Polytetrafluoroethylene composition, binder for electrochemical devices, electrode mixture, electrode, and secondary battery

Abstract

Provided are: a polytetrafluoroethylene composition for a binder for electrochemical devices, wherein the composition can be uniformly mixed with a powder component for electrochemical devices and can yield a mixture sheet that exhibits an excellent strength and flexibility; and a binder for electrochemical devices, an electrode mixture, an electrode, and a secondary battery, in each instance which use this composition. The polytetrafluoroethylene composition is used for binders for electrochemical devices, and contains polytetrafluoroethylene that contains polytetrafluoroethylene particles having a particle diameter of at least 1 µm.

Description

Polytetrafluoroethylene composition, binder for electrochemical device, electrode mixture, electrode, and secondary battery

[0001] The present disclosure relates to a polytetrafluoroethylene composition, a binder for an electrochemical device, an electrode mixture, an electrode, and a secondary battery.

[0002] Secondary batteries such as lithium-ion secondary batteries are used in small, portable electrical and electronic devices such as notebook computers, mobile phones, smartphones, tablet computers, and ultrabooks because of their high voltage, high energy density, low self-discharge, low memory effect, and the ability to be ultra-lightweight, and are also being put into practical use as a wide range of power sources, including on-board power sources for driving automobiles and large-scale stationary power sources. Demand is now being placed on secondary batteries to achieve even higher energy densities, and further improvements in their battery characteristics are being sought.

[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 batteries.

[0006] Patent Publication No. 2017-517862 International Publication No. 2021 / 181887 International Publication No. 2021 / 181888 International Publication No. 2021 / 192541 International Publication No. 2022 / 138942 International Publication No. 2022 / 138939 International Publication No. 2022 / 234227

[0007] An object of the present disclosure is to provide a polytetrafluoroethylene composition for binders for electrochemical devices that can be uniformly mixed with powder components of electrochemical devices and that can give a mixture sheet that is excellent in strength and flexibility, as well as a binder for electrochemical devices, an electrode mixture, an electrode, and a secondary battery that use the same.

[0008] The present disclosure (1) is a polytetrafluoroethylene composition used in a binder for an electrochemical device, the polytetrafluoroethylene composition containing polytetrafluoroethylene containing polytetrafluoroethylene particles having a particle diameter of 1 μm or more.

[0009] The present disclosure (2) is the polytetrafluoroethylene composition according to the present disclosure (1), in which the content of polytetrafluoroethylene including polytetrafluoroethylene particles with a particle size of 1 μm or more is 1% by mass or more and 70% by mass or less relative to the polytetrafluoroethylene composition.

[0010] The present disclosure (3) is a binder for electrochemical devices consisting essentially of a polytetrafluoroethylene composition, wherein the polytetrafluoroethylene composition is a binder for electrochemical devices containing polytetrafluoroethylene containing polytetrafluoroethylene particles having a particle diameter of 1 μm or more.

[0011] The present disclosure (4) is the binder for electrochemical devices according to the present disclosure (3), wherein the polytetrafluoroethylene containing the polytetrafluoroethylene particles having a particle size of 1 μm or more is polytetrafluoroethylene that does not exhibit melt flowability.

[0012] The present disclosure (5) is the binder for electrochemical devices according to the present disclosure (3) or (4), wherein the content of polytetrafluoroethylene including polytetrafluoroethylene particles having a particle size of 1 μm or more is 1% by mass or more and 70% by mass or less relative to the polytetrafluoroethylene composition.

[0013] The present disclosure (6) is the binder for electrochemical devices according to any one of the present disclosures (3) to (5), wherein the content of polytetrafluoroethylene including polytetrafluoroethylene particles having a particle size of 1 μm or more is 1% by mass or more and 50% by mass or less relative to the polytetrafluoroethylene composition.

[0014] The present disclosure (7) is a polytetrafluoroethylene composition used as a binder for an electrochemical device, having a specific surface area of ​​0.5 m ２ / g or more 7.0m ２ / g of polytetrafluoroethylene.

[0015] This disclosure (8) has a specific surface area of ​​1.5 m ２ / g or more 3.5m ２ The polytetrafluoroethylene composition according to the present disclosure (7) contains polytetrafluoroethylene of 0.1g or less.

[0016] The present disclosure (9) is a binder for electrochemical devices consisting essentially of a polytetrafluoroethylene composition, wherein the polytetrafluoroethylene composition has a specific surface area of ​​0.5 m ２ / g or more 7.0m ２ The binder for electrochemical devices contains polytetrafluoroethylene with a molecular weight of less than 1 / g.

[0017] The present disclosure (10) provides a specific surface area of ​​0.5 m ２ / g or more 7.0m ２ / g is a binder for electrochemical devices according to the present disclosure (9), which is polytetrafluoroethylene that does not exhibit melt flowability.

[0018] The present disclosure (11) provides a method for manufacturing the polytetrafluoroethylene composition having a specific surface area of ​​0.5 m ２ / g or more 7.0m ２ The binder for electrochemical devices according to the present disclosure (9) or (10), wherein the polytetrafluoroethylene content is less than 1% by mass or more and 70% by mass or less.

[0019] The present disclosure (12) provides a method for manufacturing the polytetrafluoroethylene composition having a specific surface area of ​​0.5 m ２ / g or more 7.0m ２ The binder for electrochemical devices according to any one of the present disclosures (9) to (11), wherein the polytetrafluoroethylene content is less than 1% by mass or more and 50% by mass or less.

[0020] The present disclosure (13) provides that the polytetrafluoroethylene composition has a specific surface area of ​​1.5 m ２ / g or more 3.5m ２The binder for electrochemical devices according to any one of the present disclosures (9) to (12) contains polytetrafluoroethylene having a molecular weight of 1000 or less.

[0021] The present disclosure (14) is a polytetrafluoroethylene composition used in a binder for an electrochemical device, the polytetrafluoroethylene composition containing polytetrafluoroethylene obtained by suspension polymerization.

[0022] The present disclosure (15) is a binder for electrochemical devices consisting essentially of a polytetrafluoroethylene composition, wherein the polytetrafluoroethylene composition contains polytetrafluoroethylene obtained by suspension polymerization.

[0023] The present disclosure (16) is the binder for electrochemical devices according to the present disclosure (15), wherein the polytetrafluoroethylene obtained by the suspension polymerization is polytetrafluoroethylene that does not exhibit melt flowability.

[0024] The present disclosure (17) is the binder for electrochemical devices according to the present disclosure (15) or (16), wherein the content of the polytetrafluoroethylene obtained by the suspension polymerization relative to the polytetrafluoroethylene composition is 1% by mass or more and 70% by mass or less.

[0025] The present disclosure (18) is the binder for electrochemical devices according to any one of the present disclosures (15) to (17), wherein the content of the polytetrafluoroethylene obtained by the suspension polymerization relative to the polytetrafluoroethylene composition is 1% by mass or more and 50% by mass or less.

[0026] The present disclosure (19) is the binder for electrochemical devices according to any one of the present disclosures (3) to (6), (9) to (13), and (15) to (18), wherein the polytetrafluoroethylene composition has an endothermic peak temperature of 333°C or higher.

[0027] The present disclosure (20) is the binder for electrochemical devices according to any one of the present disclosures (3) to (6), (9) to (13), and (15) to (19), wherein the polytetrafluoroethylene composition is a powder.

[0028] The present disclosure (21) is the binder for electrochemical devices according to any one of the present disclosures (3) to (6), (9) to (13), and (15) to (20), wherein the polytetrafluoroethylene composition is substantially free of moisture.

[0029] The present disclosure (22) is the binder for electrochemical devices according to any one of the present disclosures (3) to (6), (9) to (13), and (15) to (21), wherein the polytetrafluoroethylene composition is substantially free of a fluorine-containing compound having a molecular weight of 1,000 or less.

[0030] The present disclosure (23) is an electrode mixture comprising the polytetrafluoroethylene composition according to the present disclosure (1), (2), (7), (8), or (14), or the binder for electrochemical devices according to any one of the present disclosures (3) to (6), (9) to (13), or (15) to (22), and an electrode active material.

[0031] The present disclosure (24) is the electrode mixture according to the present disclosure (23) in the form of a sheet.

[0032] The present disclosure (25) is an electrode comprising the polytetrafluoroethylene composition according to the present disclosure (1), (2), (7), (8), or (14), or the binder for electrochemical devices according to any one of the present disclosures (3) to (6), (9) to (13), or (15) to (22), an electrode active material, and a current collector.

[0033] The present disclosure (26) is a secondary battery comprising the electrode according to the present disclosure (25).

[0034] According to the present disclosure, it is possible to provide a polytetrafluoroethylene composition for binders for electrochemical devices that can be uniformly mixed with powder components of electrochemical devices and that can give a mixture sheet that is excellent in strength and flexibility, as well as a binder for electrochemical devices, an electrode mixture, an electrode, and a secondary battery that use the same.

[0035] FIG. 2 is a schematic diagram of a cross section of a pressure cell used to measure the ionic conductivity of a solid electrolyte mixture sheet in the examples.

[0036] The present disclosure will be specifically described below.

[0037] The present disclosure provides a polytetrafluoroethylene (PTFE) composition used as a binder for electrochemical devices, the PTFE composition comprising PTFE particles having a particle diameter of 1 μm or more (hereinafter also referred to as PTFE composition (1) of the present disclosure).

[0038] The present disclosure provides a PTFE composition for use in a binder for an electrochemical device, the PTFE composition having a specific surface area of ​​0.5 m ２ / g or more 7.0m ２ / g of PTFE (hereinafter also referred to as PTFE composition (2) of the present disclosure).

[0039] The present disclosure also provides a PTFE composition used as a binder for electrochemical devices, the PTFE composition containing PTFE obtained by suspension polymerization (hereinafter also referred to as PTFE composition (3) of the present disclosure).

[0040] In this specification, unless otherwise specified, the PTFE compositions (1) to (3) of the present disclosure will be collectively referred to as the "PTFE composition of the present disclosure."

[0041] The PTFE composition of the present disclosure, containing a specific PTFE, is less likely to form agglomerates even when kneaded for a long period of time with powder components of electrochemical devices, such as electrode active materials and solid electrolytes, and can be uniformly mixed with the powder components. It can also produce a composite sheet with excellent strength and flexibility. The PTFE composition of the present disclosure also eliminates the need for large amounts of dispersion mediums, such as water or organic solvents, when used as a binder, allowing for a wide range of electrode active materials and solid electrolytes to be combined, which is advantageous in terms of production processes. It also reduces the steps and costs associated with the use of dispersion mediums. Furthermore, the PTFE composition of the present disclosure has excellent binding strength with active materials and electrolytes, allowing for reduced usage.

[0042] The PTFE composition (1) of the present disclosure contains PTFE containing PTFE particles with a particle size of 1 μm or more. Because PTFE has low fibrillation properties, the presence of this PTFE reduces fibrillation of the PTFE composition, making it less likely to form aggregates even when kneaded with the powder components of an electrochemical device for a long period of time. This allows for uniform mixing with the powder components and also improves the strength and flexibility of the composite sheet. The presence or absence of PTFE particles with a particle size of 1 μm or more can be confirmed by determining the particle size of the PTFE particles using a scanning electron microscope (SEM). The particle size is determined by taking an SEM image of the PTFE powder at 2000x magnification and measuring the distance between two horizontal parallel lines that sandwich the particle. The PTFE preferably contains PTFE particles with a particle size of 5 μm or more, more preferably PTFE particles with a particle size of 10 μm or more, even more preferably PTFE particles with a particle size of 15 μm or more, even more preferably PTFE particles with a particle size of 20 μm or more, and also preferably PTFE particles with a particle size of 500 μm or less, more preferably PTFE particles with a particle size of 400 μm or less, even more preferably PTFE particles with a particle size of 300 μm or less, even more preferably PTFE particles with a particle size of 200 μm or less, and particularly preferably PTFE particles with a particle size of 100 μm or less. The PTFE containing PTFE particles with a particle size of 1 μm or more may be PTFE that does not contain PTFE particles with a particle size of less than 1 μm.

[0043] The PTFE containing PTFE particles having a particle diameter of 1 μm or more preferably has a median diameter (d50) of 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, even more preferably 20 μm or more, and preferably 500 μm or less, more preferably 400 μm or less, even more preferably 300 μm or less, even more preferably 200 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less. The median diameter is determined by the following laser diffraction method. A dry method is performed using a HELOS & RODOS system (product name, manufactured by SYMPATEC). The powder to be measured is dispersed with compressed air at a dispersion pressure of 2 bar, and the measurement sensor detects the shadow of the powder to be measured, projected by a laser, to calculate the particle size distribution of the powder to be measured, and the average particle diameter (50% cumulative particle diameter) d50 is determined on a volume basis. d50 is equal to the particle size corresponding to 50% of the integrated particle size distribution.

[0044] The PTFE containing PTFE particles with a particle size of 1 μm or more is preferably a PTFE that does not exhibit melt flowability.In this specification, "not exhibiting melt flowability" means that the melt flow rate (MFR) is less than 0.25 g / 10 min, preferably less than 0.10 g / 10 min, more preferably 0.05 g / 10 min or less, and even more preferably 0.01 g / 10 min or less.The MFR is a value obtained according to ASTM D1238 using a melt indexer, as the mass (g / 10 min) of polymer flowing out of a nozzle with an inner diameter of 2.095 mm and a length of 8 mm at 372 ° C and a load of 5 kg per 10 minutes.

[0045] The PTFE containing the PTFE particles having a particle diameter of 1 μm or more can be mixed more uniformly with the powder components of the electrochemical device, and a composite sheet having even greater strength and flexibility can be obtained. ２ / g or more, and ２ / g or more, and 1.5m ２ / g or more, and more preferably 7.0m ２ / g, and preferably less than 6.5m ２ / g or less, and more preferably 6.0m ２ / g or less, and more preferably 5.5m ２ / g or less, and more preferably 5.0m ２ / g or less, and more preferably 4.5m ２ / g or less, and more preferably 4.0m ２ / g or less, and more preferably 3.5m ２ The specific surface area can be measured by the BET method in accordance with JIS Z8830 using a mixed gas of 30% nitrogen and 70% helium as a carrier gas and cooling with liquid nitrogen.

[0046] In the PTFE composition (1) of the present disclosure, the content of PTFE containing the PTFE particles having a particle size of 1 μm or more is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 10% by mass or more, relative to the PTFE composition, in that it can be mixed more uniformly with the powder components of an electrochemical device and a composite sheet having even greater strength and flexibility can be obtained. Alternatively, it may be 70% by mass or less, preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, even more preferably 35% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less.

[0047] The PTFE containing PTFE particles having a particle size of 1 μm or more can be produced by suspension polymerization. The particle size of PTFE obtained by suspension polymerization is usually larger than that of PTFE obtained by emulsion polymerization.

[0048] In this specification, suspension polymerization refers to polymerization carried out in an aqueous medium in the absence of a surfactant or in the presence of 2000 mass ppm or less of a surfactant relative to the aqueous medium. Details of suspension polymerization will be described later.

[0049] As will be described later, PTFE particles produced by suspension polymerization are often generally scaly in shape, and can be visually distinguished from secondary particles of PTFE particles produced by emulsion polymerization.

[0050] The PTFE particles having a particle size of 1 μm or more are usually scaly PTFE particles.

[0051] The PTFE particles having a particle diameter of 1 μm or more preferably have a diameter-to-thickness ratio (diameter / thickness) of 3.0 or more, more preferably 4.0 or more, and even more preferably 5.0 or more, and preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less. The ratio is determined from the diameter and thickness of the PTFE particles observed with a scanning electron microscope (SEM) and image processing. The ratio is determined for 20 particles, and the average value is used.

[0052] The PTFE composition (1) of the present disclosure preferably further comprises PTFE that does not contain PTFE particles having a particle size of 1 μm or more.The mass ratio of the PTFE containing PTFE particles having a particle size of 1 μm or more to the PTFE that does not contain PTFE particles having a particle size of 1 μm or more is preferably 1 / 99 or more, more preferably 3 / 97 or more, and even more preferably 5 / 95 or more, and is preferably 50 / 50 or less, more preferably 45 / 55 or less, even more preferably 40 / 60 or less, even more preferably 35 / 65 or less, even more preferably 30 / 70 or less, and particularly preferably 25 / 75 or less.

[0053] The PTFE not containing PTFE particles having a particle size of 1 μm or more can be produced by emulsion polymerization, the details of which will be described later.

[0054] The PTFE composition (2) of the present disclosure has a specific surface area of ​​0.5 m ２ / g or more 7.0m ２ Contains less than PTFE / g. Specific surface area: 0.5 m ２ / g or more 7.0m ２PTFE of less than 1.0 m / g has poor fibrillation properties, so the presence of this PTFE reduces fibrillation of the PTFE composition, making it less likely to produce aggregates even when kneaded with the powder components of an electrochemical device for a long period of time. This allows for uniform mixing with the powder components, and also improves the strength and flexibility of the composite sheet. ２ / g or more, and 1.5m ２ / g or more, and 6.5m ２ / g or less, and ２ / g or less, and more preferably 5.5m ２ / g or less, and more preferably 5.0m ２ / g or less, and more preferably 4.5m ２ / g or less, and more preferably 4.0m ２ / g or less, and more preferably 3.5m ２ It is particularly preferable that the SiO2 content is 1 / g or less.

[0055] The specific surface area is 0.5 m ２ / g or more 7.0m ２ PTFE having a viscosity of less than 1 / g is preferably PTFE that does not exhibit melt flowability.

[0056] The specific surface area is 0.5 m ２ / g or more 7.0m ２PTFE having a specific surface area of ​​less than 0.5 m / g can be mixed more uniformly with the powder components of the electrochemical device, and a composite sheet having even greater strength and flexibility can be obtained. Therefore, the composite sheet preferably contains PTFE particles having a particle diameter of 1 μm or more, more preferably PTFE particles having a particle diameter of 5 μm or more, even more preferably PTFE particles having a particle diameter of 10 μm or more, even more preferably PTFE particles having a particle diameter of 15 μm or more, and particularly preferably PTFE particles having a particle diameter of 20 μm or more, and preferably PTFE particles having a particle diameter of 500 μm or less, more preferably PTFE particles having a particle diameter of 400 μm or less, even more preferably PTFE particles having a particle diameter of 300 μm or less, even more preferably PTFE particles having a particle diameter of 200 μm or less, and particularly preferably PTFE particles having a particle diameter of 100 μm or less. ２ / g or more 7.0m ２ The PTFE having a particle size of less than 1 μm may be PTFE that does not contain PTFE particles having a particle size of less than 1 μm.

[0057] The specific surface area is 0.5 m ２ / g or more 7.0m ２ / g of PTFE, the median diameter (d50) is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, even more preferably 20 μm or more, and is preferably 500 μm or less, more preferably 400 μm or less, even more preferably 300 μm or less, even more preferably 200 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less.

[0058] In the PTFE composition (2) of the present disclosure, the specific surface area of ​​0.5 m ２ / g or more 7.0m ２A PTFE content of less than 1% by mass relative to the PTFE composition is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 10% by mass or more, and may be 70% by mass or less, preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, even more preferably 35% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less, in terms of being able to be mixed more uniformly with the powder components of the electrochemical device and being able to obtain a composite sheet having even greater strength and flexibility. ２ / g or more 7.0m ２ The PTFE content of less than 1 μm / g is equivalent to the PTFE content containing the PTFE particles having a particle size of 1 μm or more.

[0059] The specific surface area is 0.5 m ２ / g or more 7.0m ２ PTFE with a specific surface area of ​​less than 1 / g can be produced by suspension polymerization. The specific surface area of ​​PTFE obtained by suspension polymerization is usually lower than that of PTFE obtained by emulsion polymerization.

[0060] The PTFE composition (2) of the present disclosure has a specific surface area of ​​7.0 m ２ It is preferable that the polymer further contains PTFE having a specific surface area of ​​0.5 m / g or more. ２ / g or more 7.0m ２ / g and a specific surface area of ​​7.0 m ２ The mass ratio of PTFE to PTFE of 1 / 99 or more is preferably 1 / 99 or more, more preferably 3 / 97 or more, and even more preferably 5 / 95 or more, and is preferably 50 / 50 or less, more preferably 45 / 55 or less, even more preferably 40 / 60 or less, even more preferably 35 / 65 or less, even more preferably 30 / 70 or less, and particularly preferably 25 / 75 or less.

[0061] The specific surface area is 7.0 m ２ PTFE with a tensile strength of 1 / g or more can be produced by emulsion polymerization.

[0062] The PTFE composition (3) of the present disclosure contains PTFE obtained by suspension polymerization. Since PTFE obtained by suspension polymerization has low fibrillation properties, the presence of this PTFE reduces fibrillation of the PTFE composition, making it less likely to produce aggregates even when kneaded with the powder components of an electrochemical device for a long period of time. This allows the PTFE to be uniformly mixed with the powder components, and also improves the strength and flexibility of the composite sheet.

[0063] The PTFE obtained by the above suspension polymerization is preferably a PTFE that does not exhibit melt flowability.

[0064] The PTFE obtained by the suspension polymerization can be mixed more uniformly with the powder components of the electrochemical device, and can obtain a composite sheet having better strength and flexibility. Therefore, it preferably contains PTFE particles having a particle diameter of 1 μm or more, more preferably PTFE particles having a particle diameter of 5 μm or more, even more preferably PTFE particles having a particle diameter of 10 μm or more, even more preferably PTFE particles having a particle diameter of 15 μm or more, and particularly preferably PTFE particles having a particle diameter of 20 μm or more. It is also preferable to contain PTFE particles having a particle diameter of 500 μm or less, more preferably PTFE particles having a particle diameter of 400 μm or less, even more preferably PTFE particles having a particle diameter of 300 μm or less, even more preferably PTFE particles having a particle diameter of 200 μm or less, and particularly preferably PTFE particles having a particle diameter of 100 μm or less. The PTFE obtained by the suspension polymerization may be PTFE that does not contain PTFE particles having a particle diameter of less than 1 μm.

[0065] The PTFE obtained by the above suspension polymerization preferably has a median diameter (d50) of 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, even more preferably 20 μm or more, and preferably 500 μm or less, more preferably 400 μm or less, even more preferably 300 μm or less, even more preferably 200 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less.

