Separator for electrochemical element, member for electrochemical element, and electrochemical element

Abstract

To provide a separator for an electrochemical element which can attain a high ionic permeability and a low moisture content at the same time.SOLUTION: The separator for an electrochemical element according to the present disclosure has a porous layer containing at least two different types of nitrogen-containing aromatic resins and a filler in the range of at least 0 wt.% and less than 20 wt.%.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a separator for an electrochemical element, a member for an electrochemical element, and an electrochemical element.

Background Art

[0002] Electrochemical elements, such as non-aqueous electrolyte secondary batteries, particularly lithium-ion secondary batteries, are widely used as batteries for personal computers, mobile phones, portable information terminals, in-vehicle applications, etc., because of their high energy density.

[0003] As a member of the non-aqueous electrolyte secondary battery, the development of a separator with excellent heat resistance has been underway. For example, as described in Patent Document 1, a separator in which a heat-resistant layer containing an aramid resin and inorganic particles is laminated on a porous substrate is known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inorganic particles (fillers) as described in Patent Document 1 can be used as pore-forming materials for making the heat-resistant layer porous to ensure ion permeability. However, the conventional technology as described above has room for improvement from the viewpoint of reducing the amount of moisture mixed into the heat-resistant layer. From the viewpoint of suppressing gas generation in the battery, it is preferable to reduce the amount of moisture mixed into the heat-resistant layer.

[0006] One aspect of the present invention aims to realize a separator for an electrochemical element that achieves both high ion permeability and low moisture content.

Means for Solving the Problems

[0007] As a result of intensive studies by the inventors to solve the above problems, it has been found that by using two or more nitrogen-containing aromatic resins and controlling the filler content to be 0 wt% or more and less than 20 wt%, a separator for an electrochemical element having both high ion permeability and low water content can be realized.

[0008] A separator for an electrochemical element according to one aspect of the present invention includes a porous layer containing two or more nitrogen-containing aromatic resins and having a filler content of 0 wt% or more and less than 20 wt%.

Advantages of the Invention

[0009] According to one aspect of the present invention, a separator for an electrochemical element having both high ion permeability and low water content can be provided.

Modes for Carrying Out the Invention

[0010] An embodiment of the present invention will be described below, but the present invention is not limited thereto. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more and B or less".

[0011] 〔1. Separator for Electrochemical Element〕 A separator for an electrochemical element according to an embodiment of the present invention includes a porous layer containing two or more nitrogen-containing aromatic resins and having a filler content of 0 wt% or more and less than 20 wt%. Hereinafter, the separator for an electrochemical element will also be simply referred to as a "separator".

[0012] The filler can be used to make the porous layer porous to ensure ion permeability. If the filler is not used, it is difficult to form pores, so the air permeability increases and the ion permeability tends to decrease. However, if a large amount of filler, for example, alumina filler, is used, the amount of water mixed into the porous layer also tends to increase. In addition, using a large amount of alumina filler also leads to an increase in cost.

[0013] Therefore, as a result of intensive research by the present inventors, it has been found that by using two or more nitrogen-containing aromatic resins, high ion permeability can be achieved without using a filler or even when reducing the filler content compared to the prior art. Although it is speculative, the following mechanism is considered. When there is a difference in the ease of dissolution (precipitability) of two or more nitrogen-containing aromatic resins, in the process of precipitation, the resin that is difficult to dissolve (the first resin) precipitates first, while the resin that is easy to dissolve (the second resin) precipitates later. The second resin precipitates in the vicinity of the first resin that has precipitated earlier due to the compatibility relationship between the first resin and the solvent. By precipitating with the resin unevenly distributed in this way, it is considered that sufficient pore formation can be achieved without using a filler or even when reducing the filler content compared to the prior art.

[0014] In one embodiment of the present invention, the porous layer can be disposed between a polyolefin porous substrate and at least one of a positive electrode and a negative electrode as a member constituting an electrochemical element. Hereinafter, the polyolefin porous substrate may also be simply referred to as the "porous substrate". The porous layer may be disposed between the porous substrate and at least one of the positive electrode and the negative electrode so as to be in contact with them. The porous layer disposed between the porous substrate and at least one of the positive electrode and the negative electrode may be one layer or two or more layers. The porous layer is preferably an insulating layer.

[0015] The nitrogen-containing aromatic resin means an aromatic resin containing a nitrogen atom. The aromatic resin means a resin containing at least a structural unit having an aromatic group.

[0016] Examples of the nitrogen-containing aromatic resin include aromatic polyamides such as wholly aromatic polyamides (aramid resins) and semi-aromatic polyamides, aromatic polyimides, aromatic polyamideimides, polybenzimidazoles, aromatic polyurethanes, and melamine resins. Among them, the nitrogen-containing aromatic resin preferably contains an aramid resin.

[0017] Examples of the aramid resin include para-aramid and meta-aramid, with para-aramid being preferred. Examples of para-aramid include para-oriented or para-oriented-like structured para-aramids such as poly(p-phenylene terephthalamide), poly(p-benzamide), poly(4,4'-benzylanilide terephthalamide), poly(p-phenylene-4,4'-biphenylene dicarboxamide), poly(p-phenylene-2,6-naphthalenedicarboxamide), poly(2-chloro-p-phenylene terephthalamide), p-phenylene terephthalamide / 2,6-dichlorop-phenylene terephthalamide copolymer, poly(4,4'-diphenylsulfonyl terephthalamide), and p-phenylene terephthalamide / 4,4'-diphenylsulfonyl terephthalamide copolymer. Examples of meta-aramid include poly(m-phenylene terephthalamide), poly(m-phenylene isophthalamide), poly(m-benzamide), poly(m-phenylene-4,4'-biphenylene dicarboxamide), and poly(m-phenylene-2,6-naphthalenedicarboxamide). Poly(m-phenylene isophthalamide) is also referred to as poly[N,N'-(1,3-phenylene)isophthalamide].

[0018] As for two or more nitrogen-containing aromatic resins, it is preferable to include resins with different precipitation properties as described above. For example, it is preferable to combine resins with different structures, such as a resin having a rigid structure and a resin having flexibility. For example, poly(p-phenylene terephthalamide), poly(2-chloro-p-phenylene terephthalamide), poly(p-benzamide), and poly(4,4'-benzylanilide terephthalamide) have a rigid structure. On the other hand, poly(4,4'-diphenylsulfonyl terephthalamide), p-phenylene terephthalamide / 4,4'-diphenylsulfonyl terephthalamide copolymer, and meta-aramid have flexibility. However, the combination of two or more nitrogen-containing aromatic resins is not limited to these combinations. For example, even when resins having relatively similar structures are combined, such as the combination of poly(p-phenylene terephthalamide) and poly(2-chloro-p-phenylene terephthalamide) shown in the examples, sufficient ion permeability can be obtained, and the ion permeability can be further improved by appropriately adjusting the filler content. It is preferable that two or more nitrogen-containing aromatic resins are contained in a single-layer porous layer.

[0019] When the porous layer contains a first nitrogen-containing aromatic resin and a second nitrogen-containing aromatic resin, from the viewpoint of ion permeability, the weight ratio of the first nitrogen-containing aromatic resin to the second nitrogen-containing aromatic resin is preferably 5:95 to 95:5, and more preferably 10:90 to 90:10.

