Tetrafluoroethylene polymer composition, binder for electrochemical device, electrode mixture, electrode, and secondary battery

Abstract

Provided are: a tetrafluoroethylene-based polymer composition for a binder for electrochemical devices, which can be uniformly mixed with a powder component of an electrochemical device, and which is capable of obtaining a mixture sheet having excellent strength and flexibility; and a binder for electrochemical devices, an electrode mixture, an electrode, and a secondary battery, each of which uses the tetrafluoroethylene-based polymer composition. A tetrafluoroethylene polymer composition which is used as a binder for electrochemical devices and which has endothermic peaks in a region (A) of 330 DEG C or more and less than 340 DEG C and a region (B) of 340 DEG C or more and 350 DEG C or less in differential scanning calorimetry.

Description

Technical Field

[0001] The present invention relates to a tetrafluoroethylene polymer composition, a binder for electrochemical devices, an electrode mixture, an electrode and a secondary battery. Background Art

[0002] Secondary batteries such as lithium-ion secondary batteries are used in small and portable electrical and electronic devices such as notebook computers, mobile phones, smartphones, tablet computers, and ultra-notebooks due to their high voltage, high energy density, low self-discharge, minimal memory effect, and ability to be ultra-lightweight. They are also being put into practical use as power sources for driving vehicles and large stationary power supplies, such as in automobiles. There is a growing demand for secondary batteries to achieve higher energy density and further improvements in electrochemical device characteristics.

[0003] Patent Document 1 describes an energy storage device in which at least one of the cathode and the anode contains a polytetrafluoroethylene mixed binder material.

[0004] Patent Documents 2 to 6 describe the use of polytetrafluoroethylene as a binder for batteries.

[0005] Patent Document 7 describes the use of a mixture of polytetrafluoroethylene and polyvinylidene fluoride as a binder for a battery.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application No. 2017-517862

[0009] Patent Document 2: International Publication No. 2021 / 181887

[0010] Patent Document 3: International Publication No. 2021 / 181888

[0011] Patent Document 4: International Publication No. 2021 / 192541

[0012] Patent Document 5: International Publication No. 2022 / 138942

[0013] Patent Document 6: International Publication No. 2022 / 138939

[0014] Patent Document 7: International Publication No. 2022 / 234227 Summary of the Invention

[0015] Technical problem to be solved by the invention

[0016] The object of the present invention is to provide a tetrafluoroethylene polymer composition for use as a binder for electrochemical devices, which can be uniformly mixed with the powder components of the electrochemical device and can produce a composite sheet having excellent strength and flexibility, as well as a binder for electrochemical devices, an electrode composite, an electrode and a secondary battery using the same.

[0017] Means of solving technical problems

[0018] The present invention (1) is a tetrafluoroethylene polymer composition for use as a binder for electrochemical devices, wherein, in differential scanning calorimetry analysis, the composition has endothermic peaks in a region (A) of 330°C or higher and lower than 340°C and in a region (B) of 340°C or higher and 350°C or lower.

[0019] The present invention (2) is an adhesive for electrochemical devices, which is an adhesive for electrochemical devices substantially composed only of a tetrafluoroethylene polymer composition, wherein the above-mentioned tetrafluoroethylene polymer composition has endothermic peaks in a region (A) above 330°C and below 340°C and a region (B) above 340°C and below 350°C in differential scanning calorimetry analysis.

[0020] The present invention (3) is the binder for electrochemical devices described in the present invention (2), wherein the intensity ratio of the above-mentioned tetrafluoroethylene polymer composition represented by the intensity of the endothermic peak in the above-mentioned region (A) / the intensity of the endothermic peak in the above-mentioned region (B) is greater than 0.5.

[0021] The present invention (4) is the binder for electrochemical devices described in the present invention (3), wherein the intensity ratio of the above-mentioned tetrafluoroethylene polymer composition, expressed as the intensity of the endothermic peak in the above-mentioned region (A) / the intensity of the endothermic peak in the above-mentioned region (B), is 0.8 to 2.0.

[0022] The present invention (5) is a binder for electrochemical devices according to any one of the present inventions (2) to (4), wherein the tetrafluoroethylene polymer composition comprises a tetrafluoroethylene copolymer, which comprises a tetrafluoroethylene unit and a modified monomer unit based on a modified monomer copolymerizable with tetrafluoroethylene.

[0023] The present invention (6) is the binder for electrochemical devices according to the present invention (5), wherein the content of the modified monomer unit in the tetrafluoroethylene copolymer is 10% by mass or less relative to the total polymerized units.

[0024] The present invention (7) is a binder for electrochemical devices according to any one of the present inventions (2) to (6), wherein the tetrafluoroethylene polymer composition comprises a tetrafluoroethylene unit and a modified monomer unit based on a modified monomer copolymerizable with tetrafluoroethylene.

[0025] The present invention (8) is the binder for electrochemical devices according to the present invention (7), wherein the content of the modified monomer unit in the tetrafluoroethylene polymer composition is 0.20% by mass or less relative to the total polymer units.

[0026] The present invention (9) is the binder for an electrochemical device according to any one of the present inventions (5) to (8), wherein the modifying monomer is a compound represented by the following general formula (I).

[0027] CX 1 X 2 =CX 3 X 4 (I)

[0028] (Where, X 1 ~X 3 Each independently represents H or F. X 4 is F, Cl, Rf or O-Rf. Rf is a perfluorinated organic group.)

[0029] The present invention (10) is the binder for electrochemical devices according to the present invention (9), wherein the modifying monomer is at least one selected from the group consisting of chlorotrifluoroethylene and hexafluoropropylene.

[0030] The present invention (11) is the binder for electrochemical devices according to any one of the present inventions (2) to (10), wherein the tetrafluoroethylene polymer composition is stretchable.

[0031] The present invention (12) is a binder for electrochemical devices according to any one of the present inventions (2) to (11), wherein the tetrafluoroethylene polymer composition comprises a tetrafluoroethylene copolymer having an extrusion pressure of 75 MPa or less at a compression ratio of 1000.

[0032] The present invention (13) is the binder for electrochemical devices according to any one of the present inventions (2) to (12), wherein the tetrafluoroethylene polymer composition is a powder.

[0033] The present invention (14) is the binder for electrochemical devices according to any one of the present inventions (2) to (13), wherein the tetrafluoroethylene polymer composition contains substantially no water.

[0034] The present invention (15) is the binder for electrochemical devices according to any one of the present inventions (2) to (14), wherein the tetrafluoroethylene polymer composition does not substantially contain a fluorine-containing compound having a molecular weight of 1000 or less.

[0035] The present invention (16) is the binder for electrochemical devices according to any one of the present inventions (2) to (15), wherein the content of the fluorine-based polymer is 90% by mass or more relative to the tetrafluoroethylene-based polymer composition.

[0036] The present invention (17) is the binder for electrochemical devices according to any one of the present inventions (2) to (16), wherein the tetrafluoroethylene polymer composition comprises two or more tetrafluoroethylene polymers.

[0037] The present invention (18) is the binder for electrochemical devices according to any one of the present inventions (2) to (17), wherein the tetrafluoroethylene polymer in the tetrafluoroethylene polymer composition is polytetrafluoroethylene.

[0038] The present invention (19) is the binder for electrochemical devices according to any one of the present inventions (2) to (18), wherein the average aspect ratio of the powder of the fluorine-based polymer composition is 2.5 or less.

[0039] The present invention (20) is an electrode mixture comprising the tetrafluoroethylene polymer composition described in the present invention (1) or the binder for electrochemical devices described in any one of the present inventions (2) to (19), and an electrode active material.

[0040] The present invention (21) is the electrode mixture described in the present invention (20), which is a sheet.

[0041] The present invention (22) is an electrode comprising the tetrafluoroethylene polymer composition described in the present invention (1) or the binder for electrochemical devices described in any one of the present inventions (2) to (19), an electrode active material, and a current collector.

[0042] The present invention (23) is a secondary battery comprising the electrode according to the present invention (22).

[0043] Effects of the Invention

[0044] The present invention provides a tetrafluoroethylene polymer composition for use as a binder for electrochemical devices that can be uniformly mixed with powder components of electrochemical devices and can produce a composite sheet having excellent strength and flexibility, as well as a binder for electrochemical devices, an electrode composite, an electrode, and a secondary battery using the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of a cross section of a pressure cell used for measuring the ion conductivity of a solid electrolyte mixture sheet in Examples. DETAILED DESCRIPTION

[0046] The present invention will be described in detail below.

[0047] The present invention provides a tetrafluoroethylene (TFE) polymer composition for use as a binder for electrochemical devices, wherein the composition has endothermic peaks in a region (A) of 330°C or higher and lower than 340°C and in a region (B) of 340°C or higher and 350°C or lower in differential scanning calorimetry analysis.

[0048] Because the TFE-based polymer composition of the present invention has endothermic peaks in the aforementioned regions (A) and (B), it is unlikely to form aggregates even when kneaded for extended periods with powder components of electrochemical devices, such as electrode active materials and solid electrolytes, allowing for uniform mixing with these powder components. Furthermore, a composite sheet exhibiting excellent strength and flexibility can be obtained.

[0049] Furthermore, the TFE-based polymer composition of the present invention does not require the use of large amounts of dispersion media such as water or organic solvents, allowing for a wide selection of electrode active materials and solid electrolytes to be combined, which is advantageous in terms of production processes. Furthermore, the process and costs associated with using dispersion media can be reduced.

[0050] Furthermore, the TFE-based polymer composition of the present invention has excellent binding strength with active materials and electrolytes, and thus the amount used can be reduced.

[0051] The TFE-based polymer composition of the present invention has endothermic peaks in the above region (A) and the above region (B) in differential scanning calorimetry [DSC].

[0052] This means that the TFE polymer composition of the present invention contains a TFE polymer (A) having an endothermic peak in the region (A) and a TFE polymer (B) having an endothermic peak in the region (B).

[0053] The TFE-based polymer (A) having an endothermic peak in region (A) has low fibrillation properties. Therefore, the presence of this TFE-based polymer reduces fibrillation in the TFE-based polymer composition, making it less likely to form aggregates even when kneaded with the powder components of an electrochemical device for extended periods of time. This allows for uniform mixing with the powder components, and also enhances the strength and flexibility of the resulting composite sheet.

[0054] The temperature range of the zone (A) is 330°C or higher and lower than 340°C, preferably 333°C or higher, and more preferably 336°C or higher.

[0055] The temperature range of zone (B) is 340°C or higher and 350°C or lower, preferably 348°C or lower, and more preferably 346°C or lower.

[0056] The endothermic peak temperature is the temperature corresponding to the respective minimum points in region (A) and region (B) of the heat of fusion curve when a TFE-based polymer composition that has no history of heating to a temperature of 300°C or higher is heated at a rate of 2°C / min using a differential scanning calorimeter [DSC].

[0057] From the perspective of being able to mix more uniformly with the powder components of the electrochemical device and to obtain a composite sheet with superior strength and flexibility, the TFE-based polymer composition of the present invention has an intensity ratio represented by the intensity of the endothermic peak in the above-mentioned region (A) / the intensity of the endothermic peak in the above-mentioned region (B) of preferably 0.5 or more, more preferably 0.6 or more, further preferably 0.7 or more, and even more preferably 0.8 or more. In addition, it is preferably 3.0 or less, more preferably 2.5 or less, further preferably 2.0 or less, and even more preferably 1.5 or less.

[0058] The intensity of the endothermic peak is determined as the distance between the minimum point (a) and the intersection point (b), where the minimum point of the heat of fusion curve in the measurement of the endothermic peak temperature is defined as (a) and the intersection point (b) of a straight line passing through the minimum point (a) and perpendicular to the horizontal axis (temperature) and a straight line connecting the points of 305°C and 355°C on the heat of fusion curve is defined as.

[0059] The intensity ratio can be adjusted by adjusting the mixing ratio of the TFE polymer (A) having an endothermic peak in the region (A) and the TFE polymer (B) having an endothermic peak in the region (B).

[0060] The TFE polymer composition of the present invention comprises a TFE polymer. The TFE polymer composition of the present invention preferably comprises two or more TFE polymers, and more preferably comprises two TFE polymers. The TFE polymer composition of the present invention preferably comprises the aforementioned TFE polymers (A) and (B) as the two or more TFE polymers.

[0061] The TFE-based polymer may be a tetrafluoroethylene (TFE) homopolymer or a TFE copolymer comprising polymerized units derived from TFE (TFE units) and polymerized units derived from a modifying monomer copolymerizable with TFE (hereinafter also referred to as "modified monomer units").

[0062] The TFE homopolymer mentioned above means that the content of the modifying monomer unit relative to all polymerized units is less than 0.0001% by mass.

[0063] In this specification, the TFE copolymer may contain 90.0% by mass or more of TFE units and 10.0% by mass or less of modified monomer units. Alternatively, the TFE copolymer may consist solely of TFE units and modified monomer units.

[0064] The TFE-based polymer composition of the present invention preferably contains the above-mentioned TFE copolymer from the viewpoints of enabling more uniform mixing with the powder components of the electrochemical device and obtaining a composite sheet having superior strength and flexibility.

[0065] At least one of the TFE-based polymer (A) having an endothermic peak in region (A) and the TFE-based polymer (B) having an endothermic peak in region (B) is preferably a TFE copolymer, more preferably at least the TFE-based polymer (A) is a TFE copolymer, and even more preferably both the TFE-based polymers (A) and (B) are TFE copolymers.

[0066] The TFE polymer is preferably polytetrafluoroethylene (PTFE). The PTFE includes a homopolymer of TFE and a modified PTFE comprising 99.0% by mass or more of TFE units and 1.0% by mass or less of a modified monomer unit. The modified PTFE may consist solely of TFE units and modified monomer units.

[0067] It is preferred that at least one of the TFE polymer (A) and the TFE polymer (B) is modified PTFE, more preferably at least the TFE polymer (A) is modified PTFE, and even more preferably both the TFE polymers (A) and (B) are modified PTFE.

[0068] From the aspect that can be more evenly mixed with the powder component of electrochemical device and can obtain the composite sheet with better strength and flexibility, the content of the above-mentioned TFE copolymer preferably modified monomer unit is the range of 0.0001~10.0 mass % relative to all polymerized units. As the lower limit of the content of modified monomer unit, it is more preferably 0.001 mass %, more preferably 0.010 mass %, and even more preferably 0.050 mass %. As the upper limit of the content of modified monomer unit, it is preferably 5.0 mass %, more preferably 3.0 mass %, more preferably 1.0 mass %, and even more preferably 0.80 mass %, and even more preferably 0.60 mass %, and even more preferably 0.50 mass %, and even more preferably 0.40 mass %, and even more preferably 0.30 mass %, particularly preferably 0.20 mass %.

[0069] In this specification, the modified monomer unit refers to a part of the molecular structure of the TFE-based polymer, and is a portion derived from the modified monomer.

[0070] The content of each polymerized unit can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and fluorescent X-ray analysis depending on the type of monomer.

[0071] The modifying monomer is not particularly limited as long as it can copolymerize with TFE, and examples thereof include perfluoroolefins such as hexafluoropropylene [HFP]; hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride [VDF]; perhaloolefins such as chlorotrifluoroethylene [CTFE]; perfluorovinyl ether; perfluoroallyl ether; (perfluoroalkyl)ethylene, ethylene, etc. The modifying monomer used may be one or two or more.

[0072] The perfluorovinyl ether is not particularly limited, and examples thereof include the following general formula (A):

[0073] CF2=CF-Orf 1 (A)

[0074] (Where Rf 1 In this specification, the "perfluoroorganic group" refers to an organic group in which all hydrogen atoms bonded to carbon atoms are replaced by fluorine atoms. The perfluoroorganic group may have an ether oxygen.

[0075] Examples of the perfluorovinyl ether include: 1 Perfluoro(alkyl vinyl ether) [PAVE] having a perfluoroalkyl group having 1 to 10 carbon atoms. The perfluoroalkyl group preferably has 1 to 5 carbon atoms.

[0076] Examples of the perfluoroalkyl group in PAVE include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group.

[0077] Examples of the perfluorovinyl ether include Rf in the general formula (A) 1 A substance which is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, Rf 1 is the following formula:

[0078] [Chemistry 1]

[0079]

[0080] (wherein m represents 0 or an integer of 1 to 4), a substance having a group represented by 1 is the following formula:

[0081] [Chemistry 2]

[0082]

[0083] (wherein n represents an integer of 1 to 4) and the like.

[0084] The (perfluoroalkyl)ethylene (PFAE) is not particularly limited, and examples thereof include (perfluorobutyl)ethylene (PFBE) and (perfluorohexyl)ethylene.

[0085] Examples of perfluoroallyl ethers include those represented by the general formula (B):

[0086] CF2=CF-CF2-Orf 2 (B)

[0087] (Where Rf 2 represents a perfluorinated organic group).

[0088] The above Rf 2 Preferred are perfluoroalkyl groups having 1 to 10 carbon atoms or perfluoroalkoxyalkyl groups having 1 to 10 carbon atoms. The perfluoroallyl ether is preferably 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, more preferably 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, and even more preferably CF2=CF-CF2-O-CF2CF2CF3.

[0089] The above-mentioned modified monomer is preferably of the following general formula (I):

[0090] CX 1 X 2 =CX 3 X 4 (I)

[0091] (Where, X 1 ~X 3 Each independently represents H or F. X 4 is F, Cl, Rf or O-Rf. Rf is a perfluoroorganic group. )

[0092] In the general formula (I), Rf is preferably a perfluoroalkyl group having 1 to 10 carbon atoms, more preferably a perfluoroalkyl group having 1 to 5 carbon atoms, and still more preferably a perfluoroalkyl group having 1 to 4 carbon atoms.

[0093] From the perspective of being able to mix more evenly with the powder components of the electrochemical device and to obtain a composite sheet with better strength and flexibility, the above-mentioned modifying monomer is preferably at least one selected from the group consisting of CTFE, HFP, perfluoro(methyl vinyl ether) [PMVE], perfluoro(propyl vinyl ether) [PPVE], PFBE and VDF, more preferably at least one selected from the group consisting of CTFE, HFP, PMVE and PPVE, further preferably at least one selected from the group consisting of CTFE, HFP and PPVE, and particularly preferably at least one selected from the group consisting of CTFE and HFP.

[0094] The TFE polymer in the TFE polymer composition of the present invention may have a core-shell structure. Examples of TFE polymers having a core-shell structure include TFE copolymers, preferably modified PTFE, wherein the particles comprise a core of a high molecular weight TFE polymer and a shell of a lower molecular weight TFE polymer or TFE copolymer. Examples of such modified PTFE include the PTFEs described in Japanese Unexamined Patent Application Publication No. 2005-527652.

[0095] From the perspective of being able to mix more uniformly with the powder components of the electrochemical device and to obtain a composite sheet with better strength and flexibility, the TFE-based polymer composition of the present invention preferably contains a TFE copolymer having an extrusion pressure of 75 MPa or less at a compression ratio (RR) of 1000.

[0096] The extrusion pressure at RR1000 is more preferably 70 MPa or less, further preferably 60 MPa or less, still more preferably 50 MPa or less, particularly preferably 40 MPa or less, and is preferably 20 MPa or more, more preferably 30 MPa or more.

[0097] The extrusion pressure at RR1000 is measured by the following method.

[0098] 60 g of TFE-based polymer and 12.3 g of hydrocarbon oil (trade name: Isopar G (registered trademark), manufactured by ExxonMobil) as an extrusion aid were mixed in a polyethylene container for 3 minutes. At room temperature (25±2°C), the mixture was filled into the barrel of the extruder, and a load of 0.47 MPa was applied to the piston inserted into the barrel and maintained for 1 minute. Then, it was extruded from the hole at a punching speed of 20 mm / min. The ratio of the cross-sectional area of ​​the barrel to the cross-sectional area of ​​the hole was 1000. In the second half of the extrusion operation, the value obtained by dividing the load (N) when the pressure reaches a balanced state by the cross-sectional area of ​​the barrel was used as the extrusion pressure (MPa).

[0099] The TFE-based polymer (A) having an endothermic peak in the region (A) is preferably a TFE copolymer having an extrusion pressure of 75 MPa or less at RR1000, and more preferably modified PTFE.

[0100] The TFE polymer (A) having an endothermic peak in region (A) or the TFE polymer having an extrusion pressure of 75 MPa or less at RR1000 preferably has a core-shell structure. This allows for more uniform mixing with the powder components of the electrochemical device and yields a composite sheet with superior strength and flexibility.

[0101] In the core-shell structure, there is no need for a clear boundary between the core and the shell. The TFE-based polymer constituting the core and the TFE-based polymer constituting the shell may be mixed near the boundary between the core and the shell.

[0102] The core in the core-shell structure is preferably a TFE copolymer having polymerized units based on a modified monomer, and more preferably modified PTFE.

[0103] The modifying monomer in the core is preferably at least one selected from the group consisting of fluoro(alkyl vinyl ether), vinyl heterocyclic compounds and fluoroolefins, more preferably at least one selected from the group consisting of fluoro(alkyl vinyl ether) and fluoroolefins, further preferably at least one selected from the group consisting of PAVE, HFP and CTFE, still more preferably at least one selected from the group consisting of PAVE and CTFE, and particularly preferably CTFE.

[0104] Furthermore, as PAVE, perfluoro(propyl vinyl ether) [PPVE] is preferred.

[0105] The shell in the core-shell structure is preferably a TFE copolymer having polymerized units based on a modified monomer and / or a TFE-based copolymer obtained by polymerization using a chain transfer agent, and more preferably modified PTFE.

