Insulation member for electrochemical device

Abstract

This invention provides an insulation member for an electrochemical device, capable of maintaining insulation properties even at a high temperature. This insulation member for an electrochemical device includes a polytetrafluoroethylene composition containing polytetrafluoroethylene which is a homopolymer of tetrafluoroethylene or modified polytetrafluoroethylene containing a tetrafluoroethylene unit and 1.0 mass% or less of a modified monomer unit.

Description

Insulating materials for electrochemical devices

[0001] The present disclosure relates to an insulating member for an electrochemical device.

[0002] It is known that resins such as perfluoroalkoxyalkane (PFA) are used as insulating members or sealing members for electrochemical devices such as lithium ion secondary batteries (see, for example, Patent Documents 1 to 3).

[0003] JP 2017-174732 A International Publication No. 2020 / 066050 International Publication No. 2014 / 049645

[0004] An object of the present disclosure is to provide an insulating member for an electrochemical device that can maintain its insulating properties even at high temperatures.

[0005] The present disclosure (1) is an insulating member for an electrochemical device, comprising a polytetrafluoroethylene composition containing polytetrafluoroethylene, which is a homopolymer of tetrafluoroethylene or a modified polytetrafluoroethylene containing tetrafluoroethylene units and 1.0 mass% or less of modified monomer units.

[0006] The present disclosure (2) is the insulating member according to the present disclosure (1), wherein the polytetrafluoroethylene composition has a heat of crystallization of 50 J / g or less.

[0007] The present disclosure (3) is the insulating member according to the present disclosure (1) or (2), wherein the polytetrafluoroethylene composition exhibits non-melt moldability.

[0008] The present disclosure (4) is an insulating member in any combination with any of the present disclosures (1) to (3), in which the polytetrafluoroethylene is the modified polytetrafluoroethylene.

[0009] The present disclosure (5) is an insulating member in any combination with any of the present disclosures (1) to (4), in which the modified monomer is perfluoro(propyl vinyl ether).

[0010] The present disclosure (6) is an insulating member in any combination with any of the present disclosures (1) to (5), wherein the electrochemical device comprises a non-aqueous electrolyte.

[0011] The present disclosure (7) is an insulating member that can be arbitrarily combined with any of the present disclosures (1) to (6) that are gaskets.

[0012] The present disclosure (8) is an insulating member in any combination with any of the present disclosures (1) to (7), in which the content of modified monomer units in the modified polytetrafluoroethylene is 0.20 mass% or less relative to all polymerized units.

[0013] The present disclosure (9) is the insulating member according to the present disclosure (8), wherein the content of the polytetrafluoroethylene is 99.0 mass% or more relative to the polytetrafluoroethylene composition, and the content of the polytetrafluoroethylene composition is 99.0 mass% or more relative to the insulating member.

[0014] The present disclosure (10) is the insulating member according to the present disclosure (9), having a melt flow rate of less than 0.10 g / 10 min.

[0015] The present disclosure (11) is an insulating member for an electrochemical device that exhibits non-melt formability.

[0016] The present disclosure (12) is the insulating member according to the present disclosure (11), which has a melt flow rate of less than 0.10 g / 10 min and contains polytetrafluoroethylene.

[0017] The present disclosure (13) is an insulating member in any combination with any of the present disclosures (1) to (12), wherein the electrochemical device is a lithium ion battery or a sodium ion battery.

[0018] The present disclosure (14) is an insulating member of any combination with any of the present disclosures (1) to (13) having a heat of fusion of 50 J / g or more.

[0019] According to the present disclosure, it is possible to provide an insulating member for an electrochemical device that can maintain its insulating properties even at high temperatures.

[0020] FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a portion of an electrochemical device including an insulating member (gasket). FIG. 2 is a schematic cross-sectional view showing an example of the configuration of a portion of an electrochemical device including an insulating member (gasket). FIG. 3 is a schematic cross-sectional view showing an example of the configuration of a portion of an electrochemical device including an insulating member (gasket). FIG. 4 is a diagram schematically showing a procedure for fabricating a test assembly used for insulation resistance measurement. FIG. 5 is a diagram schematically showing a procedure for fabricating a test assembly used for insulation resistance measurement. FIG. 6 is a schematic view of a test assembly used for insulation resistance measurement. FIG. 7 is a diagram schematically showing one step of insulation resistance measurement. FIG. 8 is a schematic view of a permeation test jig used for a water vapor permeation test.

[0021] The present disclosure will be specifically described below.

[0022] The present disclosure provides an insulating member for electrochemical devices (hereinafter also referred to as insulating member (1) of the present disclosure) containing a PTFE composition containing PTFE, which is a homopolymer of tetrafluoroethylene (TFE) or a modified polytetrafluoroethylene (PTFE) containing TFE units and 1.0 mass% or less of modified monomer units.

[0023] In this specification, unless otherwise specified, the insulating member (1) of the present disclosure and the insulating member (2) of the present disclosure described below will be collectively referred to as the "insulating member of the present disclosure."

[0024] The insulating member (1) of the present disclosure contains a specific PTFE composition, which allows it to maintain its insulating properties even at high temperatures. In electrochemical devices requiring high output, such as lithium-ion power batteries, a large number of cells are generally connected in parallel or series in close proximity. In such a configuration, even if a nearby cell catches fire or the temperature of the cell becomes abnormally high (e.g., 400°C or higher), the insulating member (1) of the present disclosure can maintain good insulating properties and prevent short circuits between cells and cell components.

[0025] The PTFE in the insulating member (1) of the present disclosure is a homopolymer of TFE or a modified PTFE. The modified PTFE is preferred because it has better insulating properties at high temperatures and also has low water vapor permeability.

[0026] The modified PTFE contains TFE units and 1.0% by mass or less of modified monomer units. The amount of TFE units may be 99.0% by mass or more. Alternatively, the modified PTFE may consist solely of TFE units and modified monomer units.

[0027] In order to further improve the insulating properties at high temperatures and the low water vapor permeability of the modified PTFE, the content of the modified monomer unit is preferably in the range of 0.00001 to 1.0 mass% relative to the total polymerized units. The lower limit of the content of the modified monomer unit is more preferably 0.0001 mass%, even more preferably 0.001 mass%, even more preferably 0.005 mass%, and particularly preferably 0.010 mass%. The upper limit of the content of the modified monomer unit is preferably 0.90 mass%, more preferably 0.80 mass%, more preferably 0.50 mass%, even more preferably 0.40 mass%, even more preferably 0.30 mass%, even more preferably 0.20 mass%, and particularly preferably 0.10 mass%. In this specification, the modified monomer unit refers to a part of the molecular structure of PTFE that is derived from the modified monomer.