[0020] In 100% by weight of the resin contained in the porous layer, the nitrogen-containing aromatic resin is preferably more than 50% by weight, more preferably 70% by weight or more, and even more preferably 90% by weight or more. In 100% by weight of the resin contained in the porous layer, the nitrogen-containing aromatic resin may be 100% by weight or less, or less than 100% by weight. It is particularly preferable that the resin contained in the porous layer consists only of a nitrogen-containing aromatic resin.

[0021] The porous layer may contain a nitrogen-containing aromatic resin and a resin other than the nitrogen-containing aromatic resin. However, in 100% by weight of the resin contained in the porous layer, the resin other than the nitrogen-containing aromatic resin is preferably less than 50% by weight, more preferably 30% by weight or less, and even more preferably 10% by weight or less. In 100% by weight of the resin contained in the porous layer, the resin other than the nitrogen-containing aromatic resin may be 0% by weight or more, or may be more than 0% by weight.

[0022] Examples of the resin other than the nitrogen-containing aromatic resin include polyolefin resins; (meth)acrylate resins; fluorine-containing resins; polyester resins; rubbers; resins having a melting point or a glass transition temperature of 180°C or higher; water-soluble polymers; polycarbonate, polyacetal, and the like. In one embodiment, the resin contained in the porous layer can be a resin excluding polyester resins. For example, when a mixture is employed in which an adhesive (meth)acrylate resin and / or a fluorine-containing resin is mixed with a nitrogen-containing aromatic resin having excellent heat resistance as the resin other than the nitrogen-containing aromatic resin, a porous layer having both heat resistance and adhesiveness can be obtained. At this time, the form of existence of the (meth)acrylate resin and / or the fluorine-containing resin is not particularly limited, and it may be in a particulate form, may exist in a mixed state with the nitrogen-containing aromatic resin, or may be segregated on the surface of the porous layer.

[0023] Examples of the polyester resin include aromatic polyesters such as polyarylate and liquid crystal polyester.

[0024] Examples of the rubbers include styrene-butadiene copolymers and their hydrogenated products, methacrylic acid ester copolymers, acrylonitrile-acrylic acid ester copolymers, styrene-acrylic acid ester copolymers, ethylene propylene rubber, polyvinyl acetate, and the like.

[0025] Examples of the fluororesin include polyvinylidene fluoride (PVdF), polytetrafluoroethylene, vinylidene fluoride - hexafluoropropylene copolymer, tetrafluoroethylene - hexafluoropropylene copolymer, tetrafluoroethylene - perfluoroalkyl vinyl ether copolymer, vinylidene fluoride - tetrafluoroethylene copolymer, vinylidene fluoride - trifluoroethylene copolymer, vinylidene fluoride - trichloroethylene copolymer, vinylidene fluoride - vinyl fluoride copolymer, vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene copolymer, ethylene - tetrafluoroethylene copolymer, etc. Among the above fluororesins, fluororubbers with a glass transition temperature of 23°C or lower are also included.

[0026] Examples of the resin with a melting point or glass transition temperature of 180°C or higher include polyphenylene ether, polysulfone, polyethersulfone, polyphenylene sulfide, polyetherimide, polyamideimide, polyetheramide, and polyetheretherketone, etc.

[0027] Examples of the water - soluble polymer include polyvinyl alcohol, polyethylene glycol, cellulose ether, sodium alginate, polyacrylic acid, polyacrylamide, polymethacrylic acid, etc.

[0028] The porous layer can be a heat - resistant layer. The heat - resistant layer means a layer having a melting temperature higher than that of the base material. The resin contained in the porous layer can be a resin having heat resistance. The resin having heat resistance can be a resin having a melting point or glass transition temperature higher than that of the resin constituting the base material. The resin contained in the porous layer is preferably insoluble in the electrolyte of the electrochemical element and electrochemically stable within the operating range of the electrochemical element.

[0029] The filler can be an inorganic filler or an organic filler. Preferred fillers are those composed of inorganic oxides such as silica, calcium oxide, magnesium oxide, magnesium hydroxide, barium sulfate, titanium oxide, alumina, mica, zeolite, aluminum hydroxide, or boehmite. Fillers composed of calcium oxide, magnesium oxide, magnesium hydroxide, barium sulfate, alumina, or boehmite are more preferred, and fillers composed of alumina are even more preferred.

[0030] Examples of the organic filler include homopolymers or copolymers of two or more monomers such as styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, and methyl acrylate; fluororesins such as polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, and polyvinylidene fluoride; melamine resin; urea resin; polyolefin; polymethacrylate, etc. The organic filler may be used alone or in combination of two or more. Among these organic fillers, polytetrafluoroethylene powder is preferred in terms of chemical stability. Also, from the viewpoint of improving the shutdown property of the separator, polyolefin may be used as the organic filler. When polyolefin is used as the organic filler, the shutdown property can be imparted to the porous layer.

[0031] The content of the filler in 100% by weight of the porous layer is 0% by weight or more and less than 20% by weight, and may be 0 to 15% by weight, 0 to 10% by weight, or 0 to 5% by weight. The filler content being 0% by weight means that the porous layer does not contain the filler. From the viewpoint of ensuring ion permeability, the filler content in 100% by weight of the porous layer may be more than 0% by weight, and may be 1% by weight or more.

[0032] The average particle size of the filler is preferably 0.01 to 1 μm, more preferably 0.01 to 0.8 μm, still more preferably 0.01 to 0.5 μm, even more preferably 0.01 to 0.1 μm, and particularly preferably 0.01 to 0.05 μm. A filler having an average particle size of 0.01 μm or more is likely to increase the pore diameter of the pores in the porous layer, so that even when the separator is compressed in the battery, the ion permeability is less likely to decrease. In addition, unevenness is likely to be formed on the surface of the porous layer, so that the antistatic property and the slipperiness of the separator can be improved. On the other hand, when the average particle size of the filler is 1 μm or less, the heat resistance of the separator can be improved and the separator can be made thinner. In order to achieve both of these characteristics, fillers having different average particle sizes may be used in combination, or a filler having a wide particle size distribution may be used. The lower limit of the average particle size of the filler is not particularly limited, but may be, for example, 0.005 μm or more.

[0033] Here, the average particle size of the filler is the average value of the spherical equivalent particle sizes of 50 fillers. The spherical equivalent particle size of the filler is a value measured by a transmission electron microscope. Specific measurement methods are exemplified as follows. 1. Using a transmission electron microscope (TEM; JEOL Ltd., transmission electron microscope JEM-2100F), at an acceleration voltage of 200 kV, the imaging magnification uses a Gatan Imaging Filter and is taken at 10,000 times. 2. For the obtained image, using image analysis software (ImageJ), trace the contour of the filler particles (primary particles) and measure the spherical equivalent particle size of the filler particles. 3. Perform the above measurement on 50 filler particles randomly extracted. The arithmetic mean of the spherical equivalent particle sizes of the 50 filler particles is defined as the average particle size of the filler.

[0034] The porous layer may contain other components other than the nitrogen-containing aromatic resin and the filler, as long as the object of the present invention is not impaired. Examples of the other components may include additives generally used in separators. The other components may be of one type or a mixture of two or more types.

