JP2019093565A - Laminated porous film, separator for power storage device and power storage device - Google Patents

Abstract

To provide a laminated porous film that can suppress the occurrence of warpage and shows excellent battery characteristics.SOLUTION: A laminated porous film has a heat-resistant porous layer containing tabular inorganic particles placed on at least one side of a polyolefin microporous film. The inorganic particle has a major axis of 4 μm or more.SELECTED DRAWING: None

Description

  The present invention relates to a laminated porous film, a storage battery separator, and a storage battery.

  Heretofore, various porous films have been developed and used as filters, electrolytic membranes, separators of non-aqueous solvent type batteries, and the like.

  In the field of lithium ion secondary batteries, since various active materials having high reactivity are used, various safety devices are provided in the batteries or the devices used. In a lithium ion secondary battery, a separator that separates a positive electrode and a negative electrode as one means for preventing the occurrence of heat generation, ignition, or rupture accident of the battery due to a short circuit of an external circuit, overcharge or the like. Is being used. As such a separator, a microporous film made of polyolefin such as polyethylene and polypropylene is widely used. That is, the pores of the microporous polyolefin film such as polyethylene and polypropylene are blocked by heat generation at the time of abnormality, and the separator has a function to stop the battery reaction through the separator, and the shape as the separator It is required to have a function of maintaining and preventing direct contact between the positive electrode and the negative electrode.

  In particular, in the case of a large capacity lithium ion secondary battery whose demand has been increasing in recent years, if the internal short circuit occurs due to the large capacity, the location will generate heat and the internal short circuit is likely to expand. There is a strong demand for the development of high performance separators that can avoid common accidents. Furthermore, the separators of microporous films manufactured by stretching, which are widely used at present, do not always have sufficient film shape maintaining characteristics, and separators having excellent film shape maintaining characteristics even at high temperatures are required.

Various attempts have been made to solve the problems of the conventional polyolefin microporous film, and one of them is to form a heat-resistant porous layer containing plate-like inorganic particles as a main component on the polyolefin membrane. A battery separator whose heat resistance stability has been improved by causing the heat treatment is proposed as a separator which achieves both the function of closing the film hole at the time of abnormal heat generation and the film shape maintaining characteristic at high temperature (see Patent Document 1).
Specifically, Patent Document 1 discloses that, as a battery separator, by using a multilayer separator in which a heat-resistant porous layer containing plate-like inorganic particles as a main component is formed on a polyolefin film, polyolefin is generated by heat generation due to minute short circuit. Even when the resin melts, the heat-resistant porous layer has a large amount of plate-like inorganic particles, and these are densely present, so even if the resin porous film tries to shrink under high temperature, the heat-resistant porous layer It is disclosed that the shrinkage of the whole multilayer porous film can be suppressed by the collision of the plate-like inorganic particles with each other, and the blocking function and the film shape maintaining property at high temperature can be compatible.
In the multilayer separator disclosed in Patent Document 1, a heat resistant porous layer is formed by applying a composition for forming a heat resistant porous layer, such as a slurry, on one side of a polyolefin film. As a general method for forming a porous layer, melt extrusion method, phase separation method, solvent casting method, etc. may be mentioned. When a porous film is formed by these methods, the heat-resistant layer precipitates and solidifies. The volume shrinks because the density increases. Therefore, in single-sided coating, significant warping (curling) occurs in the multilayer separator in order to alleviate this shrinkage, so that the handling property when laminated with an electrode for use as a battery separator was not sufficiently satisfactory. . Furthermore, by newly forming a heat-resistant layer on the polyolefin film, for example, the air permeability of the separator and the wettability to the electrolytic solution may be changed, and as a result, the performance of the battery may be significantly reduced.

JP, 2009-76410, A

  This invention is made in view of the subject which the said prior art has, local heating tolerance is improved, generation | occurrence | production of curvature can be suppressed, and when it uses as a separator for electrical storage devices, an electrical storage device is favorable. An object of the present invention is to provide a laminated porous film capable of exhibiting performance, a storage battery separator, and a storage battery.

When the present inventors diligently studied in order to solve the above-mentioned subject, they found a means which can solve the subject and arrived at the present invention. That is, the present invention has the following features (1) to (11):
(1) A laminated porous film in which a heat-resistant porous layer containing inorganic particles formed in a plate shape is laminated on at least one surface of a polyolefin microporous film, wherein the major diameter of the inorganic particles is 4 μm or more. Laminated porous film.
(2) The heat-resistant porous layer is characterized in that through-holes for penetrating both the heat-resistant porous layer and the polyolefin microporous film are not formed when a terminal heated to 400 ° is abutted for 5 seconds. The laminated porous film according to (1).
(3) Thermal mechanical analysis (TMA), described in (1) or (2) in which the shrinkage in the MD direction is 0.8% or less when reaching 100 ° C. at a temperature rising rate of 3 ° C./min from 30 ° C. Laminated porous film.
(4) The heat-resistant porous layer is a rectangular piece cut out with a size of 100 mm in a side in the machine direction and 100 mm in a direction substantially orthogonal to the machine direction under an environment of a temperature of 23 ° C and a dew point of -40 ° C or less The laminated porous film according to (1) or (2), wherein the floating amount of the four corners or the four sides of the rectangular piece is 16 mm or less on both the front side and the back side when left standing for 1 hour with the upper surface facing up.
There are two patterns for placing the porous film with one side (front side) facing up or the other side (back side) up, but in both cases it is 16 mm or less .
(5) The laminated porous film according to any one of (2) to (4), wherein the rate of increase in Gurley value is 30% or less with respect to the polyolefin microporous film of the substrate.
(6) The laminated porous film according to any one of (1) to (5), wherein an aspect ratio to a thickness of the inorganic particles is 4.5 or more.
(7) The laminated porous film according to (6), wherein the inorganic particles are boehmite.
(8) The microporous polyolefin film has a thickness of 3 μm to 16 μm, the heat-resistant porous layer containing inorganic particles has a thickness of 1 μm to 15 μm, and the supported amount of inorganic particles is 2.0 mg / cm ² or less (4 The laminated porous film as described in 2.).
(9) A separator for a storage battery comprising the laminated porous film according to any one of (1) to (8).
(10) An electric storage device comprising the electric storage device separator according to (9), a positive electrode, and a negative electrode.
(11) The laminated porous film according to (7), wherein the rate of increase in Gurley value is 30% or less with respect to the microporous polyolefin film.

According to the laminated porous film characterized in that a porous layer containing plate-like inorganic particles is formed on the microporous polyolefin film of the present invention in a layer, a battery separator having excellent local heat resistance and improved heat stability. It is possible to improve the performance of the storage device.
Furthermore, the occurrence of warpage in the laminated porous film can be suppressed, and the handling property when laminated with an electrode can be improved for use as a separator for a storage battery.

It is a figure which shows the local heating tolerance evaluation method. It is a figure which shows the local heating tolerance evaluation method. It is a figure which shows the local heating tolerance evaluation method.

In the laminated porous film of the present invention, a heat-resistant porous layer containing inorganic particles formed in a plate shape (hereinafter sometimes referred to simply as "plate-like inorganic particles") is laminated on at least one surface of a polyolefin microporous film It is a film. The major diameter of the inorganic particle is 4 μm or more.
<Polyolefin microporous film>
As the polyolefin microporous film used in the present invention, among the polyolefin microporous films applied to conventional electric storage device separators, those having sufficient mechanical properties and ion permeability can be suitably used.