[0028] 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.

[0029] 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.

[0030] 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 １represents a perfluoroorganic group. ) and perfluorounsaturated compounds represented by the following formula (I) are included. 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.

[0031] 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.

[0032] 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.

[0033] The perfluorovinyl ether further includes a compound represented by the general formula (A) in which Rf １ is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, Rf １ is of the following formula:

[0034]

[0035] (wherein m represents 0 or an integer of 1 to 4), Rf １ is of the following formula:

[0036]

[0037] (wherein n represents an integer of 1 to 4).

[0038] The (perfluoroalkyl)ethylene [PFAE] is not particularly limited, and examples thereof include (perfluorobutyl)ethylene [PFBE] and (perfluorohexyl)ethylene.

[0039] Hydrogen-containing fluoroolefins include CH ２ =CF ２ , CFH=CH ２ , CFH=CF２ , C.H. ２ =CFCF ３ , C.H. ２ = CHCF ３ , CHF=CHCF ３ (E form), CHF=CHCF ３ (Z-isomer), etc.

[0040] 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.

[0041] The above Rf ２ is 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 CF３ is more preferred.

[0042] As the modified monomer, from the viewpoint of further improving insulating properties at high temperatures and low water vapor permeability, at least one selected from the group consisting of PAVE, PFAE, HFP, and CTFE is preferred, at least one selected from the group consisting of PAVE and HFP is more preferred, PAVE is even more preferred, and perfluoro(propyl vinyl ether) [PPVE] is even more preferred.

[0043] 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.

[0044] The PTFE may be the PTFE obtained by emulsion polymerization or the PTFE obtained by suspension polymerization.From the viewpoint of improving low water vapor permeability, the PTFE obtained by emulsion polymerization is preferable, and the unsintered PTFE (having no history of being heated to a temperature above the melting point) obtained by emulsion polymerization is more preferable.

[0045] In order to further improve the insulating properties at high temperatures, the PTFE composition preferably has an endothermic peak temperature of 333°C or higher, more preferably 335°C or higher, even more preferably 337°C or higher, even more preferably 340°C or higher, and preferably 350°C or lower, 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, each of them is taken as the endothermic peak temperature.

[0046] In order to further improve insulating properties at high temperatures, the PTFE composition preferably has a melting point of 315° C. or higher, more preferably 320° C. or higher, even more preferably 323° C. or higher, and even more preferably 325° C. or higher, and preferably 335° C. or lower, and more preferably 330° C. or lower. The melting point is the temperature corresponding to the minimum point in the heat of fusion curve obtained by performing differential scanning calorimetry (DSC) on a PTFE composition that has a history of being heated to a temperature of 300° C. or higher at a heating rate of 10° C. / min.

[0047] The PTFE composition may be a PTFE composition that has not been completely sintered. A PTFE composition that has not been completely sintered has a large heat of fusion and may take a long time to completely melt, so there is an advantage in that the temperature rise during heat generation can be delayed, and it is possible to prevent the temperature from reaching an abnormally high temperature in a short time.

[0048] The heat of fusion of the PTFE composition is preferably 27 J / g or more, more preferably 30 J / g or more, even more preferably 33 J / g or more, particularly preferably 60 J / g or more, and may be 90 J / g or less, or may be 80 J / g or less, in that the temperature rise can be delayed when the PTFE composition generates heat, and the temperature rise can be prevented from reaching an abnormally high temperature in a short time. The heat of fusion of the PTFE composition is a value measured by using a differential scanning calorimeter (DSC).

[0049] In order to further improve the insulating property at high temperature, the heat of crystallization of the PTFE composition is preferably 50 J / g or less, more preferably 40 J / g or less, even more preferably 30 J / g or less, and even more preferably 25 J / g or less, and may be 10 J / g or more, or may be 15 J / g or more.The heat of crystallization is the value measured by using a differential scanning calorimeter (DSC).

[0050] The thermal decomposition temperature of the PTFE composition is preferably 400° C. or higher, more preferably 430° C. or higher, and even more preferably 450° C. or higher, in order to further improve insulating properties at high temperatures. It may also be 600° C. or lower, 550° C. or lower, or 520° C. or lower. The thermal decomposition temperature is the temperature at which the mass loss rate of a sample reaches 1% by mass when measured in an air atmosphere at a heating rate of 10° C. / min using a thermogravimetric and differential thermal analyzer (STA7200 manufactured by Hitachi High-Tech Science Corporation).

[0051] The PTFE composition has a melt viscosity of 1.0×10 at 380° C., which further improves insulating properties at high temperatures. ７ It is preferable that the viscosity is 1.0×10 Pa·s or more. ８ It is more preferable that the viscosity is 1.0×10 Pa·s or more. １１ Pa s or less, and may be 5.0 × 10 １０ The melt viscosity may be quantified using a melt viscoelasticity measuring device MCR302 (manufactured by Anton Paar Japan Co., Ltd.). The melt viscosity is determined by measuring the complex viscosity using a parallel plate measuring jig having a diameter of 7 mm under conditions of a deformation rate of 0.3%, a sample thickness of 0.5 mm, a temperature of 380°C, and a frequency of 0.01 radians per second.

[0052] In order to further improve insulating properties at high temperatures, the PTFE composition preferably has a standard specific gravity (SSG) of 2.200 or less, more preferably 2.190 or less, even more preferably 2.180 or less, and even more preferably 2.175 or less, and may also be 2.130 or more, 2.140 or more, or 2.150 or more. The SSG is measured by the water displacement method in accordance with ASTM D 792 using a sample molded in accordance with ASTM D 4895 89.

[0053] The PTFE composition preferably has non-melt-fabricability, which 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, the PTFE composition does not easily flow even in the melting temperature range.

[0054] The PTFE composition preferably exhibits non-melt-formability, which will be described later.