[0035] Examples of the additive include a flame retardant, an antioxidant, a surfactant, a lithium imide salt, and a wax. When the porous layer is likely to be charged, the addition of a surfactant or a lithium imide salt can suppress the charging of the porous layer. Examples of the surfactant include nonionic surfactants such as glycerin fatty acid esters, polyoxyethylene alkyl ethers, and polyoxyethylene alkyl amines, anionic surfactants such as alkyl sulfonic acids, cationic surfactants such as tetraalkyl ammonium salts, and amphoteric surfactants such as alkyl betaines. Examples of the lithium imide salt include lithium bis(trifluoromethanesulfonyl)imide and lithium bis(pentafluoroethanesulfonyl)imide. In addition, the addition of a flame retardant and / or a crosslinking agent can further improve the safety and heat resistance of the separator.

[0036] The film thickness per layer of the porous layer is preferably in the range of 0.15 μm to 5 μm, more preferably in the range of 0.25 μm to 5 μm, and even more preferably in the range of 0.35 μm to 3 μm from the viewpoints of ensuring adhesion to the electrode and high energy density. When the film thickness per layer of the porous layer is 0.15 μm or more, internal short circuits due to damage to the electrochemical device can be sufficiently suppressed, and the amount of electrolyte retained in the porous layer becomes sufficient. Further, when the film thickness per layer of the porous layer is 5 μm or less, the permeation resistance of metal ions in the electrochemical device is suppressed, so that a decrease in rate characteristics and cycle characteristics can be suppressed. Further, when the film thickness per layer of the porous layer is 5 μm or less, an increase in the distance between the positive electrode and the negative electrode can also be suppressed, so that a decrease in the internal volume efficiency of the electrochemical device can be suppressed.

[0037] The weight per unit area of the porous layer, that is, the weight per unit area, can be appropriately determined in consideration of the strength, film thickness, weight, and handleability of the porous layer. The weight per unit area of each layer of the porous layer is 0.15 to 10 g / m 2It is preferably 0.25 to 5 g / m 2 More preferably, it is as follows. By setting the basis weight of the porous layer within these numerical ranges, the weight energy density and the volume energy density of the electrochemical element can be increased.

[0038] The porosity of the porous layer is preferably 20 to 90% by volume, more preferably 30 to 80% by volume so as to obtain sufficient ion permeability. Further, the pore diameter of the pores in the porous layer is preferably 1.0 μm or less, more preferably 0.5 μm or less. By setting the pore diameter of the pores to these sizes, the electrochemical element can obtain sufficient ion permeability.

[0039] In one embodiment of the present invention, the separator includes a polyolefin porous substrate, and the porous layer is laminated on the polyolefin porous substrate. That is, in one embodiment of the present invention, the separator is a separator in which the porous layer and the polyolefin porous substrate are laminated. In this specification, such a separator is also referred to as a laminated separator.

[0040] The polyolefin porous substrate means a porous substrate mainly composed of a polyolefin resin. "Mainly composed of a polyolefin resin" means that the proportion of the polyolefin resin in the porous substrate is 50% by weight or more, preferably 90% by weight or more, more preferably 95% by weight or more of the entire material constituting the porous substrate. The porous substrate can be a polyolefin porous film.

[0041] The polyolefin resin preferably contains a high molecular weight component having a weight average molecular weight of 5×10 5 ~15×10 6 . In particular, it is more preferable that the polyolefin resin contains a high molecular weight component having a weight average molecular weight of 1,000,000 or more because the strength of the obtained separator is improved.

[0042] The polyolefin resin is not particularly limited, and examples thereof include thermoplastic resins such as homopolymers or copolymers obtained by polymerizing monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene. Examples of the homopolymer include polyethylene, polypropylene, and polybutene. Examples of the copolymer include ethylene-propylene copolymer.

[0043] Among these, polyethylene is more preferable because it can prevent an excessive current from flowing through the separator at a lower temperature. Preventing the flow of this excessive current is also referred to as shutdown. Examples of the polyethylene include low-density polyethylene, high-density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), and ultra-high molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more. Among these, ultra-high molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more is more preferable.

[0044] The polyolefin porous substrate may have a multilayer structure composed of two or more layers. Examples of the polyolefin porous substrate having a multilayer structure include those obtained by laminating a layer mainly composed of polyethylene and a layer mainly composed of polypropylene. The number of laminated layers is not particularly limited, and it may be two layers composed of a layer mainly composed of polyethylene and a layer mainly composed of polypropylene, or three layers composed of a combination of a layer mainly composed of polyethylene and a layer mainly composed of polypropylene. By adopting a multilayer structure of a layer mainly composed of polyethylene and a layer mainly composed of polypropylene, it is possible to achieve both shutdown performance and heat resistance.

[0045] The polyolefin porous substrate may have a crosslinked structure. The crosslinked structure can be introduced, for example, by using a silane-modified polyolefin. Since the polyolefin porous substrate having a crosslinked structure is excellent in heat resistance, the heat resistance of the separator can be further improved by combining it with a porous layer having heat resistance. Note that the crosslinked structure may be formed between the polyolefin porous substrate and the porous layer.

[0046] The film thickness of the porous substrate is preferably 4 to 40 μm, more preferably 5 to 20 μm. If the film thickness of the porous substrate is 4 μm or more, internal short circuit of the electrochemical element can be sufficiently prevented. On the other hand, if the film thickness of the porous substrate is 40 μm or less, enlargement of the electrochemical element can be prevented.

[0047] The weight per unit area of the porous substrate, that is, the weight per unit area, can be appropriately determined in consideration of strength, film thickness, weight, and handleability. However, so as to increase the weight energy density and the volume energy density of the electrochemical element, the weight per unit area is preferably 4 to 20 g / m 2 and more preferably 4 to 12 g / m 2 and even more preferably 5 to 10 g / m 2 .

[0048] The porous substrate has a large number of pores connected inside thereof, and it is possible to allow gas and liquid to pass from one surface to the other surface. The air permeability of the porous substrate is preferably 30 to 500 s / 100 mL, more preferably 50 to 300 s / 100 mL. By having the above air permeability, sufficient ion permeability can be obtained. The air permeability represents a value measured with a King Research air permeability tester in accordance with JIS P8117.

[0049] The porosity of the porous substrate is preferably 20 to 80% by volume, more preferably 30 to 75% by volume, so as to increase the retention amount of the electrolyte solution and obtain a function of reliably preventing an excessive current from flowing at a lower temperature. The pore diameter of the pores of the porous substrate is preferably 0.3 μm or less, more preferably 0.14 μm or less, so as to obtain sufficient ion permeability and prevent the particles from entering the positive electrode and the negative electrode.

[0050] The film thickness of the separator is preferably 3.5 to 45 μm, more preferably 3.5 to 25 μm, still more preferably 3.5 to 20 μm, and particularly preferably 3.5 to 18 μm. If the film thickness of the separator is 3.5 μm or more, an internal short circuit of the electrochemical element can be sufficiently prevented. On the other hand, if the film thickness of the separator is 45 μm or less, an increase in the size of the electrochemical element can be prevented. The film thickness of the separator may be 5.5 to 45 μm or 6 to 25 μm.

[0051] The air permeability of the separator is preferably 30 to 1000 s / 100 mL, more preferably 50 to 800 s / 100 mL, and still more preferably 70 to 500 s / 100 mL. By having the air permeability, the separator can obtain sufficient ion permeability in the electrochemical element. The air permeability represents a value measured by a King-type air permeability tester in accordance with JIS P8117.