[0066] The PTFE obtained by the suspension polymerization can be more uniformly mixed with the powder components of electrochemical devices, and a composite sheet having more excellent strength and flexibility can be obtained. ２ / g or more, and ２ / g or more, and 1.5m ２ / g or more, and more preferably 7.0m ２ / g, and preferably less than 6.5m ２ / g or less, and more preferably 6.0m ２ / g or less, and more preferably 5.5m ２ / g or less, and more preferably 5.0m ２ / g or less, and more preferably 4.5m ２ / g or less, and more preferably 4.0m ２ / g or less, and more preferably 3.5m ２ It is particularly preferable that the SiO2 content is 1 / g or less.

[0067] In the PTFE composition (3) of the present disclosure, the content of the PTFE obtained by the suspension polymerization is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 10% by mass or more relative to the PTFE composition, in that it can be more uniformly mixed with the powder components of the electrochemical device and a composite sheet having even greater strength and flexibility can be obtained. It may also be 70% by mass or less, preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, even more preferably 35% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less. The content of the PTFE obtained by the suspension polymerization is the content of the PTFE containing the PTFE particles having a particle diameter of 1 μm or more, and the specific surface area of ​​0.5 m ２ / g or more 7.0m ２ This is equivalent to a PTFE content of less than 1 / g.

[0068] The PTFE composition (3) of the present disclosure preferably further comprises the PTFE obtained by emulsion polymerization.The mass ratio of the PTFE obtained by suspension polymerization to the PTFE obtained by emulsion polymerization is preferably 1 / 99 or more, more preferably 3 / 97 or more, even more preferably 5 / 95 or more, and is preferably 50 / 50 or less, more preferably 45 / 55 or less, even more preferably 40 / 60 or less, even more preferably 35 / 65 or less, even more preferably 30 / 70 or less, and particularly preferably 25 / 75 or less.

[0069] The PTFE composition of the present disclosure preferably consists essentially of PTFE (including PTFE other than the specific PTFE described above). This allows the effects of PTFE to be significantly exhibited. "Consisting essentially of PTFE" means that the PTFE content is 95.0% by mass or more relative to the PTFE composition. The PTFE content is preferably 98.0% by mass or more relative to the PTFE composition, more preferably 99.0% by mass or more, even more preferably 99.5% by mass or more, particularly preferably 99.9% by mass or more, and most preferably 99.95% by mass or more. It is also preferable that the PTFE composition of the present disclosure consists essentially of PTFE.

[0070] In the present disclosure, PTFE may be a homopolymer of tetrafluoroethylene (TFE), or may be a modified PTFE that comprises a polymerized unit based on TFE (TFE unit) and a polymerized unit based on a modified monomer copolymerizable with TFE (hereinafter also referred to as "modified monomer unit").The TFE homopolymer refers to a polymerized unit in which the content of modified monomer unit relative to the total polymerized unit is less than 0.0001% by mass.The modified PTFE may comprise 99.0% by mass or more of TFE unit and 1.0% by mass or less of modified monomer unit.Furthermore, the modified PTFE may be composed only of TFE unit and modified monomer unit.

[0071] The modified PTFE can be more uniformly mixed with the powder components of the electrochemical device, and a composite sheet having even greater strength and flexibility can be obtained. Therefore, the content of the modified monomer unit is preferably in the range of 0.0001 to 1.0% by mass relative to the total polymerized units. The lower limit of the content of the modified monomer unit is preferably 0.001% by mass, more preferably 0.010% by mass, even more preferably 0.015% by mass, and particularly preferably 0.020% by mass. The upper limit of the content of the modified monomer unit is preferably 0.80% by mass, more preferably 0.60% by mass, even more preferably 0.50% by mass, even more preferably 0.40% by mass, even more preferably 0.30% by mass, and particularly preferably 0.20% by mass. In this specification, the modified monomer unit refers to a portion of the molecular structure of PTFE that is derived from the modified monomer.

[0072] The content of each of the above-mentioned polymerized units can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis depending on the type of monomer.

[0073] The above-mentioned modified monomer is not particularly limited as long as it can be copolymerized with TFE, and for example, can be listed perfluoroolefin such as hexafluoropropylene (HFP); hydrogen-containing fluoroolefin such as trifluoroethylene, vinylidene fluoride (VDF); perhaloolefin such as chlorotrifluoroethylene (CTFE); perfluorovinyl ether; perfluoroallyl ether; (perfluoroalkyl) ethylene, ethylene etc. In addition, the modified monomer used can be one kind or multiple kinds.

[0074] The perfluorovinyl ether is not particularly limited, and examples thereof include perfluorovinyl ethers represented by the following general formula (A): CF ２ =CF-ORf １ (A) (wherein, Rf １ represents a perfluoroorganic group. ) and perfluorounsaturated compounds represented by the following formula: In this specification, the "perfluoroorganic group" refers to an organic group in which all hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms. The perfluoroorganic group may have an ether oxygen.

[0075] The perfluorovinyl ether may be, for example, a compound represented by the general formula (A) in which Rf １ is a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5.

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

[0077] The perfluorovinyl ether further includes a compound represented by the general formula (A) below, wherein Rf １ is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, Rf １ is of the following formula:

[0078]

[0079] (wherein m represents 0 or an integer of 1 to 4), Rf １ is of the following formula:

[0080]

[0081] (wherein n represents an integer of 1 to 4).

[0082] The (perfluoroalkyl)ethylene [PFAE] is not particularly limited, and examples thereof include (perfluorobutyl)ethylene [PFBE] and (perfluorohexyl)ethylene.

[0083] Examples of perfluoroallyl ethers include those represented by the general formula (B): CF ２ =CF-CF ２ -ORf ２ (B) (wherein, Rf ２ represents a perfluoroorganic group.

[0084] The above Rf ２is preferably a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms. ２ =CF-CF ２ -O-CF ３ , C.F. ２ =CF-CF ２ -O-C ２ F ５ , C.F. ２ =CF-CF ２ -O-C ３ F ７ , and CF ２ =CF-CF ２ -O-C ４ F ９ At least one selected from the group consisting of CF ２ =CF-CF ２ -O-C ２ F ５ , C.F. ２ =CF-CF ２ -O-C ３ F ７ , and CF ２ =CF-CF ２ -O-C ４ F ９ More preferably, at least one selected from the group consisting of CF ２ =CF-CF ２ -O-CF ２ CF ２ CF ３ is more preferred.

[0085] The modified monomer is represented by the following general formula (I): CX １ X ２ =CX ３ X ４ (I) (wherein, X １ ~X ３ are each independently H or F. ４ is F, Cl, Rf or O-Rf, and Rf is a perfluoroorganic group.

[0086] Rf in general formula (I) is preferably a perfluoroalkyl group having 1 to 10 carbon atoms, more preferably a perfluoroalkyl group having 1 to 5 carbon atoms, and even more preferably a perfluoroalkyl group having 1 to 4 carbon atoms.

[0087] The modified 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, still more 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 PPVE and HFP, in terms of being able to be mixed more uniformly with the powder components of the electrochemical device and being able to obtain a composite sheet having even greater strength and flexibility.

[0088] The PTFE may have a core-shell structure. Examples of PTFE having a core-shell structure include modified PTFE particles containing a core of high molecular weight PTFE and a shell of lower molecular weight PTFE or modified PTFE. Examples of such modified PTFE include the PTFE described in JP-A-2005-527652.

[0089] The PTFE composition of the present disclosure can be mixed more uniformly with the powder components of an electrochemical device, and a composite sheet having even greater strength and flexibility can be obtained. Therefore, the endothermic peak temperature is preferably 333°C or higher, more preferably 335°C or higher, and even more preferably 337°C or higher, and is preferably 350°C or lower, and more preferably 346°C or lower. The endothermic peak temperature is the temperature corresponding to the minimum point in the heat of fusion curve obtained by performing differential scanning calorimetry (DSC) at a heating rate of 10°C / min on a PTFE composition that has not been heated to a temperature of 300°C or higher. When there are two or more minimum points in one melting peak, the temperature corresponding to the minimum value is taken as the endothermic peak temperature.

[0090] The PTFE composition of the present disclosure is preferably substantially free of moisture. This can suppress gas generation and deterioration of electrochemical device properties. Furthermore, a wide range of electrode active materials and solid electrolytes can be combined, which is advantageous in terms of production processes. Being substantially free of moisture means that the moisture content of the PTFE composition is 0.010% by mass or less. The moisture content is preferably 0.005% by mass or less, more preferably 0.003% by mass or less, even more preferably 0.002% by mass or less, and even more preferably 0.001% by mass or less. The moisture content is measured by the following method. The mass of the PTFE composition is measured before and after heating at 150°C for 2 hours, and calculated according to the following formula. A sample is taken three times, and the values ​​are calculated for each sample, and the average is calculated. Water content (mass%)=[(mass (g) of PTFE composition before heating)−(mass (g) of PTFE composition after heating)] / (mass (g) of PTFE composition before heating)×100

[0091] The PTFE composition of the present disclosure preferably does not substantially contain fluorine-containing compounds with a molecular weight of 1000 or less. "Substantially does not contain fluorine-containing compounds" means that the amount of the fluorine-containing compounds is 25 mass ppb or less relative to the PTFE composition. The amount of the fluorine-containing compounds is preferably 20 mass ppb or less, more preferably 15 mass ppb or less, even more preferably 10 mass ppb or less, even more preferably less than 10 mass ppb, even more preferably 1 mass ppb or less, even more preferably less than 1 mass ppb, and particularly preferably less than the lower limit of quantification. The lower limit is not particularly limited, and may be an amount less than the lower limit of quantification.

[0092] The amount of the fluorine-containing compound having a molecular weight of 1,000 or less is measured by the following method. 1 g of sample is weighed, 10 g (12.6 ml) of methanol is added, and ultrasonic treatment is performed for 60 minutes to obtain an extract. The obtained extract is concentrated using a nitrogen purge as appropriate, and the fluorine-containing compounds in the concentrated extract are measured by LC / MS / MS. Molecular weight information is extracted from the obtained LC / MS spectrum, and a match with the structural formula of the candidate fluorine-containing compound is confirmed. Aqueous solutions with five or more levels of content of the standard substance are prepared, and LC / MS analysis is performed on the aqueous solutions with each content. The relationship between the content and the area area relative to that content is plotted, and a calibration curve is drawn. Using the calibration curve, the area area of ​​the LC / MS chromatogram of the fluorine-containing compound in the extract is converted to the content of the fluorine-containing compound. The lower limit of quantitation in this measurement method is 10 ppb by mass.

[0093] Examples of the fluorine-containing compound having a molecular weight of 1000 or less include a fluorine-containing compound having a hydrophilic group with a molecular weight of 1000 g / mol or less. The molecular weight of the fluorine-containing compound is preferably 800 or less, more preferably 500 or less. The polymer particles obtained by polymerization in the presence of a fluorine-containing surfactant usually contain a fluorine-containing surfactant in addition to PTFE. In this specification, the fluorine-containing surfactant is used during polymerization. The fluorine-containing compound having a molecular weight of 1000 or less may be a compound that is not added during polymerization, for example, a compound that is by-produced during polymerization. Note that, when the fluorine-containing compound having a molecular weight of 1000 or less contains an anionic moiety and a cationic moiety, it means a compound containing fluorine, the molecular weight of which of the anionic moiety is 1000 or less. The fluorine-containing compound having a molecular weight of 1000 or less does not include PTFE.

[0094] Examples of the hydrophilic group include -COOM and -SO ２ M or -SO ３ M, -COOM, -SO ３ M (in each formula, M is H, a metal atom, NR １ ４, optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium, and R １ is H or an organic group.

[0095] As the fluorine-containing surfactant, a surfactant containing fluorine (anionic fluorine-containing surfactant) in which the molecular weight of the anionic part is 1000 or less can also be used. The "anionic part" means the part of the fluorine-containing surfactant excluding the cation. For example, F(CF ２ ) ｎ１ In the case of COOM, "F(CF ２ ) ｎ１ The anionic fluorine-containing surfactant is a surfactant represented by the following general formula (N ０ ): X ｎ０ -Rf ｎ０ -Y ０ (N ０ ) (wherein, X ｎ０ is H, Cl or F. ｎ０ is a linear, branched or cyclic alkylene group having 3 to 20 carbon atoms, in which some or all of the H atoms are substituted with F, and the alkylene group may contain one or more ether bonds, and some of the H atoms may be substituted with Cl. ０ is an anionic group. ０ The anionic group is -COOM, -SO ２ M or -SO ３ M, -COOM or -SO ３ M. M may be H, a metal atom, NR １ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium, and R １ is H or an organic group. The metal atom includes alkali metals (Group 1), alkaline earth metals (Group 2), etc., such as Na, K, or Li. １ As the group, H or C １－１０ and may be an organic group of the formula: １－４and may be an organic group of the formula: １－４ M may be H, a metal atom, or an alkyl group of the formula NR １ ４ may be H, an alkali metal (Group 1), an alkaline earth metal (Group 2), or NR １ ４ may be H, Na, K, Li or NH ４ The above Rf ｎ０ may be one in which 50% or more of H is substituted with fluorine.

[0096] The above fluorine-containing surfactant may be one type of fluorine-containing surfactant or a mixture containing two or more types of fluorine-containing surfactants.

[0097] Examples of the fluorine-containing surfactant include compounds represented by the following formula: F(CF ２ ) ７ COOM, F(CF ２ ) ５ COOM, H(CF ２ ) ６ COOM, H(CF ２ ) ７ COOM, C.F. ３ O (CF ２ ) ３ OCHFCF ２ COOM, C ３ F ７ OCF (CF ３ )CF ２ OCF (CF ３ ) COOM, C.F. ３ CF ２ CF ２ OCF (CF ３ ) COOM, C.F. ３ CF ２ OCF ２ CF ２ OCF ２ COOM, C ２ F ５ OCF (CF ３ )CF ２ OCF (CF ３ ) COOM, C.F. ３ OCF (CF ３)CF ２ OCF (CF ３ ) COOM, C.F. ２ ClCF ２ CF ２ OCF (CF ３ )CF ２ OCF ２ COOM, C.F. ２ ClCF ２ CF ２ OCF ２ CF (CF ３ ) OCF ２ COOM, C.F. ２ ClCF(CF ３ ) OCF (CF ３ )CF ２ OCF ２ COOM, C.F. ２ ClCF(CF ３ ) OCF ２ CF (CF ３ ) OCF ２ COOM, and (In each formula, M is H, metal atom, NR １ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium. １ is H or an organic group.) The PTFE composition of the present disclosure is preferably substantially free of any of the fluorine-containing compounds represented by the above formulas.

[0098] In each of the above formulas, M is H, a metal atom, or NR １ ４ may be H, an alkali metal (Group 1), an alkaline earth metal (Group 2), or NR １ ４ may be H, Na, K, Li or NH ４ R １ is H or C １－１０ and may be an organic group of the formula: １－４ and may be an organic group of the formula: １－４ The alkyl group may be:

[0099] If the PTFE composition of the present disclosure is substantially free of any of the fluorine-containing compounds represented by the above formula, it can further suppress gas generation and deterioration of electrochemical device properties. Substantially free of any of the fluorine-containing compounds represented by the above formula means that the amount of the fluorine-containing compound is 25 mass ppb or less relative to the PTFE composition. The amount of the fluorine-containing compound is preferably 20 mass ppb or less, more preferably 15 mass ppb or less, even more preferably 10 mass ppb or less, even more preferably less than 10 mass ppb, even more preferably 1 mass ppb or less, even more preferably less than 1 mass ppb, and particularly preferably less than the lower limit of quantitation. The lower limit is not particularly limited, and may be an amount less than the lower limit of quantitation.

[0100] The PTFE composition of the present disclosure has the following general formula: ｎ－１ F ２ｎ－１ COO － ]M ＋ (wherein n is an integer of 9 to 14, preferably an integer of 9 to 12; M ＋ It is also preferable that the composition is substantially free of a fluorine-containing compound represented by the formula (I). This makes it possible to further suppress gas generation and deterioration of the electrochemical device properties. ＋ The M constituting the formula is the same as the M described above. Substantially not containing the fluorine-containing compound represented by the formula means that the amount of the fluorine-containing compound is 25 mass ppb or less relative to the PTFE composition. The amount of the fluorine-containing compound is preferably 20 mass ppb or less, more preferably 15 mass ppb or less, even more preferably 10 mass ppb or less, even more preferably less than 10 mass ppb, even more preferably 1 mass ppb or less, even more preferably less than 1 mass ppb, and particularly preferably less than the lower limit of quantification. The lower limit is not particularly limited, and may be an amount less than the lower limit of quantification.

[0101] The PTFE composition of the present disclosure preferably has non-melt-fabricability. The term "non-melt-fabricability" means that the melt flow rate cannot be measured at a temperature higher than the melting point in accordance with ASTM D-1238 and D-2116, in other words, that the PTFE composition does not easily flow even in the melting temperature range.

[0102] The PTFE composition of the present disclosure can be more uniformly mixed with the powder components of an electrochemical device, and a composite sheet having even greater strength and flexibility can be obtained. Therefore, the standard specific gravity (SSG) of the PTFE composition of the present disclosure is preferably 2.200 or less, more preferably 2.190 or less, even more preferably 2.180 or less, even more preferably 2.175 or less, and is preferably 2.130 or more, more preferably 2.140 or more, and even more preferably 2.150 or more. The SSG is measured by the water displacement method according to ASTM D 792 using a sample molded in accordance with ASTM D 4895 89.

[0103] The PTFE composition of the present disclosure is preferably paste-extrudable, since it can be more uniformly mixed with the powder components of an electrochemical device and can produce a composite sheet with even greater strength and flexibility. Whether a PTFE composition is paste-extrudable is determined by the following method: 60 g of the PTFE composition and 12.3 g of hydrocarbon oil (trade name: Isopar G (registered trademark), manufactured by ExxonMobil Corporation) serving as an extrusion aid are mixed in a polyethylene container for 3 minutes. The mixture is filled into the cylinder of an extruder at room temperature (25±2°C), and a load of 0.47 MPa is applied to the piston inserted into the cylinder and held for 1 minute. The mixture is then extruded through an orifice at a ram speed of 20 mm / min. The ratio of the cross-sectional area of ​​the cylinder to the cross-sectional area of ​​the orifice is 100. If the beads break and cannot be continuously extruded, the composition is deemed unextrudable; if the beads can be continuously extruded without breaking, the composition is deemed extrudable.

[0104] The form of the PTFE composition of the present disclosure is not limited, but is preferably a powder, since it can be mixed with an electrode active material and a solid electrolyte without using a large amount of a dispersion medium. Note that the PTFE composition may be in a form other than a powder, for example, a dispersion liquid.

[0105] The PTFE composition of the present disclosure may have an average secondary particle diameter of 350 μm or more, preferably 400 μm or more, more preferably 450 μm or more, and preferably 1000 μm or less, more preferably 900 μm or less, even more preferably 800 μm or less, even more preferably 700 μm or less, and particularly preferably 600 μm or less. The average secondary particle diameter is measured in accordance with JIS K 6891.

[0106] The PTFE composition of the present disclosure preferably has an apparent density of 0.40 g / ml or more, more preferably 0.43 g / ml or more, from the viewpoint of excellent handleability, and the upper limit is not particularly limited, but may be 0.70 g / ml. The apparent density is measured in accordance with JIS K 6892.

[0107] The PTFE composition of the present disclosure can be produced, for example, by mixing PTFE obtained by emulsion polymerization with PTFE obtained by suspension polymerization. The mixing method is not limited, and all of the PTFE may be mixed in the form of powder, or the PTFE may be mixed in the form of an aqueous dispersion and the powder.

[0108] The PTFE composition of the present disclosure can be suitably produced by a production method including, for example, the step (A) of mixing the aqueous dispersion of PTFE obtained by emulsion polymerization with the powder of PTFE obtained by suspension polymerization, the step (B) of coagulating the aqueous dispersion after mixing to obtain wet powder, and the step (C) of drying the wet powder.

[0109] The aqueous dispersion in step (A) can be produced by emulsion polymerization.

[0110] Above-mentioned emulsion polymerization can be carried out by known method.For example, in the presence of anionic fluorine-containing surfactant and polymerization initiator, the emulsion polymerization of the monomer (TFE and optionally modified monomer) necessary for forming above-mentioned PTFE is carried out in aqueous medium, thereby obtaining the aqueous dispersion liquid containing above-mentioned PTFE particles (primary particles).In above-mentioned emulsion polymerization, if necessary, chain transfer agent, buffer, pH adjuster, stabilizing aid, dispersion stabilizer, radical scavenger etc. can be used.

[0111] The aqueous dispersion may contain at least one of the above-mentioned fluorine-containing compounds.

[0112] The emulsion polymerization can be carried out, for example, in an aqueous medium in the presence of an anionic fluorine-containing surfactant and a polymerization initiator. The emulsion polymerization can be carried out by charging an aqueous medium, the anionic fluorine-containing surfactant, monomers, and other additives as necessary into a polymerization reactor, stirring the contents of the reactor, maintaining the reactor at a predetermined polymerization temperature, and then adding a predetermined amount of polymerization initiator to initiate the polymerization reaction. After the start of the polymerization reaction, additional monomers, polymerization initiators, chain transfer agents, the surfactants, etc. may be added depending on the purpose.

[0113] The polymerization initiator is not particularly limited as long as it can generate radicals within the polymerization temperature range, and known oil-soluble and / or water-soluble polymerization initiators can be used.Furthermore, it can also be combined with a reducing agent or the like to initiate polymerization as redox.The concentration of the polymerization initiator is appropriately determined according to the type of monomer, the molecular weight of the target PTFE, and the reaction rate.

[0114] As the polymerization initiator, an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator can be used.