  When the laminated porous film of the present invention is used as a separator for an electric storage device, too high a temperature makes it difficult to ensure safety when an internal short circuit occurs, and too low a temperature range in a normal use range. The battery may lose its convenience because it may be non-porous. For this reason, the heat blocking temperature is set to 120 to 180 ° C., preferably 120 to 140 ° C., although it is set according to the battery characteristics and the use environment. Further, the battery separator of the present invention has a porous layer (heat-resistant layer) containing plate-like inorganic particles, but in order to maintain non-poration up to a high temperature, the polyolefin microporous film alone is not porous at 170 ° C. or higher It is preferable to have a chemical maintenance temperature.

  In order to satisfy such characteristics, the microporous polyolefin film constituting the present invention preferably has a melting point of 150 ° C. or higher, and may be a laminated polyolefin microporous film. In the case of the laminated polyolefin microporous film, it preferably has a layer of the polyolefin microporous film having a melting point of 150 ° C. or more and a layer of the polyolefin microporous film having a melting point in the range of 110 ° C. to 140 ° C.

  The polyolefin microporous film having a melting point of 150 ° C. or more includes polypropylene (PP), and the polyolefin microporous film having a melting point in the range of 110 ° C. to 140 ° C. includes polyethylene (PE). Preferably, it is a porous film laminated in the order of PP / PE / PP.

  Although depending on the type of battery used, the film thickness of the polyolefin microporous film is, for example, preferably 3 to 300 μm, more preferably 9 to 100 μm, and still more preferably 16 to 50 μm.

  In addition, the microporous polyolefin film needs to have an appropriate air permeability (gas permeation rate; measured as Gurley value), and the Gurley value is 10 to 1000 seconds, although it varies depending on the production conditions, the composition of the film, etc. It is preferably 100 cc, more preferably 10 to 800 seconds / 100 cc, and still more preferably 30 to 600 seconds / 100 cc. If the Gurley value is too high, the function when used as a battery separator is not sufficient, and there is a risk that reaction nonuniformity within the battery may increase, which is not preferable. On the other hand, if the Gurley value is too low, Li dendrite precipitates during charge and discharge of the battery, which increases the risk of causing troubles.

  When the laminated porous film of the present invention is used as a storage device separator, the filler, particles, coloring agent, plasticizer, lubricant, flame retardant, anti-aging agent, to the extent that the performance as the storage device separator is not impaired. And a resin additive represented by an antioxidant etc., an adhesive, and a reinforcing agent composed of plate-like inorganic particles.

  The method for producing the polyolefin microporous film used in the present invention is not particularly limited, and, for example, JP-A-7-307146 or JP-A-4-181651, JP-A-3-80923, JP-A-7-268118. It can manufacture with reference to the method as described in the gazette, Unexamined-Japanese-Patent No. 8-138643 grade | etc.,.

  For example, in the case of producing a microporous polyolefin film by a dry stretching method, a nucleating agent is added to the polymer as needed and melted, and a sheet is formed by an extrusion method etc. and subjected to heat treatment for crystallization, and then stretched. The crystal interface can be peeled off and opened.

  Further, as described later, a coating liquid containing plate-like inorganic particles is applied to at least one surface of the polyolefin microporous film in order to form a porous layer containing plate-like inorganic particles, but By performing surface treatment such as ultraviolet light treatment, corona discharge treatment and plasma discharge treatment of the microporous polyolefin film before coating, the wettability to the coating liquid can be controlled. These surface treatments are preferably performed only on the surface of the microporous polyolefin film from the viewpoint of homogeneous coating. If the effect of the treatment extends to the inside of the polyolefin microporous film, there is a possibility that the “piercing” in which the coating liquid penetrates into the inside of the film and slips off to the back surface is likely to occur.

<Heat-resistant porous layer containing inorganic particles formed in a plate shape>
The heat-resistant porous layer of the present invention (hereinafter sometimes referred to simply as "porous layer") contains the inorganic particles formed in a plate shape (or scale-like shape, the same applies hereinafter) to achieve local heat resistance. Secure. In the present specification, “local heat resistance” is heat resistance evaluated using the soldering iron test method shown in FIG. 1 and obtained by “local heat resistance coefficient” corresponding to the penetration pattern shown in FIG. It can be evaluated by the "corrected through aperture". Furthermore, by containing plate-like inorganic particles, the occurrence of warpage in the laminated porous film can be suppressed, and the handling property when laminated with an electrode can be improved for use as a separator for a storage battery. In the present specification, warpage in the laminated porous film is evaluated by the curling amount of the laminated porous film of the present invention having a size of 100 mm × 100 mm under the conditions of 23 ° C., 50% humidity, or the dew point −50 ° C. It is

The inorganic fine particles of the present invention preferably have electrical insulating properties, and specifically, inorganic oxides such as iron oxide, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), TiO ₂ , magnesia, boehmite, BaTiO _{2 and the} like Fine particles; inorganic nitride fine particles such as aluminum nitride and silicon nitride; poorly soluble ionic crystal fine particles such as calcium fluoride, barium fluoride and barium sulfate; covalent crystalline fine particles such as silicon and diamond; clay fine particles such as montmorillonite And the like. Here, the inorganic oxide fine particles may be fine particles of a mineral resource-derived substance such as boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine or mica, or a artificial substance thereof. Moreover, the inorganic compound which comprises these inorganic fine particles may be element-substituted, or may be formed into solid solution as needed, and also the said inorganic fine particles may be surface-treated. In addition, the inorganic fine particles can be used to electrically insulate the surface of a conductive material exemplified by metals, conductive oxides such as SnO ₂ , tin-indium oxide (ITO), carbon black, carbonaceous materials such as graphite, etc. The particle | grains which gave electrical insulation by coat | covering with the material (for example, said inorganic oxide etc.) which has these may be sufficient.

Preferred examples of the plate-like inorganic particles according to the present invention include montmorillonite, hectorite, nontronite, sauconite, saponite, smideite such as beidellite and stevensite, talc, alumina, boehmite, calcium carbonate, silica, montmorillonite, mica and vermiculite, More preferably, talc and mica are used.
As a plate-like inorganic particle used preferably, various commercial item is mentioned, For example, a ground product (TiO ₂ ) of “Sun Lovely” (SiO ₂ ) manufactured by Asahi Glass SITEK, “NST-B1” manufactured by Ishihara Sangyo Co., Plate-like barium sulfate “H series” manufactured by Sakai Chemical Industry Co., Ltd. “HL series”, “Micron white” manufactured by Hayashi Kasei Co., Ltd. (talc), “Bengel” manufactured by Hayashi Kasei Co., Ltd. (bentonite), “BMM” manufactured by Kawai Lime Co., Ltd. And “BMT” (boehmite), Kawai Lime Co., Ltd. “Serashur BMT-B” (alumina (Al ₂ O ₃ )), Kinseimatech “Seraph” (alumina), Kamogawa Mining Co., Ltd. “Sakawa Mica Z-20 (Serisite) etc. are available. Besides, SiO ₂ , Al ₂ O ₃ and ZrO can be prepared by the method disclosed in Japanese Patent Application Laid-Open No. 2003-206475. Kawai Lime "BMM" and "BMT" (boehmite) are preferred.

  The plate-like inorganic particles may be used alone or in combination of two or more.

The average particle diameter of the inorganic fine particles is defined, for example, as a number average particle diameter measured by dispersing the plate-like inorganic particles in a medium in which the plate-like inorganic particles are not dissolved using a laser scattering particle size distribution analyzer (for example, "LA-920" manufactured by HORIBA) can do.
It can also be calculated by image analysis from an observation image of a scanning electron microscope (SEM).

