Composite fluoropolymer binder and methods of making same, composite binder material and method for producing same, electrode, energy storage device, binder powder for electrochemical device and method for producing same, binder for electrochemical device, electrode mixture, electrode for secondary battery, and secondary battery

Abstract

To provide a binder powder for an electrochemical device capable of providing an electrode mixture sheet having excellent uniformity of tensile strength.SOLUTION: Composite binder materials for energy storage applications are disclosed. The composite binder materials include a fluoropolymer, such as polytetrafluoroethylene (PTFE), integrated with a conductive additive and a low-melting point thermoplastic. Methods of making the composite binder materials are also disclosed. The methods include providing an emulsion of the fluoropolymer, mixing the low-melting point thermoplastic and the particulate conductive additive into the emulsion of the fluoropolymer to form a mixture, and coagulating the mixture to produce a coagulum including the composite binder material. The disclosure also provides a binder powder for an electrochemical device capable of providing an electrode mixture sheet having excellent uniformity of tensile strength. The disclosure relates to a binder powder for an electrochemical device, containing a non-fibrillated fibrillatable resin and a thermoplastic polymer.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure generally relates to composite fluoropolymer binder materials for energy storage devices and methods for manufacturing the same.

[0002] The present disclosure relates to composite binder materials and methods for manufacturing the same, electrodes, energy storage devices, binder powders for electrochemical devices and methods for manufacturing the same, binders for electrochemical devices, electrode binders, electrodes for secondary batteries, and secondary batteries.

Background Art

[0003] Generally, binder materials are combined with electrode active materials and other additives and processed to form electrode films. In current methods for forming cathodes, polyvinylidene difluoride (PVdF) is mixed with a solvent such as N-methylpyrrolidone (NMP), and further mixed with a conductive aid such as carbon black and / or carbon nanotubes, and an electrode material to create a slurry. Anodes are generally made by an aqueous solution method, and the most commonly used binder in this method is styrene butadiene rubber / carboxymethyl cellulose (SBR-CMC). The resulting suspension is cast onto a current collector of an aluminum cathode or a copper anode, or other metal alloys used in batteries. Although current manufacturing processes are well known, there are several drawbacks, such as the use of PVdF with a high dielectric constant (greater than 3.0), considerations regarding the safety, environment, and cost of NMP.

[0004] Polytetrafluoroethylene (PTFE) is known as an alternative to PVdF. However, since PTFE is insoluble in NMP, it cannot be used in the current method. Another problem regarding PTFE and PVdF is that both of these fluoropolymers are insulators. When it is necessary to pass an electric current through the cathode, it is necessary to add a conductive aid to PTFE or PVdF. Conductive aids such as carbon black dry-mixed with PTFE do not disperse well in the PTFE matrix, resulting in poor conductivity. Furthermore, since PTFE has a high melting point, it retains its shape even when melted. That is, PTFE does not flow on any surface and does not form a mechanical bond. Additionally, even if PTFE could be made to flow, the temperature required to melt PTFE exceeds the upper limit temperature of many of the heating devices commonly used in the manufacturing process.

[0005] Therefore, in the relevant technical field, there remains a need for a binder material for energy storage applications that can overcome the technical problem of obtaining a homogeneous mixture of PTFE and a conductive aid.

[0006] Patent Document 1 describes a dry electrode film for an energy storage device, which includes a dry active material, a dry binder including a fibrillated binder and fine particulate non-fibrillated binders having a D 50 particle size of about 0.5 to 40 μm, and is a self-supporting dry electrode film.

[0007] Patent Document 2 describes an electrode film that is an independent dry electrode film provided with a mixed binder material having polytetrafluoroethylene (PTFE) and polyethylene oxide (PEO) and does not contain solvent residues.

[0008] Patent Document 3 describes a non-aqueous electrolyte battery comprising a positive electrode active material mixture composed of at least a positive electrode active material, a conductive agent, and a binder, wherein the binder is a mixed binder composed of a first binder that binds the positive electrode active material mixture by fibrillating and a second binder that binds the positive electrode active material mixture by melting.

[0009] Patent Document 4 describes a method for manufacturing an electrode for an electrochemical cell, particularly a battery cell such as a lithium cell, which includes a step of high-shear mixing at least one binder and at least one particulate fibrillation aid to fibrillate the binder, and a step of low-shear mixing at least one electrode component with at least one fibrillated binder.

[0010] Patent Document 5 describes an energy storage device comprising a cathode, an anode, and a separator disposed between the cathode and the anode, wherein at least one of the cathode and the anode contains a polytetrafluoroethylene (PTFE) mixed binder material, and the PTFE mixed binder material has at least one of polyvinylidene fluoride (PVDF), a PVDF copolymer, and polyethylene oxide (PEO) and polytetrafluoroethylene (PTFE).

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

SUMMARY OF THE INVENTION

[0012] The above problems and other problems are addressed by the following invention, but it should be understood that not all embodiments of the invention described herein address each of the above problems. The present disclosure provides a composite binder material in which a fluoropolymer such as PTFE is integrated with a low melting point thermoplastic resin such as a low melting point fluoropolymer and a conductive aid. The composite binder material can be used, for example, as a binder for energy storage applications such as in a cathode or an anode. Further, by adding a melt-processable fluoropolymer, it becomes easier to adhere the composite binder material to a current collector used in a battery.

[0013] In a first aspect, there is provided a composite binder material comprising polytetrafluoroethylene (PTFE), a low melting point thermoplastic resin, and a conductive aid.

[0014] In a second aspect, there is provided a method for producing a composite binder material, the method including a step of obtaining a PTFE emulsion, a step of mixing the PTFE emulsion with low melting point thermoplastic resin and conductive aid particles to form a first mixture, and a step of coagulating the first mixture to produce a coagulate composed of the composite binder material.

[0015] In a third aspect, there is provided a composite binder produced by the production method of the second aspect.

[0016] In a fourth aspect, there is provided an electrode including the composite binder material of the first aspect or the third aspect.

[0017] In a fifth aspect, there is provided an energy storage device including the electrode of the fourth aspect.

PROBLEMS TO BE SOLVED BY THE INVENTION

[0018] An object of the present disclosure is to provide a binder powder for an electrochemical device capable of obtaining an electrode binder sheet excellent in tensile strength uniformity.

Means for Solving the Problems

[0019] The present disclosure relates to a binder powder for an electrochemical device containing a non-fibrillated resin having fibrillating properties and a thermoplastic polymer.

[0020] The thermoplastic polymer is preferably a thermoplastic resin.

[0021] The thermoplastic resin preferably has a melting point of 100 to 310°C.

[0022] The thermoplastic resin is preferably a fluoropolymer.

[0023] The thermoplastic resin preferably has a melt flow rate of 0.01 to 500 g / 10 min.

[0024] The thermoplastic polymer is preferably an elastomer having a glass transition temperature of 25°C or lower.

[0025] The elastomer is preferably a fluoroelastomer.

[0026] The fluoroelastomer preferably contains a vinylidene fluoride unit and other monomer units copolymerizable with vinylidene fluoride.

[0027] The resin having fibrillating properties preferably has a glass transition temperature of 10 to 30°C.

[0028] The resin having fibrillating properties is preferably polytetrafluoroethylene.

[0029] It is preferable to contain 50% by mass or more of the polytetrafluoroethylene.

[0030] The above-mentioned polytetrafluoroethylene preferably has a peak temperature of 333 to 347°C.

[0031] The above-mentioned binder powder preferably has a water content of 1000 mass ppm or less.

[0032] The above-mentioned binder powder preferably has an average primary particle diameter of 10 to 500 nm.

[0033] The resin having fibrillation properties is in the form of particles, and the ratio of the number of resin particles having fibrillation properties with an aspect ratio of 30 or more to the total number of resin particles having fibrillation properties is preferably 20% or less.

[0034] The above-mentioned binder powder preferably has an average particle diameter of 1000 μm or less.

[0035] The above-mentioned binder powder is preferably for a secondary battery.

[0036] The above-mentioned binder powder preferably further contains a carbon-based conductive aid.

[0037] The present disclosure also relates to an electrode binder obtained by using the above-mentioned binder powder for an electrochemical device.

[0038] The above-mentioned electrode binder is preferably obtained by using an active material.

[0039] The above-mentioned electrode binder is preferably a positive electrode binder.

[0040] The present disclosure also relates to an electrode for a secondary battery obtained by using the above-mentioned binder powder for an electrochemical device.

[0041] The present disclosure also relates to a secondary battery including the above-mentioned electrode for a secondary battery.

[0042] The present disclosure also relates to a method for manufacturing a binder powder for an electrochemical device, including a step (1) of preparing a mixture containing a fibrillatable resin, a thermoplastic polymer, and water, and a step (2) of producing a powder from the above mixture.

[0043] Preferably, the above step (2) includes a step (2-1) of aggregating a composition containing the fibrillatable resin and the thermoplastic polymer from the above mixture to obtain an aggregate, and a step (2-2) of heat-treating the above aggregate.

[0044] In the above step (1), it is preferable to mix a dispersion liquid containing the thermoplastic polymer having an average primary particle diameter of 50 μm or less with the fibrillatable resin and water.

[0045] The present disclosure also relates to a binder for an electrochemical device, including a fibrillatable resin and an ethylene / tetrafluoroethylene copolymer.

[0046] The present disclosure also relates to a binder for an electrochemical device, including a fibrillatable resin and an elastomer having a glass transition temperature of 25°C or less.

[0047] Preferably, the binder for the electrochemical device is in powder form.

[0048] Preferably, the above elastomer is a fluoroelastomer.

[0049] Preferably, the above fluoroelastomer contains vinylidene fluoride units and other monomer units copolymerizable with vinylidene fluoride.

[0050] Preferably, the fibrillatable resin has a glass transition temperature of 10 to 30°C.

[0051] Preferably, the fibrillatable resin is polytetrafluoroethylene.

[0052] It is preferable to contain 50 mass% or more of the above-mentioned polytetrafluoroethylene.

[0053] The above-mentioned polytetrafluoroethylene preferably has a peak temperature of 333 to 347 °C.

[0054] The above-mentioned binder preferably has a water content of 1000 mass ppm or less.

[0055] The above-mentioned binder preferably has an average primary particle diameter of 10 to 500 nm.

[0056] The above-mentioned binder is preferably for secondary batteries.

[0057] The above-mentioned binder preferably contains a carbon-based conductive assistant.

[0058] The present disclosure also relates to an electrode binder obtained by using the above-mentioned binder for an electrochemical device.

[0059] The above-mentioned electrode binder preferably further contains an active material.

[0060] The above-mentioned electrode binder is preferably a positive electrode binder.

[0061] The present disclosure also relates to an electrode for a secondary battery obtained by using the above-mentioned binder for an electrochemical device.

[0062] The present disclosure also relates to a secondary battery including the above-mentioned electrode for a secondary battery.

Advantages of the Invention

[0063] According to the present disclosure, it is possible to provide a binder powder for an electrochemical device that can obtain an electrode binder sheet excellent in the uniformity of tensile strength.

Brief Description of the Drawings

[0064] Additional features and advantages will become apparent from the following detailed description provided in connection with the drawings described below.

[0065]

Figure 1

[0066]

Figure 2

[0067]

Figure 3

[0068]

Figure 4

[0069]

Figure 5

[0070]

Figure 6

[0071]

Figure 7

[0072]

Figure 8

[0073]

Figure 9

[0074]

Figure 10-1

Figure 10-2

[0075]

Figure 11

DETAILED DESCRIPTION OF THE INVENTION

[0076] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Further, terms as defined in commonly used dictionaries shall be interpreted to have a meaning that conforms to their meaning in the context of this specification, and it should be understood that they should not be interpreted in an idealized or overly formal sense unless explicitly defined as such herein. Well-known functions and structures may not be described in detail for the sake of brevity and clarity.

[0077] The terms “about” and “approximately” generally mean an acceptable degree of error or variation of a measured quantity, taking into account the nature or precision of the measurement. Typical and exemplary degrees of error or variation are within 20% of a given value or range of values, preferably within 10%, more preferably within 5%, and even more preferably within 1%. Numerical quantities described in this specification are approximate values unless otherwise noted. This means that the term “about” or “approximately” can be inferred when not explicitly stated.

[0078] The terms used in this specification are for the purpose of describing particular embodiments only and are not intended to be limiting. In this specification, the singular forms “a,” “an,” and “the” are intended to include the plural forms (i.e., “at least one”) unless the context clearly dictates otherwise.

[0079] In this specification, terms such as “first,” “second,” etc. are used to describe various features and elements, but these features and elements should not be limited by these terms. These terms are used only to distinguish one feature or element from another. Thus, without departing from the teachings of this disclosure, the first feature or element described hereinafter may be referred to as the second feature or element, and similarly, the second feature or element described hereinafter may be referred to as the first feature or element.

[0080] Terms such as "at least one of A and B" should be understood to mean "only A, only B, or both A and B". The same syntax should apply to longer lists (e.g., "at least one of A, B, and C").

[0081] The term "consisting essentially of" means that, unless it adversely affects the operability of what is claimed for the intended purposes described in this disclosure, what is claimed may include other elements (processes, structures, components, members, etc.) in addition to the recited elements. This term excludes other elements that would adversely affect the operability of what is claimed for the intended purposes described in this disclosure, even if such other elements might improve the operability of what is claimed for other purposes.

[0082] As used herein, the term "may" refers to an optional (i.e., "it may or may not") feature and should not be construed as limiting the recited content.

[0083] It should be understood that any given element of the disclosed embodiments of the present invention may be embodied in a single structure, a single process, a single substance, etc. Similarly, a given element of the disclosed embodiments may be embodied in a plurality of structures, processes, substances, etc.

[0084] Composite binder material

[0085] This disclosure provides a composite binder material for energy storage applications. Various embodiments of the composite binder material described herein have one or more of the following advantages: "providing a mixture in which a fluoropolymer such as PTFE integrated with a conductive aid and a low melting point thermoplastic is homogeneously and well-dispersed", "being conductive", "being able to adhere to a metal such as a current collector on an electrode".

[0086] In one embodiment, the composite binder material includes a fluoropolymer such as polytetrafluoroethylene (PTFE). In one embodiment, the PTFE may be a PTFE homopolymer or may include a perfluorinated copolymer. In another embodiment, the PTFE may be modified PTFE. "Modified PTFE" refers to a homopolymer of tetrafluoroethylene that contains no more than 1 wt% of other fluoromonomers (see ASTM D4895-15). The modified PTFE may include tetrafluoroethylene (TFE) units and modified monomer units based on modified monomers copolymerizable with TFE. The modified monomer is not particularly limited as long as it is a monomer copolymerizable with TFE. In some embodiments, the modified monomer may be partially fluorinated or fully fluorinated. Examples of partially fluorinated or fully fluorinated modified monomers include perfluoroolefins such as hexafluoropropylene (HFP), chlorofluoroolefins such as chlorotrifluoroethylene (CTFE), hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride (VDF), perfluoroalkyl vinyl ethers having an alkyl chain of 1, 2, 3, 4, 5, 6, 7, or 8 carbon atoms, perfluoroalkyl ethylene, ethylene, and nitrile group-containing fluorinated vinyl ethers. In other embodiments, the modified monomer may not contain fluorine.

[0087] The molecular weight of the fluoropolymer such as PTFE can be represented by the standard specific gravity (SSG) conventionally used as a reference for the molecular weight of PTFE (see ASTM D-4441-15, ASTM D-4894-19, or ASTM D-4895-18). The relationship between SSG and the number-average molecular weight (Mn) is shown by Equation 1 below. SSG = -0.0579(ln(Mn)) + 2.6113 (1)

[0088] In some embodiments, the PTFE may be high molecular weight PTFE with a standard specific gravity of at least 2.150. In yet another embodiment, the PTFE may be high molecular weight PTFE with a standard specific gravity of at least 2.160. In yet another embodiment, the PTFE may be high molecular weight PTFE with a standard specific gravity of at least 2.170. The PTFE may be high molecular weight PTFE with a standard specific gravity of 2.20 or less.

[0089] The PTFE may be present in the composite binder material in an amount of about 25% to about 99% by mass. In another embodiment, the PTFE may be present in the composite binder material in an amount of about 40% to about 99% by mass. In yet another embodiment, the PTFE may be present in the composite binder material in an amount of about 60% to about 99% by mass.

[0090] The composite binder material of the present disclosure may also include a low melting point thermoplastic resin. As used herein, "low melting point thermoplastic resin" refers to a polymer having a melting point of 375°C or lower, preferably 200°C or lower. As a result, the polymer can be melt processed at the processing temperatures disclosed herein. For example, the low melting point thermoplastic resin must be processable with a screw extruder such that the polymer can be pushed through a die with a screw when the processing temperature exceeds the melting point of the polymer. Without being bound by a particular theory, the low melting point thermoplastic resin is thought to facilitate adhesion of the binder material to a substrate such as a current collector for cathodes and anodes.

[0091] In one embodiment, the low melting point thermoplastic resin is a low melting point fluoropolymer. Suitable low melting point fluoropolymers include, but are not limited to, polyvinylidene fluoride (PVdF), fluorinated ethylene-propylene (FEP), ethylene-fluorinated ethylene-propylene (EFEP), ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene, hexafluoropropylene and vinylidene fluoride (THV), fluoroelastomers (e.g., FKM, FFKM, etc.), polyperfluoroalkoxy alkane (PFA), polyvinyl fluoride (PVF), and alloys and blends thereof. In a preferred embodiment, the low melting point fluoropolymer is EFEP.

[0092] In other embodiments, the low melting point thermoplastic resin may be a low melting point non-fluorinated polymer. Examples of low melting point non-fluorinated polymers include, but are not limited to, polyolefins (such as polyethylene (PE) and polypropylene (PP)), polyamides (PA, nylon, etc.), polystyrene (PS), thermoplastic polyurethane (TPU), polyimide (PI), polyacrylate (PA), polycarbonate (PC), polylactic acid (PLA), polyether ether ketone (PEEK), polyethylene glycol (PEG / PEO), and alloys and blends containing these.

[0093] The low melting point thermoplastic resin may be used in particulate form. For example, in some embodiments, the low melting point thermoplastic resin is used in powder form. In one embodiment, the average particle size of the powdered low melting point thermoplastic resin, measured by scanning electron microscopy (SEM), is about 700 μm or less. In another embodiment, the average particle size of the low melting point thermoplastic resin is about 500 μm or less. In yet another embodiment, the average particle size of the low melting point thermoplastic resin is about 300 μm or less. In yet another embodiment, the average particle size of the low melting point thermoplastic resin is about 100 μm or less. In another embodiment, the average particle size of the low melting point thermoplastic resin is about 50 μm or less.

[0094] The above-mentioned low melting point thermoplastic resin in some embodiments is used in the form of an emulsion. In this embodiment, the average primary particle diameter of the above-mentioned low melting point thermoplastic resin may be about 500 nm or less. In a further embodiment, the average primary particle diameter of the above-mentioned low melting point thermoplastic resin may be about 450 nm or less. In yet another embodiment, the average primary particle diameter of the above-mentioned low melting point thermoplastic resin may be about 400 nm or less. In yet another embodiment, the average primary particle diameter of the above-mentioned low melting point thermoplastic resin may be about 350 nm or less. In yet another embodiment, the average primary particle diameter of the above-mentioned low melting point thermoplastic resin may be about 300 nm or less. In yet another embodiment, the average primary particle diameter of the above-mentioned low melting point thermoplastic resin may be about 250 nm or less. For example, the average primary particle diameter of the above-mentioned low melting point thermoplastic resin may be 240, 230, 220, 210, 200, 190, 180, 170, 160, 150, 140, 130, 120, 110, or 100 nm.

[0095] The above-mentioned low melting point thermoplastic resin may be present in the above-mentioned composite binder material in an amount of about 0.01 to about 50% by mass. In a further embodiment, the above-mentioned low melting point thermoplastic resin may be present in the above-mentioned composite binder material in an amount of about 1 to about 35% by mass. In yet another embodiment, the above-mentioned low melting point thermoplastic resin may be present in the above-mentioned composite binder material in an amount of about 5 to about 20% by mass. In yet another embodiment, the above-mentioned low melting point thermoplastic resin may be present in the above-mentioned composite binder material in an amount of about 5 to about 10% by mass.

[0096] The composite binder material of the present disclosure may further include a conductive aid. The conductive aid enhances the dielectric properties of the composite binder material. In one embodiment, the conductive aid is conductive carbon. For example, the conductive aid may be carbon nanoparticles, carbon nanotubes, carbon black, acetylene black, graphite, or a combination of two or more of the above. The conductive aid may be present in the composite binder material at about 0.01% to about 20% by mass. More specifically, the conductive aid may be present in the composite binder material at about 1% to about 15% by mass. More specifically, the conductive aid may be present in the composite binder material at about 2% to about 10% by mass.

[0097] The composite binder material of the present disclosure exhibits excellent adhesive strength. In some embodiments, the composite binder material of the present disclosure has an adhesive strength with high-purity aluminum measured by an adhesion test using a 25-mm wide film having high-purity aluminum on both sides that exceeds 1 N / mm. The composite binder material of further embodiments has an adhesive strength exceeding 1.5, 2, or 2.5 N / mm in the same measurement.

