KR20130026373A - Separator for attaching heat resistant insulating layer - Google Patents

Abstract

PURPOSE: A separator for attaching heat resistant insulating layer is provided to obtain ion conductivity by electrolyte as a medium, improving the adhesion between a porous substrate and the heat resistant insulating layer. CONSTITUTION: A separator(1) for attaching heat resistant insulating layer comprises a porous substrate(2), and a heat-insulating layer which comprises a heat-insulating particle and binder formed on one side of the porous substrate. The heat resistant insulating layer has a gradient towards the thickness direction. The porosity of a heat resistant insulating layer which is in the opposite side of the porous substrate is higher than the porosity of a heat resistant insulating layer(3,3') which is in the porous substrate. A high porosity in the heat insulating layer is 50-80% and a low porosity in the heat insulating layer is 40-60%.

Description

Separator with heat-resistant insulation layer {SEPARATOR FOR ATTACHING HEAT RESISTANT INSULATING LAYER}

The present invention relates to a separator with a heat resistant insulating layer.

Recently, in order to cope with global warming, a reduction in the amount of carbon dioxide is urgently desired. The automobile industry is expected to reduce carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and the development of electric devices such as motor-driven secondary batteries, which hold the key to their practical use, is actively being developed. It is done.

In particular, lithium ion secondary batteries, which are electric devices, are considered to be suitable for electric vehicles in view of their high energy density and high durability against repeated charging and discharging, and thus, they tend to further increase in capacity, and safety is becoming increasingly important.

BACKGROUND ART Lithium ion secondary batteries generally have a positive electrode coated with a positive electrode active material or the like on both sides of a positive electrode current collector, and a negative electrode coated with a negative electrode active material or the like on both sides of a negative electrode current collector through an electrolyte layer having an electrolyte solution or an electrolyte gel in the separator. Connected to each other and stored in the battery case.

As the separator, for example, many polyolefin microporous membranes having a thickness of about 20 to 30 µm are used. However, such polyolefin microporous membranes may have heat shrinkage due to an increase in battery temperature and a short circuit accompanying them.

Therefore, in order to suppress thermal contraction of a separator, the separator with a heat resistant insulating layer which laminated | stacked the heat resistant porous layer on the surface of a microporous film is developed. For example, Patent Literature 1 describes that such a separator is used in a wound lithium ion battery and heat shrinkage due to temperature increase in the battery is suppressed.

International Publication No. 2007/066768 Pamphlet

However, by providing the heat resistant insulating layer in the separator, ion conduction through the electrolyte is inhibited. In order to improve the ion conduction, it is conceivable to increase the porosity of the heat resistant insulating layer, but in this case, the adhesion between the porous substrate and the heat resistant insulating layer is lowered, and the heat resistant insulating layer may drop off during cell fabrication. have.

Accordingly, the present invention provides a means for improving the adhesion between the porous substrate of the separator with a heat resistant insulating layer and the heat resistant insulating layer, and ensuring ion conduction through the electrolyte while suppressing the drop of the heat resistant insulating layer during cell fabrication or the like. It aims to provide.

The present inventors earnestly studied in view of the said subject. As a result, in the heat resistant insulating layer of the separator with a heat resistant insulating layer, the porosity of the heat resistant insulating layer having an inclination of the porosity in the thickness direction and on the side opposite to the porous substrate is larger than the porosity of the heat resistant insulating layer on the porous substrate side. It has been found that the problem can be solved by making it large.

That is, this invention is equipped with the heat-resistant insulating layer containing a porous base material and the heat-resistant particle and binder formed in at least one surface of the said porous base, The said heat-resistant insulating layer has the inclination of the porosity in the thickness direction, The said porous base side The porosity of the heat resistant insulating layer on the side opposite to the porous substrate is larger than the porosity of the heat resistant insulating layer on the substrate.

According to the present invention, a means for improving the adhesion between the porous substrate of the separator with a heat resistant insulating layer and the heat resistant insulating layer and preventing the drop of the heat resistant insulating layer during cell fabrication or the like, while ensuring electrolyte-mediated ion conduction, Can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the outline of the separator with a heat resistant insulating layer which concerns on one Embodiment of this invention.
It is a schematic diagram which shows the outline of the separator with a heat resistant insulating layer which concerns on another embodiment of this invention.
3 is a cross-sectional schematic diagram schematically showing an outline of a flat-layer stacked non-bipolar lithium ion secondary battery as a typical embodiment of the present invention.
4 is a perspective view schematically showing the appearance of a flat-layer stacked non-bipolar lithium ion secondary battery which is a typical embodiment of the present invention.
It is a schematic diagram which shows the outline of the separator with a heat resistant insulating layer which concerns on another embodiment of this invention.
It is a schematic diagram which shows the outline of the separator with a heat resistant insulating layer which concerns on another embodiment of this invention.
It is a schematic diagram which shows the outline of the separator with a heat resistant insulating layer which concerns on another embodiment of this invention.

In one embodiment of the present invention, the separator with a heat resistant insulating layer includes a heat resistant insulating layer comprising a porous base and heat resistant particles and a binder formed on at least one surface of the porous base, wherein the heat resistant insulating layer is formed in a thickness direction. The porosity of the heat resistant insulating layer on the side opposite to the porous base is larger than the porosity of the heat resistant insulating layer on the porous base side with a slope of the porosity.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the separator with a heat resistant insulating layer of this embodiment, and the electrical device which uses this is demonstrated, referring drawings. However, the technical scope of the present invention should be determined based on the description of the claims, and is not limited only to the following forms. In addition, in description of drawing, the same code | symbol is attached | subjected to the same element, and the overlapping description is abbreviate | omitted. In addition, the dimension ratio of drawing is exaggerated on account of description, and may differ from an actual ratio.

[Separator with Heat-resistant Insulation Layer]

The cross-sectional schematic diagram which shows typically the separator with a heat resistant insulating layer (henceforth a separator only) which concerns on one Embodiment of this invention is shown in FIG. According to FIG. 1, in the separator 1 with the heat resistant insulating layer of the present embodiment, the first heat resistant insulating layers 3 and 3 ′ are formed on both surfaces of the porous substrate 2, and the first heat resistant insulating layers 3 and 3 are formed. The second heat resistant insulating layers 6 and 6 'having a larger porosity than the first heat resistant insulating layers 3 and 3' are formed on the surface of 3 '). The first heat resistant insulating layers 3 and 3 'and the second heat resistant insulating layers 6 and 6' are present between the porous substrate 2 and the positive electrode or the negative electrode, whereby redox reaction by electrode potential It is possible to protect the porous gas from decomposition by thermal reaction.