[0115] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, for example, dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and disec-butyl peroxydicarbonate, peroxyesters such as t-butyl peroxyisobutyrate and t-butyl peroxypivalate, dialkyl peroxides such as di-t-butyl peroxide, and the like. Also usable are di(ω-hydro-dodecafluoroheptanoyl) peroxide, di(ω-hydro-tetradecafluoroheptanoyl) peroxide, di(ω-hydro-hexadecafluorononanoyl) peroxide, di(perfluorobutyryl) peroxide, di(perfluorovaleryl) peroxide, di(perfluorohexanoyl) peroxide, di(perfluoroheptanoyl) peroxide, di(perfluorooctanoyl) peroxide, di(perfluorononanoyl) peroxide, di(ω-chloro Representative examples include di[perfluoro(or fluorochloro)acyl]peroxides such as di(ω-hexafluorobutyryl)peroxide, di(ω-chlorodecafluorohexanoyl)peroxide, di(ω-chlorotetradecafluorooctanoyl)peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydrododecafluoroheptanoyl-perfluorobutyryl-peroxide, di(dichloropentafluorobutanoyl)peroxide, di(trichlorooctafluorohexanoyl)peroxide, di(tetrachloroundecafluorooctanoyl)peroxide, di(pentachlorotetradecafluorodecanoyl)peroxide, and di(undecachlorodotriacontafluorodocosanoyl)peroxide.

[0116] The water-soluble radical polymerization initiator may be a known water-soluble peroxide, such as ammonium salts, potassium salts, or sodium salts of persulfuric acid, perborate, perchloric acid, perphosphoric acid, or percarbonate, t-butyl permaleate, t-butyl hydroperoxide, or disuccinic acid peroxide. Among these, ammonium persulfate and disuccinic acid peroxide are preferred. A reducing agent such as sulfites or sulfites may also be contained, and the amount used may be 0.1 to 20 times the amount of the peroxide.

[0117] The amount of the water-soluble radical polymerization initiator to be added is not particularly limited, but may be added all at once, stepwise, or continuously at the beginning of the polymerization in an amount (for example, several ppm relative to the water concentration) that does not significantly reduce the polymerization rate. The upper limit is a range in which the reaction temperature can be increased while removing heat from the equipment using the heat of polymerization reaction, and a more preferred upper limit is a range in which the heat of polymerization reaction can be removed from the equipment. In terms of easily obtaining the above-mentioned properties, the amount of polymerization initiator to be added is preferably an amount equivalent to 0.1 ppm or more of the aqueous medium, more preferably an amount equivalent to 1.0 ppm or more, and also preferably an amount equivalent to 100 ppm or less, more preferably an amount equivalent to 10 ppm or less.

[0118] For example, when polymerization is carried out at a low temperature of 30°C or less, it is preferable to use a redox initiator that combines an oxidizing agent and a reducing agent as the polymerization initiator. Examples of oxidizing agents include persulfates, organic peroxides, potassium permanganate, manganese triacetate, cerium ammonium nitrate, and bromates. Examples of reducing agents include sulfites, bisulfites, bromates, diimines, and oxalic acid. Examples of persulfates include ammonium persulfate and potassium persulfate. Examples of sulfites include sodium sulfite and ammonium sulfite. In order to increase the decomposition rate of the initiator, it is also preferable to add a copper salt or an iron salt to the redox initiator combination. Examples of copper salts include copper(II) sulfate, and examples of iron salts include iron(II) sulfate.

[0119] The redox initiator preferably has an oxidizing agent that is permanganic acid or a salt thereof, a persulfate, manganese triacetate, a cerium (IV) salt, or a bromic acid or a salt thereof, and a reducing agent that is a dicarboxylic acid or a salt thereof, or a diimine. More preferably, the oxidizing agent is permanganic acid or a salt thereof, a persulfate, or a bromic acid or a salt thereof, and the reducing agent is a dicarboxylic acid or a salt thereof.

[0120] Examples of the redox initiator include combinations such as 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. When using a redox initiator, either an oxidizing agent or a reducing agent may be charged into a polymerization vessel in advance, and then the other may be added continuously or intermittently to initiate polymerization. For example, when potassium permanganate / oxalic acid is used, it is preferable to charge oxalic acid into a polymerization vessel and then continuously add potassium permanganate thereto. Note that, when referring to redox initiators in this specification, "potassium permanganate / oxalic acid" refers to a combination of potassium permanganate and oxalic acid. The same applies to other compounds.

[0121] The redox initiator is preferably a combination of an oxidizing agent that is a salt and a reducing agent that is a salt. For example, the oxidizing agent that is a salt is more preferably at least one selected from the group consisting of persulfates, permanganates, cerium (IV) salts, and bromates, more preferably permanganates, and particularly preferably potassium permanganate. The reducing agent that is a salt is more preferably at least one selected from the group consisting of oxalates, malonates, succinates, glutarates, and bromates, more preferably oxalates, and particularly preferably ammonium oxalate.

[0122] 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 cerium ammonium nitrate / ammonium oxalate, more preferably at least one selected from the group consisting of potassium permanganate / oxalic acid, potassium permanganate / ammonium oxalate, potassium bromate / ammonium sulfite, and cerium ammonium nitrate / ammonium oxalate, and even more preferably potassium permanganate / oxalic acid.

[0123] When a redox initiator is used, the oxidizing agent and the reducing agent may be added all at once at the beginning of the polymerization, or the reducing agent may be added all at once at the beginning of the polymerization and the oxidizing agent may be added continuously, or the oxidizing agent may be added all at once at the beginning of the polymerization and the reducing agent may be added continuously, or both the oxidizing agent and the reducing agent may be added continuously.

[0124] When one of the above redox polymerization initiators is added at the beginning of polymerization and the other is added continuously, it is preferable to gradually reduce the rate of addition in order to obtain PTFE with a low SSG, and it is also preferable to stop the addition midway through the polymerization, and the timing for stopping the addition is preferably before 20 to 40% by mass of the total TFE consumed in the polymerization reaction is consumed.

[0125] When a redox initiator is used as a polymerization initiator, the amount of oxidizing agent added to the aqueous medium is preferably 0.1 ppm or more, more preferably 0.3 ppm or more, even more preferably 0.5 ppm or more, even more preferably 1 ppm or more, particularly preferably 5 ppm or more, particularly preferably 10 ppm or more, and preferably 10,000 ppm or less, more preferably 1,000 ppm or less, even more preferably 100 ppm or less, and even more preferably 50 ppm or less. The amount of 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, particularly preferably 10 ppm or more, and preferably 10,000 ppm or less, more preferably 1,000 ppm or less, even more preferably 100 ppm or less, and even more preferably 50 ppm or less. 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. The polymerization temperature is preferably 10° C. or higher, more preferably 20° C. or higher, and even more preferably 30° C. or higher.

[0126] As the polymerization initiator, a water-soluble radical polymerization initiator and a redox initiator are preferred, since the above-mentioned properties can be easily obtained.

[0127] The aqueous medium is a reaction medium for polymerization and refers to a liquid containing water. The aqueous medium is not particularly limited as long as it contains water, and may contain water and, for example, a fluorine-free organic solvent such as an alcohol, an ether, or a ketone, and / or a fluorine-containing organic solvent having a boiling point of 40° C. or lower.

[0128] In the emulsion polymerization, a nucleating agent, a chain transfer agent, a buffer, a pH adjuster, a stabilizing aid, a dispersion stabilizer, a radical scavenger, a decomposing agent for the polymerization initiator, a dicarboxylic acid, etc. may be used, if necessary.

[0129] The emulsion polymerization is preferably carried out with the addition of a nucleating agent for the purpose of adjusting the particle size. The nucleating agent is preferably added before the start of the polymerization reaction. As the nucleating agent, a known agent can be used, and 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.

[0130] The fluoropolyether may be, for example, a perfluoropolyether (PFPE) acid or a salt thereof. The perfluoropolyether (PFPE) acid or a salt thereof may 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. Two or more types of fluorocarbon groups may be present in the molecule. A representative structure has a repeating unit represented by the following formula: (-CFCF ３ -CF ２ -O-) ｎ (-CF ２ -CF ２ -CF ２ -O-) ｎ (-CF ２ -CF ２ -O-) ｎ -(-CF ２ -O-) ｍ (-CF ２ -CFCF ３ -O-) ｎ -(-CF ２ -O-) ｍ

[0131] These structures are described by Kasai in J. Appl. Polymer Sci. 57, 797 (1995). As disclosed therein, the PFPE acid or its salt may have a carboxylic acid group or a salt thereof at one or both ends. The PFPE acid or its salt may also have a sulfonic acid or phosphonic acid group or a salt thereof at one or both ends. The PFPE acid or its salt may also have a different group at each end. For monofunctional PFPEs, the other end of the molecule is usually perfluorinated but may contain a hydrogen or chlorine atom. The PFPE acid or its salt has at least two ether oxygens, preferably at least four ether oxygens, and even more preferably at least six ether oxygens. Preferably, at least one of the fluorocarbon groups separating the ether oxygens, more preferably at least two of such fluorocarbon groups, has two or three carbon atoms. Even more preferably, at least 50% of the fluorocarbon groups separating the ether oxygens have 2 or 3 carbon atoms. Also preferably, the PFPE acid or salt thereof 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 of the PFPE acids or salts thereof having acid groups at one or both termini may be used in the manufacturing method of the present disclosure. The PFPE acid or salt thereof preferably has a number average molecular weight of less than 6,000 g / mol.

[0132] In view of being able to further increase the molecular weight of PTFE and improve the strength of composite sheet, it is preferable to add radical scavenger or decomposer of polymerization initiator to carry out the emulsion polymerization.After the start of polymerization reaction, preferably, the decomposer of radical scavenger or polymerization initiator is added before 10% by mass or more, preferably 20% by mass or more of the total TFE consumed in polymerization reaction is polymerized, and it is also preferable to add before 50% by mass or less, preferably 40% by mass or less is polymerized.When carrying out depressurization and repressurization as described later, it is preferable to add after that.

[0133] The radical scavenger is a compound that does not have the ability to reinitiation after addition or chain transfer to the free radicals in the polymerization system. Specifically, a compound that easily undergoes chain transfer reaction with a primary radical or a propagating radical to generate a stable radical that does not subsequently react with the monomer, or a compound that easily undergoes an addition reaction with a primary radical or a propagating radical to generate a stable radical, is used. The activity of what is generally called a chain transfer agent is characterized by the chain transfer constant and the reinitiation efficiency, and among chain transfer agents, those with a reinitiation efficiency of almost 0% are called radical scavengers. The radical scavenger can also be described as, for example, a compound whose chain transfer constant with TFE at the polymerization temperature is greater than the polymerization rate constant and whose reinitiation efficiency is essentially 0%. "Reinitiation efficiency is essentially 0%" means that the generated radical turns the radical scavenger into a stable radical. Preferably, the compound has a chain transfer constant (Cs) (= chain transfer rate constant (kc) / polymerization rate constant (kp)) with TFE at polymerization temperature of more than 0.1, and the chain transfer constant (Cs) of the compound is more preferably 0.5 or more, even more preferably 1.0 or more, even more preferably 5.0 or more, and particularly preferably 10 or more.

[0134] Examples of the radical scavenger include aromatic hydroxy compounds, aromatic amines, N,N-diethylhydroxylamine, quinone compounds, terpenes, thiocyanates, and cupric chloride (CuCl ２) is preferred. Examples of aromatic hydroxy compounds include unsubstituted phenol, polyhydric phenol, salicylic acid, m- or p-salicylic acid, gallic acid, naphthol, etc. Examples of the unsubstituted phenol include o-, m-, or p-nitrophenol, o-, m-, or p-aminophenol, p-nitrosophenol, etc. Examples of polyhydric phenols include catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, naphthresorcinol, etc. Examples of aromatic amines include o-, m-, or p-phenylenediamine, benzidine, etc. Examples of the quinone compounds include o-, m-, or p-benzoquinone, 1,4-naphthoquinone, alizarin, etc. Examples of thiocyanates include ammonium thiocyanate (NH ４ Examples of the radical scavenger include potassium thiocyanate (KSCN), sodium thiocyanate (NaSCN), etc. Among these, aromatic hydroxy compounds are preferred, unsubstituted phenols or polyhydric phenols are more preferred, and hydroquinone is even more preferred.

[0135] The amount of the radical scavenger added is preferably an amount corresponding to 3 to 500% (molar basis) of the polymerization initiator concentration, from the viewpoint of appropriately reducing the standard specific gravity. A more preferred lower limit is 10% (molar basis), and even more preferred is 15% (molar basis). A more preferred upper limit is 400% (molar basis), and even more preferred is 300% (molar basis).

[0136] The polymerization initiator decomposer may be any compound capable of decomposing the polymerization initiator used. For example, at least one selected from the group consisting of sulfites, bisulfites, bromates, diimines, diimine salts, oxalic acid, oxalates, copper salts, and iron salts is preferred. Examples of sulfites include sodium sulfite and ammonium sulfite. Examples of copper salts include copper(II) sulfate, and examples of iron salts include iron(II) sulfate. The amount of decomposer added is preferably an amount equivalent to 3 to 500% (molar basis) of the initiator concentration, from the viewpoint of appropriately reducing the standard specific gravity. A more preferred lower limit is 10% (molar basis), and even more preferred is 15% (molar basis). A more preferred upper limit is 400% (molar basis), and even more preferred is 300% (molar basis).

[0137] The emulsion polymerization may be carried out in the presence of 5 to 500 ppm of dicarboxylic acid relative to the aqueous medium, preferably 10 to 200 ppm, in order to reduce the amount of coagulation produced during polymerization. If the amount of dicarboxylic acid relative to the aqueous medium is too small, sufficient effects may not be obtained, while if the amount is too large, chain transfer reactions may occur, resulting in a low molecular weight polymer. The amount of dicarboxylic acid is more preferably 150 ppm or less. The dicarboxylic acid may be added before the start of the polymerization reaction or during the polymerization.

[0138] As the dicarboxylic acid, for example, one represented by the general formula: HOOCRCOOH (wherein R represents an alkylene group having 1 to 5 carbon atoms) is preferred, and succinic acid, malonic acid, glutaric acid, adipic acid, and pimelic acid are more preferred, with succinic acid being even more preferred.

[0139] In the emulsion polymerization, the polymerization temperature and polymerization pressure are appropriately determined depending on the type of monomer used, the molecular weight of the target PTFE, and the reaction rate.Usually, the polymerization temperature is 5 to 150°C, preferably 10°C or higher, more preferably 30°C or higher, and even more preferably 50°C or higher.Moreover, it is more preferably 120°C or lower, and even more preferably 100°C or lower.The polymerization pressure is 0.05 to 10 MPaG.More preferably, the polymerization pressure is 0.3 MPaG or higher, and even more preferably 0.5 MPaG or higher.More preferably, it is 5.0 MPaG or lower, and even more preferably 3.0 MPaG or lower.

[0140] When VDF is used as the modified monomer, in the emulsion polymerization, the VDF concentration in the gas in the reactor at the start of polymerization (when the initiator is added) is preferably 0.001 mol% or more, more preferably 0.01 mol% or more, since the above-mentioned physical properties can be easily obtained. The concentration may also be 15 mol% or less, preferably 6.0 mol% or less, more preferably 5.0 mol% or less, even more preferably 3.0 mol% or less, and particularly preferably 1.0 mol% or less. The VDF concentration may then be maintained until the end of the polymerization reaction, or pressure relief may be performed during the reaction. VDF is preferably charged all at once before the start of polymerization, but a portion may be added continuously or intermittently after the start of polymerization.

[0141] When VDF is used as the modified monomer, it is preferable not to release the pressure in the emulsion polymerization after VDF is charged into the polymerization vessel until the polymerization is completed, which allows VDF to remain in the system until the end of the polymerization, and further increases the strength of the resulting composite sheet using PTFE.

[0142] When HFP is used as a modified monomer, in the emulsion polymerization, the HFP concentration in the gas in the reactor at the start of polymerization (when the initiator is added) is preferably 0.01 to 3.0 mol%, since the above-mentioned physical properties can be easily obtained. Furthermore, the HFP concentration in the gas in the reactor at the time when 40 mass% of the total TFE consumed in the polymerization reaction is polymerized is preferably greater than 0 mol% and 0.2 mol% or less. The above HFP concentration is preferably maintained until the end of the polymerization reaction. HFP may be charged all at once before the start of polymerization, or a portion may be charged 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, the extrusion pressure is reduced, despite the high strength of the resulting PTFE mixture sheet.

[0143] When HFP is used as a modified monomer, in the emulsion polymerization, in order to further improve the strength of the resulting composite sheet using PTFE, it is preferable to depressurize before 5 to 40 mass% of the total TFE consumed in the polymerization reaction is polymerized, and then repressurize using only TFE.The depressurization is preferably carried out so that the pressure in the reactor is 0.2 MPaG or less, more preferably 0.1 MPaG or less, and even more preferably 0.05 MPaG or less.It is also preferable to carry out so that the pressure is 0.0 MPaG or more.In addition, the depressurization and repressurization may be carried out multiple times.Depressurization may be carried out using a vacuum pump until reduced pressure is reached.

[0144] When CTFE is used as modified monomer, in the above-mentioned emulsion polymerization, the CTFE concentration in the gas in reactor at the start of polymerization (when adding initiator) is preferably 0.001 mol% or more, more preferably 0.01 mol% or more, because it can easily obtain each of the above-mentioned properties.Above-mentioned concentration is also preferably 3.0 mol% or less, more preferably 1.0 mol% or less.Above-mentioned CTFE concentration can be maintained until the end of polymerization reaction, or can be depressurized during the process.It is preferable to charge CTFE all at once before the start of polymerization, but can also be added partly continuously or intermittently after the start of polymerization.

[0145] When CTFE is used as the modified monomer, it is preferable that the pressure is not released in the emulsion polymerization after the CTFE is charged into the polymerization vessel until the polymerization is completed. This allows the CTFE to remain in the system until the end of the polymerization, and the strength of the resulting composite sheet using PTFE can be further increased.

[0146] The powder in step (A) can be produced by suspension polymerization.

[0147] Suspension polymerization can be carried out, for example, by charging a reactor with a monomer such as TFE, an aqueous medium, and other additives as necessary, stirring the contents of the reactor, maintaining the reactor at a predetermined polymerization temperature, and then adding a predetermined amount of polymerization initiator to initiate the polymerization reaction. After the start of the polymerization reaction, additional monomers such as TFE, polymerization initiators, chain transfer agents, etc. may be added depending on the purpose.

[0148] Suspension polymerization can be carried out in the presence of a polymerization initiator. The polymerization initiator is not particularly limited as long as it can generate radicals within the polymerization temperature range, and known oil-soluble and / or water-soluble polymerization initiators can be used. Furthermore, polymerization can also be initiated as a redox reaction in combination with a reducing agent, etc. The concentration of the polymerization initiator is appropriately determined depending on the type of monomer, the molecular weight of the target polytetrafluoroethylene, and the reaction rate.

[0149] As the polymerization initiator, a water-soluble radical polymerization initiator can be used.

[0150] Examples of water-soluble radical polymerization initiators include ionic radical initiators such as persulfates, such as ammonium persulfate, potassium persulfate, and alkali metal persulfates, and permanganates. Furthermore, these radical polymerization initiators may be used as an oxidizing component in combination with, for example, hydrazine, diimine, iron(II) sulfate, copper(II) sulfate, oxalates, sulfites, or the like as a reducing component to form redox initiators. Compounds capable of forming hydrates, such as iron(II) sulfate and copper(II) sulfate, may be anhydrous or hydrated.

[0151] Examples of the redox initiator include ammonium persulfate / copper(II) sulfate, ammonium persulfate / iron(II) sulfate, ammonium persulfate / sodium sulfite / iron(II) sulfate, ammonium persulfate / azodicarbonamide / copper(II) sulfate, ammonium persulfate / sodium azodicarboxylate / copper(II) sulfate, ammonium carbamate / copper(II) sulfate, ammonium persulfate / ammonium carbamate / copper(II) sulfate, and potassium permanganate / ammonium oxalate.

[0152] In the case of such a combination of redox initiators, it is preferred to charge one of them in advance into a polymerization vessel, and then add the other intermittently or continuously while carrying out polymerization.

[0153] The amount of radical polymerization initiator used is adjusted so as to allow good control of the reaction rate. For example, in the case of ammonium persulfate, the amount is preferably 1 to 100 ppm, more preferably 1 to 50 ppm, and most preferably 1 to 10 ppm relative to the aqueous medium.

[0154] Suspension polymerization is carried out by polymerizing TFE in an aqueous medium under stirring. The aqueous medium means a liquid containing water. The aqueous medium is not particularly limited as long as it contains water.

[0155] The suspension polymerization can be carried out in the presence or absence of a surfactant. The amount of the surfactant is preferably 2000 ppm by mass or less, more preferably 1000 ppm by mass or less, even more preferably 500 ppm by mass or less, even more preferably 200 ppm by mass or less, even more preferably 100 ppm by mass or less, and even more preferably 50 ppm by mass or less, based on the aqueous medium. The amount of the surfactant may be 0 ppm by mass, 0.5 ppm by mass or more, 1 ppm by mass or more, 5 ppm by mass or more, or 10 ppm by mass or more.

[0156] The surfactant used in suspension polymerization is preferably a fluorine-containing surfactant. Examples of the fluorine-containing surfactant include anionic fluorine-containing surfactants. The anionic fluorine-containing surfactant may be, for example, a surfactant containing fluorine atoms and having a total carbon number of 20 or less excluding the anionic group.

[0157] As the fluorine-containing surfactant, a surfactant containing fluorine, the molecular weight of the anionic part of which is 1000 or less, preferably 800 or less, can also be used. The "anionic part" means the part of the fluorine-containing surfactant excluding the cation. For example, F(CF) represented by the formula (I) described below can be used. ２ ) ｎ１ In the case of COOM, "F(CF ２ ) ｎ１ This is the "COO" part.

[0158] The fluorine-containing surfactant also includes a fluorine-containing surfactant having a Log POW of 3.5 or less. The Log POW of the fluorine-containing surfactant is preferably 3.4 or less. The Log POW is a partition coefficient between 1-octanol and water, and is expressed as Log P [where P represents the ratio of the fluorine-containing surfactant concentration in octanol to the fluorine-containing surfactant concentration in water when a 1:1 octanol / water mixture containing the fluorine-containing surfactant undergoes phase separation].

