JP2012129115A - Separator for nonaqueous electrolyte battery and nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for nonaqueous electrolyte battery having excellent mechanical strength and shutdown characteristics and being excellent in short circuit resistance in a high temperature.SOLUTION: A separator for nonaqueous electrolyte battery comprises: a porous base material which includes polyolefin with a characteristic viscosity of 5×10Pa s or more and 5×10Pa s or less and a non-newton fluidity of 0.15 or more and 0.4 or less, and whose crystallinity is 65% or more and 85% or less; and a heat-resistant porous layer provided on at least one surface of the porous base material and containing heat-resistant resin.

Description

  The present invention relates to a separator for a nonaqueous electrolyte battery and a nonaqueous electrolyte battery.

  Nonaqueous electrolyte batteries, particularly nonaqueous electrolyte batteries typified by lithium ion secondary batteries, have high energy density, and are therefore widely used as main power sources for portable electronic devices such as mobile phones and laptop computers. This lithium ion secondary battery is required to have a higher energy density, but ensuring safety is a technical issue.

  The role of the separator is important in ensuring the safety of the lithium ion secondary battery, and from the viewpoint of providing a shutdown function to the separator, a porous film of polyolefin, particularly polyethylene, has been conventionally used. Here, the shutdown function refers to the function of blocking the current flow by closing the pores of the porous membrane when the battery temperature rises, and is effective as a mechanism to avoid thermal runaway of the battery. ing.

  However, the shutdown function is based on the capping of pores due to the melting of a porous film such as polyethylene as its operating principle, and therefore does not necessarily coincide with heat resistance. That is, even after the shutdown function is activated, the battery temperature may rise further. In such a case, melting of the separator (so-called meltdown) proceeds to cause a short circuit inside the battery. May generate a large amount of heat, causing smoke, fire, or explosion. For this reason, in addition to the shutdown function, there is no risk of a short circuit occurring when the separator reaches a temperature higher than the temperature at which the shutdown function is manifested. It is required to have heat resistance with reduced risk.

  Under such circumstances, conventionally, a technique in which a heat-resistant porous layer containing a heat-resistant resin such as aromatic polyamide is formed on the surface of a polyolefin microporous film is known (see Patent Documents 1 and 2). Such a configuration is said to be excellent in that both a shutdown function and heat resistance can be achieved.

International Publication No. 2008/62727 Pamphlet International Publication No. 2008/156033 Pamphlet

  However, even with the above-described conventional configuration, when the battery is held at a temperature higher than the shutdown temperature for a long time or when an external force is applied, the separator is deformed inside the battery to prevent a short circuit of the battery. There are cases where it is not possible. Therefore, a separator having superior mechanical properties and excellent short-circuit resistance is desired for use in a high-temperature environment or a scene where an external force is applied.

  On the other hand, in order to improve the mechanical properties at high temperatures, improving the mechanical properties at high temperatures of the porous substrate formed using polyolefin directly affects the strength. If it tries to do so, the shutdown characteristic will be impaired, and conversely, there is a possibility that the shutdown function will not be exhibited at the necessary timing.

  The present invention has been made in view of the above, and has excellent mechanical strength and shutdown characteristics, as well as a separator for a nonaqueous electrolyte battery excellent in short circuit resistance at high temperatures, and thermal runaway and ignition are suppressed. Another object of the present invention is to provide a highly safe non-aqueous electrolyte battery and to achieve the object.

Specific means for achieving the above object are as follows.
<1> A polyolefin having a characteristic viscosity of 5 × 10 ⁵ Pa · s to 5 × 10 ⁶ Pa · s and a non-Newtonian fluidity of 0.15 to 0.4 and a crystallinity of 65 A separator for a non-aqueous electrolyte battery, comprising: a porous base material that is not less than 85% and no more than 85%; and a heat-resistant porous layer that is provided on at least one surface of the porous base material and contains a heat-resistant resin.

<2> Polyethylene including 5 to 90% by mass of ultra high molecular weight polyethylene having a weight average molecular weight of 1 million or more and high density polyethylene having a density of 0.942 g / cm ³ (JIS K 6748-1981) or more. It is a separator for nonaqueous electrolyte batteries as described in said <1> which is a composition.

  <3> A positive electrode, a negative electrode, and the separator for a nonaqueous electrolyte battery according to <1> or <2>, which is disposed between the positive electrode and the negative electrode. It is a non-aqueous electrolyte battery that obtains electric power.

ADVANTAGE OF THE INVENTION According to this invention, while having the outstanding mechanical strength and shutdown characteristic, the separator for nonaqueous electrolyte batteries excellent in the short circuit resistance under high temperature can be provided. Also,
According to the present invention, it is possible to provide a highly safe nonaqueous electrolyte battery in which thermal runaway or ignition is suppressed.

  Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is not restrict | limited to the said form, Various deformation | transformation can be implemented within the range of the summary.

[Separator for non-aqueous electrolyte battery]
The separator for a non-aqueous electrolyte battery of the present invention has a characteristic viscosity of 5 × 10 ⁵ Pa · s or more and 5 × 10 ⁶ Pa · s or less, and a non-Newtonian fluidity of 0.15 or more and 0.4 or less. And having a crystallinity of 65% or more and 85% or less, and a heat-resistant porous layer provided on at least one side of the porous substrate and containing a heat-resistant resin. It is.

  In the present invention, the polyolefin constituting the porous substrate has a characteristic viscosity and non-Newtonian fluidity satisfying a predetermined range, and the crystallinity of the porous substrate itself is in the predetermined range, so that the battery temperature While maintaining the fluidity to maintain the shutdown function that blocks the pores when the pores of the porous substrate rise, the behavior that appears as a viscosity change when receiving various stresses from the outside The instability of physical properties due to external stress is suppressed. As a result, film deterioration such as tearing or pinholes occurring when subjected to external stress is prevented, mechanical strength is maintained, and short-circuit resistance is improved.

  The separator for a non-aqueous electrolyte battery according to the present invention includes the porous substrate, a heat-resistant porous layer formed by including a heat-resistant resin, and laminated (preferably formed by coating) on at least one surface of the porous substrate; have. The total film thickness of such a nonaqueous electrolyte battery separator (hereinafter also simply referred to as “separator” or “separator of the present invention”) is preferably 30 μm or less.