[Porous gas]

Although it does not restrict | limit especially as the porous base 2, For example, a resin porous base, a metal porous base, etc. can be used. Preferably, it is a resin porous substrate which is a porous sheet containing organic resin which absorbs and maintains electrolyte solution, a woven fabric, a nonwoven fabric, etc. More preferably, the porous sheet is a microporous membrane composed of a microporous polymer. As such a polymer, the laminated body which has the 3-layered structure of polyolefin, polyimide, aramid, or PP / PE / PP, such as polyethylene (PE) and polypropylene (PP), etc. are mentioned, for example. In particular, the polyolefin-based microporous membrane has a property of being chemically stable, and is preferable in that the reactivity with the electrolyte solution can be suppressed low.

Although the thickness of the said porous sheet differs according to a use, it cannot be prescribed | regulated uniquely, For example, in the use of the motor drive secondary battery of a vehicle, it is preferable that it is 4-60 micrometers in single layer or multilayer. It is preferable that the micropore diameter of the said porous sheet is at most 1 micrometer or less (usually a pore diameter of about 10 nm), and the porosity is 20 to 80%.

Although it does not specifically limit as said woven fabric or nonwoven fabric, For example, Polyester, such as polyethylene terephthalate (PET); Polyolefins such as PP and PE; Polyimide, aramid, etc. may be conventionally known. Although it does not restrict | limit especially as bulk density of a woven fabric or a nonwoven fabric, What is necessary is just to acquire sufficient battery characteristics with the impregnated electrolyte solution. As a porosity of a woven fabric or a nonwoven fabric, Preferably it is 40 to 90%, Especially preferably, it is 50 to 90%. Moreover, as thickness of a woven fabric or a nonwoven fabric, Preferably it is 5-200 micrometers, Especially preferably, it is 5-100 micrometers. If the thickness is 5 μm or more, the electrolyte retainability is good, and if it is 200 μm or less, the resistance hardly increases excessively.

Although it does not restrict | limit especially as a manufacturing method of the said resin porous gas, In the case of a polyolefin microporous membrane, for example, after melt | dissolving a polyolefin in solvents, such as paraffin, a liquid paraffin, paraffin oil, tetralin, ethylene glycol, glycerin, decalin, etc. It can manufacture by the method of extruding to a sheet form, removing a solvent, and performing uniaxial stretching or biaxial stretching.

[Heat-resistant insulating layer]

The first heat resistant insulating layer (low porosity resistant heat insulating layer) 3 and 3 'and the second heat resistant insulating layer (high porosity resistant heat insulating layer) 6 and 6' mainly include heat resistant particles and a binder. As a material of the said heat resistant particle | grain, it is preferable that it is high heat resistance, and melting | fusing point or a thermal softening point is 150 degreeC or more, Preferably it is 240 degreeC or more. By using such a material having high heat resistance, shrinkage of the separator can be effectively prevented even when the temperature inside the battery reaches around 200 ° C. As a result, the occurrence of a short between the electrodes of the battery can be prevented, so that a battery in which performance is less likely to be degraded even by the temperature rise can be produced.

The heat-resistant particles are preferably electrically chemically stable, chemically stable with respect to a solvent used in the preparation of an electrolyte solution or a heat resistant insulating layer, and hardly oxidized and reduced in the operating voltage range of the battery. Do. The heat-resistant particles may be organic particles or inorganic particles, but are preferably inorganic particles from the viewpoint of chemical stability and the like. In addition, the heat-resistant particles are preferably fine particles in terms of dispersibility, and fine particles having a primary particle diameter of 100 nm to 3 μm may be preferably used. The shape of the heat-resistant particles is not particularly limited, and may be a shape close to a spherical shape, or may be a plate shape, a rod shape, or a needle shape.

The inorganic particles (inorganic powder) having the melting point or the thermal softening point of 150 ° C. or higher are not particularly limited. For example, iron oxide (Fe _x O _y ), SiO ₂ , Al ₂ O ₃ , aluminosilicate (aluminosilicate), TiO Inorganic oxides such as ₂ , BaTiO ₂ and ZrO ₂ ; Inorganic nitrides such as aluminum nitride and silicon nitride; Poorly soluble ionic crystals such as calcium fluoride, barium fluoride and barium sulfate; Covalent bond crystals such as silicon and diamond; Clay such as montmorillonite; And the like. The inorganic oxide may be a material derived from mineral resources such as boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, mica, or an artificial material thereof. In addition, the inorganic particles are metal; Conductive oxides such as SnO ₂ and tin-indium oxide (ITO); Carbonaceous materials such as carbon black and graphite; The particle | grains which gave electrical insulation by coating the surface of the electroconductive material illustrated by etc. with the material which has electrical insulation, for example, the said inorganic oxide, etc. may be sufficient. Especially, since the particle | grains of an inorganic oxide can be apply | coated to the surface of a porous base easily as a water dispersion slurry, a separator can be manufactured by a simple method and it is suitable. Among the inorganic oxides, Al ₂ O ₃ , SiO ₂ and aluminosilicates (aluminosilicates) are particularly preferable.

Examples of the organic particles (organic powder) having the melting point or the thermal softening point of 150 ° C. or more include crosslinked polymethacrylate, crosslinked polystyrene, crosslinked polydivinylbenzene, styrene-divinylbenzene copolymer crosslinked product, polyimide, melamine resin, and phenol. Particles of organic resins such as various crosslinked polymer particles such as resins and benzoguanamine-formaldehyde condensates, and heat resistant polymer particles such as polysulfone, polyacrylonitrile, polyaramid, polyacetal, and thermoplastic polyimide can be exemplified. have. In addition, the organic resin (polymer) constituting these organic particles may be a mixture, modified material, derivative, copolymer (random copolymer, alternating copolymer, block copolymer, graft copolymer), crosslinked material ( In the case of the heat resistant polymer microparticles). Among them, from the viewpoint of industrial productivity and electrochemical stability, it is preferable to use particles of crosslinked polymethyl methacrylate and polyaramid as organic particles. Since the separator mainly containing resin can be produced by using the particle | grains of such an organic resin, a lightweight battery can be obtained as a whole.