[0159] The LogPOW was measured using a column: TOSOH ODS-120T column (φ4.6 mm×250 mm, manufactured by Tosoh Corporation) and an eluent: acetonitrile / 0.6% by mass HClO ４ HPLC is performed on standard substances (heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid) with known octanol / water partition coefficients under conditions of water=1 / 1 (vol / vol %), flow rate: 1.0 ml / min, sample amount: 300 μL, column temperature: 40°C, and detection light: UV 210 nm. A calibration curve is prepared between each elution time and the known octanol / water partition coefficient, and the elution time is calculated from the HPLC elution time of the sample solution based on this calibration curve.

[0160] Specific examples of the fluorine-containing surfactants include those described in U.S. Patent Application Publication Nos. 2007 / 0015864, 2007 / 0015865, 2007 / 0015866, 2007 / 0276103, 2007 / 0117914, 2007 / 142541, 2008 / 0015319, and U.S. Pat. No. 3,250,808. , U.S. Patent No. 3,271,341, JP 2003-119204 A, WO 2005 / 042593, WO 2008 / 060461, WO 2007 / 046377, JP 2007-119526 A, WO 2007 / 046482, WO 2007 / 046345, U.S. Patent Application Publication No. 2014 / 0228531, WO 2013 / 189824, and those described in WO 2013 / 189826, and the like.

[0161] The anionic fluorine-containing surfactant may be a compound represented by the following general formula (N ０ ): X ｎ０ -Rf ｎ０ -Y ０ (N ０ ) (wherein, X ｎ０ is H, Cl or F. ｎ０ is a linear, branched or cyclic alkylene group having 3 to 20 carbon atoms, in which some or all of the H atoms are substituted with F, and the alkylene group may contain one or more ether bonds, and some of the H atoms may be substituted with Cl. ０ is an anionic group. ０ The anionic group is -COOM, -SO ２ M or -SO ３ M, -COOM or -SO ３ M. M may be H, a metal atom, NR ７ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium, and R ７is H or an organic group. The metal atom includes alkali metals (Group 1), alkaline earth metals (Group 2), etc., such as Na, K, or Li. ７ As the group, H or C １－１０ and may be an organic group of the formula: １－４ and may be an organic group of the formula: １－４ M may be H, a metal atom, or an alkyl group of the formula NR ７ ４ may be H, an alkali metal (Group 1), an alkaline earth metal (Group 2), or NR ７ ４ may be H, Na, K, Li or NH ４ The above Rf ｎ０ may be one in which 50% or more of H is substituted with fluorine.

[0162] The general formula (N ０ The compound represented by the following general formula (N １ ): X ｎ０ -(CF ２ ) ｍ１ -Y ０ (N １ ) (wherein, X ｎ０ is H, Cl, and F, m1 is an integer from 3 to 15, and Y ０ is as defined above), a compound represented by the following general formula (N ２ ): Rf ｎ１ -O-(CF(CF ３ )CF ２ O) ｍ２ CFX ｎ１ -Y ０ (N ２ ) (wherein, Rf ｎ１ is a perfluoroalkyl group having 1 to 5 carbon atoms, m2 is an integer of 0 to 3, and X ｎ１ is F or CF ３ and Y ０ is as defined above), a compound represented by the following general formula (N ３ ): Rf ｎ２ (CH ２ ) ｍ３ -(Rf ｎ３ ) ｑ -Y ０(N ３ ) (wherein, Rf ｎ２ is a partially or fully fluorinated alkyl group having 1 to 13 carbon atoms, which may contain an ether bond and / or a chlorine atom, m3 is an integer of 1 to 3, and Rf ｎ３ is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, q is 0 or 1, and Y ０ is as defined above), a compound represented by the following general formula (N ４ ): Rf ｎ４ -O-(CY ｎ１ Y ｎ２ ) ｐ CF ２ -Y ０ (N ４ ) (wherein, Rf ｎ４ is a linear or branched partially or fully fluorinated alkyl group having 1 to 12 carbon atoms, which may contain an ether bond; Y ｎ１ and Y ｎ２ are the same or different and are H or F, p is 0 or 1, and Y ０ is as defined above.) and a compound represented by the general formula (N ５ ): (In the formula, X ｎ２ , X ｎ３ and X ｎ４ Rf may be the same or different and are H, F, or a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms, which may contain an ether linkage. ｎ５ is a linear or branched partially or fully fluorinated alkylene group having 1 to 3 carbon atoms, which may contain an ether bond; L is a linking group; Y ０ is as defined above, where X ｎ２ , X ｎ３ , X ｎ４ and Rf ｎ５ wherein the total number of carbon atoms is 18 or less.

[0163] The general formula (N ０) More specifically, the compounds represented by the formula (I) below include perfluorocarboxylic acids (I), ω-H perfluorocarboxylic acids (II), perfluoroether carboxylic acids (III), perfluoroalkyl alkylene carboxylic acids (IV), perfluoroalkoxy fluorocarboxylic acids (V), perfluoroalkyl sulfonic acids (VI), ω-H perfluorosulfonic acids (VII), perfluoroalkyl alkylene sulfonic acids (VIII), alkyl alkylene carboxylic acids (IX), fluorocarboxylic acids (X), alkoxy fluorosulfonic acids (XI), alkoxy fluorosulfonic acids (XI), and the like.

[0164] The perfluorocarboxylic acid (I) is represented by the following general formula (I): F(CF ２ ) ｎ１ COOM (I) (wherein n1 is an integer of 3 to 14, and M is H, a metal atom, NR ７ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium, and R ７ is H or an organic group.

[0165] The ω-H perfluorocarboxylic acid (II) is represented by the following general formula (II): H(CF ２ ) ｎ２ COOM (II) (wherein n2 is an integer of 4 to 15, and M is as defined above).

[0166] The perfluoroethercarboxylic acid (III) is represented by the following general formula (III): １ -O-(CF(CF ３ )CF ２ O) ｎ３ CF (CF３ ) COOM (III) (wherein, Rf １ is a perfluoroalkyl group having 1 to 5 carbon atoms, n3 is an integer of 0 to 3, and M is as defined above.

[0167] The perfluoroalkyl alkylene carboxylic acid (IV) is represented by the following general formula (IV): ２ (CH ２ ) ｎ４ Rf ３ COOM (IV) (wherein, Rf ２ is a perfluoroalkyl group having 1 to 5 carbon atoms, and Rf ３ is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, n4 is an integer of 1 to 3, and M is as defined above.

[0168] The alkoxyfluorocarboxylic acid (V) is represented by the following general formula (V): ４ -O-CY １ Y ２ CF ２ -COOM (V) (wherein, Rf ４ is a linear or branched, partially or fully fluorinated alkyl group having 1 to 12 carbon atoms, which may contain an ether bond and / or a chlorine atom; Y １ and Y ２ are the same or different and are H or F, and M is as defined above.

[0169] The perfluoroalkylsulfonic acid (VI) is represented by the following general formula (VI): F(CF ２ ) ｎ５ SO ３ M (VI) (wherein n5 is an integer of 3 to 14, and M is as defined above).

[0170] The ω-H perfluorosulfonic acid (VII) is represented by the following general formula (VII): H(CF ２ ) ｎ６ SO ３M (VII) (wherein n6 is an integer of 4 to 14, and M is as defined above).

[0171] The perfluoroalkyl alkylene sulfonic acid (VIII) is represented by the following general formula (VIII): ５ (CH ２ ) ｎ７ SO ３ M (VIII) (wherein, Rf ５ is a perfluoroalkyl group having 1 to 13 carbon atoms, n7 is an integer of 1 to 3, and M is as defined above.

[0172] The alkyl alkylene carboxylic acid (IX) is represented by the following general formula (IX): ６ (CH ２ ) ｎ８ COOM (IX) (wherein, Rf ６ is a linear or branched partially or fully fluorinated alkyl group having 1 to 13 carbon atoms which may contain an ether bond, n8 is an integer from 1 to 3, and M is as defined above.

[0173] The fluorocarboxylic acid (X) is represented by the following general formula (X): ７ -O-Rf ８ -O-CF ２ -COOM (X) (wherein, Rf ７ is a linear or branched, partially or fully fluorinated alkyl group having 1 to 6 carbon atoms, which may contain an ether bond and / or a chlorine atom, and Rf ８ is a linear or branched, partially or fully fluorinated alkyl group having 1 to 6 carbon atoms, and M is as defined above.

[0174] The alkoxyfluorosulfonic acid (XI) is represented by the following general formula (XI): ９ -O-CY １ Y ２ CF ２ -SO ３ M (XI) (wherein, Rf ９is a linear or branched alkyl group having 1 to 12 carbon atoms, which may contain an ether bond, and which may contain chlorine, and which is partially or completely fluorinated; Y １ and Y ２ are the same or different and are H or F, and M is as defined above.

[0175] The compound (XII) is represented by the following general formula (XII): (In the formula, X １ , X ２ and X ３ Rf may be the same or different and are H, F and linear or branched partially or fully fluorinated alkyl groups having 1 to 6 carbon atoms, which may contain ether bonds; １０ is a perfluoroalkylene group having 1 to 3 carbon atoms, L is a linking group, and Y ０ is an anionic group. ０ is -COOM, -SO ２ M or -SO ３ M, and -SO ３ M or COOM (wherein M is as defined above). Examples of L include a single bond and a partially or fully fluorinated alkylene group having 1 to 10 carbon atoms which may contain an ether bond.

[0176] The compound (XIII) has the following general formula (XIII): １１ -O-(CF ２ CF (CF ３ ) O) ｎ９ (CF ２ O) ｎ１０ CF ２ COOM (XIII) (wherein, Rf １１ is a fluoroalkyl group containing chlorine and having 1 to 5 carbon atoms, n9 is an integer of 0 to 3, n10 is an integer of 0 to 3, and M is as defined above. ２ ClO(CF ２ CF (CF ３ ) O) ｎ９ (CF ２ O) ｎ１０ CF２ COONH ４ (a mixture having an average molecular weight of 750, wherein n9 and n10 are as defined above).

[0177] As such, examples of the anionic fluorine-containing surfactant include carboxylic acid surfactants and sulfonic acid surfactants.

[0178] The fluorine-containing surfactant may be one type of fluorine-containing surfactant or a mixture containing two or more types of fluorine-containing surfactants.

[0179] Examples of the fluorine-containing surfactant include compounds represented by the following formula: F(CF ２ ) ７ COOM, F(CF ２ ) ５ COOM, H(CF ２ ) ６ COOM, H(CF ２ ) ７ COOM, C.F. ３ O (CF ２ ) ３ OCHFCF ２ COOM, C ３ F ７ OCF (CF ３ )CF ２ OCF (CF ３ ) COOM, C.F. ３ CF ２ CF ２ OCF (CF ３ ) COOM, C.F. ３ CF ２ OCF ２ CF ２ OCF ２ COOM, C ２ F ５ OCF (CF ３ )CF ２ OCF (CF ３ ) COOM, C.F. ３ OCF (CF ３ )CF ２ OCF (CF ３ ) COOM, C.F. ２ ClCF ２ CF２ OCF (CF ３ )CF ２ OCF ２ COOM, C.F. ２ ClCF ２ CF ２ OCF ２ CF (CF ３ ) OCF ２ COOM, C.F. ２ ClCF(CF ３ ) OCF (CF ３ )CF ２ OCF ２ COOM, C.F. ２ ClCF(CF ３ ) OCF ２ CF (CF ３ ) OCF ２ COOM, (In each formula, M is H, metal atom, NR ７ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium. ７ is H or an organic group.

[0180] The suspension polymerization particles obtained by the suspension polymerization carried out under the presence of fluorine-containing surfactant generally contain fluorine-containing surfactant in addition to polytetrafluoroethylene.In addition, the suspension polymerization particles obtained by polymerizing the monomer such as TFE, modified monomer, etc. may contain the fluorine-containing compound produced by the polymerization of monomer in addition to polytetrafluoroethylene.In the present disclosure, fluorine-containing compound is the compound that is not added during suspension polymerization, and for example, includes the compound that has the structure similar to that of fluorine-containing surfactant but has different carbon number.

[0181] According to the above-mentioned production method, polytetrafluoroethylene particles having a reduced content of fluorine-containing compounds generated by polymerization of monomers can be produced. Furthermore, according to the production method of the present disclosure, even when suspension polymerization is performed in the presence of a fluorine-containing surfactant, polytetrafluoroethylene particles having a reduced content of fluorine-containing surfactant can be produced.

[0182] A typical compound as the fluorine-containing compound in the suspension polymerized particles is a fluorine-containing compound having a hydrophilic group and a molecular weight of 1000 or less, preferably 800 g / mol or less. According to the above production method, polytetrafluoroethylene particles can be produced in which the content of the fluorine-containing compound having a hydrophilic group and a molecular weight of 1000 or less, preferably 800 g / mol or less, in the suspension polymerized particles obtained by polymerization of a monomer such as TFE is reduced.

[0183] The hydrophilic group contained in the fluorine-containing compound is preferably an anionic group such as an acid group, for example, —NH ２ , -PO ３ M, -OPO ３ M, -SO ３ M, -OSO ３ Examples of the hydrophilic group include -M and -COOM (in each formula, M represents a cation). ３ M or -COOM is preferred, and -COOM is more preferred.

[0184] In one embodiment of the suspension polymerized particles, the fluorine-containing compound having a hydrophilic group contains a compound represented by the following general formula (1): － ] ｉ M ｉ＋ (Wherein, X represents H, Cl, Br, F, or I; Rf represents a linear or branched partially or fully fluorinated aliphatic group, or a linear or branched partially or fully fluorinated aliphatic group interrupted by at least one oxygen atom; A － is an acid group, M ｉ＋ represents a cation having a valence i, where i is an integer from 1 to 3.

[0185] In one embodiment of the suspension polymerized particles, the fluorine-containing compound having a hydrophilic group contains a compound represented by the following general formula (2): General formula (2): [C ｎ－１ F ２ｎ－１ COO － ]M ＋ (wherein n is an integer of 9 to 14, M ＋ represents a cation.)

[0186] The compound represented by general formula (2) (perfluoroalkanoic acid) is known to be formed during polymerization when perfluoroalkyl vinyl ether or the like is used as a modified monomer (see WO 2019 / 161153).

[0187] In one embodiment of the suspension polymerized particles, the fluorine-containing compound having a hydrophilic group contains a compound represented by the following general formula (3): General formula (3): [R １ -O-L-CO ２ － ]M ＋ (In the formula, R １ represents a linear or branched partially or fully fluorinated aliphatic group, or a linear or branched partially or fully fluorinated aliphatic group interrupted by at least one oxygen atom; L represents a linear or branched non-fluorinated, partially fluorinated or fully fluorinated alkylene group; M represents a ＋ represents a cation.)

[0188] In one embodiment of the suspension polymerized particles, the fluorine-containing compound having a hydrophilic group contains a compound represented by general formula (4). General formula (4): [H—(CF ２ ) ｍ CO ２ － ]M ＋ (wherein m is an integer of 3 to 19, M ＋ represents a cation.)

[0189] The suspension-polymerized particles obtained may be washed and then pulverized, or the suspension-polymerized particles obtained may be pulverized while being washed, to produce pulverized particles.

[0190] Suspension polymerized particles obtained by suspension polymerization are usually obtained in a wet state. In the production method of the present disclosure, the suspension polymerized particles in a wet state may be pulverized, or the suspension polymerized particles in a wet state may be dried and then pulverized. The pulverization may be wet pulverization or dry pulverization.

[0191] Examples of methods for pulverizing suspension-polymerized particles include pulverization using a pulverizer. Examples of pulverizers include impact pulverizers such as hammer mills, pin mills, high-speed rotary mills, and jet mills, and attrition pulverizers such as cutter mills, feather mills, and colloid mills that pulverize by shearing forces generated by a rotary blade and an outer stator (fixed blade). A combination of pulverizers may be used for pulverization.

[0192] The temperature at which the grinding treatment is carried out is preferably −200 to 50° C., more preferably 1° C. or higher, more preferably 40° C. or lower, and even more preferably 30° C. or lower.

[0193] The method of pulverizing the suspension polymerized particles while washing them includes a method of pulverizing the suspension polymerized particles in water or an organic solvent. For example, water or an organic solvent and the suspension polymerized particles may be simultaneously supplied to a grinding type grinder such as a cutter mill and pulverized, or water or an organic solvent and the suspension polymerized particles may be mixed in advance, and the mixture may be supplied to a grinder and pulverized.

[0194] Before the suspension-polymerized particles are pulverized, the suspension-polymerized particles may be washed. Water or an organic solvent can be used to wash the suspension-polymerized particles. Washing may be performed once or multiple times.

[0195] Examples of organic solvents used for washing include ethers, halogenated hydrocarbons, aromatic hydrocarbons, pyridine, nitriles, nitrogen-containing polar organic compounds, dimethyl sulfoxide, and alcohols.

[0196] The pulverization may be carried out once, or may be carried out repeatedly until pulverized particles having a desired average particle size or a desired particle size distribution are produced.

[0197] The pulverized particles obtained by pulverization are usually obtained in a wet state. After pulverization, the pulverized particles have a moisture content of, for example, more than 40% by mass before dehydration. In the above-mentioned production method, the wet pulverized particles may be dehydrated. Examples of the method for dehydrating the wet pulverized particles include a method using a dehydrator. Examples of the dehydrator include a vibration dehydrator, a filtration dehydrator, and a centrifugal dehydrator. The dehydration is preferably carried out at a temperature below 50°C. The dehydration temperature is the temperature of the atmosphere surrounding the pulverized particles.

[0198] The wet pulverized particles may be dehydrated and further dried. Drying is carried out for the purpose of removing moisture from the pulverized particles obtained by pulverization. Examples of a method for drying the wet pulverized particles include a method using a dryer.

[0199] Examples of the dryer include a hot air heat receiving dryer, a conduction heat receiving dryer, a radiation heat transfer dryer, a high frequency heat transfer dryer, etc. Examples of the dryer include a material static dryer, a material transfer dryer, a material agitation dryer, a material conveying dryer, etc.

[0200] Examples of hot air heat-receiving type material stationary dryers and material transport dryers include box dryers, tunnel dryers, band dryers, turbo vertical dryers, vertical dryers, belt dryers, etc. Examples of hot air heat-receiving type material agitation dryers include fluidized bed dryers, ventilated rotary dryers, grooved agitation dryers, multi-stage disk dryers, etc. Examples of hot air heat-receiving type material transport dryers include flash dryers and spray dryers (jet flow dryers, spray dryers).

[0201] Examples of conductive heat-receiving type stationary dryers and material-transfer dryers include vacuum box dryers, cylindrical dryers, vibration dryers, vacuum heat treatment dryers, freeze dryers, and drum dryers. Examples of conductive heat-receiving type agitation dryers include cylindrical dryers, groove dryers, inverted cone dryers, extrusion dryers, and steam-heated tube bundle rotary dryers.

[0202] Examples of the radiation heat transfer type stationary material dryer and material transfer type dryer include an infrared dryer and a superheated steam dryer.

[0203] Examples of the high-frequency heat transfer type stationary material dryer and material transfer type dryer include a high-frequency dryer and a microwave dryer.

[0204] In one embodiment, the ground particles are dried by flash drying, which can be performed using a flash dryer.

[0205] After drying the pulverized particles by flash drying, the solid-gas mixture containing the dried pulverized particles and gas may be separated into the pulverized particles and the gas using a cyclone or the like, and the pulverized particles may be recovered.

[0206] The temperature at which the pulverized particles are dried is preferably less than 300°C, more preferably 280°C or less, even more preferably 250°C or less, still more preferably less than 200°C, particularly preferably less than 180°C, most preferably less than 160°C, and preferably 50°C or more, more preferably 100°C or more. The drying temperature is the temperature of the atmosphere surrounding the pulverized particles, and when hot air is used for drying, it can be determined by measuring the temperature of the hot air. The temperature of the hot air can be measured at the supply port that supplies hot air to the dryer or the exhaust port that exhausts hot air from the dryer, but is preferably measured at the exhaust port.

[0207] The moisture content of the pulverized particles is preferably 40% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, even more preferably 1% by mass or less, even more preferably 0.1% by mass or less, even more preferably 0.010% by mass or less, even more preferably 0.005% by mass or less, even more preferably 0.003% by mass or less, even more preferably 0.002% by mass or less, and particularly preferably 0.001% by mass or less. The moisture content of the pulverized particles can be adjusted, for example, by dehydrating or drying the pulverized particles. The moisture content of the pulverized particles can be calculated, for example, by heating the pulverized particles at 150°C for 2 hours to thoroughly dry them, measuring the mass of the pulverized particles before and after heating, and then calculating the moisture content according to the following formula: Moisture content (mass%) = [(mass (g) of pulverized particles before heating) - (mass (g) of pulverized particles after heating)] / (mass (g) of pulverized particles after heating) x 100

[0208] After the suspension polymerized particles are pulverized, the pulverized particles obtained may be classified by a known method such as air classification, etc. By classifying, fine particles having very small particle diameters and coarse particles having very large particle diameters can be removed, thereby obtaining pulverized particles having a desired average particle diameter or a desired particle size distribution.

[0209] The average particle size of the pulverized particles is preferably 800 μm or less, more preferably 600 μm or less, even more preferably 400 μm or less, preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, even more preferably 100 μm or more, particularly preferably 150 μm or more, and most preferably more than 200 μm. As described above, the pulverized particles often have a torn shape or a large, flat shape due to the pulverization process. Usually, they often have a scaly particle shape. In this specification, "PTFE particles with a particle size of 1 μm or more" refers to the scaly particles.

[0210] The resulting pulverized particles may be granulated by a known granulation method.

[0211] The mixing in step (A) can be carried out by a known method.

[0212] The coagulation in step (B) can be carried out by a known method.

[0213] In step (C), the drying is usually carried out by means of vacuum, high frequency, hot air, etc., while keeping the wet powder in a state where it is not fluidized much, preferably in a static state. Friction between powders, especially at high temperatures, generally has an undesirable effect on fine powder PTFE. This is because particles made of this type of PTFE have the property of easily fibrillating even with a small shear force, losing their original stable particle structure.