[0052] The separator may be configured such that a porous layer is provided on one side of the above-described porous substrate, or a porous layer may be provided on both sides of the porous substrate. Further, one porous layer and the other porous layer provided on both sides of the porous substrate may have the same film thickness, basis weight, and porosity, or may be different from each other. Furthermore, the porous layers provided on both sides of the porous substrate may have different compositions from each other. Different compositions from each other mean that the types of resin and filler constituting the porous layer, as well as the filling amount of the filler, etc. are different in the front and back porous layers. Note that the content exemplified for the above-described porous layer can be applied to the resin, filler, and the filling amount of the filler.

[0053] The separator may optionally contain another functional layer different from the above-described porous substrate and porous layer (e.g., heat-resistant layer) within a range that does not impair the object of the present invention. Examples of the other functional layer include known porous layers such as an adhesive layer, a protective layer, a shutdown layer, an antistatic layer, and a lubricious layer.

[0054] The other functional layer may be provided on one side or both sides of the separator. When the separator has the above-described porous layers on both sides of the porous substrate, the other functional layer may be provided on the porous layers on both sides, or may be provided on the porous layer on one side. When the separator has the above-described porous layer on only one side of the porous substrate, the other functional layer may be provided on the porous layer, or may be provided on the surface of the porous substrate where the porous layer is not provided. The other functional layer may be provided as the outermost layer of the separator.

[0055] For example, the separator further includes an adhesive layer separately from the above-described porous base material and porous layer. In this specification, the adhesive layer means a porous layer having adhesiveness. The adhesive layer can be provided on the surface of the separator that contacts the electrode. Examples of the components contributing to the adhesiveness included in the adhesive layer include acrylic resins and PVdF-based resins. As the acrylic resin, for example, those described in paragraphs

[0072] to

[0088] of JP-A-2024-006988 can be used. As the PVdF-based resin, for example, those described in paragraphs

[0017] to

[0022] of JP-A-2017-168419 can be used. The acrylic resin and the PVdF-based resin may be used alone or in combination. The adhesive layer may further contain a filler in addition to the components contributing to the adhesiveness. As the filler, the same ones as those added to the porous layer can be used.

[0056] The state of existence of the adhesive layer is not particularly limited, and the components contributing to the adhesiveness may exist in a particulate state or may exist as a homogeneous coating layer. Further, the adhesive layer may be present in a dot shape or a stripe shape by pattern coating. By providing the adhesive layer, the separator can be fixed to the electrode via the adhesive layer to form an electrode laminate, so that the handleability and heat resistance of the electrode laminate can be improved. Furthermore, by making the adhesive layer exist in a particulate, dot, or stripe shape, a decrease in the ion permeability of the laminated separator can be suppressed.

[0057] For example, the separator further includes a shutdown layer separately from the above-described porous base material and porous layer. In this specification, the shutdown layer means a particle layer having shutdown properties. The shutdown layer can be provided on the surface of the separator that contacts the electrode. Examples of the components contributing to the shutdown properties included in the shutdown layer include polyethylene particles.

[0058] For example, the separator further includes an antistatic layer separately from the above-described porous base material and porous layer. In this specification, the antistatic layer means a layer having antistatic properties. The antistatic layer can be provided on the surface of the separator that contacts the electrode. As the component contributing to the antistatic property contained in the antistatic layer, the same materials as those exemplified as the surfactant added to the porous layer can be used.

[0059] For example, the separator further includes a lubricious layer separately from the above-described porous base material and porous layer. In this specification, the lubricious layer means a layer that imparts slipperiness to the separator. The lubricious layer can be provided on the surface of the separator that contacts the electrode. Components contributing to the slipperiness contained in the lubricious layer include antiblocking agents or fillers, etc. By providing surface irregularities, in addition to the slipperiness of the separator, the antistatic property can be improved. Note that a porous layer with surface irregularities formed by sandblasting the surface of the porous layer may be used as the lubricious layer.

[0060] As another method for suppressing the charging of the porous layer other than the above, a unit or substituent for improving hydrophilicity may be introduced into the structure of the nitrogen-containing aromatic resin constituting the porous layer. Also, as a resin other than the nitrogen-containing aromatic resin, the charging of the porous layer can be suppressed by unevenly distributing a conductive polymer on the surface of the porous layer.

[0061] [2. Method for manufacturing a separator for an electrochemical element] A porous layer can be formed using a coating liquid obtained by dissolving or dispersing a resin in a solvent. Note that the solvent can also be said to be a dispersion medium for dispersing the resin. Examples of the resin include the above-described nitrogen-containing aromatic resin and resins other than the nitrogen-containing aromatic resin. Examples of the method for forming the coating liquid include a mechanical stirring method, an ultrasonic dispersion method, a high-pressure dispersion method, a media dispersion method, etc.

[0062] Examples of the method for forming the porous layer include, for example, a method in which a coating solution is directly applied to the surface of a substrate and then the solvent is removed; a method in which a coating solution is applied to a suitable support, the solvent is removed to form a porous layer, this porous layer is pressure-bonded to the substrate, and then the support is peeled off; a method in which a coating solution is applied to a suitable support, the substrate is pressure-bonded to the coated surface, and then the solvent is removed after the support is peeled off; and a method in which dip coating is performed by immersing the substrate in the coating solution and then the solvent is removed, etc.

[0063] The solvent preferably has no adverse effect on the substrate, uniformly and stably dissolves the resin, and uniformly and stably disperses the filler. Examples of the solvent include N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide, N,N-dimethylformamide, acetone, and water, etc.

[0064] The coating solution may contain a filler. As components other than the resin and the filler, the coating solution may appropriately contain a dispersant, a plasticizer, a surfactant, a pH adjuster, etc.

[0065] As a method for applying the coating solution to the substrate, a conventionally known method can be adopted. Specifically, for example, a gravure coater method, a dip coater method, a bar coater method, a die coater method, etc. can be mentioned.

[0066] When the coating solution contains an aramid resin, the aramid resin can be precipitated by applying moisture to the coated surface. Thereby, a porous layer may be formed. The specific method for applying moisture to the coated surface is not particularly limited, and examples include exposing it to an atmosphere with high humidity, spraying water with a spray, etc., and spraying steam with a nozzle, etc.

[0067] In particular, as a method for manufacturing a laminated separator, for example, in the above-described method for manufacturing a porous layer, a method of using the above-described porous substrate as the substrate to which the coating solution is applied can be mentioned.

[0068] The method for producing the porous substrate is not particularly limited. For example, a sheet-like polyolefin resin composition is produced by kneading a polyolefin resin, a pore-forming agent such as an inorganic filler or a plasticizer, and optionally an antioxidant or the like, and then extruding. Then, the pore-forming agent is removed from the sheet-like polyolefin resin composition with an appropriate solvent. Thereafter, a porous substrate can be produced by stretching the polyolefin resin composition from which the pore-forming agent has been removed.

[0069] The inorganic filler is not particularly limited, and examples thereof include inorganic fillers, specifically calcium carbonate and the like. The plasticizer is not particularly limited, and examples thereof include low molecular weight hydrocarbons such as liquid paraffin.