In addition, only 1 type may be used for the heat-resistant particle | grains mentioned above, or may be used for it in combination of 2 or more type, and when using it in combination of 2 or more types, it is the case of the inorganic particle or organic particle as mentioned above, for example. The heat resistant particles selected from the group may be used separately for each heat resistant insulating layer or mixed in one layer.

Although it does not restrict | limit especially as said binder, For example, carboxymethyl cellulose (CMC), polyacrylonitrile, cellulose, hydroxyethyl cellulose, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, Polyvinylpyrrolidone, styrene-butadiene rubber (SBR), isoprene rubber, butadiene rubber, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), methyl acrylate, and the like can be used. have. You may use these individually or in combination of 2 or more types. Especially, it is preferable to use carboxymethyl cellulose (CMC), methyl acrylate, or polyvinylidene fluoride (PVdF).

The binder contributes to adhesion between the heat resistant particles and adhesion of the porous gas layer and the heat resistant insulating layer. Therefore, the binder is essential as a component of the heat resistant insulating layer. Although the addition amount of a binder is not specifically limited, Preferably it is 2-15 mass% with respect to 100 mass% of total mass of a heat resistant particle and a binder, More preferably, it is 2-10 mass%. When the addition amount of a binder is 2 mass% or more, it is preferable at the point which the mechanical strength (peel strength etc.) of the separator with a heat resistant insulating layer becomes high, and vibration resistance improves. On the other hand, when the addition amount of a binder is 15 mass% or less, it is preferable at the point which adhesiveness can be suitably maintained and the possibility of inhibiting ion conductivity can be reduced.

The heat resistant insulating layer is not particularly limited, but may be formed of one layer or two or more layers. Even when the heat resistant insulating layer is formed of one layer, it is essential to have an inclination of the porosity in the thickness direction thereof.

Moreover, when the said heat resistant insulating layer is formed in two or more layers, it may consist of a layer containing any one or more different heat resistant particle | grains, such as a size, a shape, or a material, and may be made into the thickness direction of the heat resistant insulating layer which combined two or more layers. Any form can be employed as long as it has a slope of porosity.

The form having an inclination of the porosity in the thickness direction is not particularly limited, but the form in which the porosity is inclined in the thickness direction while having a constant gradient or the gradient is changed, and the layers having different porosities are laminated, and the porosity is gradated to form an overall thickness. It may also include a form having an inclination of the porosity in the direction, or a form having an inclined porosity in each layer constituting the heat-resistant insulating layer, or a gradient having a change in the overall thickness direction.

The inclination of the porosity is larger than the porosity of the heat resistant insulating layer on the porous substrate side, whereby the porosity of the heat resistant insulating layer on the side opposite to the porous substrate (the surface side of the separator) becomes larger, i.e., a portion having a high porosity on the surface side of the separator. It is configured to be inclined so that. In a laminated structure of two or more layers having different porosities, when the porosity is gradient and inclined, it is more preferable from the viewpoint of ease of manufacture and the like. In addition, when the said separator is used for a battery, the site | part on the said surface side is a site | part on an electrode side. In the battery, if the battery has the inclination as described above, the electrolyte may be inclined so that the amount of the electrolyte solution present between the heat-resistant particles increases toward the electrode, thereby promoting ion conduction through the electrolyte solution.

The porosity of the heat resistant insulating layer constituted using the heat resistant particles is not particularly limited, but the porosity of the high porosity portion is preferably 50 to 80%, more preferably 60 to 80%. Moreover, the porosity of a low porosity part becomes like this. Preferably it is 40 to 60%, More preferably, it is 40 to 55%. In the case of a heat resistant insulating layer formed of two layers having different porosities, the porosity of the layer having a high porosity is preferably 50 to 80%, more preferably 60 to 80%. Moreover, the porosity of the layer of low porosity becomes like this. Preferably it is 40 to 60%, More preferably, it is 40 to 55%. In addition, the porosity of the site | part (layer) of high porosity is larger than the porosity of the site | part (layer) of low porosity in any case. If the porosity of each layer is in the said range, mechanical strength will be maintained suitably and the output characteristic (rate characteristic etc.) can also be maintained high.

In addition, since the thickness of the said heat resistant insulating layer differs according to a use, it cannot be prescribed | regulated uniquely, The thickness of the whole heat resistant insulating layer located in each of the positive electrode side and the negative electrode side may be mutually same or different. In addition, when the heat resistant insulating layer on the positive electrode side or the negative electrode side is formed of two or more layers, the thickness of each layer may be the same or different, respectively. Although not particularly limited, when the heat resistant insulating layer is formed of two layers, the thickness of the high porosity layer on the positive electrode side is present in the range of 20 to 80% of the thickness of the entire heat resistant insulating layer on the positive electrode side. Preferably, it is 25 to 70% more preferably. On the other hand, it is preferable that the thickness of the high porosity layer on the negative electrode side exists in 20 to 80% of the thickness of the whole heat resistant insulating layer on the negative electrode side, More preferably, it is 30 to 75%. If the thickness of the layer of high porosity exists within the said range, mechanical strength will be maintained suitably, especially if the layer of high porosity is thicker than the layer of low porosity, the output characteristic can also be maintained high. In addition, since the ion conductivity on the negative electrode side particularly affects the output characteristics, it is particularly preferable to increase the thickness of the high porosity layer on the negative electrode side.

Although it does not restrict | limit especially as a total thickness of a separator, Usually, if it is about 5-50 micrometers, it can be used. In order to obtain a compact battery, it is preferable to make it as thin as possible in the range which can ensure the function as a separator, Preferably the total thickness of a separator is 30-50 micrometers, More preferably, it is 35-45 micrometers. If it is 30 micrometers or more, it can contribute to the improvement of battery output, and if it is 50 micrometers or less, it is suitable for use.