[0214] In step (C), the wet powder obtained in step (B) is preferably placed in a container whose bottom and / or sides are air permeable, and heat-treated for 2 hours or more at a temperature of 130 to 300° C. By carrying out heat treatment under such extremely limited conditions, the fluorine-containing compound having a molecular weight of 1,000 or less can be efficiently removed together with water, and the contents of the fluorine-containing compound and water can be kept within the above-mentioned ranges.

[0215] The temperature of the heat treatment in step (C) is preferably 140°C or higher, more preferably 150°C or higher, even more preferably 160°C or higher, still more preferably 180°C or higher, still more preferably 200°C or higher, particularly preferably 220°C or higher, and is preferably 280°C or lower, more preferably 250°C or lower, from the viewpoint of more efficiently removing moisture and fluorine-containing compounds.

[0216] The time for the heat treatment in step (C) is preferably 5 hours or more, more preferably 10 hours or more, and even more preferably 15 hours or more, from the viewpoint of more efficiently removing moisture and the fluorine-containing compound. The upper limit is not particularly limited, but is, for example, preferably 100 hours, more preferably 50 hours, and even more preferably 30 hours.

[0217] The air velocity in step (C) is preferably 0.01 m / s or more, more preferably 0.03 m / s or more, even more preferably 0.05 m / s or more, and even more preferably 0.1 m / s or more, from the viewpoint of more efficiently removing moisture and fluorine-containing compounds, and is preferably 50 m / s or less, more preferably 30 m / s or less, and even more preferably 10 m / s or less, from the viewpoint of suppressing scattering of powder.

[0218] The heat treatment in step (C) can be carried out using an electric furnace or a steam furnace. For example, it can be carried out using an electric furnace such as a parallel-flow box-type electric furnace, a ventilated box-type electric furnace, a ventilated conveyor-type electric furnace, a band furnace, a radiant conveyor-type electric furnace, a fluidized-bed electric furnace, a vacuum electric furnace, an agitator-type electric furnace, an airflow-type electric furnace, or a hot-air circulation electric furnace, or a steam furnace corresponding to the above (an apparatus obtained by replacing the electric furnace in the apparatus name of each electric furnace with a steam furnace). In terms of being able to remove moisture and fluorine-containing compounds more efficiently, a parallel-flow box-type electric furnace, a ventilated box-type electric furnace, a ventilated conveyor-type electric furnace, a band furnace, a fluidized-bed electric furnace, a hot-air circulation electric furnace, or a steam furnace corresponding to the above (an apparatus obtained by replacing the electric furnace in the apparatus name of each electric furnace with a steam furnace) is preferred.

[0219] The heat treatment in step (C) is preferably carried out by placing the wet powder in a container whose bottom and / or sides are breathable, since this allows for more efficient removal of moisture and fluorine-containing compounds. The container whose bottom and / or sides are breathable may be any container that can withstand the heat treatment temperature, but is preferably made of a metal such as stainless steel. The container whose bottom and / or sides are breathable is preferably a tray (bath) whose bottom and / or sides are breathable, and more preferably a tray whose bottom and / or sides are made of mesh (mesh tray). The mesh is preferably either a woven mesh or a punched metal. The mesh opening is preferably 2000 μm or less (ASTM standard 10 mesh or more), more preferably 595 μm or less (30 mesh or more), even more preferably 297 μm or less (50 mesh or more), even 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). When the mesh is a woven net, the weaving method may be, for example, plain weave, twill weave, plain dutch weave, or twill dutch weave. When the mesh is a punched metal, the opening rate is preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more. Furthermore, it is preferably 95% or less.

[0220] In the step (C), the amount of the wet powder to be placed is 10 g / cm from the viewpoint of more efficiently removing moisture and fluorine-containing compounds. ２ Preferably, it is 8 g / cm or less. ２ More preferably, it is 5 g / cm or less. ２ More preferably, it is 3 g / cm or less. ２ It is particularly preferable that the density is 0.01 g / cm or less. ２ It is preferable that the density is 0.05 g / cm or more. ２ More preferably, it is 0.1 g / cm or more. ２ More preferably, it is equal to or greater than this.

[0221] The moisture content of the moist powder to be heat-treated in step (C) 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 moist powder, in order to more efficiently remove moisture and the fluorine-containing compound, and is preferably 150% by mass or less, and more preferably 100% by mass or less.

[0222] The PTFE composition of the present disclosure can also be suitably produced by a production method including a step (D) of mixing a PTFE powder obtained by emulsion polymerization with a PTFE powder obtained by suspension polymerization.

[0223] The PTFE powder obtained by emulsion polymerization in step (D) can be produced by coagulating the aqueous dispersion of PTFE obtained by emulsion polymerization, and then drying.The aqueous dispersion can be produced by the same method as the aqueous dispersion of PTFE obtained by emulsion polymerization in step (A).The coagulation and drying can be carried out by the same method as steps (B) and (C).

[0224] The PTFE powder obtained by suspension polymerization in step (D) can be produced by the same method as that for the PTFE powder obtained by suspension polymerization in step (A).

[0225] The mixing in step (D) can be carried out by a known dry mixing method.

[0226] The PTFE composition of the present disclosure is used in a binder for electrochemical devices. In the binder for electrochemical devices, the PTFE composition of the present disclosure may be used alone or in a mixture with other materials (e.g., polymers other than PTFE). However, it is preferable to use the PTFE composition of the present disclosure substantially alone, and more preferably to use it alone. Note that using the PTFE composition of the present disclosure substantially alone means that the amount of the PTFE composition in the binder for electrochemical devices is used within the range described below.

[0227] The present disclosure also provides a binder for electrochemical devices consisting essentially of a PTFE composition, wherein the PTFE composition contains PTFE having a particle size of 1 μm or more (hereinafter also referred to as binder (1) of the present disclosure).

[0228] The present disclosure provides a binder for electrochemical devices consisting essentially of a PTFE composition, wherein the PTFE composition has a specific surface area of ​​0.5 m ２ / g or more 7.0m ２ The present invention also provides a binder for electrochemical devices containing PTFE in an amount of less than 1000 kJ / g (hereinafter also referred to as binder (2) of the present disclosure).

[0229] The present disclosure also provides a binder for electrochemical devices consisting essentially of a PTFE composition, wherein the PTFE composition contains PTFE obtained by suspension polymerization (hereinafter also referred to as binder (3) of the present disclosure).

[0230] In this specification, unless otherwise specified, binders (1) to (3) of the present disclosure will be collectively referred to as "binders of the present disclosure."

[0231] The binder of the present disclosure, containing a specific PTFE composition, is less likely to form agglomerates even when kneaded for a long period of time with powder components of electrochemical devices, such as electrode active materials and solid electrolytes, and can be uniformly mixed with the powder components. It is also possible to obtain a composite sheet with excellent strength and flexibility. The binder of the present disclosure also eliminates the need to use 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. It also reduces the steps and costs associated with the use of dispersion media. Furthermore, the binder of the present disclosure has excellent binding strength with active materials and electrolytes, allowing for reduced usage amounts.

[0232] As the PTFE composition in the binder of the present disclosure, the same PTFE composition as the above-described PTFE composition of the present disclosure can be used, and the preferred embodiments are also the same.

[0233] The binder of the present disclosure consists essentially of the PTFE composition. This allows the effects of the PTFE composition to be significantly exhibited. "Consisting essentially of the PTFE composition" means that the content of the PTFE composition is 95.0% by mass or more relative to the binder. The content of the PTFE composition is preferably 98.0% by mass or more relative to the binder, more preferably 99.0% by mass or more, even more preferably 99.5% by mass or more, particularly preferably 99.9% by mass or more, and most preferably 99.95% by mass or more. It is also preferable that the binder of the present disclosure consists essentially of the PTFE composition.

[0234] The binder of the present disclosure is preferably substantially free of organic solvents. This allows for reduction in steps and costs associated with the use of organic solvents. "Substantially free of organic solvents" means that the organic solvent content relative to the binder is 5% by mass or less. The organic solvent content is preferably 3% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, even more preferably 0.01% by mass or less, and particularly preferably 0.001% by mass or less.

[0235] The binder of the present disclosure is preferably in the form of a powder.

[0236] The binder of the present disclosure is used in electrochemical devices such as batteries and capacitors. Examples of batteries include secondary batteries such as lithium ion batteries. 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.

[0237] The binder of the present disclosure can be suitably used as a battery binder, and particularly suitably used as a binder for secondary batteries such as lithium ion batteries. The binder of the present disclosure may be used to prepare electrochemical device components, preferably battery components. The binder of the present disclosure can be particularly suitably used as an electrode binder. The binder of the present disclosure can also be suitably used as a binder in the solid electrolyte layer of a solid secondary battery.

[0238] The present disclosure also provides an electrode mixture containing the PTFE composition or binder of the present disclosure and an electrode active material. The use of the electrode mixture of the present disclosure allows the powder components of an electrochemical device to be uniformly dispersed, resulting in a mixture sheet with excellent strength and flexibility. Furthermore, because the electrode active material can be held in place even with a small amount of binder, more materials that improve the electrochemical device properties, such as active materials and conductive additives, can be added.

[0239] Examples of the electrode active material include a positive electrode active material and a negative electrode active material.

[0240] The positive electrode active material is not particularly limited as long as it can electrochemically absorb and release alkali metal ions, but for example, a material containing an alkali metal and at least one transition metal is preferred. Specific examples include alkali metal-containing transition metal composite oxides and alkali metal-containing transition metal phosphate compounds. Of these, alkali metal-containing transition metal composite oxides that generate high voltage are particularly preferred as the positive electrode active material. Examples of the alkali metal ions include lithium ions, sodium ions, and potassium ions. In a preferred embodiment, the alkali metal ions may be lithium ions. That is, in this embodiment, the alkali metal ion secondary battery is a lithium ion secondary battery.

[0241] Examples of the alkali metal-containing transition metal composite oxide include those represented by the formula: M ａ Mn ２－ｂ M １ ｂ O ４ (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 is 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), alkali metal-manganese spinel composite oxides (such as lithium-manganese spinel composite oxides) represented by the formula: MNi １－ｃ M ２ ｃ O ２ (Wherein, M is at least one metal selected from the group consisting of Li, Na, and K; 0≦c≦0.5; M ２ is 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 an alkali metal-nickel composite oxide (such as a lithium-nickel composite oxide) represented by the formula: MCo １－ｄ M ３ ｄ O ２ (Wherein, M is at least one metal selected from the group consisting of Li, Na, and K; 0≦d≦0.5; M ３is 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. In 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.

[0242] Among these, MCoO is preferred because it can provide a secondary battery with high energy density and high output. ２ , M MnO ２ , MNiO ２ , M.M. ２ O ４ , MNi ０．８ Co ０．１５ Al ０．０５ O ２ , or MNi １／３ Co １／３ Mn １／３ O ２ and the like are preferred, and a compound represented by the following general formula (3) is preferred: MNi ｈ Co ｉ Mn ｊ M ５ ｋ O ２ (3) (wherein M is at least one metal selected from the group consisting of Li, Na, and K, and M ５ represents 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, and (h+i+j+k)=1.0, 0≦h≦1.0, 0≦i≦1.0, 0≦j≦1.5, 0≦k≦0.2.

[0243] Examples of the alkali metal-containing transition metal phosphate compound include those represented by the following general formula (4): ｅ M ４ ｆ (P.O. ４ ) ｇ (4) (wherein M is at least one metal selected from the group consisting of Li, Na, and K, and M ４represents at least one selected from the group consisting of V, Ti, Cr, Mn, Fe, Co, Ni, and Cu, and 0.5≦e≦3, 1≦f≦2, and 1≦g≦3. In 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. That is, the alkali metal-containing transition metal phosphate compound is preferably a lithium-containing transition metal phosphate compound.

[0244] The transition metal of the lithium-containing transition metal phosphate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, or the like, and specific examples thereof include LiFePO ４ , Li ３ Fe ２ (P.O. ４ ) ３ , LiFeP ２ O ７ Iron phosphates such as LiCoPO ４ and lithium transition metal phosphate compounds in which a part of the transition metal atoms constituting the main component of these compounds is substituted with other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc. The lithium-containing transition metal phosphate compounds preferably have an olivine structure.

[0245] Other examples of the positive electrode active material include lithium-nickel composite oxides. The lithium-nickel composite oxides are represented by the following general formula (5): Li ｙ Ni １－ｘ M ｘ O ２ (5) (wherein x is 0.01≦x≦0.7, y is 0.9≦y≦2.0, and M is a metal atom (excluding Li and Ni)) is preferred.

[0246] Other positive electrode active materials include MFePO ４ , MNi ０．８ Co ０．２ O ２ , M １．２ Fe ０．４ Mn ０．４ O ２, MNi ０．５ Mn １．５ O ２ , M.V. ３ O ６ , M ２ MnO ３ In particular, M ２ MnO ３ , MNi ０．５ Mn １．５ O ２ These positive electrode active materials are preferred in that their crystalline structure does not collapse even when the secondary battery is operated at a voltage exceeding 4.4 V or a voltage of 4.6 V or higher. Therefore, electrochemical devices such as secondary batteries using positive electrode materials containing the above-mentioned positive electrode active materials are preferred because they are less likely to reduce their remaining capacity and change their resistance increase rate even when stored at high temperatures, and their battery performance does not deteriorate even when operated at high voltages.

[0247] Other positive electrode active materials include M ２ MnO ３ and M.M. ６ O ２ (wherein M is at least one metal selected from the group consisting of Li, Na, and K, and M ６ Examples of the material include solid solution materials with transition metals such as Co, Ni, Mn, and Fe.

[0248] The solid solution material may be, for example, a material represented by the general formula Mx [Mn （１－ｙ） M ７ ｙ ]O ｚ In the formula, M 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, and contains, for example, one or more elements selected from the group consisting of Co, Ni, Fe, Ti, Mo, W, Cr, Zr and Sn. The values ​​of x, y and z in the formula are in the ranges 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 O ２ Li like ２ MnO ３ Based on LiNiO２ and LiCoO ２ A manganese-containing solid solution material containing manganese is preferred in that it can provide an alkali metal ion secondary battery having a high energy density.

[0249] Furthermore, it is preferable to include lithium phosphate in the positive electrode active material, since this improves continuous charging characteristics. Although there is no limitation on the use of lithium phosphate, it is preferable to use a mixture of the positive electrode active material and lithium phosphate. The amount of lithium phosphate used, based on the total amount of the positive electrode active material and lithium phosphate, is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, and is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less.

[0250] Alternatively, a substance having a different composition may be attached to the surface of the positive electrode active material, such as an oxide, such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, or bismuth oxide; a sulfate, such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, or aluminum sulfate; a carbonate, such as lithium carbonate, calcium carbonate, or magnesium carbonate; or carbon.

[0251] These surface-attaching substances can be attached to the surface of the positive electrode active material by, for example, a method of dissolving or suspending the substance in a solvent, impregnating the positive electrode active material, and then drying, a method of dissolving or suspending a surface-attaching substance precursor in a solvent, impregnating the positive electrode active material, and then reacting the surface-attaching substance by heating, or a method of adding the substance to a positive electrode active material precursor and simultaneously baking the surface-attaching substance, etc. When carbon is attached, a method of mechanically attaching the carbonaceous material in the form of, for example, activated carbon, etc., after the surface-attaching substance is also available.

[0252] The amount of the surface-attached substance is, by mass relative to the positive electrode active material, preferably 0.1 ppm or more as the lower limit, more preferably 1 ppm or more, and even more preferably 10 ppm or more, and preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less as the upper limit. The surface-attached substance can suppress the oxidation reaction of the electrolyte on the surface of the positive electrode active material and improve the battery life, but if the amount of attachment is too small, the effect will not be fully exerted, and if it is too large, the movement of lithium ions into and out of the positive electrode active material will be hindered, which may increase the resistance.

[0253] The shape of the particles of the positive electrode active material may be any of the conventional shapes such as block, polyhedron, sphere, oval sphere, plate, needle, column, etc. Furthermore, primary particles may aggregate to form secondary particles.

[0254] 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 ３ That is all. If the tap density of the positive electrode active material is below the above lower limit, the amount of dispersion medium required when forming the positive electrode active material layer increases, and the amounts of conductive material and binder required also increase, which may restrict the filling rate of the positive electrode active material in the positive electrode active material layer and restrict the battery capacity. By using a composite oxide powder with a high tap density, a high-density positive electrode active material layer can be formed. Generally, the higher the tap density, the more preferable it is, and there is no particular upper limit. However, if the tap density is too high, the diffusion of lithium ions in the positive electrode active material layer using the electrolyte as a medium becomes rate-limiting, and the load characteristics may be easily reduced. Therefore, the upper limit is preferably 4.0 g / cm. ３ or less, more preferably 3.7 g / cm ３ More preferably 3.5 g / cm or less ３ The tap density is the powder packing density (tap density) g / cm when 5 to 10 g of the positive electrode active material powder is placed in a 10 ml glass measuring cylinder and tapped 200 times with a stroke of about 20 mm. ３ is required.

[0255] The median diameter d50 of the particles of the positive electrode active material (the secondary particle diameter when primary particles are aggregated to form secondary particles) is preferably 0.3 μm or more, more preferably 0.5 μm or more, even more preferably 0.8 μm or more, and most preferably 1.0 μm or more, and is preferably 30 μm or less, more preferably 27 μm or less, even more preferably 25 μm or less, and most preferably 22 μm or less. If it is below the lower limit, a high tap density product may not be obtained, and if it exceeds the upper limit, it may take a long time for lithium to diffuse within the particles, resulting in problems such as a decrease in battery performance. Here, by mixing two or more types of the above positive electrode active materials having different median diameters d50, the filling ability during positive electrode production can be further improved.

[0256] The median diameter d50 is measured using a known laser diffraction / scattering particle size distribution analyzer. When using a HORIBA LA-920 particle size distribution analyzer, the measurement is performed using a 0.1% by mass aqueous solution of sodium hexametaphosphate as the dispersion medium, and after ultrasonic dispersion for 5 minutes, the measurement is performed with a refractive index set to 1.24.

[0257] When primary particles aggregate to form secondary particles, the average primary particle diameter of the positive electrode active material is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.2 μm or more. The upper limit is preferably 5 μm or less, more preferably 4 μm or less, even more 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 may adversely affect powder packing and significantly reduce the specific surface area, thereby increasing the possibility of battery performance, such as output characteristics, being degraded. Conversely, if the lower limit is exceeded, problems such as poor charge / discharge reversibility may occur due to underdeveloped crystals. The average primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at 10,000x magnification, the longest intercepts of the horizontal line at the left and right boundaries of the primary particles are determined for any 50 primary particles, and the average is calculated.

[0258] 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 / g or less. If the BET specific surface area is smaller than this range, battery performance is likely to decrease, while if it is larger, it is difficult to increase the tap density, which may lead to problems with processability when forming the positive electrode active material layer. The BET specific surface area is defined as a value measured by a nitrogen adsorption BET single-point method using a surface area meter (e.g., a fully automatic surface area measuring device manufactured by Ohkura Riken Co., Ltd.) after pre-drying a sample at 150°C for 30 minutes under a nitrogen flow, using a nitrogen-helium mixed gas accurately adjusted so that the relative pressure of nitrogen to atmospheric pressure is 0.3.

[0259] When the secondary battery of the present disclosure is used as a large-scale lithium-ion secondary battery for hybrid vehicles or distributed power sources, high output is required, so it is preferable that the particles of the positive electrode active material are mainly secondary particles. The particles of the positive electrode active material preferably have an average secondary particle size of 40 μm or less and contain 0.5 to 7.0 volume % of fine particles having an average primary particle size of 1 μm or less. The inclusion of fine particles having an average primary particle size of 1 μm or less increases the contact area with the electrolyte, allowing for faster diffusion of lithium ions between the electrode mixture and the electrolyte, thereby improving the output performance of the battery.

[0260] As a method for producing a positive electrode active material, a general method for producing an inorganic compound is used. In particular, various methods can be considered for producing a spherical or oval-spherical active material. For example, a raw material of a transition metal is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to produce and recover a spherical precursor. This is then dried as necessary, and then the precursor is dissolved in LiOH, Li ２ CO ３ , LiNO ３ and baking at a high temperature to obtain an active material.

[0261] For the production of a positive electrode, the positive electrode active material may be used alone, or two or more types of different compositions may be used in any combination or ratio. In this case, a preferred combination is LiCoO ２ and LiNi ０．３３ Co ０．３３ Mn ０．３３ O ２ combination with ternary systems such as LiCoO ２ and LiMn ２ O ４ Or a combination of this with a material in which a part of Mn is replaced with another transition metal, or LiFePO ４ and LiCoO ２ Alternatively, a combination of Co with other transition metals or the like may be used.

[0262] The content of the positive electrode active material is preferably 50 to 99.5% by mass of the positive electrode mixture, more preferably 80 to 99% by mass, in terms of high battery capacity. 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. The upper limit is preferably 99% by mass or less, 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 electrical capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.

[0263] The negative electrode active material is not particularly limited, and examples thereof include carbonaceous materials such as lithium metal, artificial graphite, graphite carbon fiber, resin-baked carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-baked carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon; silicon-containing compounds such as silicon and silicon alloys; Li ４ Ti ５ O １２ Among these, those containing at least a carbonaceous material and silicon-containing compounds are particularly suitable.

[0264] The negative electrode active material used in the present disclosure preferably contains silicon as a constituent element, which allows the production of a high-capacity battery.

[0265] The silicon-containing material is preferably silicon particles, particles having a structure in which silicon fine particles 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, a negative electrode mixture for a lithium ion secondary battery having higher initial charge / discharge efficiency, high capacity, and excellent cycle characteristics can be obtained.

[0266] In this disclosure, silicon oxide is a general term for amorphous silicon oxide, and silicon oxide before disproportionation is represented by the general formula SiOx (0.5≦x≦1.6). Preferably, x is 0.8≦x<1.6, and more preferably 0.8≦x<1.3. This silicon oxide can be obtained, for example, by heating a mixture of silicon dioxide and metallic silicon to produce silicon monoxide gas, which is then cooled and precipitated.