Moreover, the following ranges are preferable for each physical property of the separator of the present invention.
The porosity of the separator for nonaqueous electrolyte batteries of the present invention is preferably 30 to 60% from the viewpoints of permeability, mechanical strength, and handling properties. More preferably, the porosity is 40% to 55%.
The Gurley value (JIS P8117) of the separator for nonaqueous electrolyte batteries of the present invention is preferably 100 to 500 sec / 100 cc from the viewpoint of improving the balance between mechanical strength and membrane resistance.
The membrane resistance of the non-aqueous electrolyte battery separator of the present invention is preferably 1.5 to 10 ohm · cm ² from the viewpoint of load characteristics of the non-aqueous electrolyte battery.

The puncture strength of the separator for a nonaqueous electrolyte battery of the present invention is preferably 250 to 1000 g, and more preferably 250 to 500 g. When the puncture strength is 250 g or more, when a non-aqueous electrolyte battery is produced, it has excellent resistance to electrode irregularities and impacts, prevents the occurrence of pinholes in the separator, and more effectively short-circuits the non-aqueous electrolyte battery. Can be avoided. The puncture strength is a value measured as a maximum puncture load by performing a puncture test using a KES-G5 handy compression tester (manufactured by Kato Tech Co., Ltd.) with a needle tip curvature radius of 0.5 mm and a puncture speed of 2 mm / sec. It is.
The tensile strength of the nonaqueous electrolyte battery separator of the present invention is preferably 10 N or more. When it is 10N or more, when producing a nonaqueous electrolyte battery in a long shape, it is preferable in that the separator can be wound well so as not to damage the separator.
The thermal shrinkage rate at 105 ° C. of the nonaqueous electrolyte battery separator of the present invention is preferably 0.5 to 10%.

(Porous substrate)
The separator for nonaqueous electrolyte batteries of the present invention is configured by providing a porous substrate containing polyolefin. Examples of the porous substrate include a layer having a porous structure of a microporous film shape, a nonwoven fabric shape, a paper shape, and other three-dimensional network shapes. A porous membrane-like layer is preferable. Here, the microporous film-like layer (hereinafter, also simply referred to as “microporous film”) has a structure in which a large number of micropores are connected and these micropores are connected to each other. A layer that allows gas or liquid to pass from one surface to the other.
This microporous membrane is preferably a polyolefin that softens at 120 to 150 ° C., closes the porous voids, exhibits a shutdown function, and does not dissolve in the electrolyte of the nonaqueous electrolyte battery.

  The porous substrate is mainly formed of polyolefin. Here, “mainly” means that the proportion of polyolefin in the porous substrate is 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and 100% by mass. % May mean.

  Examples of the raw material for forming the porous substrate include polyolefin, that is, polyethylene, polypropylene, polymethylpentene, a copolymer thereof, and the like. Among these, polyethylene is preferable, and from the viewpoint of strength, heat resistance, and the like, high-density polyethylene and a mixture of high-density polyethylene and ultrahigh molecular weight polyethylene are more preferable. As the ultra high molecular weight polyethylene, polyethylene having a weight average molecular weight of 1 million or more is preferable.

The molecular weight of polyethylene is preferably 500,000 to 5,000,000 in terms of weight average molecular weight, and a polyethylene composition containing 5% by mass or more of ultrahigh molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more is particularly preferable. Furthermore, a polyethylene composition containing 10 to 90% by mass of ultrahigh molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more is suitable.
The weight average molecular weight of the polyolefin is a molecular weight measured by gel permeation chromatography (hereinafter also referred to as GPC) and expressed in terms of polystyrene.

The density of the high-density polyethylene is preferably 0.942 g / cm ³ (JIS K 6748-1981) or more.

  The porous substrate in the present invention is preferably an embodiment in which 90% by mass or more is composed of polyolefin, and may contain other components that do not affect the battery characteristics of 10% by mass or less.

In the present invention, the characteristic viscosity of the polyolefin is in the range of 5 × 10 ⁵ Pa · s to 5 × 10 ⁶ Pa · s. The characteristic viscosity is obtained from the complex viscosity measured at 200 ° C. using a rotational dynamic viscoelasticity measuring device (ARES manufactured by Rheometric SPE Co., Ltd.), and the frequency ω (rad / s) is 0.1. It is a complex viscosity when it is and shows fluidity in low shear.
When the characteristic viscosity exceeds 5 × 10 ⁶ , sufficient fluidity cannot be obtained because the fine pores are blocked (that is, the shutdown function is exhibited), and the shutdown characteristics are impaired. Conversely, if the characteristic viscosity is less than 5 × 10 ⁵ , the separator shape cannot be maintained in a temperature region higher than the shutdown temperature, and the short-circuit resistance is lowered.

Among them, the characteristic viscosity is preferably 5 × 10 ⁵ Pa · s or more and 20 × 10 ⁵ Pa · s or less for the same reason as described above.

In the present invention, the non-Newtonian fluidity of polyolefin is in the range of 0.15 to 0.4. The non-Newtonian fluidity is obtained from the complex viscosity measured at 200 ° C. using a rotational dynamic viscoelasticity measuring device (ARES manufactured by Rheometric SPE Co., Ltd.). The ratio of complex viscosities at 1, that is, the viscosity η ^* when the vibration is given at the frequency ω = 1.0 with respect to the viscosity η ^* (ω = 0.1) when the vibration is given at the frequency ω = 0.1 ^. (Ω = 1.0) ratio [η ^* (ω = 1.0) / η ^* (ω = 0.1)]. The higher this value, the higher the non-Newtonian fluidity, that is, the greater the decrease in viscosity with respect to shear stress.
If the non-Newtonian fluidity exceeds 0.4, pinholes and fractures are likely to occur when shear stress is applied in the temperature range where fluidity develops, and mechanical properties at high temperatures decrease and short circuit resistance. Inferior to Further, if the non-Newtonian fluidity is less than 0.15, the moldability is deteriorated.
In general, when polyethylene is less than 0.15, the moldability is remarkably lowered. Therefore, by setting the non-Newtonian fluidity to 0.15 or more, a porous substrate can be formed better. Among these, the non-Newtonian fluidity is preferably in the range of 0.20 to 0.38.

  The method for controlling the characteristic viscosity and the non-Newtonian fluidity is not particularly limited, and examples thereof include adjusting the molecular weight of the polyolefin to be used and the number of branches in the molecule. Specifically, a method of mixing two or more kinds of polyethylenes having different molecular weights and densities, for example, a method of mixing two or more kinds including high molecular weight polyethylene and high density polyethylene can be mentioned.