[0098] When referring to the adhesion peel test, it refers to the adhesion peel test method described in the Examples section of the present disclosure.

[0099] Method for manufacturing a composite binder material

[0100] The present disclosure provides a method for manufacturing the above composite binder material. In one embodiment, the method includes a step of obtaining an emulsion of the above fluoropolymer such as PTFE. The above fluoropolymer emulsion can be obtained by various suitable methods. For example, a PTFE emulsion may be prepared by aqueous polymerization of tetrafluoroethylene in the presence of an emulsifier, paraffin wax, and an initiator. The above wax may be separated from the emulsion by decanting the above emulsion from a light wax phase. In some embodiments, the above emulsion may be aggregated to separate the above fluoropolymer such as PTFE from water. By this step, secondary particles composed of the above fluoropolymer are formed.

[0101] After the formation of the above fluoropolymer emulsion, for example, a PTFE emulsion, the method includes a step of mixing the above low melting point thermoplastic resin and the particulate conductive aid into the above fluoropolymer emulsion to form a mixture. In this embodiment, the above low melting point thermoplastic resin and the above particulate conductive aid may be added to the emulsion in any of the above-described amounts. The above low melting point thermoplastic resin may be added in particulate form such as powder, or in the form of an emulsion. In an embodiment where the above low melting point thermoplastic substance is used in the form of an emulsion, the average particle size may be about 500 nm or less. In a further embodiment, the maximum average particle size of the above emulsion may be 450, 400, 350, or 300 nm. The target range of the particle size can be obtained by various suitable means including screening or filtration. After adding the above low melting point thermoplastic resin and the above particulate conductive aid to the above emulsion, the above mixture may be aggregated. In one embodiment, aggregation occurs when sufficient energy is applied to the above mixture, such as by mechanical stirring, and the aggregated secondary particles composed of the above fluoropolymer, the above low melting point thermoplastic resin, and the above particulate conductive aid can precipitate from the above mixture. In a further embodiment, aggregation can be achieved ionically using a monovalent, divalent, or trivalent salt such as an aluminum salt, calcium nitrate, sodium chloride, quaternary salt, or other flocculating salts known in the art.

[0102] The above aggregation step may be carried out at a temperature of about 90 °C or lower. In a further embodiment, the above aggregation step is carried out at a temperature in the range of about 5 to about 30 °C, or about 5 to about 15 °C. Before aggregation, the specific gravity of the above fluoropolymer emulsion may be adjusted to about 1.050 to about 1.100. The above aggregation step may be carried out using any mechanical stirrer capable of adding sufficient energy to promote mixing and separation of the secondary particles from the mixture. For example, the above mechanical stirrer may be an anchor, an impeller, or any other design capable of generating a vortex of the above fluoropolymer emulsion within the stirrer. In a further embodiment, the aggregation vessel may include one or more baffles or other design features to enable aggregation.

[0103] The aggregation process of this method may occur in three stages: an initial stage, a slurry stage, and a post-aggregation stage. In the above-mentioned initial stage, the fluoropolymer, the low-melting-point thermoplastic resin, and the particulate conductive aid are mixed at a low viscosity. When the viscosity of the mixture increases until the vortex in the stirrer disappears or the size of the vortex becomes smaller, it transitions to the above-mentioned slurry stage. When aggregated secondary particles composed of the fluoropolymer integrated with the particulate conductive aid and the low-melting-point thermoplastic resin clearly exist, it transitions to the above-mentioned aggregation stage. The aggregated substance may be decanted from the liquid formed during the above-mentioned aggregation stage. The obtained aggregate forms the above-mentioned composite binder material. In some embodiments, the liquid formed during the above-mentioned aggregation stage is removed, and the obtained slurry may be used as the above-mentioned composite binder material, and in some embodiments, without an aggregate.

[0104] In some embodiments, the method includes a step of drying the aggregate to remove a liquid polymerization medium that can be trapped between particles by capillary force. In one embodiment, the aggregate is dried at a temperature of about 375 °C or lower. In a further embodiment, the aggregate is dried at a temperature of about 300 °C or lower. In yet another embodiment, the aggregate is dried at a temperature of about 200 °C or lower. For example, the aggregate may be dried at a temperature of about 177 °C. After drying, the aggregate may be stored at a temperature of about 20 °C or lower to prevent excessive fibrillation of the fluoropolymer (e.g., PTFE).

[0105] In some embodiments, the composite binder material formed by the manufacturing method of the present disclosure may be mixed with an additional particulate conductive material such as carbon black. In such embodiments, the composite binder material and the additional particulate conductive material may be combined using any mixing or grinding method capable of applying shear to the components. For example, the mixing method may be carried out using any mechanical stirrer that rotates at a high speed to facilitate the mixing of the composite binder material and the additional particulate conductive material.

[0106] The composite binder material may be combined with an electrode active material. Such electrodes are used, for example, as electrodes of batteries or supercapacitors. For example, the electrode active material may be a positive electrode active material such as lithium nickel manganese cobalt oxide (NMC), lithium cobalt oxide (LCO), lithium nickel cobalt aluminum oxide (NCA), lithium iron phosphate (LFP), lithium nickel manganese spinel (LNMO), lithium manganese oxide (LMO), etc., or a negative electrode active material such as graphite, silicon, silicon composite material, pyrolytic carbon, coke, mesocarbon microbeads, carbon fiber, activated carbon, pitch-coated graphite, etc. The composite binder material and the electrode active material may be mixed to form an electrode paste that can be applied to an electrode.

[0107] Usage

[0108] The composite binder materials described herein may be used for energy storage applications. In one embodiment, the present disclosure provides an electrode, such as a cathode or an anode, manufactured by applying an electrode binder comprising the disclosed composite binder material to a current collector. In this embodiment, the electrode binder may be formed by uniformly dispersing an electrode active material, an additional conductive aid, and the composite binder material. The battery active material may be either the cathode active material or the anode active material described above. The battery active material may be added to the electrode binder at about 90% to about 99% by mass. The composite binder material may be added to the electrode binder at about 0.5% to about 10% by mass. The additional conductive aid may be added at about 9.5% by mass or less.

[0109] In one embodiment, the battery active material, the additional conductive aid, and the composite binder material may be dispersed using a low-energy solvent-free mixing process. For example, by uniformly dispersing the components of the electrode binder using a gentle mechanical mixing method before and / or during controlling the fibrillation of the fluoropolymer, the composite binder material and the additional conductive aid may be controllably integrated throughout the battery active material. The mixing method may use planetary stirring and may be performed at a rotational speed in the range of about 10 to about 100 rpm. In some embodiments, the mixing is performed at a temperature in the range of about 5 to about 90 °C.

[0110] The homogeneous electrode binder containing the composite binder material of the present disclosure may be applied to a positive electrode or negative electrode current collector. Examples of the material constituting the current collector include aluminum and its alloys, stainless steel, nickel and its alloys, titanium and its alloys, carbon, conductive resins, and materials produced by treating the surfaces of aluminum or stainless steel with carbon or titanium. The electrode binder can be applied to the current collector using any suitable coating method, such as using a roller or a press system. The coating method may be carried out under ambient conditions. In other embodiments, the coating method may be carried out at a high temperature from approximately room temperature (e.g., 20 °C) to about 375 °C. By using the composite binder material of the present disclosure, the adhesion of the electrode binder to the current collector is improved, and an electrode can be formed when applied to the current collector.

[0111] The present disclosure provides an energy storage device including at least one electrode such as a cathode and / or an anode, and having a current collector coated with an electrode binder containing the composite binder material described herein. In some embodiments, the energy storage device includes at least two electrodes (or exactly two electrodes) containing the composite binder. The energy storage device may be a battery such as a lithium-ion battery. In other embodiments, the energy storage device may be a supercapacitor, an electric double layer capacitor, or a lithium-ion capacitor. In still other embodiments, the energy storage device may be a lithium secondary battery.

[0112] Hereinafter, the present disclosure will be specifically described.

[0113] The present disclosure relates to a binder powder for an electrochemical device containing a resin having fibrillatable property without fibrillation and a thermoplastic polymer. Due to having the above characteristics, the binder powder for the electrochemical device of the present disclosure can obtain an electrode binder sheet excellent in the uniformity of tensile strength. Furthermore, it is also possible to manufacture the electrochemical device at low cost. In addition, when a conductive auxiliary agent is added, it can be uniformly mixed with the fibrillatable resin, so that the adhesiveness between the current collector foil and the electrode binder sheet of the electrochemical device can be improved.

[0114] The inclusion of the non-fibrillated resin having fibrillatability means that the ratio of the number of resin particles having fibrillatability with an aspect ratio of 30 or more to the total number of resin particles having fibrillatability is 20% or less. The ratio of the number of resin particles having fibrillatability with an aspect ratio of 30 or more to the total number of resin particles having fibrillatability is preferably 15% or less, more preferably 10% or less, still more preferably 5% or less, even more preferably 3% or less, particularly preferably 2% or less, even particularly preferably 1% or less, and most preferably 0.5% or less. The ratio of the number of resin particles having fibrillatability with an aspect ratio of 30 or more to the total number of resin particles having fibrillatability is determined by the following method. Using a microscope, a magnified photograph of the resin powder is taken to obtain an image. The magnification can be, for example, 30 to 1000 times. The obtained image is saved on a computer and read with the image analysis software ImageJ. The number of resin particles to be counted is 200 or more. Among the counted resin particles, the number of resin particles having fibrillatability with an aspect ratio of 30 or more is counted, and the percentage is determined.

[0115] The term "containing a resin having fibrillation properties that is not fibrillated" preferably indicates that the ratio of the number of resin particles having fibrillation properties with an aspect ratio of 20 or more to the total number of resin particles having fibrillation properties is 20% or less. The ratio of the number of resin particles having fibrillation properties with an aspect ratio of 20 or more to the total number of resin particles having fibrillation properties is preferably 15% or less, more preferably 10% or less, still more preferably 5% or less, even more preferably 3% or less, particularly preferably 2% or less, extremely preferably 1% or less, and most preferably 0.5% or less. The ratio of the number of resin particles having fibrillation properties with an aspect ratio of 20 or more to the total number of resin particles having fibrillation properties is determined by the following method. Using a microscope, a magnified photograph of the resin powder is taken to obtain an image. The magnification can be, for example, 30 to 1000 times. The obtained image is saved on a computer and read with the image analysis software ImageJ. The number of resin particles to be counted is 200 or more. Among the counted resin particles, the number of resin particles having fibrillation properties with an aspect ratio of 20 or more is counted, and the percentage is determined.

[0116] The term "containing a resin having fibrillation properties that is not fibrillated" more preferably indicates that the ratio of the number of resin particles having fibrillation properties with an aspect ratio of 10 or more to the total number of resin particles having fibrillation properties is 20% or less. The ratio of the number of resin particles having fibrillation properties with an aspect ratio of 10 or more to the total number of resin particles having fibrillation properties is preferably 15% or less, more preferably 10% or less, still more preferably 5% or less, even more preferably 3% or less, particularly preferably 2% or less, extremely preferably 1% or less, and most preferably 0.5% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 10 or more to the total number of fibrillatable resin particles is determined by the following method. Using a microscope, take a magnified photograph of the resin powder to obtain an image. The magnification can be, for example, 30 to 1000 times. Save the obtained image on a computer and load it with the image analysis software ImageJ. The number of resin particles to be counted shall be 200 or more. Among the counted resin particles, count the number of fibrillatable resin particles having an aspect ratio of 10 or more, and determine the percentage.

[0117] Including the above non-fibrillated resin having fibrillatability, more preferably, it indicates that the ratio of the number of fibrillatable resin particles having an aspect ratio of 5 or more to the total number of fibrillatable resin particles is 20% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 5 or more to the total number of fibrillatable resin particles is preferably 15% or less, more preferably 10% or less, still more preferably 5% or less, still more preferably 3% or less, particularly preferably 2% or less, most preferably 1% or less, and particularly preferably 0.5% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 5 or more to the total number of fibrillatable resin particles is determined by the following method. Using a microscope, take a magnified photograph of the resin powder to obtain an image. The magnification can be, for example, 30 to 1000 times. Save the obtained image on a computer and load it with the image analysis software ImageJ. The number of resin particles to be counted shall be 200 or more. Among the counted resin particles, count the number of fibrillatable resin particles having an aspect ratio of 5 or more, and determine the percentage.

[0118] The resin having the fibrillating property preferably has a glass transition temperature of 10 °C or higher, more preferably 15 °C or higher, and preferably 35 °C or lower, more preferably 30 °C or lower, and still more preferably 25 °C or lower.

[0119] As the resin having the fibrillating property, the higher the molecular weight, the easier it is to fibrillate. For example, the molecular weight is 50,000 or more, more preferably 100,000 or more, still more preferably 500,000 or more, and even more preferably 1,000,000 or more. Specifically, polytetrafluoroethylene (PTFE), polyethylene, polyester, LCP, acrylic resin, etc. can be mentioned. As the resin having the fibrillating property, polyethylene, polyester, and polytetrafluoroethylene (PTFE) are preferred, and PTFE is more preferred.

[0120] The binder powder for an electrochemical device of the present disclosure preferably contains 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70% by mass or more of the resin having the fibrillating property. Also, it preferably contains 99% by mass or less, more preferably 98% by mass or less, and still more preferably 95% by mass or less.

[0121] The binder powder for an electrochemical device of the present disclosure preferably contains 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70% by mass or more of the above PTFE based on the powder. Also, it preferably contains 99% by mass or less, more preferably 98% by mass or less, and still more preferably 95% by mass or less.

[0122] The above PTFE preferably has a standard specific gravity (SSG) of 2.200 or less, more preferably 2.180 or less, still more preferably 2.170 or less, even more preferably 2.160 or less, still more preferably 2.150 or less, particularly preferably 2.145 or less, and especially preferably 2.140 or less in terms of improving the adhesive strength, electrode strength, and flexibility of the electrode. The above SSG is preferably 2.130 or more. The above SSG is measured by the water displacement method in accordance with ASTM D 792 using a sample molded in accordance with ASTM D 4895.

[0123] The above PTFE preferably has non-melting secondary processability. The non-melting secondary processability means the property that the melt flow rate cannot be measured at a temperature higher than the melting point in accordance with ASTM D-1238 and D-2116. In other words, it means the property that it does not easily flow even in the melting temperature range.

[0124] The above PTFE may be a homopolymer of tetrafluoroethylene (TFE), or may be a modified PTFE containing a polymerization unit based on TFE (TFE unit) and a polymerization unit based on a modified monomer (hereinafter also referred to as "modified monomer unit"). The above modified PTFE may contain 99.0 mass% or more of TFE units and 1.0 mass% or less of modified monomer units. Further, the above modified PTFE may consist only of TFE units and modified monomer units. As the above PTFE, the above modified PTFE is preferable in terms of improving the adhesion, electrode strength, and flexibility of the electrode.

[0125] The above modified PTFE preferably has a content of modified monomer units in the range of 0.00001 to 1.0 mass% with respect to all polymerization units in terms of improving the stretchability, adhesion, electrode strength, and flexibility of the electrode. As the lower limit of the content of modified monomer units, 0.0001 mass% is more preferable, 0.001 mass% is further preferable, 0.005 mass% is further more preferable, and 0.010 mass% is particularly more preferable. As the upper limit of the content of modified monomer units, 0.90 mass% is preferable, 0.50 mass% is more preferable, 0.40 mass% is further preferable, 0.30 mass% is further more preferable, 0.20 mass% is further more preferable, 0.15 mass% is particularly more preferable, and 0.10 mass% is particularly preferable. In this specification, the above modified monomer unit means a part of the molecular structure of PTFE that is derived from the modified monomer.

[0126] The content of each polymerization unit described above can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis according to the type of monomer.

[0127] The above-mentioned modified monomer is not particularly limited as long as it can copolymerize with TFE. For example, perfluoroolefins such as hexafluoropropylene [HFP]; hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride [VDF]; perhaloolefins such as chlorotrifluoroethylene; perfluorovinyl ether: perfluoroallyl ether; (perfluoroalkyl)ethylene, ethylene, etc. can be mentioned. Also, the modified monomer used may be one type or a plurality of types.

[0128] The above-mentioned perfluorovinyl ether is not particularly limited. For example, the following general formula (A): CF2=CF-ORf (A) (In the formula, Rf represents a perfluoro organic group.) Perfluoro unsaturated compounds represented by the like can be mentioned. In this specification, the above-mentioned "perfluoro organic group" means an organic group in which all hydrogen atoms bonded to carbon atoms are substituted by fluorine atoms. The above-mentioned perfluoro organic group may have an ether oxygen.

[0129] As the above-mentioned perfluorovinyl ether, for example, in the above general formula (A), perfluoro(alkyl vinyl ether) [PAVE] in which Rf is a perfluoroalkyl group having 1 to 10 carbon atoms can be mentioned. The number of carbon atoms of the above-mentioned perfluoroalkyl group is preferably 1 to 5.

[0130] Examples of the perfluoroalkyl group in the above PAVE include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, etc.

[0131] As the perfluorovinyl ether, further in the general formula (A), those in which Rf is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, those in which Rf is a group represented by the following formula:

[0132] [Chemical formula]

[0133] (wherein m represents an integer of 0 or 1 to 4), those in which Rf is a group represented by the following formula:

[0134] [Chemical formula]

[0135] (wherein n represents an integer of 1 to 4), etc. are exemplified.

[0136] (Perfluoroalkyl)ethylene (PFAE) is not particularly limited, and examples thereof include (perfluorobutyl)ethylene (PFBE), (perfluorohexyl)ethylene, and the like.

[0137] As the perfluoroallyl ether, for example, the general formula (B): CF2=CF-CF2-ORf 1 (B) (wherein Rf 1 represents a perfluoro organic group). The fluoromonomer represented by the formula is exemplified.

[0138] The above Rf 1A perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms is preferable. As the above perfluoroallyl ether, at least one selected from the group consisting of CF2=CF-CF2-O-CF3, CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9 is preferable, at least one selected from the group consisting of CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9 is more preferable, and CF2=CF-CF2-O-CF2CF2CF3 is even more preferable.

[0139] As the above modified monomer, at least one selected from the group consisting of PAVE and HFP is preferable in terms of improving stretchability, adhesiveness, and flexibility of the electrode, and at least one selected from the group consisting of perfluoro(methyl vinyl ether) (PMVE) and HFP is more preferable.

[0140] The above PTFE may have a core-shell structure. Examples of the PTFE having a core-shell structure include modified PTFE containing a core of high molecular weight PTFE and a shell of lower molecular weight PTFE or modified PTFE in the particles. Examples of such modified PTFE include PTFE described in JP-T-2005-527652.

[0141] The above PTFE preferably has a peak temperature of 333 to 347 °C, more preferably 335 to 345 °C. When there are a plurality of the above peak temperatures, at least one of them is preferably 340 °C or higher. The above peak temperature is the temperature corresponding to the maximum value in the melting heat curve when the temperature of PTFE without a heating history at a temperature of 300 °C or higher is raised at a rate of 10 °C / min using a differential scanning calorimeter [DSC].

[0142] When the above-mentioned PTFE is heated at a rate of 10 °C / min using a differential scanning calorimeter [DSC] for PTFE without a heating history at a temperature of 300 °C or higher, at least one endothermic peak appears in the melting heat curve in the range of 333 to 347 °C, and it is preferable that the melting heat quantity in the range of 290 to 350 °C calculated from the above melting heat curve is 62 mJ / mg or more.

[0143] The binder powder for an electrochemical device of the present disclosure preferably contains the above thermoplastic polymer in an amount of 0.5% by mass or more, more preferably 1% by mass or more, still more preferably 5% by mass or more, even more preferably 10% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, and even more preferably 25% by mass or less, based on the powder.

[0144] The binder powder for an electrochemical device of the present disclosure preferably contains the above thermoplastic polymer in an amount of 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, and preferably 100% by mass or less, more preferably 75% by mass or less, still more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less, based on the resin having fibrillating properties.

[0145] The above thermoplastic polymer may be a thermoplastic resin or an elastomer having a glass transition temperature of 25 °C or lower.

[0146] The above-mentioned thermoplastic resin preferably has a melting point of 100 °C or higher, more preferably 115 °C or higher, still more preferably 130 °C or higher, even more preferably 160 °C or higher, particularly preferably 210 °C or higher, even more particularly preferably 250 °C or higher, still more particularly preferably 255 °C or higher, especially preferably 295 °C or higher. Also, it preferably has a melting point of less than 324 °C, more preferably 310 °C or lower, still more preferably 275 °C or lower, even more preferably 270 °C or lower, particularly preferably 230 °C or lower, even more particularly preferably 225 °C or lower, still more particularly preferably 200 °C or lower, even more particularly preferably 180 °C or lower, especially preferably 135 °C or lower. In this specification, the melting point is the temperature corresponding to the maximum value in the melting heat curve when the second heating is carried out at a rate of 10 °C / min using a differential scanning calorimeter [DSC].