[0070] Although the method for forming a porous layer on the porous substrate has been described above, instead of the porous substrate, an electrode such as a positive electrode or a negative electrode described later may be used as the substrate. When an electrode is used as the substrate, since the coating liquid is directly applied onto the electrode, a laminate in which the electrode and the porous layer are laminated can be obtained. Note that, as a method for applying the coating liquid onto the electrode, the same method as the method for applying it onto the porous substrate can be employed.

[0071] [3. Member for Electrochemical Element, Electrochemical Element] A member for an electrochemical element according to an embodiment of the present invention includes a positive electrode, the separator for an electrochemical element described above, and a negative electrode, which are arranged in this order. Further, an electrochemical element according to an embodiment of the present invention includes the separator for an electrochemical element described above.

[0072] Examples of the electrochemical element include secondary batteries and capacitors. Examples of the secondary battery include non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries. Examples of the capacitor include electric double layer capacitors. The shape of the non-aqueous electrolyte secondary battery is not particularly limited, and may be a thin plate (paper) type, a disk type, a cylindrical type, a prismatic type such as a rectangular parallelepiped, or the like.

[0073] For example, a member for an electrochemical element can be formed by arranging a positive electrode, the above-described separator, and a negative electrode in this order. Here, the porous layer can be present between the porous substrate and at least one of the positive electrode and the negative electrode. Next, the member for the electrochemical element is placed in a container that serves as a casing for the electrochemical element. Thereby, an electrochemical element can be manufactured. In the case of a non-aqueous electrolyte secondary battery, after filling the inside of the container with a non-aqueous electrolyte described later, it is sealed while reducing the pressure.

[0074] <Positive electrode> The positive electrode is not particularly limited as long as it is generally used as the positive electrode of an electrochemical element. For example, as the positive electrode, a positive electrode sheet having a structure in which an active material layer containing a positive electrode active material and a binder is formed on a positive electrode current collector can be used. Note that the active material layer may further contain a conductive agent.

[0075] Examples of the positive electrode active material include materials capable of doping and undoping metal ions such as lithium ions or sodium ions. Specific examples of such materials include lithium-containing composite metal oxides containing lithium (Li) and at least one transition metal selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, and Al. Examples of such lithium-containing composite metal oxides include LiCoO2, LiNiO2, LiMn2O4, Li2MnO3, LiNi x Mn y Co 1-x-y O2 [0 < x + y < 1], LiNi x Co y Al 1-x-y O2 [0 < x + y < 1], LiCr 0.5 Mn 0.5 O2, LiFePO4, Li2FeP2O7, LiMnPO4, LiFeBO3, Li3V2(PO4)3, Li2CuO2, Li2FeSiO4, Li2MnSiO4, etc.

[0076] Examples of the conductive agent include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black (e.g., acetylene black), pyrolytic carbons, fibrous carbon materials, and fired products of organic polymer compounds. The conductive agent may be used alone or in combination of two or more. The proportion of the conductive agent in the positive electrode mixture is preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. When using fibrous carbon materials such as graphitized carbon fibers and carbon nanotubes as the conductive agent, it is also possible to reduce this proportion.

[0077] As the binder, a thermoplastic resin can be used. For example, fluorine-based resins such as PVdF, polytetrafluoroethylene (PTFE), tetrafluoroethylene - hexafluoropropylene - vinylidene fluoride copolymer, hexafluoropropylene - vinylidene fluoride copolymer, tetrafluoroethylene - perfluorovinyl ether copolymer, acrylic resins, styrene - butadiene rubber, polyimide resins, and polyolefin resins can be mentioned. Note that the binder also has a function as a thickener. These thermoplastic resins may be used as a mixture of two or more. By using a fluorine-based resin and a polyolefin resin as the binder, and setting the proportion of the fluorine-based resin to 1% by mass or more and 10% by mass or less, and the proportion of the polyolefin resin to 0.1% by mass or more and 2% by mass or less with respect to the entire positive electrode mixture, a positive electrode mixture with high adhesion to the positive electrode current collector and high internal binding force within the positive electrode mixture can be obtained.

[0078] Examples of the positive electrode current collector include conductors such as Al, Ni, and stainless steel. Among them, Al is more preferable because it is easy to process into a thin film and is inexpensive.

[0079] Examples of the method for manufacturing the positive electrode sheet include a method of pressure molding a positive electrode active material, a conductive agent, and a binder (positive electrode mixture) on a positive electrode current collector; a method of making the positive electrode mixture into a paste using an appropriate organic solvent, then coating the paste on the positive electrode current collector, drying, and then applying pressure to fix it to the positive electrode current collector.

[0080] Examples of the organic solvent that can be used in the above method include amine solvents such as N,N-dimethylaminopropylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; ketone solvents such as methyl ethyl ketone; ester solvents such as methyl acetate; amide solvents such as dimethylacetamide and NMP, and the like.

[0081] Examples of the method for applying the paste of the positive electrode active material to the positive electrode current collector include slit die coating method, screen coating method, curtain coating method, knife coating method, gravure coating method, and electrostatic spraying method, and the like.

[0082] <Negative electrode> The negative electrode is not particularly limited as long as it is generally used as the negative electrode of an electrochemical device. For example, as the negative electrode, a negative electrode sheet having a structure in which an active material layer containing a negative electrode active material and a binder is formed on a negative electrode current collector can be used. The active material layer may further contain a conductive agent.

[0083] Examples of the negative electrode active material include materials capable of doping and dedoping metal ions such as lithium ions or sodium ions. Examples of such materials include carbonaceous materials, chalcogen compounds (oxides, sulfides, etc.), nitrides, metals or alloys, and materials capable of doping and dedoping lithium ions at a potential lower than that of the positive electrode. Examples of the carbonaceous materials include natural graphite, artificial graphite, cokes, carbon black, and pyrolytic carbons.

[0084] Examples of the oxide that can be used as the negative electrode active material include silicon oxides represented by the formula SiO x (where x is a positive real number); titanium oxides represented by the formula TiO x (where x is a positive real number); vanadium oxides represented by the formula VO x (where x is a positive real number); iron oxides represented by the formula FeO such as Fe3O4, Fe2O3, and FeO xIron oxides represented by x Tin oxides represented by x Tungsten oxides represented by 12 Composite metal oxides containing lithium and titanium or vanadium such as Li4Ti5O

[0085] Sulfides that can be used as negative electrode active materials include Ti2S3, TiS2, TiS, etc., represented by x Titanium sulfides represented by x Vanadium sulfides represented by x Iron sulfides represented by x Molybdenum sulfides represented by x Tin sulfides represented by x Tungsten sulfides represented by x Antimony sulfides represented by x Selenium sulfides represented by

[0086] Nitrides that can be used as negative electrode active materials include Li3N, Li 3-x A x Lithium-containing nitrides such as N (where A is either Ni or Co or both, and 0 < x < 3).

[0087] These carbonaceous materials, oxides, sulfides, and nitrides may be used alone or in combination of two or more. Also, these carbonaceous materials, oxides, sulfides, and nitrides may be either crystalline or amorphous.

[0088] In addition, examples of metals that can be used as the negative electrode active material include lithium metal, silicon metal, and tin metal.

[0089] Examples of alloys that can be used as the negative electrode active material include lithium alloys such as Li-Al, Li-Ni, Li-Si, Li-Sn, and Li-Sn-Ni; silicon alloys such as Si-Zn; tin alloys such as Sn-Mn, Sn-Co, Sn-Ni, Sn-Cu, and Sn-La; and alloys such as Cu2Sb and La3Ni2Sn7.