Among the above, the characteristic viscosity and non-Newtonian fluidity satisfy the above range, while maintaining the fluidity to express the shutdown function, while maintaining the shape at high temperature, from the point of excellent mechanical strength and short circuit resistance, It is preferable to use a polyethylene composition containing 5 to 90% by mass of ultrahigh molecular weight polyethylene having a weight average molecular weight of 1 million or more and the balance being high density polyethylene having a density of 0.942 g / cm ³ (JIS K 6748-1981) or more. It is.

  In the present invention, the degree of crystallinity of the porous substrate constituting the separator is in the range of 65% to 85%. When the crystallinity is in this range, excellent mechanical strength and shutdown characteristics can be obtained even when the porous substrate is combined with the heat-resistant porous layer. In other words, if the degree of crystallinity is less than 65%, it is not preferable because fatigue resistance is lowered due to a decrease in mechanical strength, and pinholes are easily generated in the battery. If the degree of crystallinity exceeds 85%, it becomes hard and brittle and the elongation is lowered. Therefore, wrinkles and breakage are likely to occur due to the dimensional change of the active material due to charge and discharge in the battery.

  The crystallinity of the porous substrate can be easily determined by, for example, X-ray diffraction, and the crystallinity of the porous substrate can be determined by 2θ = 21.3, 23.7, 29 in wide-angle X-ray measurement. For the peak in the vicinity of .8, it can be obtained from the ratio of the sum of the integrated intensities to the total integrated intensity.

Here, when classifying polyolefin from the viewpoint of crystal, it is formed by the orientation of stretched polymer chains, and stretched chain crystals that affect the tensile strength, and the polymer chains are folded and oriented within or between molecules. It can be roughly divided into lamellar crystals formed by this and amorphous parts that move freely. In the amorphous part, there are a tie molecular part that bridges between lamella crystals and affects the puncture strength, and a part that can move freely in an equilibrium state between the crystalline part and the amorphous part.
In the present invention, the crystallinity of the polyolefin is determined from the ratio of the melting energy measured by DSC and the theoretical melting energy of the crystal, as shown in the following formula (1). In the following formula, 289 J / g · K is used as the theoretical melting energy.
Crystallinity = measured melting energy / theoretical melting energy (1)

  In the above formula (1), the melting energy measured by DSC is the sum of the melting energy of the extended chain crystal and the lamellar crystal. As the degree of crystallinity increases, the melting point, tensile strength, and puncture strength of the porous substrate are improved. Higher crystallinity means that the amorphous part is reduced. The polymer has entangled parts due to tie molecules in the amorphous part. As the degree of crystallinity increases, the amorphous part decreases, and as a result, the tie molecular density in the amorphous part increases. This amorphous part is often formed at the end or side chain of the crystal part, but the entanglement at the amorphous part constrains the crystals. Therefore, in terms of mechanical strength, it leads to improvement of puncture strength. However, restraint between crystals also causes an increase in melting point and causes a decrease in shutdown characteristics. Therefore, the range of crystallinity is preferably 65% to 85%.

  The method for controlling the degree of crystallinity is not particularly limited. For example, stretching conditions and heat setting conditions for producing a porous substrate, control of molecular weight distribution and branch structure of polyolefin used as raw material, raw material For example, control of the kneading temperature. Basically, as the molecular weight increases, the branching structure decreases, the stretching conditions increase, and the heat setting temperature decreases, the crystallinity tends to increase.

  In this invention, it is preferable that the film thickness of a porous base material is 5-25 micrometers from a viewpoint of the energy density of a nonaqueous electrolyte battery, a load characteristic, mechanical strength, and handling property. In particular, when the thickness of the porous substrate is 5 μm or more, the shutdown function is good, and when it is 25 μm or less, a range in which a high electric capacity can be realized can be maintained. The thickness of the porous substrate is preferably 5 to 20 μm.

The porosity of the porous substrate is preferably 30 to 60% from the viewpoints of permeability, mechanical strength, and handling properties.
The Gurley value (JIS P8117) of the porous substrate is preferably 50 to 500 sec / 100 cc from the viewpoint of obtaining a good balance between mechanical strength and membrane resistance.
The membrane resistance of the porous substrate is preferably 0.5 to ⁵ ohm · cm ² from the viewpoint of load characteristics of the nonaqueous electrolyte battery.
The puncture strength of the porous substrate is preferably 250 g or more.
The tensile strength of the porous substrate is preferably 10N or more.
The shutdown temperature of the porous substrate is preferably 130 to 150 ° C. The shutdown temperature refers to the temperature when the resistance value becomes 10 ³ ohm · cm ² . When the shutdown temperature is 130 ° C. or higher, the shutdown function can be maintained, the porous substrate is completely melted, and a phenomenon called meltdown in which a short-circuit phenomenon occurs hardly occurs, which is preferable in terms of safety. Moreover, since the shutdown temperature is 150 ° C. or lower, a safety function at high temperatures can be expected. The shutdown temperature is preferably 135 to 145 ° C.
The thermal shrinkage rate at 105 ° C. of the porous substrate is preferably in the range of 5% to 40%. When the thermal contraction rate is in the above range, the shape stability and shutdown characteristics of the separator for a nonaqueous electrolyte battery obtained by processing the porous substrate are balanced.

~ Method for producing porous substrate ~
Although there is no restriction | limiting in particular in the manufacturing method of the porous base material mentioned above, Specifically, it can manufacture by the method including the process of the following (1)-(6), for example. The polyolefin used as a raw material is as described above.

(1) Preparation of polyolefin solution A solution prepared by dissolving a predetermined amount of polyolefin in a solvent is prepared. At this time, a solvent may be mixed to prepare a solution. Examples of the solvent include paraffin, liquid paraffin, paraffin oil, mineral oil, castor oil, tetralin, ethylene glycol, glycerin, decalin, toluene, xylene, diethyltriamine, ethyldiamine, dimethyl sulfoxide, hexane, and the like. The concentration of the polyolefin in the polyolefin solution is preferably 1 to 35% by mass, more preferably 10 to 30% by mass. When the concentration of the polyolefin solution is 1% by mass or more, the gel-like molded product obtained by cooling gelation can be maintained so as not to be highly swollen with a solvent, so that it is difficult to be deformed and the handleability is good. On the other hand, when it is 35% by mass or less, the pressure during extrusion can be suppressed, so that the discharge amount can be maintained and the productivity is excellent. In addition, the alignment in the extrusion process is difficult to proceed, which is advantageous for ensuring stretchability and uniformity. In addition, it is preferable that the kneading | mixing temperature of the polyolefin solution which is a raw material is 190-220 degreeC, when obtaining the crystal physical property like this invention.