[0055] The PTFE composition may be a sintered PTFE composition or an unsintered PTFE composition. It may also be a PTFE composition that has been heated to a temperature above its melting point, or a PTFE composition that has not been heated to a temperature above its melting point. A PTFE composition that has not been heated to a temperature above its melting point has the property of being easily stretchable and soft when processed into a raw tape. Therefore, when wrapped around a part, it easily conforms to the shape of the part, and can be easily attached to parts with simple shapes as well as parts with complex shapes, providing insulation to the surrounding area of ​​the part.

[0056] The PTFE composition may contain components other than the PTFE, but preferably consists essentially of the PTFE. This allows the effects of the PTFE to be significantly exhibited. "Consisting essentially of the PTFE" means that the PTFE content is 70% by mass or more relative to the PTFE composition. The PTFE content is preferably 90.0% by mass or more, more preferably 95.0% by mass or more, even more preferably 99.0% by mass or more, particularly preferably 99.9% by mass or more, and most preferably 99.95% by mass or more relative to the PTFE composition. It is also preferable that the PTFE composition consists essentially of the PTFE.

[0057] The PTFE composition may contain a filler or the like. The filler is preferably an insulating filler, and is not preferably a conductive filler. Examples of the filler include known insulating fillers such as aluminum oxide, silicon oxide, magnesium oxide, anhydrous magnesium carbonate, magnesium hydroxide, silicon oxide, silicon nitride, boron nitride, and aluminum nitride, with magnesium oxide, aluminum nitride, and boron nitride being preferred.

[0058] The insulating member (1) of the present disclosure may contain components other than the PTFE composition, but preferably 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 70% by mass or more relative to the insulating member. The content of the PTFE composition is preferably 90.0% by mass or more relative to the insulating member, more preferably 95.0% by mass or more, even more preferably 99.0% 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 insulating member (1) of the present disclosure consists essentially of the PTFE composition.

[0059] The insulating member (1) of the present disclosure preferably exhibits non-melt formability, which will be described later.

[0060] The insulating member (1) of the present disclosure can be produced by molding a raw material composition containing raw material PTFE into a desired shape. The form of the raw material composition is not limited and may be a powder, a dispersion liquid, or the like, but is preferably a powder.

[0061] The raw material PTFE can be produced by emulsion polymerization or suspension polymerization.

[0062] 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 monomers (TFE and optionally modified monomers) necessary for forming the above-mentioned PTFE is carried out in aqueous medium, thereby obtaining the aqueous dispersion liquid containing the above-mentioned PTFE particles (primary particles).In the above-mentioned emulsion polymerization, if necessary, chain transfer agent, buffer, pH adjuster, stabilizing aid, dispersion stabilizer, radical scavenger etc. can be used.

[0063] The resulting aqueous dispersion is coagulated to obtain a wet powder, which is then dried to obtain a powder of raw PTFE. Coagulation and drying can be carried out by known methods.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] After the suspension polymerized particles are pulverized, the pulverized particles obtained may be classified by a known method such as air classification.

[0068] The resulting pulverized particles may be granulated by a known granulation method.

[0069] The physical properties of the resulting PTFE can be adjusted by adjusting the conditions of polymerization and post-treatment. For example, in emulsion polymerization, the endothermic peak temperature can be increased, the standard specific gravity can be lowered, and the melt viscosity can be increased by reducing the amount of polymerization initiator used, reducing the amount of chain transfer agent used, or using a radical scavenger. In post-treatment of emulsion polymerization, the decomposition temperature can be increased by setting the drying temperature to 150°C or higher. In suspension polymerization, the endothermic peak temperature can be increased, the standard specific gravity can be lowered, and the melt viscosity can be increased by reducing the amount of polymerization initiator used, reducing the amount of chain transfer agent used, or preferably not using it at all. In post-treatment, the decomposition temperature can be increased by performing washing or setting the drying temperature to 150°C or higher.

[0070] The method for molding the raw material composition is not particularly limited, and any known molding method can be used.

[0071] When using a powder obtained by emulsion polymerization, for example, the powder of the raw material composition and an extrusion aid can be mixed and paste extrusion molded. The extrusion aid can be removed by drying. It is also preferable to compress the powder of the raw material composition. A dispersion of the raw material composition may be applied to a substrate such as glass cloth and dried. If necessary, firing may be performed.

[0072] When using the powder obtained by suspension polymerization, molding methods such as compression molding, ram extrusion molding, and isostatic pressing can be used. If necessary, firing can be performed. The PTFE molded body can be processed by mechanical processing such as cutting to produce a molded body having a desired shape. For example, a PTFE sheet can be obtained by cutting the PTFE molded body.

[0073] The present disclosure also provides an insulating member for electrochemical devices that exhibits non-melt formability (hereinafter also referred to as insulating member (2) of the present disclosure).

[0074] The insulating member (2) of the present disclosure exhibits non-melt moldability, thereby maintaining its insulating properties even at high temperatures. The insulating member (2) of the present disclosure can maintain good insulating properties even when the cells of an electrochemical device reach abnormally high temperatures (e.g., 400°C or higher), thereby preventing short circuits in the cells and between cell components.

[0075] As used herein, "non-melt-processable" means that the melt flow rate (MFR) is less than 0.10 g / 10 min, preferably less than 0.01 g / 10 min. The MFR is determined in accordance with 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 5000 g (total load) per 10 min.

[0076] The insulating member (2) of the present disclosure may contain a resin exhibiting non-melt formability (hereinafter also referred to as non-melt formable resin), a filler, etc. The non-melt formable resin may be a fluororesin or a non-fluororesin.

[0077] The non-melt-moldable resin has almost no fluidity at high temperatures, and therefore has a thermal decomposition temperature of preferably 480°C or higher, more preferably 485°C or higher, even more preferably 490°C or higher, even more preferably 492°C or higher, and particularly preferably 495°C or higher, in order to further improve insulation. It may also be 600°C or lower, 550°C or lower, or 520°C or lower. The thermal decomposition temperature is the temperature at which the mass loss rate of the sample reaches 1% by mass when measured in an air atmosphere at a heating rate of 10°C / min using a thermogravimetric and differential thermal analyzer (STA7200 manufactured by Hitachi High-Tech Science Corporation).

[0078] The non-melt-moldable resin is also preferably crosslinked.

[0079] Examples of the non-melt-moldable resin include PTFE, ultra-high molecular weight polyethylene, thermosetting resin, cross-linked resin, etc., and among these, PTFE, ultra-high molecular weight polyethylene, phenol resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, silicone resin, polyurethane, thermosetting polyimide, and cross-linked polyethylene are preferred, and PTFE and ultra-high molecular weight polyethylene are more preferred.