[0090] These metals and alloys are mainly used alone as electrodes after being processed into, for example, foil form. Among the above negative electrode active materials, carbonaceous materials mainly composed of graphite such as natural graphite and artificial graphite are preferably used. This is because the potential of the negative electrode hardly changes from the uncharged state to the fully charged state during charging (good potential flatness), the average discharge potential is low, and the capacity retention rate is high when repeatedly charged and discharged (good cycle characteristics). The shape of the carbonaceous material can be, for example, flaky like natural graphite, spherical like mesocarbon microbeads, fibrous like graphitized carbon fibers, or an aggregate of fine powders.

[0091] Examples of the negative electrode current collector include Cu, Ni, and stainless steel. Cu is more preferable because it is difficult to form an alloy with lithium and is easy to process into a thin film.

[0092] Examples of the method for manufacturing the negative electrode sheet include a method of pressure molding the negative electrode active material on the negative electrode current collector; a method of making the negative electrode active material into a paste using an appropriate organic solvent, then coating the paste on the negative electrode current collector, drying it, and then pressing it to adhere it to the negative electrode current collector; and the like. The paste preferably contains the above-mentioned conductive agent and the binder.

[0093] The negative electrode sheet may contain a binder as required. Examples of the binder include thermoplastic resins, and specifically, PVdF, thermoplastic polyimide, carboxymethyl cellulose, polyolefin resin, and the like can be mentioned.

[0094] <Non-aqueous electrolyte> The non-aqueous electrolyte is not particularly limited as long as it is generally a non-aqueous electrolyte used in an electrochemical device, for example, a non-aqueous electrolyte secondary battery. As the non-aqueous electrolyte, for example, a non-aqueous electrolyte obtained by dissolving a lithium salt in an organic solvent can be used. Examples of the lithium salt include LiClO4, LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, LiN(SO2C2F5)2, LiN(SO2CF3)(COCF3), Li(C4F9SO3), Li2B 10 Cl 10 , LiBOB (where BOB is bis(oxalato)borate), LiFSI (where FSI is bis(fluorosulfonyl)imide), lithium lower aliphatic carboxylate salts, LiAlCl4, and the like. The lithium salt may be used alone or in combination of two or more. Among them, as the electrolyte, it is preferable to use one containing at least one selected from the group consisting of LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(SO2CF3)2, and LiC(SO2CF3)3 containing fluorine.

[0095] Examples of the organic solvent include carbonates such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, and 1,2-di(methoxycarbonyloxy)ethane; ethers such as 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran; esters such as methyl formate, methyl acetate, and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; carbamates such as 3-methyl-2-oxazolidone; sulfur-containing compounds such as sulfolane, dimethyl sulfoxide, and 1,3-propane sultone; or a solvent obtained by further introducing a fluoro group into these organic solvents (a solvent in which one or more of the hydrogen atoms of the organic solvent are replaced with fluorine atoms). The organic solvent may be used alone or in combination of two or more. Among them, a mixed solvent containing carbonates is preferable, and a mixed solvent of a cyclic carbonate and an acyclic carbonate and a mixed solvent of a cyclic carbonate and ethers are more preferable. As the mixed solvent of a cyclic carbonate and an acyclic carbonate, a mixed solvent containing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate is preferable. The electrolytic solution using such a mixed solvent has a wide operating temperature range, is less likely to deteriorate even when charged and discharged at a high current rate, is less likely to deteriorate even when used for a long time, and has many features such as being hardly decomposable even when a graphite material such as natural graphite or artificial graphite is used as the negative electrode active material.

[0096] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0097] One embodiment of the present invention may include the following configuration. <1>A separator for an electrochemical element, comprising a porous layer containing two or more nitrogen-containing aromatic resins and having a filler content of 0 wt% or more and less than 20 wt%. <2>The basis weight of the porous layer is 0.15 to 10 g / m 2 The separator for an electrochemical element according to <1>. <3>The film thickness of the porous layer is 0.15 to 5 μm. The separator for an electrochemical element according to <1> or <2>. <4>The nitrogen-containing aromatic resin contains an aramid resin. The separator for an electrochemical element according to any one of <1> to <3>. <5>Comprising a polyolefin porous substrate, and the porous layer is laminated on the polyolefin porous substrate. The separator for an electrochemical element according to any one of <1> to <4>. <6>The film thickness is 5.5 to 45 μm. The separator for an electrochemical element according to <5>. <7>Separate from the polyolefin porous substrate and the porous layer, further comprising an adhesive layer. The separator for an electrochemical element according to <5> or <6>. <8>A member for an electrochemical element, in which a positive electrode, a separator for an electrochemical element according to any one of <1> to <7>, and a negative electrode are arranged in this order. <9>An electrochemical element comprising a separator for an electrochemical element according to any one of <1> to <7>. <10>The electrochemical element according to <9>, which is a secondary battery or a capacitor.

Example

[0098] One embodiment of the present invention will be described below.

[0099] <Measurement of the air permeability of the separator> The separator was cut into a square with a size of 60 mm × 60 mm and used as a sample for measuring the air permeability of the separator. The sample for measuring the air permeability of the separator was placed in a digital Wangyan type air permeability tester EGO1 manufactured by Asahi Seiko Co., Ltd., and the air permeability of the separator was measured to obtain the air permeability of the separator (unit: s / 100 mL).

[0100] <Measurement of the moisture content of the separator> Using a Karl Fischer moisture meter (manufactured by Metrohm Shibata Co., Ltd.), the moisture content of the separator was measured based on the Karl Fischer method.

[0101] <Measurement of the gas generation amount> A single-layer laminated cell was fabricated using a separator, a positive electrode formed on an Al current collector (including lithium metal composite oxide powder, acetylene black, and PVdF), a negative electrode formed on a Cu current collector (including artificial graphite, styrene-butadiene rubber, and carboxymethyl cellulose), and an electrolytic solution (a mixed solution of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 3:2:5, dissolved with LiPF6 to a concentration of 1.0 mol / L).

[0102] The above-mentioned laminated cell was charged to SOC 100% by CC-CV charging at a test temperature of 25°C with a current of 0.1 C A, and then formed under the condition of discharging to 2.5 V at a current of 0.2 C A. After that, it was opened once to vent the gas, and the volume before storage was measured by the Archimedes method. Then, it was charged to 4.3 V, stored in a constant temperature bath at 60°C for 7 days, and the volume of the laminated cell that was discharged to 2.7 V at a current value of 1 C A was measured by the Archimedes method. The gas generation amount was obtained from the difference between the volume after storage at 60°C for 7 days and the volume before storage.

[0103] The Archimedes method is a method of measuring the actual volume of the entire laminated cell from the difference between the weight in air and the weight in water of the laminated cell using a digital hydrometer.

[0104] <Measurement of the film thickness of the separator> Using a high-precision digital length measuring instrument (manufactured by Mitutoyo Corporation), the film thickness of the separator was measured. Specifically, each separator was cut into a square with a side length of 8 cm, and 5-point measurements were taken within the range of the square, and the film thickness was obtained from the average value of these 5 points.