FIG. 2 is a schematic sectional view schematically showing a separator with a heat resistant insulating layer according to another embodiment of the present invention. According to FIG. 2, the separator 1 with a heat resistant insulating layer of this form is the 1st heat resistant insulating layers 3 and 3 which are the same material, size, shape, and thickness of heat resistant particle, respectively, on both surfaces of the porous base body 2, respectively. ') Is formed. In addition, a second heat resistant insulating layer 6 having a different porosity from the first heat resistant insulating layer 3 is formed on the surface of the first heat resistant insulating layer 3. The second heat resistant insulating layer 6 is preferably formed on the surface of the first heat resistant insulating layer 3 on the negative electrode side. The output characteristic can be made high by making the thickness of the high porosity layer on the negative electrode side thick.

The first heat resistant insulating layer (low porosity resistant heat insulating layer) 3 and 3 'and the second heat resistant insulating layer (high porosity resistant heat insulating layer) 6 are formed of the porous base 2 and the positive electrode or the negative electrode. By being therebetween, the porous gas can be protected from redox reaction by electrode potential or decomposition by thermal reaction. Since the decomposition by redox reaction or thermal reaction by the electrode potential at the negative electrode side is more severe than the decomposition by redox reaction or thermal reaction by the electrode potential at the positive electrode side, it is particularly preferable that the second heat resistant insulating layer is formed at least on the negative electrode side. Do. By being present at least on the negative electrode side, the ion conductivity can be maintained high.

The structure, form, etc. of the separator with a heat resistant insulating layer in this embodiment can use the thing mentioned above about embodiment shown in FIG.

[Electric device]

The separator with a heat resistant insulating layer of one embodiment of the present invention can be used for an electrical device. An electrical device, in particular a lithium ion secondary battery, comprising a separator with a heat-resistant insulating layer of one embodiment of the present invention between a positive electrode and a negative electrode is excellent for a driving power supply or an auxiliary power supply for a vehicle.

Moreover, since the lithium ion secondary battery which uses the separator with a heat resistant insulating layer of this embodiment is excellent also in cycle durability, it is preferable to use it for the drive power supply of a vehicle, portable devices, such as a mobile telephone.

The separator with a heat resistant insulating layer can be applied to, for example, a flat plate stacked type (flat type) battery. By adopting a flat plate laminated (flat type) battery structure, long-term reliability can be ensured by a sealing technique such as simple thermocompression bonding, which is advantageous in terms of cost and workability.

In addition, when seen from the electrical connection form (electrode structure) in a lithium ion secondary battery, it can apply to both a non-bipolar (internal parallel connection type) battery and a bipolar (internal series connection type) battery.

In the case of differentiating the type of electrolyte layer in the lithium ion secondary battery, the electrolyte layer may be used for a solution electrolyte type battery using a solution electrolyte such as a non-aqueous electrolyte solution as the electrolyte layer, and a gel electrolyte battery using a polymer gel electrolyte as the electrolyte layer. Can be applied.

In the following description, a non-dipolar type (internal parallel connection type) lithium ion secondary battery formed by using the above-described separator with a heat-resistant insulating layer will be briefly described with reference to the drawings. However, the technical scope of the present invention is not limited to these.

[Overall Structure of Battery]

Fig. 3 is a cross-sectional schematic diagram schematically showing the overall structure of a flat plate laminated (flat) lithium ion secondary battery (hereinafter, simply referred to as a "laminated battery"), which is a typical embodiment of the present invention.

As shown in FIG. 3, the stacked battery 10 of the present embodiment has a structure in which a substantially rectangular power generating element 21 in which the charge / discharge reaction actually proceeds is sealed inside a laminate sheet 29 that is an exterior body. . Here, the power generation element 21 includes a positive electrode in which the positive electrode active material layer 13 is disposed on both surfaces of the positive electrode current collector 11, an electrolyte layer 17 in which an electrolyte solution or an electrolyte gel is held in the separator, and a negative electrode current collector 12. ), The negative electrode having the negative electrode active material layer 15 disposed thereon is laminated. Specifically, the negative electrode, the electrolyte layer, and the positive electrode are stacked in this order so that one positive electrode active material layer 13 and the negative electrode active material layer 15 adjacent thereto face each other via the electrolyte layer 17.

As a result, the adjacent positive electrode, the electrolyte layer, and the negative electrode constitute one unit cell layer 19. Therefore, the stacked battery 10 shown in FIG. 3 can also be said to have a structure in which a plurality of unit cell layers 19 are stacked to be electrically connected in parallel. In addition, although the positive electrode active material layer 13 is arrange | positioned only to one side in the positive electrode electrical power collector of the outermost layer located in both outermost layers of the power generation element 21, the active material layer may be provided in both surfaces. In other words, the current collector having the active material layer on both sides may be used as the current collector of the outermost layer instead of the current collector for the outermost layer provided with the active material layer only on one side. 3, the arrangement of the positive electrode and the negative electrode is reversed so that the negative electrode current collector of the outermost layer is positioned on both outermost layers of the power generation element 21, and the negative electrode active material is disposed on at least one side of the negative electrode current collector of the outermost layer. The layers may be arranged.

The positive electrode current collector 11 and the negative electrode current collector 12 are each provided with a positive electrode current collector plate 25 and a negative electrode current collector plate 27, which are connected to each electrode (positive electrode and negative electrode), and are disposed between ends of the laminate sheet 29. It has a structure which is led out to the exterior of the laminate sheet 29 so that it may fit in the. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 are each ultrasonically applied to the positive electrode current collector 11 and the negative electrode current collector 12 of each electrode through a positive electrode lead and a negative electrode lead (not shown), respectively, as necessary. It may be provided by welding, resistance welding, or the like.

The lithium ion secondary battery described above is characterized by the separator. Hereinafter, the main structural members of the battery including the separator will be described.

[Active material layer]

The active material layer 13 or the active material layer 15 contains an active material and further contains other additives as necessary.

The positive electrode active material layer 13 contains a positive electrode active material. Examples of the positive electrode active material include a lithium-transition metal composite such as LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni-Co-Mn) O _2, and some of these transition metals substituted by another element. Oxides, lithium-transition metal phosphate compounds, lithium-transition metal sulfate compounds, and the like. In some cases, two or more kinds of positive electrode active materials may be used in combination. Preferably, in view of capacity and output characteristics, a lithium-transition metal composite oxide is used as the positive electrode active material. In addition, of course, positive electrode active materials other than the above may be used.