[0147] Examples of the above-mentioned thermoplastic resin include non-fluorinated polymers such as polyethylene, polypropylene, polyamide, polystyrene, thermoplastic polyurethane, polyimide, polyacrylate, polycarbonate, polylactic acid, polyether ether ketone, and polyethylene glycol; and fluoropolymers. Among them, polyethylene and fluoropolymers are preferred, and fluoropolymers are more preferred.

[0148] The above-mentioned thermoplastic resin preferably has a melt flow rate of 0.01 to 500 g / 10 min, and more preferably 0.1 to 300 g / 10 min. The above-mentioned melt flow rate is obtained as the mass (g / 10 min) of the polymer flowing out per 10 minutes from a nozzle with an inner diameter of 2 mm and a length of 8 mm at the measurement temperature (for example, 372 °C for PFA and FEP, 297 °C for ETFE) and load (for example, 49 N (5 kg) for PFA, FEP, and ETFE) determined according to the type of fluoropolymer using a melt indexer in accordance with ASTM D1238.

[0149] Examples of the above fluoropolymer include tetrafluoroethylene [TFE] / perfluoro(alkyl vinyl ether) [PAVE] copolymer [PFA], TFE / hexafluoropropylene [HFP] copolymer [FEP], ethylene [Et] / TFE copolymer [ETFE], TFE / HFP / VdF copolymer [THV], VdF / TFE copolymer [VT], Et / TFE / HFP copolymer [EFEP], polychlorotrifluoroethylene [PCTFE], chlorotrifluoroethylene [CTFE] / TFE copolymer, Et / CTFE copolymer, polyvinyl fluoride [PVF], polyvinylidene fluoride [PVdF], and the like.

[0150] Although not particularly limited, as PFA, a copolymer in which the molar ratio of TFE units to PAVE units (TFE units / PAVE units) is 70 / 30 or more and less than 99 / 1 is preferable. A more preferable molar ratio is 70 / 30 or more and 98.9 / 1.1 or less, a still more preferable molar ratio is 80 / 20 or more and 98.9 / 1.1 or less, an even more preferable molar ratio is 90 / 10 or more and 99.7 / 0.3 or less, and an especially more preferable molar ratio is 97 / 3 or more and 99 / 1 or less. If the amount of TFE units is too small, the mechanical properties tend to deteriorate, and if it is too large, the melting point becomes too high and the moldability tends to deteriorate. It is also preferable that the above PFA is a copolymer in which the monomer units derived from monomers copolymerizable with TFE and PAVE are 0.1 to 10 mol%, and the total of TFE units and PAVE units is 90 to 99.9 mol%. Examples of monomers copolymerizable with TFE and PAVE include HFP, CZ 3 Z 4 =CZ 5 (CF2) n Z 6 (wherein Z 3 Z 4 and Z 5 represent the same or different hydrogen atoms or fluorine atoms, Z 6 represents a hydrogen atom, a fluorine atom, or a chlorine atom, and n represents an integer of 2 to 10.) vinyl monomers represented by, and CF2=CF-OCH2-Rf 7 (wherein Rf 7represents a perfluoroalkyl group having 1 to 5 carbon atoms. Examples thereof include alkyl perfluorovinyl ether derivatives represented by ().

[0151] The above-mentioned PFA preferably has a melting point of 180 °C or higher, more preferably 230 °C or higher, still more preferably 280 °C or higher, even more preferably 290 °C or higher, particularly preferably 295 °C or higher, and preferably less than 324 °C, more preferably 320 °C or lower, and still more preferably 310 °C or lower.

[0152] Although not particularly limited as FEP, a copolymer having a molar ratio of TFE units to HFP units (TFE units / HFP units) of 70 / 30 or more and less than 99 / 1 is preferred. A more preferred molar ratio is 70 / 30 or more and 98.9 / 1.1 or less, and a still more preferred molar ratio is 80 / 20 or more and 98.9 / 1.1 or less. Also, although not particularly limited as FEP, a copolymer having a mass ratio of TFE units to HFP units (TFE units / HFP units) of 60 / 40 or more and 98 / 2 or less is preferred. A more preferred mass ratio is 60 / 40 or more and 95 / 5 or less, and a still more preferred mass ratio is 85 / 15 or more and 92 / 8 or less. Further, as the above-mentioned FEP, perfluoro(alkyl vinyl ether) etc. may be used as a monomer copolymerizable with TFE and HFP, and it may be modified within the range of 0.1 to 2% by mass of all monomers. If the amount of TFE units is too small, the mechanical properties tend to decrease, and if it is too large, the melting point becomes too high and the moldability tends to decrease. The above-mentioned FEP is preferably a copolymer in which the monomer units derived from the monomers copolymerizable with TFE and HFP are 0.1 to 10 mol%, and the total of TFE units and HFP units is 90 to 99.9 mol%. Examples of the monomers copolymerizable with TFE and HFP include PAVE and alkyl perfluorovinyl ether derivatives.

[0153] The above-mentioned FEP has a melting point lower than that of the above-mentioned PTFE, preferably 150°C or higher, more preferably 200°C or higher, even more preferably 240°C or higher, even more preferably 250°C or higher, and preferably less than 324°C, more preferably 320°C or lower, even more preferably 300°C or lower, even more preferably 280°C or lower, and particularly preferably 275°C or lower.

[0154] As for ETFE, a copolymer in which the molar ratio of TFE units to ethylene units (TFE units / ethylene units) is 20 / 80 or more and 90 / 10 or less is preferable. A more preferable molar ratio is 37 / 63 or more and 85 / 15 or less, and an even more preferable molar ratio is 38 / 62 or more and 80 / 20 or less. The molar ratio of TFE units to ethylene units (TFE units / ethylene units) may be 50 / 50 or more and 99 / 1 or less. ETFE may be a copolymer composed of TFE, ethylene, and a monomer copolymerizable with TFE and ethylene. Examples of the copolymerizable monomer include the following formula CH2=CX 5 Rf 3 , CF2=CFRf 3 , CF2=CFORf 3 , CH2=C(Rf 3 )2 (In the formula, X 5 is a hydrogen atom or a fluorine atom, and Rf 3 represents a fluoroalkyl group which may contain an ether bond.) Monomers represented by are exemplified. Among them, CF2=CFRf 3 , CF2=CFORf 3 and CH2=CX 5 Rf 3 Fluorine-containing vinyl monomers represented by are preferable, and HFP, CF2=CF-ORf 4 (In the formula, Rf 4 represents a perfluoroalkyl group having 1 to 5 carbon atoms.) Perfluoro(alkyl vinyl ether) represented by and CH2=CX 3 where Rf 5 is a fluoroalkyl group having 1 to 8 carbon atoms 3The fluorine-containing vinyl monomer represented by is more preferable. Further, as the monomer copolymerizable with TFE and ethylene, an aliphatic unsaturated carboxylic acid such as itaconic acid or itaconic anhydride may be used. As the monomer copolymerizable with TFE and ethylene, perfluorobutylethylene, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene, 2,3,3,4,4,5,5-heptafluoro-1-pentene (CH2=CFCF2CF2CF2H), 2-trifluoromethyl-3,3,3-trifluoropropene ((CF3)2C=CH2) may be used. The monomer copolymerizable with TFE and ethylene is preferably 0.1 to 10 mol%, more preferably 0.1 to 5 mol%, and particularly preferably 0.2 to 4 mol% based on all polymerization units. Further, as the above ETFE, a monomer copolymerizable with TFE and ethylene may be further used and modified within the range of 0 to 20% by mass of all monomers. Preferably, TFE:ethylene:monomer copolymerizable with TFE and ethylene = (63 to 94):(27 to 2):(1 to 10).

[0155] The above ETFE may be a copolymer (EFEP) containing TFE units, ethylene units and HFP units. As the above EFEP, the molar ratio of TFE units to ethylene units is preferably 20:80 to 90:10, more preferably 37:63 to 85:15, and even more preferably 38:62 to 80:20. The HFP units are preferably 0.1 to 30 mol%, more preferably 0.1 to 20 mol% based on all polymerization units. The above ETFE preferably consists of 20 to 80 mol% of tetrafluoroethylene units, 10 to 80 mol% of ethylene units, 0 to 30 mol% of hexafluoropropylene units, and 0 to 10 mol% of other monomer units.

[0156] The above ETFE preferably has a melting point of 140°C or higher, more preferably 160°C or higher, still more preferably 195°C or higher, even more preferably 210°C or higher, particularly preferably 215°C or higher, and preferably less than 324°C, more preferably 320°C or lower, still more preferably 300°C or lower, even more preferably 280°C or lower, particularly preferably 270°C or lower. The above EFEP preferably has a melting point of 160°C or higher and preferably 200°C or lower.

[0157] In the above THV, the copolymerization ratio (molar% ratio) of TFE, HFP, and VdF is preferably TFE / HFP / VdF = 75 to 95 / 0.1 to 10 / 0.1 to 19, more preferably 77 to 95 / 1 to 8 / 1 to 17 (molar ratio), still more preferably 77 to 95 / 2 to 8 / 2 to 16.5 (molar ratio), and most preferably 77 to 90 / 3 to 8 / 5 to 16 (molar ratio). Further, the TFE / HFP / VdF copolymer may contain 0 to 20 mol% of other monomers. Examples of other monomers include fluorine-containing monomers such as perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), perfluoro(propyl vinyl ether), chlorotrifluoroethylene, 2-chloropentafluoropropene, and perfluorinated vinyl ethers (such as perfluoroalkoxy vinyl ethers like CF3OCF2CF2CF2OCF=CF2), perfluoroalkyl vinyl ethers, perfluoro-1,3-butadiene, trifluoroethylene, hexafluoroisobutene, vinyl fluoride, ethylene, propylene, and alkyl vinyl ethers, BTFB (H2C=CH-CF2-CF2-Br), BDFE (F2C=CHBr), and BTFE (F2C-CFBr). At least one monomer selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), perfluoro(propyl vinyl ether), BTFB (H2C=CH-CF2-CF2-Br), BDFE (F2C=CHBr), and BTFE (F2C-CFBr) is preferred.

[0158] The above-mentioned THV preferably has a melting point of 110°C or higher, more preferably 140°C or higher, still more preferably 160°C or higher, even more preferably 180°C or higher, particularly preferably 220°C or higher, and preferably 300°C or lower, more preferably 270°C or lower, still more preferably 250°C or lower, even more preferably 200°C or lower, particularly preferably 180°C or lower, even more preferably 160°C or lower, and most preferably 130°C or lower.

[0159] VT preferably contains 80.0 to 90.0 mol% of a polymerization unit based on VdF (also referred to as a "VdF unit") with respect to all polymerization units. When the VdF unit is less than 80.0 mol%, the change in viscosity of the electrode binder over time increases, and when it is more than 90.0 mol%, the flexibility of the electrode obtained from the binder tends to be inferior. The above-mentioned fluoropolymer preferably contains 80.5 mol% or more of the VdF unit with respect to all polymerization units, and more preferably 82.0 mol% or more. When it contains 82.0 mol% or more, the cycle characteristics of a battery using an electrode obtained from the electrode binder of the present disclosure tend to be better. Also, the above-mentioned VT more preferably contains 89.0 mol% or less of the VdF unit with respect to all polymerization units, still more preferably 88.9 mol% or less, and particularly preferably 88.8 mol% or less.

[0160] The above-mentioned VT may contain, in addition to the polymerization unit based on VdF and TFE (also referred to as a "TFE unit"), a polymerization unit based on a monomer copolymerizable with VdF and TFE. To achieve the effects of the present disclosure, a copolymer of VdF and TFE is sufficient, but a monomer copolymerizable with them can be copolymerized to further improve the adhesiveness to such an extent that the excellent non-aqueous electrolyte swelling property of the copolymer is not impaired. The content of the polymerized unit based on the monomer copolymerizable with the above VdF and TFE is preferably less than 3.0 mol% with respect to all the polymerized units of the above VT. When it is 3.0 mol% or more, generally the crystallinity of the copolymer of VdF and TFE significantly decreases, and as a result, the non-aqueous electrolyte swelling property tends to decrease.

[0161] Examples of the monomer copolymerizable with the above VdF and TFE include unsaturated dibasic acid monoesters such as those described in JP-A-6-172452, for example, maleic acid monomethyl ester, citraconic acid monomethyl ester, citraconic acid monoethyl ester, and vinylene carbonate, and those described in JP-A-7-201316, such as -SO3M, -OSO3M, -COOM, -OPO3M (where M represents an alkali metal), and -NHR which is an amine-based polar group. 1 、-NR 2 R 3 (R 1 、R 2 、R 3 represents an alkyl group), and compounds having a hydrophilic polar group such as CH2=CH-CH2-Y, CH2=C(CH3)-CH2-Y, CH2=CH-CH2-O-CO-CH(CH2COOR 4 )-Y, CH2=CH-CH2-O-CH2-CH(OH)-CH2-Y, CH2=C(CH3)-CO-O-CH2-CH2-CH2-Y, CH2=CH-CO-O-CH2-CH2-Y, CH2=CHCO-NH-C(CH3)2-CH2-Y (where Y is a hydrophilic polar group and R 4 represents an alkyl group), and others, such as maleic acid and maleic anhydride. Further, CH2=CH-CH2-O-(CH2) n -OH (3≦n≦8),

[0162]

Chemical formula

[0163] CH2=CH-CH2-O-(CH2-CH2-O) n -H (1≦n≦14), CH2=CH-CH2-O-(CH2-CH(CH3)-O)n allyl ether monomers such as -H (1 ≦ n ≦ 14), and carboxylated and / or -(CF2) n allyl ethers and ester monomers substituted with -CF3 (3 ≦ n ≦ 8), for example CH2=CH-CH2-O-CO-C2H4-COOH, CH2=CH-CH2-O-CO-C5H 10 -COOH, CH2=CH-CH2-O-C2H4-(CF2) n CF3, CH2=CH-CH2-CO-O-C2H4-(CF2) n CF3, CH2=C(CH3)-CO-O-CH2-CF3, etc. can also be used as copolymerizable monomers in the same way. By the way, it has been inferred from previous research that even compounds other than those containing polar groups as described above can slightly reduce the crystallinity of the copolymer of vinylidene fluoride and tetrafluoroethylene and impart flexibility to the material, thereby improving the adhesiveness to a current collector made of a metal foil such as aluminum or copper. From this, for example, unsaturated hydrocarbon monomers such as ethylene and propylene (CH2=CHR, where R is a hydrogen atom, an alkyl group, or a halogen such as Cl), and fluorine-based monomers such as vinylidene chloride trifluoride, hexafluoropropylene, hexafluoroisobutene, 2,3,3,3-tetrafluoropropene, CF2=CF-O-C n F 2n+1 (n is an integer of 1 or more), CH2=CF-C n F 2n+1 (n is an integer of 1 or more), CH2=CF-(CF2CF2) n H (n is an integer of 1 or more), and further CF2=CF-O-(CF2CF(CF3)O) m -C n F 2n+1 (m and n are integers of 1 or more) can also be used. In addition, formula (1):

[0164]

Chemical formula

[0165] (wherein Y is -CH2OH, -COOH, carboxylate, carboxyester group or epoxy group, X and X 1 are the same or different and each is a hydrogen atom or a fluorine atom, and R f represents a divalent fluorine-containing alkylene group having 1 to 40 carbon atoms or a divalent fluorine-containing alkylene group containing an ether bond and having 1 to 40 carbon atoms), and a fluorine-containing ethylenic monomer having at least one functional group represented by the formula can also be used. By copolymerizing one or more of these monomers, the adhesiveness to the current collector is further improved, and even when charge and discharge are repeated, the electrode active material does not peel off from the current collector, and good charge and discharge cycle characteristics can be obtained. Among these monomers, from the viewpoints of flexibility and chemical resistance, hexafluoropropylene and 2,3,3,3-tetrafluoropropene are particularly preferable.

[0166] As described above, the above-mentioned VT may contain other polymerization units in addition to the VdF unit and the TFE unit, but it is more preferably composed of only the VdF unit and the TFE unit.

[0167] The above-mentioned VT preferably has a weight average molecular weight (in terms of polystyrene) of 50,000 to 2,000,000. The above weight average molecular weight is more preferably 80,000 or more, still more preferably 100,000 or more, more preferably 1,950,000 or less, still more preferably 1,900,000 or less, particularly preferably 1,700,000 or less, and most preferably 1,500,000 or less. The above weight average molecular weight can be measured at 50 °C using N,N-dimethylformamide as a solvent by gel permeation chromatography (GPC).

[0168] The above-mentioned VT preferably has a number average molecular weight (in terms of polystyrene) of 10,000 to 1,400,000. The above number average molecular weight is more preferably 16,000 or more, still more preferably 20,000 or more, more preferably 1,300,000 or less, and still more preferably 1,200,000 or less. The number average molecular weight can be measured at 50 °C using N,N-dimethylformamide as a solvent by gel permeation chromatography (GPC).

[0169] The above-mentioned VT preferably has a melting point of 120 °C or higher, more preferably 130 °C or higher, and preferably 150 °C or lower, more preferably 140 °C or lower, and even more preferably 135 °C or lower.

[0170] The above-mentioned PVdF may be a homopolymer consisting only of polymerization units based on VdF, or may be composed of polymerization units based on VdF and polymerization units based on a monomer (α) copolymerizable with the above-mentioned polymerization units based on VdF.

[0171] Examples of the monomer (α) include vinyl fluoride, trifluoroethylene, trifluorochloroethylene, fluoroalkyl vinyl ether, hexafluoropropylene, 2,3,3,3-tetrafluoropropene, propylene, etc. Also, unsaturated dibasic acid monoesters as described in JP-A-6-172452, such as maleic acid monomethyl ester, citraconic acid monomethyl ester, citraconic acid monoethyl ester, and vinylene carbonate, and -SO3M, -OSO3M, -COOM, -OPO3M (M represents an alkali metal) and -NHR which is an amine-based polar group 1 、-NR 2 R 3 (R 1 、R 2 、R 3 represents an alkyl group), and compounds having hydrophilic polar groups such as CH2=CH-CH2-Y, CH2=C(CH3)-CH2-Y, CH2=CH-CH2-O-CO-CH(CH2COOR 4)-Y, CH2=CH-CH2-O-CH2-CH(OH)-CH2-Y, CH2=C(CH3)-CO-O-CH2-CH2-CH2-Y, CH2=CH-CO-O-CH2-CH2-Y, CH2=CHCO-NH-C(CH3)2-CH2-Y (Y is a hydrophilic polar group, and R 4 represents an alkyl group), and others, such as maleic acid and maleic anhydride. Furthermore, CH2=CH-CH2-O-(CH2) n -OH (3 ≤ n ≤ 8),

Chemical formula

[0172] [Chemical formula] (In the formula, Y is -CH2OH, -COOH, carboxylate, carboxyester group or epoxy group, X and X 1 are the same or different and each is a hydrogen atom or a fluorine atom, and R f represents a divalent fluorine-containing alkylene group having 1 to 40 carbon atoms or a divalent fluorine-containing alkylene group containing an ether bond having 1 to 40 carbon atoms). A fluorine-containing ethylenic monomer having at least one functional group represented by) can also be used. By copolymerizing one or more of these monomers, the adhesiveness to the current collector is further improved, and even when charge and discharge are repeated, the electrode active material does not peel off from the current collector, and good charge and discharge cycle characteristics can be obtained.

[0173] It is preferable that the above PVdF has a polymerization unit based on monomer (α) of 5 mol% or less of all polymerization units, and more preferably 4.5 mol% or less.

[0174] It is preferable that the above PVdF has a weight average molecular weight (in terms of polystyrene) of 50,000 to 2,000,000. The above weight average molecular weight is more preferably 80,000 or more, still more preferably 100,000 or more, more preferably 1,700,000 or less, and still more preferably 1,500,000 or less. The above weight average molecular weight can be measured at 50 °C using N,N-dimethylformamide as a solvent by gel permeation chromatography (GPC).

[0175] The above PVdF has a number average molecular weight (in terms of polystyrene) of 150,000 to 1,400,000. If it is less than 150,000, the adhesion of the obtained electrode will be low. If it exceeds 1,400,000, it will be prone to gelation when preparing the electrode paste. The above number average molecular weight is preferably 200,000 or more, more preferably 250,000 or more, still more preferably 300,000 or more, preferably 1,300,000 or less, more preferably 1,200,000 or less, still more preferably 1,000,000, and particularly preferably 800,000. The above number average molecular weight can be measured at 50 °C using N,N-dimethylformamide as a solvent by gel permeation chromatography (GPC).

[0176] The above PVdF preferably has a melting point of 130 °C or higher, more preferably 150 °C or higher, still more preferably 160 °C or higher, and preferably 230 °C or lower, more preferably 200 °C or lower, still more preferably 180 °C or lower.

[0177] The content of each monomer unit of the copolymer described above can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis according to the type of monomer.