[0106] The modifying monomer in the shell is preferably at least one selected from the group consisting of fluoro(alkyl vinyl ether) and fluoroolefin, more preferably at least one selected from the group consisting of PAVE, HFP and CTFE, further preferably at least one selected from the group consisting of HFP and CTFE, and even more preferably CTFE.

[0107] The chain transfer agent is not particularly limited as long as it is a substance that reduces the molecular weight of the TFE-based polymer constituting the shell. Examples thereof include substances composed of non-peroxidized organic compounds such as water-soluble alcohols, hydrocarbons, and fluorinated hydrocarbons, water-soluble organic peroxides such as succinyl peroxide [DSP], and persulfates such as ammonium persulfate [APS] and potassium persulfate [KPS].

[0108] The chain transfer agent may be at least one of a non-peroxidized organic compound, a water-soluble organic peroxide, and a persulfate.

[0109] Among the chain transfer agents, one or more non-peroxidized organic compounds, water-soluble organic peroxides, and persulfates can be used.

[0110] The chain transfer agent is preferably composed of at least one selected from the group consisting of water-soluble alcohols having 1 to 4 carbon atoms, hydrocarbons having 1 to 4 carbon atoms, and fluorinated hydrocarbons having 1 to 4 carbon atoms, from the viewpoint of good dispersibility and uniformity in the reaction system. It is more preferably composed of at least one selected from the group consisting of methane, ethane, n-butane, isobutane, methanol, HFC-134a, HFC-32, DSP, APS, and KPS. It is further preferably composed of methanol and / or isobutane, and particularly preferably composed of methanol.

[0111] The TFE-based polymer (A) having an endothermic peak in the region (A) preferably has a standard specific gravity (SSG) of 2.160 or more, more preferably 2.165 or more, and preferably 2.200 or less, more preferably 2.190 or less, further preferably 2.185 or less, still more preferably 2.180 or less, and particularly preferably 2.175 or less.

[0112] The TFE polymer (B) having an endothermic peak in region (B) preferably has an SSG of less than 2.160, more preferably 2.155 or less, and preferably 2.130 or more, more preferably 2.140 or more, and even more preferably 2.145 or more.

[0113] The SSG is measured by the water displacement method according to ASTM D 792 using a sample molded according to ASTM D 4895.

[0114] The mass ratio of the TFE polymer (A) having an endothermic peak in the region (A) to the TFE polymer (B) having an endothermic peak in the region (B) (TFE polymer (A) / TFE polymer (B)) is preferably 1 / 99 or more, more preferably 5 / 95 or more, even more preferably 10 / 90 or more, still more preferably 15 / 85 or more, still more preferably 20 / 80 or more, and particularly preferably 30 / 70 or more, and is preferably 60 / 40 or less, more preferably 55 / 45 or less, and even more preferably 50 / 50 or less.

[0115] In the TFE-based polymer composition of the present invention, the content of the fluorine-based polymer is preferably 90% by mass or more based on the TFE-based polymer composition.

[0116] The fluorine-based polymer may include a TFE-based polymer, and may further include a fluorine-based polymer other than the TFE-based polymer.

[0117] The content of the fluorine-based polymer is the total amount of the TFE-based polymer and the fluorine-based polymer other than the TFE-based polymer.

[0118] Examples of fluorine-based polymers other than TFE-based polymers include vinylidene fluoride (VdF)-based polymers. Examples of VdF-based polymers include VdF-based resins such as polyvinylidene fluoride [PVdF] and VdF / TFE copolymers [VT]; and VdF-based elastomers such as VdF / HFP copolymers, VdF / TFE / HFP copolymers, and VdF / 2,3,3,3-tetrafluoropropylene copolymers.

[0119] The TFE polymer composition of the present invention is preferably composed essentially of the above-mentioned fluorine-based polymer alone, thereby significantly demonstrating the effects of the above-mentioned fluorine-based polymer.

[0120] Substantially consisting of the fluorine-based polymer means that the total amount of the fluorine-based polymer is 95.0% by mass or more based on the fluorine-based polymer composition.

[0121] The fluorinated polymer accounts for preferably 98.0% by mass or more, more preferably 99.0% by mass or more, further preferably 99.5% by mass or more, particularly preferably 99.9% by mass or more, and most preferably 99.95% by mass or more of the fluorinated polymer composition.

[0122] The fluorine-based polymer composition of the present invention is preferably composed solely of the above-mentioned fluorine-based polymer.

[0123] The TFE-based polymer composition of the present invention preferably consists essentially only of the aforementioned TFE-based polymer. This allows for significant benefits from the aforementioned TFE-based polymer. "Essentially consisting only of the TFE-based polymer" means that the content of the aforementioned TFE-based polymer is 95.0% by mass or greater relative to the aforementioned TFE-based polymer composition.

[0124] The content of the TFE polymer is preferably 98.0% by mass or more, more preferably 99.0% by mass or more, further preferably 99.5% by mass or more, particularly preferably 99.9% by mass or more, and most preferably 99.95% by mass or more, based on the TFE polymer composition.

[0125] The TFE-based polymer composition of the present invention is preferably composed only of the above-mentioned TFE-based polymer.

[0126] The TFE-based polymer composition of the present invention preferably consists essentially of only the two or more TFE-based polymers described above. This allows for significant benefits from the two or more TFE-based polymers. "Essentially consisting of only two or more TFE-based polymers" means that the content of the two or more TFE-based polymers is 95.0% by mass or greater relative to the TFE-based polymer composition.

[0127] The content of the two or more TFE polymers is preferably 98.0% by mass or more, more preferably 99.0% by mass or more, further preferably 99.5% by mass or more, particularly preferably 99.9% by mass or more, and most preferably 99.95% by mass or more, based on the TFE polymer composition.

[0128] The TFE-based polymer composition of the present invention is preferably composed only of two or more TFE-based polymers described above.

[0129] The TFE polymer composition of the present invention preferably consists essentially only of the TFE polymer (A) having an endothermic peak in region (A) and the TFE polymer (B) having an endothermic peak in region (B). This allows for significant effects of the TFE polymers (A) and (B). "Consisting essentially only of the TFE polymers (A) and (B)" means that the combined amount of the TFE polymers (A) and (B) relative to the TFE polymer composition is 95.0% by mass or greater.

[0130] The total amount of the TFE polymers (A) and (B) is preferably 98.0% by mass or more, more preferably 99.0% by mass or more, further preferably 99.5% by mass or more, particularly preferably 99.9% by mass or more, and most preferably 99.95% by mass or more, based on the TFE polymer composition.

[0131] The TFE-based polymer composition of the present invention is preferably composed only of the above-mentioned TFE-based polymers (A) and (B).

[0132] The TFE polymer composition of the present invention preferably comprises TFE units and modified monomer units based on a modifying monomer copolymerizable with TFE. Examples of the modifying monomer include those listed above.

[0133] The TFE polymer composition of the present invention may contain 90.0 mass % or more of TFE units and 10.0 mass % or less of modifying monomer units relative to all polymerized units, and preferably contains 99.0 mass % or more of TFE units and 1.0 mass % or less of modifying monomer units.

[0134] The TFE-based polymer composition of the present invention may contain only TFE units and modifying monomer units as polymerized units.

[0135] From the aspect that can be more evenly mixed with the powder component of electrochemical device and can obtain the composite sheet with better strength and flexibility, the content of the modified monomer unit in the TFE-based polymer composition of the present invention is preferably in the range of 0.0001 to 10.0 mass % relative to all polymerized units. As the lower limit of the content of the modified monomer unit, it is more preferably 0.001 mass %, more preferably 0.010 mass %, and even more preferably 0.050 mass %. As the upper limit of the content of the modified monomer unit, it is preferably 5.0 mass %, more preferably 3.0 mass %, more preferably 1.0 mass %, and even more preferably 0.80 mass %, and even more preferably 0.60 mass %, and even more preferably 0.50 mass %, and even more preferably 0.40 mass %, and even more preferably 0.30 mass %, and particularly preferably 0.20 mass %.

[0136] The TFE-based polymer composition of the present invention may contain a conductive auxiliary agent.

[0137] As the conductive auxiliary agent, any known conductive material can be used. Specific examples include metal materials such as copper and nickel, graphite (graphite) such as natural graphite and artificial graphite, carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, needle coke, carbon nanotubes, fullerene, and amorphous carbon such as VGCF. It should be noted that any of these materials can be used alone, or two or more can be used in any combination and ratio.

[0138] When the TFE-based polymer composition of the present invention contains the conductive additive, the content of the conductive additive is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, relative to the TFE-based polymer composition. The upper limit is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less.

[0139] The TFE-based polymer composition of the present invention preferably contains substantially no moisture. Thus, it is possible to suppress gas generation and degradation of electrochemical device characteristics. In addition, it is possible to widely select the electrode active material and solid electrolyte to be combined, which is therefore advantageous in the production process. Substantially containing no moisture means that the moisture content relative to the above-mentioned TFE-based polymer composition is 0.010% by mass or less.

[0140] The water content is preferably 0.005% by mass or less, more preferably 0.003% by mass or less, further preferably 0.002% by mass or less, and still more preferably 0.001% by mass or less.

[0141] The above-mentioned water content is measured by the following method.

[0142] The mass of the TFE polymer composition was measured before and after heating at 150°C for 2 hours, and the mass was calculated according to the following formula: 3 samples were taken, the mass was calculated for each sample, and the average value was calculated and used.

[0143] Water content (mass %) = [(mass of the TFE polymer composition before heating (g)) - (mass of the TFE polymer composition after heating (g))] / (mass of the TFE polymer composition before heating (g)) × 100

[0144] The TFE polymer composition of the present invention preferably contains substantially no fluorinated compounds having a molecular weight of 1000 or less. Substantially containing no fluorinated compounds means that the amount of the fluorinated compounds is 25 ppb by mass or less relative to the TFE polymer composition.

[0145] The amount of the fluorinated compound is preferably 20 ppb by mass or less, more preferably 15 ppb by mass or less, further preferably 10 ppb by mass or less, even more preferably less than 10 ppb by mass, even more preferably less than 1 ppb by mass, even more preferably less than 1 ppb by mass, and particularly preferably less than the lower limit of quantification. The lower limit is not particularly limited, and the amount may be less than the lower limit of quantification.

[0146] The amount of the fluorine-containing compound having a molecular weight of 1000 or less is measured by the following method.

[0147] Weigh 1 g of the sample, add 10 g (12.6 ml) of methanol, and perform ultrasonic treatment for 60 minutes to obtain an extract. The obtained extract is appropriately concentrated by purging with nitrogen, and the fluorine-containing compounds in the concentrated extract are determined by LC / MS / MS. The molecular weight information is selected from the obtained LC / MS spectrum, and it is confirmed that it is consistent with the structural formula of the candidate fluorine-containing compound. Aqueous solutions with more than 5 levels of the standard substance are prepared, and LC / MS analysis of the aqueous solutions with each content is performed. The relationship between the content and the area of ​​the region relative to the content is plotted to draw a calibration curve. Using the above calibration curve, the area of ​​the LC / MS chromatogram of the fluorine-containing compound in the extract is converted into the content of the fluorine-containing compound.

[0148] It should be noted that the lower limit of quantification in this measurement method is 10 mass ppb.

[0149] Examples of the fluorine-containing compound having a molecular weight of 1000 or less include fluorine-containing compounds having a molecular weight of 1000 g / mol or less and having a hydrophilic group. The molecular weight of the fluorine-containing compound is preferably 800 or less, more preferably 500 or less.

[0150] The polymerized particles obtained by polymerization in the presence of a fluorinated surfactant generally contain a fluorinated surfactant in addition to the TFE-based polymer. In this specification, the fluorinated surfactant is used during polymerization.

[0151] The fluorine-containing compound having a molecular weight of 1000 or less may be a compound not added during polymerization, for example, a compound produced as a by-product during polymerization.

[0152] It should be noted that the fluorinated compound having a molecular weight of 1000 or less, when comprising an anionic portion and a cationic portion, refers to a fluorinated compound having an anionic portion with a molecular weight of 1000 or less. The fluorinated compound having a molecular weight of 1000 or less does not include TFE-based polymers.

[0153] As the hydrophilic group, for example, -COOM, -SO2M or -SO3M can be mentioned, and -COOM, -SO3M (wherein M is H, metal atom, NR 1 4. an imidazolium with or without a substituent, a pyridinium with or without a substituent, or a phosphonium with or without a substituent, R 1 H or an organic group. ) or other anionic groups.

[0154] As the above-mentioned fluorine-containing surfactant, a surfactant containing fluorine (anionic fluorine-containing surfactant) whose anionic portion has a molecular weight of 1000 or less can also be used. The above-mentioned "anionic portion" refers to the portion of the above-mentioned fluorine-containing surfactant other than the cation. For example, in F(CF2) n1 In the case of COOM, it is "F(CF2) n1 COO” part.

[0155] Examples of the anionic fluorinated surfactant include the following general formula (N 0 ):

[0156] X n0 -Rf n0 -Y 0 (N 0 )

[0157] (Where, X n0 For H, Cl or and F. Rf n0 It is a chain, branched or cyclic alkylene group having 3 to 20 carbon atoms, in which some or all of the H groups are replaced by F. The alkylene group may contain one or more ether bonds, and some of the H groups may be replaced by Cl. 0 is an anionic group).

[0158] Y 0The anionic group may be -COOM, -SO2M or -SO3M, or may be -COOM or -SO3M.

[0159] M is H, metal atom, NR 1 4. an imidazolium with or without a substituent, a pyridinium with or without a substituent, or a phosphonium with or without a substituent, R 1 is H or an organic group.

[0160] Examples of the metal atom include alkali metals (Group 1) and alkaline earth metals (Group 2), such as Na, K, and Li.

[0161] As R 1 , which can be H or C 1-10 The organic group can be H or C 1-4 The organic group can also be H or C 1-4 of alkyl.

[0162] M can be H, metal atom or NR 1 4, can be H, alkali metal (Group 1), alkaline earth metal (Group 2) or NR 1 4, can also be H, Na, K, Li or NH4.

[0163] The above Rf n0 In the present invention, more than 50% of the H can be replaced by fluorine.

[0164] The fluorinated surfactant may be a single fluorinated surfactant or a mixture of two or more fluorinated surfactants.

[0165] Examples of the fluorinated surfactant include compounds represented by the following formulas: The fluorinated surfactant may be a mixture of these compounds.

[0166] F(CF2)7COOM,

[0167] F(CF2)5COOM,

[0168] H(CF2)6COOM,

[0169] H(CF2)7COOM,

[0170] CF3O(CF2)3OCHFCF2COOM,

[0171] C3F7OCF(CF3)CF2OCF(CF3)COOM,

[0172] CF3CF2CF2OCF(CF3)COOM,

[0173] CF3CF2OCF2CF2OCF2COOM,

[0174] C2F5OCF(CF3)CF2OCF(CF3)COOM,

[0175] CF3OCF(CF3)CF2OCF(CF3)COOM,

[0176] CF2ClCF2CF2OCF(CF3)CF2OCF2COOM,

[0177] CF2ClCF2CF2OCF2CF(CF3)OCF2COOM,

[0178] CF2ClCF(CF3)OCF(CF3)CF2OCF2COOM,

[0179] CF2ClCF(CF3)OCF2CF(CF3)OCF2COOM and

[0180] [Chemistry 3]

[0181]

[0182] (In each formula, M is H, metal atom, NR 1 4. An imidazolium which may have a substituent group, a pyridinium which may have a substituent group, or a phosphonium which may have a substituent group. 1 is H or an organic group. ).

[0183] The TFE-based polymer composition of the present invention preferably contains substantially no fluorinated compounds represented by the above formula.

[0184] In the above formulas, M can be H, a metal atom or NR 1 4, can be H, alkali metal (Group 1), alkaline earth metal (Group 2) or NR 1 4, can also be H, Na, K, Li or NH4.

[0185] R 1 Can be H or C 1-10 The organic group can be H or C 1-4 The organic group can also be H or C 1-4 of alkyl.

[0186] When the TFE-based polymer composition of the present invention does not substantially contain any of the fluorine-containing compounds represented by the above formula, gas generation and degradation of electrochemical device characteristics can be further suppressed.

[0187] The phrase "substantially not containing any of the fluorinated compounds represented by the above formula" means that the amount of the fluorinated compound is 25 ppb by mass or less based on the TFE-based polymer composition.

[0188] The amount of the fluorinated compound is preferably 20 ppb by mass or less, more preferably 15 ppb by mass or less, further preferably 10 ppb by mass or less, even more preferably less than 10 ppb by mass, even more preferably less than 1 ppb by mass, even more preferably less than 1 ppb by mass, and particularly preferably less than the lower limit of quantification. The lower limit is not particularly limited, and the amount may be less than the lower limit of quantification.

[0189] The TFE-based polymer composition of the present invention also preferably does not substantially contain the following general formula:

[0190] [C n-1 F 2n-1 COO - ]M +

[0191] (wherein, n represents an integer of 9 to 14, preferably an integer of 9 to 12, and M + The fluorine-containing compound represented by ( ) represents a cation. Thus, the generation of gas and the degradation of the electrochemical device characteristics can be further suppressed.

[0192] The cation M in the above formula + The M is the same as the M mentioned above.

[0193] The phrase "substantially containing no fluorine-containing compound represented by the above formula" means that the amount of the fluorine-containing compound is 25 ppb by mass or less based on the TFE-based polymer composition.

[0194] The amount of the fluorinated compound is preferably 20 ppb by mass or less, more preferably 15 ppb by mass or less, further preferably 10 ppb by mass or less, even more preferably less than 10 ppb by mass, even more preferably less than 1 ppb by mass, even more preferably less than 1 ppb by mass, and particularly preferably less than the lower limit of quantification. The lower limit is not particularly limited, and the amount may be less than the lower limit of quantification.

[0195] The TFE-based polymer composition of the present invention is preferably stretchable from the viewpoint of being able to be more uniformly mixed with the powder component of the electrochemical device and to obtain a composite sheet having superior strength and flexibility.

[0196] According to the description of Japanese Patent Application Publication No. 2002-201217, 21.7 g of a lubricant (trade name: Isopar H (registered trademark), manufactured by ExxonMobil) is added to 100 g of a TFE-based polymer composition and mixed for 3 minutes. After the mixture is placed in a thermostatic bath at 25°C for 2 hours, the paste is extruded through a hole (diameter 2.5 mm, land length 1.1 cm, lead-in angle 30°) at 25°C under the conditions of a compression ratio (ratio of the cross-sectional area of ​​the die inlet to the cross-sectional area of ​​the die outlet) of 100 and an extrusion speed of 51 cm / min to obtain a strip. The obtained strip is dried at 230°C for 30 minutes to remove the lubricant. The dried strip is cut into appropriate lengths, each end is fixed so that the distance between the chucks is 3.8 cm, and heated to 300°C in an air circulation oven. Next, the chucks are separated at a stretching speed of 1000% / second until the separation distance corresponds to a total stretching of 2400%. "Total stretch" is the increase in length due to stretching relative to the strip length before the tensile test (100%). If the strip does not break during stretching, it is considered stretchable, and if it breaks, it is considered non-stretchable.

[0197] Whether the TFE-based polymer composition is stretchable is preferably determined by the above-mentioned method, but can also be determined by the following method.

[0198] 50 g of a TFE-based polymer composition and 10.25 g of a hydrocarbon oil (trade name: Isopar E (registered trademark), manufactured by ExxonMobil) as an extrusion aid were mixed in a polyethylene container for 3 minutes. At room temperature (25±2°C), the above mixture was filled into the barrel of the extruder, and a load of 0.47 MPa was applied to the piston inserted into the barrel and maintained for 1 minute. Then, it was extruded from the hole at a punching speed of 18 mm / min. The ratio of the cross-sectional area of ​​the barrel to the cross-sectional area of ​​the hole was 100. The obtained strip was dried at 230°C for 30 minutes to remove the lubricant. The dried strip was cut into appropriate lengths and placed in a furnace heated to 300°C. In the furnace, it was stretched to 25 times the length of the strip before the tensile test at a stretching speed of 100% / second. If it does not break during stretching, it is judged to be stretchable, and if it breaks, it is judged to be non-stretchable.

[0199] The TFE-based polymer composition of the present invention preferably has non-melt secondary processability. This non-melt secondary processability refers to the property that the melt flow rate cannot be measured at temperatures above the melting point according to ASTM D-1238 and D-2116. In other words, it refers to the property of not being able to flow easily even in the melting temperature range.

[0200] From the perspective of being able to mix more evenly with the powder components of the electrochemical device and to obtain a composite sheet with better strength and flexibility, the standard specific gravity (SSG) of the TFE-based polymer composition of the present invention is preferably 2.200 or less, more preferably 2.190 or less, further preferably 2.180 or less, and even more preferably 2.175 or less. In addition, it is preferably 2.130 or more, more preferably 2.140 or more, and even more preferably 2.150 or more.

[0201] The SSG is measured by the water displacement method according to ASTM D 792 using a sample molded according to ASTM D 4895.

[0202] From the perspective of being able to mix more evenly with the powder components of the electrochemical device and to obtain a composite sheet with better strength and flexibility, the extrusion pressure of the TFE-based polymer composition of the present invention at a compression ratio (RR) of 200 is preferably 10 MPa or more, more preferably 15 MPa or more, and is preferably 50 MPa or less, more preferably 40 MPa or less, and even more preferably 35 MPa or less.

[0203] The extrusion pressure at RR200 is measured by the following method.