[0080] The PTFE may be the same as the PTFE in the insulating member (1) of the present disclosure.

[0081] The ultra-high molecular weight polyethylene has a weight average molecular weight of 1.0 × 10 ６ It is preferable that the ratio is 2.0×10 or more. ６ More preferably, it is 7.0 × 10 or more. ７ or less, 7.0 × 10 ６ The molecular weight of the ultra-high molecular weight polyethylene is measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0082] Examples of commonly available ultra-high molecular weight polyethylene include Tiber UHMW-PE manufactured by Mitsubishi Chemical Advanced Materials Corporation and Hi-Zex Million manufactured by Mitsui Chemicals, Inc.

[0083] The filler is preferably an insulating filler, and is not preferably a conductive filler. Examples of the filler include known insulating fillers such as aluminum oxide, silicon oxide, magnesium oxide, anhydrous magnesium carbonate, magnesium hydroxide, silicon oxide, silicon nitride, boron nitride, and aluminum nitride, with magnesium oxide, aluminum nitride, and boron nitride being preferred.

[0084] The insulating member (2) of the present disclosure may contain components other than the non-melt-formable resin, but preferably consists essentially of the non-melt-formable resin. This allows the effects of the non-melt-formable resin to be significantly exhibited. "Consisting essentially of the non-melt-formable resin" means that the content of the non-melt-formable resin is 70% by mass or more relative to the insulating member. The content of the non-melt-formable resin is preferably 90.0% by mass or more relative to the insulating member, more preferably 95.0% by mass or more, even more preferably 99.0% 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 insulating member (2) of the present disclosure consists essentially of the non-melt-formable resin.

[0085] The insulating member (2) of the present disclosure can be produced by molding a raw material composition containing a raw material resin into a desired shape. The form of the raw material composition is not limited and may be a powder, a dispersion, or the like, but powder is preferred. The molding method is also not limited, and in addition to the molding methods exemplified for the insulating member (1) of the present disclosure, known molding methods can be used.

[0086] The insulating member of the present disclosure is a member used to provide electrical insulation in an electrochemical device. The insulating member of the present disclosure may provide insulation between two or more conductive members of an electrochemical device, for example, between a positive electrode and a negative electrode, or between an electrode and another member (for example, an exterior such as a lid).

[0087] In order to further improve insulating properties at high temperatures, the insulating member of the present disclosure preferably has an endothermic peak temperature of 333°C or higher, more preferably 335°C or higher, even more preferably 337°C or higher, and even more preferably 340°C or higher, and preferably 350°C or lower, and more preferably 346°C or lower. The endothermic peak temperature is a temperature corresponding to a minimum point in a heat of fusion curve obtained by performing differential scanning calorimetry (DSC) at a heating rate of 10°C / min on an insulating member 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, each of these minimum points is defined as an endothermic peak temperature.

[0088] In order to further improve insulating properties at high temperatures, the insulating member of the present disclosure preferably has a melting point of 315° C. or higher, more preferably 320° C. or higher, even more preferably 323° C. or higher, and even more preferably 325° C. or higher, and preferably 335° C. or lower, and more preferably 330° C. or lower. The melting point 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 an insulating member that has a history of being heated to a temperature of 300° C. or higher.

[0089] The insulating member of the present disclosure has a heat of fusion of preferably 27 J / g or more, more preferably 30 J / g or more, even more preferably 33 J / g or more, even more preferably 50 J / g or more, particularly preferably 60 J / g or more, and may also be 90 J / g or less, or may be 80 J / g or less, in order to delay the temperature rise during heat generation and prevent the insulating member from reaching an abnormally high temperature in a short time. The heat of fusion is a value measured using a differential scanning calorimeter (DSC).

[0090] In order to further improve insulating properties at high temperatures, the insulating member of the present disclosure preferably has a heat of crystallization of 50 J / g or less, more preferably 40 J / g or less, even more preferably 30 J / g or less, and even more preferably 25 J / g or less, and may be 10 J / g or more, or may be 15 J / g or more. The heat of crystallization is a value measured using a differential scanning calorimeter (DSC).

[0091] The insulating member of the present disclosure preferably has a thermal decomposition temperature of 400°C or higher, more preferably 430°C or higher, and even more preferably 450°C or higher, in order to further improve insulating properties at high temperatures. The thermal decomposition temperature may be 600°C or lower, 550°C or lower, or 520°C or lower. The thermal decomposition temperature is the temperature at which the mass loss rate of a sample reaches 1% by mass when measured in an air atmosphere at a heating rate of 10°C / min using a thermogravimetric and differential thermal analyzer (STA7200 manufactured by Hitachi High-Tech Science Corporation).

[0092] The insulating member of the present disclosure has a melt viscosity of 1.0×10 at 380° C., which further improves insulating properties at high temperatures. ７ It is preferable that the viscosity is 1.0×10 Pa·s or more. ８ It is more preferable that the viscosity is 1.0×10 Pa·s or more. １１ Pa s or less, and may be 5.0 × 10 １０ The melt viscosity may be quantified using a melt viscoelasticity measuring device MCR302 (manufactured by Anton Paar Japan Co., Ltd.). The melt viscosity is determined by measuring the complex viscosity using a parallel plate measuring jig having a diameter of 7 mm under conditions of a deformation rate of 0.3%, a sample thickness of 0.5 mm, a temperature of 380°C, and a frequency of 0.01 radians per second.

[0093] In order to further improve insulating properties at high temperatures, the insulating member of the present disclosure preferably has a standard specific gravity (SSG) of 2.200 or less, more preferably 2.190 or less, even more preferably 2.180 or less, and even more preferably 2.175 or less, and may be 2.130 or more, 2.140 or more, or 2.150 or more. The SSG is measured by the water displacement method in accordance with ASTM D 792 using a sample molded in accordance with ASTM D 4895 89.

[0094] The insulating member 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 insulating member does not easily flow even in the melting temperature range.

[0095] In order to further improve insulating properties at high temperatures, the insulating member of the present disclosure preferably has an insulation resistance of 1 MΩ or more, more preferably 10 MΩ or more, and even more preferably 100 MΩ or more after heating at 450° C. The insulation resistance is measured by the method described in the examples below.