[0178] Among the above fluoropolymers, at least one selected from the group consisting of THV, VT, PVdF, ETFE, FEP, and PFA is preferable, at least one selected from the group consisting of THV, VT, PVdF, and EFEP is more preferable, and at least one selected from the group consisting of THV and VT is still more preferable.

[0179] Examples of the elastomer having a glass transition temperature of 25°C or lower include non-fluorine elastomers such as nitrile rubber, hydrogenated nitrile rubber, styrene-butadiene rubber (SBR), chloroprene rubber (CR), butadiene rubber (BR), natural rubber (NR), isoprene rubber (IR), ethylene-α-olefin rubber, ethylene-α-olefin-non-conjugated diene rubber, chlorinated polyolefin rubber, chlorosulfonated polyolefin rubber, acrylic rubber, ethylene-based acrylic rubber, epichlorohydrin rubber, silicone rubber, butyl rubber (IIR), ethylene-vinyl ester rubber, ethylene-methacrylate rubber, etc.; and fluorine elastomers. Among them, fluorine elastomers are preferred. The elastomer having a glass transition temperature of 25°C or lower may be crosslinked or non-crosslinked.

[0180] Specific examples of the fluorine elastomer include, for example, vinylidene fluoride (VdF)-based fluorine elastomers, TFE / propylene (Pr)-based fluorine elastomers, TFE / Pr / VdF-based fluorine elastomers, ethylene (Et) / HFP-based fluorine elastomers, Et / HFP / VdF-based fluorine elastomers, Et / HFP / TFE-based fluorine-containing elastomers, fluorosilicone-based fluorine-containing elastomers, or fluorophosphazene-based fluorine-containing elastomers, etc. These can be used alone or in any combination within the range that does not impair the effects of the present disclosure. Among these, it is preferable to use VdF-based fluorine-containing elastomers.

[0181] The VdF-based fluorine-containing elastomer is a fluorine-containing elastomer containing VdF units and other monomer units copolymerizable with VdF. In the VdF-based fluorine-containing elastomer, the VdF units are preferably 20 mol% or more and 90 mol% or less, more preferably 40 mol% or more and 85 mol% or less, of the total number of moles of VdF units and other monomer units. A more preferable lower limit is 45 mol%, and a particularly preferable lower limit is 50 mol%. A more preferable upper limit is 80 mol%.

[0182] And the comonomer in the above VdF-based elastomer is not particularly limited as long as it can copolymerize with VdF. For example, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoroalkyl vinyl ether (PAVE), chlorotrifluoroethylene (CTFE), trifluoroethylene, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, vinyl fluoride, iodine-containing fluorinated vinyl ether, general formula (1-1) CH2=CFRf1(1-1) (In the formula, Rf1 is a linear or branched fluorinated alkyl group or fluorinated alkoxy group having 1 to 12 carbon atoms. When the carbon number is 2 or more, it may contain an oxygen atom between carbon-carbon atoms.) Fluorine-containing monomers represented by General formula (2-1) CHF=CHRf2(2-1) (In the formula, Rf2 is a linear or branched fluorinated alkyl group or fluorinated alkoxy group having 1 to 12 carbon atoms. When the carbon number is 2 or more, it may contain an oxygen atom between carbon-carbon atoms.) Fluorine-containing monomers such as fluorine-containing monomers represented by; fluorine-free monomers such as ethylene (Et), propylene (Pr), and alkyl vinyl ether, monomers that give a crosslinkable group (curing site), and reactive emulsifiers, etc. are mentioned, and one or two or more of these monomers and compounds can be used in combination.

[0183] As the compound represented by the above general formula (1-1), Rf1 is a linear or branched fluorinated alkyl group having 1 to 12 carbon atoms, or a linear or branched fluorinated alkoxy group having 1 to 12 carbon atoms. Both the fluorinated alkyl group and the fluorinated alkoxy group can contain an oxygen atom (-O-) between carbon-carbon atoms when the carbon number is 2 or more. The fluorinated alkyl group of Rf1 may be a partially fluorinated alkyl group in which some of the hydrogen atoms bonded to the carbon atoms are substituted by fluorine atoms, or a perfluorinated alkyl group in which all of the hydrogen atoms bonded to the carbon atoms are substituted by fluorine atoms. Further, the fluorinated alkyl group of Rf1 may have a hydrogen atom substituted by a substituent other than a fluorine atom, but preferably does not contain a substituent other than a fluorine atom. Also, the fluorinated alkoxy group of Rf1 may be a partially fluorinated alkoxy group in which some of the hydrogen atoms bonded to the carbon atoms are substituted by fluorine atoms, or a perfluorinated alkoxy group in which all of the hydrogen atoms bonded to the carbon atoms are substituted by fluorine atoms. Further, the fluorinated alkoxy group of Rf1 may have a hydrogen atom substituted by a substituent other than a fluorine atom, but preferably does not contain a substituent other than a fluorine atom. The number of carbon atoms of Rf1 is preferably 1 to 10, more preferably 1 to 6, still more preferably 1 to 4, and particularly preferably 1. As Rf1, the general formula: -(Rf 11 )m-(O)p-(Rf 12 -O)n-Rf 13 (In the formula, Rf 11 and Rf 12 are each independently a linear or branched fluorinated alkylene group having 1 to 4 carbon atoms, Rf 13 is a linear or branched fluorinated alkyl group having 1 to 4 carbon atoms, p is 0 or 1, m is an integer of 0 to 4, and n is an integer of 0 to 4) is preferably a group represented by.

[0184] Rf 11 and Rf 12 's fluorinated alkylene group may be a partially fluorinated alkylene group in which some of the hydrogen atoms bonded to the carbon atoms are substituted by fluorine atoms, or a perfluorinated alkylene group in which all of the hydrogen atoms bonded to the carbon atoms are substituted by fluorine atoms. Further, Rf 11 and Rf 12The fluorinated alkylene group may have a hydrogen atom substituted by a substituent other than a fluorine atom, but preferably does not contain a substituent other than a fluorine atom. Rf 11 and Rf 12 may be the same or different at each occurrence.

[0185] Rf 11 Examples of the fluorinated alkylene group of Rf include -CHF-, -CF2-, -CH2-CF2-, -CHF-CF2-, -CF2-CF2-, -CF(CF3)-, -CH2-CF2-CF2-, -CHF-CF2-CF2-, -CF2-CF2-CF2-, -CF(CF3)-CF2-, -CF2-CF(CF3)-, -C(CF3)2-, -CH2-CF2-CF2-CF2-, -CHF-CF2-CF2-CF2-, -CF2-CF2-CF2-CF2-, -CH(CF3)-CF2-CF2-, -CF(CF3)-CF2-CF2-, -C(CF3)2-CF2-, etc. Among them, a perfluorinated alkylene group having 1 or 2 carbon atoms is preferred, and -CF2- is more preferred.

[0186] Rf 12 Examples of the fluorinated alkylene group of Rf include -CHF-, -CF2-, -CH2-CF2-, -CHF-CF2-, -CF2-CF2-, -CF(CF3)-, -CH2-CF2-CF2-, -CHF-CF2-CF2-, -CF2-CF2-CF2-, -CF(CF3)-CF2-, -CF2-CF(CF3)-, -C(CF3)2-, -CH2-CF2-CF2-CF2-, -CHF-CF2-CF2-CF2-, -CF2-CF2-CF2-CF2-, -CH(CF3)-CF2-CF2-, -CF(CF3)-CF2-CF2-, -C(CF3)2-CF2-, etc. Among them, a perfluorinated alkylene group having 1 to 3 carbon atoms is preferred, and -CF2-, -CF2CF2-, -CF2-CF2-CF2-, -CF(CF3)-CF2- or -CF2-CF(CF3)- is more preferred.

[0187] Rf 13As the fluorinated alkyl group, it may be a partially fluorinated alkyl group in which some of the hydrogen atoms bonded to the carbon atom are substituted by fluorine atoms, or it may be a perfluorinated alkyl group in which all of the hydrogen atoms bonded to the carbon atom are substituted by fluorine atoms. Also, Rf 13 The fluorinated alkyl group of 13 may have a hydrogen atom substituted by a substituent other than a fluorine atom, but preferably does not contain a substituent other than a fluorine atom (for example, -CN, -CH2I, -CH2Br, etc.).

[0188] Rf 13 Examples of the fluorinated alkyl group of 13 include -CH2F, -CHF2, -CF3, -CH2-CH2F, -CH2-CHF2, -CH2-CF3, -CHF-CH2F, -CHF-CHF2, -CHF-CF3, -CF2-CH2F, -CF2-CHF2, -CF2-CF3, -CH2-CF2-CH2F, -CHF-CF2-CH2F, -CF2-CF2-CH2F, -CF(CF3)-CH2F, -CH2-CF2-CHF2, -CHF-CF2-CHF2, -CF2-CF2-CHF2, -CF(CF3)-CHF2, -CH2-CF2-CF3, -CHF-CF2-CF3, -CF2-CF2-CF3, -CF(CF3)-CF3, -CH2-CF2-CF2-CF3, -CHF-CF2-CF2-CF3, -CF2-CF2-CF2-CF3, -CH(CF3)-CF2-CF3, -CF(CF3)-CF2-CF3, -C(CF3)2-CF3, etc. Among them, -CF3, -CHF-CF3, -CF2-CHF2, -CF2-CF3, -CF2-CF2-CF3, -CF(CF3)-CF3, -CF2-CF2-CF2-CF3, -CH(CF3)-CF2-CF3 or -CF(CF3)-CF2-CF3 are preferred.

[0189] As p, 0 is preferred.

[0190] As m, it is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0. Also, when p is 0, m is preferably 0.

[0191] n is preferably an integer of 0 to 2, more preferably 0 or 1, and still more preferably 0.

[0192] As the repeating unit, -CH2-CF[-CF3]-, -CH2-CF[-CF2CF3]-, -CH2-CF[-CF2CF2CF3]-, -CH2-CF[-CF2CF2CF2CF3]-, -CH2-CF[-CF2-O-CF(CF3)-CF2-O-CHF-CF3]-, -CH2-CF[-CF2-O-CF(CF3)-CF2-O-CF2-CF3]-, -CH2-CF[-CF2-O-CF(CF3)-CF2-O-CF(CF3)-CF3]-, -CH2-CF[-CF2-O-CF(CF3)-CF2-O-CH(CF3)-CF2-CF3]-, -CH2-CF[-CF2-O-CF(CF3)-CF2-O-CF(CF3)-CF2-CF3]-, -CH2-CF[-OCF2OCF3]-, -CH2-CF[-OCF2CF2CF22OCF3]-, -CH2-CF[-CF2OCFOCF3]-, -CH2-CF[-CF2OCF2CF2CF2OCF3]-, or, -CH2-CF[-O-CF2-CF3]- is preferred, -CH2-CF[-CF3]- is more preferred.

[0193] As the compound represented by the above formula (2-1), Rf2 is a linear or branched fluorinated alkyl group having 1 to 12 carbon atoms, or a linear or branched fluorinated alkoxy group having 1 to 12 carbon atoms. When both the fluorinated alkyl group and the fluorinated alkoxy group have 2 or more carbon atoms, they can contain an oxygen atom (-O-) between carbon-carbon atoms. The fluorinated alkyl group of Rf2 may be a partially fluorinated alkyl group in which some of the hydrogen atoms bonded to the carbon atoms are substituted by fluorine atoms, or may be a perfluorinated alkyl group in which all of the hydrogen atoms bonded to the carbon atoms are substituted by fluorine atoms. Further, the fluorinated alkyl group of Rf2 may have a hydrogen atom substituted by a substituent other than a fluorine atom, but preferably does not contain a substituent other than a fluorine atom. Further, the fluorinated alkoxy group of Rf2 may be a partially fluorinated alkoxy group in which some of the hydrogen atoms bonded to the carbon atoms are substituted by fluorine atoms, or may be a perfluorinated alkoxy group in which all of the hydrogen atoms bonded to the carbon atoms are substituted by fluorine atoms. Further, the fluorinated alkoxy group of Rf2 may have a hydrogen atom substituted by a substituent other than a fluorine atom, but preferably does not contain a substituent other than a fluorine atom. The number of carbon atoms of Rf2 is preferably 1 to 10, more preferably 1 to 6, still more preferably 1 to 4, and particularly preferably 1.

[0194] As Rf2, the general formula: -(Rf 21 )m-(O)p-(Rf 22 -O)n-Rf 23 (In the formula, Rf 21 and Rf 22 are each independently a linear or branched fluorinated alkylene group having 1 to 4 carbon atoms, Rf 23 is a linear or branched fluorinated alkyl group having 1 to 4 carbon atoms, p is 0 or 1, m is an integer of 0 to 4, and n is an integer of 0 to 4.) is preferred.

[0195] Rf 21 and Rf 22 The fluorinated alkylene group of may be a partially fluorinated alkylene group in which some of the hydrogen atoms bonded to the carbon atoms are substituted by fluorine atoms, or may be a perfluorinated alkylene group in which all of the hydrogen atoms bonded to the carbon atoms are substituted by fluorine atoms. Further, Rf 21 and Rf 22The fluorinated alkylene group may have a hydrogen atom substituted by a substituent other than a fluorine atom, but preferably does not contain a substituent other than a fluorine atom. Rf 21 and Rf 22 may be the same or different in each occurrence.

[0196] Rf 21 Examples of the fluorinated alkylene group of Rf include -CHF-, -CF2-, -CH2-CF2-, -CHF-CF2-, -CF2-CF2-, -CF(CF3)-, -CH2-CF2-CF2-, -CHF-CF2-CF2-, -CF2-CF2-CF2-, -CF(CF3)-CF2-, -CF2-CF(CF3)-, -C(CF3)2-, -CH2-CF2-CF2-CF2-, -CHF-CF2-CF2-CF2-, -CF2-CF2-CF2-CF2-, -CH(CF3)-CF2-CF2-, -CF(CF3)-CF2-CF2-, -C(CF3)2-CF2-, etc. Among them, a perfluorinated alkylene group having 1 or 2 carbon atoms is preferred, and -CF2- is more preferred.

[0197] Rf 22 Examples of the fluorinated alkylene group of Rf include -CHF-, -CF2-, -CH2-CF2-, -CHF-CF2-, -CF2-CF2-, -CF(CF3)-, -CH2-CF2-CF2-, -CHF-CF2-CF2-, -CF2-CF2-CF2-, -CF(CF3)-CF2-, -CF2-CF(CF3)-, -C(CF3)2-, -CH2-CF2-CF2-CF2-, -CHF-CF2-CF2-CF2-, -CF2-CF2-CF2-CF2-, -CH(CF3)-CF2-CF2-, -CF(CF3)-CF2-CF2-, -C(CF3)2-CF2-, etc. Among them, a perfluorinated alkylene group having 1 to 3 carbon atoms is preferred, and -CF2-, -CF2CF2-, -CF2-CF2-CF2-, -CF(CF3)-CF2- or -CF2-CF(CF3)- is more preferred.

[0198] Rf 23The fluorinated alkyl group may be a partially fluorinated alkyl group in which some of the hydrogen atoms bonded to the carbon atom are substituted by fluorine atoms, or may be a perfluorinated alkyl group in which all of the hydrogen atoms bonded to the carbon atom are substituted by fluorine atoms. Also, Rf 23 The fluorinated alkyl group of 23 may have a hydrogen atom substituted by a substituent other than a fluorine atom, but preferably does not contain a substituent other than a fluorine atom (for example, -CN, -CH2I, -CH2Br, etc.).

[0199] Rf 23 Examples of the fluorinated alkyl group of 23 include -CH2F, -CHF2, -CF3, -CH2-CH2F, -CH2-CHF2, -CH2-CF3, -CHF-CH2F, -CHF-CHF2, -CHF-CF3, -CF2-CH2F, -CF2-CHF2, -CF2-CF3, -CH2-CF2-CH2F, -CHF-CF2-CH2F, -CF2-CF2-CH2F, -CF(CF3)-CH2F, -CH2-CF2-CHF2, -CHF-CF2-CHF2, -CF2-CF2-CHF2, -CF(CF3)-CHF2, -CH2-CF2-CF3, -CHF-CF2-CF3, -CF2-CF2-CF3, -CF(CF3)-CF3, -CH2-CF2-CF2-CF3, -CHF-CF2-CF2-CF3, -CF2-CF2-CF2-CF3, -CH(CF3)-CF2-CF3, -CF(CF3)-CF2-CF3, -C(CF3)2-CF3, etc. Among them, -CF3, -CHF-CF3, -CF2-CHF2, -CF2-CF3, -CF2-CF2-CF3, -CF(CF3)-CF3, -CF2-CF2-CF2-CF3, -CH(CF3)-CF2-CF3 or -CF(CF3)-CF2-CF3 are preferred.

[0200] Preferably, p is 0.

[0201] Preferably, m is an integer of 0 to 2, more preferably 0 or 1, and still more preferably 0. Also, when p is 0, it is preferable that m is also 0.

[0202] n is preferably an integer of 0 to 2, more preferably 0 or 1, and still more preferably 0.

[0203] As the repeating unit, -CHF-CH[-CF3]-, -CHF-CH[-CF2CF3]-, -CHF-CH[-CF2CF2CF3]-, or -CHF-CH[-CF2CF2CF2CF3]-, is preferable, -CHF-CH[-CF3]- is more preferable.

[0204] Among them, it is preferable that the copolymer unit is composed of hexafluoropropylene (HFP), tetrafluoroethylene (TFE), 2,3,3,3-tetrafluoropropylene, 1,3,3,3-tetrafluoropropylene, and perfluoroalkyl vinyl ether (PAVE). Further, it is most preferable that at least a part of the copolymer unit is hexafluoropropylene (HFP). Examples of the vinylidene fluoride-based elastomer in which at least a part of the copolymer unit is hexafluoropropylene (HFP) include a binary elastomer composed of vinylidene fluoride and hexafluoropropylene, and a ternary elastomer composed of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene.

[0205] As the above PAVE, perfluoro(methyl vinyl ether) (PMVE) and perfluoro(propyl vinyl ether) (PPVE) are more preferable, and particularly PMVE is preferable. Further, as the above PAVE, the formula: CF2=CFOCF2ORf c (wherein, Rf cA perfluorovinyl ether represented by (wherein Rf is a linear or branched perfluoroalkyl group having 1 to 6 carbon atoms, a cyclic perfluoroalkyl group having 5 to 6 carbon atoms, or a linear or branched perfluorooxyalkyl group having 2 to 6 carbon atoms containing 1 to 3 oxygen atoms) can also be used. For example, it is preferable to use CF2=CFOCF2OCF3, CF2=CFOCF2OCF2CF3, or CF2=CFOCF2OCF2CF2OCF3.

[0206] As the above-mentioned VdF-based fluorine-containing elastomer, at least one copolymer selected from the group consisting of a VdF / HFP copolymer, a VdF / TFE / HFP copolymer, a VdF / CTFE copolymer, a VdF / CTFE / TFE copolymer, a VdF / PAVE copolymer, a VdF / TFE / PAVE copolymer, a VdF / HFP / PAVE copolymer, a VdF / HFP / TFE / PAVE copolymer, a VdF / TFE / Pr copolymer, a VdF / Et / HFP copolymer, and a copolymer of VdF and a fluorine-containing monomer represented by the formula (1-1) or (2-1) is preferable. Further, as other comonomers other than VdF, it is more preferable to have at least one comonomer selected from the group consisting of TFE, HFP, and PAVE.

[0207] Among these, at least one copolymer selected from the group consisting of a VdF / HFP copolymer, a VdF / TFE / HFP copolymer, a copolymer of VdF and a fluorine-containing monomer represented by the formula (1-1) or (2-1), a VdF / PAVE copolymer, a VdF / TFE / PAVE copolymer, a VdF / HFP / PAVE copolymer, and a VdF / HFP / TFE / PAVE copolymer is preferable, at least one copolymer selected from the group consisting of a VdF / HFP copolymer, a VdF / TFE / HFP copolymer, a copolymer of VdF and a fluorine-containing monomer represented by the formula (1-1) or (2-1), and a VdF / PAVE copolymer is more preferable, and at least one copolymer selected from the group consisting of a VdF / HFP copolymer, a VdF / TFE / HFP copolymer, and a VdF / PAVE copolymer is particularly preferable.

[0208] The VdF / HFP copolymer preferably has a VdF / HFP composition of (45 to 85) / (55 to 15) (mol %), more preferably (50 to 80) / (50 to 20) (mol %), and still more preferably (60 to 80) / (40 to 20) (mol %). A VdF / HFP composition of (50 to 78) / (50 to 22) (mol %) is also preferred.

[0209] The VdF / TFE / HFP copolymer preferably has a VdF / TFE / HFP composition of (30 to 80) / (4 to 35) / (10 to 35) (mol %).

[0210] As the VdF / PAVE copolymer, a VdF / PAVE composition of (65 to 90) / (35 to 10) (mol %) is preferred. Also, a VdF / PAVE composition of (50 to 78) / (50 to 22) (mol %) is also a preferred form.

[0211] As the VdF / TFE / PAVE copolymer, a VdF / TFE / PAVE composition of (40 to 80) / (3 to 40) / (15 to 35) (mol %) is preferred.