  The polyolefin solution is preferably used for filtration to remove foreign substances. There are no particular limitations on the filtration device, filter shape, mode, etc., and conventionally known devices and modes can be used. In this case, the hole diameter (filtration diameter) of the filter is preferably 1 μm or more and 50 μm or less from the viewpoint of filterability. When the hole diameter is 50 μm or less, the filterability is excellent and the foreign matter removal efficiency is good. Further, when the hole diameter is 1 μm or more, good filterability can be obtained, and productivity can be maintained high.

(2) Extrusion of polyolefin solution The prepared solution is kneaded with a single screw extruder or a twin screw extruder, and extruded with a T die or an I die at a temperature not lower than the melting point and not higher than the melting point + 60 ° C. A twin screw extruder is preferably used. Then, the extruded solution is passed through a chill roll or a cooling bath to form a gel composition. At this time, it is preferable to rapidly cool below the gelation temperature to cause gelation.

(3) Desolvation treatment Next, the solvent is removed from the gel composition. When a volatile solvent is used, the solvent can also be removed from the gel composition by evaporating by heating or the like, which also serves as a preheating step. In the case of a non-volatile solvent, the solvent can be removed by squeezing out under pressure. The solvent need not be completely removed.

(4) Stretching of the gel-like composition Following the solvent removal treatment, the gel-like composition is stretched. Here, a relaxation treatment may be performed before the stretching treatment. In the stretching treatment, the gel-like molded product is heated and biaxially stretched at a predetermined magnification by a normal tenter method, roll method, rolling method, or a combination of these methods. Biaxial stretching may be simultaneous or sequential. Moreover, it can also be set as longitudinal multistage extending | stretching, 3-stage extending | stretching, and 4-stage extending | stretching.
The stretching temperature is preferably in the range of 90 ° C. or higher and lower than the melting point of polyolefin, more preferably 100 to 120 ° C. When the heating temperature is lower than the melting point, the gel-like molded product is difficult to dissolve, so that the stretching can be performed satisfactorily. Further, when the heating temperature is 90 ° C. or higher, the gel-like molded product is sufficiently softened, so that it is difficult to break the film during stretching, and stretching at a high magnification can be performed.
Moreover, although a draw ratio changes with thickness of a raw fabric, it is preferable to carry out at least 2 times or more in a uniaxial direction, Preferably it is 4 to 20 times. In particular, from the viewpoint of controlling crystal parameters, the draw ratio is preferably 4 to 10 times in the machine direction (MD direction) and 6 to 15 times in the direction perpendicular to the machine direction (TD direction).
After stretching, heat setting is performed as necessary to provide thermal dimensional stability.

(5) Extraction and removal of solvent The stretched gel composition is immersed in an extraction solvent to extract the solvent. Examples of the extraction solvent include hydrocarbons such as pentane, hexane, heptane, cyclohexane, decalin, and tetralin, chlorinated hydrocarbons such as methylene chloride, carbon tetrachloride, and methylene chloride, and fluorinated hydrocarbons such as ethane trifluoride, Easily volatile compounds such as ethers such as diethyl ether and dioxane can be used. These solvents are appropriately selected according to the solvent used for dissolving the polyolefin composition, and can be used alone or in admixture of two or more. Solvent extraction removes the solvent in the porous substrate to less than 1% by weight.

(6) Annealing of microporous film The microporous film is heat-set by annealing. The annealing is preferably performed in the temperature range of 80 to 150 ° C. from the viewpoint of the heat shrinkage rate. Furthermore, the annealing temperature is preferably 115 to 135 ° C. from the viewpoint of having a predetermined heat shrinkage rate.

(Heat resistant porous layer)
The separator for a nonaqueous electrolyte battery according to the present invention is provided on at least one side of the porous substrate, and is provided with a heat resistant porous layer containing a heat resistant resin. Examples of the heat-resistant porous layer include microporous film-like, nonwoven fabric-like, paper-like, and other layers having a three-dimensional network-like porous structure, but more excellent heat resistance can be obtained. The layer is preferably a microporous membrane. A “microporous membrane layer” has a structure in which a large number of micropores are connected to each other and these micropores are connected, and gas or liquid can pass from one surface to the other. The layer that became.
Here, “heat resistance” refers to a property that does not cause melting or decomposition in a temperature range of less than 200 ° C.

-Heat resistant resin-
The heat resistant resin constituting the heat resistant porous layer may be any polymer having a melting point higher than the melting point of polyolefin or a thermal decomposition temperature. For example, wholly aromatic polyamides, fluorine resins, polyimides, polyamides Examples thereof include at least one resin selected from the group consisting of imide, polysulfone, polyketone, polyetherketone, polyetherimide, and cellulose.

  Since the heat resistant resin is insoluble in the electrolyte solution and has high durability, a wholly aromatic polyamide is preferable. In the wholly aromatic polyamide, for example, a small amount of an aliphatic component can be copolymerized. From the viewpoint of easily forming a porous layer and excellent redox resistance, polymetaphenylene isophthalamide, which is a meta-type wholly aromatic polyamide, is more preferable. Fluorine-based resins include polyvinylidene fluoride homopolymer and / or vinylidene fluoride as the main repeating unit, vinyl fluoride, ethylene trifluoride, tetrafluoroethylene, hexafluoropropylene, and trifluoroethylene chloride. And a copolymer containing at least one monomer from the group consisting of.

  The heat-resistant porous layer can be formed on both surfaces or one surface of the porous substrate, but is formed on both the front and back surfaces of the porous substrate from the viewpoint of handling properties, durability, and the effect of suppressing heat shrinkage. The form is preferred.

  In order to fix the heat-resistant porous layer on the substrate, a method in which the heat-resistant porous layer is directly formed on the substrate by a coating method is preferable. A technique of adhering the quality layer sheet on the base material using an adhesive or the like, a technique such as heat fusion or pressure bonding can also be employed.

  When the heat-resistant porous layer is formed on both sides of the porous substrate, the total thickness of the heat-resistant porous layer is preferably 3 μm or more and 12 μm or less. When the porous porous layer is formed only on one side of the porous base material, the thickness of the heat resistant porous layer is preferably 3 μm or more and 12 μm or less. Such a range of thickness is also preferable from the viewpoint of the effect of preventing liquid withering.