[0267] Particles having a structure in which silicon microparticles are dispersed in a silicon-based compound can be obtained, for example, by firing a mixture of silicon microparticles and a silicon-based compound, or by heat-treating pre-disproportionation silicon oxide particles 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 to 1,100°C, to carry out a disproportionation reaction. Materials obtained by the latter method are particularly suitable because the silicon microcrystals are uniformly dispersed. The disproportionation reaction described above can reduce the size of silicon nanoparticles to 1 to 100 nm. The silicon oxide in particles having a structure in which silicon nanoparticles are dispersed in silicon oxide is preferably silicon dioxide. The dispersion of silicon nanoparticles (crystals) in amorphous silicon oxide can be confirmed using a transmission electron microscope.

[0268] 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 to 50 μm, with the lower limit being more preferably 0.2 μm or more, and even more preferably 0.5 μm or more. The upper limit is more preferably 30 μm or less, and even more preferably 20 μm or less. The average particle size is expressed as the weight-average particle size measured by particle size distribution measurement using a laser diffraction method.

[0269] BET specific surface area: 0.5 to 100 m ２ / g is preferred, and 1 to 20m ２ / g is more preferable. ２ If the adhesive strength is 100 m / g or more, there is no risk of the adhesive strength decreasing when processed into an electrode, and the battery characteristics decreasing. ２ / g or less, the proportion of silicon dioxide on the particle surface is large, and there is no risk of a decrease in battery capacity when used as a negative electrode material for a lithium ion secondary battery.

[0270] The silicon-containing particles are coated with carbon to impart conductivity, thereby improving battery performance. Methods for imparting conductivity include mixing with conductive particles such as graphite, coating the surfaces of the silicon-containing particles with a carbon coating, and combining both methods. The carbon coating method is preferred, and chemical vapor deposition (CVD) is more preferred.

[0271] In order to increase the capacity of the resulting electrode mixture, the content of the negative electrode active material is preferably 40% by mass or more, more preferably 50% by mass or more, and particularly preferably 60% by mass or more, of the electrode mixture, and the upper limit is preferably 99% by mass or less, more preferably 98% by mass or less.

[0272] The electrode mixture of the present disclosure preferably further contains a conductive aid. Any known conductive material can be used as the conductive aid. Specific examples include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, and carbon materials such as needle coke, carbon nanotubes, fullerenes, and amorphous carbon such as VGCF. These materials may be used alone or in any combination and ratio of two or more.

[0273] The conductive additive is used in an amount of typically 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and typically 50% by mass or less, preferably 30% by mass or less, more preferably 15% by mass or less, in the electrode mixture. If the content is lower than this range, the conductivity may be insufficient. Conversely, if the content is higher than this range, the battery capacity may decrease.

[0274] The electrode mixture of the present disclosure may further contain a thermoplastic resin. Examples of the thermoplastic resin include polyvinylidene fluoride, polypropylene, polyethylene, polystyrene, polyethylene terephthalate, and polyethylene oxide. One type may be used alone, or two or more types may be used in any combination and ratio.

[0275] The ratio of the thermoplastic resin to the electrode active material is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.10% by mass or more, and usually 3.0% by mass or less, preferably 2.5% by mass or less, more preferably 2.0% by mass or less. Adding the thermoplastic resin can improve the mechanical strength of the electrode. Furthermore, if the ratio exceeds this range, the ratio of the electrode active material in the electrode mixture decreases, which may cause problems such as a decrease in battery capacity or an increase in resistance between the active materials.

[0276] In the electrode mixture of the present disclosure, the binder content may be 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.5% by mass or more, and may be 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 10% by mass or less, particularly preferably 5% by mass or less, and most preferably 3% by mass or less. If the binder content is too low, the electrode mixture active material may not be sufficiently retained, resulting in insufficient mechanical strength of the electrode mixture sheet and deterioration of battery performance such as cycle characteristics. On the other hand, if the binder content is too high, it may lead to a decrease in battery capacity and conductivity. Because the binder of the present disclosure has excellent binding strength, even a small content can sufficiently retain the electrode active material.

[0277] In the electrode mixture of the present disclosure, the binder component preferably consists essentially of the PTFE composition, more preferably the PTFE composition. The binder component consisting essentially of the PTFE composition means that the content of the PTFE composition in the binder component constituting the electrode mixture is 95.0% by mass or more relative to the binder component. The content of the PTFE composition is preferably 98.0% by mass or more, more preferably 99.0% by mass or more, even more 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 binder component.

[0278] The electrode mixture of the present disclosure is preferably in the form of a sheet.

[0279] The electrode mixture of the present disclosure can be suitably used as an electrode mixture for secondary batteries. In particular, the electrode mixture of the present disclosure is suitable for lithium ion secondary batteries. When used in secondary batteries, the electrode mixture of the present disclosure is usually used in the form of a sheet.

[0280] The electrode mixture sheet preferably has a thickness of 300 μm or less, more preferably 250 μm or less, even more preferably 200 μm or less, even more preferably 180 μm or less, particularly preferably 150 μm or less, and preferably 10 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more.

[0281] An example of a specific method for producing an electrode mixture sheet containing an electrode mixture is shown below. The electrode mixture sheet can be obtained by a production method including the steps of: (1) mixing a raw material composition containing an electrode active material, a binder, and, if necessary, a conductive additive; (2) forming the raw material composition obtained in the step (1) into a bulk; and (3) rolling the bulk raw material composition obtained in the step (2) into a sheet.

[0282] At the stage where the raw material composition is mixed in the above step (1), the raw material composition is simply a mixture of the electrode active material, binder, etc. and exists in a state without a definite shape. Specific mixing methods include mixing methods using a W-type mixer, V-type mixer, drum mixer, ribbon mixer, conical screw mixer, single-screw kneader, twin-screw kneader, mix muller, stirring mixer, planetary mixer, etc.

[0283] In the above step (1), the binder mixing condition is preferably 3000 rpm or less. It is preferably 10 rpm or more, more preferably 15 rpm or more, and even more preferably 20 rpm or more, and is preferably 2000 rpm or less, more preferably 1500 rpm or less, and even more preferably 1000 rpm or less. If the mixing speed is below the above range, it takes a long time to mix, which affects productivity. Furthermore, if the speed is above the above range, fibrillation may proceed excessively, resulting in an electrode mixture sheet with poor strength and flexibility.

[0284] In the above step (2), forming into a bulk form refers to forming the raw material composition into a single mass. Specific methods for forming into a bulk form include extrusion molding, press molding, etc. Furthermore, the term "bulk form" does not specify a particular shape, and may refer to a state in which the raw material composition is in the form of a single mass, including rod-like, sheet-like, spherical, cube-like, and other shapes.

[0285] Specific examples of the rolling method in the step (3) include rolling methods using a roll press, a plate press, a calender roll, or the like.

[0286] It is also preferable to include a step (4) after step (3), in which a larger load is applied to the obtained rolled sheet to roll it into an even thinner sheet. It is also preferable to repeat step (4). In this way, by rolling the rolled sheet little by little in stages rather than thinning it all at once, flexibility is improved. The number of times step (4) is performed is preferably from 2 to 10 times, and more preferably from 3 to 9 times. Specific rolling methods include, for example, a method in which two or more rolls are rotated and the rolled sheet is passed between them to process it into an even thinner sheet.

[0287] From the viewpoint of adjusting the fibril diameter, it is also preferable to include a step (5) after step (3) or step (4) in which the rolled sheet is roughly crushed, then re-formed into a bulk form, and rolled into a sheet. It is also preferable to repeat step (5). The number of times step (5) is performed is preferably from 1 to 12 times, more preferably from 2 to 11 times.

[0288] In step (5), specific methods for roughly crushing the rolled sheet and forming it into a bulk form include folding the sheet, forming it into a rod or thin film sheet, chipping, etc. In the present disclosure, "rough crushing" means changing the form of the rolled sheet obtained in step (3) or (4) into a different form in order to roll it into a sheet in the next step, and also includes simply folding the rolled sheet.

[0289] Furthermore, step (4) may be performed after step (5), or may be repeated. Furthermore, uniaxial or biaxial stretching may be performed in steps (2), (3), (4), and (5). Furthermore, the fibril diameter can be adjusted by the degree of crushing in step (5).

[0290] In the above steps (3), (4), or (5), the rolling ratio 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 rolling ratio is below the above range, the number of rolling operations increases, which takes time and affects productivity. If the rolling ratio is above the above range, fibrillation may proceed excessively, resulting in an electrode mixture sheet with poor strength and flexibility. The rolling ratio here refers to the reduction rate of the thickness of the sample after processing relative to the thickness before rolling. The sample before rolling may be a bulk raw material composition or a sheet-like raw material composition. The thickness of the sample refers to the thickness in the direction in which a load is applied during rolling.

[0291] The electrode mixture sheet can also be suitably produced by a production method comprising: step (a): mixing powder components and a binder to form an electrode mixture; and step (b): calendaring or extrusion-molding the electrode mixture to produce a sheet, wherein the mixing in step (a) comprises: (a1) homogenizing the powder components and the binder to form a powder; and (a2) mixing the powdered raw material mixture obtained in step (a1) to prepare the electrode mixture.

[0292] For example, PTFE has two transition temperatures at about 19° C. and about 30° C. Below 19° C., PTFE can be easily mixed while maintaining its shape. However, above 19° C., the structure of the PTFE particles becomes looser and more sensitive to mechanical shear. At temperatures above 30° C., a greater degree of fibrillation occurs.

[0293] For this reason, the homogenization of (a1) is preferably carried out at a temperature of 19°C or lower, preferably 0°C to 19°C. That is, in such (a1), it is preferable to mix and homogenize while suppressing fibrillation. The subsequent mixing in (a2) is preferably carried out at a temperature of 30°C or higher to promote fibrillation.

[0294] Preferably, step (a2) is carried out at a temperature of 30° C. to 150° C., more preferably 35° C. to 120° C., even more preferably 40° C. to 100° C. In one embodiment, the calendering or extrusion of step (b) is carried out at a temperature between 30° C. and 150° C., preferably between 35° C. and 120° C., more preferably between 40° C. and 100° C.

[0295] The mixing in step (a) is preferably carried out while applying a shear force. Specific mixing methods include mixing using a W-type mixer, V-type mixer, drum mixer, ribbon mixer, conical screw mixer, single-screw kneader, twin-screw kneader, Mix Muller, stirring mixer, planetary mixer, Henschel mixer, high-speed mixer, etc.

[0296] The mixing conditions may be appropriately set by the rotation speed and mixing time. For example, the rotation speed is preferably 15,000 rpm or less. It is preferably 10 rpm or more, more preferably 50 rpm or more, even more preferably 100 rpm or more, and is preferably 12,000 rpm or less, more preferably 10,000 rpm or less, and even more preferably 8,000 rpm or less. If the rotation speed is below the above range, mixing will take a long time, which will affect productivity. If the rotation speed is above the above range, fibrillation will proceed excessively, which may result in an electrode mixture sheet with inferior strength. It is preferable to perform step (a1) with a weaker shear force than step (a2). It is also desirable to perform step (a1) for a shorter time than step (a2).

[0297] In the step (a2), the raw material composition preferably does not contain a liquid solvent, but a small amount of a lubricant may be used. That is, a lubricant may be added to the powdery raw material mixture obtained in the step (a1) to prepare a paste.

[0298] 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 / paraffin (C10-C16), and mixtures thereof).

[0299] The lubricant preferably has a water content of 1000 ppm or less. A water content of 1000 ppm or less is preferable in that it reduces deterioration of the electrochemical device. The water content is more preferably 500 ppm or less.

[0300] When the above-mentioned lubricant is used, it is particularly preferable that the lubricant is a solvent with low polarity such as butyl butyrate, or an ether compound.

[0301] When the above-mentioned 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, more preferably 15.0 to 25.0 parts by weight, based on the total weight of the composition subjected to step (a1).

[0302] It is preferable that the raw material composition substantially does not contain a liquid medium. Conventional electrode mixture formation methods generally involve preparing a slurry in which powders, which are electrode mixture components, are dispersed using a solvent in which a binder is dissolved, and then preparing an electrode mixture sheet by applying and drying the slurry. In this case, a solvent that disperses or dissolves the binder is used. However, solvents that can dissolve binder resins that have been commonly used in the past are limited to specific solvents such as N-methylpyrrolidone. Because of their high polarity and the need for a drying process, the use of solvents incurs additional steps and costs. Furthermore, these solvents react with electrolytes, such as electrolytic solutions and solid electrolytes, degrading the electrolyte, and residual components during slurry preparation or after drying can cause a decrease in battery performance. Furthermore, low-polarity solvents such as heptane dissolve very limited binder resins, and their low flash points can make handling difficult.

[0303] By using a powder binder with low moisture content without using a solvent when forming the electrode mixture sheet, a battery with little electrolyte deterioration can be manufactured. Furthermore, in the manufacturing method described above, an electrode mixture sheet containing a binder with a fine fibrous structure can be manufactured, and by not preparing a slurry, the burden on the manufacturing process can be reduced.

[0304] Step (b) is calendering or extrusion. Calendering and extrusion can be performed by well-known methods. This allows the electrode mixture to be formed into the shape of an electrode mixture sheet. Step (b) preferably includes (b1) a step of forming the electrode mixture obtained by step (a) into a bulk form, and (b2) a step of calendering or extrusion-molding the bulk electrode mixture.

[0305] Forming into a bulk state means forming the electrode mixture into a single mass. Specific methods for forming into a bulk state include extrusion molding, press molding, and the like. The term "bulk state" does not particularly specify a shape, and may refer to a state in which the electrode mixture is in the form of a single mass, including rods, sheets, spheres, cubes, and the like. The size of the mass is preferably such that the diameter or the shortest side of its cross section is 10,000 μm or more, more preferably 20,000 μm or more.

[0306] Specific examples of the calendering or extrusion molding method in the step (b2) include a method of rolling the electrode mixture using a roll press, a calender roll machine, or the like.

[0307] The step (b) is preferably carried out at 30 to 150° C. As mentioned above, PTFE has a glass transition temperature around 30° C., and therefore, is easily fibrillated at temperatures above 30° C. Therefore, the step (b) is preferably carried out at such a temperature.

[0308] Furthermore, calendering or extrusion applies shear force, which causes the PTFE to fibrillate and form.

[0309] It is also preferable to have a step (c) after step (b) in which a larger load is applied to the obtained rolled sheet to roll it into an even thinner sheet. It is also preferable to repeat step (c). In this way, by rolling the rolled sheet little by little in stages rather than thinning it all at once, flexibility is improved. The number of times step (c) is performed is preferably from 2 to 10 times, and more preferably from 3 to 9 times. Specific rolling methods include, for example, a method in which two or more rolls are rotated and the rolled sheet is passed between them to process it into an even thinner sheet.

[0310] From the viewpoint of adjusting the sheet strength, it is also preferable to include a step (d) after step (b) or step (c) in which the rolled sheet is crushed, re-formed into a bulk form, and rolled into a sheet. It is also preferable to repeat step (d). The number of times step (d) is performed is preferably from 1 to 12 times, more preferably from 2 to 11 times.

[0311] In step (d), specific methods for crushing the rolled sheet and forming it into a bulk form include folding the rolled sheet, forming it into a rod or thin film sheet, chipping, etc. In the present disclosure, "crushing" means changing the form of the rolled sheet obtained in step (b) or (c) into another form in order to roll it into a sheet in the next step, and also includes simply folding the rolled sheet.

[0312] Furthermore, step (c) may be performed after step (d), or these steps may be repeated. Furthermore, uniaxial or biaxial stretching may be performed in steps (a), (b), (c), and (d). Furthermore, the sheet strength can be adjusted by the degree of crushing in step (d).

[0313] In the above steps (b), (c), or (d), the rolling ratio 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 rolling ratio is below the above range, the number of rolling operations increases, which increases the time required and affects productivity. If the rolling ratio is above the above range, excessive fibrillation may occur, resulting in an electrode mixture sheet with poor strength and flexibility. The rolling ratio here refers to the reduction in thickness of the sample after rolling relative to the thickness before rolling. The sample before rolling may be a bulk raw material composition or a sheet-like raw material composition. The thickness of the sample refers to the thickness in the direction in which a load is applied during rolling. The above steps (c) to (d) are preferably performed at 30°C or higher, more preferably 60°C or higher. Furthermore, they are preferably performed at 150°C or lower.

[0314] The electrode mixture sheet can be used as an electrode mixture sheet for a secondary battery. It can be used for either a negative electrode or a positive electrode. The electrode mixture sheet is particularly suitable for a lithium ion secondary battery.

[0315] The present disclosure also provides an electrode comprising the PTFE composition or binder of the present disclosure, an electrode active material, and a current collector. The electrode of the present disclosure has uniformly dispersed powder components of an electrochemical device, and is therefore excellent in strength and flexibility. Furthermore, because the electrode active material can be held in place even with a small amount of binder, it is possible to add more materials that improve the electrochemical device characteristics, such as active materials and conductive additives.

[0316] The electrode of the present disclosure may include the above-described electrode mixture (preferably an electrode mixture sheet) of the present disclosure and a current collector.

[0317] The electrodes of the present disclosure may be positive electrodes or negative electrodes.

[0318] The positive electrode is preferably composed of 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, and nickel, or alloys thereof; and carbon materials such as carbon cloth and carbon paper. Among these, metal materials, particularly aluminum or its alloys, are preferred.

[0319] Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, expanded metal, punched metal, and foam metal in the case of a metal material, and carbon plate, carbon thin film, and carbon cylinder in the case of a carbon material. Of these, metal foil is preferred. The metal foil may be appropriately formed into a mesh shape. The thickness of the metal foil is optional, but is usually 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more, and is usually 1 mm or less, preferably 100 μm or less, and more preferably 50 μm or less. If the metal foil is thinner than this range, the strength required as a current collector may be insufficient. Conversely, if the metal foil is thicker than this range, handling may be impaired.

[0320] In addition, it is also preferable that the surface of the current collector is roughened, from the viewpoint of improving the adhesion between the current collector and the positive electrode active material layer and reducing the electrical contact resistance. The surface roughness of the current collector, expressed as Sa (arithmetic mean height), is preferably about 260 nm or more, more preferably about 280 nm or more, and even more preferably about 300 nm or more.

[0321] In addition, it is also preferable that a conductive additive is applied to the surface of the current collector in order to reduce the electrical contact resistance between the current collector and the positive electrode active material layer. Examples of the conductive additive include carbon and precious metals such as gold, platinum, and silver. Carbon is particularly preferable because of its small weight.

[0322] The positive electrode may be produced by a conventional method, for example, by laminating the electrode mixture sheet and a current collector with an adhesive therebetween, followed by vacuum drying.

[0323] 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 ３or more, and preferably 3.80 g / cm ３ or less, more preferably 3.75 g / cm ３ More preferably, 3.70 g / cm or less ３ The range is as follows. If the temperature exceeds this range, cracks may easily occur within the sheet. If the temperature falls below this range, the conductivity between the active materials may decrease, increasing the battery resistance and making it difficult to obtain high output.

[0324] The thickness of the positive electrode is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the mixture layer minus the thickness of the metal foil of the current collector is preferably 10 μm or more, more preferably 20 μm or more, as a lower limit, and is also preferably 500 μm or less, more preferably 450 μm or less, on one side of the current collector.

[0325] The negative electrode is preferably composed of 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, and stainless steel, or alloys thereof; and carbon materials such as carbon cloth and carbon paper. Among these, metal materials, particularly copper, nickel, and alloys thereof, are preferred.

[0326] Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, expanded metal, punched metal, and foam metal in the case of a metal material, and carbon plate, carbon thin film, and carbon cylinder in the case of a carbon material. Of these, metal foil is preferred. The metal foil may be appropriately formed into a mesh shape. The thickness of the metal foil is optional, but is usually 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more, and is usually 1 mm or less, preferably 100 μm or less, and more preferably 50 μm or less. If the metal foil is thinner than this range, the strength required as a current collector may be insufficient. Conversely, if the metal foil is thicker than this range, handling may be impaired.

[0327] In addition, it is also preferable that the surface of the current collector is roughened, from the viewpoint of improving the adhesion between the current collector and the positive electrode active material layer and reducing the electrical contact resistance. The surface roughness of the current collector, expressed as Sa (arithmetic mean height), is preferably about 260 nm or more, more preferably about 280 nm or more, and even more preferably about 300 nm or more.

[0328] In addition, it is also preferable that a conductive additive is applied to the surface of the current collector in order to reduce the electrical contact resistance between the current collector and the positive electrode active material layer. Examples of the conductive additive include carbon and precious metals such as gold, platinum, and silver. Carbon is particularly preferable because of its small weight.

[0329] The negative electrode may be produced by a conventional method, for example, by laminating the electrode mixture sheet and a current collector with an adhesive therebetween, followed by vacuum drying.

[0330] 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 or more, and preferably 2.0 g / cm ３ or less, more preferably 1.9 g / cm ３ More preferably, 1.8 g / cm or less ３ The range is as follows. If the temperature exceeds this range, cracks may easily occur within the sheet. If the temperature falls below this range, the conductivity between the active materials may decrease, increasing the battery resistance and making it difficult to obtain high output.

[0331] The thickness of the negative electrode is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the mixture layer minus the thickness of the metal foil of the current collector is preferably 10 μm or more, more preferably 20 μm or more, as a lower limit, and is also preferably 500 μm or less, more preferably 450 μm or less, on one side of the current collector.

[0332] The present disclosure also provides a secondary battery comprising the electrode of the present disclosure described above.

[0333] The secondary battery of the present disclosure may be a secondary battery that uses an electrolytic solution or may be a solid-state secondary battery. Note that in this specification, the solid-state secondary battery may be a secondary battery that contains a solid electrolyte, may be a semi-solid-state secondary battery that contains a solid electrolyte and a liquid component as the electrolyte, or may be an all-solid-state secondary battery that contains only a solid electrolyte as the electrolyte.

[0334] The secondary battery using the above-mentioned electrolyte solution can use the electrolyte solution, separator, etc. used in known secondary batteries, which will be described in detail below.

[0335] The electrolyte is preferably a non-aqueous electrolyte, which may be prepared by dissolving a known electrolyte salt in a known organic solvent for dissolving electrolyte salts.