The shape of the inorganic particles can be analyzed, for example, from observation with a scanning electron microscope (SEM). Here, an example of the definition about the shape of inorganic particles is described.
Among the rectangular parallelepipeds circumscribing the inorganic particles, the longest side of the rectangular parallelepiped (the circumscribed rectangular parallelepiped) having the smallest volume is the long diameter L, the second longest side is the short diameter B, and the shortest side is the thickness T (B> T). The shape of the inorganic particles is defined by an aspect ratio (L / T, L / B). L / T is an aspect ratio to thickness, and L / B is an aspect ratio to short diameter. The plate-like inorganic particles are inorganic particles in which L / T is larger than 4 and L / B is smaller than 5.

  The major diameter (maximum length in the direction orthogonal to the thickness direction of the plate) of the plate-like inorganic particles used in the present invention is 4 μm or more. The thickness is preferably 4.5 μm or more, more preferably 5.5 μm or more, and still more preferably 8.0 μm or more. The major axis is preferably 0.5 to 3 times the minor axis, and more preferably 0.8 to 1.5 times. The major axis or minor axis of the plate-like or scale-like inorganic particles is preferably 20 μm or less, more preferably 15 μm or less, and still more preferably 12 μm or less.

  The aspect ratio to the thickness of the plate-like inorganic particles used in the present invention (the thickness direction length of the plate, that is, the short direction length of the particles) is preferably 6 or more, and more preferably 8 or more. The thickness of the plate-like or scale-like inorganic particles is, for example, 0.36 μm to 2.0 μm, or 0.4 μm to 1.0 μm.

  The aspect ratio of the plate-like inorganic particles used in the present invention is preferably 4.5 or more, more preferably 6 or more, and 10 or more, using the aspect ratio (L / T) to the thickness. Is more preferable, and 15 or more is particularly preferable. The aspect ratio of the plate-like inorganic particles used in the present invention is preferably 40 or less, more preferably 30 or less, and still more preferably 20 or less.

  The heat-resistant porous layer containing plate-like inorganic particles contains plate-like inorganic particles as a main component, but in the present specification, “containing as a main component” means the plate-like inorganic particles as a structure of a porous layer containing plate-like inorganic particles It means that 70% by volume or more is included in the total volume of the components. The amount of plate-like inorganic particles in the porous layer containing plate-like inorganic particles is preferably 80% by volume or more, and more preferably 90% by volume or more in the total volume of the components of the heat-resistant layer. By setting the plate-like inorganic particles in the porous layer containing the plate-like inorganic particles to a high content as described above, the thermal contraction of the whole multilayer porous membrane can be favorably suppressed.

  Further, in the heat-resistant porous layer containing plate-like inorganic particles, the plate-like inorganic particles containing as a main component are bound to each other, or in order to bind the porous layer containing plate-like inorganic particles and the polyolefin microporous film. It is preferable to contain an organic binder, and from such a viewpoint, the preferable upper limit of the amount of plate-like inorganic particles in the porous layer containing plate-like inorganic particles is, for example, the whole of the constituent components of the porous layer comprising plate-like inorganic particles The volume is 99% by volume. If the amount of plate-like inorganic particles in the porous layer containing plate-like inorganic particles is too small, for example, it is necessary to increase the amount of organic binder in the porous layer containing plate-like inorganic particles. In the porous layer containing the inorganic inorganic particles, the pores of the porous layer may be filled with the organic binder, for example, there is a risk of losing the function as a separator. The distance between the inorganic particles is too large, which may reduce the effect of suppressing the thermal contraction.

  As the organic binder used for the heat-resistant porous layer containing plate-like inorganic particles, the plate-like inorganic particles and the porous layer containing plate-like inorganic particles and the polyolefin microporous film can be adhered well, and they are electrochemically stable. When it is used for the separator for the secondary battery, it is not particularly limited as long as it is stable to the organic electrolyte. Specifically, ethylene-vinyl acetate copolymer (EVA, having 20 to 35 mol% of a structural unit derived from vinyl acetate), ethylene-acrylic acid copolymer such as ethylene-ethyl acrylate copolymer, fluorocarbon resin [Polyvinylidene fluoride (PVDF), etc.], fluorocarbon rubber, styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP) ), Poly (N-vinylacetamide), cross-linked acrylic resin, polyurethane, epoxy resin, polyimide and the like. These organic binders may be used alone or in combination of two or more.

  In addition, when using these organic binders, it is made to melt | dissolve in the medium (solvent) of the coating liquid (slurry etc.) which forms the porous layer containing plate-like inorganic particle, or it was made to disperse | distribute in a coating liquid. It may be used in the form of

  The coating liquid for forming the porous layer containing plate-like inorganic particles contains plate-like inorganic particles and, if necessary, an organic binder and the like, which are dispersed in a medium such as water or an organic solvent (the organic binder is dissolved in the medium And the like).

  The organic solvent used as the medium of the coating liquid is one that does not damage the polyolefin microporous film by dissolving or swelling the polyolefin microporous film, and when an organic binder is used. The organic binder is not particularly limited as long as it can uniformly dissolve the organic binder, but furans such as tetrahydrofuran (THF); ketones such as methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK); is there. The high boiling point organic solvent is applied to the microporous polyolefin film by applying a composition for forming a porous layer containing plate-like inorganic particles to the microporous polyolefin film and then removing the organic solvent by drying etc. It is not preferable because it may cause damage. In addition, add polyhydric alcohol (ethylene glycol, triethylene glycol, etc.), surfactant (linear alkyl benzene sulfonate, polyoxyethylene alkyl ether, polyoxyethyl alkyl phenyl ether, etc.) to these organic solvents as appropriate. It is also good.

  In addition, water can also be used as the medium of the coating liquid, and in this case also, alcohol (ethanol, alcohol having 6 or less carbon atoms such as isopropanol, etc.) or surfactant (for example, the organic solvent described above) And the like may be added to the composition for forming a porous layer containing plate-like inorganic particles.

  In the laminated porous film (separator for an electricity storage device) of the present invention, the thickness of the porous layer containing plate-like inorganic particles is not particularly limited, but preferably 0.5 μm to 50 μm, more preferably 1 μm to 20 μm. And more preferably 5 μm to 15 μm. If the porous layer containing the plate-like inorganic particles is too thin, the meltdown prevention effect is insufficient, and if too thick, there is a risk that defects such as cracks may occur in the heat-resistant layer when forming the separator into a roll shape Is not preferable because In addition, the porous layer containing plate-like inorganic particles is thick also from the fact that the injection amount of the electrolyte increases and it contributes to the increase of the battery manufacturing cost and the energy density per volume and weight of the battery decreases. It is not preferable that it is too much.

The standard deviation of the film thickness of the porous layer containing plate-like inorganic particles is preferably 1.4 μm or less, more preferably 1.2 μm or less, still more preferably 1.0 μm or less, and further preferably It is 0.8 μm or less.
In the separator for a storage battery device of the present invention, the thickness of the porous layer containing plate-like inorganic particles is not particularly limited, but is preferably 0.5 μm to 50 μm, more preferably 1 μm to 120 μm, still more preferably 5 μm to 15 μm.