[0105] <Charpy test: Measurement of the swing-up angle> Ten strip-shaped samples measuring 80 mm × 10 mm with the MD direction as the longitudinal direction were cut out from the separator. Using these strip-shaped samples, a Charpy test was conducted in accordance with JIS K7111-1 (2012). The measuring apparatus and measuring conditions used were as follows. Apparatus: Universal impact tester (manufactured by Yasuda Seiki Seisakusho, No. 258) Test piece: 80 mm × 10 mm Lifting angle: 150° Number of measurements: 10 times Pendulum (hammer) capacity: 1 J Number of test pieces: 1 piece Notch of test piece: None The average value of the lifting angles obtained from 10 measurements was taken as the lifting angle in the MD direction.

[0106] Also, a Charpy test was carried out in the same manner as in the case of the MD direction as the longitudinal direction, except that ten strip-shaped samples measuring 80 mm × 10 mm with the TD direction as the longitudinal direction were cut out. The average value of the lifting angles obtained from 10 measurements was taken as the lifting angle in the TD direction.

[0107] [Synthesis Example 1: Synthesis of Resin A] Resin A (poly(4,4'-diphenylsulfonylterephthalamide)) was synthesized according to the following procedure. 1. A 0.5 L separable flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and powder addition port was thoroughly dried. 2. 408.6 g of NMP was charged into the flask. Further, 31.4 g of calcium chloride (dried at 200 °C for 2 hours) was added, and the temperature was raised to 100 °C. 3. After the calcium chloride was completely dissolved, 31.97 g of 4,4'-diaminodiphenylsulfone was added at 100 °C and completely dissolved. 4. The resulting solution was cooled to room temperature. While maintaining the temperature of the solution at 25 ± 2 °C, a total of 25.88 g of terephthaloyl chloride was added in three portions. 5. While maintaining the temperature of the obtained solution at 25 ± 2°C, the solution was aged for 1 hour to obtain a solution containing Resin A.

[0108] [Synthesis Example 2: Synthesis of Resin B] Resin B (poly(p-phenyleneterephthalamide)) was synthesized according to the following procedure. 1. A 0.5 L separable flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and powder addition port was thoroughly dried. 2. 408.6 g of NMP was charged into the flask. Further, 31.4 g of calcium chloride (dried at 200°C for 2 hours) was added, and the temperature was raised to 100°C. 3. After calcium chloride was completely dissolved, the temperature of the obtained solution was returned to room temperature. Then, 13.20 g of p-phenylenediamine was added and completely dissolved. 4. While maintaining the temperature of the obtained solution at 25 ± 2°C, a total of 24.24 g of terephthaloyl dichloride was added in three portions. 5. While maintaining the temperature of the obtained solution at 25 ± 2°C, the solution was aged for 1 hour to obtain a solution containing Resin B.

[0109] [Synthesis Example 3: Synthesis of Resin C] Resin C (poly(2-chlorop-phenyleneterephthalamide)) was synthesized according to the following procedure. 1. A 0.5 L separable flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and powder addition port was thoroughly dried. 2. 441.4 g of NMP was charged into the flask. Further, 33.9 g of calcium chloride (dried at 200°C for 2 hours) was added, and the temperature was raised to 100°C. 3. After calcium chloride was completely dissolved, the temperature of the obtained solution was returned to room temperature. Then, 5.18 g of 2-chloro-1,4-phenylenediamine was added and completely dissolved. 4. While maintaining the temperature of the obtained solution at 25 ± 2°C, a total of 7.13 g of terephthaloyl dichloride was added in three portions. 5. While maintaining the temperature of the obtained solution at 25 ± 2°C, the solution was aged for 1 hour to obtain a solution containing Resin C.

[0110] [Synthesis Example 4: Dissolution of Resin D] A solution containing Resin D (poly[N,N'-(1,3-phenylene)isophthalamide]) was obtained by the following procedure. 1. A 0.5 L separable flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and powder addition port was thoroughly dried. 2. 408.6 g of NMP was charged into the flask. Further, 31.4 g of calcium chloride (dried at 200 °C for 2 hours) was added, and the temperature was raised to 100 °C. 3. After the calcium chloride was completely dissolved, 28.09 g of poly[N,N'-(1,3-phenylene)isophthalamide] (manufactured by Aldrich) was added and stirred at 125 °C until completely dissolved. 4. The resulting solution was cooled to room temperature to obtain a solution containing Resin D.

[0111] [Example 1] A porous layer with a weight ratio of Resin A:Resin B of 90:10 was prepared. Specifically, the solutions obtained in Synthesis Examples 1 and 2 were mixed so that the weight ratio of Resin A:Resin B was 90:10. To 500 g of the resulting mixture (1), 17.27 g of calcium carbonate was added and stirred for 10 minutes to neutralize the solution, obtaining a neutralized solution (1). Then, the neutralized solution (1) was diluted with NMP and degassed under reduced pressure to prepare a slurry-like coating solution (1). The solid content concentration of the coating solution (1) was 4.5% by weight.

[0112] The coating solution (1) was applied to a polyethylene porous film (thickness: 10.3 μm, air permeability: 180 s / 100 mL) and treated in an oven at 50 °C and 70% humidity for 1 minute to deposit a porous layer (1). Then, it was washed with water and dried to obtain a separator provided with the porous layer (1). The weight per unit area of the porous layer (1) was 1.7 g / m 2 .

[0113] [Example 2] Separator having a porous layer (2) was obtained by performing the same operations as in Example 1, except that the solutions obtained in Synthesis Examples 1 and 2 were mixed so that the weight ratio of Resin A: Resin B was 70:30. The areal weight of the porous layer (2) was 1.4 g / m 2 was obtained.

[0114] [Example 3] Separator having a porous layer (3) was obtained by performing the same operations as in Example 1, except that the solutions obtained in Synthesis Examples 1 and 2 were mixed so that the weight ratio of Resin A: Resin B was 50:50. The areal weight of the porous layer (3) was 1.2 g / m 2 was obtained.

[0115] [Example 4] Separator having a porous layer (4) was obtained by performing the same operations as in Example 1, except that the solutions obtained in Synthesis Examples 1 and 2 were mixed so that the weight ratio of Resin A: Resin B was 40:60 and the film thickness of the polyethylene porous film was changed to 8.9 μm. The areal weight of the porous layer (4) was 1.6 g / m 2 was obtained.

[0116] [Example 5] Separator having a porous layer (5) was obtained by performing the same operations as in Example 1, except that the solutions obtained in Synthesis Examples 1 and 2 were mixed so that the weight ratio of Resin A: Resin B was 30:70 and the film thickness of the polyethylene porous film was changed to 8.3 μm. The areal weight of the porous layer (5) was 1.4 g / m 2 was obtained.

[0117] [Example 6] Separator having a porous layer (6) was obtained by performing the same operations as in Example 1, except that the solutions obtained in Synthesis Examples 1 and 2 were mixed so that the weight ratio of Resin A: Resin B was 10:90 and the film thickness of the polyethylene porous film was changed to 8.3 μm. The areal weight of the porous layer (6) was 1.0 g / m 2 was obtained.

[0118] [Example 7] A separator having a porous layer (7) was obtained in the same manner as in Example 3, except that alumina (average particle size: 13 nm) was added so that the weight ratio of resin A: resin B: alumina was 50:50:1. The alumina content in the porous layer (7) was about 1.0% by weight. The basis weight of the porous layer (7) was 1.7 g / m 2 was obtained.