The negative electrode active material layer 15 contains a negative electrode active material. Examples of the negative electrode active material include carbon materials such as graphite (graphite), soft carbon, hard carbon, lithium-transition metal composite oxides (for example, Li ₄ Ti ₅ O ₁₂ ), metal materials, lithium alloy negative electrode materials, and the like. Can be mentioned. In some cases, two or more types of negative electrode active materials may be used in combination. Preferably, from the viewpoints of capacity and output characteristics, a carbon material or a lithium-transition metal composite oxide is used as the negative electrode active material. In addition, of course, the negative electrode active material of that excepting the above may be used.

Although the average particle diameter of each active material contained in each active material layer is not specifically limited, From a viewpoint of high output, Preferably it is 1-100 micrometers, More preferably, it is 1-20 micrometers.

Preferably, the positive electrode active material layer 13 and the negative electrode active material layer 15 include a binder.

Although it does not specifically limit as a binder used for an active material layer, For example, polyethylene, polypropylene, polyethylene terephthalate (PET), polyether nitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC) , Ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene butadiene rubber (SBR), isoprene rubber, butadiene rubber, ethylene propylene rubber, ethylene propylene diene copolymer, styrene butadiene styrene block copolymer and hydrogen thereof Thermoplastic polymers such as additives, styrene-isoprene-styrene block copolymers and hydrogenated additives thereof, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP) , Tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA), ethylene tere Fluorine resins such as polytetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene chlorotrifluoroethylene copolymer (ECTFE) and polyvinyl fluoride (PVF), vinylidene fluoride- (VDF-HFP fluorine rubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene fluororubber (VDF-HFP-TFE fluorine rubber), vinylidene fluoride-pentafluoro (VDF-PFP-based fluorine rubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluorine rubber (VDF-PFP-TFE based fluorine rubber), vinylidene fluoride-perfluoro Vinylidene fluoride such as methylvinylether-tetrafluoroethylene fluororubber (VDF-PFMVE-TFE fluororubber) and vinylidene fluoride-chlorotrifluoroethylene fluororubber (VDF-CTFE fluororubber) Droid type fluororubber, an epoxy resin, etc. are mentioned. Among these, polyvinylidene fluoride, polyimide, styrene-butadiene rubber, carboxymethylcellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile and polyamide are more preferable. These suitable binders are excellent in heat resistance, and have a very wide potential window, which is stable to both the positive electrode potential and the negative electrode potential, and thus can be used for the active material layer. These binders may be used independently and may use 2 or more types together.

Although the quantity of the binder contained in an active material layer will not be specifically limited if it is an quantity which can bind an active material, Preferably it is 0.5-15 mass% with respect to an active material layer, More preferably, it is 1-10 mass%.

Other additives that can be included in the active material layer include, for example, a conductive auxiliary agent, an electrolyte, and an ion conductive polymer.

The conductive auxiliary agent means an additive compounded to improve the conductivity of the positive electrode active material layer or the negative electrode active material layer. As the conductive auxiliary agent, carbon materials such as carbon black such as acetylene black, graphite, and carbon fiber can be mentioned. When the active material layer contains a conductive aid, the electronic network in the inside of the active material layer is effectively formed, which can contribute to the improvement of the output characteristics of the battery.

Examples of the electrolyte salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ and LiCF ₃ SO ₃ .

As an ion conductive polymer, the polymer of a polyethylene oxide (PEO) system and a polypropylene oxide (PPO) system is mentioned, for example.

The mixing ratio of the components contained in the positive electrode active material layer and the negative electrode active material layer is not particularly limited. The compounding ratio can be adjusted by appropriately referring to known knowledge about nonaqueous electrolyte secondary batteries. There is no restriction | limiting in particular also about the thickness of each active material layer, The conventionally well-known knowledge about a battery can be referred suitably. For example, the thickness of each active material layer is about 2-100 micrometers.

[Whole house]

The current collectors 11 and 12 are made of a conductive material. The size of the current collector is determined by the use of the battery. For example, a current collector having a large area is used as long as it is used for a large battery requiring high energy density. The lithium ion battery of the present embodiment is preferably a large battery, and the size of the current collector used is, for example, a long side of 100 mm or more, preferably 100 mm x 100 mm or more, more preferably 200 mm x 200 mm. That's it. The thickness of the current collector is not particularly limited. The thickness of an electrical power collector is about 1-100 micrometers normally. The shape of the current collector is not particularly limited either. In the stacked battery 10 shown in FIG. 3, in addition to the current collector foil, a mesh shape (such as an expanded grid) or the like can be used.

The material constituting the current collector is not particularly limited, but preferably a metal may be employed. Specific examples include aluminum, nickel, iron, stainless steel, titanium, and copper. In addition to these, a cladding material of nickel and aluminum, a cladding material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Moreover, the foil in which aluminum is coat | covered on the metal surface may be sufficient. Among them, aluminum, stainless steel and copper are preferable from the viewpoints of electronic conductivity and battery operating potential.

[Electrolyte Layer]

The electrolyte layer 17 has a structure in which an electrolyte is held at the center of the surface direction of the separator of this embodiment as a substrate. By using the separator of the present embodiment, a highly reliable battery can be stably manufactured.

[Manufacturing method]

Although the manufacturing method of the separator of this embodiment is not specifically limited, For example, after apply | coating the composition for slurry heat-resistant insulation layer formation containing the heat resistant particle whose melting | fusing point or heat softening point is 150 degreeC or more on both surfaces of a porous base material, Drying may be used.

The composition for forming a heat resistant insulating layer is obtained by dispersing heat resistant particles in a solvent and includes a binder and the like. As a binder for improving the shape stability of a heat resistant insulating layer, what is selected from the group mentioned above can be used. The amount of the binder contained in the heat resistant insulating layer is preferably 2 to 15% by mass or less, and more preferably 2 to 10% by mass or less based on the total mass of the heat resistant particles and the binder.

The solvent is not particularly limited as long as the heat-resistant particles can be uniformly dispersed. Examples of the solvent include water, aromatic hydrocarbons such as toluene, furan such as tetrahydrofuran, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and N. -Methylpyrrolidone (NMP), dimethylacetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), etc. are mentioned. Ethylene glycol, propylene glycol, monomethyl acetate, etc. may be added to these solvents suitably for the purpose of controlling interfacial tension. Particularly when inorganic oxide particles are used as the heat resistant particles, a heat resistant insulating layer can be easily manufactured by preparing a water dispersion slurry using water as a solvent. Moreover, it is preferable to manufacture the composition for heat-resistant insulating layer formation at 30-60 mass% of solid content concentration.