[0096] The insulating member of the present disclosure has good sealing properties even at high temperatures, and therefore can be suitably used as a sealing member. A sealing member is a member used to prevent leakage of liquid or gas or intrusion of liquid or gas from the outside. Examples of the sealing member include gaskets and packings, and among these, gaskets (insulating gaskets) are preferred.

[0097] The shape of the insulating member of the present disclosure is not particularly limited and may be, for example, an annular shape. Furthermore, the insulating member of the present disclosure may have a circular, oval, rectangular shape with rounded corners, or the like in a plan view, and may have a through hole in the center.

[0098] The insulating member of the present disclosure may have a cylindrical portion and a flange portion extending radially from one opening of the cylindrical portion. An insulating member having such a structure can be suitably used, for example, to insulate an external terminal having a terminal head and a shaft portion. In this embodiment, when the shaft portion of the external terminal is arranged to face the interior of the electrochemical device (e.g., when it faces the same direction as the external terminal 2 in FIGS. 1 and 2 described below), the insulating member of the present disclosure is preferably arranged so that the opening of the cylindrical portion opposite the flange portion faces the interior of the electrochemical device. When the shaft portion of the external terminal is arranged to face the exterior of the electrochemical device (when it is upside down from the external terminal 2 in FIGS. 1 and 2 ), the insulating member of the present disclosure is preferably arranged so that the opening of the cylindrical portion opposite the flange portion faces the exterior of the electrochemical device.

[0099] A mode of use of an insulating member according to an embodiment of the present disclosure will be described with reference to the drawings.

[0100] 1, an electrochemical device 10 (e.g., a sealed prismatic secondary battery) includes an outer can (not shown) and a lid 1. An electric element (not shown), such as a power generator, is housed inside the outer can, and the opening of the outer can is hermetically sealed with the lid 1. An external terminal 2 (positive electrode terminal or negative electrode terminal) is provided on the lid 1, and externally generated electric power is supplied to the electric element via the external terminal 2 for storage, and also for supplying electric power to an external load.

[0101] To electrically insulate the external terminals 2 from the lid 1, an insulating member (gasket) 3 and an insulating plate 4 are provided on the lid 1. The insulating member 3 corresponds to the insulating member of the present disclosure. The external terminals 2 have a terminal head 21 having a rectangular block shape and a cylindrical shank 22. The shank 22 protrudes from the bottom surface of the terminal head 21 (toward the interior of the electrochemical device).

[0102] As shown in FIG. 1 , the insulating member 3 has a cylindrical portion 31 , a flange portion 32 that extends radially from one opening of the cylindrical portion 31 , and a side wall portion 33 that rises from the periphery of the flange portion 32 .

[0103] The cylindrical portion 31 is fitted onto the shaft portion 22 of the external terminal 2, and the inner peripheral surface of the cylindrical portion 31 abuts against the outer peripheral surface of the shaft portion 22. The cylindrical portion 31 is also inserted into the through hole of the lid 1, and the outer peripheral surface of the cylindrical portion 31 abuts against the inner peripheral surface of the through hole of the lid 1.

[0104] The flange portion 32 is sandwiched between the lid 1 and the external terminal 2 , with one contact surface of the flange portion 32 contacting the lower surface of the external terminal 2 and the other contact surface of the flange portion 32 contacting the surface of the lid 1 .

[0105] With the cylindrical portion 31 and flange portion 32 of the insulating member 3 compressed, the insulating member 3 comes into contact with the external terminal 2 and the lid 1, thereby ensuring the hermeticity of the electrochemical device.

[0106] The insulating member of the present disclosure can be used alone or in combination with other members. The insulating member of the present disclosure may be laminated with other members. The other members may be insulating members or sealing members.

[0107] The other members preferably include a material different from the insulating member of the present disclosure, for example, a non-fluorine resin such as polyethylene (PE), polypropylene (PP), or polybutylene terephthalate (PBT), or a fluorine resin other than PTFE such as tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer (PFA).

[0108] Specific examples of the insulating member of the present disclosure used in combination with other members are shown in FIGS. 2 and 3.

[0109] In Figure 2, the insulating member (gasket) 3 includes a member 3a containing PTFE to ensure insulation at high temperatures, and a member 3b containing another material (e.g., PP) to ensure sealing under normal conditions, not high temperatures. Members 3a and 3b may be in contact with each other, or may be adjacent but not in contact. An adjacent state refers to a state in which the members are not in contact but are within a distance of 3 mm. The same effect can be achieved by swapping the materials and functions of members 3a and 3b.

[0110] In FIG. 3 , the insulating member (gasket) 3 has a laminated structure consisting of a member 3c containing PTFE and ensuring insulation at high temperatures, and a member 3d containing another material (e.g., PP) and ensuring insulation under normal conditions, not high temperatures. Members 3c and 3d may be partially overlapping. A partially overlapping state refers to a portion of the members 3c and 3d that does not overlap due to reasons such as non-overlapping edges, different widths or depths, misalignment, or the presence of holes or gaps. Making member 3c smaller than member 3d can reduce material costs. Making member 3c larger than member 3d can improve insulation at high temperatures. Member 3c may also have holes or gaps. In this case, material costs can be reduced. Having no holes or gaps improves insulation at high temperatures. Member 3c may also be divided into multiple components. This may facilitate assembly.

[0111] Examples of methods for achieving a structure in which the insulating member of the present disclosure and another member are laminated include the following: (I) A molded article is produced in which the insulating member of the present disclosure and another member are pre-laminated, and this is then attached to an electrochemical device. (II) The insulating member of the present disclosure and the other member are laminated as separate members by attaching and fixing them to an electrochemical device. (III) A portion of the surface of the other member is coated with a material (such as PTFE) for forming the insulating member of the present disclosure, and then the member is attached to an electrochemical device.

[0112] Specific examples of the coating method in (III) above include the following methods: (i) Applying a dispersion (e.g., PTFE dispersion) containing the material for the insulating member of the present disclosure to the surface of another member. This may then be dried. It may also be fired afterwards. (ii) Winding a sintered tape (e.g., sintered PTFE tape) containing the material for the insulating member of the present disclosure to the surface of another member. (iii) Winding a tape that has not been completely sintered or has not been sintered at all (e.g., PTFE tape that has not been completely sintered or has not been sintered at all) containing the material for the insulating member of the present disclosure to the surface of another member. (iv) Attaching a tape that has not been completely sintered or has not been sintered at all (e.g., PTFE tape that has not been completely sintered or has not been sintered at all) containing the material for the insulating member of the present disclosure to the surface of another member. Attachment may be via an adhesive or glue.