[0212] As the VdF / HFP / PAVE copolymer, a VdF / HFP / PAVE composition of (65 to 90) / (3 to 25) / (3 to 25) (mol %) is preferred.

[0213] As the VdF / HFP / TFE / PAVE copolymer, a VdF / HFP / TFE / PAVE composition of (40 to 90) / (0 to 25) / (0 to 40) / (3 to 35) (mol %) is preferred, and a composition of (40 to 80) / (3 to 25) / (3 to 40) / (3 to 25) (mol %) is more preferred.

[0214] As the VdF / fluorine-containing monomer (1-1) or (2-1) copolymer represented by formula (1-1) or (2-1), those in which the VdF / fluorine-containing monomer (1-1) or (2-1) units are 87 / 13 to 20 / 80 (mol%), and the other monomer units other than VdF and the fluorine-containing monomer (1-1) or (2-1) are 0 to 50 mol% of all monomer units are preferred, and it is more preferred that the molar ratio of the VdF / fluorine-containing monomer (1-1) or (2-1) units is 80 / 20 to 20 / 80. Also, a composition in which the VdF / fluorine-containing monomer (1-1) or (2-1) units are 78 / 22 to 50 / 50 (mol%) is also one of the preferred forms. Further, those in which the VdF / fluorine-containing monomer (1-1) or (2-1) units are 87 / 13 to 50 / 50 (mol%), and the other monomer units other than VdF and the fluorine-containing monomer (1-1) or (2-1) are 1 to 50 mol% of all monomer units are also preferred. As the other monomers other than VdF and the fluorine-containing monomer (1-1) or (2-1), the monomers exemplified as the comonomers of VdF such as TFE, HFP, PMVE, perfluoroethyl vinyl ether (PEVE), PPVE, CTFE, trifluoroethylene, hexafluoroisobutene, vinyl fluoride, Et, Pr, alkyl vinyl ether, monomers giving crosslinkable groups, and reactive emulsifiers are preferred, and among them, PMVE, CTFE, HFP, and TFE are more preferred.

[0215] The TFE / Pr fluorine-containing elastomer refers to a fluorine-containing copolymer composed of 45 to 70 mol% of TFE and 55 to 30 mol% of Pr. In addition to these two components, it may contain 0 to 40 mol% of a specific third component (for example, PAVE).

[0216] As the Et / HFP copolymer, it is preferable that the composition of Et / HFP is (35 to 80) / (65 to 20) (mol%), and more preferably (40 to 75) / (60 to 25) (mol%).

[0217] The Et / HFP / TFE copolymer preferably has a composition of Et / HFP / TFE of (35 to 75) / (25 to 50) / (0 to 15) (mol %), more preferably (45 to 75) / (25 to 45) / (0 to 10) (mol %).

[0218] Examples of the perfluoro fluorinated elastomer include those composed of TFE / PAVE. The composition of TFE / PAVE is preferably (50 to 90) / (50 to 10) (mol %), more preferably (50 to 80) / (50 to 20) (mol %), and even more preferably (55 to 75) / (45 to 25) (mol %). Examples of PAVE in this case include PMVE, PPVE, etc., and these can be used alone or in any combination.

[0219] The fluororubber preferably has a fluorine content of 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more. The upper limit of the fluorine content is not particularly limited, but is preferably 71% by mass or less. The fluorine content is 19 a value obtained by calculation from the composition of the fluororubber measured by F-NMR. The molecular weight was calculated from the composition ratio, the mass of fluorine atoms contained therein was determined, and the fluorine content was calculated.

[0220] In the present disclosure, the composition ratio of each repeating unit of the fluororubber is a value measured by the NMR method. Specifically, it is a value measured by the following solution NMR method. Measuring device: VNMRS400 manufactured by Varian Resonance frequency: 376.04 (Sfrq) Pulse width: 30° (pw = 6.8)

[0221] The non-perfluoro fluorine-containing elastomer and the perfluoro fluorine-containing elastomer described above can be produced by conventional methods such as emulsion polymerization, suspension polymerization, solution polymerization, etc. In particular, according to the polymerization method using an iodine (bromine) compound known as iodine (bromine) transfer polymerization, a fluoroelastomer with a narrow molecular weight distribution can be produced.

[0222] The above polymer may have a structural unit other than the vinylidene fluoride unit and the copolymer unit (A). In this case, the content of the other structural unit is preferably 50 mol% or less. Note that it may consist only of the vinylidene fluoride unit and the copolymer unit (A). The content of the other structural unit is more preferably 30 mol% or less, and still more preferably 15 mol% or less.

[0223] The above polymer may use a monomer that provides a crosslinking site as the above other monomer.

[0224] The monomer that provides the above crosslinking site is not particularly limited. For example, the general formula: CX 1 2=CX 1 -Rf 1 CHR 1 X 2 (In the formula, X 1 is a hydrogen atom, a fluorine atom or -CH3, Rf 1 is a fluoroalkylene group, a perfluoroalkylene group, a fluoro(poly)oxyalkylene group or a perfluoro(poly)oxyalkylene group, R 1 is a hydrogen atom or -CH3, X 2 is an iodine atom or a bromine atom.) An iodine or bromine-containing monomer represented by the general formula: CF2=CFO(CF2CF(CF3)O)m(CF2)n-X 3 (In the formula, m is an integer from 0 to 5, n is an integer from 1 to 3, X 3 is a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, or a bromine atom.) A monomer represented by the general formula: CH2=CFCF2O(CF(CF3)CF2O)m(CF(CF3))n-X 4 (In the formula, m is an integer from 0 to 5, n is an integer from 1 to 3, and X 4 is a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or -CH2OH.) A monomer represented by the formula may be used as another monomer.

[0225] Among them, at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN, CF2=CFOCF2CF(CF3)OCF2CF2COOH, CF2=CFOCF2CF2CH2I, CF2=CFOCF2CF(CF3)OCF2CF2CH2I, CH2=CFCF2OCF(CF3)CF2OCF(CF3)CN, CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOH, and CH2=CFCF2OCF(CF3)CF2OCF(CF3)CH2OH is preferable. Further, it may contain a repeating unit based on a monomer that provides a crosslinking site, but in one embodiment of the present disclosure, it does not contain a crosslinking agent.

[0226] The above fluororubber has good adhesiveness and flexibility, and in order to have good solubility in a solvent, the number average molecular weight (Mn) is preferably 7000 to 5000000, the mass average molecular weight (Mw) is preferably 10000 to 10000000, Mw / Mn is preferably 1.0 to 30.0, and more preferably 1.5 to 25.0. The above number average molecular weight (Mn), mass average molecular weight (Mw), and Mw / Mn are values measured by the GPC method.

[0227] The Mooney viscosity (ML1+10(121°C)) of the above fluororubber is preferably 2 or more, more preferably 5 or more, still more preferably 10 or more, particularly preferably 30 or more, and may be 200 or less. The Mooney viscosity (ML1+10(140°C)) of the fluororubber is preferably 2 or more, more preferably 5 or more, still more preferably 10 or more, particularly preferably 30 or more, and may be 200 or less. The Mooney viscosity is a value measured in accordance with ASTM-D1646-15 and JIS K6300-1:2013.

[0228] The above fluororubber preferably has a terminal structure satisfying the following inequality: 0.01 ≦ ([-CH2OH] + [-COOH]) / ([-CH3] + [-CF2H] + [-CH2OH] + [-CH2I] + [-OC(O)RH] + [-COOH]) ≦ 0.25 (wherein, RH is an alkyl group having 1 to 20 carbon atoms). By making the terminal functional group satisfy the above formula, the adhesiveness and flexibility are good and it has excellent functions.

[0229] Note that satisfying the above general formula does not mean that the fluorine-containing copolymer has all the functional groups of [-CH3], [-CF2H], [-CH2OH], [-CH2I], [-OC(O)RH], and [-COOH]. Among these, for the terminal groups present in the fluorine-containing copolymer, it means that the molar ratio is within the above-mentioned range.

[0230] The amount of each terminal group of the fluorine-containing copolymer can be measured by NMR analysis.

[0231] For example, the terminal group analysis by NMR is performed by the proton solution NMR method. The analysis sample is adjusted to a 20 mass% solution using Acetone-d6 as a solvent and measured. The reference peak is set at 2.05 ppm at the peak top of acetone. Measuring device: VNMRS400 manufactured by Varian Resonance frequency: 399.74 (Sfrq) Pulse width: 45° Each end corresponds to those with the following peak positions. [-CH3]: 1.72 - 1.86 ppm [-CF2H]: 6.1 - 6.8 ppm [-CH2OH]: 3.74 - 3.80 ppm [-CH2I]: 3.87 - 3.92 ppm [-OC(O)RH]: 1.09 - 1.16 ppm [-COOH]: 10 - 15 ppm Based on the integral value of each peak specified by the above measurement, the functional group amount is calculated from each peak intensity and calculated by the following formula based on the result. ([-CH2OH] + [-COOH]) / ([-CH3] + [-CF2H] + [-CH2OH] + [-CH2I] + [-OC(O)RH] + [-COOH])

[0232] The method of making [-CH2OH] and [-COOH] within the above-mentioned predetermined ranges is not particularly limited and can be controlled by known methods (for example, selection and usage amount of initiator used in polymerization, etc.).

[0233] The fluoropolymer can be produced by a general radical polymerization method. The polymerization form may be any of bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization, but emulsion polymerization is preferred because it is easy to implement industrially. In the polymerization, a polymerization initiator, a chain transfer agent, a surfactant, and a solvent can be used, and each can be a conventionally known one. The above copolymer may be in any form such as an aqueous dispersion or powder. The copolymer powder can be obtained by coagulating the dispersion at the end of polymerization in the case of emulsion polymerization, followed by washing with water, dehydration, and drying. Coagulation can be carried out by adding an inorganic salt or inorganic acid such as aluminum sulfate, applying mechanical shear force, or freezing the dispersion. In the case of suspension polymerization, it can be obtained by recovering from the dispersion at the end of polymerization and drying. In the case of solution polymerization, it can be obtained by directly drying the solution containing the fluorine-containing polymer, or by adding a poor solvent dropwise for purification.

[0234] The binder powder for the electrochemical device of the present disclosure preferably has a water content of 1000 mass ppm or less. The water content is more preferably 500 mass ppm or less, still more preferably 200 mass ppm or less, even more preferably 100 mass ppm or less, particularly preferably 50 mass ppm or less, and most preferably 10 mass ppm or less. The above water content is measured by the following method. Measure the mass of the binder powder for the electrochemical device before and after heating at 150 °C for 2 hours, and calculate according to the following formula. Take three samples, calculate each one, then find the average and adopt the average value. Water content (mass ppm) = [(mass of the binder powder for the electrochemical device before heating (g)) - (mass of the binder powder for the electrochemical device after heating (g))] / (mass of the binder powder for the electrochemical device before heating (g)) × 1000000

[0235] The binder powder for the electrochemical device of the present disclosure preferably has an average primary particle size of 10 to 500 nm. The average primary particle size is preferably 350 nm or less, more preferably 330 nm or less, still more preferably 320 nm or less, even more preferably 300 nm or less, particularly preferably 280 nm or less, and especially preferably 250 nm or less. Also, it is preferably 100 nm or more, more preferably 150 nm or more, still more preferably 170 nm or more, and particularly preferably 200 nm or more. The above average primary particle size is measured by the dynamic light scattering method. Irradiate the binder powder for the electrochemical device with radiation of 100 to 300 kGy and make fine particles with a pulverizer. Add a nonionic surfactant to water to prevent the fine particles from aggregating, and perform ultrasonic treatment to obtain a dispersion. The average primary particle size is measured by creating an aqueous dispersion adjusted to a solid content concentration of about 1.0 mass%, using the dynamic light scattering method, at 25°C, with the refractive index of the solvent (water) being 1.3328 and the viscosity of the solvent (water) being 0.8878 mPa·s, and can be measured by integrating 70 times. As the dynamic light scattering method, for example, ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used.

[0236] The binder powder for the electrochemical device of the present disclosure preferably has a maximum particle size of less than 2000 μm. The maximum particle size is more preferably 1500 μm or less, still more preferably 1300 μm or less, and even more preferably 1000 μm or less. Also, the maximum particle size is preferably 300 μm or more. The above maximum particle size is measured by the following method. The particle size D90 corresponding to 90% by weight of the cumulative particle size distribution measured in accordance with JIS Z 8815 is taken as the maximum particle size.

[0237] The binder powder for an electrochemical device of the present disclosure preferably has a ratio of the number of fibrillatable resin particles having an aspect ratio of 30 or more to the total number of fibrillatable resin particles of 20% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 30 or more to the total number of fibrillatable resin particles is more preferably 15% or less, still more preferably 10% or less, even more preferably 5% or less, particularly preferably 3% or less, even more particularly preferably 2% or less, especially preferably 1% or less, and particularly especially preferably 0.5% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 30 or more to the total number of fibrillatable resin particles can be determined by the method described above.

[0238] The binder powder for an electrochemical device of the present disclosure preferably has a ratio of the number of fibrillatable resin particles having an aspect ratio of 20 or more to the total number of fibrillatable resin particles of 20% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 20 or more to the total number of fibrillatable resin particles is more preferably 15% or less, still more preferably 10% or less, even more preferably 5% or less, particularly preferably 3% or less, even more particularly preferably 2% or less, especially preferably 1% or less, and particularly especially preferably 0.5% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 20 or more to the total number of fibrillatable resin particles can be determined by the method described above.

[0239] The binder powder for an electrochemical device of the present disclosure preferably has a ratio of the number of fibrillatable resin particles having an aspect ratio of 10 or more to the total number of fibrillatable resin particles of 20% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 10 or more to the total number of fibrillatable resin particles is more preferably 15% or less, still more preferably 10% or less, even more preferably 5% or less, particularly preferably 3% or less, even more particularly preferably 2% or less, especially preferably 1% or less, and most preferably 0.5% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 10 or more to the total number of fibrillatable resin particles can be determined by the method described above.

[0240] The binder powder for an electrochemical device of the present disclosure more preferably has a ratio of the number of fibrillatable resin particles having an aspect ratio of 5 or more to the total number of fibrillatable resin particles of 20% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 5 or more to the total number of fibrillatable resin particles is more preferably 15% or less, still more preferably 10% or less, even more preferably 5% or less, particularly preferably 3% or less, even more particularly preferably 2% or less, especially preferably 1% or less, and most preferably 0.5% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 5 or more to the total number of fibrillatable resin particles can be determined by the method described above.

[0241] The binder powder for an electrochemical device of the present disclosure preferably has a non-fibrillated fibrillatable resin and a thermoplastic polymer mixed therewith, and more preferably they are uniformly mixed. Uniform mixing can be confirmed, for example, by the following average particle diameter.

[0242] The binder powder for the electrochemical device preferably has an average particle diameter of 1000 μm or less, more preferably 800 μm or less, and preferably 200 μm or more, more preferably 300 μm or more. The average particle diameter can be measured according to JIS Z8815.

[0243] The binder powder for the electrochemical device of the present disclosure can be produced, for example, by a production method including step (1) of producing a mixture containing the resin having the fibrillating property, the thermoplastic polymer, and water, and step (2) of producing a powder from the mixture.

[0244] Preferably, the above step (2) includes step (B) of removing a liquid medium such as water by drying the mixture obtained in the above step (1). Examples of the drying method include a shelf dryer, a vacuum dryer, a freeze dryer, a hot air dryer, a drum dryer, a spray dryer, etc. Particularly preferred is spray drying. Spray drying is a technique for producing a dried powder by spraying a mixture of a liquid and a solid into a gas and rapidly drying it. Thereby, a binder powder in a powder state in which a resin having fibrillating property and a thermoplastic polymer are uniformly mixed can be obtained. Spray drying is a generally well-known technique and can be performed by a general method using any known apparatus. The above step (B) can be performed by a general method using a known general apparatus. The drying temperature is preferably in the range of, for example, 100°C or higher and 250°C or lower. At 100°C or higher, the solvent can be sufficiently removed, and at 250°C or lower, the energy consumption can be further reduced, which is preferable. The drying temperature is more preferably 110°C or higher and more preferably 220°C or lower. Also, the supply liquid amount may be in the range of, for example, 0.1 L / h or more and 2 L / h or less, although it depends on the scale of production. Also, the nozzle size for spraying the prepared solution may be in the range of, for example, 0.5 mm or more and 5 mm or less in diameter, although it depends on the scale of production.

[0245] The present disclosure also relates to a method for producing a binder powder for an electrochemical device, including a step (1) of preparing a mixture containing a fibrillatable resin, a thermoplastic polymer, and water, and a step (2) of producing a powder from the above mixture. According to the method for producing a binder powder for an electrochemical device of the present disclosure, the binder powder for an electrochemical device of the present disclosure can be suitably produced.

[0246] As the fibrillatable resin and the thermoplastic polymer, those similar to those described for the binder powder for an electrochemical device of the present disclosure can be used.

[0247] In step (1), it is preferable that at least one of the fibrillatable resin and the thermoplastic polymer is mixed in the form of a dispersion, more preferably at least the thermoplastic polymer is mixed in the form of a dispersion, and even more preferably both the fibrillatable resin and the thermoplastic polymer are mixed in the form of a dispersion. The dispersion is preferably an aqueous dispersion. By mixing as described above, fibrillation of the fibrillatable resin can be suppressed, and a binder powder containing the unfibrillated fibrillatable resin can be easily obtained. Also, the fibrillatable resin and the thermoplastic polymer can be uniformly mixed. In step (1), a carbon-based conductive aid may be further added.

[0248] The dispersion may be an aqueous dispersion obtained by emulsion polymerization, or may be a powder obtained by emulsion polymerization or suspension polymerization dispersed in an aqueous medium. The dispersion of the fibrillatable resin is preferably an aqueous dispersion obtained by emulsion polymerization. The dispersion of the thermoplastic polymer preferably has an average primary particle size of 50 μm or less, more preferably 20 μm or less, even more preferably 10 μm or less, even more preferably 5 μm or less, and particularly preferably 1 μm or less, and preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.10 μm or more.

[0249] In the step (1), it is preferable to mix a dispersion containing the thermoplastic polymer having an average primary particle size of 50 μm or less with the fibrillating resin and water.

[0250] The step (2) preferably includes a step (2-1) of aggregating a composition containing the fibrillating resin and the thermoplastic polymer from the mixture to obtain an aggregate, and a step (2-2) of heat-treating the aggregate.

[0251] The coagulation in step (2-1) can be carried out by a known method. When coagulating a polymer in an aqueous dispersion, the aqueous dispersion obtained by polymerization of a polymer latex or the like is usually diluted with water, and in some cases, the pH is adjusted to neutral or alkaline, and then the mixture is stirred in a container equipped with a stirrer. The average particle size can be adjusted by adjusting the temperature and concentration during coagulation.

[0252] The heat treatment temperature in step (2-2) is preferably 10°C or higher, more preferably 50°C or higher, and even more preferably 100°C or higher, and is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower.

[0253] The heat treatment time in step (2-2) is preferably 10 minutes or more, more preferably 30 minutes or more, and even more preferably 60 minutes or more, and is preferably 100 hours or less, and more preferably 50 hours or less.

[0254] The binder powder for an electrochemical device of the present disclosure is preferably for a secondary battery.

[0255] The binder powder for an electrochemical device of the present disclosure may further contain a carbon-based conductive aid.

[0256] Examples of the carbon-based conductive aid include graphite (graphite) such as natural graphite and artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, needle coke, carbon nanotubes, fullerenes, and amorphous carbon such as VGCF.

[0257] The content of the carbon-based conductive aid is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 1% by mass or more, even more preferably 2% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less, based on the binder powder.

[0258] The present disclosure relates to a binder for an electrochemical device (hereinafter, also referred to as binder for an electrochemical device (1)) containing a resin having fibrillating properties and an ethylene / tetrafluoroethylene copolymer.

[0259] The present disclosure also relates to a binder for an electrochemical device (hereinafter, also referred to as binder for an electrochemical device (2)) containing a resin having fibrillating properties and an elastomer having a glass transition temperature of 25°C or lower.

[0260] The binders (1) and (2) for an electrochemical device are preferably powders.

[0261] As the resin having fibrillation properties, the ethylene / tetrafluoroethylene copolymer, and the elastomer having a glass transition temperature of 25°C or lower, those similar to those described for the binder powder for an electrochemical device of the present disclosure can be used.

[0262] The ethylene / tetrafluoroethylene copolymer is preferably an ethylene / tetrafluoroethylene / hexafluoropropylene copolymer (EFEP).

[0263] The elastomer is preferably a fluoroelastomer.

[0264] The fluoroelastomer preferably contains a VdF unit and other monomer units copolymerizable with VdF.

[0265] The binders (1) and (2) for an electrochemical device of the present disclosure preferably contain 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and preferably 99% by mass or less, more preferably 95% by mass or less, still more preferably 90% by mass or less of the resin having fibrillation properties with respect to the binder.