Although the weight per unit area at the time of apply | coating the composition for heat-resistant insulating layer formation to the said porous base material is not restrict | limited, Preferably it is 5-20 g / m <^2> , More preferably, it is 9-13 g / m <^2> . If it is the said range, the heat resistant insulating layer which has a suitable porosity and thickness can be obtained. There is no restriction | limiting in particular in the coating method, For example, the knife coater method, the gravure coater method, the screen printing method, the Meyer bar method, the die coater method, the reverse roll coater method, the inkjet method, the spray method, the roll coater method, the doctor blade method, etc. Can be mentioned.

The method for drying the applied composition for forming a heat-resistant insulating layer is not particularly limited, and for example, a method such as hot-air drying may be used. The drying temperature is, for example, 30 to 80 占 폚, and the drying time is, for example, 2 seconds to 50 hours.

The electrolyte layer is not particularly limited as long as it is formed using the separator of the present embodiment, and an electrolyte solution-containing separator having excellent ion conductivity can be used as the electrolyte layer depending on the purpose of use thereof, and a polymer gel electrolyte or the like can be used. The electrolyte layer formed by impregnating, apply | coating, spraying, etc. to a separator can also be used suitably.

(a) Electrolyte containing separator

As an electrolyte solution which can be permeated into the separator of this embodiment, at least one of LiClO ₄ , LiAsF ₆ , LiPF ₅ , LiBOB, LiCF ₃ SO _3, and Li (CF ₃ SO ₂ ) ₂ is used as the electrolyte, and ethylene is used as the solvent. Carbonate (EC), propylene carbonate, diethyl carbonate (DEC), dimethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydro The concentration of the electrolyte is adjusted to 0.5 to 2 M by dissolving the electrolyte in the solvent using at least one kind from ethers consisting of furan, 1,3-dioxolane and γ-butyrolactone. Should not be limited to them at all.

The amount of the electrolyte solution held by the separator by impregnation or the like may be impregnated, applied, or the like to the range of the separator's retention capacity, but may be impregnated beyond the range of the retention range. For example, in the case of a bipolar battery, resin can be injected into the electrolyte seal portion to prevent leakage of the electrolyte solution from the electrolyte layer, so that it can be impregnated as long as it can be held in the separator of the electrolyte layer. Similarly, in the case of the non-bipolar battery, since the battery element can be enclosed in the battery packaging material to prevent leakage of the electrolyte solution from inside the battery packaging material, it can be impregnated as long as it can be held in the battery packaging material. The electrolyte solution can be impregnated with the separator by a conventionally known method, such as after pouring with a vacuum injection method or the like, and then completely sealing.

(b) The gel electrolyte layer

In the gel electrolyte layer of the present invention, the separator of the present embodiment is held by impregnation, coating, or the like.

The gel electrolyte has a structure in which the liquid electrolyte (electrolyte solution) is injected into a matrix polymer made of an ion conductive polymer. As an ion conductive polymer used as a matrix polymer, polyethylene oxide (PEO), polypropylene oxide (PPO), these copolymers, etc. are mentioned, for example. In such a polyalkylene oxide polymer, electrolyte salts such as lithium salts can be dissolved well.

The ratio of the liquid electrolyte (electrolyte solution) in the gel electrolyte is not particularly limited, but from the viewpoint of ionic conductivity or the like, it is preferable to set it to several mass% to 98 mass%. In this embodiment, it is especially effective with respect to the gel electrolyte with many electrolyte solutions whose ratio of electrolyte solution is 70 mass% or more.

The matrix polymer of the gel electrolyte can express excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, a suitable polymerization initiator is used to polymerize polymerizable polymers for forming a polymer electrolyte (for example, PEO or PPO) such as thermal polymerization, ultraviolet polymerization, radiation polymerization, and electron beam polymerization. Do it.

The thickness of the electrolyte layer is not particularly limited, but is basically about the same as or slightly thicker than the thickness of the separator of the present embodiment, and can be used if it is usually about 5 to 30 μm.

Moreover, in this invention, the electrolyte of the said electrolyte layer may contain the various conventionally well-known additive as long as it is in the range which does not impair the effect of this invention.

Current collector and lead

A current collector plate (electrode tab) may be used for the purpose of drawing current out of the battery. The current collector plate (electrode tab) is electrically connected to the current collector or the lead, and is taken out of the laminate sheet as the battery exterior material.

The material constituting the current collector plate is not particularly limited, and a known highly conductive material conventionally used as the current collector plate for a lithium ion secondary battery can be used. As a constituent material of the current collecting plate, for example, a metal material such as aluminum, copper, titanium, nickel, stainless steel (SUS) or an alloy thereof is preferable, and more preferably, aluminum, Copper and the like are preferable. In addition, the same material may be used for the positive electrode collector plate and the negative electrode collector plate, and different materials may be used.

The positive terminal lead and the negative terminal lead are also used as necessary. As a material for the positive electrode terminal lead and the negative electrode terminal lead, a terminal lead used in a known lithium ion secondary battery can be used. In addition, the portion taken out from the battery packaging material 29 is covered with a heat-shrinkable heat-shrinkable tube or the like so as not to contact the peripheral device or the wiring or the like and short-circuit the product (for example, automobile parts, especially electronic devices, etc.). It is preferable.

[Battery exterior material]

As the battery packaging material 29, not only a known metal can case can be used, but also a bag-shaped case using a laminate film containing aluminum that can cover the power generating element can be used. Although the laminated film etc. which consist of laminated | stacked PP, aluminum, and nylon in this order can be used for the said laminated film, For example, there is no limitation in these. A laminate film is preferable from the viewpoint of high output power and excellent cooling performance and suitably used in a battery for large equipment for EV and HEV.

Moreover, the said lithium ion secondary battery can be manufactured by a conventionally well-known manufacturing method.

[Outline structure of lithium ion secondary battery]

4 is a perspective view showing an appearance of a flat plate stacked lithium ion secondary battery.