[0204] 60 g of a TFE-based polymer composition and 12.3 g of a hydrocarbon oil (trade name: Isopar G (registered trademark), manufactured by ExxonMobil) as an extrusion aid were mixed in a polyethylene container for 3 minutes. At room temperature (25±2°C), the mixture was filled into the barrel of the extruder, and a load of 0.47 MPa was applied to the piston inserted into the barrel and maintained for 1 minute. Next, the extruder was extruded from the hole at a punching speed of 20 mm / min. The ratio of the cross-sectional area of ​​the barrel to the cross-sectional area of ​​the hole was 200. In the second half of the extrusion operation, the value obtained by dividing the load (N) when the pressure reaches a balanced state by the cross-sectional area of ​​the barrel was used as the extrusion pressure (MPa).

[0205] The form of the TFE-based polymer composition of the present invention is not limited, but is preferably a powder from the viewpoint of being able to be mixed with an electrode active material and a solid electrolyte without using a large amount of a dispersion medium.

[0206] It should be noted that the TFE-based polymer composition may be in a form other than powder, for example, a dispersion.

[0207] From the perspective of excellent powder flowability and excellent uniformity of the strength of the composite sheet, the TFE-based polymer composition of the present invention preferably has an average aspect ratio of 2.5 or less, more preferably 2.0 or less, even more preferably 1.8 or less, and even more preferably 1.5 or less in powder form. Furthermore, it is preferably 1.0 or greater, and more preferably 1.1 or greater. In this case, the TFE-based polymer composition may be in powder form.

[0208] The average aspect ratio of the powder is calculated as follows: the powder is spread thinly on a black paper in the air without applying shear to the powder, the spread powder is observed using a microscope, and the average value of the ratio of the major axis to the minor axis of more than 100 randomly selected powders is used to calculate the average aspect ratio.

[0209] The average secondary particle size of the TFE-based polymer composition of the present invention can be 350 μm or more, preferably 400 μm or more, more preferably 450 μm or more, and even more preferably 500 μm or more. In addition, it is preferably 1000 μm or less, more preferably 900 μm or less, even more preferably 800 μm or less, and even more preferably 700 μm or less.

[0210] The above-mentioned average secondary particle size is measured in accordance with JIS K 6891.

[0211] From the perspective of excellent handleability, the apparent density of the TFE polymer composition of the present invention is preferably 0.40 g / ml or higher, more preferably 0.43 g / ml or higher, and even more preferably 0.45 g / ml or higher. The upper limit is not particularly limited and may be 0.70 g / ml.

[0212] The above apparent density is measured in accordance with JIS K 6892.

[0213] The TFE polymer composition of the present invention can be produced by mixing the TFE polymer (A) having an endothermic peak in region (A) and the TFE polymer (B) having an endothermic peak in region (B). The mixing method is not limited; the TFE polymers (A) and (B) may be mixed in the form of a powder, an aqueous dispersion, or a combination of an aqueous dispersion and a powder. For more uniform mixing, mixing in the form of an aqueous dispersion is preferred.

[0214] The TFE-based polymer composition of the present invention can be suitably produced by a production method comprising the following steps: for example, step (A) of mixing an aqueous dispersion of the TFE-based polymer (A) having an endothermic peak in region (A) and an aqueous dispersion of the TFE-based polymer (B) having an endothermic peak in region (B), step (B) of precipitating the mixed aqueous dispersion to obtain a wet powder, and step (C) of drying the wet powder.

[0215] The aqueous dispersion of the TFE-based polymer (B) in step (A) can be produced by, for example, emulsion polymerization.

[0216] The emulsion polymerization can be carried out by a known method. For example, in the presence of an anionic fluorinated surfactant and a polymerization initiator, emulsion polymerization of monomers (TFE and, if necessary, a modifying monomer) required to form the TFE-based polymer is carried out in an aqueous medium to obtain an aqueous dispersion of particles (primary particles) containing the TFE-based polymer. In the emulsion polymerization, a chain transfer agent, a buffer, a pH adjuster, a stabilizing agent, a dispersion stabilizer, a radical scavenger, etc. may be used as needed.

[0217] The aqueous dispersion may contain at least one of the fluorine-containing compounds described above.

[0218] The emulsion polymerization can be carried out in an aqueous medium in the presence of an anionic fluorinated surfactant and a polymerization initiator, for example.

[0219] The emulsion polymerization can be carried out by placing an aqueous medium, the anionic fluorinated surfactant, monomers, and other additives as needed into a polymerization reactor, stirring the contents of the reactor while maintaining the reactor at a predetermined polymerization temperature, and then adding a predetermined amount of polymerization initiator to initiate the polymerization reaction. After the polymerization reaction has begun, additional monomers, polymerization initiators, chain transfer agents, and the surfactant may be added depending on the intended purpose.

[0220] The polymerization initiator is not particularly limited as long as it can generate free radicals within the polymerization temperature range, and known oil-soluble and / or water-soluble polymerization initiators can be used. Furthermore, the polymerization can be initiated in a redox manner in combination with a reducing agent or the like. The concentration of the polymerization initiator is appropriately determined based on the type of monomer, the molecular weight of the target TFE-based polymer, and the reaction rate.

[0221] As the polymerization initiator, an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator can be used.

[0222] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, and for example, the following peroxides may be cited as representative substances: dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and di-sec-butyl peroxydicarbonate; peroxyesters such as tert-butyl peroxyisobutyrate and tert-butyl peroxypivalate; dialkyl peroxides such as di-tert-butyl peroxide; and di(ω-hydro-dodecafluoroheptanoyl) peroxide, di(ω-hydro-tetradecafluoroheptanoyl) peroxide, di(ω-hydro-hexafluorononanoyl) peroxide, di(perfluorobutyryl) peroxide, di(perfluorovaleranoyl) peroxide, di(perfluorohexanoyl) peroxide, di(perfluoroheptanoyl) peroxide, di(perfluorooctanoyl) peroxide. peroxide, bis(perfluorononanoyl) peroxide, bis(ω-chloro-hexafluorobutyryl) peroxide, bis(ω-chloro-decafluorohexanoyl) peroxide, bis(ω-chloro-tetrafluorooctanoyl) peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexafluorononanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydro-dodecafluoroheptanoyl-perfluorobutyryl-peroxide, bis(dichloropentafluorobutyryl) peroxide, bis(trichlorooctafluorohexanoyl) peroxide, bis(tetrachloroundecanoyl) peroxide, bis(pentachlorotetrafluorodecanoyl) peroxide, bis(undecachlorotriadecanoyl) peroxide, etc.

[0223] The water-soluble free radical polymerization initiator may be a known water-soluble peroxide, such as ammonium, potassium, or sodium salts of persulfuric acid, perboric acid, perchloric acid, perphosphoric acid, or percarbonic acid, tert-butyl permaleate, tert-butyl hydroperoxide, or disuccinic acid peroxide. Among these, ammonium persulfate and disuccinic acid peroxide are preferred. A reducing agent such as a sulfite or sulfite salt may also be included, and its amount may be 0.1 to 20 times that of the peroxide.

[0224] The amount of water-soluble radical polymerization initiator added is not particularly limited; it may be added all at once, sequentially, or continuously in the initial stage of polymerization in an amount sufficient to prevent a significant decrease in the polymerization rate (e.g., a concentration of several ppm relative to water). The upper limit is a range within which the heat of polymerization can be removed from the apparatus surface while simultaneously raising the reaction temperature. A more preferred upper limit is a range within which the heat of polymerization can be removed from the apparatus surface.

[0225] From the perspective of easily obtaining the above-mentioned physical properties, the amount of polymerization initiator added is preferably an amount equivalent to 0.1 ppm or more, more preferably an amount equivalent to 1.0 ppm or more, relative to the aqueous medium. In addition, it is preferably an amount equivalent to 100 ppm or less, more preferably an amount equivalent to 10 ppm or less.

[0226] For example, when polymerization is carried out at a low temperature of 30°C or lower, it is preferred to use a redox initiator that is a combination of an oxidizing agent and a reducing agent as a polymerization initiator. Examples of the oxidizing agent include persulfates, organic peroxides, potassium permanganate, manganese triacetate, ceric ammonium nitrate, and bromates. Examples of the reducing agent include sulfites, bisulfites, bromates, diimides, and oxalic acid. Examples of the persulfate include ammonium persulfate and potassium persulfate. Examples of the sulfite include sodium sulfite and ammonium sulfite. In order to increase the decomposition rate of the initiator, it is also preferred to add a copper salt or an iron salt to the combination of the redox initiator. Examples of the copper salt include copper (II) sulfate, and examples of the iron salt include iron (II) sulfate.

[0227] As the redox initiator, preferably, the oxidizing agent is permanganic acid or a salt thereof, persulfate, manganese triacetate, cerium (IV) salt, or bromic acid or a salt thereof, and the reducing agent is dicarboxylic acid or a salt thereof, or diimine.

[0228] More preferably, the oxidizing agent is permanganic acid or a salt thereof, persulfate, or bromic acid or a salt thereof, and the reducing agent is dicarboxylic acid or a salt thereof.

[0229] Examples of the redox initiator include combinations of potassium permanganate / oxalic acid, potassium permanganate / ammonium oxalate, manganese triacetate / oxalic acid, manganese triacetate / ammonium oxalate, cerium ammonium nitrate / oxalic acid, and cerium ammonium nitrate / ammonium oxalate.

[0230] When a redox initiator is used, either the oxidizing agent or the reducing agent can be pre-charged into the polymerization vessel, followed by continuous or intermittent addition of the other to initiate polymerization. For example, when potassium permanganate / ammonium oxalate is used, it is preferred to charge ammonium oxalate into the polymerization vessel and continuously add potassium permanganate thereto.

[0231] In addition, in the present specification, when a redox initiator is described as "potassium permanganate / ammonium oxalate", it means a combination of potassium permanganate and ammonium oxalate. The same applies to other compounds.

[0232] The redox initiator is particularly preferably a combination of an oxidizing agent which is a salt and a reducing agent which is a salt.

[0233] For example, the oxidizing agent as the salt is more preferably at least one selected from the group consisting of persulfate, permanganate, cerium (IV) salt, and bromate, further preferably permanganate, and particularly preferably potassium permanganate.

[0234] The reducing agent for the salt is more preferably at least one selected from the group consisting of oxalates, malonates, succinates, glutarates, and bromates, further preferably oxalates, and particularly preferably ammonium oxalate.

[0235] Specifically, the redox initiator is preferably at least one selected from the group consisting of potassium permanganate / oxalic acid, potassium permanganate / ammonium oxalate, potassium bromate / ammonium sulfite, manganese triacetate / ammonium oxalate, and ceric ammonium nitrate / ammonium oxalate; more preferably, it is at least one selected from the group consisting of potassium permanganate / oxalic acid, potassium permanganate / ammonium oxalate, potassium bromate / ammonium sulfite, and ceric ammonium nitrate / ammonium oxalate; and even more preferably, it is potassium permanganate / oxalic acid.

[0236] When a redox initiator is used, the oxidizing agent and the reducing agent may be added at once at the beginning of the polymerization, the reducing agent may be added at once and the oxidizing agent may be added continuously at the beginning of the polymerization, the oxidizing agent may be added at once and the reducing agent may be added continuously at the beginning of the polymerization, or both the oxidizing agent and the reducing agent may be added continuously.

[0237] When one of the above-mentioned redox polymerization initiators is added at the initial stage of polymerization and the remaining one is added continuously, it is preferred to slow down the rate of addition, and more preferably to stop the addition during polymerization, from the perspective of obtaining a TFE-based polymer with low SSG. The addition is preferably stopped before 20% to 40% by mass of the total TFE consumed in the polymerization reaction has been consumed.

[0238] When a redox initiator is used as the polymerization initiator, the amount of the oxidizing agent added is preferably 0.1 ppm or more, more preferably 0.3 ppm or more, even more preferably 0.5 ppm or more, still more preferably 1 ppm or more, particularly preferably 5 ppm or more, and particularly preferably 10 ppm or more, relative to the aqueous medium, and is preferably 10,000 ppm or less, more preferably 1,000 ppm or less, even more preferably 100 ppm or less, and even more preferably 10 ppm or less. The amount of the reducing agent added is preferably 0.1 ppm or more, more preferably 1.0 ppm or more, even more preferably 3 ppm or more, even more preferably 5 ppm or more, and particularly preferably 10 ppm or more, and is preferably 10,000 ppm or less, more preferably 1,000 ppm or less, even more preferably 100 ppm or less, and even more preferably 10 ppm or less.

[0239] When a redox initiator is used in the emulsion polymerization, the polymerization temperature is preferably 100°C or lower, more preferably 95°C or lower, and even more preferably 90°C or lower. It is preferably 10°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher.

[0240] As the polymerization initiator, a water-soluble radical polymerization initiator and a redox initiator are preferred from the viewpoint of easily obtaining the above-mentioned physical properties.

[0241] The aqueous medium is a reaction medium for polymerization and is a liquid containing water. The aqueous medium is not particularly limited as long as it contains water and may contain water and a non-fluorinated organic solvent such as an alcohol, ether, or ketone and / or a fluorinated organic solvent having a boiling point of 40°C or less.

[0242] In the emulsion polymerization, a nucleating agent, a chain transfer agent, a buffer, a pH adjuster, a stabilization aid, a dispersion stabilizer, a radical scavenger, a decomposition agent of the polymerization initiator, a dicarboxylic acid, and the like may be used as needed.

[0243] In order to adjust the particle size, the emulsion polymerization is preferably carried out with the addition of a nucleating agent. The nucleating agent is preferably added before the start of the polymerization reaction.

[0244] As the nucleating agent, a known nucleating agent can be used. For example, at least one selected from the group consisting of fluoropolyethers, nonionic surfactants, and chain transfer agents is preferred, and a nonionic surfactant is more preferred.

[0245] Examples of the fluoropolyether include perfluoropolyether (PFPE) acid and salts thereof.

[0246] The perfluoropolyether (PFPE) acid or salt thereof can have any chain structure in which oxygen atoms in the main chain of the molecule are separated by saturated fluorocarbon groups having 1 to 3 carbon atoms. Furthermore, two or more fluorocarbon groups can be present in the molecule. A typical structure has a repeating unit represented by the following formula.

[0247] (-CFCF3-CF2-O-) n

[0248] (-CF2-CF2-CF2-O-) n

[0249] (-CF2-CF2-O-)n-(-CF2-O-) m

[0250] (-CF2-CFCF3-O-)n-(-CF2-O-) m

[0251] These structures are described by Kasai in J. Appl. Polymer Sci. 57, 797 (1995). As disclosed in this document, the PFPE acid or salt thereof may have a carboxylic acid group or its salt at one or both termini. Furthermore, the PFPE acid or salt thereof may have a sulfonic acid, phosphonic acid group or its salt at one or both termini. Furthermore, the PFPE acid or salt thereof may have different groups at each terminus. In monofunctional PFPE, the other terminus of the molecule is typically perfluorinated and may also contain a hydrogen or chlorine atom. The PFPE acid or salt thereof has at least two ether oxygen groups, preferably at least four, and more preferably at least six. Preferably, at least one of the fluorocarbon groups interrupting the ether oxygen groups, and more preferably at least two of the fluorocarbon groups, has 2 or 3 carbon atoms. Even more preferably, at least 50% of the fluorocarbon groups interrupting the ether oxygen groups have 2 or 3 carbon atoms. Furthermore, the PFPE acid or salt thereof preferably has a total of at least 15 carbon atoms. For example, the preferred minimum value of n or n+m in the repeating unit structure is at least 5. Two or more PFPE acids or salts thereof having an acid group at one or both ends can be used in the production method of the present invention. The PFPE acid or salt thereof preferably has a number average molecular weight of less than 6000 g / mol.

[0252] From the perspective of further increasing the molecular weight of the TFE-based polymer and improving the strength of the composite sheet, the emulsion polymerization is preferably carried out by adding a free radical scavenger or a decomposition agent for the polymerization initiator. The free radical scavenger or decomposition agent for the polymerization initiator is preferably added after the polymerization reaction begins, preferably before 10% or more, preferably 20% or more, of the total TFE consumed in the polymerization reaction is polymerized, and preferably before 50% or less, preferably 40% or less, of the total TFE consumed in the polymerization reaction is polymerized. In the case of performing the pressure relief and re-increasing described below, the free radical scavenger or decomposition agent for the polymerization initiator is preferably added thereafter.

[0253] As the above-mentioned free radical scavenger, a compound that adds to free radicals in the polymerization system or has no reinitiation ability after chain transfer is used. Specifically, a compound that readily undergoes a chain transfer reaction with a primary free radical or a propagating free radical to subsequently generate a stable free radical that does not react with the monomer, or readily undergoes an addition reaction with a primary free radical or a propagating free radical to generate a stable free radical is used.

[0254] The activity of substances generally referred to as chain transfer agents is characterized by a chain transfer constant and a reinitiation efficiency. Among chain transfer agents, substances having a reinitiation efficiency of substantially 0% are referred to as free radical scavengers.

[0255] The radical scavenger can be, for example, a compound having a chain transfer constant with TFE at the polymerization temperature greater than the polymerization rate constant and having a substantially zero% reinitiation efficiency. "Substantially zero% reinitiation efficiency" means that the generated free radicals stabilize the radical scavenger.

[0256] Preferred are compounds having a chain transfer constant (Cs) with TFE at the polymerization temperature (=chain transfer rate constant (kc) / polymerization rate constant (kp)) greater than 0.1, and the chain transfer constant (Cs) of the above-mentioned compound is more preferably 0.5 or greater, further preferably 1.0 or greater, still more preferably 5.0 or greater, and particularly preferably 10 or greater.

[0257] The radical scavenger is preferably at least one selected from the group consisting of aromatic hydroxy compounds, aromatic amines, N,N-diethylhydroxylamine, quinone compounds, terpenes, thiocyanates, and copper chloride (CuCl 2 ).

[0258] Examples of the aromatic hydroxy compound include unsubstituted phenol, polyphenol, salicylic acid, m-salicylic acid, p-salicylic acid, gallic acid, and naphthol.

[0259] Examples of the unsubstituted phenol include o-nitrophenol, m-nitrophenol, p-nitrophenol, o-aminophenol, m-aminophenol, p-aminophenol, and p-nitrosophenol. Examples of the polyphenol include catechol, resorcinol, hydroquinone, pyrogallol, pyrogallol, and naphthol resorcinol.

[0260] Examples of the aromatic amines include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, and benzidine.

[0261] Examples of the quinone compound include o-benzoquinone, m-benzoquinone, p-benzoquinone, 1,4-naphthoquinone, and alizarin.

[0262] Examples of the thiocyanate include ammonium thiocyanate (NH4SCN), potassium thiocyanate (KSCN), and sodium thiocyanate (NaSCN).

[0263] Among these, the radical scavenger is preferably an aromatic hydroxy compound, more preferably unsubstituted phenol or polyphenol, and still more preferably hydroquinone.

[0264] From the perspective of appropriately reducing the standard specific gravity, the amount of the radical scavenger added is preferably an amount equivalent to 3% to 500% (on a molar basis) of the polymerization initiator concentration. A more preferred lower limit is 10% (on a molar basis), and even more preferably 15% (on a molar basis). A more preferred upper limit is 400% (on a molar basis), and even more preferably 300% (on a molar basis).

[0265] The decomposition agent for the polymerization initiator may be any compound capable of decomposing the polymerization initiator used, and is preferably at least one selected from the group consisting of sulfites, bisulfites, bromates, diimines, diimide salts, oxalic acid, oxalates, copper salts, and iron salts. Examples of the sulfite include sodium sulfite and ammonium sulfite. Examples of the copper salt include copper (II) sulfate, and examples of the iron salt include iron (II) sulfate.

[0266] From the perspective of appropriately reducing the standard specific gravity, the amount of the decomposition agent added is preferably an amount equivalent to 3% to 500% (on a molar basis) of the initiator concentration. A more preferred lower limit is 10% (on a molar basis), and even more preferably 15% (on a molar basis). A more preferred upper limit is 400% (on a molar basis), and even more preferably 300% (on a molar basis).

[0267] To reduce the amount of coagulum produced during polymerization, the emulsion polymerization can be carried out in the presence of a dicarboxylic acid at a concentration of 5 ppm to 500 ppm, preferably 10 ppm to 200 ppm, relative to the aqueous medium. If the dicarboxylic acid concentration is too low relative to the aqueous medium, a sufficient effect may not be achieved. If it is too high, chain transfer reactions may occur, resulting in a low molecular weight polymer. The dicarboxylic acid concentration is more preferably 150 ppm or less. The dicarboxylic acid can be added before or during the polymerization reaction.

[0268] The dicarboxylic acid is preferably a dicarboxylic acid represented by the general formula: HOOCRCOOH (wherein R represents an alkylene group having 1 to 5 carbon atoms), more preferably succinic acid, malonic acid, glutaric acid, adipic acid, or pimelic acid, and still more preferably succinic acid.

[0269] In the emulsion polymerization described above, the polymerization temperature and polymerization pressure are appropriately determined depending on the type of monomer used, the molecular weight of the target TFE-based polymer, and the reaction rate. Generally, the polymerization temperature is 5°C to 150°C, preferably 10°C or higher, more preferably 30°C or higher, and even more preferably 50°C or higher. Furthermore, it is more preferably 120°C or lower, and even more preferably 100°C or lower.

[0270] The polymerization pressure is 0.05 MPaG to 10 MPaG. The polymerization pressure is more preferably 0.3 MPaG or higher, and even more preferably 0.5 MPaG or higher. The polymerization pressure is more preferably 5.0 MPaG or lower, and even more preferably 3.0 MPaG or lower.