In the laminated porous film of the present invention (separator for an electricity storage device), the supported amount of the plate-like inorganic particles is not particularly limited, preferably ^{0.2mg / cm 2 ~5mg / cm 2} , more preferably 0. a ^{4mg / cm 2 ~3mg / cm 2} , more preferably from ^{0.5mg / cm 2 ~2mg / cm 2} . When the loading amount of the plate-like inorganic particles is too small, the meltdown preventing effect is insufficient, and when too large, there is a risk that defects such as cracks may occur in the heat-resistant layer when forming the separator into a roll shape Unfavorably because it increases. In addition, the amount of the plate-like inorganic particles carried is too large also from the fact that the injection amount of the electrolytic solution increases to contribute to the increase of the battery manufacturing cost and the energy density per volume and weight of the battery decreases. Is not desirable.

<Method of producing laminated porous film>
The method for producing a laminated porous film (separator for an electricity storage device) of the present invention comprises the steps of providing the above-mentioned polyolefin microporous film, and the plate-like inorganic particles formed on one side or both sides of the polyolefin microporous film. The process of apply | coating the coating liquid contained as a component, The process of drying the applied coating liquid and forming the porous layer containing plate-like inorganic particle is included.

  As a method of applying the coating liquid on the polyolefin microporous film, usually, a conventional casting or coating method, for example, a roll coater, an air knife coater, a blade coater, a rod coater, a bar coater, a comma coater, a gravure coater, Examples thereof include methods using conventionally known coating devices such as a silk screen coater, a die coater, and a microgravure coater method. As a method of applying the coating liquid containing the plate-like inorganic particles of the present invention on the microporous polyolefin film, a constant orientation can be controlled while maintaining the shape of the plate-like inorganic particles, so continuous coating is performed. A continuous coating apparatus that can be used is preferred.

  By drying the coating liquid applied on one side or both sides of the polyolefin microporous film to remove the medium in the coating liquid, a porous layer containing plate-like inorganic particles is formed.

  The film thickness of the laminated porous film of the present invention (the total of the film thickness of the microporous polyolefin film and the film thickness of the porous layer containing plate-like inorganic particles) is not particularly limited, but 4 to 300 μm, preferably 9 to 100 μm. More preferably, it is 16 to 50 μm. If the film thickness is too thin, the meltdown prevention effect becomes insufficient and the short circuit suppression effect by Li dendrite also becomes insufficient. If the film thickness is too thick, it is preferable because the injection amount of the electrolyte increases when it is used as a battery separator, which contributes to an increase in battery manufacturing cost, and the energy density per volume and weight of the battery decreases. Absent.

  When the average film thickness of the microporous polyolefin film is a (μm) and the average film thickness of the porous layer containing plate-like inorganic particles is b (μm), the value of the film thickness ratio a / b is 1 or more and 20 It is preferable that it is the following, It is more preferable that it is 2 or more and 10 or less, It is more preferable that it is 3 or more and 10 or less.

  Although the Gurley value (air permeability) of the laminated porous film of the present invention is not particularly limited, it is 10 to 1000 seconds / 100 cc, preferably 10 to 800 seconds / 100 cc, and more preferably 30 to 600 seconds / 100 cc. If the Gurley value is too high, the function when used as a storage device separator is not sufficient, and if the Gurley value is too low, there is a risk that reaction nonuniformity inside the battery may increase, which is not preferable.

  In the present invention, the standard deviation of the Gurley value of the laminated porous film is preferably 12 seconds / 100 cc or less, more preferably 10 seconds / 100 cc or less.

  In the laminated porous film of the present invention, the heat blocking temperature is preferably 110 ° C. to 180 ° C. in order to secure the function as a storage device separator.

  Generally, in the case of a laminated porous film in which a coating layer is provided on a substrate, a load may be applied under specific temperature conditions in order to suppress warpage, but such treatment is not required in the present invention. ing. It is one of the features of the present invention to suppress the warpage of the laminated porous film without such treatment.

<Evaluation of laminated porous film (separator) provided with plate-like inorganic particle-containing porous layer>
It evaluates based on the evaluation method (measurement method of correction | amendment through-diameter) of the local heating tolerance mentioned later with respect to the produced said laminated porous film. When a terminal heated to 400 degrees is brought into contact with the heat-resistant porous layer for 5 seconds, it is preferable that a through-hole penetrating both the heat-resistant porous layer and the polyolefin microporous film is not formed. Furthermore, it is more preferable that through holes that pierce both the heat-resistant porous layer and the polyolefin microporous film are not formed when the terminal heated to 400 degrees is abutted for 10 seconds. Furthermore, it is more preferable that when the terminal heated to 400 degrees is abutted for 20 seconds, no through hole is formed to pierce both the heat resistant porous layer and the polyolefin microporous film.

  It evaluates based on the evaluation method of the heat-shrink behavior below mentioned with respect to the produced said laminated porous film. Thermal mechanical analysis (TMA) shows that the shrinkage in the MD direction is preferably 0.8% or less, and is 0.6% or less when reaching 100 ° C. at a heating rate of 3 ° C./min from 30 ° C. Is more preferably 0.5% or less, and particularly preferably 0.1% or less.

  The curl height of the laminated porous film in which the porous layer containing the plate-like inorganic particle produced above was formed is evaluated based on the measuring method of the curl height mentioned below. A rectangular piece cut out with a size of 100 mm in a side in the machine direction and 100 mm in a direction substantially orthogonal to the machine direction is placed on the heat resistant porous layer at the top under an environment of a temperature of 23 ° C. and a dew point of −40 ° C. The total floating amount, which is the sum of the floating amounts of the four sides or the four corners of the rectangular piece, is preferably 16 mm or less, more preferably 12 mm or less, and 7 mm or less when left for 1 hour. It is more preferable.

  The layer ratio of the heat-resistant porous layer to the microporous polyolefin membrane can be 1: 1 to 1:10, but the thickness of the heat-resistant porous layer is preferably 60% or less of that of the porous polyolefin film from the viewpoint of weight. % Or less is more preferable, and 45% or less is even more preferable. While reducing the battery weight by reducing the layer thickness of the heat resistant porous layer to 60% or less of the thickness of the polyolefin microporous film, the heat shrinkage resistance, heat resistance (resistance to soldering iron test), and curl (warpage) reduction are reduced. For example, in the case of a battery for vehicles, this weight reduction makes it possible to further increase the travel distance.

The microporous polyolefin membrane is not particularly limited, but one having excellent shape stability is preferable. In addition, it is preferable that the difference in shape stability between the heat-resistant porous layer and the microporous polyolefin membrane be small. For example, although the heat-resistant porous layer hardly thermally shrinks, the microporous polyolefin membrane heat-shrinks. Therefore, when the heat-resistant porous layer is provided on the microporous polyolefin film, a bending moment is generated to generate a curl. It is often the case.
In order to suppress this warp, it is desirable to perform at least one of the shape stability of the heat-resistant porous layer and the shape stability of the microporous polyolefin membrane. The present invention has been made from such a point of view, and provides a laminated porous film in which the shape stability such as the reduction of the thermal contraction rate and the prevention of the formation of through holes is further enhanced while reducing the warpage. .

  As described above, the structure of the microporous polyolefin membrane is not particularly limited, but preferably the zero shear viscosity at 200 ° C. is 1300 to 20000 Pa.s. It is preferable to use a microporous polyolefin having a layer composed of a polypropylene resin which is s. By using such a polypropylene resin, shape stability higher than before can be maintained even at 200 ° C. Above all, the symmetry in the film thickness direction is made favorable by using a polyolefin microporous film of a three-layer structure in which the layer made of the above polypropylene resin is used as the surface layer and the layer made of polyethylene resin is used as the middle layer. It is possible to provide a laminated porous film excellent in shape stability. In addition, the shutdown characteristic can be maintained without breaking the film up to at least 200 degrees or more. Therefore, it can be expected that the shutdown characteristics can be maintained unless the above-mentioned through hole is formed, and when the present invention is used as a storage device separator, it can contribute to safety.

