

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