[0271] When VDF is used as a modifying monomer, in the emulsion polymerization, the VDF concentration in the gas within the reactor at the start of polymerization (when the initiator is added) is preferably set to 0.001 mol% or more, more preferably 0.01 mol% or more, in order to easily achieve the above-mentioned physical properties. The above-mentioned concentration may also be 15 mol% or less, preferably 6.0 mol% or less, more preferably 5.0 mol% or less, still more preferably 3.0 mol% or less, and particularly preferably 1.0 mol% or less. The above-mentioned VDF concentration may be maintained until the end of the polymerization reaction, or the pressure may be released midway. VDF is preferably added all at once before the start of polymerization, but portions may also be added continuously or intermittently after the start of polymerization.

[0272] When using VDF as a modifying monomer, it is preferred that the pressure not be released during the emulsion polymerization after VDF is added to the polymerization vessel until the polymerization is complete. This allows the VDF to remain in the system until the end of the polymerization, further enhancing the strength of the resulting TFE-based polymer composite sheet.

[0273] When using HFP as a modifying monomer, in the emulsion polymerization, from the perspective of easily obtaining the above-mentioned physical properties, the HFP concentration in the gas in the reactor at the start of polymerization (when adding initiator) is preferably set to 0.01 mol% to 3.0 mol%. Furthermore, the HFP concentration in the gas in the reactor at the moment when 40% by mass of all TFE consumed in the polymerization reaction is polymerized is preferably greater than 0 mol% and less than 0.2 mol%. The above-mentioned HFP concentration is preferably maintained thereafter until the polymerization reaction is completed. HFP can be added in a single dose before the start of polymerization, or a portion can be added before the start of polymerization and added continuously or intermittently after the start of polymerization. By allowing HFP to remain until the end of the polymerization reaction, although the strength of the composite sheet using the resulting TFE-based polymer is high, the extrusion pressure is reduced.

[0274] When HFP is used as the modifying monomer, in the emulsion polymerization described above, from the perspective of further improving the strength of the composite sheet using the resulting TFE-based polymer, it is preferred to release the pressure before 5% to 40% by mass of the total TFE consumed in the polymerization reaction is polymerized, and then re-increase the pressure using only TFE.

[0275] The pressure reduction is preferably performed so that the pressure in the reactor becomes 0.2 MPaG or less, more preferably 0.1 MPaG or less, and even more preferably 0.05 MPaG or less. Furthermore, it is preferably performed so that the pressure becomes 0.0 MPaG or more.

[0276] The pressure reduction and re-increasing can be repeated multiple times. The pressure reduction can be performed using a vacuum pump to a reduced pressure.

[0277] When CTFE is used as a modifying monomer, in the emulsion polymerization, from the perspective of easily obtaining the above-mentioned physical properties, the CTFE concentration in the gas in the reactor at the start of polymerization (when the initiator is added) is preferably set to 0.001 mol% or more, more preferably 0.01 mol% or more. In addition, the above concentration is preferably set to 3.0 mol% or less, more preferably 1.0 mol% or less. The above CTFE concentration can be maintained until the end of the polymerization reaction, or pressure relief can be implemented midway. CTFE is preferably added all at once before the start of polymerization, but a portion can also be added continuously or intermittently after the start of polymerization.

[0278] When using CTFE as the modifying monomer, it is preferred that the pressure not be released during the emulsion polymerization after the CTFE is added to the polymerization vessel until the polymerization is complete. This allows the CTFE to remain in the system until the end of the polymerization, further enhancing the strength of the resulting TFE-based polymer composite sheet.

[0279] The aqueous dispersion of the TFE-based polymer (A) in step (A) can be suitably produced, for example, by carrying out, in the step of emulsion polymerization of TFE and a modifying monomer, a step (1a) of adding a modifying monomer to a reaction system at the initial stage of the polymerization reaction to carry out the polymerization reaction, and a step (2a) of introducing a chain transfer agent and / or a modifying monomer into the reaction system after the step (1a).

[0280] This production method can easily produce an aqueous dispersion of a TFE copolymer having an extrusion pressure of 75 MPa or less at RR1000 as described above. Furthermore, a TFE copolymer having a core-shell structure can be easily produced.

[0281] Examples of the modifying monomer in step (1a) include fluoro(alkyl vinyl ethers) such as perfluoro(alkyl vinyl ether) [PAVE]; vinyl heterocyclics such as perfluoro-2,2-dimethyl-1,3-dioxole [PDD]; and fluoroolefins such as hexafluoropropylene [HFP] and chlorotrifluoroethylene [CTFE]. One or more of these can be used.

[0282] Among them, at least one selected from the group consisting of fluoro(alkyl vinyl ether) and fluoroolefin is preferred, at least one selected from the group consisting of PAVE, HFP and CTFE is more preferred, at least one selected from the group consisting of PAVE and CTFE is further preferred, and CTFE is even more preferred.

[0283] As the modifying monomer in step (1a), it is also preferred to use PAVE and HFP in combination.

[0284] As PAVE, perfluoro(propyl vinyl ether) [PPVE] is preferred.

[0285] The chain transfer agent in step (2a) is not particularly limited as long as it is a substance that reduces the molecular weight of the TFE-based polymer constituting the shell of the core-shell structure. Examples thereof include substances composed of non-peroxidized organic compounds such as water-soluble alcohols, hydrocarbons, and fluorinated hydrocarbons, water-soluble organic peroxides such as succinyl peroxide [DSP], and persulfates such as ammonium persulfate [APS] and potassium persulfate [KPS].

[0286] The chain transfer agent may be at least one of a non-peroxidized organic compound, a water-soluble organic peroxide, and a persulfate.

[0287] Among the chain transfer agents, one or more of each of non-peroxidized organic compounds, water-soluble organic peroxides, and persulfates can be used.

[0288] The chain transfer agent is preferably composed of at least one member selected from the group consisting of water-soluble alcohols having 1 to 4 carbon atoms, hydrocarbons having 1 to 4 carbon atoms, and fluorinated hydrocarbons having 1 to 4 carbon atoms, from the viewpoint of good dispersibility and uniformity in the reaction system. It is more preferably composed of at least one member selected from the group consisting of methane, ethane, n-butane, isobutane, methanol, HFC-134a, HFC-32, DSP, APS, and KPS. It is further preferably composed of methanol and / or isobutane, and particularly preferably composed of methanol.

[0289] The modifying monomer in step (2a) is preferably at least one selected from the group consisting of the above-mentioned fluoro(alkyl vinyl ethers) and fluoroolefins, more preferably at least one selected from the group consisting of PAVE, HFP and CTFE, further preferably at least one selected from the group consisting of HFP and CTFE, and even more preferably CTFE.

[0290] In step (2a), it is also preferred to use the chain transfer agent and the modified monomer in combination.

[0291] When CTFE is used as the modifying monomer in step (1a), it is preferred to use CTFE as the modifying monomer in step (2a).

[0292] When PAVE (and HFP) is used as the modifying monomer in step (1a), methanol (and HFP as the modifying monomer) is preferably used as the chain transfer agent in step (2a).

[0293] In the step (1a), the polymerization reaction is preferably carried out until the conversion of TFE used in the entire emulsion polymerization step including the steps (1a) and (2a) reaches 80% or more, preferably 80 to 97%, more preferably 85 to 95%.

[0294] In this specification, the "conversion rate" is the ratio of the amount of TFE consumed in the polymerization from the start of polymerization to a certain point in the middle of the polymerization to the amount of TFE equivalent to the target amount of TFE units.

[0295] In the above steps (1a) and (2a), the reaction conditions can be appropriately set according to the type of the modifier used, the composition and yield of the target TFE-based polymer, and the like.

[0296] The emulsion polymerization can be carried out in an aqueous medium in the presence of an anionic fluorinated surfactant and a polymerization initiator, and a dispersion stabilizer or the like can be used as needed.

[0297] The anionic fluorinated surfactant may be present in an amount of 0.02 to 0.3% by mass of the aqueous medium.

[0298] As the polymerization initiator, for example, persulfates such as ammonium persulfate [APS] and water-soluble organic peroxides such as succinyl peroxide [DSP] can be used. These polymerization initiators can be used alone or in combination of two or more. Among them, APS and DSP are preferred because they also function as the chain transfer agents described above.

[0299] The emulsion polymerization is preferably carried out using a polymerization initiator in an amount of 0.0001 to 0.02 parts by mass relative to 100 parts by mass of the aqueous medium.

[0300] As the aqueous medium, those described above can be used.

[0301] The emulsion polymerization can be carried out at a polymerization temperature of 10 to 95°C. When a persulfate or a water-soluble organic peroxide is used as a polymerization initiator, the polymerization is preferably carried out at a temperature of 60 to 90°C.

[0302] The emulsion polymerization can be carried out usually at 0.5 to 3.9 MPaG, preferably 0.6 to 3 MPaG.

[0303] Furthermore, the emulsion polymerization can be carried out at a pressure of 0.5 MPaG or less in the initial stage of polymerization, particularly before the conversion rate of TFE reaches a range of 15% or less of the total, and thereafter by maintaining the pressure at a pressure greater than 0.5 MPaG. Alternatively, the polymerization can be carried out by reducing the reaction pressure to, for example, 0.1 MPaG or less during the formation of the core portion, and then supplying TFE again to carry out the reaction at a predetermined pressure.

[0304] The mixing in step (A) can be performed by a known method.

[0305] The precipitation in step (B) can be performed by a known method.

[0306] In step (C), the drying is typically performed using vacuum, high-frequency, hot air, or other methods while maintaining the wet powder in a non-flowing state, preferably a static state. Friction between powders, especially at high temperatures, often adversely affects fine powders of TFE-based polymers. This is because particles composed of such TFE-based polymers readily fibrillate even when subjected to small shear forces, losing their originally stable particle structure.

[0307] In step (C), the wet powder obtained in step (B) is preferably placed in a container having an air-permeable bottom and / or side surfaces and heat-treated at a temperature of 130°C to 300°C for 2 hours or longer. By performing the heat treatment under such extremely limited conditions, the fluorinated compound having a molecular weight of 1000 or less can be efficiently removed along with water, and the contents of the fluorinated compound and water can be reduced to within the above-mentioned ranges.

[0308] From the perspective of being able to more efficiently remove moisture and fluorine-containing compounds, the temperature of the heat treatment in step (C) is preferably 140°C or higher, more preferably 150°C or higher, further preferably 160°C or higher, further more preferably 180°C or higher, further preferably 200°C or higher, and particularly preferably 220°C or higher. In addition, it is preferably 280°C or lower, more preferably 250°C or lower.

[0309] From the aspect of being able to remove water and fluorine-containing compounds more efficiently, the time of the heat treatment in step (C) is preferably 5 hours or more, more preferably 10 hours or more, and further preferably 15 hours or more. The upper limit is not particularly limited, for example, it is preferably 100 hours, more preferably 50 hours, and further preferably 30 hours.

[0310] From the perspective of more efficiently removing water and fluorinated compounds, the wind speed in step (C) is preferably 0.01 m / s or higher, more preferably 0.03 m / s or higher, even more preferably 0.05 m / s or higher, and even more preferably 0.1 m / s or higher. Furthermore, from the perspective of suppressing powder scattering, the wind speed is preferably 50 m / s or lower, more preferably 30 m / s or lower, and even more preferably 10 m / s or lower.

[0311] The heat treatment in step (C) can be carried out using an electric furnace or a steam furnace. For example, a parallel flow box-type electric furnace, a ventilated box-type electric furnace, a ventilated conveyor type electric furnace, a belt-type electric furnace, a radiant conveyor type electric furnace, a fluidized bed electric furnace, a vacuum electric furnace, a stirring electric furnace, an airflow type electric furnace, a hot air circulation type electric furnace or an electric furnace corresponding to the above (the electric furnace in the device name of each of the above-mentioned electric furnaces is replaced with a device for a steam furnace) can be used. From the aspect of being able to more efficiently remove moisture and fluorine-containing compounds, preferably a parallel flow box-type electric furnace, a ventilated box-type electric furnace, a ventilated conveyor type electric furnace, a belt-type electric furnace, a fluidized bed electric furnace, a hot air circulation type electric furnace, and a steam furnace corresponding to the above (the electric furnace in the device name of each of the above-mentioned electric furnaces is replaced with a device for a steam furnace) can be used.

[0312] From the perspective of more effectively removing moisture and fluorinated compounds, the heat treatment in step (C) is preferably performed by placing the wet powder in a container with a permeable bottom and / or side surfaces. The container with a permeable bottom and / or side surfaces can be any container capable of withstanding the heat treatment temperature and is preferably made of a metal such as stainless steel.

[0313] The container having an air-permeable bottom and / or side surfaces is preferably a tray (pot) having an air-permeable bottom and / or side surfaces, and more preferably a tray having a mesh bottom and / or side surfaces (mesh tray).

[0314] The mesh is preferably any one of a woven mesh and a punched mesh.

[0315] The mesh size of the net is preferably 2000 μm or less (10 mesh or more according to the ASTM standard), more preferably 595 μm or less (30 mesh or more), further preferably 297 μm or less (50 mesh or more), still more preferably 177 μm or less (80 mesh or more), particularly preferably 149 μm or less (100 mesh or more), and particularly preferably 74 μm or less (200 mesh or more). Furthermore, it is preferably 25 μm or more (500 mesh or less).

[0316] When the net is a woven net, examples of the weaving method include plain weave, twill weave, flat weave, and diagonal weave.

[0317] When the mesh is a punched mesh, the opening ratio is preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more, and preferably 95% or less.

[0318] In step (C), the amount of the wet powder is preferably 10 g / cm2 in order to more efficiently remove water and fluorine-containing compounds. 2 Below, more preferably 8g / cm 2 Below, more preferably 5g / cm 2Below, particularly preferably 3 g / cm 2 Below, preferably 0.01 g / cm 2 More preferably, 0.05 g / cm 2 More preferably, 0.1 g / cm 2 above.

[0319] Regarding the moisture content of the wet powder subjected to heat treatment in step (C), from the perspective of being able to more efficiently remove moisture and fluorine-containing compounds, it is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, relative to the above-mentioned wet powder. In addition, it is preferably 150% by mass or less, and more preferably 100% by mass or less.

[0320] When the TFE polymers (A) and (B) are mixed in the form of powders, they can be produced by a production method including, for example, a step of obtaining the powdered TFE polymers (A) and (B) and a step of mixing the powdered TFE polymers (A) and (B).

[0321] Powdery TFE polymers (A) and (B) can be produced, for example, by separately precipitating aqueous dispersions of TFE polymer (A) and (B) to obtain wet powders, and then drying the wet powders.

[0322] The aqueous dispersion of the TFE polymer (A) and the aqueous dispersion of the TFE polymer (B) can be produced, for example, by the method described in the above step (A).

[0323] The precipitation of the aqueous dispersion and the drying of the wet powder are carried out by the same method as in the above steps (B) and (C).

[0324] From the aspect that can suppress the fibrillation of TFE polymer composition, improve powder fluidity, can improve the strength of composite sheet, the process of mixing powdered TFE polymer (A) and (B) is preferably implemented by the mixing method with weak shearing force. As the mixing method with weak shearing force, for example, mixing method without using stirring paddle such as air flow mixing and mixing using V-type blender can be enumerated.

[0325] In a conventional mixing method using a stirring blade, the TFE-based polymer may be fibrillated, and desired physical properties may not be obtained.

[0326] The TFE-based polymer composition of the present invention is obtained by mixing the TFE-based polymers (A) and (B) with, as needed, a conductive additive and the like. Furthermore, the TFE-based polymer composition of the present invention can be used as a binder for electrochemical devices, mixing with an electrode active material and a solid electrolyte. Thus, after preparing the TFE-based polymer composition of the present invention, mixing with the electrode active material and the solid electrolyte allows the TFE-based polymers (A) and (B) to be well dispersed in the TFE-based polymer composition, significantly functioning as a binder.

[0327] In the above-mentioned binder for electrochemical devices, the TFE-based polymer composition of the present invention can be used alone or mixed with other materials (e.g., polymers other than TFE-based polymers). Preferably, the TFE-based polymer composition of the present invention is used substantially alone, and more preferably alone. It should be noted that using the TFE-based polymer composition of the present invention substantially alone means using the TFE-based polymer composition in the binder for electrochemical devices in a manner such that the amount of the TFE-based polymer composition in the binder for electrochemical devices falls within the range described below.

[0328] The present invention also provides an adhesive for electrochemical devices, which is an adhesive for electrochemical devices essentially composed only of a TFE-based polymer composition, wherein the above-mentioned TFE-based polymer composition has endothermic peaks in a region (A) above 330°C and below 340°C and a region (B) above 340°C and below 350°C in differential scanning calorimetry analysis.

[0329] The binder of the present invention, by comprising a specific TFE-based polymer composition, is less likely to form aggregates even when kneaded for extended periods with powder components of electrochemical devices, such as electrode active materials and solid electrolytes, and can be uniformly mixed with the powder components. Furthermore, a composite sheet with excellent strength and flexibility can be obtained.

[0330] Furthermore, the binder of the present invention does not require the use of a large amount of dispersion medium such as water or an organic solvent, allowing for a wide selection of electrode active materials and solid electrolytes to be combined, which is advantageous in terms of the production process. Furthermore, the process and cost of using a dispersion medium can be reduced.

[0331] Furthermore, the binder of the present invention has excellent binding strength with the active material and the electrolyte, and thus the amount used can be reduced.

[0332] As the TFE-based polymer composition in the binder of the present invention, the same ones as the TFE-based polymer composition of the present invention described above can be used, and preferred embodiments are also the same.

[0333] The binder of the present invention is composed essentially only of the TFE-based polymer composition. This allows for significant utilization of the TFE-based polymer composition's benefits. "Essentially composed only of the TFE-based polymer composition" means that the TFE-based polymer composition accounts for 95.0% by mass or greater of the binder.

[0334] The content of the TFE-based polymer composition relative to the binder is preferably 98.0% by mass or more, more preferably 99.0% by mass or more, further preferably 99.5% by mass or more, particularly preferably 99.9% by mass or more, and most preferably 99.95% by mass or more.

[0335] The adhesive of the present invention is also preferably composed solely of the above-mentioned TFE-based polymer composition.

[0336] The adhesive of the present invention preferably contains substantially no organic solvent. This can reduce the process and cost of using organic solvents. Substantially containing no organic solvent means that the organic solvent content of the adhesive is 5% by mass or less.

[0337] The organic solvent content is preferably 3% by mass or less, more preferably 1% by mass or less, further preferably 0.1% by mass or less, still more preferably 0.01% by mass or less, and particularly preferably 0.001% by mass or less.

[0338] The binder of the present invention is preferably in the form of powder.

[0339] The binder of the present invention is used in electrochemical devices such as batteries and capacitors.

[0340] Examples of the battery include secondary batteries such as lithium ion batteries.

[0341] The capacitor is not particularly limited, but is preferably an electrochemical capacitor. Examples of electrochemical capacitors include electric double layer capacitors, hybrid capacitors, and redox capacitors. Examples of hybrid capacitors include sodium ion capacitors, lithium ion capacitors, and magnesium ion capacitors. Among these, electric double layer capacitors are particularly preferred.

[0342] The binder of the present invention can be preferably used as a binder for batteries or a binder for capacitors, and more preferably as a binder for secondary batteries such as lithium ion batteries.

[0343] The binder of the present invention can be used to produce electrochemical device components, preferably battery components.

[0344] The binder of the present invention can be particularly preferably used as a binder for electrodes.

[0345] Furthermore, the binder of the present invention is also preferably used as a binder in a solid electrolyte layer of a solid-state secondary battery.

[0346] The present invention also provides an electrode mixture comprising the TFE-based polymer composition of the present invention or the binder of the present invention and an electrode active material. Using the electrode mixture of the present invention, a mixture sheet having uniformly dispersed powder components and excellent strength and flexibility for an electrochemical device can be obtained. Furthermore, the strength of the mixture sheet can be improved. Furthermore, even if the amount of the binder is small, the electrode active material can be retained, allowing for the addition of more active materials, conductive additives, and other materials that improve the characteristics of the electrochemical device.

[0347] Examples of the electrode active material include positive electrode active materials and negative electrode active materials.

[0348] As the positive electrode active material, there is no particular limitation as long as it can electrochemically encapsulate and release alkali metal ions. For example, substances containing alkali metals and at least one transition metal are preferred. As specific examples, transition metal composite oxides containing alkali metals, transition metal phosphate compounds containing alkali metals, etc. can be cited. Among them, as the positive electrode active material, transition metal composite oxides containing alkali metals that can generate high voltage are particularly preferred. As the above-mentioned alkali metal ions, lithium ions, sodium ions, potassium ions, etc. can be cited. In a preferred embodiment, the alkali metal ions can be lithium ions. That is, in this embodiment, the alkali metal ion secondary battery is a lithium ion secondary battery.

[0349] Examples of the alkali metal-containing transition metal composite oxide include

[0350] Formula: M a Mn 2-b M 1 b O4

[0351] (wherein, M is at least one metal selected from the group consisting of Li, Na, and K; 0.9≤a; 0≤b≤1.5; M 1 an alkali metal manganese spinel composite oxide (lithium manganese spinel composite oxide, etc.) represented by at least one metal selected from the group consisting of Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge,

[0352] Formula: MNi 1-c M 2 c O2

[0353] (wherein, M is at least one metal selected from the group consisting of Li, Na, and K; 0≤c≤0.5; M 2an alkali metal nickel composite oxide (lithium nickel composite oxide, etc.) represented by at least one metal selected from the group consisting of Fe, Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge), or

[0354] Formula: MCo 1-d M 3 d O2

[0355] (wherein, M is at least one metal selected from the group consisting of Li, Na, and K; 0≤d≤0.5; M 3 Alkali metal cobalt composite oxide (lithium cobalt composite oxide, etc.) represented by at least one metal selected from the group consisting of Fe, Ni, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge.