[0113] The insulating member of the present disclosure is used in electrochemical devices such as batteries and capacitors. Examples of the battery include secondary batteries such as lithium ion batteries and sodium ion batteries. A sodium ion secondary battery is a secondary battery in which sodium ions in an electrolyte solution are responsible for electrical conduction. For example, sodium metal oxide can be used as the active material of the positive electrode. Examples of salts in the electrolyte include NaPF ６ , NaBF ４ , NaClO ４ and NaAsF ６ inorganic sodium salts such as; and NaCF ３ SO ３ , NaPF ３ (C ２ F ５ ) ３ , NaN(CF ３ SO ２ ) ２ , NaN(C ２ F ５ SO ２ ) ２ , NaC(CF ３ SO ２ ) ３ , NaN(FSO ２ ) ２Examples of the material for the negative electrode include organic sodium salts such as those mentioned above. Hard carbon can be used as the negative electrode material. The capacitor is not particularly limited, but is preferably an electrochemical capacitor. Examples of the electrochemical capacitor include an electric double layer capacitor, a hybrid capacitor, and a redox capacitor. Examples of the hybrid capacitor include a sodium ion capacitor, a lithium ion capacitor, and a magnesium ion capacitor. Of these, an electric double layer capacitor is particularly preferred.

[0114] The insulating member of the present disclosure can be suitably used as an insulating member for batteries, and can be particularly suitably used as an insulating member for secondary batteries such as lithium ion batteries and sodium ion batteries.

[0115] The secondary battery may be a secondary battery using an electrolytic solution or a solid-state secondary battery. In this specification, the solid-state secondary battery may be a secondary battery containing a solid electrolyte, and may be a semi-solid-state secondary battery containing a solid electrolyte and a liquid component as the electrolyte, or an all-solid-state secondary battery containing only a solid electrolyte as the electrolyte.

[0116] The insulating member of the present disclosure can be used in contact with an electrolyte included in an electrochemical device, i.e., it can have a contact surface with the electrolyte. Even when used in such a state, the insulating member of the present disclosure can maintain excellent insulating properties at high temperatures. The electrolyte here includes not only the electrolyte itself but also substances derived from the electrolyte, and may be liquid, solid, or gas. The gas includes, for example, volatilized electrolytic solution and gas generated by decomposition of the electrolytic solution during charging and discharging.

[0117] The electrochemical device according to the present disclosure preferably includes a nonaqueous electrolyte. The insulating member according to the present disclosure may be used in contact with the nonaqueous electrolyte included in the electrochemical device, i.e., may have a liquid-contact surface with the nonaqueous electrolyte included in the electrochemical device.

[0118] The non-aqueous electrolyte may be prepared by dissolving a known electrolyte salt in a known organic solvent for dissolving electrolyte salts.

[0119] 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.

[0120] 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 , LiCl, LiBr, CH ３ SO ３ Li, CF ３ SO ３ Li, cesium carbonate, etc. are listed, and LiPF is particularly preferred due to its good 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.

[0121] 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 is usually 1.5 mol / L, although it depends on the organic solvent used to dissolve the electrolyte salt.

[0122] The solid electrolyte used in the solid secondary battery may be a sulfide-based solid electrolyte or an oxide-based solid electrolyte. In particular, when a sulfide-based solid electrolyte is used, there is an advantage in that the flexibility of the sheet is improved.

[0123] The company's portfolio of households in the fields of self-sufficiency ２ 3-0 ２ ﳳ ５ 、i ２ 3-0 ２ ﳳ ３ 、i ２ 3-0 ２ ﳳ ３ -P ２ ﳳ ５ 、i ２ 3-3iｳ ２ 、iILi ２ 3-3iｳ ２ 、iILi ２ 3-0 ２ ﳳ ５ 、iILi ２ 3-0 ２ 9 ５ 、iILi ３ PO ４ -P ２ ﳳ ５ 、iILi ２ 3-3iｳ ２ -P ２ ﳳ ５ 、i ２ 3-3iｳ ２ -i ４ 3iｯ ４ 、i ２ 3-3iｳ ２ -i ３ PO ４ 、i ３ PS ４ -i ４ 11e3 ４ 、i ３．４ P ０．６ ｳi ０．４ ﳳ ４ 、i ３．２５ P ０．２５ Ge ０．７６ ﳳ ４ 、i ４－ｘ Ge １－ｘ P ｘ ﳳ ４ (x=00.6~0.8)、ｬi ４＋ｙ Ge １－ｙ Ga ｙ ﳳ ４ (1000000003) ７－ｘ－２ｙ PS ６－ｘ－ｙ 3lｘ (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.

[0124] 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.

[0125] 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.

[0126] 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 O ｎｂ (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 , Li ３ 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 O１２ (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 １２ Other 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.

[0127] 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.

[0128] 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 etc.), 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.

[0129] 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.

[0130] The present disclosure will now be described in more detail with reference to examples, but the present disclosure is not limited to these examples.

[0131] Various physical properties were measured by the following methods.

[0132] <Content of modified monomer> The PPVE content in PTFE was determined by press-molding a sample into a thin film disk, 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 PPVE content in the PFA was measured using an NMR analyzer (for example, AVANCE300 high temperature probe manufactured by Bruker Biospin).

[0133] <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.

[0134] <Heat of fusion> The obtained sheet was cut, and approximately 3 mg was weighed and placed in a dedicated aluminum pan. Using an X-DSC7000 (manufactured by Hitachi High-Tech Science Corporation), the temperature was raised to the melting peak temperature +40°C at a rate of 10°C / min under a nitrogen atmosphere, and the heat of fusion was measured. The heat of fusion was determined by drawing a line from the melting peak temperature -40°C to the melting peak temperature +20°C on the obtained DSC chart, and measuring the area enclosed by the curve including the peak.