[0119] [Example 8] A separator having a porous layer (8) was obtained in the same manner as in Example 7, except that alumina was added so that the weight ratio of resin A: resin B: alumina was 50:50:5. The alumina content in the porous layer (8) was about 4.8% by weight. The basis weight of the porous layer (8) was 2.1 g / m 2 was obtained.

[0120] [Example 9] A separator having a porous layer (9) was obtained in the same manner as in Example 7, except that alumina was added so that the weight ratio of resin A: resin B: alumina was 50:50:20. The alumina content in the porous layer (9) was about 16.7% by weight. The basis weight of the porous layer (9) was 1.0 g / m 2 was obtained.

[0121] [Example 10] A separator having a porous layer (10) was obtained in the same manner as in Example 1, except that the solutions obtained in Synthesis Examples 2 and 3 were mixed so that the weight ratio of resin B: resin C was 50:50. The basis weight of the porous layer (10) was 1.6 g / m 2 was obtained.

[0122] [Example 11] A separator having a porous layer (11) was obtained in the same manner as in Example 10, except that alumina was added so that the weight ratio of resin B: resin C: alumina was 50:50:20. The alumina content in the porous layer (11) was about 16.7% by weight. The basis weight of the porous layer (11) was 1.7 g / m 2 was obtained.

[0123] [Example 12] A separator having a porous layer (12) was obtained in the same manner as in Example 1, except that the solutions obtained in Synthesis Examples 1 and 4 were mixed so that the weight ratio of Resin A to Resin D was 50:50. The basis weight of the porous layer (12) was 0.9 g / m 2 .

[0124] [Example 13] A separator having a porous layer (13) was obtained in the same manner as in Example 1, except that the solutions obtained in Synthesis Examples 2 and 4 were mixed so that the weight ratio of Resin B to Resin D was 50:50. The basis weight of the porous layer (13) was 1.9 g / m 2 .

[0125] [Example 14] A separator having a porous layer (14) was obtained in the same manner as in Example 1, except that the solutions obtained in Synthesis Examples 1, 2, and 4 were mixed so that the weight ratio of Resin A: Resin B: Resin D was 34:33:33. The basis weight of the porous layer (14) was 1.1 g / m 2 .

[0126] [Example 15] A separator having porous layers (15) on both sides was obtained in the same manner as in Example 1, except that the solutions obtained in Synthesis Examples 1 and 2 were mixed so that the weight ratio of Resin A to Resin B was 40:60, the film thickness of the polyethylene porous film was changed to 5.2 μm, and the porous layer was coated on both sides. The combined basis weight of the porous layers (15) on both sides was 0.8 g / m 2 .

[0127] [Comparative Example 1] A separator was obtained in the same manner as in Example 1, except that the solution obtained in Synthesis Example 1 was used so that the weight ratio of Resin A to Resin B was 100:0.

[0128] [Comparative Example 2] Separator was obtained by performing the same operations as in Example 1 except that the solution obtained in Synthesis Example 2 was used so that the weight ratio of Resin A to Resin B was 0:100.

[0129] [Comparative Example 3] Separator was obtained by performing the same operations as in Example 10 except that the solution obtained in Synthesis Example 3 was used so that the weight ratio of Resin B to Resin C was 0:100.

[0130] [Comparative Example 4] An attempt was made to produce a separator by performing the same operations as in Example 12 except that the solution obtained in Synthesis Example 4 was used so that the weight ratio of Resin A to Resin D was 0:100, but a separator could not be obtained due to poor precipitation.

[0131] [Comparative Example 5] A separator having a porous layer (C5) was obtained by performing the same operations as in Comparative Example 2 except that alumina (average particle size: 13 nm) was added so that the weight ratio of Resin B to alumina was 100:100. The content of alumina contained in the porous layer (C5) was 50% by weight. The weight basis of the porous layer (C5) was 1.7 g / m 2 It was.

[0132] [Comparative Example 6] A separator having a porous layer (C6) was obtained by performing the same operations as in Example 7 except that alumina was added so that the weight ratio of Resin A to Resin B to alumina was 50:50:100. The content of alumina contained in the porous layer (C6) was 50% by weight. The weight basis of the porous layer (C6) was 1.6 g / m 2 It was.

[0133] [Results] The compositions and evaluation results of the examples and comparative examples are shown in Tables 1 to 3.

[0134] [Table 1]

[0135] In any of the examples and comparative examples, the thickness of the porous layer was about the same. In Comparative Examples 1 to 3, since no filler was mixed and no two or more resins were mixed either, the amount of moisture mixed in during the manufacturing process was expected to be small, but the air permeability was high. Regarding Comparative Example 4, the precipitation of the porous layer was poor and data could not be obtained. In Comparative Examples 5 and 6, although the air permeability was somewhat low, the ratio of the filler exceeded 20% by weight and the moisture content was high.

[0136] In contrast, in Examples 1 to 15 using two or more nitrogen-containing aromatic resins and with the ratio of the filler being less than 20% by weight, the air permeability was lower compared to Comparative Examples 1 to 3, and the moisture content was lower compared to Comparative Examples 5 and 6. That is, in Examples 1 to 15, it was possible to achieve both high ion permeability and low moisture content.

[0137]

Table 2

[0138] In Examples 3 and 8 with low moisture content, the gas generation amount was small. On the other hand, in Comparative Examples 5 and 6 with high moisture content, the gas generation amount was large.

[0139]

Table 3

[0140] As shown in Table 3, in Example 3, the upward swing angle in the Charpy test was smaller than that in Comparative Example 5. Generally, the upward swing angle in the Charpy test corresponds to the energy consumed when the test piece is broken. When the energy is small, the upward swing angle becomes large, and when the energy is large, the upward swing angle becomes small. Since the separator according to an embodiment of the present invention has a smaller upward swing angle compared to the conventional separator, the energy consumed when the test piece is broken is large. That is, it was found that the separator according to an embodiment of the present invention is superior in impact resistance to the conventional separator. From the above, it is considered that a battery equipped with the separator according to an embodiment of the present invention is further superior in safety than the conventional battery.

Industrial Applicability

[0141] One aspect of the present invention can be used for an electrochemical element.

Claims

1. A separator for an electrochemical element, comprising a porous layer containing two or more kinds of nitrogen-containing aromatic resins and having a filler content of 0% by weight or more and less than 20% by weight.

2. The porous layer has a basis weight of 0.15 to 10 g / m ２ 2. The separator for an electrochemical element according to claim 1,

3. 2. The separator for an electrochemical element according to claim 1, wherein the porous layer has a thickness of 0.15 to 5 μm.

4. 2. The separator for an electrochemical element according to claim 1, wherein the nitrogen-containing aromatic resin comprises an aramid resin.

5. A polyolefin porous substrate is provided, The separator for an electrochemical element according to claim 1 , wherein the porous layer is laminated on a polyolefin porous substrate.

6. The separator for an electrochemical element according to claim 5, wherein the thickness of the separator is 5.5 to 45 μm.

7. The separator for an electrochemical element according to claim 5 , further comprising an adhesive layer in addition to the polyolefin porous substrate and the porous layer.

8. A member for an electrochemical device comprising a positive electrode, the separator for an electrochemical device according to any one of claims 1 to 7, and a negative electrode arranged in this order.

9. An electrochemical element comprising the separator for electrochemical elements according to any one of claims 1 to 7.

10. The electrochemical device according to claim 9 , which is a secondary battery or a capacitor.

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