[0356] Among the above, M is preferably one metal selected from the group consisting of Li, Na, and K, more preferably Li or Na, and even more preferably Li.

[0357] Among them, MCoO2, MMnO2, MNiO2, MMn2O4, MNiO2, and MMn2O4 are preferred from the perspective of providing a secondary battery with high energy density and high output. 0.8 Co 0.15 Al 0.05 O2, or MNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., preferably a compound represented by the following general formula (3).

[0358] MNi h Co i Mn j M 5 k O2(3)

[0359] (wherein, M is at least one metal selected from the group consisting of Li, Na and K, 5 is at least one selected from the group consisting of Fe, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge, (h+i+j+k)=1.0, 0≤h≤1.0, 0≤i≤1.0, 0≤j≤1.5, and 0≤k≤0.2.

[0360] Examples of the alkali metal-containing transition metal phosphate compound include the following general formula (4):

[0361] M e M 4f (PO4) g (4)

[0362] (wherein, M is at least one metal selected from the group consisting of Li, Na and K, 4 represents at least one selected from the group consisting of V, Ti, Cr, Mn, Fe, Co, Ni, and Cu, with 0.5 ≤ e ≤ 3, 1 ≤ f ≤ 2, and 1 ≤ g ≤ 3. Among the above, M is preferably a metal selected from the group consisting of Li, Na, and K, more preferably Li or Na, and even more preferably Li. That is, the alkali metal-containing transition metal phosphate compound is preferably a lithium-containing transition metal phosphate compound.

[0363] The transition metal in the lithium-containing transition metal phosphate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, or Cu. Specific examples include iron phosphates such as LiFePO4, Li3Fe2(PO4)3, and LiFeP2O7; cobalt phosphates such as LiCoPO4; and compounds obtained by replacing a portion of the transition metal atoms that form the main component of these lithium transition metal phosphate compounds with other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, and Si. The lithium-containing transition metal phosphate compound preferably has an olivine structure.

[0364] As other positive electrode active materials, lithium nickel composite oxides can be mentioned. As the lithium nickel composite oxide, the following general formula (5) is preferred:

[0365] Li y Ni 1-x M x O2(5)

[0366] (wherein, x is 0.01≤x≤0.7, y is 0.9≤y≤2.0, and M represents a metal atom (excluding Li and Ni)).

[0367] As other positive electrode active materials, MFePO4, MNi 0.8 Co 0.2 O2, M 1.2 Fe 0.4 Mn 0.4 O2、MNi 0.5 Mn 1.5 O2, MV3O6, M2MnO3, etc. In particular, M2MnO3, MNi 0.5 Mn 1.5Positive electrode active materials such as O2 are preferred in that their crystal structures do not collapse even when the secondary battery operates at a voltage exceeding 4.4V or above 4.6V. Therefore, electrochemical devices such as secondary batteries using the positive electrode material containing the above-exemplified positive electrode active materials are preferred because even when stored at high temperatures, the residual capacity is not easily reduced, the resistance increase rate does not easily change, and even when operating at high voltages, the battery performance does not deteriorate.

[0368] As other positive electrode active materials, M2MnO3 and MM can also be cited. 6 O2 (where M is at least one metal selected from the group consisting of Li, Na, and K, and M 6 is a transition metal such as Co, Ni, Mn, Fe, etc.) and solid solution materials thereof.

[0369] As the above solid solution materials, for example, the alkali metal manganese oxides represented by the general formula Mx[Mn (1-y) M 7 y O z can be cited. Here, M in the formula is at least one metal selected from the group consisting of Li, Na, and K, and M 7 is composed of at least one metal element other than M and Mn, for example, contains one or more elements selected from the group consisting of Co, Ni, Fe, Ti, Mo, W, Cr, Zr, and Sn. In addition, the values of x, y, and z in the formula are in the range of 1 < x < 2, 0 ≤ y < 1, and 1.5 < z < 3. Among them, Li 1.2 Mn 0.5 Co 0.14 Ni 0.14 O2, such a manganese-containing solid solution material based on Li2MnO3 and solid-dissolved with LiNiO2 and LiCoO2, can provide an alkali metal ion secondary battery with a high energy density and is preferred in this regard.

[0370] In addition, if the positive electrode active material contains lithium phosphate, the continuous charging characteristics are improved, so it is preferred. The use of lithium phosphate is not limited, and it is preferred to use it in combination with the above positive electrode active material. The amount of lithium phosphate used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and further preferably 0.5% by mass or more with respect to the total lower limit of the above positive electrode active material and lithium phosphate, and the upper limit is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 5% by mass or less.

[0371] Alternatively, a positive electrode active material may be used by attaching a substance having a different composition to the surface of the positive electrode active material. Examples of the surface-attached substance include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate; and carbon.

[0372] These surface-attaching substances can be attached to the surface of the positive electrode active material by, for example, the following methods: dissolving or suspending them in a solvent, adding them to the positive electrode active material by impregnation, and then drying; dissolving or suspending a precursor of the surface-attaching substance in a solvent, adding them to the positive electrode active material by impregnation, and then reacting them by heating or the like; adding them to the positive electrode active material precursor and then firing them; etc. It should be noted that in the case of attaching carbon, a method of attaching the carbon material, such as activated carbon, mechanically attaching the carbon material can also be used.

[0373] The amount of surface-attached material is preferably 0.1 ppm or more, more preferably 1 ppm or more, and even more preferably 10 ppm or more, by mass, relative to the positive electrode active material, and preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less, as an upper limit. The surface-attached material can inhibit the oxidation reaction of the electrolyte on the surface of the positive electrode active material, thereby improving battery life. However, if the amount of surface-attached material is too small, its effect may not be fully demonstrated. If the amount of surface-attached material is too large, it may hinder the entry and exit of lithium ions, thereby increasing resistance.

[0374] The shape of the particles of the positive electrode active material may include conventionally used shapes such as agglomerates, polyhedrons, spheres, ellipsoids, plates, needles, and columns. Primary particles may also aggregate to form secondary particles.

[0375] The tap density of the positive electrode active material is preferably 0.5 g / cm 3 More preferably, 0.8 g / cm 3 More preferably, 1.0 g / cm 3Above. If the tap density of the positive electrode active material is less than the above lower limit, the amount of dispersion medium required when the positive electrode active material layer is formed increases, and the required amount of conductive material and binder increases, and sometimes the filling rate of the positive electrode active material in the positive electrode active material layer is limited, and the battery capacity is limited. By using a composite oxide powder with a high tap density, a high-density positive electrode active material layer can be formed. The larger the tap density is, the better, and there is no particular upper limit. However, if it is too large, the diffusion of lithium ions using the electrolyte in the positive electrode active material layer as a medium becomes rate-limiting, and sometimes the load characteristics are easily reduced. Therefore, the upper limit is preferably 4.0 g / cm 3 Below, more preferably 3.7g / cm 3 Below, more preferably 3.5g / cm 3 the following.

[0376] The tap density is calculated as follows: 5 to 10 g of the positive electrode active material powder is placed in a 10 ml glass graduated cylinder and shaken 200 times with a stroke of about 20 mm. The tap density is g / cm 3 Find out.

[0377] The median diameter d50 of the particles of the positive electrode active material (secondary particle diameter in the case where the primary particles are agglomerated to form secondary particles) is preferably 0.3 μm or more, more preferably 0.5 μm or more, further preferably 0.8 μm or more, most preferably 1.0 μm or more, and preferably 30 μm or less, more preferably 27 μm or less, further preferably 25 μm or less, and most preferably 22 μm or less. If it is less than the above lower limit, a high tap density product may not be obtained; if it exceeds the upper limit, the diffusion of lithium in the particles takes time, thereby causing problems such as reduced battery performance. Here, by mixing two or more of the above-mentioned positive electrode active materials with different median diameters d50, the filling property during positive electrode production can also be further improved.

[0378] The median diameter d50 is measured using a known laser diffraction / scattering particle size distribution measuring device. When using LA-920 manufactured by HORIBA as a particle size distribution meter, a 0.1% by mass sodium hexametaphosphate aqueous solution is used as the dispersion medium used during measurement, and after 5 minutes of ultrasonic dispersion, the refractive index is set to 1.24 for measurement.

[0379] When the primary particles are aggregated to form secondary particles, the average primary particle size of the positive electrode active material is preferably 0.05 μm or more, more preferably 0.1 μm or more, further preferably 0.2 μm or more, and the upper limit is preferably 5 μm or less, more preferably 4 μm or less, further preferably 3 μm or less, and most preferably 2 μm or less. If the upper limit is exceeded, it is difficult to form spherical secondary particles, which has an adverse effect on the powder filling property, or the specific surface area is greatly reduced, so the possibility of reducing battery performance such as output characteristics is sometimes increased. On the other hand, if it is below the lower limit, crystallization is generally not developed, so problems such as poor reversibility of charge and discharge may occur.

[0380] The average primary particle size is determined by observation using a scanning electron microscope (SEM). Specifically, the maximum value of a slice taken horizontally from the left and right boundaries of each primary particle is obtained for any 50 primary particles in a photograph at a magnification of 10,000 times, and the average value is taken to determine the primary particle size.

[0381] The BET specific surface area of ​​the positive electrode active material is preferably 0.1 m 2 / g or more, more preferably 0.2m 2 / g or more, more preferably 0.3m 2 / g or more, and the upper limit is preferably 50m 2 / g or less, more preferably 40m 2 / g or less, more preferably 30m 2 If the BET specific surface area is smaller than this range, the battery performance is likely to decrease; if the BET specific surface area is larger than this range, it is difficult to increase the tap density, and sometimes the processability during the formation of the positive electrode active material layer is likely to be problematic.

[0382] The above-mentioned BET specific surface area is defined as follows: using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken Co., Ltd.), the sample is pre-dried at 150°C for 30 minutes under nitrogen circulation, and then a nitrogen-helium mixed gas accurately adjusted to a relative pressure value of nitrogen relative to atmospheric pressure of 0.3 is used to measure the sample by the nitrogen adsorption BET single-point method based on the gas flow method, and the obtained value is used to define the BET specific surface area.

[0383] When the secondary battery of the present invention is used as a large lithium-ion secondary battery for hybrid vehicles or distributed power sources, high output is required, so the particles of the positive electrode active material are preferably mainly secondary particles. The particles of the positive electrode active material preferably have an average particle size of secondary particles of 40 μm or less and contain 0.5% to 7.0% by volume of microparticles with an average primary particle size of 1 μm or less. By containing microparticles with an average primary particle size of 1 μm or less, the contact area with the electrolyte becomes larger, which can further accelerate the diffusion of lithium ions between the electrode mixture and the electrolyte, and as a result, the output performance of the battery can be improved.

[0384] As a method for producing the positive electrode active material, a common method for producing inorganic compounds is used. In particular, various methods are considered for producing spherical or ellipsoidal active materials, for example, the following method can be mentioned: dissolving or crushing a transition metal raw material and dispersing it in a solvent such as water, adjusting the pH under stirring, producing a spherical precursor and recovering it, drying it as needed, then adding a lithium source such as LiOH, Li2CO3, LiNO3, and calcining it at high temperature to obtain the active material.

[0385] In order to manufacture the positive electrode, the above-mentioned positive electrode active materials can be used alone, or two or more of different compositions can be used in any combination or ratio. As a preferred combination in this case, LiCoO2 and LiNi 0.33 Co 0.33 Mn 0.33 O2 and other ternary combinations, LiCoO2 and LiMn2O4 or a combination in which a portion of the Mn is replaced by other transition metals, or a combination in which a portion of the Co is replaced by other transition metals, etc.

[0386] From the perspective of high battery capacity, the content of the above-mentioned positive electrode active material is preferably 50% to 99.5% by mass of the positive electrode mixture, and more preferably 80% to 99% by mass. In addition, the content in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. In addition, the upper limit is preferably 99% by mass or less, and more preferably 98% by mass or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the capacitance may be insufficient. On the contrary, if the content is too high, the strength of the positive electrode may be insufficient.

[0387] The negative electrode active material is not particularly limited, and examples thereof include materials selected from lithium metal, artificial graphite, graphite carbon fiber, resin-fired carbon, pyrolysis vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-fired carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and carbon containing carbon materials such as non-graphitizable carbon, silicon-containing compounds such as silicon and silicon alloys, Li4Ti5O 12 Among them, a substance containing at least a portion of a carbonaceous material or a silicon-containing compound can be particularly preferably used.

[0388] The negative electrode active material used in the present invention preferably contains silicon among its constituent elements. By containing silicon among its constituent elements, a high-capacity battery can be produced.

[0389] The silicon-containing material is preferably silicon particles, particles having a structure in which silicon microparticles are dispersed in a silicon-based compound, silicon oxide particles represented by the general formula SiOx (0.5≤x≤1.6), or a mixture thereof. By using these materials, a negative electrode mixture for a lithium-ion secondary battery with higher initial charge and discharge efficiency, high capacity, and excellent cycle characteristics is obtained.

[0390] Silicon oxide in the present invention is a general term for amorphous silicon oxides. Silicon oxide before disproportionation is represented by the general formula SiOx (0.5 ≤ x ≤ 1.6). x is preferably 0.8 ≤ x < 1.6, and more preferably 0.8 ≤ x < 1.3. Silicon oxide can be obtained, for example, by heating a mixture of silicon dioxide and metallic silicon and cooling and precipitating the generated silicon monoxide gas.

[0391] Particles having a structure in which silicon microparticles are dispersed in a silicon-based compound can be obtained, for example, by mixing silicon microparticles with a silicon-based compound and sintering the mixture; or by heat-treating silicon oxide particles before disproportionation represented by the general formula SiOx in an inert, non-oxidizing atmosphere such as argon at a temperature of 400°C or higher, preferably 800°C to 1,100°C, to carry out a disproportionation reaction. In particular, the material obtained by the latter method is preferred because the silicon microcrystals are uniformly dispersed. The above-mentioned disproportionation reaction can make the size of silicon nanoparticles 1nm to 100nm. It should be noted that the silicon oxide in the particles having a structure in which silicon nanoparticles are dispersed in silicon oxide is preferably silicon dioxide. It should be noted that the silicon nanoparticles (crystals) dispersed in the amorphous silicon oxide can be confirmed by transmission electron microscopy.

[0392] The physical properties of the silicon-containing particles can be appropriately selected depending on the desired composite particles. For example, the average particle size is preferably 0.1 μm to 50 μm, with the lower limit more preferably being 0.2 μm or greater, and even more preferably being 0.5 μm or greater. The upper limit is more preferably 30 μm or less, and even more preferably 20 μm or less. The above average particle size is expressed as the weight-average particle size as determined by particle size distribution measurement using laser diffraction.

[0393] The BET specific surface area is preferably 0.5 m 2 / g~100m 2 / g, more preferably 1m 2 / g~20m 2 / g. If the BET specific surface area is 0.5m 2 / g or more, there is no possibility of reduced adhesion when processing to the electrode and reduced electrochemical device characteristics. 2 / g or less, the proportion of silicon dioxide on the particle surface becomes large, and the battery capacity does not decrease when used as a negative electrode material for a lithium ion secondary battery.

[0394] By imparting conductivity to the silicon-containing particles by carbon coating, improved electrochemical device properties have been observed. Examples of methods for imparting conductivity include mixing the silicon-containing particles with conductive particles such as graphite, coating the surfaces of the silicon-containing particles with a carbon coating, and a combination of the two. Carbon coating is preferred, and chemical vapor deposition (CVD) is more preferred.

[0395] In order to increase the capacity of the obtained electrode mixture, the content of the above-mentioned negative electrode active material is preferably more than 40 mass %, more preferably more than 50 mass %, particularly preferably more than 60 mass %. In addition, the upper limit is preferably below 99 mass %, more preferably below 98 mass %.

[0396] The electrode mixture of the present invention preferably further comprises a conductive additive. The conductive additive may be contained in the TFE-based polymer composition of the present invention or may be added separately from the TFE-based polymer composition of the present invention.

[0397] The conductive additive is used in an amount generally containing 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and generally 50% by mass or less, preferably 30% by mass or less, and more preferably 15% by mass or less in the electrode mixture. If the content is below this range, the conductivity may be insufficient. On the other hand, if the content is above this range, the battery capacity may be reduced.

[0398] The electrode mixture of the present invention can further comprise a thermoplastic resin. As the thermoplastic resin, polyvinylidene fluoride, polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polyethylene oxide etc. can be enumerated. One can be used alone, or two or more can be used in any combination and ratio.

[0399] Thermoplastic resin is generally more than the 0.01 mass %, is preferably more than the 0.05 mass %, more preferably more than the 0.10 mass %, in addition, is generally below the 3.0 mass %, is preferably below the 2.5 mass %, more preferably the scope below the 2.0 mass %.By adding thermoplastic resin, the mechanical strength of electrode can be improved.In addition, if exceed this scope, then the shared ratio of electrode active material in electrode mixture reduces, and sometimes produces the problem that the capacity of electrochemical device reduces or the problem that the resistance between active material increases.

[0400] In the electrode mixture of the present invention, the content of the binding agent can be more than 0.1 mass %, preferably more than 0.2 mass %, more preferably more than 0.5 mass % relative to the above-mentioned electrode mixture. In addition, it can be less than 50 mass %, preferably less than 40 mass %, more preferably less than 30 mass %, and then more preferably less than 10 mass %, particularly preferably less than 5 mass %, and most preferably less than 3 mass %. If the ratio of the binding agent is too low, the electrode mixture active material can sometimes not be fully maintained, and the mechanical strength of the electrode mixture sheet is insufficient, which can deteriorate the battery performance such as cycle characteristics. On the other hand, if the ratio of the binding agent is too high, it can sometimes lead to a reduction in battery capacity and conductivity. The binding force of the binding agent of the present invention is excellent, so even if the content is small, the electrode active material can be fully maintained.

[0401] In the electrode mixture of the present invention, the binder component is preferably substantially composed only of the above-mentioned TFE-based polymer composition, and more preferably composed only of the above-mentioned TFE-based polymer composition. The binder component being substantially composed only of the above-mentioned TFE-based polymer composition means that the content of the above-mentioned TFE-based polymer composition in the binder component constituting the electrode mixture is 95.0% by mass or more relative to the above-mentioned binder component. The content of the above-mentioned TFE-based polymer composition is preferably 98.0% by mass or more, more preferably 99.0% by mass or more, further preferably 99.5% by mass or more, particularly preferably 99.9% by mass or more, and most preferably 99.95% by mass or more relative to the above-mentioned binder component.

[0402] The electrode mixture of the present invention is preferably in the form of a sheet.

[0403] The electrode mixture of the present invention can be suitably used as an electrode mixture for secondary batteries. In particular, the electrode mixture of the present invention is suitable for lithium-ion secondary batteries. When used in secondary batteries, the electrode mixture of the present invention is usually used in a sheet form.

[0404] The thickness of the electrode mixture sheet is preferably 300 μm or less, more preferably 250 μm or less, further preferably 200 μm or less, still more preferably 180 μm or less, and particularly preferably 150 μm or less. It is preferably 10 μm or more, more preferably 15 μm or more, and further preferably 20 μm or more.

[0405] An example of a specific method for producing an electrode mixture sheet containing an electrode mixture is described below. The electrode mixture sheet can be produced by a production method comprising the following steps: a step (1) of mixing a raw material composition containing an electrode active material, a binder, and, if necessary, a conductive additive; a step (2) of forming the raw material composition obtained in step (1) into a block; and a step (3) of rolling the block of raw material composition obtained in step (2) into a sheet.

[0406] In the step (1) of mixing the raw material composition, the raw material composition is present in a state where the electrode active material, the binder, etc. are simply mixed and do not have a fixed shape. Specific mixing methods include methods using a W-type mixer, a V-type mixer, a drum mixer, a ribbon mixer, a conical screw mixer, a single-screw kneader, a twin-screw kneader, a mill mixer, a stirring mixer, a planetary mixer, and the like.

[0407] In the above-mentioned step (1), the binder mixing condition is preferably below 3000 rpm. It is preferably above 10 rpm, more preferably above 15 rpm, and further preferably above 20 rpm. In addition, it is preferably below 2000 rpm, more preferably below 1500 rpm, and further preferably below 1000 rpm. If it is lower than the above-mentioned range, mixing takes time, which will affect productivity. In addition, if it exceeds the above-mentioned range, fibrillation will be excessive, and it is possible to form an electrode composite sheet with poor strength and flexibility.

[0408] In the above step (2), forming the raw material composition into a block means forming the raw material composition into a single block. Specific methods for forming the raw material composition into a block include extrusion molding, compression molding, and the like. Furthermore, the term "block" is not particularly specific in shape, and any shape that is in a single block may be used, including rod-like, sheet-like, spherical, and cubic shapes.

[0409] Specific examples of the rolling method in the step (3) include methods using a roll press, a flat plate press, a calender roll machine, and the like.

[0410] In addition, it is also preferred to have a step (4) after the step (3): applying a greater load to the obtained calendered sheet to calender it into a thinner sheet. It is also preferred to repeat the step (4). In this way, instead of thinning the calendered sheet all at once, it is calendered little by little in stages, thereby making the softness better. As the number of times of step (4), it is preferably 2 times or more and 10 times or less, more preferably 3 times or more and 9 times or less. As a specific calendering method, for example, the following method can be cited: rotating 2 or more rollers, passing the calendered sheet between them, thereby processing it into a thinner sheet.

[0411] Furthermore, from the perspective of adjusting the fibril diameter, it is also preferable to include a step (5) after step (3) or step (4): coarsely crushing the rolled sheet, reshaping it into a block, and rolling it into a sheet. It is also preferable to repeat step (5). The number of times step (5) is performed is preferably 1 or more and 12 or less, and more preferably 2 or more and 11 or less.