[0135] <Heat of crystallization> The obtained sheet was cut, and approximately 3 mg was weighed and placed in a dedicated aluminum pan. Using an X-DSC7000 (Hitachi High-Tech Science Corporation), the temperature was raised to the crystallization peak temperature +40 ° C at a rate of 10 ° C / min under a nitrogen atmosphere, held for 1 minute, and then lowered to the crystallization peak temperature -60 ° C at a rate of 10 ° C / min to measure the heat of crystallization at the crystallization point. The value of the heat of crystallization was determined by drawing a line from the crystallization peak temperature -30 ° C to +25 ° C on the obtained DSC chart, and determining the area enclosed by the curve including the peak.

[0136] <Melt Viscosity> Quantification was performed using a melt viscoelasticity measuring device MCR302 (manufactured by Anton Paar Japan Co., Ltd.). A parallel plate with a diameter of 7 mm was used as the measuring jig, and the complex viscosity measured at a deformation rate of 0.3%, a sample thickness of 0.5 mm, a temperature of 380°C, and a frequency of 0.01 radians per second was taken as the melt viscosity. If the viscosity is too low or if the sample polymer gasifies due to thermal decomposition, the viscosity is set to 100 Pa s or less.

[0137] <Melt moldability (MFR)> According to ASTM D1238, 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 per 10 minutes was measured using a melt indexer at 372°C and a load of 5000 g (total load). MFR of 0.10 g / 10 min or more was deemed to be melt moldable, while MFR of less than 0.10 g / 10 min was deemed to be non-melt moldable. Note that MFR of less than 0.10 g / 10 min was deemed to be too low to measure due to low fluidity. If the fluidity is too high or the polymer of the sample gasifies due to thermal decomposition, the MFR is deemed to be 100 g / 10 min or more.

[0138] <Insulation resistance> Using the obtained sheet, as shown in FIG. 4(a), a test piece 11 (a = 3.5 mm, b = 0.2 mm, c = d = 30 mm in FIG. 4(a)) having a φ3.5 mm hole in the center of a square sheet of 30 mm × 30 mm × thickness 0.2 mm was produced. As shown in FIG. 4(b), the test piece 11 and a washer 12 (e = 6.5 mm, f = 18 mm, g = 1 mm in FIG. 4(b)) were overlapped and fixed so that the centers of the holes in the test piece 11 and the washer 12 were aligned. As shown in FIG. 5(a), the hole in the test piece 11 was enlarged with a taper punch 13 (h = 1 mm, i = 8 mm, j = 40 mm in FIG. 5(a)), and a cylindrical sleeve portion whose outer peripheral surface abutted against the inner peripheral surface of the hole in the washer 12 was formed. As shown in FIG. 5( b), the shank of a pin 14 (k = 6 mm, l = 12 mm, m = 6 mm, n = 8 mm in FIG. 5( b)) having a disk-shaped base and a cylindrical shank was inserted into the sleeve, obtaining a test assembly 100 shown in FIG. 6. As shown in FIG. 7( a), a tubular jig 101 was placed over the washer 12 of the test assembly 100, and the test assembly 100 was placed in an electric furnace with a 5 kg load applied via the tubular jig 101 in the direction of the arrow shown in FIG. 7( b). The test assembly 100 was heated to an initial temperature of 250°C in the electric furnace, and then heated to a holding temperature of 450°C at a heating rate of 10°C / min. The heat treatment was performed at the holding temperature for 10 minutes, and then cooled to room temperature. After cooling, the load was removed, and the resistance between the washer 12 and the pin 14 was measured using an insulation measuring device (Digital Megaohm Tester 3454, manufactured by Hioki E.E. Corporation) at an applied voltage of 250 V. If the insulation resistance exceeded 100 MΩ, it was determined that there was insulation after heating at 450°C, and if it was less than 10 Ω, it was determined that there was no insulation after heating at 450°C. Insulation was also evaluated in the same manner when the holding temperature was 350°C. If the insulation resistance exceeded 100 MΩ, it was determined that there was insulation after heating at 350°C, and if it was less than 10 Ω, it was determined that there was no insulation after heating at 350°C.

[0139] <Water Vapor Permeation Test> As shown in FIG. 8, 2 g of water 42 was placed in an aluminum alloy cup 41. A gasket 47 was inserted between the cup 41 and a gasket compression jig 43, and the lid 44 was tightened with bolts 45 to compress the gasket 47. A spacer 46 was placed between the lid 44 and the cup 41, and the compression rate of the gasket 47 was adjusted to 37.5% or 58%. The compression rate was calculated using the following formula: (Gasket compression rate (%)) = {1 - (Distance between the cup 41 and the gasket compression jig 43 (gasket placement portion)) / (Height of the gasket before compression)} × 100. The mass of the permeation test jig 40 obtained in this manner was measured. The permeation test jig 40 was placed in an electric furnace at 80°C, left for 1000 hours, removed, and left at room temperature for 2 hours, after which the mass was measured. The water vapor permeation coefficient was calculated using the following formula. This operation was repeated three times, and the average water vapor permeation coefficient was calculated. The average values ​​are shown in Table 2. Water vapor permeability coefficient (g / 1000 hr) = (mass of permeation test jig before heating) - (mass of permeation test jig after heating)

[0140] Example 1: PTFE powder (TFE homopolymer obtained by suspension polymerization, SSG = 2.159) was compression-molded under a pressure of 30 MPa and held for 5 minutes. The temperature was raised to 365°C at a rate of 50°C / min in an electric furnace, and heat-treated at 365°C for 5.5 hours. The molded product was then cooled to room temperature to obtain a φ50 mm molded body. The resulting molded body was machined to obtain a 0.2 mm thick PTFE sheet A. PTFE sheet A exhibited non-melt moldability. Various physical properties were measured using the PTFE sheet A using the methods described above. The results are shown in Table 1. From the resulting φ50 mm molded body, a circular gasket A with a square cross section measuring 14.3 mm inner diameter, 17.7 mm outer diameter, and 1.6 mm height was obtained. Gasket A exhibited non-melt processability. A water vapor permeation test was conducted using gasket A to measure the water vapor permeability coefficient. The results are shown in Table 2.