[0266] The binder (1) for an electrochemical device of the present disclosure preferably contains 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1.0% by mass or more, still more preferably 5.0% by mass or more, particularly preferably 10% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, still more preferably 25% by mass or less of the ethylene / tetrafluoroethylene copolymer with respect to the binder.

[0267] The binder (1) for the electrochemical device of the present disclosure preferably contains 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, and preferably 100% by mass or less, more preferably 75% by mass or less, still more preferably 50% by mass or less of the ethylene / tetrafluoroethylene copolymer with respect to the resin having fibrillation properties.

[0268] The binder (2) for the electrochemical device of the present disclosure preferably contains 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1.0% by mass or more, 5.0% by mass or more, 10% by mass or more with respect to the binder, and preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less of the elastomer having a glass transition temperature of 25°C or lower.

[0269] The binder (2) for the electrochemical device of the present disclosure preferably contains 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more with respect to the resin having fibrillation properties, and preferably 67% by mass or less, more preferably 43% by mass or less, still more preferably 33% by mass or less of the elastomer having a glass transition temperature of 25°C or lower.

[0270] The resin having fibrillation properties preferably has a glass transition temperature of 10 to 30°C.

[0271] The resin having fibrillation properties is preferably polytetrafluoroethylene.

[0272] The binders (1) and (2) for the electrochemical device preferably contain 50% by mass or more of the polytetrafluoroethylene.

[0273] The polytetrafluoroethylene preferably has a peak temperature of 333 to 347°C.

[0274] The above-mentioned binders (1) and (2) for the electrochemical device preferably have a water content of 1000 mass ppm or less. The water content is more preferably 500 mass ppm or less, still more preferably 200 mass ppm or less, even more preferably 100 mass ppm or less, particularly preferably 50 mass ppm or less, and most preferably 10 mass ppm or less. The above water content is measured by the following method. Measure the mass of the binder for the electrochemical device before and after heating at 150 °C for 2 hours, and calculate according to the following formula. Take the sample three times, calculate each time, then find the average, and adopt the average value. Water content (mass ppm) = [(mass of the binder for the electrochemical device before heating (g)) - (mass of the binder for the electrochemical device after heating (g))] / (mass of the binder for the electrochemical device before heating (g)) × 1000000

[0275] The above-mentioned binders (1) and (2) for the electrochemical device preferably have an average primary particle diameter of 10 to 500 nm. The average primary particle diameter is preferably 350 nm or less, more preferably 330 nm or less, still more preferably 320 nm or less, even more preferably 300 nm or less, particularly preferably 280 nm or less, and most preferably 250 nm or less. Also, it is preferably 100 nm or more, more preferably 150 nm or more, still more preferably 170 nm or more, and particularly preferably 200 nm or more. The above average primary particle diameter is measured by the dynamic light scattering method. The binder for the electrochemical device is irradiated with radiation of 100 to 300 kGy and made into fine particles with a pulverizer. Water and a nonionic surfactant are added to prevent the fine particles from aggregating, and ultrasonic treatment is performed to obtain a dispersion. The average primary particle diameter is measured by preparing an aqueous dispersion adjusted to a solid content concentration of about 1.0 mass%, using the dynamic light scattering method, at 25°C, with the refractive index of the solvent (water) being 1.3328 and the viscosity of the solvent (water) being 0.8878 mPa·s, and can be measured by integrating 70 times. As the dynamic light scattering method, for example, ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used.

[0276] The above-mentioned binders (1) and (2) for the electrochemical device preferably have a maximum particle diameter of less than 2000 μm. The maximum particle diameter is more preferably 1500 μm or less, still more preferably 1300 μm or less, and even more preferably 1000 μm or less. Also, the maximum particle diameter is preferably 300 μm or more. The particle diameter D90 corresponding to 90% by weight of the cumulative distribution of the particle size distribution measured in accordance with JIS Z 8815 is defined as the maximum particle diameter.

[0277] For the above-mentioned binders (1) and (2) for the electrochemical device, the ratio of the number of fibrillatable resin particles having an aspect ratio of 30 or more to the total number of fibrillatable resin particles is preferably 20% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 30 or more to the total number of fibrillatable resin particles is more preferably 15% or less, still more preferably 10% or less, even more preferably 5% or less, particularly preferably 3% or less, more particularly preferably 2% or less, especially preferably 1% or less, and particularly especially preferably 0.5% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 30 or more to the total number of fibrillatable resin particles can be determined by the method described above.

[0278] The above-mentioned binders (1) and (2) for the electrochemical device preferably have a ratio of the number of fibrillatable resin particles having an aspect ratio of 20 or more to the total number of fibrillatable resin particles of 20% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 20 or more to the total number of fibrillatable resin particles is more preferably 15% or less, still more preferably 10% or less, even more preferably 5% or less, particularly preferably 3% or less, even more particularly preferably 2% or less, especially preferably 1% or less, and particularly especially preferably 0.5% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 20 or more to the total number of fibrillatable resin particles can be determined by the method described above.

[0279] The above-mentioned binders (1) and (2) for the electrochemical device more preferably have a ratio of the number of fibrillatable resin particles having an aspect ratio of 10 or more to the total number of fibrillatable resin particles of 20% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 10 or more to the total number of fibrillatable resin particles is more preferably 15% or less, still more preferably 10% or less, even more preferably 5% or less, particularly preferably 3% or less, even more particularly preferably 2% or less, especially preferably 1% or less, and particularly especially preferably 0.5% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 10 or more to the total number of fibrillatable resin particles can be determined by the method described above.

[0280] The binders (1) and (2) for the above-mentioned electrochemical device are more preferably such that the ratio of the number of fibrillatable resin particles having an aspect ratio of 5 or more to the total number of fibrillatable resin particles is 20% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 5 or more to the total number of fibrillatable resin particles is more preferably 15% or less, still more preferably 10% or less, even more preferably 5% or less, particularly preferably 3% or less, even more particularly preferably 2% or less, especially preferably 1% or less, and most particularly preferably 0.5% or less. The ratio of the number of fibrillatable resin particles having an aspect ratio of 5 or more to the total number of fibrillatable resin particles can be determined by the method described above.

[0281] The binders (1) and (2) for the electrochemical device of the present disclosure are preferably a mixture of a non-fibrillated fibrillatable resin and a thermoplastic polymer, and more preferably a uniformly mixed one. Uniform mixing can also be confirmed, for example, by the following average particle diameter.

[0282] The binders (1) and (2) for the above-mentioned electrochemical device preferably have an average particle diameter of 1000 μm or less, more preferably 700 μm or less, and preferably 200 μm or more, more preferably 300 μm or more. The average particle diameter can be measured according to JIS Z8815.

[0283] The binders (1) and (2) for the above-mentioned electrochemical device are preferably for secondary batteries.

[0284] The binders (1) and (2) for the above-mentioned electrochemical device preferably further contain a carbon-based conductive assistant.

[0285] Examples of the carbon-based conductive aids include graphite (such as natural graphite and artificial graphite), carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, needle coke, carbon nanotubes, fullerenes, amorphous carbons such as VGCF, and the like.

[0286] The content of the carbon-based conductive aid is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 1% by mass or more, and even more preferably 2% by mass or more, based on the binder. Also, it is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less. The binders (1) and (2) for the electrochemical device of the present disclosure can be produced by known methods, not limited to the method for producing the binder powder for the electrochemical device of the present disclosure.

[0287] The present disclosure is also an electrode binder obtained by using the above-described binder powder for the electrochemical device of the present disclosure, or an electrode binder obtained by using the binder (1) or (2) for the electrochemical device. The electrode binder of the present disclosure may be a positive electrode binder or a negative electrode binder, but is preferably a positive electrode binder.

[0288] The above electrode binder usually contains an electrode active material. The above electrode binder may further contain a conductive aid.

[0289] As the constitution of the above electrode binder other than the binder, for example, those described in International Publication No. 2022 / 050251 can be adopted.

[0290] In the electrode binder of the present disclosure, the content of the binder may be 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.5% by mass or more, with respect to the above electrode binder. Also, it may be 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 10% by mass or less, particularly preferably 5% by mass or less, and most preferably 3% by mass or less. If the proportion of the binder is too low, the electrode binder active material cannot be sufficiently retained, resulting in insufficient mechanical strength of the electrode binder sheet and possibly deteriorating battery performance such as cycle characteristics. On the other hand, if it is too high, it may lead to a decrease in battery capacity and conductivity. Since the binder powder for electrochemical devices and the binders (1) and (2) for electrochemical devices of the present disclosure have excellent adhesive strength, even with a small content, the electrode active material can be sufficiently retained.

[0291] The electrode binder of the present disclosure is preferably in a sheet form.

[0292] The electrode binder of the present disclosure can be suitably used as an electrode binder for secondary batteries. In particular, the electrode binder of the present disclosure is suitable for lithium-ion secondary batteries. When the electrode binder of the present disclosure is used in a secondary battery, it is usually used in a sheet form.

[0293] The manufacturing method of the above electrode binder sheet is not limited, but specific examples of the manufacturing method are shown below.

[0294] Step (a): A step of mixing a powder component and a binder to form an electrode binder, Step (b): A step of calendaring or extrusion-molding the electrode binder to produce a sheet and The mixing in step (a) (a1) A step of homogenizing the powder component and the binder into a powder, (a2) A step of mixing the powdery raw material mixture obtained in step (a1) to prepare an electrode binder and is preferably a manufacturing method characterized by including.

[0295] For example, PTFE has two transition temperatures at about 19°C and about 30°C. Below 19°C, PTFE can be easily mixed while maintaining its shape. However, above 19°C, the structure of PTFE particles becomes loose and more sensitive to mechanical shear. At temperatures above 30°C, a higher degree of fibrillation occurs.

[0296] Therefore, the homogenization of (a1) is preferably carried out at a temperature of 19°C or lower, preferably 0°C to 19°C. That is, in such (a1), it is preferable to mix and homogenize while suppressing fibrillation. Next, the mixing in (a2), which is the subsequent step, is preferably carried out at a temperature of 30°C or higher to promote fibrillation.

[0297] The above step (a2) is preferably carried out at a temperature of 30°C to 150°C, more preferably 35°C to 120°C, and even more preferably 40°C to 80°C. In one embodiment, the calendaring or extrusion in the above step (b) is carried out at a temperature between 30°C and 150°C, preferably between 35°C and 120°C, and more preferably between 40°C and 100°C.

[0298] In the mixing of the above step (a), it is preferable to apply a shearing force. Specific mixing methods include methods of mixing using a W-type mixer, V-type mixer, drum-type mixer, ribbon mixer, conical screw-type mixer, single-screw kneader, twin-screw kneader, mix muller, stirring mixer, planetary mixer, Henschel mixer, high-speed mixer, etc.

[0299] The mixing conditions may be appropriately set for the rotation speed and the mixing time. For example, the rotation speed is preferably 15,000 rpm or less. Preferably it is 10 rpm or more, more preferably 1,000 rpm or more, still more preferably 3,000 rpm or more, and preferably 12,000 rpm or less, more preferably 11,000 rpm or less, still more preferably in the range of 10,000 rpm. If it is below the above range, it will take time for mixing and affect productivity. Also, if it exceeds the range, fibrillation may progress excessively, resulting in an electrode binder sheet with inferior strength. In step (a1), it is preferably carried out with a shearing force weaker than that in step (a2).

[0300] In the above step (a2), the raw material composition preferably does not contain a liquid solvent, but a small amount of lubricant may be used. That is, a lubricant may be added to the powdery raw material mixture obtained in the above step (a1) to prepare a paste.

[0301] The above lubricant is not particularly limited, and examples include water, ether compounds, alcohols, ionic liquids and carbonates, aliphatic hydrocarbons (low-polarity solvents such as heptane and xylene), isoparaffin-based hydrocarbon compounds and petroleum fractions (gasoline (C4-C10), naphtha (C4-C11), kerosene / paraffin (C10-C16), and mixtures thereof).

[0302] The above lubricant preferably has a water content of 1,000 ppm or less. A water content of 1,000 ppm or less is preferable in terms of reducing the deterioration of the electrochemical device. The above water content is more preferably 500 ppm or less.

[0303] When using the above lubricant, it is particularly preferable that it is a low-polarity solvent such as heptane or xylene, or an ionic liquid.

[0304] When using the above lubricant, the amount thereof may be 5.0 to 35.0 parts by weight, preferably 10.0 to 30.0 parts by weight, more preferably 15.0 to 25.0 parts by weight based on the total weight of the composition to be subjected to step (a1).

[0305] The above raw material composition preferably does not substantially contain a liquid medium. In the conventional method for forming an electrode binder, it was common to prepare a slurry in which a powder, which is an electrode binder component, was dispersed using a solvent in which a binder was dissolved, and to prepare an electrode binder sheet by applying and drying the slurry. In this case, a solvent for dissolving the binder is used. However, solvents that can dissolve the conventionally generally used binder resin are limited to specific solvents such as butyl butyrate. Since these react with the solid electrolyte and deteriorate the solid electrolyte, they may cause a decrease in battery performance. In addition, in low-polarity solvents such as heptane, the binder resin that can be dissolved is very limited, and the flash point is low, which may make handling complicated.

[0306] By using a powdery binder with little moisture without using a solvent during the formation of the electrode binder sheet, a battery with less deterioration of the solid electrolyte can be manufactured. Furthermore, in the manufacturing method as described above, an electrode binder sheet containing a binder having a fine fiber structure can be manufactured, and also, by not preparing a slurry, the burden on the manufacturing process can be reduced.

[0307] Step (b) is calendaring or extrusion. Calendaring and extrusion can be carried out by well-known methods. Thereby, it can be formed into the shape of an electrode binder sheet. Step (b) preferably includes (b1) a step of forming the electrode binder obtained in the above step (a) into a bulk shape, and (b2) a step of calendaring or extrusion-molding the bulk electrode binder.

[0308] Forming into a bulk shape means making the electrode binder into one mass. Specific methods for forming into a bulk shape include extrusion molding, press molding, and the like. Furthermore, the term "bulk" does not particularly specify a shape, but may refer to a state in which the material is in the form of a single mass, including rods, sheets, spheres, cubes, and the like. The size of the mass is preferably such that the diameter or the shortest side of the cross section is 10,000 μm or more, more preferably 20,000 μm or more.

[0309] Specific examples of the calendering or extrusion molding method in the step (b2) include a method in which the electrode mixture is rolled using a roll press, a calender roll, or the like.

[0310] The above step (b) is preferably carried out at 30 to 150° C. As mentioned above, PTFE has a glass transition temperature around 30° C., and therefore is easily fibrillated at temperatures above 30° C. Therefore, the step (b) is preferably carried out at such a temperature.

[0311] Then, calendering or extrusion applies shear force, which causes the PTFE to fibrillate and form.

[0312] It is also preferable to have a step (c) after step (b) in which a larger load is applied to the obtained rolled sheet to roll it into an even thinner sheet. It is also preferable to repeat step (c). In this way, by rolling the rolled sheet little by little in stages rather than thinning it all at once, flexibility is improved. The number of times step (c) is carried out is preferably 2 to 10 times, more preferably 3 to 9 times. A specific rolling method is, for example, a method in which two or more rolls are rotated and the rolled sheet is passed between them to process it into a thinner sheet.

[0313] Also, from the viewpoint of adjusting the sheet strength, after step (b) or step (c), it is also preferable to have a step (d) of crushing the rolled sheet and then reshaping it into a bulk form and rolling it into a sheet form again. It is also preferable to repeat step (d). The number of times of step (d) is preferably 1 or more and 12 or less, and more preferably 2 or more and 11 or less.

[0314] In step (d), specific methods for crushing the rolled sheet and shaping it into a bulk form include folding the rolled sheet, or shaping it into a rod or thin film sheet form, or chipping it. In the present disclosure, "crushing" means changing the form of the rolled sheet obtained in step (b) or step (c) to another form in order to roll it into a sheet form in the next step, and includes cases such as simply folding the rolled sheet.

[0315] Also, after step (d), step (c) may be performed, or may be repeated. Also, uniaxial stretching or biaxial stretching may be performed in steps (a) to (b), (c), and (d). Also, the sheet strength can be adjusted according to the degree of crushing in step (d).

[0316] In the above steps (b), (c), or (d), the rolling rate is preferably 10% or more, more preferably 20% or more, and also preferably 80% or less, more preferably 65% or less, and even more preferably 50% or less. If it is below the above range, it will take time as the number of rolling passes increases, which will affect productivity. Also, if it exceeds the range, fibrillation may progress excessively, resulting in an electrode binder sheet with poor strength and flexibility. Here, the rolling rate refers to the reduction rate of the thickness after processing with respect to the thickness of the sample before rolling. The sample before rolling may be a bulk raw material composition or a sheet raw material composition. The thickness of the sample refers to the thickness in the direction where the load is applied during rolling. The above steps (c) to (d) are preferably carried out at 30 °C or higher, more preferably 60 °C or higher. Also, it is preferably carried out at 150 °C or lower.

[0317] The above electrode binder sheet can be used as an electrode binder sheet for a secondary battery. It can be either the negative electrode or the positive electrode. In particular, the above electrode binder sheet is suitable for a lithium-ion secondary battery.

[0318] This disclosure is also an electrode obtained by using the binder powder for an electrochemical device of this disclosure described above, or an electrode obtained by using the binder (1) or (2) for an electrochemical device. The electrode of this disclosure usually includes an electrode active material and a current collector. The electrode of this disclosure is preferably for a secondary battery. The electrode of this disclosure may include the above electrode binder (preferably an electrode binder sheet) of this disclosure and a current collector. The electrode of this disclosure may be a positive electrode or a negative electrode, but is preferably a positive electrode.

[0319] As the configuration of the above electrode other than the binder, for example, those described in International Publication No. 2022 / 050251 can be adopted.

[0320] This disclosure also provides a secondary battery including the above electrode of this disclosure.

[0321] The secondary battery of this disclosure may be a secondary battery using an electrolytic solution or a solid secondary battery.

[0322] For the secondary battery using the above electrolytic solution, an electrolytic solution, a separator, etc. used in a known secondary battery can be used. As the configuration of the secondary battery using the above electrolytic solution other than the binder, for example, those described in International Publication No. 2022 / 050251 can be adopted.

[0323] The above-mentioned solid secondary battery is preferably an all-solid-state secondary battery. The above-mentioned solid secondary battery is preferably a lithium-ion battery, and also preferably a sulfide-based all-solid-state secondary battery. The above-mentioned solid secondary battery preferably includes a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode. As the configuration of the above-mentioned solid secondary battery other than the binder, for example, those described in International Publication No. 2022 / 050252 can be adopted.

Examples

[0324] Next, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to only these examples.

[0325] A composite binder material was manufactured according to the present disclosure. The following samples of the composite binder material were prepared and tested. Sample 1: PTFE containing integrated conductive carbon and various amounts of EFEP (5 mass%, 7.5 mass%, 10 mass%, and 20 mass%) Sample 2: High molecular weight PTFE containing integrated conductive carbon and various amounts of EFEP (5 mass%, 7.5 mass%, 10 mass%, and 20 mass%) Sample 3: Modified PTFE containing integrated conductive carbon and various amounts of EFEP (10 mass% and 20 mass%)

[0326] Preparation method

[0327] A composite binder material was prepared according to the following method. A PTFE emulsion was obtained by aqueous polymerization of tetrafluoroethylene in the presence of an emulsifier, paraffin wax, and an initiator. First, the wax was separated by decanting the emulsion from the light wax phase. After separation from the wax phase, mechanical stirring was started to initiate the aggregation process of the PTFE emulsion. The stirring speed was set at a speed that generated a vortex to draw the added materials into the PTFE emulsion while not applying excessive shear force to the emulsion. When vortices began to be observed, a conductive aid and a low melting point thermoplastic resin (EFEP) were added to the PTFE emulsion. When sufficient energy was applied to the suspension by mechanical stirring, secondary particles aggregated or PTFE separated from the aqueous phase. At completion, distinct secondary particles of PTFE containing the integrated conductive aid and EFEP were observed. The aggregated material was then decanted from the remaining liquid and dried at a high temperature.

[0328] Results

[0329] Imaging of the composite binder material

[0330] Figures 1A - 1E show images of PTFE particles integrated with conductive carbon and 5 wt% of EFEP. Figures 2A - 2E show images of PTFE particles integrated with conductive carbon and 7.5 wt% of EFEP. Figures 3A - 3E show images of PTFE particles integrated with conductive carbon and 10 wt% of EFEP. Figures 4A - 4E show images of PTFE particles integrated with conductive carbon and 20 wt% of EFEP. As seen in Figures 1A - 1E, 2A - 2E, 3A - 3E, and 4A - 4E, the appearance of the composite binder material is a fluffy gray to black powder. Since the conductive carbon is integrated within the PTFE, there is little or no adhesion of the conductive carbon to the container or hands during handling.