[0412] In step (5), specific methods for roughly crushing the rolled sheet and forming it into a block shape include folding the sheet, forming it into a rod or film sheet, and forming it into chips. In the present invention, "roughly crushing" means changing the form of the rolled sheet obtained in step (3) or step (4) into another form in order to roll it into a sheet in the next step, and also includes simply folding the rolled sheet.

[0413] Alternatively, step (4) may be performed after step (5), or may be repeated. Alternatively, uniaxial stretching or biaxial stretching may be performed in steps (2) or (3), (4), and (5). Furthermore, the fibril diameter may be adjusted by the degree of coarse crushing in step (5).

[0414] In the above-mentioned steps (3), (4) or (5), the calendering rate is preferably 10% or more, more preferably 20% or more, and preferably 80% or less, more preferably 65% ​​or less, and more preferably 50% or less. If it is less than the above-mentioned range, time is consumed as the number of calendering times increases, which affects productivity. In addition, if it exceeds the above-mentioned range, fibrillation is excessively carried out, and it is possible to form an electrode mixture sheet with poor strength and flexibility. It should be noted that the calendering rate mentioned here refers to the reduction rate of the thickness of the sample after processing relative to the thickness before calendering. The sample before calendering can be a block-shaped raw material composition or a sheet-shaped raw material composition. The thickness of the sample refers to the thickness in the direction of applying the load during calendering.

[0415] The electrode mixture sheet can also be suitably manufactured by the following manufacturing method, which is characterized in that it includes:

[0416] Step (a): a step of mixing the powder components and the binder to form an electrode mixture; and

[0417] Step (b): the step of rolling or extruding the electrode mixture to form a sheet.

[0418] The mixing in step (a) includes:

[0419] (a1) a step of homogenizing the powder components and the binder to form a powder;

[0420] (a2) A step of mixing the powdered raw material mixture obtained in step (a1) to prepare an electrode mixture.

[0421] For example, PTFE has two transition temperatures, at approximately 19°C and 30°C. Below 19°C, PTFE can be easily mixed while maintaining its shape. However, above 19°C, the structure of the PTFE particles becomes loose, making them more sensitive to mechanical shear. At temperatures exceeding 30°C, a higher degree of fibrillation occurs.

[0422] Therefore, the homogenization of (a1) is preferably performed at a temperature of 19°C or lower, preferably 0°C to 19°C.

[0423] That is, in such (a1), it is preferable to perform mixing and homogenization while suppressing fibrillation.

[0424] The mixing in the subsequent step (a2) is preferably performed at a temperature of 30° C. or higher to promote fibrillation.

[0425] The step (a2) is preferably performed at a temperature of 30°C to 150°C, more preferably 35°C to 120°C, and still more preferably 40°C to 80°C.

[0426] In one embodiment, the calendering or extrusion in step (b) is performed 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.

[0427] The mixing in the step (a) is preferably performed while applying a shearing force.

[0428] Specific mixing methods include methods using a W-type mixer, a V-type mixer, a drum mixer, a ribbon mixer, a conical screw mixer, a single-screw kneader, a twin-screw kneader, a co-mill, a stirring mixer, a planetary mixer, a Henschel mixer, a high-speed mixer, and the like.

[0429] The mixing conditions can be set as long as the rotation speed and mixing time are appropriately set. For example, the rotation speed is preferably below 15000 rpm. It is preferably above 10 rpm, more preferably above 50 rpm, and further preferably above 100 rpm. In addition, it is preferably below 12000 rpm, more preferably below 10000 rpm, and further preferably below 8000 rpm. If it is lower than the above range, mixing takes time and productivity is affected. In addition, if it exceeds the above range, fibrillation is excessively carried out, which may result in an electrode mixture sheet with poor strength.

[0430] In the step (a1), it is preferred to perform the step with a shearing force weaker than that in the step (a2).

[0431] Furthermore, the step (a1) is preferably performed in a shorter time than the step (a2).

[0432] In the 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 powdered raw material mixture obtained in the step (a1) to prepare a paste.

[0433] The lubricant is not particularly limited, and examples thereof include water, ether compounds, alcohols, ionic liquids, carbonates, aliphatic hydrocarbons (low-polarity solvents such as heptane and xylene), isoparaffinic hydrocarbon compounds, and petroleum fractions (gasoline (C4-C10), naphtha (C4-C11), kerosene / paraffins (C10-C16), and mixtures thereof).

[0434] The water content of the lubricant is preferably 1000 ppm or less.

[0435] The water content is preferably 1000 ppm or less in terms of reducing degradation of the electrochemical device, and is more preferably 500 ppm or less.

[0436] When the above-mentioned lubricant is used, a low-polarity solvent such as butyl butyrate or an ether compound is particularly preferred.

[0437] When the lubricant is used, the amount thereof may be 5.0 to 35.0 parts by weight, preferably 10.0 to 30.0 parts by weight, and more preferably 15.0 to 25.0 parts by weight, relative to the total weight of the composition to be used in step (a1).

[0438] The above-mentioned raw material composition preferably does not substantially contain a liquid medium. Existing electrode mixture formation methods generally use a solvent that dissolves the binder to prepare a slurry in which a powder as an electrode mixture component is dispersed, and the electrode mixture sheet is prepared by coating / drying the slurry. In this case, a solvent that disperses or dissolves the binder is used. However, the solvents that can dissolve the binder resin commonly used in the past are limited to specific solvents such as N-methylpyrrolidone. Due to the high polarity and the drying process, the process and cost of using solvents will be generated. In addition, they react with electrolytes such as electrolytes and solid electrolytes to deteriorate the electrolyte. Therefore, the residual components during slurry preparation and after drying sometimes become the reason for the reduction of battery performance. In addition, in the case of low-polarity solvents such as heptane, the dissolved binder resin is very limited, and sometimes the flash point is low and the operation becomes complicated.

[0439] By using a powdered binder with low water content instead of a solvent when forming the electrode mixture sheet, a battery with minimal electrolyte degradation can be manufactured. Furthermore, the above-described manufacturing method can produce an electrode mixture sheet containing a binder with a fine fiber structure, and by eliminating the need for slurry preparation, the burden of the manufacturing process can be reduced.

[0440] Step (b) is calendering or extrusion. Calendering or extrusion can be performed by known methods. Thus, the electrode mixture sheet can be formed.

[0441] The step (b) preferably includes: (b1) forming the electrode mixture obtained in the step (a) into a block; and (b2) rolling or extruding the block of electrode mixture.

[0442] Molding into a block shape means forming the electrode mixture into a single block.

[0443] Specific methods of forming the block include extrusion molding, press molding, and the like.

[0444] The term "block" is not particularly specific in shape; any block may be formed into a single block, including rods, flakes, spheres, cubes, and other shapes. The block preferably has a cross-sectional diameter or the smallest side of 10,000 μm or greater, and more preferably 20,000 μm or greater.

[0445] As a specific method of the calendering or extrusion molding in the step (b2), there can be mentioned a method of calendering the electrode mixture using a roll press, a calender roll machine, or the like.

[0446] The above step (b) is preferably performed at 30° C. to 150° C. As described above, PTFE has a glass transition temperature around 30° C. and is therefore easily fibrillated at 30° C. or higher. Therefore, the step (b) is preferably performed at such a temperature.

[0447] Furthermore, since shearing force is applied during calendering or extrusion, PTFE is fibrillated and molded.

[0448] After step (b), it is also preferred to have step (c) of applying a greater load to the resulting calendered sheet to thereby calender it into a thinner sheet. It is also preferred to repeat step (c). In this way, rather than thinning the calendered sheet all at once, the calendering is performed step by step, thereby further improving the flexibility.

[0449] The number of times of performing step (c) is preferably 2 or more and 10 or less, more preferably 3 or more and 9 or less.

[0450] Specific examples of the calendering method include a method in which two or more rolls are rotated and a calendered sheet is passed between the rolls to thereby form a thinner sheet.

[0451] Furthermore, from the perspective of adjusting sheet strength, it is also preferred to include a step (d) after step (b) or step (c): coarsely crushing the rolled sheet, reshaping it into a block, and rolling it into a sheet. It is also preferred to repeat step (d). The number of times step (d) is performed is preferably 1 to 12 times, and more preferably 2 to 11 times.

[0452] In step (d), specific methods for roughly crushing the rolled sheet and forming it into a block include folding the rolled sheet, forming it into a rod or film sheet, forming it into chips, etc. In the present invention, "roughly crushing" means changing the form of the rolled sheet obtained in step (b) or step (c) into another form in order to roll it into a sheet in the next step, and also includes simply folding the rolled sheet.

[0453] In addition, step (c) may be performed after step (d), or the steps may be repeated.

[0454] Furthermore, uniaxial stretching or biaxial stretching may be performed in the steps (a) or (b), (c), and (d).

[0455] Furthermore, the sheet strength can also be adjusted by adjusting the degree of coarse pulverization in step (d).

[0456] In the above steps (b), (c), or (d), the calendering rate is preferably 10% or more, more preferably 20% or more, and preferably 80% or less, more preferably 65% ​​or less, and even more preferably 50% or less. If the calendering rate is less than the above range, time is consumed as the number of calendering times increases, which affects productivity. If the calendering rate exceeds the above range, fibrillation may occur excessively, resulting in an electrode mixture sheet with poor strength and flexibility.

[0457] It should be noted that the rolling rate herein refers to the reduction rate of the thickness of the sample after processing relative to the thickness before the rolling process. The sample before rolling can be a block-shaped raw material composition or a sheet-shaped raw material composition. The thickness of the sample refers to the thickness in the direction of the load applied during rolling.

[0458] The above steps (c) to (d) are preferably performed at 30°C or higher, more preferably 60°C or higher, and preferably 150°C or lower.

[0459] The electrode mixture sheet can be used as an electrode mixture sheet for a secondary battery. It can be used as either a negative electrode or a positive electrode. The electrode mixture sheet is particularly suitable for lithium-ion secondary batteries.

[0460] The present invention also provides an electrode comprising the TFE-based polymer composition of the present invention or the binder of the present invention, an electrode active material, and a current collector. The electrode of the present invention has a uniform dispersion of the powder components of the electrochemical device and excellent strength and flexibility. Furthermore, even with a small amount of binder, the electrode active material can be retained, allowing for the addition of more active material, conductive additive, or other materials that improve the characteristics of the electrochemical device.

[0461] The electrode of the present invention may include the electrode mixture of the present invention (preferably an electrode mixture sheet) and a current collector.

[0462] The electrode of the present invention may be a positive electrode or a negative electrode.

[0463] The positive electrode preferably comprises a current collector and an electrode mixture sheet containing the positive electrode active material. Examples of materials for the positive electrode current collector include metals such as aluminum, titanium, tantalum, stainless steel, nickel, or alloys thereof; and carbon materials such as carbon cloth and carbon paper. Metallic materials, particularly aluminum or its alloys, are preferred.

[0464] As the shape of the current collector, in the case of metal materials, metal foil, metal cylinder, metal coil, metal plate, metal mesh, stamped metal, foamed metal, etc. can be mentioned. In the case of carbon materials, carbon plate, carbon film, carbon cylinder, etc. can be mentioned. Among these, metal foil is preferred. It should be noted that the metal foil can be suitably formed into a mesh. The thickness of the metal foil is arbitrary, usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. If the metal foil is thinner than this range, the strength required as a current collector is sometimes insufficient. On the contrary, if the metal foil is thicker than this range, the handleability is sometimes impaired.

[0465] In order to reduce the electrical contact resistance between the current collector and the positive electrode active material layer, it is also preferable to coat the surface of the current collector with a conductive additive. Examples of the conductive additive include carbon or noble metals such as gold, platinum, and silver.

[0466] The positive electrode can be produced by a conventional method, for example, by laminating the electrode mixture sheet and the current collector with an adhesive and vacuum drying the laminate.

[0467] The density of the positive electrode mixture sheet is preferably 2.80 g / cm 3 More preferably, 3.00 g / cm 3 More preferably, 3.20 g / cm 3 More than, in addition, preferably 3.80g / cm 3 Below, more preferably 3.75g / cm 3 Below, more preferably 3.70g / cm 3 If the value exceeds this range, cracks may occur in the sheet. If the value is less than this range, the conductivity between the active materials decreases, which may increase the battery resistance and prevent high output.

[0468] The thickness of the positive electrode is not particularly limited. From the perspective of high capacity and high output, the thickness of the composite layer after deducting the thickness of the metal foil of the collector is preferably greater than 10 μm, more preferably greater than 20 μm, relative to a single side of the collector as the lower limit. In addition, it is preferably less than 500 μm, more preferably less than 450 μm.

[0469] The negative electrode preferably comprises a current collector and an electrode mixture sheet containing the negative electrode active material. Examples of materials for the negative electrode current collector include metals such as copper, nickel, titanium, tantalum, stainless steel, or alloys thereof; and carbon materials such as carbon cloth and carbon paper. Metallic materials are preferred, with copper, nickel, or alloys thereof being particularly preferred.

[0470] As the shape of the current collector, in the case of metal materials, metal foil, metal cylinder, metal coil, metal plate, metal mesh, stamped metal, foamed metal, etc. can be mentioned. In the case of carbon materials, carbon plate, carbon film, carbon cylinder, etc. can be mentioned. Among these, metal foil is preferred. It should be noted that the metal foil can be suitably formed into a mesh. The thickness of the metal foil is arbitrary, usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. If the metal foil is thinner than this range, the strength required as a current collector is sometimes insufficient. On the contrary, if the metal foil is thicker than this range, the handleability is sometimes impaired.

[0471] The negative electrode can be produced by conventional methods, such as laminating the electrode mixture sheet and the current collector with a binder and vacuum drying.

[0472] The density of the negative electrode mixture is preferably 1.3 g / cm 3 More preferably, 1.4 g / cm 3 More preferably, 1.5 g / cm 3 More than, and preferably 2.0 g / cm 3 Below, more preferably 1.9 g / cm 3 Below, more preferably 1.8 g / cm 3 If the value exceeds this range, cracks may occur in the sheet. If the value is less than this range, the conductivity between the active materials decreases, which may increase the battery resistance and prevent high output.

[0473] The thickness of the negative electrode is not particularly limited. From the perspective of high capacity and high output, the thickness of the composite layer after deducting the thickness of the metal foil of the collector is preferably greater than 10 μm, more preferably greater than 20 μm, relative to a single side of the collector as the lower limit. In addition, it is preferably less than 500 μm, more preferably less than 450 μm.

[0474] The present invention also provides a secondary battery comprising the electrode of the present invention.

[0475] The secondary battery of the present invention may be a secondary battery using an electrolyte solution or a solid-state secondary battery.

[0476] It should be noted that in this specification, a solid-state secondary battery may be any secondary battery containing a solid electrolyte, and may be a semi-solid secondary battery containing a solid electrolyte and a liquid component as the electrolyte, or an all-solid-state secondary battery containing only a solid electrolyte as the electrolyte.

[0477] The secondary battery using the above-mentioned electrolyte solution can use the electrolyte solution, separator, etc. used for a well-known secondary battery. These will be described in detail below.

[0478] As the electrolyte solution, a non-aqueous electrolyte solution is preferably used. As the non-aqueous electrolyte solution, a solution prepared by dissolving a known electrolyte salt in a known organic solvent for dissolving the electrolyte salt can be used.

[0479] The organic solvent for dissolving the electrolyte salt is not particularly limited, and known hydrocarbon solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; and one or more fluorine-based solvents such as fluoroethylene carbonate, fluoroethers, and fluorinated carbonates can be used.

[0480] As electrolyte salts, for example, LiClO4, LiAsF6, LiBF4, LiPF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, etc. can be cited. From the perspective of good cycle characteristics, LiPF6, LiBF4, LiN(SO2CF3)2, LiN(SO2C2F5)2 or a combination thereof is particularly preferred.

[0481] The concentration of the electrolyte salt is preferably 0.8 mol / L or more, more preferably 1.0 mol / L or more. The upper limit depends on the organic solvent used to dissolve the electrolyte salt, but is usually 1.5 mol / L.

[0482] The secondary battery using the above electrolyte preferably also includes a separator. The material and shape of the separator are not particularly limited as long as the electrolyte is stable and the liquid retention is excellent, and known separators can be used. Among them, it is preferred to use a porous sheet or non-woven fabric-like material formed from a material stable for the above electrolyte, using a resin, glass fiber, an inorganic substance, etc., and having excellent liquid retention.

[0483] Materials for the resin and glass fiber separators include polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, and glass filters. These materials, such as polypropylene / polyethylene two-layer membranes and polypropylene / polyethylene / polypropylene three-layer membranes, can be used alone or in any combination and ratio. For excellent electrolyte permeability and shutdown effects, the separators are preferably porous sheets or nonwoven fabrics made from polyolefins such as polyethylene and polypropylene.

[0484] The thickness of the separator is arbitrary, and is usually 1 μm or more, preferably 5 μm or more, more preferably 8 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is too thin compared to the above range, the insulation and mechanical strength may be reduced. In addition, if it is too thick compared to the above range, the battery performance such as rate characteristics may be reduced, and the energy density of the electrolyte battery as a whole may be reduced.

[0485] On the other hand, as inorganic materials, oxides such as aluminum oxide and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used, and materials in the form of particles or fibers are used.

[0486] As a form, a non-woven fabric, a woven fabric, a microporous membrane or other thin film-shaped material can be used. In the case of a thin film, a film with a pore size of 0.01 μm to 1 μm and a thickness of 5 μm to 50 μm is preferably used. In addition to the above-mentioned independent thin film shapes, a separator can also be used in which a composite porous layer containing particles of the above-mentioned inorganic substance is formed on the surface of the positive electrode and / or the negative electrode using a resin binder. For example, a fluororesin can be used as a binder, and a porous layer of aluminum oxide particles with a particle size of 90% less than 1 μm is formed on both sides of the positive electrode.

[0487] The material of the housing is not particularly limited as long as it is stable against the electrolyte used. Specifically, metals such as nickel-plated steel, stainless steel, aluminum or aluminum alloys, and magnesium alloys can be used; or laminated films of resin and aluminum foil can be used. For lightweighting purposes, aluminum or aluminum alloys and laminated films are preferably used.

[0488] Among the metal shells, there are those in which metals are welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed encapsulated structure; or those in which the above metals are used to form a riveted structure through a resin gasket. Among the shells using the above laminated films, there are those in which a sealed encapsulated structure is formed by thermally bonding resin layers to each other. In order to improve the sealing performance, a resin different from the resin used in the laminated film may be sandwiched between the above resin layers. In particular, in the case of forming a sealed structure by thermally bonding resin layers through collector terminals, since the metal and the resin are bonded, it is preferred to use a resin having a polar group or a modified resin into which a polar group is introduced as the sandwiched resin.

[0489] The secondary battery using the above electrolyte solution can be of any shape, including cylindrical, rectangular, laminated, button, and large shapes. The shape and structure of the positive electrode, negative electrode, and separator can be varied according to the shape of each battery.

[0490] The solid-state secondary battery is preferably an all-solid-state secondary battery, preferably a lithium-ion battery, and also preferably a sulfide-based solid-state secondary battery.

[0491] The solid-state secondary battery preferably includes a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode.

[0492] In the above-mentioned solid-state secondary battery, the binder of the present invention can be used in the electrode layer or in the solid electrolyte layer.

[0493] A solid secondary battery mixture (preferably a mixture sheet) comprising the binder of the present invention and a solid electrolyte, and a solid electrolyte layer (preferably a solid electrolyte layer sheet) comprising the binder of the present invention and a solid electrolyte are also preferred embodiments of the present invention.

[0494] The solid electrolyte used in the mixture for solid-state secondary batteries can be a sulfide-based solid electrolyte or an oxide-based solid electrolyte. In particular, the use of a sulfide-based solid electrolyte has the advantage of being flexible.

[0495] The sulfide-based solid electrolyte is not particularly limited, and can be selected from Li2S-P2S5, Li2S-P2S3, Li2S-P2S3-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, LiI-Li2S-SiS2-P2S5, Li2S-SiS2-Li4SiO4, Li2S-SiS2-Li3PO4, Li3PS4-Li4GeS4, Li 3.4 P 0.6 Si 0.4 S4, Li 3.25 P 0.25 Ge 0.76 S4, Li 4-x Ge 1-x P x S4 (X = 0.6 to 0.8), Li 4+y Ge 1-y Ga y S4 (y=0.2~0.3), LiPSCl, LiCl, Li 7-x-2y PS 6-x-y Cl x (0.8≤x≤1.7, 0 <y≤-0.25x+0.5)、Li 10 SnP2S 12 Any one or a mixture of two or more thereof.

[0496] The sulfide-based solid electrolyte preferably contains lithium. Sulfide-based solid electrolytes containing lithium are used in solid-state batteries using lithium ions as carriers and are particularly preferred for electrochemical devices having high energy density.

[0497] The oxide-based solid electrolyte is preferably a compound containing oxygen atoms (O), having ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and having electronic insulation properties.