[0336] The organic solvent for dissolving the electrolyte salt is not particularly limited, and one or more of 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 fluorine-based solvents such as fluoroethylene carbonate, fluoroether, and fluorinated carbonate can be used.

[0337] The electrolyte salt is, for example, LiClO ４ , LiAsF ６ , LiBF ４ , LiPF ６ , LiN(SO ２ CF ３ ) ２ , LiN(SO ２ C ２ F ５ ) ２ In particular, LiPF is preferred because of its excellent cycle characteristics. ６ , LiBF ４ , LiN(SO ２ CF ３ ) ２ , LiN(SO ２ C ２ F ５ ) ２ Or a combination of these is preferred.

[0338] 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 or less.

[0339] A secondary battery using the above-mentioned electrolyte solution preferably further includes a separator. The material and shape of the separator are not particularly limited as long as it is stable to the electrolyte solution and has excellent liquid retention properties, and any known separator can be used. Among them, it is preferable to use a material that is stable to the electrolyte solution, such as resin, glass fiber, or inorganic material, and that is in the form of a porous sheet or nonwoven fabric with excellent liquid retention properties.

[0340] Examples of materials that can be used for the resin or glass fiber separator include polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, and glass filters. These materials may be used alone or in any combination and ratio, such as polypropylene / polyethylene two-layer films and polypropylene / polyethylene / polypropylene three-layer films. Among these, porous sheets or nonwoven fabrics made from polyolefins such as polyethylene and polypropylene are preferred for the separator, due to their excellent electrolyte permeability and shutdown effect.

[0341] The thickness of the separator is not particularly limited, but 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 thinner than the above range, the insulating properties and mechanical strength may be reduced. If the separator is thicker than the above range, not only may the battery performance such as rate characteristics be reduced, but also the energy density of the entire electrolyte battery may be reduced.

[0342] On the other hand, inorganic materials include, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate, and these are used in particulate or fibrous form.

[0343] As for the form, a thin film such as a nonwoven fabric, a woven fabric, or a microporous film is used. A thin film with a pore size of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferably used. In addition to the above-mentioned independent thin film, a separator can be used in which a composite porous layer containing the above-mentioned inorganic particles is formed on the surface layer of the positive electrode and / or negative electrode using a resin binder. For example, a porous layer can be formed on both sides of the positive electrode using alumina particles with a 90% particle size of less than 1 μm and a fluororesin as a binder.

[0344] The material of the outer case is not particularly limited as long as it is a substance that is stable against the electrolyte used. Specifically, metals such as nickel-plated steel sheet, stainless steel, aluminum or aluminum alloy, magnesium alloy, or a laminate film of resin and aluminum foil (laminate film) can be used. From the viewpoint of weight reduction, metals such as aluminum or aluminum alloy and laminate film are preferably used.

[0345] Examples of exterior cases using metals include those in which metals are welded together to form a sealed, airtight structure by laser welding, resistance welding, or ultrasonic welding, or those in which the metals are used via a resin gasket to form a crimped structure. Examples of exterior cases using the above-mentioned laminate film include those in which resin layers are heat-sealed to form a sealed, airtight structure. In order to improve sealing properties, a resin different from the resin used in the laminate film may be interposed between the resin layers. In particular, when a sealed structure is formed by heat-sealing the resin layers via a current collecting terminal, a resin having a polar group or a modified resin into which a polar group has been introduced is preferably used as the interposed resin, since the metal and the resin are bonded together.

[0346] The shape of the secondary battery using the above-mentioned electrolyte solution is arbitrary, and examples thereof include cylindrical, prismatic, laminated, coin, large, etc. The shapes and configurations of the positive electrode, negative electrode, and separator can be changed according to the shape of each battery.

[0347] The solid secondary battery is preferably an all-solid-state secondary battery. The solid secondary battery is preferably a lithium-ion battery, and is also preferably a sulfide-based solid secondary battery. The solid secondary battery preferably includes a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode. In the solid secondary battery, the binder of the present disclosure may be used in the electrode layer or the solid electrolyte layer. A solid secondary battery mixture (preferably a mixture sheet) containing the binder and solid electrolyte of the present disclosure, and a solid electrolyte layer (preferably a solid electrolyte layer sheet) containing the binder and solid electrolyte of the present disclosure are also suitable aspects of the present disclosure.

[0348] The solid electrolyte used in the solid secondary battery mixture may be a sulfide-based solid electrolyte or an oxide-based solid electrolyte. In particular, when a sulfide-based solid electrolyte is used, it has the advantage of being flexible.

[0349] The sulfide-based solid electrolyte is not particularly limited, and may be Li ２ S-P ２ S ５ , Li ２ S-P ２ S ３ , Li ２ S-P ２ S ３ -P ２ S ５ , Li ２ S-SiS ２ , LiI-Li ２ S-SiS ２ , LiI-Li ２ S-P ２ S ５ , LiI-Li ２ S-P ２ O ５ , LiI-Li ３ P.O. ４ -P ２ S ５ , LiI-Li ２ S-SiS ２ -P ２ S ５ , Li ２ S-SiS ２ -Li ４ SiO ４ , Li２ S-SiS ２ -Li ３ P.O. ４ , Li ３ P.S. ４ -Li ４ GeS ４ , Li ３．４ P ０．６ Si ０．４ S ４ , Li ３．２５ P ０．２５ Ge ０．７６ S ４ , Li ４－ｘ Ge １－ｘ P ｘ S ４ (x=0.6~0.8), Li ４＋ｙ Ge １－ｙ Ga ｙ S ４ (y=0.2-0.3), LiPSCl, LiCl, Li ７－ｘ－２ｙ P.S. ６－ｘ－ｙ Cl ｘ (0.8≦x≦1.7, 0<y≦-0.25x+0.5), Li １０ SnP ２ S １２ Any one selected from the above, or a mixture of two or more thereof, can be used.

[0350] The sulfide-based solid electrolyte preferably contains lithium. Sulfide-based solid electrolytes containing lithium are used in solid-state batteries that use lithium ions as a carrier, and are particularly preferred in terms of electrochemical devices having high energy density.

[0351] The oxide-based solid electrolyte is preferably a compound that contains oxygen atoms (O), has the ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation properties.

[0352] Specific examples of the compound include Li ｘａ La ｙａ TiO ３ [xa=0.3~0.7, ya=0.3~0.7] (LLT), Li ｘｂ La ｙｂ Zr ｚｂ M ｂｂ ｍｂ Oｎｂ (M ｂｂ is at least one element selected from Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, and Sn, where xb satisfies 5≦xb≦10, yb satisfies 1≦yb≦4, zb satisfies 1≦zb≦4, mb satisfies 0≦mb≦2, and nb satisfies 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, where xc satisfies 0≦xc≦5, yc satisfies 0≦yc≦1, zc satisfies 0≦zc≦1, and nc satisfies 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 between 0 and 0.1, and 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), Li ３ BO ３ -Li ２ SO ４ , Li ２ Alumni ２ O ３ -P ２ O ５ , Li ２ O—SiO ２ , Li ６ BaLa ２ Ta ２ O １２ , Li３ P.O. （４－３／２ｗ） N ｗ (w is w<1), Li having a LISICON (Lithium super ionic conductor) type crystal structure ３．５ Zn ０．２５ GeO ４ , La having a perovskite crystal structure ０．５１ Li ０．３４ TiO ２．９４ , La ０．５５ Li ０．３５ TiO ３ , LiTi having a NASICON (sodium super ionic conductor) type crystal structure ２ P ３ O 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), Li having a garnet-type crystal structure ７ La ３ Zr ２ O １２ Also, ceramic materials in which elements are substituted for LLZ are known. For example, Li ６．２４ La ３ Zr ２ Al ０．２４ O １１．９８ , Li ６．２５ Al ０．２５ La ３ Zr ２ O １２ and Li substituted with Ta ６．６ La ３ Zr １．６ Ta ０．４ O １２ , Nb-substituted Li ６．７５ La ３ Zr １．７５ Nb ０．２５ O １２Other examples include LLZ-based ceramic materials in which 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)) is substituted for LLZ. Phosphorus compounds containing Li, P, and O are also desirable. For example, lithium phosphate (Li ３ P.O. ４ ), LiPON, LiPOD, in which some of the oxygen in lithium phosphate is replaced with nitrogen 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. １ ON (A １ is at least one selected from Si, B, Ge, Al, C, Ga, etc.) can also be preferably used. ２ O-Al ２ O ３ -SiO ２ -P ２ O ５ -TiO ２ -GeO ２ , Li ２ O-Al ２ O ３ -SiO ２ -P ２ O ５ -TiO ２ etc.

[0353] The oxide-based solid electrolyte preferably contains lithium. The oxide-based solid electrolyte containing lithium is used in a solid-state battery that uses lithium ions as a carrier, and is particularly preferred in terms of electrochemical devices having a high energy density.

[0354] The oxide-based solid electrolyte is preferably an oxide having a crystalline structure. Oxides having a crystalline structure are particularly preferred in terms of good Li ion conductivity. Examples of oxides having a crystalline structure include perovskite-type (La ０．５１ Li ０．３４ TiO ２．９４), NASICON type (Li １．３ Al ０．３ Ti １．７ (P.O. ４ ) ３ etc.), garnet type (Li ７ La ３ Zr ２ O １２ (LLZ), etc. Among these, garnet type is preferred.

[0355] The volume-average particle size of the oxide-based solid electrolyte is not particularly limited, but is preferably 0.01 μm or more, and more preferably 0.03 μm or more. The upper limit is preferably 100 μm or less, and more preferably 50 μm or less. The average particle size of oxide-based solid electrolyte particles is measured using the following procedure. Oxide-based solid electrolyte particles are diluted with water (or heptane in the case of substances unstable in water) in a 20 ml sample bottle to prepare a 1 mass % dispersion. The diluted dispersion sample is irradiated with 1 kHz ultrasound for 10 minutes and used for testing immediately thereafter. Using this dispersion sample, data is acquired 50 times at 25°C using a quartz measurement cell using a laser diffraction / scattering particle size distribution analyzer LA-920 (manufactured by HORIBA), to obtain the volume-average particle size. For other detailed conditions, please refer to the description in JIS Z8828:2013, "Particle Size Analysis - Dynamic Light Scattering Method," as necessary. Five samples are prepared for each level, and the average value is used.

[0356] The solid secondary battery may include a separator between the positive electrode and the negative electrode. Examples of the separator include a porous membrane such as polyethylene or polypropylene; a nonwoven fabric made of a resin such as polypropylene; and a nonwoven fabric such as a glass fiber nonwoven fabric.

[0357] The solid 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 above-mentioned positive electrode, negative electrode, solid electrolyte layer, etc., but specific examples include a cylindrical shape, a square shape, a coin shape, and a laminate shape.

[0358] The solid secondary battery can be produced, for example, by stacking a positive electrode, a solid electrolyte layer sheet, and a negative electrode in this order and pressing them together.

[0359] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims.

[0360] The present disclosure will now be described in more detail with reference to examples, but the present disclosure is not limited to these examples.

[0361] Various physical properties were measured by the following methods.

[0362] <Average primary particle diameter> The PTFE aqueous dispersion was diluted with water until the solid content became 0.15% by mass, and the transmittance of the 550 nm projected light per unit length of the diluted latex obtained and the number-based average primary particle diameter determined by measuring the unidirectional diameter by a transmission electron microscope photograph were measured, and a calibration curve was prepared. Using this calibration curve, the average primary particle diameter was determined from the measured transmittance of the 550 nm projected light of each sample.

[0363] <Polymer solid content concentration> 1 g of the aqueous PTFE 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 (1 g) of the aqueous dispersion was expressed as a percentage and used as the solid content concentration.

[0364] <Melt fluidity> According to ASTM D1238, the mass (g / 10 min) of a polymer flowing out of a nozzle with an inner diameter of 2.095 mm and a length of 8 mm per 10 minutes was measured at 372°C and a load of 5 kg using a melt indexer. MFRs of 0.25 g / 10 min or more were considered to have melt fluidity, and those of less than 0.25 g / 10 min were considered not to have melt fluidity.

[0365] <Standard Specific Gravity (SSG)> Using a sample molded in accordance with ASTM D4895 89, the standard specific gravity was measured by the water displacement method in accordance with ASTM D 792.

[0366] <Median diameter (d50)> The median diameter of the PTFE powder was determined by the following laser diffraction method. The measurement was performed in a dry state using a HELOS & RODOS system (trade name, manufactured by SYMPATEC). The powder to be measured was dispersed with compressed air at a dispersion pressure of 2 bar, and the measurement sensor detected the shadow of the powder projected by a laser. The particle size distribution of the powder to be measured was calculated, and the average particle diameter (50% cumulative particle diameter) d50 was determined on a volume basis. d50 was defined as the particle diameter corresponding to 50% of the cumulative particle size distribution.

[0367] <Content of modified monomer> The PPVE content was determined by producing a thin film disk by press-molding a PTFE powder or composition, and measuring the infrared absorbance of the thin film disk by FT-IR, and determining the PPVE content at 995 cm －１ Absorbance at / 935 cm －１ The absorbance ratio was calculated by multiplying the absorbance ratio at 0.14.

[0368] <Specific surface area> A mixed gas of 30% nitrogen and 70% helium was used as the carrier gas, and liquid nitrogen was used for cooling. Measurement was performed by the BET method (flow method, single-point method) based on JIS Z8830. The apparatus used was a Macsorb HM Model-1210.

[0369] <Presence or absence of PTFE particles with a particle diameter of 1 μm or more> The presence or absence of PTFE particles with a particle diameter of 1 μm or more was confirmed by measuring the particle diameter of the PTFE particles through observation using a scanning electron microscope (SEM). The particle diameter was determined by taking an SEM image of the PTFE powder or composition at a magnification of 2000 times and measuring the distance between two horizontal parallel lines that sandwiched a particle.

[0370] <PTFE content including PTFE particles with a particle size of 1 μm or more> Approximately 5 g of PTFE powder was separated into particles obtained by emulsion polymerization and particles obtained by suspension polymerization, and the mass of the particles obtained by emulsion polymerization and the mass of the particles obtained by suspension polymerization were measured, and the PTFE content with a particle size of 1 μm or more was calculated according to the following formula. Samples were taken three times, and after each calculation, the average was calculated and adopted. In addition, according to the above-mentioned particle size measurement method, it was confirmed that the particles obtained by suspension polymerization did not contain PTFE particles with a particle size of less than 1 μm. The distinction between PTFE powder obtained by suspension polymerization and PTFE powder obtained by emulsion polymerization is clear to those skilled in the art. Content (% by mass) of PTFE containing PTFE particles with a particle size of 1 μm or more = (mass (g) of particles obtained by suspension polymerization) / [(mass (g) of particles obtained by suspension polymerization) + (mass (g) of particles obtained by emulsion polymerization)] × 100 The content of PTFE containing PTFE particles with a particle size of 1 μm or more was also measured by SEM observation. In SEM observation, SEM images of the PTFE powder were taken at a magnification of 2000 times, and the content of PTFE containing PTFE particles with a particle size of 1 μm or more was calculated according to the following formula. SEM images were taken five times at different locations, and after calculations were made for each, the average was calculated and this average value was adopted. Content (% by mass) of PTFE containing PTFE particles with a particle size of 1 μm or more = (area (μm) of PTFE particles with a particle size of 1 μm or more) ２ )) / [(area of ​​PTFE particles with a particle diameter of 1 μm or more (μm ２ )) + (area of ​​PTFE particles with a particle diameter of less than 1 μm (μm ２ )) × 100

[0371] <Specific surface area 0.5m ２ / g or more 7.0m ２ The content of PTFE containing PTFE particles having a particle size of 1 μm or more was determined in the same manner as in the case of the content of PTFE containing PTFE particles having a specific surface area of ​​0.5 m / g in each of the Examples and Comparative Examples. ２ / g or more 7.0m ２ The content of PTFE less than 1 μm / g and the content of PTFE obtained by suspension polymerization are equal to the content of PTFE containing PTFE particles having a particle size of 1 μm or more.

[0372] <Endothermic Peak Temperature> The endothermic peak temperature was determined as the temperature corresponding to the minimum point on the heat of fusion curve when a PTFE powder or composition that had not been heated to a temperature of 300° C. or higher was heated at a rate of 10° C. / min using a differential scanning calorimeter (DSC). When there were two or more minimum points, the temperature corresponding to the smallest value was determined as the endothermic peak temperature.

[0373] <Moisture content> Approximately 20 g of PTFE powder or composition was heated at 150°C for 2 hours, and the mass was measured before and after, and the moisture content was calculated according to the following formula. Three samples were taken, and the moisture content was calculated for each sample, and the average moisture content was calculated and used. Moisture content (mass%) = [(mass (g) of PTFE powder or composition before heating) - (mass (g) of PTFE powder or composition after heating)] / (mass (g) of PTFE powder or composition before heating) x 100

[0374] <Content of Perfluoroether Carboxylic Acids A and B> 1 ​​g of PTFE powder or composition was weighed, 10 g (12.6 ml) of methanol was added, and ultrasonic treatment was performed for 60 minutes to obtain an extract. The obtained extract was measured by LC / MS / MS. The fluorine-containing compounds in the extract were measured using a liquid chromatograph mass spectrometer (Waters, LC-MS ACQUITY UPLC / TQD). The measurement equipment configuration and LC-MS measurement conditions are shown in Table 1. Using aqueous solutions of fluorine-containing compounds with known concentrations, aqueous solutions with five or more levels of content were prepared, and LC / MS analysis of the aqueous solutions with each content was performed. The relationship between the content and the area area relative to the content was plotted to draw a calibration curve. Using the calibration curve, the area area of ​​the LC / MS chromatogram of the fluorine-containing compounds in the extract was converted to the content of the fluorine-containing compounds. Note that the lower limit of detection in this measurement method is 10 ppb by mass.

[0375] A white solid A (perfluoroethercarboxylic acid A ammonium salt) was obtained by the method described in Synthesis Example 1 of WO 2021 / 045228.

[0376] The following fluorine-containing surfactants with a molecular weight of 1000 or less were prepared: Perfluoroether carboxylic acid B ammonium salt: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Ammonium perfluoro(2-methyl-3-oxahexanoate), structural formula: CF ３ CF ２ CF ２ OCF (CF ３ ) COONH ４ The following hydrophilic monomer was prepared. Hydrophilic monomer: Ammonium 2,3,3,3-tetrafluoro-2-[(1,1,2-trifluoro-2-propenyl)oxy]-Propanoate, structural formula: CH ２ =CFCF ２ OCF (CF ３ ) COONH ４

[0377] (F106 low water content) Synthesis Example 1 3,480 g of deionized water, 100 g of paraffin wax, and 5.3 g of white solid A were charged into a 6-liter stainless steel autoclave equipped with a stainless steel stirring blade and a temperature-controlling jacket, and the autoclave was heated to 70 ° C. while purging with nitrogen gas to remove oxygen. TFE was injected to adjust the system pressure to 0.78 MPaG, and the system temperature was maintained at 70 ° C. while stirring. Next, an aqueous solution prepared by dissolving 15.0 mg of ammonium persulfate in 20 g of water was injected with TFE to initiate the polymerization reaction. As the polymerization reaction progressed, the system pressure decreased, but TFE was added to maintain the system temperature at 70 ° C. and the system pressure at 0.78 MPaG. When 400 g of TFE had been consumed from the start of polymerization, an aqueous solution prepared by dissolving 18.0 mg of hydroquinone as a radical scavenger in 20 g of water was injected with TFE. Polymerization continues thereafter, and when the polymerization amount of TFE reaches about 1200 g from the start of polymerization, stirring and supply of TFE are stopped, and the gas in the system is immediately released to normal pressure, and polymerization reaction is terminated.The aqueous dispersion is taken out, cooled, and then the paraffin wax is separated, and a PTFE aqueous dispersion is obtained.The average primary particle diameter of the obtained PTFE aqueous dispersion is 310 nm, and the solid content concentration is 25.3 mass%.

[0378] The PTFE aqueous dispersion obtained in Synthesis Example 1 was diluted to a solids concentration of 13% by mass, and the PTFE was coagulated in a container while stirring. The PTFE was then filtered off to obtain a wet PTFE powder. The obtained wet PTFE powder was placed on a stainless steel mesh tray (amount placed: 2.0 g / cm). ２ The mesh tray was then heat-treated in a hot air circulating electric furnace at 180°C. After 20 hours, the mesh tray was removed and air-cooled to obtain PTFE powder 1. The obtained PTFE powder 1 did not exhibit melt flowability. The SSG was 2.156 and the specific surface area was 7.5 m ２ / g, did not contain PTFE particles with a particle size of 1 μm or more, had an endothermic peak temperature of 345° C., had a water content of 0.000 mass %, and had a perfluoroethercarboxylic acid A content of less than 10 mass ppb.

[0379] Production Example 2 Polymerization of tetrafluoroethylene was carried out by the method described in Production Example 3 of International Publication No. 03 / 035724. In the polymerization, perfluoro(propyl vinyl ether) was not used, and 1.0 g of a fluorine-containing surfactant was charged. The obtained PTFE suspension polymerization particles were taken out, washed with pure water, and coarsely pulverized to obtain coarsely pulverized particles. The obtained coarsely pulverized particles were air-dried, and the dried coarsely pulverized particles were pulverized in an air jet mill to obtain PTFE powder 2. The obtained PTFE powder 2 did not exhibit melt flowability. In addition, the SSG was 2.162, the median diameter was 26 μm, and the specific surface area was 3.2 m ２ / g.

[0380] Production Example 3: Tetrafluoroethylene was polymerized by the method described in Production Example 4 of International Publication No. 03 / 035724. No fluorine-containing surfactant was used in the polymerization. The resulting PTFE suspension polymerization particles were removed, washed with pure water, and coarsely pulverized to obtain coarsely pulverized particles. The obtained coarsely pulverized particles were air-dried, and the dried coarsely pulverized particles were pulverized in an air jet mill to obtain PTFE powder 3. The obtained PTFE powder 3 did not exhibit melt flowability. The SSG was 2.154, the median diameter was 49 μm, and the specific surface area was 2.3 m ２ / g.