  The porosity of the heat resistant porous layer in the present invention is preferably 30 to 70% from the viewpoint of enhancing the effect of the present invention. When the porosity of the heat resistant porous layer is 30% or more, the resistance of the entire separator is good, and excellent battery characteristics are obtained. Further, when the porosity of the heat-resistant porous layer is 70% or less, the effect of suppressing the membrane breakage of the porous substrate is excellent. The porosity is more preferably in the range of 40-60%.

-Inorganic filler-
The heat-resistant porous layer in the present invention preferably contains at least one inorganic filler. The inorganic filler is not particularly limited, but specifically, metal oxides such as alumina, titania, silica, zirconia, metal carbonates such as calcium carbonate, metal phosphates such as calcium phosphate, aluminum hydroxide, hydroxide A metal hydroxide such as magnesium is preferably used. Such an inorganic filler is preferably highly crystalline from the viewpoints of impurity elution and durability.

  Especially, as an inorganic filler, what produces an endothermic reaction in 200-400 degreeC is preferable. Although it does not specifically limit as an inorganic filler which has such a characteristic, The inorganic filler which consists of a metal hydroxide, a boron salt compound, or a clay mineral etc., Comprising: What produces an endothermic reaction in 200-400 degreeC is mentioned. . Specific examples include aluminum hydroxide, magnesium hydroxide, calcium aluminate, dosonite, zinc borate and the like, and these can be used alone or in combination of two or more. In addition, these flame retardant inorganic fillers are appropriately mixed with other inorganic fillers such as metal oxides such as alumina, zirconia, silica, magnesia, and titania, metal nitrides, metal carbides, and metal carbonates. You can also.

  The average particle diameter of the inorganic filler is preferably in the range of 0.1 to 2 μm from the viewpoints of short circuit resistance at high temperature and moldability.

  As content of the inorganic filler in a heat resistant porous layer, it is preferable that it is 50-95 mass% from a heat resistant improvement effect, a viewpoint of permeability and handling property.

  In addition, the inorganic filler in the heat resistant porous layer is present in a state of being trapped by the heat resistant resin when the heat resistant porous layer is in the form of a microporous film, and the heat resistant porous layer is a nonwoven fabric or the like. In such a case, it may be present in the constituent fibers or fixed to the nonwoven fabric surface or the like with a binder such as a resin.

~ Method for producing heat-resistant porous layer ~
The method for producing the separator for a nonaqueous electrolyte battery of the present invention is not particularly limited as long as the separator of the present invention having the above-described configuration can be produced. For the heat-resistant porous layer, for example, the following (1) to (5) It can be manufactured through a process.

(1) Preparation of coating slurry A heat-resistant resin is dissolved in a solvent to prepare a coating slurry. The solvent is not particularly limited as long as it dissolves the heat-resistant resin, but specifically, a polar solvent is preferable, and examples thereof include N-methylpyrrolidone, dimethylacetamide, dimethylformamide, and dimethylsulfoxide. Moreover, the said solvent can add the solvent used as a poor solvent with respect to heat resistant resin in addition to these polar solvents. By applying such a poor solvent, a microphase separation structure is induced and the formation of a heat-resistant porous layer is facilitated. As the poor solvent, alcohols are preferable, and polyhydric alcohols such as glycol are particularly preferable. The concentration of the heat-resistant resin in the coating slurry is preferably 4 to 9% by mass. Moreover, an inorganic filler is disperse | distributed to this as needed, and it is set as the slurry for coating. In dispersing the inorganic filler in the coating slurry, when the dispersibility of the inorganic filler is not preferable, a method of improving the dispersibility by surface-treating the inorganic filler with a silane coupling agent or the like is also applicable.

(2) Coating of slurry The slurry is coated on at least one surface of the polyolefin porous substrate. When forming a heat resistant porous layer on both surfaces of a polyolefin porous substrate, it is preferable from a viewpoint of shortening of a process to apply simultaneously on both surfaces of a substrate. Examples of the method for coating the slurry for coating include a knife coater method, a gravure coater method, a screen printing method, a Meyer bar method, a die coater method, a reverse roll coater method, an ink jet method, a spray method, and a roll coater method. . Among these, the reverse roll coater method is preferable from the viewpoint of uniformly forming a coating film. When simultaneously applying to both sides of the polyolefin porous substrate, for example, by applying the polyolefin porous substrate between a pair of Meyer bars, apply an excess coating slurry on both sides of the porous substrate, There is a method in which this is passed between a pair of reverse roll coaters to scrape off excess slurry and precisely weighed.

(3) Solidification of slurry The heat resistance of the heat-resistant resin is obtained by coagulating the heat-resistant resin by treating the substrate coated with the slurry with a coagulation liquid capable of coagulating the heat-resistant resin. A porous layer is formed.
As a method of treating with the coagulating liquid, a method of spraying the coagulating liquid on the substrate coated with the coating slurry, or a method of immersing the substrate in a bath (coagulating bath) containing the coagulating liquid. Etc. Here, when installing a coagulation bath, it is preferable to install it below the coating apparatus. The coagulation liquid is not particularly limited as long as it can coagulate the heat-resistant resin, but water or a solution obtained by mixing an appropriate amount of water with the solvent used in the slurry is preferable. Here, the mixing amount of water is preferably 40 to 80% by mass with respect to the coagulating liquid. If the amount of water is 40% by mass or more, the time required for solidifying the heat-resistant resin can be kept shorter, the solidification can be performed well, and the stress and elongation at the proof stress point do not become too large. Can be adjusted. In addition, when the amount of water is 80% by mass or less, the surface of the heat-resistant resin layer in contact with the coagulation liquid is not solidified too quickly, and the surface is well porous and the crystallization proceeds appropriately. The strength can be maintained, and the stress and elongation at the proof stress can be kept high. Furthermore, the cost for solvent recovery can be kept low.

(4) Removal of coagulating liquid The coagulating liquid is removed by washing with water.
(5) Drying Dry and remove water from the sheet. There is no particular limitation on the drying method, but the drying temperature is preferably 50 to 80 ° C. When a high drying temperature is applied, in order to prevent a dimensional change due to heat shrinkage, it may be brought into contact with a roll. It is preferable to apply the method.