  Although the heat resistance of the conventional laminated porous film provided with a heat-resistant porous layer on a polyolefin microporous film was not sufficient, in the present invention, a heat-resistant porous film having a thickness of 4 μm or more on a polyolefin microporous film having a thickness of 16 μm By providing a layer, not only heat shrinkage resistance and curl (warping) characteristics, but also heat resistance can be further enhanced. In particular, the heat resistance can be enhanced by making the film thickness of the heat resistant porous layer 5 μm more than 4 μm and 6 μm more than 5 μm. At this time, conventionally, when the film thickness of the heat-resistant porous layer is increased, the Gurley value of all layers including the heat-resistant porous layer and the layer of the microporous polyolefin film tends to be large. By forming the heat-resistant porous layer so that the layer weight of the layer becomes smaller, the influence on the Gurley value is suppressed as much as possible, thereby avoiding the deterioration of the battery performance. The Gurley value of the laminated porous film does not exceed 400 seconds and can be 380 seconds or less in the present invention, and the porosity and thickness of the microporous polyolefin film, the basis weight and porosity of the heat-resistant porous layer, Of course, it is also possible to make it 300 seconds or less by appropriately adjusting the film thickness and the like.

  Moreover, in the conventional laminated porous film, a tensioning step is required to suppress the amount of curling (warpage), but in the present invention, the amount of curling can be reduced even without the tensioning step. It is also one of the features that the productivity of the laminated porous film can be enhanced.

<Non-aqueous electrolyte>
Preferred examples of the non-aqueous solvent used in the non-aqueous electrolyte include cyclic carbonates and chain esters. In order to synergistically improve the electrochemical properties at a wide temperature range, particularly at high temperatures, it is preferable to include a chain ester, more preferably to include a chain carbonate, and to include both a cyclic carbonate and a chain carbonate. Most preferred. In addition, the term "linear ester" is used as a concept including linear carbonate and linear carboxylic acid ester.

  Examples of cyclic carbonates include one or more selected from ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC), and a combination of EC and VC, and a combination of PC and VC are particularly preferable.

  Moreover, when the non-aqueous solvent contains ethylene carbonate and / or propylene carbonate, the stability of the film formed on the electrode is increased and the high temperature, high voltage cycle characteristics are improved, which is preferable, and the inclusion of ethylene carbonate and / or propylene carbonate The amount is preferably 3% by volume or more, more preferably 5% by volume or more, still more preferably 7% by volume or more, and the upper limit thereof is preferably 45% by volume or less based on the total volume of the non-aqueous solvent. More preferably, it is 35 volume% or less, More preferably, it is 25 volume% or less.

  As the chain ester, methyl ethyl carbonate (MEC) as asymmetric chain carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC) as symmetric chain carbonate, ethyl acetate (hereinafter EA) as chain carboxylic acid ester Can be mentioned.

  The content of the linear ester is not particularly limited, but is preferably in the range of 60 to 90% by volume with respect to the total volume of the non-aqueous solvent. If the content is 60% by volume or more, the viscosity of the non-aqueous electrolyte does not become too high, and if it is 90% by volume or less, the electrical conductivity of the non-aqueous electrolyte decreases and a wide temperature range, particularly at high temperature The above range is preferable because there is little possibility that the electrochemical characteristics will be reduced.

  The ratio of the cyclic carbonate to the chain ester is preferably 10:90 to 45:55 for a cyclic carbonate: chain ester (volume ratio) from the viewpoint of improvement of the electrochemical properties at a wide temperature range, particularly at high temperatures, and 15:85. To 40:60 is more preferable, and 20:80 to 35:65 is particularly preferable.

<Electrolyte salt>
As an electrolyte salt contained in a non-aqueous electrolyte solution, a lithium salt is mentioned suitably.
The lithium salt is preferably one or more selected from the group consisting of LiPF ₆ , LiBF ₄ , LiN (SO ₂ F) ₂ and LiN (SO ₂ CF ₃ ) ₂ , and LiPF ₆ , LiBF ₄ and LiN ( One or more selected from SO ₂ F) ₂ is more preferable, and it is most preferable to use LiPF ₆ .

<Production of non-aqueous electrolyte>
Non-aqueous electrolyte solution is, for example, a method of mixing the above-mentioned non-aqueous solvent, and adding thereto a composition obtained by mixing the above-mentioned electrolyte salt and the non-aqueous electrolyte with a solubilizer etc. at a specific mixing ratio. It can be obtained by Under the present circumstances, it is preferable to refine | purify previously and use a thing with few impurities as much as possible within the range which does not reduce productivity significantly, using the non-aqueous solvent and the non-aqueous electrolyte to be used.

  The microporous polyolefin film of the present invention can be used in the following first and second electricity storage devices, and not only liquid ones but also gelled ones can be used as non-aqueous electrolytes. Above all, it is preferable to use as a separator for a lithium ion battery (first power storage device) using a lithium salt as an electrolyte salt or for a lithium ion capacitor (second power storage device), and more preferably for a lithium ion battery It is more preferable to use for lithium ion secondary batteries.

<Lithium ion secondary battery>
A lithium ion secondary battery as an electricity storage device according to the present invention has a positive electrode, a negative electrode, and the non-aqueous electrolytic solution in which an electrolyte salt is dissolved in a non-aqueous solvent. The constituent members such as the positive electrode and the negative electrode other than the non-aqueous electrolytic solution can be used without particular limitation.
For example, as a positive electrode active material for a lithium ion secondary battery, a composite metal oxide with lithium containing one or more selected from the group consisting of cobalt, manganese, and nickel is used. These positive electrode active materials can be used singly or in combination of two or more.

As such a lithium composite metal oxide, for example, LiCoO ₂ , LiCo _1-x MxO ₂ (where M is Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, and Cu) One or more elements to be selected: LiMn ₂ O ₄ , LiNiO ₂ , LiCo _1-x Ni _x O ₂ , LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _0.5 Mn _{0. 3 Co 0.2 Mn 0.3 O 2,} LiNi 0.8 Mn 0.1 Co 0.1 O 2, LiNi 0.8 Co 0.15 Al 0.05 O 2, Li 2 MnO 3 and LiMO ₂ ( M is preferably one or more selected from a solid solution with Co, Ni, Mn, transition metals such as Fe, and LiNi _1/2 Mn _3/2 O ₄ .

  The conductive agent of the positive electrode is not particularly limited as long as it is an electron conductive material which does not cause a chemical change. For example, one or more kinds of carbon black selected from natural graphite (scalate graphite etc.), graphite such as artificial graphite, acetylene black and the like can be mentioned.

  The positive electrode includes the above-mentioned positive electrode active material as a conductive agent such as acetylene black and carbon black, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), copolymer of styrene and butadiene (SBR), acrylonitrile and butadiene The mixture is mixed with a binder such as copolymer (NBR), carboxymethylcellulose (CMC), etc., and a solvent is added thereto and kneaded to make a positive electrode mixture, and then this positive electrode mixture is used as an aluminum foil or stainless steel of a current collector. The composition can be applied to a plate or the like, dried and pressed, and then heat-treated under predetermined conditions.

  The negative electrode active material for lithium ion secondary batteries is selected from lithium metal, lithium alloy, carbon material capable of absorbing and desorbing lithium, tin (single body), tin compound, silicon (single body), silicon compound, etc. Or two or more thereof may be used in combination.