As shown in FIG. 4, the flat plate-type lithium ion secondary battery 10 has a flat shape having a rectangular shape, and the positive electrode current collector plate 25 and the negative electrode current collector plate 27 for taking out electric power from both sides thereof are provided. It is withdrawn. The power generation element 21 is wrapped by the battery packaging material 29 of the lithium ion secondary battery 10, the surroundings are heat-sealed, and the power generation element 21 is the positive electrode current collector plate 25 and the negative electrode current collector plate 27. ) Is sealed in the state where it is drawn out. Here, the power generation element 21 corresponds to the power generation element 21 of the lithium ion secondary battery 10 shown in FIG. 3. The power generation element 21 is formed by stacking a plurality of unit cell layers (single cells) 19 composed of a positive electrode (positive electrode active material layer) 13, an electrolyte layer 17, and a negative electrode (negative electrode active material layer) 15.

Further, the extraction of the current collector plates 25 and 27 shown in FIG. 4 is not particularly limited. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 may be taken out from the same side, or the positive electrode current collector plate 25 and the negative electrode current collector plate 27 may be divided into a plurality of portions, and may be taken out from each side. It is not limited to what is shown in FIG.

In addition, although the lithium ion secondary battery was illustrated as an electrical device in the said embodiment, it is not limited to this, It can apply to another type of secondary battery and also a primary battery. In addition, the present invention can be applied not only to batteries but also to capacitors.

<Examples>

Hereinafter, the present invention will be described in detail based on examples. In addition, the technical scope of this invention is not limited only to these Examples.

The average primary particle diameter in the Example of this invention was measured by the laser diffraction scattering method using the micro track particle size distribution measuring apparatus (model HRA9320-X100) of Nikkiso Corporation, The particle diameter computed by volume reference | standard. to be.

(Example 1)

<Positive electrode>

LiMn ₂ O ₄ (85% by mass) as a positive electrode active material, acetylene black (5% by mass) as a conductive aid, and PVdF (10% by mass) as a binder were dispersed in NMP (equivalent amount) as a slurry viscosity adjustment solvent to prepare a positive electrode slurry. It was. Subsequently, the positive electrode slurry was applied to one side of the aluminum current collector foil, and dried to form a positive electrode. It pressed so that the thickness of the single side | surface of a positive electrode might be 60 micrometers.

<Negative electrode>

Hard carbon (90 mass%) as a negative electrode active material and PVdF (10 mass%) as a binder were dispersed in NMP (suitable amount) which is a slurry viscosity adjustment solvent, and the negative electrode slurry was produced. Subsequently, the negative electrode slurry was applied to one surface of the copper current collector foil, and dried to form a negative electrode. It pressed so that the thickness of the single side | surface of a negative electrode may be 50 micrometers.

<Home>

As the current collector, aluminum foil (20 μm thick) was used as the positive electrode, and copper foil (20 μm thick) was used as the negative electrode. In addition, the electrode size was cut to 100 × 100 mm.

<Electrolyte>

1 M of LiPF ₆ / EC + DEC (solvent volume ratio 1: 1) was used as the electrolyte.

<Separator>

A polyethylene (PE) microporous membrane (film thickness of 15 µm, porosity 50%), which is a resin porous substrate, was used as the substrate.

The low porosity layer of the heat resistant insulating layer (first heat resistant insulating layer; 1-1 and 2-1 (base side) in the following table) is composed of alumina particles having an average primary particle diameter of 1 μm, a PVdF binder, and NMP. After apply | coating a slurry to the both sides of a base material by the doctor blade system, it was made by drying by hot air (film thickness of 5 micrometers, porosity 50%).

The high porosity layer (second heat resistant insulating layer; 1-2 and 2-2 (electrode side) in the following table) of the heat resistant insulating layer is alumina particles having an average primary particle diameter of 0.5 μm, PVdF binder, and NMP. The slurry thus formed was coated on the low porosity layers 1-1 and 2-1 by the doctor blade method, followed by hot air drying (film thickness 10 μm, porosity 70%).

Next, the heat-resistant insulating layers 1-1 and 1-2 face the positive electrode side, and the heat-resistant insulating layers 2-1 and 2-2 face the negative electrode side. It sealed with the laminated exterior body and produced the battery.

The schematic diagram of the separator with a heat resistant insulating layer is shown in FIG.

(Example 2)

A separator was produced in the same manner as in Example 1 except that the layer having a low porosity had a thickness of 10 μm and the layer having a high porosity had a thickness of 5 μm.

The schematic diagram of the separator with a said heat resistant insulating layer is shown in FIG.

(Example 3)

The low porosity layer was made 15 mu m thick, the low porosity layer was made 10 mu m thick, and the high porosity layer was made 10 mu m thick without producing a high porosity layer on the positive electrode side. A separator was produced in the same manner as in Example 1.

The schematic diagram of the separator with a heat resistant insulating layer is shown in FIG.

(Example 4)

It is carried out except that the low porosity layer on the positive electrode side has a film thickness of 10 μm and the high porosity layer has a film thickness of 5 μm, and the low porosity layer on the negative electrode side has a film thickness of 5 μm and the high porosity layer has a film thickness of 10 μm. A separator was produced in the same manner as in Example 1.

The schematic diagram of the separator with a heat resistant insulating layer is shown in FIG.

(Example 5)

It is implemented except that the low porosity layer on the positive electrode side has a film thickness of 10 μm and the high porosity layer has a film thickness of 5 μm, and the low porosity layer on the negative electrode side has a film thickness of 5 μm and the high porosity layer has a film thickness of 15 μm. A separator was produced in the same manner as in Example 1.

The schematic diagram of the separator with a heat resistant insulating layer is shown in FIG.

(Comparative Example 1)

A separator was produced in the same manner as in Example 1 except that the high porosity layer was 15 μm in thickness without producing a high porosity layer on both surfaces of the porous substrate.

(Comparative Example 2)

A separator was produced in the same manner as in Example 1 except that a low porosity layer was formed on both surfaces of the porous substrate, and the high porosity layer was 15 μm in thickness.

As mentioned above, the film thickness and porosity of each heat resistant insulating layer are shown in following Table 1 and Table 2.

In the method for obtaining the porosity, the porosity of each layer can be used by using Equation 1 below, and when the porosity exists in a plurality of layers, a value obtained by using the following Equation 2 can be used. Where B _i is the porosity of each layer, C is the average of the porosities of the entire heat-resistant insulating layer, W _i is the weight composition ratio (wt%) of each material in the layer, and d _i is the true density of each material in the layer. , A _i represents the actual density in the layer, t _i represents the thickness of each layer.