[0498] As specific examples of compounds, for example, Li xa La ya TiO3[xa=0.3~0.7, ya=0.3~0.7](LLT), Li xb La yb Zr zb Mbb mb O nb (M bb is at least one element selected from the group consisting of Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, and Sn, with xb satisfying 5≤xb≤10, yb satisfying 1≤yb≤4, zb satisfying 1≤zb≤4, mb satisfying 0≤mb≤2, and nb satisfying 5≤nb≤20), Li xc B yc M cc zc O nc (M cc is at least one element selected from C, S, Al, Si, Ga, Ge, In, and Sn, with xc satisfying 0≤xc≤5, yc satisfying 0≤yc≤1, zc satisfying 0≤zc≤1, and nc satisfying 0≤nc≤6), Li xd (Al,Ga) yd (Ti,Ge) zd Si ad P md O nd (where 1≤xd≤3, 0≤yd≤2, 0≤zd≤2, 0≤ad≤2, 1≤md≤7, 3≤nd≤15), Li (3-2xe) M ee xe D ee O(xe represents a number greater than or equal to 0.1 and less than or equal to 0.1, M ee Represents a divalent metal atom. ee represents a halogen atom or a combination of two or more halogen atoms), Li xf Si yf O zf (1≤xf≤5,0 <yf≤3,1≤zf≤10)、Li xg S yg O zg (1≤xg≤3,0 <yg≤2,1≤zg≤10)、Li3BO3-Li2SO4、Li2O-B2O3-P2O5、Li2O-SiO2、Li6BaLa2Ta2O 12 、Li3PO (4-3 / 2w) N w (w satisfies w<1), Li with LISICON (lithium superion conductor) type crystal structure 3.5 Zn 0.25 GeO4, La with perovskite crystal structure 0.51 Li 0.34 TiO 2.94 、La 0.55 Li 0.35TiO3, LiTi2P3O with NASICON (sodium superion conductor) crystal structure 12 、Li 1+xh+yh (Al,Ga) xh (Ti,Ge) 2-xh Si yh P 3-yh O 12 (where 0≤xh≤1, 0≤yh≤1), Li7La3Zr2O with garnet crystal structure 12 (LLZ) etc. In addition, ceramic materials in which LLZ is partially replaced with Al are also known. For example, Li 6.24 La3Zr2Al 0.24 O 11.98 、Li 6.25 Al 0.25 La3Zr2O 12 、Li after partial replacement with Ta 6.6 La3Zr 1.6 Ta 0.4 O 12 , Li partially replaced by Nb 6.75 La3Zr 1.75 Nb 0.25 O 12 Etc. In addition, LLZ-based ceramic materials in which LLZ is replaced with at least one element of Mg (magnesium) and A (A is at least one element selected from the group consisting of Ca (calcium), Sr (strontium), and Ba (barium)) can also be cited. In addition, phosphorus compounds containing Li, P, and O are also preferred. For example, lithium phosphate (Li3PO4), LiPON in which part of the oxygen in lithium phosphate is replaced with nitrogen, and LiPOD can be cited. 1 (D 1 is at least one selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Ag, Ta, W, Pt, Au, etc. In addition, LiA 1 ON(A 1 is at least one selected from Si, B, Ge, Al, C, Ga, etc. Specific examples include Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2 and Li2O-Al2O3-SiO2-P2O5-TiO2.

[0499] The oxide-based solid electrolyte preferably contains lithium. Oxide-based solid electrolytes containing lithium are used in solid-state batteries using lithium ions as carriers, and are particularly preferred from the perspective of electrochemical devices having high energy density.

[0500] The above oxide-based solid electrolyte is preferably an oxide having a crystalline structure. From the perspective of good Li ion conductivity, an oxide having a crystalline structure is particularly preferred. Examples of oxides having a crystalline structure include perovskite-type (La 0.51 Li 0.34 TiO 2.94 etc.), NASICON type (Li 1.3 Al 0.3 Ti 1.7 (PO4)3, etc.), garnet type (Li7La3Zr2O 12 (LLZ) etc. Among them, NASICON type is preferred.

[0501] The volume average particle size of the oxide-based solid electrolyte is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.03 μm or more. As an upper limit, it is preferably 100 μm or less, more preferably 50 μm or less. It should be noted that the average particle size of the oxide-based solid electrolyte particles is measured in the following order. In a 20 ml sample bottle, the oxide-based solid electrolyte particles are diluted with water (heptane is used in the case of substances that are unstable to water) to adjust to a dispersion of 1% by mass. The diluted dispersed sample is irradiated with 1 kHz ultrasound for 10 minutes and then used in the test immediately. Using this dispersion sample, a laser diffraction / scattering particle size distribution analyzer LA-920 (manufactured by HORIBA) is used to obtain data 50 times at a temperature of 25°C using a quartz dish for measurement to obtain the volume average particle size. Other detailed conditions, etc., may be referred to the description of JIS Z 8828: 2013 "Particle Size Analysis-Dynamic Light Scattering Method" as needed. Five samples are prepared for each level, and their average value is adopted.

[0502] The solid-state secondary battery may include a separator between the positive electrode and the negative electrode. Examples of the separator include porous films such as polyethylene and polypropylene, and nonwoven fabrics such as nonwoven fabrics made of resins such as polypropylene and nonwoven fabrics made of glass fiber.

[0503] The solid-state secondary battery may further include a battery case. The shape of the battery case is not particularly limited as long as it can accommodate the positive electrode, negative electrode, solid electrolyte layer, etc. Specifically, cylindrical, rectangular, button-shaped, and laminated types may be used.

[0504] The solid-state secondary battery can be manufactured, for example, by sequentially stacking a positive electrode, a solid electrolyte layer, and a negative electrode and pressing the stacked layers.

[0505] While the embodiments have been described above, it should be understood that various changes in form and details may be made without departing from the spirit and scope of the claims.

[0506] Example

[0507] Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0508] Various physical properties were measured by the following methods.

[0509] <Average Primary Particle Size>

[0510] A TFE polymer aqueous dispersion was diluted with water to a solids concentration of 0.15% by mass. The transmittance per unit length of the resulting diluted emulsion at 550 nm was measured, along with the number-based length-average primary particle size determined by measuring the orientation diameter using a transmission electron microscope photograph. A calibration curve was created. The average primary particle size was determined from the measured transmittance of each sample at 550 nm using this calibration curve.

[0511] <Polymer Solids Concentration>

[0512] 1 g of a TFE-based polymer aqueous dispersion was dried in a blower dryer at 150° C. for 60 minutes, and the ratio of the mass of the heating residue to the mass of the aqueous dispersion (1 g) was expressed as a percentage. This ratio was used as the polymer solid content concentration.

[0513] <Content of Modified Monomer>

[0514] Regarding the CTFE content, the infrared absorbance at 957 cm was determined by FT-IR measurement of a film disc made by compression molding a TFE polymer powder or composition. -1 Absorbance at 2360 cm -1 The CTFE content was calculated by multiplying the absorbance ratio at 0.58.

[0515] Regarding the HFP content, the TFE polymer powder or composition is molded into a film disc, and the infrared absorbance at 982 cm is obtained by FT-IR measurement of the film disc. -1 Absorbance at 935 cm -1 The HFP content was calculated by multiplying the absorbance ratio at 0.3.

[0516] <Standard Specific Gravity (SSG)>

[0517] The measurement was performed by the water displacement method according to ASTM D 792 using a sample molded according to ASTM D 4895 89.

[0518] <Extrusion Pressure>

[0519] 60 g of TFE-based polymer and 12.3 g of hydrocarbon oil (trade name: Isopar G (registered trademark), manufactured by ExxonMobil) as an extrusion aid were mixed in a polyethylene container for 3 minutes. At room temperature (25±2°C), the mixture was filled into the barrel of the extruder, and a load of 0.47 MPa was applied to the piston inserted into the barrel and maintained for 1 minute. Then, it was extruded from the hole at a punching speed of 20 mm / min. The ratio of the cross-sectional area of ​​the barrel to the cross-sectional area of ​​the hole was 1000. In the second half of the extrusion operation, the value obtained by dividing the load (N) when the pressure reaches a balanced state by the cross-sectional area of ​​the barrel was used as the extrusion pressure (MPa).

[0520] <Endothermic Peak Temperature>

[0521] The endothermic peak temperature is the temperature corresponding to the respective minimum points in region (A) and region (B) of the heat of fusion curve when a TFE-based polymer powder or composition that does not have a history of heating to a temperature of 300°C or higher is heated at a rate of 2°C / min using a differential scanning calorimeter [DSC].

[0522] <Endothermic Peak Intensity>

[0523] In the measurement of the endothermic peak temperature, the minimum point of the heat of fusion curve in the measurement is defined as (a), and the intersection point of a straight line passing through the minimum point (a) and perpendicular to the horizontal axis (temperature) and a straight line connecting the points of 305°C and 355°C on the heat of fusion curve is defined as (b). The distance between the minimum point (a) and the intersection point (b) is defined as the endothermic peak intensity.

[0524] <Endothermic Peak Intensity Ratio>

[0525] The value obtained by dividing the intensity of the endothermic peak in the region (A) by the intensity of the endothermic peak in the region (B) is used.

[0526] <Stretchable>

[0527] According to the description of Japanese Patent Application Publication No. 2002-201217, 21.7 g of lubricant (trade name: Isopar H (registered trademark), manufactured by ExxonMobil) is added to 100 g of TFE-based polymer powder and mixed for 3 minutes. After the above mixture is placed in a thermostatic bath at 25°C for 2 hours, the paste is extruded through a hole (diameter 2.5 mm, land length 1.1 cm, introduction angle 30°) at 25°C under the conditions of a compression ratio (ratio of the cross-sectional area of ​​the die inlet to the cross-sectional area of ​​the die outlet) of 100 and an extrusion speed of 51 cm / min to obtain a strip. The obtained strip is dried at 230°C for 30 minutes to remove the lubricant. The dried strip is cut into appropriate lengths, each end is fixed so that the distance between the chucks is 3.8 cm, and heated to 300°C in an air circulation oven. Next, the chucks are separated at a stretching speed of 1000% / second until the separation distance corresponds to a total stretching of 2400%. "Total stretch" is the increase in length due to stretching relative to the strip length before the tensile test (100%). If the strip does not break during stretching, it is considered stretchable, and if it breaks, it is considered non-stretchable.

[0528] <Moisture content>

[0529] The mass of approximately 20 g of TFE polymer powder or composition was measured before and after heating at 150°C for 2 hours, and the mass was calculated according to the following formula: 3 samples were taken, the mass was calculated for each sample, and the average value was calculated and used.

[0530] Water content (mass %) = [(mass of TFE polymer powder or composition before heating (g)) - (mass of TFE polymer powder or composition after heating (g))] / (mass of TFE polymer powder or composition before heating (g)) × 100

[0531] <Content of Perfluoroether Carboxylic A and B>

[0532] Weigh 1 g of the TFE-based polymer composition, add 10 g (12.6 ml) of methanol, and perform ultrasonic treatment for 60 minutes to obtain an extract. The obtained extract is subjected to LC / MS / MS measurement. Fluorine-containing compounds in the extract are measured using a liquid chromatography mass spectrometer (Waters, LC-MS ACQUITY UPLC / TQD). The measurement equipment composition and LC-MS measurement conditions are shown in Table 1. Using an aqueous solution of a fluorine-containing compound with a known concentration, aqueous solutions with a content of more than 5 levels are prepared, and LC / MS analysis of the aqueous solution of each content is performed. The relationship between the content and the area of ​​the region relative to the content is plotted to draw a calibration curve. Using the above calibration curve, the area of ​​the LC / MS chromatogram of the fluorine-containing compound in the extract is converted into the content of the fluorine-containing compound.

[0533] It should be noted that the lower limit of detection in this measurement method is 10 mass ppb.

[0534] [Table 1]

[0535]

[0536] <Average Aspect Ratio of Powder>

[0537] The TFE polymer powder or composition is spread thinly on a black paper in air without shearing the powder, and observed under a microscope. The average value of the ratio of the major axis to the minor axis of at least 100 randomly selected particles is determined.

[0538] A white solid A (ammonium salt of perfluoroethercarboxylic acid A) was obtained by the method described in Synthesis Example 1 of International Publication No. 2021 / 045228.

[0539] The following fluorinated surfactants having a molecular weight of 1000 or less were prepared.

[0540] Perfluoroether carboxylic acid B ammonium salt: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., perfluoro(2-methyl-3-oxahexanoic acid)ammonium, structural formula: CF3CF2CF2OCF(CF3)COONH4

[0541] Prepare the following hydrophilic monomers.

[0542] Hydrophilic monomer: 2,3,3,3-tetrafluoro-2-[(1,1,2-trifluoro-2-propenyl)oxy]-ammonium propionate, structural formula: CH2=CFCF2OCF(CF3)COONH4

[0543] Synthesis example 1

[0544] A 6-liter stainless steel autoclave equipped with a stainless steel stirring blade and a temperature control jacket was charged with 3580 g of deionized water, 100 g of paraffin wax, and 5.4 g of white solid A. The autoclave was heated to 70°C while the atmosphere was purged with nitrogen to remove oxygen. 0.06 g of HFP was then introduced with TFE. TFE was then added to a pressure of 0.78 MPaG, and the temperature was maintained at 70°C while stirring. Next, an aqueous solution of 15.4 mg of ammonium persulfate dissolved in 20 g of water was introduced with TFE to initiate a polymerization reaction. While the pressure in the system decreased as the polymerization reaction progressed, additional TFE was added to maintain the temperature at 70°C and the pressure at 0.78 MPaG.

[0545] When 430 g of TFE was consumed from the start of polymerization, an aqueous solution obtained by dissolving 18.0 mg of hydroquinone as a free radical scavenger in 20 g of water was pressurized with TFE. Polymerization continued thereafter. When the amount of TFE polymerized reached approximately 1540 g from the start of polymerization, stirring and the supply of TFE were stopped, and the gas in the system was immediately released to return it to normal pressure, thereby terminating the polymerization reaction. The aqueous dispersion was removed and cooled, and the paraffin was separated to obtain a TFE-based polymer aqueous dispersion. The obtained TFE-based polymer aqueous dispersion had an average primary particle size of 246 nm and a solid content concentration of 29.8% by mass.

[0546] Production Example 1

[0547] The TFE polymer aqueous dispersion obtained in Synthesis Example 1 was diluted to a solid content concentration of 13% by mass, and the TFE polymer was coagulated while being stirred in a container. The TFE polymer was then filtered with water to obtain a TFE polymer wet powder.

[0548] The obtained TFE polymer wet powder was placed on a stainless steel mesh tray and heat-treated in a hot air circulation electric furnace at 180° C. After 18 hours, the mesh tray was removed and air-cooled to obtain TFE polymer powder.

[0549] The obtained TFE-based polymer powder had an HFP content of 0.027% by mass and an SSG of 2.150.

[0550] Synthesis example 2

[0551] Into a 6-liter stainless steel autoclave equipped with a stainless steel stirring blade and a temperature control jacket were placed 3480 g of deionized water, 100 g of paraffin wax, and 5.3 g of white solid A. The autoclave was heated to 70°C while nitrogen was purged to remove oxygen. TFE was then introduced to a pressure of 0.78 MPaG, and the temperature was maintained at 70°C while stirring. Next, an aqueous solution of 15.0 mg of ammonium persulfate dissolved in 20 g of water was introduced with TFE to initiate a polymerization reaction. As the polymerization reaction progressed, the pressure in the system decreased, but additional TFE was added to maintain the temperature and pressure at 70°C and 0.78 MPaG.

[0552] When 400 g of TFE was consumed from the start of polymerization, an aqueous solution prepared by dissolving 18.0 mg of hydroquinone as a free radical scavenger in 20 g of water was pressurized with TFE. Polymerization continued thereafter. When the amount of TFE polymerized reached approximately 1200 g from the start of polymerization, stirring and the supply of TFE were stopped, and the gas in the system was immediately released to return it to normal pressure, thereby terminating the polymerization reaction. The aqueous dispersion was removed, cooled, and the paraffin was separated to obtain a TFE-based polymer aqueous dispersion. The resulting TFE-based polymer aqueous dispersion had an average primary particle size of 310 nm and a solids concentration of 25.3% by mass.

[0553] Production Example 2

[0554] The TFE polymer aqueous dispersion obtained in Synthesis Example 2 was diluted to a solid content concentration of 13% by mass, and the TFE polymer was coagulated while being stirred in a container, and then filtered with water to obtain a TFE polymer wet powder.

[0555] The obtained TFE polymer wet powder was placed on a stainless steel mesh tray and heat-treated in a hot air circulation electric furnace at 180° C. After 20 hours, the mesh tray was removed and air-cooled to obtain TFE polymer powder.

[0556] The SSG of the obtained TFE-based polymer powder was 2.156.

[0557] Synthesis example 3

[0558] A 6-liter stainless steel autoclave equipped with a stainless steel stirring blade and a temperature control jacket was charged with 3580 g of deionized water, 100 g of paraffin wax, and 5.4 g of white solid A. The autoclave was heated to 80°C while the atmosphere was purged with nitrogen to remove oxygen. After adding 1.20 g of CTFE, TFE was further introduced to a pressure of 0.78 MPaG. The temperature was maintained at 80°C while stirring. Next, an aqueous solution of 360 mg of succinyl peroxide dissolved in 20 g of water and an aqueous solution of 10 mg of ammonium persulfate dissolved in 20 g of water were introduced with TFE to initiate polymerization. While the pressure in the system decreased as the polymerization proceeded, additional TFE was added to maintain the temperature at 80°C and the pressure at 0.78 MPaG. When 1530 g of TFE had been consumed since the start of polymerization (90% conversion), 4.2 g of CTFE was introduced with TFE. Polymerization was continued thereafter. When the amount of TFE polymerized reached about 1700 g from the start of polymerization, stirring and the supply of TFE were stopped, and the gas in the system was immediately released to return it to normal pressure, thereby terminating the polymerization reaction. The aqueous dispersion was taken out and cooled, and then paraffin was separated to obtain a TFE-based polymer aqueous dispersion. The obtained TFE-based polymer aqueous dispersion had an average primary particle size of 241 nm and a solid content of 32.0% by mass. The particles of the TFE-based polymer obtained above had a core-shell structure.

[0559] Production Example 3

[0560] The TFE polymer aqueous dispersion obtained in Synthesis Example 3 was diluted to a solid content concentration of 13% by mass. The TFE polymer was coagulated while being vigorously stirred in a container and then filtered with water to obtain a TFE polymer wet powder.

[0561] The obtained TFE polymer wet powder was placed on a stainless steel mesh tray and heat-treated in a hot air circulation electric furnace at 145° C. After 18 hours, the mesh tray was removed and air-cooled to obtain TFE polymer powder.

[0562] The obtained TFE-based polymer powder had a CTFE content of 0.23% by mass, an SSG of 2.170, and an extrusion pressure of 36 MPa.

[0563] Synthesis example 4

[0564] A TFE-based polymer aqueous dispersion was obtained in the same manner as in Synthesis Example 2, except that 5.3 g of white solid A was replaced with 15.75 g of ammonium salt of perfluoroethercarboxylic acid B and 35 mg of the hydrophilic monomer. The obtained TFE-based polymer aqueous dispersion had an average primary particle size of 295 nm and a solid content concentration of 26.5% by mass.

[0565] Production Example 4

[0566] The TFE-based polymer aqueous dispersion obtained in Synthesis Example 4 was subjected to the same procedure as in Preparation Example 2 to obtain a TFE-based polymer powder.

[0567] The SSG of the obtained TFE-based polymer powder was 2.159.

[0568] Synthesis example 5

[0569] A TFE-based polymer aqueous dispersion was obtained in the same manner as in Preparation Example 1, except that 5.4 g of white solid A was replaced with 16 g of ammonium salt of perfluoroethercarboxylic acid B and 30 mg of the hydrophilic monomer. The obtained TFE-based polymer aqueous dispersion had an average primary particle size of 245 nm and a solid content of 31.8% by mass.

[0570] Production Example 5

[0571] The TFE-based polymer aqueous dispersion obtained in Synthesis Example 5 was subjected to the same procedure as in Production Example 3 to obtain a TFE-based polymer powder.

[0572] The obtained TFE-based polymer powder had a CTFE content of 0.23% by mass, an SSG of 2.172, and an extrusion pressure of 37 MPa.

[0573] Production example 1

[0574] The aqueous TFE polymer dispersions obtained in Synthesis Example 1 and Synthesis Example 3 were mixed at a solid content mass ratio (Synthesis Example 1: Synthesis Example 3) of 75:25, and diluted to a solid content concentration of 13% by mass. The TFE polymer was coagulated in a container while being vigorously stirred, and then filtered with water to obtain a TFE polymer wet powder. The obtained TFE polymer wet powder was placed on a stainless steel mesh tray (placement amount: 2.0 g / cm 2 ), and heat-treated the mesh tray in a hot air circulation electric furnace at 180° C. After 18 hours, the mesh tray was removed and air-cooled to obtain a TFE-based polymer composition 1.

[0575] The resulting TFE-based polymer composition 1 had a CTFE content of 0.06% by mass and an HFP content of 0.020% by mass. Furthermore, the composition exhibited endothermic peak temperatures of 338°C and 343°C, an endothermic peak intensity ratio of 0.98, and was stretchable. The composition also had a water content of 0.000% by mass, a perfluoroether carboxylic acid A content of less than 10 ppb by mass, and an average aspect ratio of the powder of 1.1.

[0576] Production example 2

[0577] A TFE-based polymer composition 2 was obtained in the same manner as in Preparation Example 1 except that the solid content mass ratio of the TFE-based polymer aqueous dispersion was changed to 50:50.

[0578] The obtained TFE-based polymer composition 2 had a CTFE content of 0.10% by mass and an HFP content of 0.014% by mass. Furthermore, the composition had endothermic peak temperatures of 337° C. and 343° C., an endothermic peak intensity ratio of 1.44, and was stretchable. The composition had a water content of 0.000% by mass, a perfluoroether carboxylic acid A content of less than 10 ppb by mass, and an average aspect ratio of the powder of 1.3.