[Nonaqueous electrolyte battery]
The non-aqueous electrolyte battery of the present invention includes a positive electrode, a negative electrode, and the separator for a non-aqueous electrolyte battery of the present invention having the above-described configuration, and is formed by lithium doping / dedoping. It is configured to obtain electric power.

  Such non-aqueous electrolyte batteries include non-aqueous primary batteries such as lithium ion primary batteries, and non-aqueous secondary batteries that obtain an electromotive force by doping and dedoping lithium such as lithium ion secondary batteries and polymer secondary batteries. A battery is mentioned. The non-aqueous electrolyte battery has a structure in which a separator is disposed between a negative electrode and a positive electrode, the battery element is impregnated with an electrolytic solution, and this is enclosed in an exterior.

The negative electrode has a structure in which a negative electrode mixture comprising a negative electrode active material, a conductive additive and a binder is formed on a current collector. Examples of the negative electrode active material include materials that can be electrochemically doped with lithium, and examples thereof include carbon materials, silicon, aluminum, tin, and wood alloys. In particular, from the viewpoint of utilizing the effect of preventing liquid withering by the separator for a nonaqueous electrolyte battery of the present invention, it is preferable to use a negative electrode active material having a volume change rate of 3% or more in the process of dedoping lithium. Examples of such a negative electrode active material include Sn, SnSb, Ag ₃ Sn, artificial graphite, graphite, Si, SiO, V ₅ O _{4 and the} like. Examples of the conductive assistant include carbon materials such as acetylene black and ketjen black. The binder is made of an organic polymer, and examples thereof include polyvinylidene fluoride and carboxymethyl cellulose. As the current collector, a copper foil, a stainless steel foil, a nickel foil, or the like can be used.

The positive electrode has a structure in which a positive electrode mixture comprising a positive electrode active material, a conductive additive and a binder is formed on a current collector. Examples of the positive electrode active material include lithium-containing transition metal oxides. Specifically, LiCoO ₂ , LiNiO ₂ , LiMn _0.5 Ni _0.5 O ₂ , LiCo _1/3 Ni _1/3 Mn _{1 / 3 O 2, LiMn 2 O 4} , LiFePO 4, LiCo 0.5 Ni 0.5 O 2, LiAl 0.25 Ni 0.75 O 2 and the like. In particular, from the viewpoint of utilizing the effect of preventing liquid withering by the separator for a nonaqueous electrolyte battery of the present invention, it is preferable to use a positive electrode active material having a volume change rate of 1% or more in the process of dedoping lithium. Examples of such a positive electrode active material include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiCo _0.5 Ni _0.5 O ₂ , LiAl _0.25 Ni _0.75 O _{2 and the} like. Examples of the conductive assistant include carbon materials such as acetylene black and ketjen black. The binder is made of an organic polymer, and examples thereof include polyvinylidene fluoride. As the current collector, aluminum foil, stainless steel foil, titanium foil, or the like can be used.

The electrolytic solution has a structure in which a lithium salt is dissolved in a non-aqueous solvent. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO _{4 and the} like. Examples of the non-aqueous solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, vinylene carbonate, and the like. These may be used alone or in combination.

  Examples of the exterior material include a metal can or an aluminum laminate pack. The shape of the battery includes a square shape, a cylindrical shape, a coin shape, and the like, and the nonaqueous electrolyte battery separator of the present invention can be suitably applied to any shape.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. In this example, a case where a non-aqueous electrolyte lithium secondary battery is manufactured as a non-aqueous electrolyte battery will be described as an example. Unless otherwise specified, “part” is based on mass.

[Measurement and evaluation method]
Each value in the examples was determined according to each method described below.
(1) Molecular weight of polyolefin The weight average molecular weight of polyolefin was measured by gel permeation chromatography (GPC). Specifically, 20 ml of a GPC measurement mobile phase was added to 15 mg of the sample and completely dissolved at 145 ° C., followed by filtration through a stainless steel sintered filter (pore diameter: 1.0 μm). 400 μl of the filtrate was injected into the apparatus for measurement, and the weight average molecular weight of the sample was determined.
-Apparatus: Gel permeation chromatograph Alliance GPC2000 (manufactured by Waters)
Column: TSKgel GMH6-HT × 2 + TSKgel GMH6-HT × 2 (manufactured by Tosoh Corporation)
Column temperature: 140 ° C
・ Mobile phase: o-dichlorobenzene ・ Detector: Differential refractometer (RI)
・ Molecular weight calibration: monodisperse polystyrene (manufactured by Tosoh Corporation)

(2) Characteristic viscosity Characteristic viscosity is complex at 200 ° C. using a rotary dynamic viscoelasticity measurement device (ARES, manufactured by Rheometric SPE Co., Ltd.) while giving vibration with a frequency ω of 0.1 rad / s. The viscosity was measured and used as the characteristic viscosity.

(3) Non-Newtonian fluidity Non-Newtonian fluidity is measured using a rotational dynamic viscoelasticity measuring device (RES, manufactured by Rheometric SPE Co., Ltd.), with a frequency ω of 0.1 rad / s and 1.0 rad / s. The complex viscosity was measured at 200 ° C. while giving vibrations, and the ratio of the complex viscosity at the frequency ω1.0 and the frequency 0.1 was obtained, which was used as an index for evaluating the non-Newtonian fluidity.
Specifically, with respect to the viscosity η ^{* (ω} = 0.1) when vibrated at a frequency several omega = 0.1, viscosity eta ^{* (omega} when vibrated by vibration frequency omega = 1.0 = 1.0) [η ^* (ω = 1.0) / η ^* (ω = 0.1)].

(4) Film thickness The thickness of the separator for the nonaqueous electrolyte secondary battery (total thickness of the polyethylene porous substrate and the heat-resistant porous layer), the thickness of the polyethylene porous substrate and the heat-resistant porous layer, 20 points were measured with a film thickness meter (manufactured by Mitutoyo Corporation) and averaged. Here, the contact terminal used was a cylindrical one having a bottom surface of 0.5 cm in diameter.