[0331] Adhesion test

[0332] Samples 1, 2, and 3 of the composite binder material were tested for adhesion strength by a composite binder peel test. The purpose of the peel test is to measure the force required to peel the metal strip from the composite binder. When referring to the adhesion peel test in this disclosure or the claims, it should be considered to refer to the adhesion peel test conducted as described herein. Aluminum was selected as the metal to function as the current collector of the cathode of the lithium-ion battery. The peel test was conducted in the following procedure. 1. Using a hand press, a "cathode grade" aluminum foil was cut into strips 2 cm × 25 cm in size. There were no creases or wrinkles in the cut strips. 2. The composite binder was uniformly dispersed on one strip. At this time, approximately 2 cm at the ends of the strip were left uncoated. A "drawdown blade" was used to place the composite binder on the strip. 3. The second strip was placed on the coated strip and slight pressure was applied. Both strips were placed in a heat press (with the cathode mixture sandwiched in between). 4. The cathode was allowed to cool to a temperature of 22 ± 3 °C over at least 1 hour. 5. Using a mechanical testing machine manufactured by Instron, the part of the strip that did not contain the cathode mixture was attached to a mechanical clamp. 6. The mechanical testing machine manufactured by Instron was set to pull at 10 inches / min (25 cm / min), and the load was measured with a pressure transducer. The measurement length was at least 2 inches (5 cm). The reported load is the average load over the measured distance.

[0333] Figure 5 shows the adhesion strength of PTFE particles integrated with conductive carbon and various amounts of EFEP (5 wt%, 7.5 wt%, 10 wt%, and 20 wt%). Figure 6 shows the adhesion strength of high molecular weight PTFE particles integrated with conductive carbon and various amounts of EFEP (5 wt%, 7.5 wt%, 10 wt%, and 20 wt%). Figure 7 shows the adhesion strength of modified PTFE particles integrated with conductive carbon and various amounts of EFEP (10 wt% and 20 wt%). Figure 8 shows the adhesion strength of PTFE particles without additives compared to PTFE particles integrated with conductive carbon and various amounts of EFEP (5 wt%, 7.5 wt%, 10 wt%, and 20 wt%).

[0334] As shown in Figures 5 - 8, the composite binder material manufactured according to the present disclosure had an adhesion strength with high purity aluminum > 1 Nmm, as measured in an adhesion test using a 25 mm wide film having high purity aluminum on both sides.

[0335] FTIR Chemical Functional Groups

[0336] The composite binder material was placed on an FTIR - ATR apparatus. Figure 9A shows the ATR - FTIR spectrum of PTFE particles integrated with conductive carbon. Figure 9B shows the ATR - FTIR spectrum of PTFE particles integrated with conductive carbon and EFEP. As demonstrated by Figures 9A and 9B, upon identification of the functional groups, it was suggested that both PTFE and EFEP were present in the composite binder material.

[0337] Thermogravimetric Analysis (TGA) Weight Loss Test

[0338] A TGA test was performed on Sample 1 (PTFE containing integrated conductive carbon and various amounts of EFEP (5 wt%, 7.5 wt%, 10 wt%, and 20 wt%)). Figures 10A - 10D show the weight loss (%) of each binder material with respect to the temperature increase.

[0339] The foregoing description illustrates and describes the processes, products, compositions, and other teachings of the present disclosure. Further, while the present disclosure presents and describes only particular embodiments of the disclosed processes, articles of manufacture, compositions of matter, and other teachings, as noted above, the teachings of the present disclosure are applicable in various other combinations, modifications, and environments, and can be varied or modified within the scope of the teachings presented herein, commensurate with the skills and / or knowledge of those of ordinary skill in the relevant art. The above-described embodiments further illustrate the best mode known to the applicant of carrying out the processes, articles of manufacture, compositions of matter, and other teachings of the present disclosure, and are intended to enable others of ordinary skill in the art to utilize the teachings of the present disclosure in such and other embodiments, with various modifications as may be required by the particular application or use. Accordingly, the processes, articles of manufacture, compositions of matter, and other teachings of the present disclosure are not intended to be limited to the exact embodiments and examples disclosed herein. The section headings described herein are provided only for consistency with the proposals of 37 C.F.R. § 1.77 or to otherwise indicate an organizational order. These headings do not limit or characterize the invention described herein.

[0340] Average primary particle size Measured by dynamic light scattering method. An aqueous dispersion of fluoropolymer adjusted to a fluoropolymer solid content concentration of about 1.0 mass% was prepared and measured at 25 °C for 70 integrations using an ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.). The refractive index of the solvent (water) was 1.3328, and the viscosity of the solvent (water) was 0.8878 mPa·s.

[0341] Solid content concentration (P) Approximately 1 g (X) of the sample was placed in an aluminum cup with a diameter of 5 cm, dried at 150 °C for 1 hour, and then determined by the formula: P = Z / X × 100 (%) based on the obtained heating residue (Z).

[0342] Fluoropolymer composition 1 1H-NMR analysis, 19It was measured by F-NMR analysis.

[0343] Standard specific gravity (SSG) Using a sample formed in accordance with ASTM D 4895, it was measured by the water displacement method in accordance with ASTM D 792.

[0344] Peak temperature of the resin having fibrillating property The peak temperature was defined as the temperature corresponding to the maximum value in the melting heat curve when the temperature of PTFE without a heating history at 300 °C or higher was raised at a rate of 10 °C / min using a differential scanning calorimeter [DSC].

[0345] Melting point of the thermoplastic polymer The melting point was defined as the temperature corresponding to the maximum value in the melting heat curve when the temperature was raised for the second time at a rate of 10 °C / min using a differential scanning calorimeter [DSC].

[0346] Measurement of glass transition point (Tg) Using a differential scanning calorimeter (manufactured by Seiko Instruments Inc.), after cooling to -50 °C, the temperature corresponding to the maximum value in the melting heat quantity curve when the temperature was raised to 50 °C at a rate of 10 °C / min was defined as the glass transition point.

[0347] MFR of the thermoplastic polymer The melt flow rate was measured in accordance with ASTM D1238 using a melt indexer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) to measure the weight (g) of the polymer flowing out per unit time (10 minutes) from a nozzle with an inner diameter of 2 mm and a length of 8 mm under various temperatures and various loads.

[0348] Mooney viscosity of the fluoroelastomer (ML1+10(121 °C, 140 °C) It was measured in accordance with ASTM D1646-15 and JIS K6300-1:2013. Measuring instrument: MV2000E type manufactured by ALPHA TECHNOLOGIES Rotator rotation speed: 2 rpm Measuring temperature: 121 °C, 140 °C Measurement time: After preheating for 1 minute, the rotor was immediately rotated, and the value after 10 minutes was measured.

[0349] Heat of fusion of fluoroelastomer Using a differential scanning calorimeter (manufactured by Hitachi High-Tech Science Corporation, X-DSC823e), a DSC curve was obtained by heating 10 mg of the sample at a rate of 20 °C / min, and the heat of fusion was calculated from the magnitude of the melting peak (ΔH) appearing in the DSC curve.

[0350] Glass transition temperature (Tg) of fluoroelastomer Using a differential scanning calorimeter (manufactured by Hitachi High-Tech Science Corporation, X-DSC823e), a DSC curve was obtained by heating 10 mg of the sample at a rate of 20 °C / min, and the temperature indicated by the intersection of the extension line of the baseline before and after the secondary transition of the DSC curve and the tangent line at the inflection point of the DSC curve was defined as the glass transition temperature.

[0351] Ratio of polar groups contained in fluoroelastomer Terminal group analysis by NMR was performed by the method described above, and the ratio of ([−CH2OH] + [−COOH]) / ([−CH3] + [−CF2H] + [−CH2OH] + [−CH2I] + [−OC(O)RH] + [−COOH]) was calculated.

[0352] Weight-average molecular weight of fluoroelastomer Measured by gel permeation chromatography (GPC). Calculated from the data measured using Tosoh Corporation's AS-8010, CO-8020, columns (three GMHHR-H columns connected in series) and Shimadzu Corporation's RID-10A, with dimethylformamide (DMF) as the solvent flowing at a flow rate of 1.0 ml / min (reference: polystyrene).

[0353] Moisture content The mass of the binder powder for electrochemical devices was measured before and after heating at 150 °C for 2 hours, and calculated according to the following formula. The sample was taken three times, calculated respectively, and the average was obtained and adopted as the average value. Water content (ppm by mass) = [(mass (g) of the binder powder for the electrochemical device before heating) - (mass (g) of the binder powder for the electrochemical device after heating)] / (mass (g) of the binder powder for the electrochemical device before heating) × 1000000

[0354] Average particle diameter The particle diameter D50 corresponding to 50% by weight of the cumulative distribution of the particle size distribution measured in accordance with JIS Z 8815 was defined as the average particle diameter.

[0355] Maximum particle diameter The particle diameter D90 corresponding to 90% by weight of the cumulative distribution of the particle size distribution measured in accordance with JIS Z 8815 was defined as the maximum particle diameter.

[0356] Average particle diameter of PVDF powder Using a laser diffraction particle size distribution analyzer (LS13 320) manufactured by Beckman Coulter, measurements were performed in a dry state at a vacuum pressure of 20 mH2O, and the average particle diameter was determined based on the obtained particle size distribution (volume basis). The average particle diameter was assumed to be equal to the particle diameter corresponding to 50% of the integrated particle size distribution.

[0357] Synthesis example White solid A was obtained by the method described in Synthesis Example 1 of International Publication No. 2021 / 045228.

[0358] Production Example 1 (PTFE-1 aqueous dispersion) A 6-liter reaction vessel equipped with a stirring blade and a temperature control jacket was charged with 3480 g of deionized water, 100 g of paraffin wax, and 5.25 g of white solid A as a fluorine-containing surfactant, and the inside of the reaction vessel was purged with nitrogen gas to remove oxygen while heating to 70°C. Tetrafluoroethylene (TFE) was pressured in to set the system internal pressure to 0.78 MPaG, and the temperature inside the vessel was maintained at 70°C while stirring. Next, an aqueous solution prepared by dissolving 15.0 mg of ammonium persulfate in 20 g of water was pressured in to initiate the polymerization reaction. As the polymerization reaction proceeded, the reaction pressure decreased, but TFE was added to maintain the temperature inside the vessel at 70°C and the reaction pressure at 0.78 MPaG. When 400 g of TFE was supplied from the start of polymerization, an aqueous solution prepared by dissolving 18.0 mg of hydroquinone in 20 g of water as a radical scavenger was injected under pressure. Polymerization continued thereafter. When the supply amount of TFE reached 1200 g from the start of polymerization, stirring and the supply of TFE were stopped, and immediately the gas in the reaction vessel was released to normal pressure to terminate the polymerization reaction. The obtained aqueous dispersion was taken out, cooled, and paraffin wax was separated to obtain an aqueous PTFE dispersion. The solid content concentration of the obtained aqueous PTFE dispersion was 25.3% by mass, and the average primary particle diameter was 310 nm. The peak temperature was 344 °C.

[0359] Production Example 2 (PTFE-1 powder) The aqueous PTFE dispersion obtained in Production Example 1 was diluted to a solid content concentration of 13% by mass, and PTFE was coagulated while stirring in a container, and then separated from water by filtration to obtain a wet PTFE powder. The obtained wet powder was placed on a stainless steel mesh tray, and the mesh tray was heat-treated in a hot air circulation type electric furnace at 130 °C. After 20 hours, the mesh tray was taken out, and after air-cooling the mesh tray, a PTFE powder was obtained. The SSG of the obtained PTFE powder was 2.159. The peak temperature of the obtained PTFE powder was 344 °C, and the glass transition point was 22 °C. The average particle diameter was 540 μm.

[0360] Production Example 3 (PTFE-2 aqueous dispersion) A reaction vessel with an internal volume of 6 liters equipped with a stirring blade and a temperature control jacket was charged with 3600 g of deionized water, 180 g of paraffin wax, 5.4 g of white solid A as a fluorine-containing surfactant, and 0.025 g of oxalic acid, and the inside of the reaction vessel was replaced with nitrogen gas to remove oxygen while heating to 70 °C. After maintaining the temperature in the tank at 70 °C while stirring, TFE gas was introduced to a pressure of 2.7 MPaG. While stirring the contents, deionized water in which 3.5 mg of potassium permanganate was dissolved was continuously added at a constant rate, and TFE was continuously supplied so that the pressure in the reaction vessel became constant at 2.7 MPaG. When the TFE consumption reached 184 g, 5.3 g of white solid A was added, and when the TFE consumption reached 900 g, the total amount of deionized water in which the above 3.5 mg of potassium permanganate was dissolved was added. When the TFE consumption reached 1540 g, stirring and TFE supply were stopped, the TFE in the reaction vessel was purged, and the polymerization reaction was terminated. An aqueous dispersion was taken out, cooled, and paraffin wax was separated to obtain a PTFE aqueous dispersion. The solid content concentration of the obtained PTFE aqueous dispersion was 29.7% by mass, and the average primary particle diameter was 296 nm.

[0361] The obtained PTFE aqueous dispersion was diluted to a solid content concentration of 13% by mass, and PTFE was coagulated while stirring in a container, then separated from water by filtration and dried to obtain PTFE powder. The SSG of the obtained PTFE powder was 2.152. The peak temperature of the obtained PTFE powder was 345 °C, and the glass transition point was 22 °C.

[0362] Production Example 4 (PVDF Aqueous Dispersion) A PVDF aqueous dispersion was obtained with reference to Example 1 of JP-A-2014-141673. That is, 1700 g of pure water, 0.85 g of H-(CF2CF2)3-CH2-O-CO-CH2CH(-SO3Na)-CO-O-CH2-(CF2CF2)3-H (surface tension 22 mN / m) as a surfactant, and 17 g of paraffin wax were placed in a 3.0 L stainless steel autoclave, and the inside was purged with nitrogen. 150 g of vinylidene fluoride (VdF) was added, and the temperature in the tank was raised to 115 °C. Under stirring, 0.51 g of acetone and 5.6 g of di-t-butyl peroxide were added to start the reaction. Vinylidene fluoride was additionally added over 9 hours in an amount of 427 g so that the pressure in the tank was maintained at 4.0 MPaG, and 1.45 g of H-(CF2CF2)3-CH2-O-CO-CH2CH(-SO3Na)-CO-O-CH2-(CF2CF2)3-H was additionally added during the process to obtain 2112.45 g of a stable PVDF aqueous dispersion (solid content concentration 20.6% by mass). The melting point of the obtained PVDF was 160.8 °C, and the average primary particle size was 171 nm.

[0363] Production Example 5 (PVDF powder) The PVDF aqueous dispersion obtained in Production Example 4 was coagulated, dried, and pulverized to obtain PVDF powder. The MFR of the obtained PVDF was 1.05 g / 10 min under the conditions of 230 °C and a load of 98 N (10 kg). The average particle size was 1.1 μm.

[0364] Production Example 6 (VdF / TFE copolymer (fluoropolymer A) powder) According to Adjustment Example 8 of International Publication No. 2013 / 176093, a white powder of fluoropolymer was obtained. The composition of the obtained fluoropolymer was VdF / TFE = 82.9 / 17.1 (mol%), and the melting point was 131 °C. The MFR of the obtained fluoropolymer was 1 g / 10 min under the conditions of 297 °C and a load of 212 N (21.6 kg), and the weight average molecular weight was 1,210,000. The average particle size was 400 μm.

[0365] Production Example 7 (Et / TFE / HFP copolymer (EFEP) powder) A fluoropolymer powder was obtained according to Synthesis Example 7 of JP-A-2006-306105. That is, 380 L of deionized water was charged into an autoclave, and after nitrogen substitution, 75 kg of 1-fluoro-1,1-dichloroethane, 155 kg of hexafluoropropylene, and 0.5 kg of perfluoro(1,1,5-trihydro-1-pentene) were charged, and the inside of the system was maintained at 35°C and a stirring speed of 200 rpm. Then, tetrafluoroethylene was pressured in up to 0.7 MPaG, and subsequently ethylene was pressured in up to 1.0 MPaG. Then, 2.4 kg of di-n-propyl peroxydicarbonate was charged to initiate polymerization. Since the pressure inside the system decreased as the polymerization progressed, a mixed gas of tetrafluoroethylene (TFE) / ethylene (Et) / hexafluoropropylene (HFP) = 40.5 / 44.5 / 15.0 mol% was continuously supplied to maintain the pressure inside the system at 1.0 MPaG. And regarding perfluoro(1,1,5-trihydro-1-pentene) (HF-Pa), a total amount of 1.5 kg was continuously charged, and stirring was continued for 20 hours. Then, after depressurizing and returning to atmospheric pressure, the reaction product was washed with water and dried to obtain 200 kg of powder. The composition of the obtained fluoropolymer was TFE / Et / HFP / HF-Pa = 40.8 / 44.8 / 13.9 / 0.5 (mol%). The melting point of the obtained fluoropolymer was 162.5°C, and the MFR was 2.6 g / 10 min under the conditions of 230°C and a load of 49 N (5 kg).

[0366] Production Example 8 (VDF / TFP elastomer (elastomer A)) 4000 ml of pure water was placed in a 6 L stainless steel autoclave, and the autoclave was purged with nitrogen. 0.09 ml of 2-methylbutane was introduced under vacuum, and then vinylidene fluoride (VdF) was slightly pressurized. While stirring at 600 rpm, the temperature was adjusted to 80 °C, and VdF was injected until the pressure reached 1.62 MPaG. Further, a mixed liquid monomer with a molar ratio of VdF to 2,3,3,3-tetrafluoropropene of 76.5 / 23.5 was injected until the pressure reached 2.001 MPaG. A solution prepared by dissolving 0.952 g of ammonium persulfate in 5 ml of pure water was injected with nitrogen to initiate polymerization. Continuous monomer was supplied to maintain the pressure at 2.0 MPaG. After 3.6 hours from the start of polymerization, when 1.0 kg of continuous monomer was charged, stirring was stopped, the gas in the autoclave was released, and the autoclave was cooled to recover 5.0 kg of the dispersion. The solid content of the dispersion was 20.27 wt%. The obtained elastomer contained VdF and 2,3,3,3-tetrafluoropropene in a molar ratio of 77.2 / 22.8. The Mooney viscosity (ML1+10(140 °C)) of the obtained elastomer was 135, the weight average molecular weight was 1,600,000, the Tg was -12 °C by DSC, and the ratio of the contained polar groups was 0.03. Also, the heat of fusion was not observed in the second run.

[0367] Production Example 9 (VDF / HFP Elastomer (Elastomer B)) 1650 ml of pure water was placed in a 3 L stainless steel autoclave, and the autoclave was purged with nitrogen. Hexafluoropropylene (HFP) was slightly pressurized, and while stirring at 380 rpm, the temperature was adjusted to 80 °C, and HFP was injected until the pressure reached 0.23 MPaG. Further, a mixed liquid monomer with a molar ratio of vinylidene fluoride (VdF) to HFP of 78.2 / 21.8 was injected until the pressure reached 1.472 MPaG. 0.097 ml of 2-methylbutane was injected with nitrogen, and a solution prepared by dissolving 36.4 g of ammonium persulfate in 80 ml of pure water was injected with nitrogen to initiate polymerization. When the pressure dropped to 1.44 MPaG, the pressure was increased to 1.50 MPaG with continuous monomer and maintained. After about 9.3 hours from the start of polymerization, when 607 g of continuous monomer was charged, stirring was stopped, the gas in the autoclave was released, and the autoclave was cooled to recover 2299 g of the dispersion. The solid content of the dispersion was 26.9 wt%. The resulting elastomer contained VdF and HFP at a molar ratio of 77.9 / 22.1. The Mooney viscosity (ML1+10(140°C)) of the resulting elastomer was 77, the weight-average molecular weight was 850,000, the Tg was -18°C by DSC, and the proportion of the contained polar groups was 0.05. Also, the heat of fusion was not observed in the second run.

[0368] Production Example 1 692 g of the PTFE-1 aqueous dispersion obtained in Production Example 1 and 850 g of the PVDF aqueous dispersion obtained in Production Example 4 were placed in a container, and while stirring at high speed, the PTFE / PVDF mixture was co-precipitated, and then separated from water by filtration to obtain a wet powder. The obtained wet powder was placed on a stainless steel mesh tray, and the mesh tray was heat-treated in a hot air circulation type electric furnace at 130°C. After 20 hours, the mesh tray was taken out, and after air-cooling the mesh tray, a PTFE / PVDF mixed powder was obtained. The mixing ratio (mass ratio) of the obtained PTFE / PVDF mixed powder was PTFE / PVDF = 50 / 50. An image of the obtained powder observed under a microscope is shown in Fig. 1. The obtained PTFE / PVDF mixed powder was used as Binder 1.

[0369] Production Example 2 298 g of the PTFE-1 powder obtained in Production Example 2, 255 g of the PVDF aqueous dispersion obtained in Production Example 4, and 1000 g of deionized water were placed in a container, and while stirring, co-precipitation and drying were carried out in the same manner as in Production Example 1 to obtain a mixed powder. The mixing ratio (mass ratio) of the obtained PTFE / PVDF mixed powder was PTFE / PVDF = 85 / 15. The obtained PTFE / PVDF mixed powder was used as Binder 2.