Here, in the formula (1), the ratio of the volume per unit mass of all the materials included in each layer of the heat resistant insulating layer can be obtained by [(1 / A _i ) / Σ (W _i / d _i )] , The porosity of the heat resistant insulating layer can be obtained by the equation (1).

In Equation 2, the ratio of the thicknesses of the respective layers of the heat resistant insulating layer to the thickness of the entire heat resistant insulating layer can be obtained by [(t _i / Σt _i )], and the porosity B _i of each layer is obtained. By taking the product of and, the ratio of the porosity of the layer i to the entire heat resistant insulating layer can be obtained. And the sum of the porosity of each obtained layer becomes the porosity of the whole heat resistant insulating layer.

[Battery evaluation]

The peeling strength of the separator with a heat resistant insulating layer produced in the said Examples 1-5 and Comparative Examples 1 and 2 was investigated. First, one side of the heat resistant insulating layer was reinforced with a cellophane tape (made by Nichido Co., Ltd.), and the heat resistant insulating layer was cut into a width of 10 mm. The heat resistant insulating layer after cutting was attached to the metal base with double-sided tape and fixed. Then, 10 mm of cellophane tapes were peeled off, and it installed in the measuring machine (STA-1150; Orientec Co., Ltd.), and peeling strength was measured on condition of 100 mm / min of tensile speed and 80 mm of peeling distances. The strength ratio with respect to the peeling strength of the separator produced by the comparative example 1 is shown in Table 3 below.

Moreover, the battery using the separator with a heat resistant insulating layer produced in Examples 1-5 and Comparative Examples 1 and 2 was produced, and the rate characteristic was investigated. The rate characteristics are shown in Table 3 below. Here, the rate characteristic is 0.2C when the initial charge discharge (the upper limit voltage of each layer 4.2V) and the gas discharge are performed at 0.5C for 5 hours, and the battery is discharged at 0.2C and 2C, respectively, after being fully charged. Is the ratio of the dose at 2C to the dose at.

The separator produced in Examples 1 to 5 exhibited high peel strength with respect to the separator according to Comparative Example 2. From this point of view, it was found that a separator including a layer having a low porosity can exhibit high peel strength with respect to a separator produced only with a layer having a high porosity.

Moreover, the battery using the separator produced in Examples 1-5 showed the high rate characteristic with respect to the battery which consists of the separator which concerns on the comparative example 1. In this respect, it can be seen that a battery made of a separator including a layer having a high porosity can exhibit high rate characteristics with respect to a battery made of a separator made of only a low porosity layer.

The separator produced in Example 2 showed higher peel strength than the separator produced in Example 1. On the other hand, the battery using the separator produced in Example 2 showed a lower rate characteristic than the battery using the separator produced in Example 1. From this point, it was found that by adjusting the thickness of the layer having a low porosity and the thickness of the layer having a high porosity, one having desirable characteristics with respect to the rate characteristic of the battery and the peeling strength of the separator can be produced.

The separator produced in Example 3 exhibited slightly lower peel strength than the separator produced in Comparative Example 1, and exhibited the same peel strength as the separators produced in Examples 1 and 2. On the other hand, the battery using the separator produced in Example 3 exhibited higher rate characteristics than the battery using the separator produced in Comparative Example 1, and exhibited the same rate characteristics as those of the batteries using the separators prepared in Examples 1 and 2. Indicated.

The separator produced in Example 4 exhibited the same peel strength as the separator produced in Example 1 or Example 2. On the other hand, although the rate characteristics were the same as the battery using the separator produced in Example 4 and the battery using the separator produced in Example 1, the rate characteristic was lower than the separator produced in Example 2.

The separator produced in Example 5 exhibited a slightly lower peel strength than the separator produced in Example 2, but exhibited the same peel strength as the separator produced in Example 4. In addition, the rate characteristic of the battery using the separator produced in Example 5 and the battery using the separator produced in Example 2 or Example 4 was about the same. In this respect, it was found that the structure of the heat resistant insulating layer on the negative electrode side had a greater effect on the rate characteristics of the battery and the peeling strength of the separator than the structure of the heat resistant insulating layer on the positive electrode side.

1: Separator (Separator) with Heat-resistant Insulation Layer
2: porous gas
3, 3 ': first heat resistant insulating layer
6, 6 ': second heat resistant insulating layer
10: lithium ion secondary battery (laminated battery)
11: positive electrode current collector
12: negative current collector
13: Positive electrode active material layer
15: negative electrode active material layer
17: electrolyte layer
19: single cell layer
21: development factors
25: positive electrode current collector
27: negative electrode current collector
29: battery exterior material (laminate film)

Claims (9)

With a porous gas,
And a heat resistant insulating layer comprising heat resistant particles and a binder formed on at least one surface of the porous substrate,
The heat resistant insulating layer has an inclination of the porosity in the thickness direction, and the porosity of the heat resistant insulating layer on the side opposite to the porous substrate is larger than the porosity of the heat resistant insulating layer on the porous substrate side. Separator. The portion of the high porosity in the heat-resistant insulating layer has a porosity of 50 to 80%, and the portion of the porosity lower than the portion of the high porosity has a porosity of 40 to 60%. Separator with insulation layer. The separator with heat resistant insulating layer according to claim 1 or 2, wherein the heat resistant insulating layer has a laminated structure of two or more layers having different porosities. The separator with heat resistant insulating layer according to claim 3, wherein the heat resistant insulating layer is made of two layers having different porosities. The thickness of the high porosity layer in the said heat resistant insulating layer exists in 20 to 80% of the thickness of the whole heat resistant insulating layer, The separator with a heat resistant insulating layer of Claim 4 characterized by the above-mentioned. The high porosity layer in the heat resistant insulating layer is thicker than the low porosity layer, and the separator with a heat resistant insulating layer according to claim 4. The low porosity layer in the heat resistant insulating layer is thicker than the high porosity layer, and the separator with a heat resistant insulating layer according to claim 4. The electrical device with which the separator with a heat resistant insulating layer of Claim 1 or 2 is interposed between a positive electrode and a negative electrode. The electrical device according to claim 8, wherein a portion of the high porosity of the heat resistant insulating layer is formed at least on the negative electrode side.

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