(5) Porosity The porosity of the nonaqueous electrolyte secondary battery separator, the polyethylene porous substrate, and the heat-resistant porous layer was determined according to the following calculation method.
The constituent components of the layer of interest are a, b, c,..., N, and the masses of the constituent components are Wa, Wb, Wc,..., Wn (g / cm ² ). When the density is xa, xb, xc,..., Xn (g / cm ³ ) and the film thickness of the layer of interest is t (cm), the porosity ε (%) can be calculated from the following equation: Desired.
ε = {1− (Wa / xa + Wb / xb + Wc / xc +... + Wn / xn) / t} × 100

(6) Puncture strength The puncture strength of the separator for a nonaqueous electrolyte secondary battery is determined by using a KES-G5 handy compression tester manufactured by Kato Tech Co., with a radius of curvature of the needle tip of 0.5 mm and a puncture speed of 2 mm / sec. The piercing test was conducted with the maximum piercing load as the piercing strength. The sample was fixed by holding a silicon rubber packing together with a metal frame (sample holder) having a hole of φ11.3 mm.

(7) Crystallinity The degree of crystallinity of the polyethylene porous substrate is the ratio of the sum of integral intensities to the total integral intensities of peaks around 2θ = 21.3, 23.7, 29.8 in wide-angle X-ray measurement. Was calculated.

(8) Shutdown temperature The shutdown temperature (SD temperature) was determined by the following method.
A circular sample having a diameter of 19 mm was punched out of a polyethylene porous substrate having a polymetaphenylene isophthalamide layer on both sides, and the obtained sample was 3% by mass of a nonionic surfactant (Emulgen 210P, manufactured by Kao Corporation). It was immersed in a dissolved methanol solution (methanol: Wako Pure Chemical Industries, Ltd.) and air-dried. This sample was sandwiched between two circular stainless steel plates (SUS plates) having a diameter of 15.5 mm used as electrode plates. Next, the sample was impregnated with an electrolytic solution (made by Kishida Chemical Co., Ltd.) in which 1M LiBF ₄ was mixed with a mixed solvent of propylene carbonate (PC) / ethylene carbonate (EC) (PC / EC = 1/1 [mass ratio]). And sealed in a 2032 type coin cell. I took the lead from the coin cell, put a thermocouple, and put it in the oven. The temperature of the cell was increased at a temperature increase rate of 1.6 ° C./min, and the resistance of the cell was measured at the same time by the AC impedance method at an amplitude of 10 mV and a frequency of 100 kHz. The temperature at which the resistance value was 10 ³ ohm · cm ² or more was defined as the shutdown temperature.

(9) Short circuit resistance (nail penetration test)
-Preparation of test battery-
The following positive electrode and negative electrode were disposed opposite to each other with a separator interposed therebetween. This was impregnated with an electrolytic solution and sealed in an outer package made of an aluminum laminate film to produce a nonaqueous electrolyte secondary battery (prototype battery). Here, a solution (Kishida Chemical Co., Ltd.) containing 1M LiPF ₆ mixed with a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC / EMC = 3/7 [mass ratio]) was used as the electrolytic solution. Made).
(Positive electrode) Lithium cobaltate (LiCoO ₂ ; manufactured by Nippon Kagaku Kogyo Co., Ltd.) powder, 89.5 parts, acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd .; trade name: Denka Black), polyvinylidene fluoride (manufactured by Kureha Chemical Co., Ltd.) ) These were kneaded using N-methyl-2pyrrolidone solvent so as to be 6 parts to prepare a slurry. The obtained slurry was applied onto an aluminum foil having a thickness of 20 μm, dried and pressed to obtain a positive electrode having a thickness of 100 μm.
(Negative electrode) Mesophase carbon microbeads (MCMB: Osaka Gas Chemical Co., Ltd.) powder 87 parts, acetylene black (Electrochemical Industry Co., Ltd .; trade name Denka Black) 3 parts, polyvinylidene fluoride (Kureha Chemical Co., Ltd.) 10 parts Thus, these were knead | mixed using the N-methyl-2 pyrrolidone solvent, and the slurry was produced. The obtained slurry was applied onto a copper foil having a thickness of 18 μm, dried and pressed to obtain a negative electrode having a thickness of 90 μm.
-Test method-
About the prototype battery produced as described above, the obtained battery was charged at 1C until the battery voltage reached 4.2V, and then charged at a constant voltage for 3 hours at that voltage to obtain a fully charged state. A φ2.5 mm iron nail was driven through the charged battery and penetrated. At this time, the case where the opening of the aluminum laminate film due to an internal short-circuit was not recognized was “◯”, and the case where it was recognized was “x”.

(10) Film breakage test Each of the produced separator samples was cut into 10 cm × 10 cm, fixed to a frame that could be fixed in four directions, and heat-treated at 200 ° C. for 30 minutes. This operation was repeated 5 times, and the film that did not break during the 5 operations was evaluated as “◯”, and the film that was broken was evaluated as “x”.

[Preparation of polyethylene (PE) material]
-Synthesis Example 1: Synthesis of ultra high molecular weight PE-
(1) Preparation of solid catalyst component A 2-liter round bottom flask fully substituted with nitrogen gas and equipped with a stirrer was charged with 100 g of diethoxymagnesium and 130 ml of tetraisopropoxytitanium to form a suspended state. Treated with stirring at 130 ° C. for 6 hours. Next, after cooling to 90 ° C., 800 ml of toluene preheated to 90 ° C. was added and stirred for 1 hour to obtain a uniform solution. 90 ml of this solution was stirred at a stirring speed of 500 rpm in 150 ml of n-heptane at 0 ° C. and 50 ml of silicon tetrachloride introduced into a 500 ml round bottom flask equipped with a stirrer while maintaining the temperature in the system at 0 ° C. While adding over 1 hour. Thereafter, the temperature was raised to 55 ° C. over 1 hour and reacted for 1 hour to obtain a white finely divided solid composition. Next, after removing the supernatant, 40 ml of toluene was added to form a slurry. To this, 20 ml of room temperature titanium tetrachloride in which 0.5 g of sorbitan distearate was previously dissolved was added with stirring, and 1.5 ml of di-n-butyl phthalate was further added to 110 ° C. over 3 hours. The temperature was raised and the treatment was performed for 2 hours. Finally, by washing 7 times with 100 ml of room temperature n-heptane, about 10 g of solid catalyst component was obtained.

(2) Polymerization 700 ml of n-heptane was charged into a 1500-ml stainless steel autoclave equipped with a stirrer that was completely replaced with ethylene gas, and 0.70 mmol of triethylaluminum was charged while maintaining the ethylene gas atmosphere at 20 ° C. I entered. Subsequently, after raising the temperature to 70 ° C., the solid catalyst component obtained above was charged in an amount of 0.006 mmol in terms of titanium atom. Then, polymerization was carried out for 10 hours while supplying ethylene so that the pressure in the system was 5 kg / cm ² · G. After separation by filtration, it was dried under reduced pressure to obtain ultrahigh molecular weight polyethylene (PE) powder (shown as UH in Table 1 below).
The weight average molecular weight (Mw) of the obtained PE was 6 million or more.