[0370] Production Example 3 1176 g of the PTFE-1 aqueous dispersion obtained in Production Example 1, 53 g of the PVDF powder obtained in Production Example 5, and 1113 g of deionized water were placed in a container, and while stirring at high speed, co-precipitation and drying were carried out in the same manner as in Production Example 1 to obtain a mixed powder. The mixing ratio (mass ratio) of the obtained PTFE / PVDF mixed powder was PTFE / PVDF = 85 / 15. The obtained PTFE / PVDF mixed powder was used as Binder 3.

[0371] Production Example 4 1176 g of the PTFE-1 aqueous dispersion obtained in Production Example 1, 53 g of the VdF / TFE copolymer (fluoropolymer A) powder obtained in Production Example 6, and 1113 g of deionized water were placed in a container, and co-precipitated and dried in the same manner as in Production Example 1 while stirring at high speed to obtain a mixed powder. The mixing ratio (mass ratio) of the obtained PTFE / fluoropolymer A mixed powder was PTFE / fluoropolymer A = 85 / 15. The obtained PTFE / fluoropolymer A mixed powder was used as Binder 4.

[0372] Production Example 5 1176 g of the PTFE-1 aqueous dispersion obtained in Production Example 1, 53 g of the Et / TFE / HFP copolymer (EFEP) powder obtained in Production Example 7, and 1113 g of deionized water were placed in a container, and co-precipitated and dried in the same manner as in Production Example 1 while stirring at high speed to obtain a mixed powder. The mixing ratio (mass ratio) of the obtained PTFE / EFEP mixed powder was PTFE / EFEP = 85 / 15. The obtained PTFE / EFEP mixed powder was used as Binder 5.

[0373] Production Example 6 1002 g of the PTFE-2 aqueous dispersion obtained in Production Example 3, 255 g of the PVDF aqueous dispersion obtained in Production Example 4, and 1032 g of deionized water were placed in a container, and co-precipitated and dried in the same manner as in Production Example 1 while stirring at high speed to obtain a mixed powder. The mixing ratio (mass ratio) of the obtained PTFE / PVDF mixed powder was PTFE / PVDF = 85 / 15. The obtained PTFE / PVDF mixed powder was used as Binder 6.

[0374] Production Example 7 1245 g of the PTFE-1 aqueous dispersion obtained in Production Example 1, 173 g of the VDF / TFP elastomer (elastomer A) aqueous dispersion of Production Example 8, and 1005 g of deionized water were placed in a container and co-precipitated and dried in the same manner as in Preparation Example 1 while being stirred at high speed to obtain a mixed powder. The mixing ratio (mass ratio) of the obtained PTFE / elastomer A mixed powder was PTFE / elastomer A = 90 / 10. The obtained PTFE / elastomer A mixed powder was used as binder 7.

[0375] Preparation Example 8 1107 g of the PTFE-1 aqueous dispersion obtained in Production Example 1 and 260 g of the VDF / HFP elastomer (elastomer B) aqueous dispersion of Production Example 9 were placed in a container and co-precipitated and dried in the same manner as in Preparation Example 1 while being stirred at high speed to obtain a mixed powder. The mixing ratio (mass ratio) of the obtained PTFE / elastomer B mixed powder was PTFE / elastomer B = 80 / 20. The obtained PTFE / elastomer B mixed powder was used as binder 8.

[0376] Preparation Example 9 85 g of the PTFE-1 powder obtained in Production Example 2 and 15 g of the PVDF powder obtained in Production Example 5 were placed in a high-speed mixer and mixed at 20,000 rpm for 2 minutes. The mixing ratio (mass ratio) of the obtained PTFE / PVDF mixed powder was PTFE / PVDF = 85 / 15. Since the average particle diameter exceeded 2000 μm, it could not be measured. The obtained PTFE / PVDF mixed powder was used as binder 9. The results of the binders obtained in Preparation Examples 1 to 9 are shown in Table 1.

[0377]

Table 1

[0378] (Examples 1 to 7, Comparative Example 1) Using each of the powders obtained above, a positive electrode active material sheet, an electrode, and a lithium ion secondary battery were produced and evaluated by the following method. Each binder powder, the electrode active material NMC811 (LiNi 0.8 Co 0.1 Mn 0.1 O2), and the conductive additive (SuperP Li manufactured by Imerys) were weighed so as to have the compositions (mass ratios) shown in Tables 2 and 4. In order to suppress fibrillation, the material mixing process was carried out at 19°C or lower. After cooling the weighed materials to -25°C, they were put into a blender and stirred at 8000 rpm for a total of 1 minute. Then, they were put into a pressure kneader heated to 30°C and kneaded at 50 rpm for 5 minutes to obtain an electrode binder powder. The electrode binder powder obtained was rolled between metal rolls arranged in parallel to process the electrode binder powder into a bulk shape. Similarly, by passing the bulk electrode binder through the rolls and rolling it multiple times, a self-supporting electrode binder sheet was produced. The temperature of the metal rolls was set at 100°C. The thickness of the electrode binder sheet was adjusted to approximately 100 μm. Test pieces were cut out from this electrode binder sheet and subjected to an evaluation of the tensile strength variation. Also, this electrode binder sheet was cut into pieces 40 mm wide, placed on an aluminum foil of the size of the electrode binder sheet with a roughened surface, and rolled with a roll press heated to 100°C (roll gap 100 μm, press pressure 15 KN) to produce an electrode.

[0379] (Examples 8, 10, Comparative Example 2) Each binder powder, the positive electrode active material NMC811 (LiNi 0.8 Co 0.1 Mn 0.1 O2), the sulfide-based solid electrolyte LPS (0.75Li2S·0.25P2S5), and the conductive additive (SuperP Li manufactured by Imerys) were added and adjusted to the compositions (mass ratios) shown in Tables 3 and 4. Other processing procedures were carried out in the same manner as in Example 1.

[0380] (Examples 9, 11, Comparative Example 3) Each binder powder, the negative electrode active material graphite, the sulfide-based solid electrolyte LPS (0.75Li2S·0.25P2S5), and the conductive additive (SuperP Li manufactured by Imerys) were added and adjusted to the compositions (mass ratios) shown in Tables 3 and 4. Other processing procedures were carried out in the same manner as in Example 1.

[0381] [Tensile Strength Variation Evaluation] Measurement was carried out using a tensile testing machine (Autograph AGS-X series AGS-100NX manufactured by Shimadzu Corporation) on strip-shaped electrode composite sheet test pieces with a width of 4 mm under the condition of 100 mm / min. The distance between the chucks was set to 30 mm. Displacement was applied until breakage, and the maximum stress of the measured results was taken as the strength of each test piece. The average value was obtained for each experiment, and the average maximum stress of Comparative Example 1 or Comparative Example 2 and Comparative Example 3 was set to 100. Also, the standard deviation was obtained, and the coefficient of variation CV (standard deviation ÷ average × 100) was calculated and used as the evaluation value of the variation. The variation of the tensile strength was evaluated. The results are shown in Tables 2 to 4.

[0382] [Peeling Strength between Electrode Binder and Current Collector] Test pieces of 1.0 cm × 5.0 cm were prepared by cutting the electrodes. After fixing the electrode material layer side of the test piece to a movable jig with double-sided tape, a tape was attached to the surface of the current collector, and the stress (N / cm) when the tape was pulled at a speed of 100 mm / min at 90 degrees was measured with an autograph. The values in the stable range of the stress were averaged to measure the peeling strength. The test was conducted with n = 5, and the average value was used as the evaluation value. A 1N load cell was used for the autograph. For the comparative examples, ◎: Further better (126% or more) ○: Good (106 - 125%) △: Equivalent to the comparative example (105 - 95%) Scoring was performed as follows.

[0383] [Table 2]

[0384] [Table 3]

[0385] [Table 4]

Claims

1. A composite binder material comprising (a) polytetrafluoroethylene (PTFE), (b) a low melting point thermoplastic resin, and (c) a conductive aid.

2. The composite binder material according to claim 1, wherein the composite binder material is particles.

3. The composite binder material according to claim 1 or 2, wherein the composite binder material is a condensate.

4. The composite binder material according to claim 1 or 2, wherein the conductive aid is present in an amount of about 20% by mass or less.

5. The composite binder material according to claim 1 or 2, wherein the conductive aid is present in an amount of about 0.01% by mass or more.

6. The composite binder material according to claim 1 or 2, wherein the low melting point thermoplastic resin is present in an amount of about 0.01 to about 50% by mass.

7. The composite binder material according to claim 1 or 2, wherein the low melting point thermoplastic resin is present in an amount of about 5 to about 20% by mass.

8. The composite binder material according to claim 1 or 2, wherein the low melting point thermoplastic resin is a low melting point fluoropolymer.

9. The composite binder material according to claim 1 or 2, wherein the PTFE is present in an amount of about 25 to about 99% by mass.

10. The composite binder material according to claim 1 or 2, wherein the PTFE consists of a homopolymer or a perfluorocopolymer.

11. The composite binder material according to claim 1 or 2, wherein the PTFE is a modified PTFE consisting of TFE and a modified monomer copolymerizable with TFE.

12. The composite binder material according to claim 1 or 2, wherein the PTFE is a high molecular weight PTFE having a standard specific gravity of 2.20 or less.

13. The composite binder material according to claim 1 or 2, wherein the low melting point thermoplastic resin has a melting point of less than 375°C.

14. The composite binder material according to claim 1 or 2, wherein the low melting point thermoplastic resin has a melting point of less than 200°C.

15. The low melting point thermoplastic resin is a low melting point fluoropolymer, and the low melting point fluoropolymer is PVdF, FEP, EFEP, ETFE, THV, FKM, FFKM, PFA, PVF, or a combination of two or more of the above, according to claim 1 or 2 of the composite binder material.

16. The composite binder material according to claim 1 or 2, wherein the low melting point thermoplastic resin is a low melting point non-fluorinated polymer.

17. The composite binder material according to claim 16, wherein the low melting point non-fluorinated polymer is a polyolefin, PE, PP, PA, nylon, PS, TPU, PI, PA, PC, PLA, PEEK, PEG / PEO, or a combination of two or more of the above.

18. The composite binder material according to claim 1 or 2, wherein the low melting point thermoplastic resin is in particulate form.

19. The composite binder material according to claim 1 or 2, wherein the low melting point thermoplastic resin is a powder having an average particle diameter of about 700 μm or less.

20. The composite binder material according to claim 1 or 2, wherein the low melting point thermoplastic resin is an emulsion having an average primary particle diameter of about 500 nm or less.

21. The composite binder material according to claim 1 or 2, wherein the conductive aid is conductive carbon.

22. The composite binder material according to claim 1 or 2, wherein the conductive aid is carbon nanoparticles, carbon nanotubes, carbon black, acetylene black, or a combination of two or more of the above.

23. The composite binder material according to claim 1 or 2, wherein the adhesive strength with high purity aluminum measured by an adhesive strength test using a 25 mm wide film having high purity aluminum on both sides is more than 1 N / mm.

24. The composite binder material according to claim 1 or 2, which has conductivity.

25. Step (a) of obtaining a PTFE emulsion, Step (b) of mixing the PTFE emulsion with low melting point thermoplastic resin and conductive aid particles to form a first mixture, and A method for producing a composite binder material, comprising step (c) of coagulating the first mixture to produce a coagulate composed of the composite binder material.

26. The production method according to claim 25, further comprising a step of drying the coagulate.

27. The production method according to claim 25 or 26, further comprising a step of drying the coagulate at a temperature of less than about 375 °C.

28. The production method according to claim 25 or 26, wherein the coagulation step is carried out at a temperature of about 90 °C or less.

29. The composite binder material is particles according to the production method of claim 25 or 26.

30. The manufacturing method according to claim 25 or 26, wherein the composite binder material is a condensate.

31. The manufacturing method according to claim 25 or 26, wherein the conductive auxiliary agent is present in an amount of about 20% by mass or less.

32. The manufacturing method according to claim 25 or 26, wherein the conductive auxiliary agent is present in an amount of about 0.01% by mass or more.

33. The manufacturing method according to claim 25 or 26, wherein the low melting point thermoplastic resin is present in an amount of about 0.01 to about 50% by mass.

34. The manufacturing method according to claim 25 or 26, wherein the low melting point thermoplastic resin is present in an amount of about 5 to about 20% by mass.

35. The manufacturing method according to claim 25 or 26, wherein the low melting point thermoplastic resin is a low melting point fluoropolymer.

36. The manufacturing method according to claim 25 or 26, wherein the PTFE is present in an amount of about 25 to about 99% by mass.

37. The manufacturing method according to claim 25 or 26, wherein the PTFE consists of a homopolymer or a perfluorocopolymer.

38. The manufacturing method according to claim 25 or 26, wherein the PTFE is a modified PTFE consisting of TFE and a modified monomer copolymerizable with TFE.

39. The manufacturing method according to claim 25 or 26, wherein the PTFE is a high molecular weight PTFE having a standard specific gravity of 2.20 or less.

40. The manufacturing method according to claim 25 or 26, wherein the low melting point thermoplastic resin has a melting point of less than 375°C.

41. The manufacturing method according to claim 25 or 26, wherein the low melting point thermoplastic resin has a melting point of less than 200°C.

42. The low melting point thermoplastic resin is a low melting point fluoropolymer, The manufacturing method according to claim 25 or 26, wherein the low melting point fluoropolymer is PVdF, FEP, EFEP, ETFE, THV, FKM, FFKM, PFA, PVF, or a combination of two or more thereof.

43. The manufacturing method according to claim 25 or 26, wherein the low melting point thermoplastic resin is a low melting point non-fluorinated polymer.

44. The manufacturing method according to claim 43, wherein the low melting point non-fluorinated polymer is a polyolefin, PE, PP, PA, Nylon, PS, TPU, PI, PA, PC, PLA, PEEK, PEG / PEO, or a combination of two or more thereof.

45. The manufacturing method according to any one of claims 25 or 26, wherein the low melting point thermoplastic resin is in particulate form.

46. The manufacturing method according to any one of claims 25 or 26, wherein the low melting point thermoplastic resin is a powder having an average particle diameter of about 700 μm or less.

47. The manufacturing method according to any one of claims 25 or 26, wherein the low melting point thermoplastic resin is an emulsion having an average primary particle diameter of about 500 nm or less.

48. The manufacturing method according to any one of claims 25 or 26, wherein the conductive auxiliary agent is conductive carbon.

49. The manufacturing method according to any one of claims 25 or 26, wherein the conductive auxiliary agent is carbon nanoparticles, carbon nanotubes, carbon black, acetylene black, or a combination of two or more of the above.

50. The manufacturing method according to any one of claims 25 or 26, wherein the composite binder material has an adhesive strength with high purity aluminum measured by an adhesive strength test using a 25 mm wide film having high purity aluminum on both sides of more than 1 Nmm.

51. The manufacturing method according to any one of claims 25 or 26, wherein the composite binder material has conductivity.

52. A composite binder material manufactured by the manufacturing method according to any one of claims 25 or 26.

53. An electrode comprising the composite binder material according to claim 1 or 2.

54. Comprising an electrode, The energy storage device, wherein the electrode is made of the composite binder material according to claim 1 or 2.

55. The energy storage device according to claim 54, further comprising a second electrode containing the composite binder material according to claim 1 or 2.

56. The energy storage device according to claim 54, wherein the electrode is a cathode.

57. The energy storage device according to claim 54, which is a battery.

58. The energy storage device according to claim 54, which is a supercapacitor.

59. A binder powder for an electrochemical device comprising a resin having fibrillatable properties that are not fibrillated and a thermoplastic polymer.

60. The binder powder for an electrochemical device according to claim 59, wherein the thermoplastic polymer is a thermoplastic resin.

61. The binder powder for an electrochemical device according to claim 59 or 60, wherein the thermoplastic resin has a melting point of 100 to 310 °C.

62. The thermoplastic resin is the binder powder for an electrochemical device according to claim 59 or 60, which is a fluoropolymer.

63. The thermoplastic resin is the binder powder for an electrochemical device according to claim 59 or 60, having a melt flow rate of 0.01 to 500 g / 10 min.

64. The thermoplastic polymer is the binder powder for an electrochemical device according to claim 59, which is an elastomer having a glass transition temperature of 25°C or lower.

65. The elastomer is the binder powder for an electrochemical device according to claim 64, which is a fluoroelastomer.

66. The fluoroelastomer is the binder powder for an electrochemical device according to claim 65, containing vinylidene fluoride units and other monomer units copolymerizable with vinylidene fluoride.

67. The resin having fibrillating properties is the binder powder for an electrochemical device according to any one of claims 59, 60, 64, 65, and 66, having a glass transition temperature of 10 to 30°C.

68. The resin having fibrillating properties is the binder powder for an electrochemical device according to any one of claims 59, 60, 64, 65, and 66, which is polytetrafluoroethylene.

69. The binder powder for an electrochemical device according to claim 68 contains 50% by mass or more of the polytetrafluoroethylene.

70. The polytetrafluoroethylene is the binder powder for an electrochemical device according to claim 68, having a peak temperature of 333 to 347°C.

71. The binder powder for an electrochemical device according to any one of claims 59, 60, 64, 65, and 66 has a water content of 1000 ppm by mass or less.

72. The binder powder for an electrochemical device according to any one of claims 59, 60, 64, 65, and 66 has an average primary particle diameter of 10 to 500 nm.

73. The resin having fibrillating properties is in particle form, and the ratio of the number of resin particles having an aspect ratio of 30 or more to the total number of resin particles having fibrillating properties is 20% or less in the binder powder for an electrochemical device according to any one of claims 59, 60, 64, 65, and 66.

74. The binder powder for an electrochemical device according to any one of claims 59, 60, 64, 65, and 66 has an average particle diameter of 1000 μm or less.

75. The binder powder for an electrochemical device according to any one of claims 59, 60, 64, 65, and 66, which is for a secondary battery.

76. The binder powder for an electrochemical device according to any one of claims 59, 60, 64, 65, and 66, further comprising a carbon-based conductive assistant.

77. An electrode binder obtained by using the binder powder for an electrochemical device according to any one of claims 59, 60, 64, 65, and 66.

78. Furthermore, the electrode binder according to claim 77, obtained by using an active material.

79. The electrode binder according to claim 77, which is a positive electrode binder.

80. An electrode for a secondary battery obtained by using the binder powder for an electrochemical device according to any one of claims 59, 60, 64, 65, and 66.

81. A secondary battery comprising the electrode for a secondary battery according to claim 80.

82. A step (1) of producing a mixture containing a fibrillatable resin, a thermoplastic polymer, and water, and A method for producing a binder powder for an electrochemical device, comprising a step (2) of producing a powder from the mixture.

83. In the step (2), the step (2-1) of aggregating a composition containing the fibrillatable resin and the thermoplastic polymer from the mixture to obtain an aggregate, and The production method according to claim 82, comprising a step (2-2) of heat-treating the aggregate.

84. In the step (1), the production method according to claim 82 or 83, wherein a dispersion liquid containing the thermoplastic polymer having an average primary particle diameter of 50 μm or less is mixed with the fibrillatable resin and water.

85. A binder for an electrochemical device, comprising a fibrillatable resin and an ethylene / tetrafluoroethylene copolymer.

86. A binder for an electrochemical device, comprising a fibrillatable resin and an elastomer having a glass transition temperature of 25°C or less.

87. The binder for an electrochemical device according to claim 85 or 86, wherein the binder for an electrochemical device is a powder.

88. The binder for an electrochemical device according to claim 86, wherein the elastomer is a fluoroelastomer.

89. The binder for an electrochemical device according to claim 88, wherein the fluoroelastomer contains a vinylidene fluoride unit and other monomer units copolymerizable with vinylidene fluoride.

90. The binder for an electrochemical device according to any one of claims 85, 86, 88, and 89, wherein the resin having fibrillation properties has a glass transition temperature of 10 to 30°C.

91. The binder for an electrochemical device according to any one of claims 85, 86, 88, and 89, wherein the resin having fibrillation properties is polytetrafluoroethylene.

92. The binder for an electrochemical device according to claim 91, which contains 50% by mass or more of the polytetrafluoroethylene.

93. The binder for an electrochemical device according to claim 91, wherein the polytetrafluoroethylene has a peak temperature of 333 to 347°C.

94. The binder for an electrochemical device according to any one of claims 85, 86, 88, and 89, wherein the water content is 1000 ppm by mass or less.

95. The binder for an electrochemical device according to any one of claims 85, 86, 88, and 89, wherein the average primary particle diameter is 10 to 500 nm.

96. The binder for an electrochemical device according to any one of claims 85, 86, 88, and 89, which is for a secondary battery.

97. Furthermore, the binder for an electrochemical device according to any one of claims 85, 86, 88, and 89, which contains a carbon-based conductive assistant.

98. An electrode mixture obtained by using the binder for an electrochemical device according to any one of claims 85, 86, 88, and 89.

99. Furthermore, the electrode mixture according to claim 98, which contains an active material.

100. The electrode mixture according to claim 99, which is a positive electrode mixture.

101. An electrode for a secondary battery obtained by using the binder for an electrochemical device according to any one of claims 85, 86, 88, and 89.

102. A secondary battery including the electrode for a secondary battery according to claim 101.

Images