  When graphite and silicon, or graphite and a silicon compound are used in combination as the negative electrode active material, when the content of silicon and silicon compound in all the negative electrode active material is 1 to 45% by mass, the lithium ion according to the present invention It is preferable because the capacity can be increased while suppressing the deterioration of the electrochemical characteristics of the secondary battery and the increase of the electrode thickness.

  The negative electrode is kneaded using the same conductive agent, binder and high boiling point solvent as in the preparation of the above positive electrode to form a negative electrode mixture, and this negative electrode mixture is then applied to copper foil of the current collector and the like. After drying and pressure molding, it can be produced by heat treatment under predetermined conditions.

  The structure of the lithium ion secondary battery is not particularly limited as one of the electricity storage devices of the present invention, and a coin cell, a cylindrical cell, a square cell, a laminate cell or the like can be applied.

  The wound-type lithium ion secondary battery has, for example, a configuration in which an electrode body is accommodated in a battery case together with a non-aqueous electrolyte. The electrode body is composed of a positive electrode, a negative electrode and a separator. At least a portion of the non-aqueous electrolyte is impregnated in the electrode body.

  The wound-type lithium ion secondary battery includes, as a positive electrode, a long sheet-like positive electrode current collector, and a positive electrode mixture layer containing a positive electrode active material and provided on the positive electrode current collector. As a negative electrode, a long sheet-like negative electrode current collector and a negative electrode mixture layer containing a negative electrode active material and provided on the negative electrode current collector are included.

  The separator of the present invention is formed into a long sheet by using the laminated porous film of the present invention, as in the case of the positive electrode and the negative electrode. The positive electrode and the negative electrode are cylindrically wound with a separator interposed therebetween. The shape of the electrode body after winding is not limited to a cylindrical shape. For example, after winding a positive electrode, a separator, and a negative electrode, you may form in flat shape by applying a pressure from the side.

  The battery case includes a bottomed cylindrical case body and a lid closing an opening of the case body. The lid and the case body are for example made of metal and are mutually insulated. The lid is electrically connected to the positive electrode current collector, and the case body is electrically connected to the negative electrode current collector. The lid may also serve as the positive electrode terminal, and the case body may also serve as the negative electrode terminal.

  The lithium ion secondary battery can be charged and discharged at −40 to 100 ° C., preferably −10 to 80 ° C. In addition, as a measure to increase the internal pressure of the wound lithium ion secondary battery, a method of providing a safety valve on the lid of the battery or cutting a member such as a battery case main body or a gasket may be employed. In addition, as a safety measure against overcharging, a lid may be provided with a current interrupting mechanism that senses the internal pressure of the battery and interrupts the current.

<Production of wound-type lithium ion secondary battery>
As an example, the manufacturing procedure of a lithium ion secondary battery will be described below.
First, a positive electrode, a negative electrode, and the separator of the present invention are produced. Next, the electrode body is assembled by overlapping them and winding in a cylindrical shape. Then, the electrode body is inserted into the case body, and the non-aqueous electrolyte is injected into the case body. Thus, the electrode body is impregnated with the non-aqueous electrolytic solution. After the non-aqueous electrolyte is injected into the case body, the case body is covered with a lid to seal the lid and the case body. The shape of the electrode body after winding is not limited to the cylindrical shape. For example, after winding a positive electrode, a separator, and a negative electrode, you may form in flat shape by applying a pressure from the side.

  The above lithium ion secondary battery can be used as a secondary battery for various applications. For example, it is mounted in vehicles, such as a car, and it can use suitably as a power supply for drive sources, such as a motor which drives a vehicle. The type of vehicle is not particularly limited, and examples thereof include hybrid vehicles, plug-in hybrid vehicles, electric vehicles, fuel cell vehicles and the like. Such lithium ion secondary batteries may be used alone, or may be used by connecting a plurality of batteries in series and / or in parallel.

<Laminated battery>
Although a wound lithium ion secondary battery has been described above, the present invention is not limited to this, and may be applied to a laminate lithium ion secondary battery.
For example, the positive or negative electrode is sandwiched and packaged by a pair of the separators of the present invention. For example, the positive electrode is a packaged electrode, and the separator is formed into a square having a size slightly larger than that of the electrode. While the main body of the electrode is sandwiched between the pair of separators, the tabs projecting from the electrode end are superposed so that the tabs protrude from the end of the separator. The side edges of the stacked pair of separators are joined together to form a bag, and one electrode and the other electrode packed in this separator are alternately laminated and impregnated with an electrolytic solution to produce a laminate type battery. can do. At this time, in order to reduce the thickness, these separators and electrodes may be compressed in the thickness direction.
It is preferable that the four corners of the square shaped separator be formed in a planar shape. For example, if one of the four corners of the separator is warped (curled), the curl must be returned to a planar shape, which degrades the yield of battery manufacture. Furthermore, if the degree of warpage is extremely large, the laminate type battery is formed in a state where the separator is bent, and a risk of internal short circuit occurs.
From the above viewpoint, the separator of the present invention is preferably planar. In the separator of the present invention, warpage (curling) of the separator is reduced or eliminated by forming grooves extending in the width direction (direction orthogonal to the machine direction) at predetermined intervals in the machine direction.

<Lithium ion capacitor>
A lithium ion capacitor is mentioned as another electricity storage device of the present invention, lithium ion to carbon materials such as graphite having the laminated porous film (separator) of the present invention, non-aqueous electrolyte, positive electrode and negative electrode and being a negative electrode. Energy can be stored using intercalation. Examples of the positive electrode include those using an electric double layer between an activated carbon electrode and an electrolytic solution, and those using a doping / dedoping reaction of a π-conjugated polymer electrode. The electrolyte includes lithium salts such as at least LiPF _6.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

  Each measuring method about the polyolefin fine porous film in the following example and a comparative example and the separator for electrical storage devices is as follows.

<1> Film Thickness and Supported Amount The film thickness was measured by a contact-type thickness meter (manufactured by Peacock).
The supported amount was calculated by calculating the weight per unit area of the inorganic particle layer from the weight difference between the polyolefin microporous film and the laminated porous film, and multiplying the ratio by the inorganic particles and the binder.
From the following formula (1), the supported amount per unit area of the inorganic particles was determined. The formula is as follows:
(Supported amount per unit area of inorganic particles) = {(weight of laminated porous film) − (weight of polyolefin microporous film)} ÷ (area of laminated porous film).

<2> Gurley Value Measured according to JIS P8117. As a measuring device, B-type Gurley densometer (made by Toyo Seiki Co., Ltd.) was used. The sample piece is tightened in a circular hole having a diameter of 28.6 mm and an area of 645 mm 2. The air in the cylinder is allowed to pass from the test circular hole to the outside of the cylinder by an inner cylinder weight of 567 g. The time taken for 100 cc of air to pass was measured and taken as the air permeability (Gurley value).

<3> Method of Measuring Curl Height of Laminated Porous Film (Separator for Storage Device) From the laminated porous film (separator) described in the Examples and Comparative Examples, this stretching is 100 mm in the stretching direction (machine direction, MD) The separator was cut in a size of 100 mm in the width direction (direction orthogonal to the mechanical method, TD) substantially perpendicular to the direction.
The cut separator is placed on a flat surface, and the porous layer containing plate-like inorganic particles is in the upper surface and the lower surface in two cases: the machine direction (MD direction) and the direction orthogonal to the machine direction (TD The height of the portion with the largest warpage was measured on each side of the direction), and the total of them was taken as the total floating amount. The above measurement was performed under an environment of a temperature of 23 ° C. and a humidity of 50%, and under an environment of a dew point of −45 ° C. at a temperature of 23 ° C.
The amount of curling is larger when the inorganic particle layer is provided on one side of the polyolefin microporous film, not on both sides. Therefore, when measuring the amount of curling, the inorganic particle layer is provided on one side of the polyolefin microporous film. A porous film was used.