[0141] Example 2: PTFE powder (TFE homopolymer obtained by emulsion polymerization, SSG = 2.172) was mixed with a lubricant (trade name: Isopar G (registered trademark), manufactured by Exxon Corporation). The mixture was paste-extruded using a sheet-shaped extrusion die and heat-treated at 230°C for 30 minutes to remove the lubricant, yielding a 0.2 mm-thick PTFE sheet B. PTFE sheet B exhibited non-melt moldability. Various physical properties were measured using the PTFE sheet B using the methods described above. The results are shown in Table 1. Similarly, the PTFE powder was mixed with a lubricant, and the mixture was paste-extruded using an RR100 die according to ASTM D4895 and heat-treated at 30°C for 30 minutes to remove the lubricant, yielding a PTFE round bar E with a diameter of approximately 2.5 mm. The PTFE round bar exhibited non-melt moldability. The PTFE round bar was bent into a circle to form a gasket with an inner diameter of 16 mm, with 3 mm of the strand ends overlapping to form a gasket, to obtain Gasket B. Gasket B exhibited non-melt processability. A water vapor permeation test was conducted using Gasket B to measure the water vapor permeation coefficient. The results are shown in Table 2.

[0142] Example 3 A 0.2 mm thick PTFE sheet C was obtained in the same manner as in Example 1, except that PTFE powder (PPVE-modified PTFE obtained by suspension polymerization (TFE / PPVE=99.89 / 0.11% by mass), SSG=2.175) was used instead of the PTFE powder in Example 1. PTFE sheet C exhibited non-melt moldability. Various physical properties of PTFE sheet C were measured by the methods described above. The results are shown in Table 1.

[0143] Comparative Example 1 PFA pellets (TFE / PPVE = 96.1 / 3.9 mass%, MFR = 15.3 g / 10 min) were melted at 370 ° C for 20 minutes using a hot plate press, and then water-cooled while being pressed at a pressure of 1 MPa to obtain a PFA sheet with a thickness of 0.2 mm. The PFA sheet exhibited melt moldability. Various physical properties were measured using the PFA sheet using the methods described above. The results are shown in Table 1.

[0144] Comparative Example 2 A 0.2 mm thick PTFE sheet D was obtained in the same manner as in Comparative Example 1, except that PTFE powder (TFE homopolymer, MFR = 22 g / 10 min) was used instead of the PFA pellets in Comparative Example 1. PTFE sheet D exhibited melt moldability. Various physical properties were measured using PTFE sheet D by the methods described above. The results are shown in Table 1.

[0145] Comparative Example 3 A 0.2 mm thick PP sheet was prepared in the same manner as in Comparative Example 1, except that polypropylene (PP) (product name: Prime Polypro F227, manufactured by Prime Polymer Co., Ltd.) was used instead of the PFA pellets used in Comparative Example 1, and the hot plate press temperature was 280°C instead of 370°C. Various physical properties were measured using the PP sheet using the methods described above. The results are shown in Table 1. Similarly, PP was heated above its melting point to prepare a sheet, and from this sheet, a circular gasket C with a rectangular cross section measuring an inner diameter of 14.3 mm, an outer diameter of 17.7 mm, and a height of 1.6 mm was obtained. A water vapor permeation test was conducted using gasket C, and the water vapor permeation coefficient was measured. The results are shown in Table 2.

[0146] Comparative Example 4 A 0.2 mm thick PBT sheet was prepared in the same manner as in Comparative Example 1, except that polybutylene terephthalate (PBT) (product name: PBT Natural Color Unfilled, manufactured by Kureha Extron Co., Ltd.) was used instead of the PFA pellets used in Comparative Example 1, and the hot plate press temperature was 280°C instead of 370°C. Various physical properties were measured using the PBT sheet using the methods described above. The results are shown in Table 1. Similarly, PBT was heated above its melting point to prepare a sheet, and from this sheet, a circular gasket D with a rectangular cross section measuring an inner diameter φ14.3 mm, an outer diameter φ17.7 mm, and a height of 1.6 mm was obtained. A water vapor permeation test was conducted using gasket D, and the water vapor permeation coefficient was measured. The results are shown in Table 2.

[0147]

[0148] The PTFE sheets (PTFE compositions) produced in the examples were suitable for use as insulating members for electrochemical devices.

[0149] 10: Electrochemical device 1: Lid 2: External terminal 21: Terminal head 22: Shaft 3: Insulating member (gasket) 31: Cylindrical portion 32: Flange portion 33: Side wall portion 4: Insulating plate 11: Test piece 12: Washer 13: Taper punch 14: Pin 100: Test assembly 101: Tubular jig 40: Permeation test jig 41: Cup 42: Water 43: Gasket compression jig 44: Lid 45: Bolt 46: Spacer 47: Gasket

Claims

1. An insulating member for electrochemical devices comprising a polytetrafluoroethylene composition containing polytetrafluoroethylene, which is a homopolymer of tetrafluoroethylene or a modified polytetrafluoroethylene containing tetrafluoroethylene units and 1.0 mass % or less of modified monomer units.

2. The insulating member according to claim 1, wherein the heat of crystallization of said polytetrafluoroethylene composition is 50 J / g or less.

3. An insulating member according to claim 1 or 2, wherein said polytetrafluoroethylene composition exhibits non-melt moldability.

4. An insulating member according to any one of claims 1 to 3, wherein the polytetrafluoroethylene is a modified polytetrafluoroethylene.

5. An insulating member according to any one of claims 1 to 4, wherein the modified monomer is perfluoro(propyl vinyl ether).

6. The insulating member according to any one of claims 1 to 5, wherein the electrochemical device comprises a non-aqueous electrolyte.

7. The insulating member according to any one of claims 1 to 6, which is a gasket.

8. An insulating material according to any one of claims 1 to 7, wherein the content of modified monomer units in the modified polytetrafluoroethylene is 0.20 mass % or less based on the total polymerized units.

9. An insulating member according to claim 8, wherein the content of said polytetrafluoroethylene is 99.0 mass% or more relative to said polytetrafluoroethylene composition, and the content of said polytetrafluoroethylene composition is 99.0 mass% or more relative to the insulating member.

10. The insulating member according to claim 9, having a melt flow rate of less than 0.10 g / 10 min.

11. Insulating materials for electrochemical devices that exhibit non-melt formability.

12. The insulating member according to claim 11, comprising polytetrafluoroethylene, the melt flow rate of which is less than 0.10 g / 10 min.

13. The insulating member according to any one of claims 1 to 12, wherein the electrochemical device is a lithium ion battery or a sodium ion battery.

14. The insulating material according to any one of claims 1 to 13, which has a heat of fusion of 50 J / g or more.

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