[0579] Production example 3

[0580] A TFE-based polymer composition 3 was obtained in the same manner as in Preparation Example 2, except that the TFE-based polymer aqueous dispersion used was changed from Synthesis Example 1 to Synthesis Example 2.

[0581] The resulting TFE-based polymer composition 3 had a CTFE content of 0.10% by mass. Furthermore, the composition had endothermic peak temperatures of 337°C and 343°C, an endothermic peak intensity ratio of 1.36, and was stretchable. The composition also had a water content of 0.000% by mass, a perfluoroether carboxylic acid A content of less than 10 ppb by mass, and an average aspect ratio of the powder of 1.2.

[0582] Production example 4

[0583] TFE-based polymer composition 4 was obtained in the same manner as in Preparation Example 3 except that the mesh tray was replaced with a flat tray (a tray with no air permeability on the bottom and sides), the drying temperature was changed from 180°C to 145°C, and the drying time was changed from 18 hours to 5 hours.

[0584] The obtained TFE polymer composition 4 had a CTFE content of 0.10% by mass, endothermic peak temperatures of 337° C. and 343° C., an endothermic peak intensity ratio of 1.36, a water content of 0.121% by mass, and an average aspect ratio of the powder of 1.3.

[0585] Production example 5

[0586] The aqueous TFE polymer dispersions obtained in Synthesis Examples 4 and 5 were mixed at a solids mass ratio of 50:50 (Synthesis Example 4:Synthesis Example 5), diluted to a solids concentration of 13% by mass, and coagulated in a container while vigorously stirring. The resulting TFE polymer powder was then filtered with water to obtain a wet TFE polymer powder. The resulting wet TFE polymer powder was placed on a stainless steel flat tray and heat-treated in a hot air circulation electric furnace at 145°C. After 18 hours, the flat tray was removed and air-cooled to obtain TFE polymer composition 5.

[0587] The resulting TFE-based polymer composition 5 had a CTFE content of 0.10% by mass, endothermic peak temperatures of 337°C and 343°C, an endothermic peak intensity ratio of 1.36, and was stretchable. It also had a water content of 0.016% by mass, a perfluoroether carboxylic acid B content of 160 ppb by mass, and an average aspect ratio of the powder of 1.1.

[0588] Production example 6

[0589] The TFE polymer powders obtained in Preparation Example 2 and Preparation Example 3 were mixed at a mass ratio of 50:50 (Preparation Example 2:Preparation Example 3) using a blender (Warning Blender 7012S, manufactured by Warning GmbH) at a stirring speed of 3100 rpm for 1 minute to obtain TFE polymer composition 6.

[0590] The resulting TFE-based polymer composition 6 had a CTFE content of 0.10% by mass, endothermic peak temperatures of 337° C. and 343° C., an endothermic peak intensity ratio of 1.35, a water content of 0.001% by mass, a perfluoroether carboxylic acid A content of less than 10 ppb by mass, and an average aspect ratio of the powder of 2.6.

[0591] Production example 7

[0592] The wet powder obtained in Production Example 2 was placed on a flat tray and heat-treated in a hot air circulation electric furnace at 180° C. After 5 hours, the flat tray was removed and air-cooled to obtain TFE-based polymer powder 7.

[0593] The obtained TFE-based polymer powder 7 had an endothermic peak temperature of 344° C., a water content of 0.126% by mass, and an average aspect ratio of the powder of 1.2.

[0594] Using each TFE-based polymer powder or composition obtained above, evaluation was performed by the following method.

[0595] Evaluation of batteries containing electrolytes

[0596] The mixed tablets of Examples 1 to 4, A1, A2, and Comparative Example 1 were prepared, evaluated, and evaluated as batteries using the following procedures.

[0597] <Production of Positive Electrode Mixture Sheet>

[0598] The active material and conductive additive were weighed and placed in a V-type mixer. Mixing was carried out at 37 rpm for 10 minutes to obtain a mixture of the active material and conductive additive. A weighed amount of binder (TFE-based polymer powder or composition) was then added to the mixture and thoroughly cooled in a thermostatic bath at 5°C. The mixture of active material, conductive additive, and binder was then placed in a Henschel mixer and homogenized at 1000 rpm for 3 minutes.

[0599] The mixture was then heated to 50°C in a thermostatic bath and then processed in a pressurized kneader (D1-5, manufactured by Japan Spindle Co., Ltd.) for 5 minutes (32 rpm, heater at 50°C, pressure of 0.5 MPa) to promote fibrillation and obtain a cohesive, bulky electrode mixture. The bulked electrode mixture was then placed in a Henschel mixer for re-grinding and processed at 300 rpm for 1 minute to obtain an electrode mixture.

[0600] The electrode mixture is placed between parallel metal rollers (temperature: 80°C, rotation speed: 1 m / min) and rolled to produce an electrode mixture sheet. The rolled sheet is then folded in half and roughly crushed. The electrode mixture is then placed between metal rollers (temperature: 80°C, rotation speed: 1 m / min) and rolled to produce an electrode mixture sheet with even higher strength.

[0601] Thereafter, the electrode mixture sheet was placed in a roller press and the gap was adjusted to adjust the thickness of the final positive electrode mixture layer to 90 μm.

[0602] Table 2 shows the material types and compositions.

[0603] [Table 2]

[0604]

[0605] denka Li-400: Carbon black produced by Denka

[0606] <Evaluation of Powder Agglomeration>

[0607] The electrode mixture before being fed into the parallel metal rollers was sieved for 30 seconds using a 0.18 mm mesh (JIS-Z8801) sieve. A value of × was given if agglomerates remained on the sieve, and a value of ○ was given if all agglomerates passed through. The results are shown in Table 3.

[0608] <Measurement of Positive Electrode Mixture Sheet Strength>

[0609] Cut out the above-mentioned positive electrode mixture sheet and make a long strip test piece with a width of 4 mm. Use a tensile testing machine (AGS-100NX manufactured by Shimadzu Corporation) to measure at 100 mm / min. The distance between the chucks is set to 30 mm. Displacement is applied until fracture, and the maximum stress of the measurement result is used as the strength of each sample. The test is carried out with N=8 and the average value is calculated. Comparative Example 1 is taken as 100% for comparison. In addition, the coefficient of variation at this time is calculated to evaluate the deviation. The results are shown in Table 3.

[0610] <Evaluation of Flexibility of Positive Electrode Mixture Sheet (Bending Test)>

[0611] The prepared electrode mixture sheets were cut into 4 cm wide and 10 cm long test pieces. These test pieces were then wound around a 2 mm diameter round rod and visually inspected for any damage, such as scratches or cracks. No damage, such as scratches, or cracks, was observed in Examples 1 to 4, A1, and A2.

[0612] <Production of positive electrode>

[0613] The positive electrode mixture sheet was bonded to a 20 μm aluminum foil as follows.

[0614] The adhesive used was a slurry of polyvinylidene fluoride (PVDF) dissolved in N-methylpyrrolidone (NMP) and carbon black dispersed in a ratio of 80:20. This adhesive was applied to aluminum foil and dried on a hot plate at 120°C for 15 minutes to form a current collector with an adhesive layer.

[0615] Thereafter, the positive electrode mixture sheet was placed on the current collector with the adhesive layer, and the positive electrode mixture sheet and the current collector were bonded using a roller press heated to 100° C., cut into desired sizes, and tabs were attached to prepare the positive electrode.

[0616] <Production of negative electrode>

[0617] 1 part by mass of an aqueous dispersion of sodium carboxymethylcellulose (1% by mass) and 1 part by mass of an aqueous dispersion of styrene-butadiene rubber (50% by mass) as thickeners and binders were added to 98 parts by mass of a carbonaceous material (graphite), and mixed using a disperser to form a slurry. The resulting slurry was applied to a 10 μm thick copper foil and dried. The slurry was then rolled using a press and cut to the desired size. The tabs were then attached to form the negative electrode.

[0618] <Preparation of Electrolyte>

[0619] As an organic solvent, a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC:EMC=30:70 (volume ratio)) was measured in a sample bottle, and 1% by mass of fluoroethylene carbonate (FEC) and vinylene carbonate (VC) were dissolved therein. A mixed solution was prepared. LiPF6 salt was mixed into the mixed solution at 23°C so that the concentration in the electrolyte was 1.1 mol / L, thereby obtaining a non-aqueous electrolyte.

[0620] <Production of Aluminum Laminated Batteries>

[0621] The positive electrode is placed opposite the negative electrode via a 20 μm thick microporous polyethylene film (diaphragm), and the non-aqueous electrolyte obtained above is injected. After the non-aqueous electrolyte fully penetrates the diaphragm, etc., it is sealed and pre-charged and aged to produce a lithium-ion secondary battery.

[0622] <Evaluation of Storage Characteristics (Remaining Capacity Ratio, Gas Generation)>

[0623] The lithium ion secondary battery manufactured as described above was charged at 25°C with a constant current-constant voltage (CC / CV) charge (0.1C cut-off) to 4.3V and then discharged at a constant current of 0.33C to 3V. This was considered one cycle, and the initial discharge capacity was determined from the discharge capacity of the third cycle.

[0624] After evaluating the initial discharge capacity, the battery was again subjected to CC / CV charging (0.1C cutoff) at 25°C to 4.3V, and the battery volume was determined using the Archimedean method. After determining the battery volume, the battery was stored at 60°C for 30 days. After sufficient cooling, the battery volume was then determined at 25°C. The gas generation amount was calculated from the difference in battery volume before and after the storage test. The gas generation amount in Comparative Example 1 was set to 100 for comparison purposes.

[0625] After the amount of gas generated was determined, the battery was discharged at 25° C. and 0.33 C to 3 V, and the remaining capacity was determined.

[0626] The ratio of the remaining capacity after high-temperature storage to the initial discharge capacity was determined and defined as the remaining capacity ratio (%).

[0627] (Remaining capacity) / (Initial discharge capacity)×100=Remaining capacity rate (%)

[0628] The results are shown in Table 3.

[0629] [Table 3]

[0630] Agglutination strength Coefficient of variation Remaining capacity rate Gas production Comparative Example 1 × 100％ 28％ 69％ 100 Example 1 ○ 162％ 15％ 74％ 85 Example 2 ○ 143％ 12％ 73％ 86 Example 3 ○ 158％ 13％ 74％ 85 Example 4 ○ 123％ 23％ 70％ 98 Example A1 ○ 138％ 14％ 73％ 89 Example A2 ○ 112％ 20％ 74％ 85

[0631] Evaluation of solid electrolyte mixture tablets

[0632] The following procedures were used to prepare and evaluate the combined tablets of Examples 5 to 8 and Comparative Example 2. Preparation and evaluation were performed under an argon atmosphere.

[0633] <Preparation of Solid Electrolyte Mixture Sheets>

[0634] The weighed binder (TFE-based polymer powder or composition) was sufficiently cooled in a thermostatic bath at 5° C., then placed in a Henschel mixer and subjected to a grinding treatment at 300 rpm for 2 minutes.

[0635] The crushed binder and solid electrolyte were weighed separately, and then sufficiently cooled in a thermostatic bath at 5° C. The mixture was then placed in a Henschel mixer and processed at 300 rpm for 1 minute to homogenize the mixture.

[0636] Thereafter, the mixture was sufficiently heated in a thermostatic bath at 40° C. and then treated with a Henschel mixer at 1000 rpm for 1 minute to promote fibrillation, thereby obtaining an electrolyte mixture.

[0637] The electrode mixture is placed between parallel metal rollers (temperature: 80°C, rotation speed: 1 m / min) and rolled to produce an electrolyte mixture sheet. The rolled sheet is then folded in half and roughly crushed. The electrolyte mixture is then placed between metal rollers (temperature: 80°C, rotation speed: 1 m / min) and rolled to produce a stronger electrolyte mixture sheet.

[0638] Thereafter, the electrolyte mixture sheet was placed in a roller press and the gap was adjusted to adjust the thickness of the final electrolyte mixture sheet to 120 μm.

[0639] Table 4 shows the material types and compositions.

[0640] [Table 4]

[0641]

[0642] <Measurement of Strength of Solid Electrolyte Mixture Sheet (Tensile Test)>

[0643] Cut out the above-mentioned solid electrolyte mixture sheet and make a 4mm wide strip test piece. Use a tensile testing machine (AGS-100NX manufactured by Shimadzu Corporation) to measure at 100mm / min. The distance between the chucks is set to 30mm. Displacement is given until it breaks, and the maximum stress of the measurement result is used as the strength of each sample. Test with N=8 and find the average value. Comparative Example 2 is taken as 100% for comparison. The results are shown in Table 5.

[0644] <Evaluation of Flexibility of Solid Electrolyte Mixture Sheet (Bending Test)>

[0645] Cut the prepared solid electrolyte mixture sheet into 4cm wide and 10cm long test pieces. Then, after winding these test pieces on a Φ10mm round rod, visually check the test pieces to confirm whether there are any damages such as scratches and cracks. If no damage is found, use a thinner Φ5mm round rod to test and confirm the damage. If no damage is still found, use an even thinner Φ2mm round rod to test and confirm the damage. The results are classified as A to D.

[0646] A: No damage with Φ2mm rod

[0647] B: Φ2mm rod is damaged

[0648] C: Damage with Φ5mm rod

[0649] D: Φ10mm rod is damaged

[0650] The results are shown in Table 5.

[0651] <Ionic Conductivity of Solid Electrolyte Mixture Sheet>

[0652] The solid electrolyte mixture sheet was cut into appropriate sizes and gold was evaporated on both sides. After that, a 10 mm Φ round solid electrolyte mixture sheet was punched out with a punch and placed in a pressure cell. The screws of the cell were tightened with 8 N, and the electrodes were removed from the top and bottom of the cell. A schematic diagram of the cross section of the pressure cell used is shown in Figure 1 .

[0653] The sample was measured using an impedance device manufactured by Dongyang Technology at 25°C, AC amplitude modulation of 10mV, and frequency of 5×10 6 The ionic conductivity was measured at 0.1 Hz.

[0654] The results are shown in Table 5.

[0655] [Table 5]

[0656]

[0657] Evaluation of solid electrolyte cathode mixture sheets

[0658] The following procedures were used to prepare and evaluate the mixed tablets of Examples B1 and B2 and Comparative Example 3. Preparation and evaluation were performed under an argon atmosphere.

[0659] <Preparation of Solid Electrolyte Electrode Mixture Sheets>

[0660] The active material and conductive additive were weighed and placed in a V-type mixer, where they were mixed at 37 rpm for 10 minutes to obtain a mixture of the active material and conductive additive. A weighed binder (TFE-based polymer powder or composition) was then added to the mixture. After sufficient cooling in a thermostatic bath at 5°C, the mixture was placed in a Henschel mixer at 2800 rpm for 10 minutes to disperse the mixture and fibrillate the TFE composition, resulting in a solid electrolyte electrode mixture.

[0661] The electrode mixture is placed between parallel metal rollers (temperature: 80°C, rotation speed: 0.5m / min) and rolled to obtain a solid electrolyte electrode mixture sheet. Again, the resulting rolled sheet is folded in half and roughly crushed, and the solid electrolyte electrode mixture is placed between metal rollers (temperature: 80°C, rotation speed: 0.5m / min) and rolled. Through this process, fibrillation is promoted, and a strong solid electrolyte electrode mixture sheet is obtained. Thereafter, the solid electrolyte electrode mixture sheet is placed in a roller press and the thickness of the solid electrolyte electrode mixture sheet is adjusted to 150μm.

[0662] Table 6 shows the material types and compositions.

[0663] [Table 6]

[0664]

[0665] denka Li-400: Carbon black produced by Denka

[0666] <Measurement of the Strength of Solid Electrolyte Electrode Mixture Sheets (Tensile Test)>

[0667] Cut out the above-mentioned solid electrolyte mixture electrode sheet and make a 4mm wide strip test piece. Use a tensile testing machine (AGS-100NX manufactured by Shimadzu Corporation) to measure at 100mm / min. The distance between the chucks is set to 30mm. Displacement is given until it breaks, and the maximum stress of the measurement result is used as the strength of each sample. Test with N=8 and find the average value. Comparative Example 3 is taken as 100% for comparison. The results are shown in Table 7.

[0668] <Evaluation of Flexibility of Solid Electrolyte Mixture Sheet (Bending Test)>

[0669] Cut the prepared solid electrolyte electrode mixture sheet into 4cm wide and 10cm long test pieces. Then, after winding these test pieces on a Φ10mm round rod, visually inspect the test pieces to confirm whether there are any damages such as scratches and cracks. If no damage is found, use a thinner Φ5mm round rod to test and confirm the damage. If no damage is still found, use an even thinner Φ2mm round rod to test and confirm the damage. The results are classified as A to D.

[0670] A: No damage with Φ2mm rod

[0671] B: Φ2mm rod is damaged

[0672] C: Damage with Φ5mm rod

[0673] D: Φ10mm rod is damaged

[0674] The results are shown in Table 7.

[0675] [Table 7]

[0676] strength bending test Comparative Example 3 100％ C Example B1 160％ B Example B2 125％ B

[0677] Explanation of symbols

[0678] 1: Screw

[0679] 2: Nut

[0680] 3: Insulation sheet

[0681] 4: Solid electrolyte mixture tablets

[0682] 5: Gold evaporation

[0683] 6: Upper electrode

[0684] 7: Lower electrode

Claims

1. A tetrafluoroethylene polymer composition, which is a tetrafluoroethylene polymer composition for use as a binder for electrochemical devices, wherein: In differential scanning calorimetry analysis, endothermic peaks are present in a region (A) of 330°C or higher and lower than 340°C and a region (B) of 340°C or higher and 350°C or lower.

2. An electrochemical device binder, which is an electrochemical device binder consisting essentially of a tetrafluoroethylene polymer composition, wherein: The tetrafluoroethylene polymer composition has endothermic peaks in a region (A) of 330° C. or higher and lower than 340° C. and a region (B) of 340° C. or higher and 350° C. or lower in differential scanning calorimetry analysis.

3. The binder for electrochemical devices according to claim 2, wherein The tetrafluoroethylene polymer composition has an intensity ratio represented by the intensity of the endothermic peak in the region (A) / the intensity of the endothermic peak in the region (B) of 0.5 or more.

4. The binder for electrochemical devices according to claim 3, wherein The tetrafluoroethylene polymer composition has an intensity ratio represented by the intensity of the endothermic peak in the region (A) / the intensity of the endothermic peak in the region (B) of 0.8 to 2.

0.

5. The binder for electrochemical devices according to any one of claims 2 to 4, wherein The tetrafluoroethylene-based polymer composition includes a tetrafluoroethylene copolymer including a tetrafluoroethylene unit and a modifying monomer unit based on a modifying monomer copolymerizable with tetrafluoroethylene.

6. The binder for electrochemical devices according to claim 5, wherein In the tetrafluoroethylene copolymer, the content of the modified monomer unit is 10% by mass or less based on all polymerized units.

7. The binder for electrochemical devices according to any one of claims 2 to 6, wherein The tetrafluoroethylene polymer composition includes tetrafluoroethylene units and modifying monomer units based on a modifying monomer copolymerizable with tetrafluoroethylene.

8. The binder for electrochemical devices according to claim 7, wherein In the tetrafluoroethylene polymer composition, the content of the modified monomer unit is 0.20% by mass or less relative to all polymerized units.

9. The binder for electrochemical devices according to any one of claims 5 to 8, wherein The modified monomer is a compound represented by the following general formula (I), CX 1 X 2 =CX 3 X 4 (I) Where, X 1 ~X 3 are each independently H or F, X 4 is F, Cl, Rf or O-Rf, and Rf is a perfluorinated organic group.

10. The binder for electrochemical devices according to claim 9, wherein The modifying monomer is at least one selected from the group consisting of chlorotrifluoroethylene and hexafluoropropylene.

11. The binder for an electrochemical device according to any one of claims 2 to 10, wherein The tetrafluoroethylene-based polymer composition is stretchable.

12. The binder for an electrochemical device according to any one of claims 2 to 11, wherein The tetrafluoroethylene polymer composition includes a tetrafluoroethylene copolymer having an extrusion pressure of 75 MPa or less at a compression ratio of 1000.

13. The binder for an electrochemical device according to any one of claims 2 to 12, wherein The tetrafluoroethylene polymer composition is in the form of powder.

14. The binder for an electrochemical device according to any one of claims 2 to 13, wherein The tetrafluoroethylene polymer composition contains substantially no water.

15. The binder for an electrochemical device according to any one of claims 2 to 14, wherein The tetrafluoroethylene polymer composition does not substantially contain a fluorine-containing compound having a molecular weight of 1000 or less.

16. The binder for an electrochemical device according to any one of claims 2 to 15, wherein The content of the fluorine-based polymer is 90% by mass or more based on the tetrafluoroethylene-based polymer composition.

17. The binder for an electrochemical device according to any one of claims 2 to 16, wherein The tetrafluoroethylene polymer composition contains two or more tetrafluoroethylene polymers.

18. The binder for an electrochemical device according to any one of claims 2 to 17, wherein The tetrafluoroethylene polymer in the tetrafluoroethylene polymer composition is polytetrafluoroethylene.

19. The binder for an electrochemical device according to any one of claims 2 to 18, wherein The average aspect ratio of the powder of the fluorine-based polymer composition is 2.5 or less.

20. An electrode mixture comprising the tetrafluoroethylene polymer composition according to claim 1 or the binder for an electrochemical device according to any one of claims 2 to 19, and an electrode active material. The electrode mixture according to claim 20 , which is in the form of a sheet.

22. An electrode comprising the tetrafluoroethylene polymer composition according to claim 1 or the binder for an electrochemical device according to any one of claims 2 to 19, an electrode active material, and a current collector. 23 . A secondary battery comprising the electrode according to claim 22 .

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