<4> Evaluation Method of Shape (Aspect Ratio, Long Diameter) of Plate-like Inorganic Particles The inorganic particles are sparsely placed on a sample table, observed with a scanning electron microscope, and the long diameter and short diameter are measured from the image. did. This measurement was performed at 50 points or more each, and the aspect ratio was calculated with the average value as the average major axis and the average minor axis.

<5> Evaluation method of local heating tolerance (measurement of correction through aperture, soldering iron test)
The local heating tolerance evaluation method was performed under the following test conditions in the test apparatus shown in FIG. 1 to evaluate the local heating tolerance.
<Test conditions>
・ Soldering iron: RX-711AS (main body), PX-60RT-B (tip / end spherical φ 0.5 mm)
・ Sample fixing: Aluminum plate / aluminum foil / Sepa / SUS plate (opening φ 8 mm) from the bottom
・ Setting temperature: 400 ° C
Contact time: 5 seconds Speed: 300 mm / min Load: weight of soldering iron (about 50 g)
-Solder iron contact surface: particle layer side, base material (raw film) side-Evaluation number: N = 10

The evaluation procedure is as follows.
(1) As for the sample after the test, as shown in FIG.
(2) The through holes are classified into four through patterns as shown in FIG.
(3) Corrected through hole diameter = (through hole diameter × pattern coefficient) to obtain a corrected through hole diameter.
<6> Evaluation method of heat shrinkage behavior (evaluation of thermomechanical analysis (TMA))
The heat shrinkage behavior of the film is evaluated under the following conditions. Measurement device: The shrinkage factor TMA (%) in the MD direction when reaching 100 ° C. at a heating rate of 3 ° C./min from Thermo Plus TMA 8310 (manufactured by Rigaku Corporation) at 30 ° C. is measured.
・ Size: Width 5mm, length 20mm
・ Measurement direction: MD
・ Load: 19.6 N (equivalent to 2 g)
・ Temperature range: 30 to 100 ° C (2 cycles)
· Heating rate: 3 ° C / min

<7> Preparation of lithium secondary battery and method of measuring battery characteristics 70% by weight of LiCoO ₂ (positive electrode active material), 20% by weight of acetylene black (conductive agent), 10% by weight of polytetrafluoroethylene (binder) % Mixed and compression molded to prepare a positive electrode. 95% by weight of natural graphite (negative electrode active material) and 5% by weight of ethylene propylene diene monomer (binding agent) were mixed, and this was compression molded to prepare a negative electrode. Then, using the laminated porous film (separator) described in the examples and the comparative examples, an electrolytic solution (ethyl carbonate (EC) / methyl ethyl carbonate (MEC) = 30/70 containing 1.0 M LiPF ₆ ,% by weight Solution was impregnated to prepare a CR2032 coin battery. After charging to a final voltage of 4.2 V at a constant current such that the speed of 0.2, 1, 3, 4 or 5 C at room temperature (25 ° C.) using this coin battery, to a final voltage of 3.0 V It was discharged. The battery characteristics were evaluated by evaluating the discharge capacity per weight of the active material when performing the charge and discharge in this manner.

Example 1
(Production of a microporous polyolefin film having a three-layer structure of PP / PE / PP)
A state in which the take-up direction is fixed after melt extrusion of a polypropylene resin having a weight average molecular weight of 55 to 750,000 and a molecular weight distribution of 7.5 to 16 into a film of 7 μm thickness using a T-die molding apparatus Heat treatment at 135 ° C. for 60 seconds.
Further, as a polyethylene resin, a polyethylene resin having a weight average molecular weight of 220,000 to 400,000 and a molecular weight distribution of 6 to 15 was melt extruded into a film having a thickness of 5 μm using a T-die molding machine. The polyethylene film was heat-treated at 120 ° C. for 60 seconds in a fixed take-up direction, and then cooled to room temperature.

  A heat-treated polypropylene film and a polyethylene film are laminated in a three-layer configuration, with polypropylene disposed on the surface layer and polyethylene disposed on the inner layer (intermediate layer), and thermocompression bonding with a heating roll at a temperature of 120 ° C and a linear pressure of 1.8 kg / cm. It was then cooled by a 50.degree. C. chill roll. The film thickness of the obtained unstretched laminated film was 20 μm.

  The unstretched laminated film is cold-drawn at 30 ° C. by 25% and then hot-stretched in the length direction of the film to a total stretch of 180% in a hot air circulating oven heated to 123 ° C. The heat setting was performed for 70 seconds in the relaxed state, to obtain a three-layered laminated porous film A of PP / PE / PP. The film thickness of the obtained polyolefin microporous film A was 16 μm. The Gurley value is 272 s / dL.

(Production of laminated porous film (separator for electricity storage device))
Water is added to 96 parts by weight of boehmite (chemical composition AlOOH, long diameter 4.5 μm, aspect ratio 5.4) and 4 parts by weight of commercially available water-soluble polyvinyl butyral so that the solid concentration becomes 40% by weight, and an alumina planet It charged into the pot for ball mills. The mixture was stirred and mixed by a planetary ball mill for 60 minutes, and the ink was adjusted to obtain a coating liquid. Using a continuous coating device (made by Imoto Machinery), apply a coating solution with a constant film thickness to polyolefin microporous film A fixed to a glass substrate under the condition of a conveyance speed of 0.08 m / min, 80 Drying was performed at 0 ° C. to obtain a laminated porous film (separator for power storage device) in which a heat-resistant porous layer containing plate-like inorganic particles was formed. The supported amount of boehmite is 0.7 mg / cm ² , and the layer thickness of the heat-resistant porous layer containing plate-like inorganic particles is 6 μm.

  The film thickness of the obtained laminated porous film (separator for electrical storage devices) was 22 micrometers.

(Evaluation of local heating tolerance)
It evaluated based on the evaluation method (measurement method of correction | amendment through-diameter) of the local heating tolerance mentioned above with respect to the produced said laminated porous film. The obtained results are shown in Table 1. It was confirmed that the local heating resistance of the power storage device separator in which the porous layer containing the plate-like inorganic particles was formed was improved.
(Evaluation of evaluation of heat shrinkage behavior)
It evaluated based on the evaluation method of the heat shrink behavior mentioned above with respect to the produced said laminated porous film. It was confirmed that the local heating resistance of the power storage device separator in which the porous layer containing the plate-like inorganic particles was formed was improved.

(Measurement of curl height)
The curling height of the laminated porous film in which the porous layer containing the plate-like inorganic particles was formed was evaluated based on the method of measuring the curling height described above, in which the heat drawing process was performed on the manufactured laminated porous film. . The obtained results are summarized in Table 1 and shown. It was confirmed that curling of the separator for a storage battery in which the porous layer containing plate-like inorganic particles was formed by the heat drawing treatment was reduced. The results are shown in Table 1.

Example 2
The laminated porous film was produced in the same manner as in Example 1, except that the coating conditions were changed and the film thickness of the obtained laminated porous film 1 (separator for power storage device) was 28 μm (the film thickness of the porous layer 12 μm). (Separator for electricity storage device) was produced.
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.

Example 3
A laminated porous film (separator for an electricity storage device) was produced in the same manner as in Example 1 except that boehmite (chemical composition AlOOH, long diameter 5.8 μm, aspect ratio 4.6).
The film thickness of the obtained laminated porous film (separator for power storage devices) was 22 μm (the film thickness of the porous layer was 6 μm).
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.