[0381] Production Example 4 Polymerization of tetrafluoroethylene was carried out by the method described in Production Example 2 of International Publication No. 03 / 035724. In the polymerization, the amount of perfluoro(propyl vinyl ether) charged was 85 g, and no fluorine-containing surfactant was used. The obtained PTFE suspension polymerization particles were taken out, washed with pure water, and coarsely pulverized to obtain coarsely pulverized particles. The obtained coarsely pulverized particles were air-dried, and the dried coarsely pulverized particles were pulverized in an air jet mill to obtain PTFE powder 4. The obtained PTFE powder 4 did not exhibit melt flowability. The SSG was 2.150, the median diameter was 19 μm, the PPVE modification amount was 0.08% by mass, and the specific surface area was 1.9 m ２ / g.

[0382] Synthesis Example 2 A PTFE aqueous dispersion was obtained in the same manner as in Synthesis Example 1, except that 5.3 g of the white solid A was changed to 15.75 g of perfluoroether carboxylic acid B ammonium salt and 35 mg of the hydrophilic monomer. The average primary particle diameter of the obtained PTFE aqueous dispersion was 295 nm, and the solid content concentration was 26.5 mass%.

[0383] Production Example 5: The PTFE aqueous dispersion obtained in Synthesis Example 2 was diluted to a solids concentration of 13% by mass, and the PTFE was coagulated in a container while stirring. The PTFE was then filtered off to obtain a wet PTFE powder. The obtained wet PTFE powder was placed on a flat tray (a tray with no air permeability on the bottom or sides), and the flat tray was heat-treated in a hot air circulating electric furnace at 145°C. After 18 hours, the flat tray was removed and air-cooled to obtain PTFE Powder 5. The obtained PTFE Powder 5 did not exhibit melt flowability. The SSG was 2.159, and the specific surface area was 7.5 m ２ / g and did not contain PTFE particles with a particle size of 1 μm or more.

[0384] Preparation Example 1 The PTFE aqueous dispersion obtained in Synthesis Example 1 and the PTFE powder 2 obtained in Production Example 2 were mixed at a solid content mass ratio (PTFE aqueous dispersion:PTFE powder 2) of 90:10, then diluted to a solid content concentration of 13 mass%, vigorously stirred in a container equipped with a stirrer to solidify, and then filtered to separate the water, thereby obtaining a wet PTFE powder. The obtained wet PTFE powder was placed on a stainless steel mesh tray (placement amount: 2.0 g / cm). ２), and the mesh tray was 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 PTFE composition 1. The obtained PTFE composition 1 contained PTFE particles having a particle size of 1 μm or more. The content of PTFE containing PTFE particles having a particle size of 1 μm or more was 9 mass%, the endothermic peak temperature was 345°C, the water content was 0.000 mass%, and the content of perfluoroethercarboxylic acid A was less than 10 mass ppb.

[0385] Preparation Example 2 PTFE powder 1 obtained in Preparation Example 1 and PTFE powder 3 obtained in Preparation Example 3 were mixed in a mass ratio (PTFE powder 1:PTFE powder 3) of 90:10 to obtain PTFE composition 2. The obtained PTFE composition 2 contained PTFE particles having a particle size of 1 μm or more. The content of PTFE containing PTFE particles having a particle size of 1 μm or more was 10 mass%, the endothermic peak temperature was 345° C., the water content was 0.001 mass%, and the content of perfluoroethercarboxylic acid A was less than 10 ppb by mass.

[0386] Preparation Example 3: PTFE composition 3 was obtained in the same manner as in Preparation Example 2, except that the mass ratio of the PTFE powder was changed to 80:20. The obtained PTFE composition 3 contained PTFE particles having a particle size of 1 μm or more. The content of PTFE containing PTFE particles having a particle size of 1 μm or more was 21 mass%, the endothermic peak temperature was 345° C., the water content was 0.001 mass%, and the content of perfluoroethercarboxylic acid A was less than 10 mass ppb.

[0387] Preparation Example 4: PTFE composition 4 was obtained in the same manner as in Preparation Example 2, except that the mass ratio of the PTFE powder was changed to 60:40. The obtained PTFE composition 4 contained PTFE particles having a particle size of 1 μm or more. The content of PTFE containing PTFE particles having a particle size of 1 μm or more was 42 mass%, the endothermic peak temperature was 345° C., the water content was 0.001 mass%, and the content of perfluoroethercarboxylic acid A was less than 10 mass ppb.

[0388] Preparation Example 5: PTFE composition 5 was obtained in the same manner as in Preparation Example 2, except that the mass ratio of the PTFE powder was changed to 30:70. The obtained PTFE composition 5 contained PTFE particles having a particle size of 1 μm or more. The content of PTFE containing PTFE particles having a particle size of 1 μm or more was 69 mass%, the endothermic peak temperature was 337° C., the water content was 0.000 mass%, and the content of perfluoroethercarboxylic acid A was less than 10 ppb by mass.

[0389] Preparation Example 6: PTFE powder 1 obtained in Preparation Example 1 and PTFE powder 4 obtained in Preparation Example 4 were mixed in a mass ratio (PTFE powder 1:PTFE powder 4) of 90:10 to obtain PTFE composition 6. The obtained PTFE composition 6 contained PTFE particles having a particle size of 1 μm or more. The content of PTFE containing PTFE particles having a particle size of 1 μm or more was 10 mass%, the amount of PPVE modification was 0.01 mass%, the endothermic peak temperature was 345° C., and the water content was 0.001 mass%.

[0390] Preparation Example 7 The wet powder obtained in Preparation Example 1 was placed on a flat tray (a tray with no air permeability on the bottom or sides) and heat-treated in a hot air circulating electric furnace at 180°C. After 5 hours, the flat tray was removed and air-cooled to obtain PTFE Powder 6. The obtained PTFE Powder 6 did not contain PTFE particles with a particle size of 1 μm or more. The endothermic peak temperature was 345°C and the moisture content was 0.126% by mass.

[0391] Preparation Example 8: PTFE powder 5 obtained in Preparation Example 5 and PTFE powder 3 obtained in Preparation Example 3 were mixed in a mass ratio (PTFE powder 5:PTFE powder 3) of 90:10 to obtain PTFE composition 7. The obtained PTFE composition 7 contained PTFE particles having a particle size of 1 μm or more. The content of PTFE containing PTFE particles having a particle size of 1 μm or more was 11 mass%, the endothermic peak temperature was 345° C., the water content was 0.020 mass%, and the content of perfluoroethercarboxylic acid B was 144 mass ppb.

[0392] Each of the PTFE compositions obtained above was evaluated by the following methods.

[0393] Evaluation of Electrolyte-Containing Batteries The following procedures were used to prepare mixture sheets, evaluate the sheets, and evaluate the batteries of Examples 1 to 7 and Comparative Examples 1 and 2. <Preparation of Positive Electrode Mixture Sheets> The active material and conductive additive were weighed, and the materials were placed in a V-type mixer and mixed at 37 rpm for 10 minutes to obtain a mixture of the active material and conductive additive. A weighed binder (PTFE powder or composition) was then added to the mixture and thoroughly cooled in a 5°C thermostatic bath. The mixture of the active material, conductive additive, and binder was placed in a Henschel mixer and homogenized by processing at 1000 rpm for 3 minutes. The mixture was then thoroughly heated in a 100°C thermostatic bath and then processed in a pressure kneader (D1-5: manufactured by Nihon Spindle Co., Ltd.) for 5 minutes (32 rpm, heater 50°C, pressure 0.5 MPa) to promote fibrillation and obtain a cohesive bulk electrode mixture. Then, the bulk electrode mixture was put into a Henschel mixer for re-pulverization and processed at 300 rpm for 1 minute to obtain an electrode mixture. The electrode mixture was put into parallel metal rolls (temperature: 80 ° C, rotation speed: 1 m / min) and rolled to obtain an electrode mixture sheet. The obtained rolled sheet was again roughly crushed by folding it in two, and the electrode mixture was put into a metal roll (temperature: 80 ° C, rotation speed: 1 m / min) and rolled to obtain a stronger electrode mixture sheet. Then, the electrode mixture sheet was put into a roll press and the gap was adjusted. The final thickness of the positive electrode mixture layer was adjusted to 90 μm. Table 2 shows the material types and compositions.

[0394] Denka Li-400: Carbon black manufactured by Denka Co., Ltd.

[0395] <Evaluation of powder cohesion> 10 g of the electrode mixture before being poured into the parallel-arranged metal rolls was sieved for 30 seconds using a sieve with 0.18 mm openings (JIS-Z8801), and the mass percentage of the aggregates remaining on the mesh was measured (rounded down to the nearest whole number). The results are shown in Table 3. Electrode mixtures with fewer aggregates have good sheet formability and uniformity.

[0396] <Measurement of strength of positive electrode mixture sheet> The positive electrode mixture sheet was cut out to prepare a 4 mm wide strip-shaped test piece. A tensile tester (AGS-100NX manufactured by Shimadzu Corporation) was used to measure at a speed of 100 mm / min. The distance between chucks was 30 mm. Displacement was applied until breakage, and the maximum stress measured was taken as the strength of each sample. Tests were performed with N=8, and the average value was calculated. Comparison was made with Comparative Example 1 set to 100%. The coefficient of variation was calculated to evaluate the variation. The results are shown in Table 3.

[0397] <Flexibility evaluation of positive electrode mixture sheet (bending test)> The prepared electrode mixture sheet was cut into a width of 4 cm and a length of 10 cm to prepare test pieces. Next, these test pieces were wrapped around a Φ2 mm round rod, and then the test pieces were visually inspected to confirm the presence or absence of damage such as scratches or cracks. The absence of damage was evaluated as ○, and the presence of damage was evaluated as ×. The results are shown in Table 3.

[0398] <Preparation of Positive Electrode> The above positive electrode mixture sheet was bonded to 20 μm aluminum foil as follows. A slurry prepared by dissolving polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) and dispersing carbon black at an 80:20 ratio was used as the adhesive. The above adhesive was applied to the aluminum foil and dried on a hot plate at 120°C for 15 minutes to form a current collector with an adhesive layer. The positive electrode mixture sheet was then placed on the current collector with the adhesive layer, and the positive electrode mixture sheet and current collector were bonded together using a roll press heated to 100°C. The sheet was then cut to the desired size and tabbed to form a positive electrode.

[0399] <Preparation of Negative Electrode> 98 parts by mass of a carbonaceous material (graphite) was mixed with 1 part by mass of an aqueous dispersion of sodium carboxymethyl cellulose (concentration of sodium carboxymethyl cellulose: 1% by mass) and 1 part by mass of an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber: 50% by mass) as a thickener and binder, and the mixture was mixed in a disperser to form a slurry. The resulting slurry was applied to a copper foil with a thickness of 10 μm, dried, rolled in a press, cut to the desired size, and tabbed to form a negative electrode.

[0400] <Preparation of Electrolyte Solution> As an organic solvent, a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) (EC:EMC:DMC = 30:30:40 (volume ratio)) was weighed into a sample bottle, and 1% by mass each of fluoroethylene carbonate (FEC) and vinylene carbonate (VC) was dissolved therein to prepare a mixed solution. LiPF was added to this mixed solution so that the concentration in the electrolyte solution was 1.1 mol / L. ６ The salts were mixed at 23° C. to obtain a non-aqueous electrolyte solution.

[0401] <Preparation of Aluminum Laminate Cell> The above-mentioned positive electrode was placed opposite to the negative electrode via a 20 μm-thick microporous polyethylene film (separator), and the nonaqueous electrolyte solution obtained above was poured into the cell. After the nonaqueous electrolyte solution had sufficiently permeated the separator and the like, the cell was sealed, pre-charged, and aged to prepare a lithium ion secondary battery.

[0402] <Evaluation of Storage Characteristics (Remaining Capacity Rate, Gas Generation Amount)> The lithium ion secondary battery manufactured as described above was charged at 25°C with a constant current and constant voltage (hereinafter referred to as CC / CV charging) (0.1C cut) to 4.3 V at a current equivalent to 0.33 C, and then discharged to 3 V at a constant current of 0.33 C. This constituted one cycle, and the initial discharge capacity was calculated from the discharge capacity of the third cycle. After the evaluation of the initial discharge capacity was completed, the battery was again charged at 25°C with CC / CV charging (0.1C cut) to 4.3 V, and the battery volume was calculated by Archimedes' method. After calculating the battery volume, the battery was stored at a high temperature for 30 days at 60°C. After the high-temperature storage, the battery was sufficiently cooled and then the volume of the battery was calculated at 25°C. The amount of gas generated was calculated from the difference in volume between the battery before and after the storage test. The amount of gas generated was compared, with the amount of gas generated in Comparative Example 1 set to 100. After determining the amount of gas generated, the battery was discharged at 0.33 C to 3 V at 25°C to determine the remaining capacity. The ratio of the remaining capacity after high-temperature storage to the initial discharge capacity was determined, and this was taken as the remaining capacity rate (%). The average of N = 5 was taken. (Remaining capacity) / (Initial discharge capacity) × 100 = remaining capacity rate (%) The results are shown in Table 3.

[0403]

[0404] Evaluation of Solid Electrolyte Mixture Sheets The mixture sheets of Examples 8 to 14 and Comparative Examples 3 and 4 were prepared and evaluated according to the following procedures. The preparation and evaluation were carried out in an argon atmosphere.

[0405] <Preparation of solid electrolyte mixture sheet> The weighed binder (PTFE powder or composition) was thoroughly cooled in a thermostatic bath at 5 ° C., then placed in a Henschel mixer and pulverized at 800 rpm for 10 minutes. The pulverized binder and solid electrolyte were each weighed and thoroughly cooled in a thermostatic bath at 5 ° C. The mixture was placed in a Henschel mixer and homogenized at 300 rpm for 1 minute. The mixture was then sufficiently heated in a thermostatic bath at 40 ° C., and then treated in a Henschel mixer at 1000 rpm for 1 minute to promote fibrillation, thereby obtaining an electrolyte mixture. The electrode mixture was placed between metal rolls (temperature: 80 ° C., rotation speed: 1 m / min) arranged in parallel and rolled to obtain an electrolyte mixture sheet. The obtained rolled sheet was again folded in half to be crushed, and the electrolyte mixture was placed in a metal roll (temperature: 80°C, rotation speed: 1 m / min) and rolled to obtain a stronger electrolyte mixture sheet. The electrolyte mixture sheet was then placed in a roll press and the gap was adjusted. The final thickness of the electrolyte mixture sheet was adjusted to 120 μm. Table 4 shows the material types and compositions.

[0406]

[0407] <Strength Measurement of Solid Electrolyte Mixture Sheet (Tensile Test)> The solid electrolyte mixture sheet was cut out to prepare a 4 mm wide strip-shaped test piece. A tensile tester (AGS-100NX manufactured by Shimadzu Corporation) was used to measure at a rate of 100 mm / min. The distance between chucks was 30 mm. Displacement was applied until fracture, and the maximum stress measured was taken as the strength of each sample. The test was performed with N=8, and the following results were obtained: Good: 0.1 N / mm ２ or more ×: 0.1N / mm ２ The results are shown in Table 5.

[0408] <Flexibility Evaluation of Solid Electrolyte Mixture Sheet (Bending Test)> The prepared solid electrolyte mixture sheet was cut into a width of 4 cm and a length of 10 cm to prepare test pieces. Next, these test pieces were wrapped around a Φ10 mm round rod, and the test pieces were visually inspected to confirm the presence or absence of damage such as scratches or cracks. If no damage was observed, a test was performed using a thinner Φ5 mm round rod to confirm damage. Again, if no damage was observed, a test was performed using a thinner Φ2 mm round rod to confirm damage. The results were classified as A to D. A: No damage with Φ2 mm rod B: Damage with Φ2 mm rod C: Damage with Φ5 mm rod D: Damage with Φ10 mm rod The results are shown in Table 5.

[0409] <Ionic Conductivity of Solid Electrolyte Mixture Sheet> The solid electrolyte mixture sheet was cut to an appropriate size, and gold was vapor-deposited on both sides. The solid electrolyte mixture sheet was then punched into a circle with a diameter of 10 mm using a punch, and placed in a pressure cell. The cell screws were tightened with 8 N, and electrodes were attached to the top and bottom of the cell. A schematic cross-sectional view of the pressure cell used is shown in Figure 1. This sample was measured using an impedance device manufactured by Toyo Corporation at 25°C, AC amplitude modulation of 10 mV, and a frequency of 5 x 10 ６ The ionic conductivity was measured at a frequency of 0.1 Hz or less, and the results are shown in Table 5.

[0410]

[0411] 1: Screw 2: Nut 3: Insulation sheet 4: Solid electrolyte mixture sheet 5: Gold vapor deposition 6: Upper electrode 7: Lower electrode

Claims

1. A polytetrafluoroethylene composition used as a binder for electrochemical devices, comprising polytetrafluoroethylene containing polytetrafluoroethylene particles having a particle diameter of 1 μm or more.

2. A polytetrafluoroethylene composition according to claim 1, wherein the content of polytetrafluoroethylene including polytetrafluoroethylene particles having a particle size of 1 μm or more is 1% by mass or more and 70% by mass or less relative to the polytetrafluoroethylene composition.

3. A binder for electrochemical devices, comprising essentially a polytetrafluoroethylene composition, said polytetrafluoroethylene composition comprising polytetrafluoroethylene particles having a particle diameter of 1 μm or more.

4. The binder for electrochemical devices according to claim 3, wherein the polytetrafluoroethylene containing the polytetrafluoroethylene particles having a particle size of 1 μm or more is polytetrafluoroethylene that does not exhibit melt flowability.

5. A binder for electrochemical devices according to claim 3 or 4, wherein the content of polytetrafluoroethylene including polytetrafluoroethylene particles having a particle diameter of 1 μm or more is 1% by mass or more and 70% by mass or less relative to the polytetrafluoroethylene composition.

6. A binder for electrochemical devices according to any one of claims 3 to 5, wherein the content of polytetrafluoroethylene including polytetrafluoroethylene particles having a particle diameter of 1 μm or more is 1% by mass or more and 50% by mass or less relative to the polytetrafluoroethylene composition.

7. A polytetrafluoroethylene composition used as a binder for electrochemical devices, having a specific surface area of ​​0.5 m ２ / g or more 7.0m ２ / g polytetrafluoroethylene.

8. Specific surface area 1.5m ２ / g or more 3.5m ２ 8. The polytetrafluoroethylene composition of claim 7, comprising no more than 1 / g of polytetrafluoroethylene.

9. A binder for electrochemical devices consisting essentially of a polytetrafluoroethylene composition, the polytetrafluoroethylene composition having a specific surface area of ​​0.5 m ２ / g or more 7.0m ２ 13. A binder for an electrochemical device comprising polytetrafluoroethylene having a molecular weight of less than 1.0 μm / g.

10. The specific surface area of ​​0.5 m ２ / g or more 7.0m ２ 10. The binder for electrochemical devices according to claim 9, wherein the polytetrafluoroethylene having a molecular weight of less than 1000 / g is polytetrafluoroethylene that does not exhibit melt flowability.

11. The polytetrafluoroethylene composition is subjected to a process for determining the specific surface area of ​​0.5 m ２ / g or more 7.0m ２ 11. The binder for electrochemical devices according to claim 9 or 10, wherein the content of polytetrafluoroethylene is less than 1 mass % and less than 70 mass %.

12. The polytetrafluoroethylene composition is subjected to a process for producing a sample having a specific surface area of ​​0.5 m ２ / g or more 7.0m ２ 12. The binder for electrochemical devices according to claim 9, wherein the polytetrafluoroethylene content is less than 1 mass % and less than 50 mass %.

13. The polytetrafluoroethylene composition has a specific surface area of ​​1.5 m ２ / g or more 3.5m ２ The binder for electrochemical devices according to any one of claims 9 to 12, comprising polytetrafluoroethylene in an amount of 0.1 to 1.0 g / g or less.

14. A polytetrafluoroethylene composition used as a binder for an electrochemical device, comprising polytetrafluoroethylene obtained by suspension polymerization.

15. A binder for electrochemical devices consisting essentially of a polytetrafluoroethylene composition, said polytetrafluoroethylene composition containing polytetrafluoroethylene obtained by suspension polymerization.

16. The binder for electrochemical devices according to claim 15, wherein the polytetrafluoroethylene obtained by the suspension polymerization is polytetrafluoroethylene that does not exhibit melt flowability.

17. The binder for electrochemical devices according to claim 15 or 16, wherein the content of the polytetrafluoroethylene obtained by the suspension polymerization is 1% by mass or more and 70% by mass or less relative to the polytetrafluoroethylene composition.

18. A binder for electrochemical devices according to any one of claims 15 to 17, wherein the content of the polytetrafluoroethylene obtained by the suspension polymerization is 1% by mass or more and 50% by mass or less relative to the polytetrafluoroethylene composition.

19. The binder for electrochemical devices according to any one of claims 3 to 6, 9 to 13, and 15 to 18, wherein the polytetrafluoroethylene composition has an endothermic peak temperature of 333°C or higher.

20. The binder for electrochemical devices according to any one of claims 3 to 6, 9 to 13, and 15 to 19, wherein the polytetrafluoroethylene composition is in the form of a powder.

21. The binder for electrochemical devices according to any one of claims 3 to 6, 9 to 13, and 15 to 20, wherein the polytetrafluoroethylene composition is substantially free of moisture.

22. The binder for electrochemical devices according to any one of claims 3 to 6, 9 to 13, and 15 to 21, wherein the polytetrafluoroethylene composition is substantially free of fluorine-containing compounds having a molecular weight of 1,000 or less.

23. An electrode mixture comprising the polytetrafluoroethylene composition according to claim 1, 2, 7, 8 or 14, or the binder for electrochemical devices according to any one of claims 3 to 6, 9 to 13, 15 to 22, and an electrode active material.

24. The electrode mixture according to claim 23, which is in the form of a sheet.

25. An electrode comprising the polytetrafluoroethylene composition according to claim 1, 2, 7, 8 or 14, or the binder for electrochemical devices according to any one of claims 3 to 6, 9 to 13, 15 to 22, an electrode active material, and a current collector.

26. A secondary battery comprising the electrode according to claim 25.

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