Example 4
The laminated porous film was prepared in the same manner as in Example 3, except that the coating conditions were changed, and the film thickness of the obtained laminated porous film 1 (separator for power storage device) was 25 μm (the film thickness of the porous layer was 9 μm). (Separator for electricity storage device) was produced.
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.

Example 5
A laminated porous film (separator for an electricity storage device) was produced in the same manner as in Example 1 except that boehmite (chemical composition AlOOH, long diameter: 8.2 μm, aspect ratio: 10.9).
The film thickness of the obtained laminated porous film (separator for electrical storage devices) was 21 micrometers (film thickness 5 micrometers of a porous layer).
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.

Example 6
The laminated porous film was produced in the same manner as in Example 5, except that the coating conditions were changed, and the film thickness of the obtained laminated porous film 1 (separator for power storage device) was 30 μm (the film thickness of the porous layer is 14 μm). (Separator for electricity storage device) was produced.
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.

Example 7
The coating conditions were changed, and the film thickness of the obtained laminated porous film 1 (separator for power storage device) was 21 μm (the film thickness of the porous layer 5 μm), and the binder was a water dispersion system (emulsion type commercially available acrylic binder) A laminated porous film (separator for an electricity storage device) was produced in the same manner as in Example 5 except for using.
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.

Example 8
The laminated porous film was prepared in the same manner as in Example 7, except that the coating conditions were changed, and the film thickness of the obtained laminated porous film 1 (separator for power storage device) was 22 μm (the film thickness of the porous layer 6 μm). (Separator for electricity storage device) was produced.
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.

Example 9
The laminated porous film was obtained in the same manner as in Example 7 except that the coating conditions were changed, and the film thickness of the obtained laminated porous film 1 (separator for power storage device) was 31 μm (the film thickness of the porous layer 15 μm). (Separator for electricity storage device) was produced.
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.

Example 10
The laminated porous film was obtained in the same manner as in Example 10, except that the coating conditions were changed, and the film thickness of the obtained laminated porous film 1 (separator for power storage device) was 31 μm (the film thickness of the porous layer 15 μm). (Separator for electricity storage device) was produced.
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.

Example 11
The coating conditions were changed, and the film thickness of the obtained laminated porous film 1 (separator for power storage device) was 21 μm (the film thickness of the porous layer 5 μm), and the binder was a water dispersion system (emulsion type commercially available acrylic binder) A laminated porous film (separator for an electricity storage device) was produced in the same manner as in Example 10 except for using.
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.
Moreover, about evaluation of local heating tolerance, the experimental data which does not penetrate even if it applies a soldering iron for 30 minutes was obtained.

Example 12
The laminated porous film was obtained in the same manner as in Example 12, except that the coating conditions were changed, and the film thickness of the obtained laminated porous film 1 (separator for power storage device) was 23 μm (the film thickness of the porous layer 7 μm). (Separator for electricity storage device) was produced.
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.
Moreover, about evaluation of local heating tolerance, the experimental data which does not penetrate even if it applies a soldering iron for 30 minutes was obtained.

Example 13
The laminated porous film was obtained in the same manner as in Example 12, except that the coating conditions were changed, and the film thickness of the obtained laminated porous film 1 (separator for power storage device) was 31 μm (the film thickness of the porous layer 15 μm). (Separator for electricity storage device) was produced.
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.
Moreover, about evaluation of local heating tolerance, the experimental data which does not penetrate even if it applies a soldering iron for 30 minutes was obtained.

Comparative Example 1
The polyolefin microporous film (film thickness 16 μm) obtained in Example 1 was evaluated as a separator for a storage device. Its local heat resistance, heat shrinkage behavior and curl height were measured. The results are shown in Table 1.

Comparative Example 2
A laminated porous film (separator for an electricity storage device) was produced in the same manner as in Example 1 except that boehmite (chemical composition AlOOH, long diameter 2 μm, aspect ratio 5.8).
The film thickness of the obtained laminated porous film (separator for electrical storage devices) was 28 micrometers (film thickness 12 micrometers of a porous layer).
The local heat resistance, the thermal contraction behavior, and the curl height of the produced laminated porous film (separator for power storage devices) were measured. The results are shown in Table 1.

(Evaluation of charge and discharge performance of battery subjected to heat drawing treatment)
Evaluation based on the method for measuring the lithium secondary battery and the battery characteristics described above, the charge and discharge performance of the laminated porous film (separator for power storage device) produced by the method of Examples 1 to 14 and Comparative Example by the coin battery did. The obtained results are shown in Table 2.
It was confirmed that the charge and discharge characteristics of the battery did not change significantly depending on the type and presence of the inorganic particle layer.

Color change level 1: narrow color change range and no through holes at all;
Discoloration level 2: A wide discoloring range but almost no through holes;
Color change level 3: The color change range is wide and a through hole is formed.

  The discharge characteristics of the batteries produced using the laminated porous films described in Examples 1, 3, 5, 6, 9, 10, 11, 14 and Comparative Examples 1 and 2 are shown in Table 2 below.

  According to the present invention, it is possible to improve the local heating resistance and to suppress the occurrence of warpage, and when used as a storage device separator, it is possible to obtain a laminated porous film in which the storage device can exhibit good performance. Can be provided. In particular, the reliability of these vehicles can be enhanced by using the battery as a storage device such as a lithium ion secondary battery mounted on a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a battery electric vehicle.

Claims (10)

A laminated porous film in which a heat-resistant porous layer containing inorganic particles formed in a plate shape is laminated on at least one surface of a microporous polyolefin film,
The multilayer porous film, wherein the major diameter of the inorganic particles is 4 μm or more.   The heat-resistant porous layer is characterized in that when the terminal heated to 400 degrees is abutted for 5 seconds, no through-hole for drilling both the heat-resistant porous layer and the polyolefin microporous film is formed. The laminated porous film according to Item 1.   The laminated porous film according to claim 2, wherein the shrinkage rate in the MD direction when reaching 100 ° C at a temperature rising rate of 3 ° C / min from a temperature of 30 ° C by thermomechanical analysis (TMA) is 0.8% or less.   A rectangular piece cut out with a size of 100 mm in a side in the machine direction and 100 mm in a direction substantially orthogonal to the machine direction is placed on the heat resistant porous layer at the top under an environment of a temperature of 23 ° C. and a dew point of −40 ° C. 4. The laminated porous film according to claim 2, wherein a total floating amount of the rectangular pieces is 16 mm or less on both the front side and the back side when left to stand for 1 hour.   The laminated porous film according to any one of claims 2 to 4, wherein the rate of increase in Gurley value is 30% or less with respect to the polyolefin microporous film of the substrate.   The aspect ratio with respect to the thickness of the said inorganic particle is 4.5 or more, The laminated porous film as described in any one of Claims 1-5 characterized by the above-mentioned.   The laminated porous film according to claim 6, wherein the inorganic particles are boehmite. The thickness of the microporous polyolefin film is 16 μm or less, the thickness of the heat-resistant porous layer containing the inorganic particles is 15 μm or less, the amount of inorganic particles supported is 2.0 mg / cm ² or less, and all layers are The laminated porous film according to any one of claims 2 to 5, which has a Gurley value of 400 seconds or less / 100 cc.   The separator for electrical storage devices which consists of a laminated porous film as described in any one of Claims 1-8.   A storage device comprising the storage device separator according to claim 9, a positive electrode, and a negative electrode.