-Synthesis example 2: Synthesis of high-density PE-
In the polymerization of Synthesis Example 1, the amount of the solid catalyst component charged was changed from 0.006 mmol to 0.0048 mmol in terms of titanium atom, and the pressure in the system was changed from 5 kg / cm ² · G to 4 kg / cm 2. ^A high-density polyethylene (PE) powder (indicated as HD in Table 1 below) in the same manner as in Synthesis Example 1, except that the polymerization time was changed from ² hours to 10 hours to 1.5 hours. Got.
The obtained PE had a weight average molecular weight (Mw) of 810,000 and a density of 0.947 g / cm ³ .

-Preparation of ultra high molecular weight polyethylene-
As commercially available PE, GUR2126 (weight average molecular weight 41.50 million) manufactured by Ticona was prepared.

-Preparation of high density polyethylene-
GURX143 (weight average molecular weight 560,000, density 0.950 g / cm ³ ) manufactured by Ticona was prepared as a commercially available PE.

[Production of poly (metaphenylene isophthalamide)]
When 160.5 g of isophthalic acid chloride was dissolved in 1120 ml of tetrahydrofuran and a solution of 85.2 g of metaphenylenediamine in 1120 ml of tetrahydrofuran was gradually added as a trickle while stirring, a milky white solution was obtained. Stirring was continued for about 5 minutes, and then an aqueous solution in which 167.6 g of sodium carbonate and 317 g of sodium chloride were dissolved in 3400 ml of water was rapidly added while stirring for 5 minutes. The reaction system increased in viscosity after a few seconds and then decreased again to obtain a white suspension. This was allowed to stand, the separated transparent aqueous solution layer was removed, and 185.3 g of a white polymer of polymetaphenylene isophthalamide (hereinafter also referred to as “PMIA”) was obtained by filtration. The number average molecular weight of PMIA was 24,000.

Example 1
-Production of polyethylene porous substrate 1-
The ultra-high molecular weight PE powder synthesized above and the high-density PE powder were mixed at a ratio of 6.3 / 93.7 (mass ratio) as shown in Table 1 below. The resulting physical properties of the polyethylene mixture, the weight average molecular weight: 1.2 million, the weight average molecular weight of 10 ^70,000 content: 1.8 wt%, further, characteristic viscosity: 5.1 × ¹⁰ 5 Pa · s Non-Newtonian fluidity: 0.38.
This polyethylene mixture was dissolved in a mixed solvent in which liquid paraffin (manufactured by Matsumura Oil Research Co., Ltd .; Smoyl P-350P; boiling point 480 ° C.) and decalin were mixed so that the polyethylene concentration was 30% by mass, and a polyethylene solution was obtained. Was made. The composition of this polyethylene solution is polyethylene: liquid paraffin: decalin = 30: 45: 25 (mass ratio).
Next, the polyethylene solution was extruded from a die at 208 ° C. and cooled in a water bath to prepare a gel tape (base tape). This base tape was dried at 60 ° C. for 8 minutes and at 95 ° C. for 15 minutes, and the obtained base tape was subjected to longitudinal stretching and lateral stretching in succession, and stretched by biaxial stretching. Here, in the longitudinal stretching, the stretching ratio is 5.5 times and the stretching temperature is 90 ° C., and in the lateral stretching, the stretching ratio is 11.0 times and the stretching temperature is 105 ° C., and the high area ratio is 60.5. Drawing was performed. After the end of transverse stretching, heat setting was performed at 130 ° C.
Next, this was immersed in a methylene chloride bath to extract liquid paraffin and decalin. Thereafter, the polyethylene porous substrate 1 having a thickness of 12 μm was obtained by drying at 50 ° C. and annealing at 120 ° C. The characteristics of the obtained polyethylene porous substrate 1 are shown in Table 1 below.

-Preparation of separator sample-
PMIA prepared above and an inorganic filler made of magnesium hydroxide having an average particle diameter of 0.8 μm (Kisuma 5 manufactured by Kyowa Chemical Co., Ltd.) were mixed so as to have a mass ratio of 50:50. This mixture is added to a mixed solvent in which dimethylacetamide (DMAc) and tripropylene glycol (TPG) are mixed at a 50:50 [mass ratio] so that the PMIA concentration is 5.5% by mass. A slurry was obtained.
A pair of Meyer bars (counter # 6) is opposed to each other with a clearance of 20 μm, an appropriate amount of the slurry for coating is placed on the Mayer bar, and the polyethylene porous substrate 1 is passed between the pair of Mayer bars. Then, a slurry for coating was applied to both surfaces of the polyethylene porous substrate 1. The coated material was immersed in a coagulation liquid having a composition of water: DMAc: TPG = 50: 25: 25 [mass ratio] and adjusted to 40 ° C. Next, washing and drying were performed.
In this way, a separator sample in which a heat-resistant porous layer having a thickness of 4 μm was formed on both surfaces (front and back surfaces) of the polyethylene porous substrate 1 was produced.

  Using the obtained separator sample, the mechanical strength, shutdown characteristics, short circuit resistance under high temperature (nail penetration test), and film breakage test were evaluated. The evaluation results are shown in Table 1 below.

(Examples 2-3, Comparative Examples 1-6)
In Example 1, except that the kind and amount of the polyethylene (PE) material used for the production of the polyethylene porous substrate 1, the temperature of the polyethylene solution, and the heat setting temperature were changed as shown in Table 1 below. A polyethylene porous substrate was produced in the same manner as in Example 1, and a separator sample was produced.

As shown in Table 1, in the examples, high mechanical strength was obtained while maintaining the shutdown characteristics in a predetermined temperature range, the nail penetration test was good, and excellent short-circuit resistance was exhibited even at high temperatures. . Moreover, the result by the film-breaking test was also favorable.

Claims (3)

A polyolefin having a characteristic viscosity of 5 × 10 ⁵ Pa · s to 5 × 10 ⁶ Pa · s and a non-Newtonian fluidity of 0.15 to 0.4 and a crystallinity of 65% to 85 % Porous substrate,
A heat-resistant porous layer provided on at least one side of the porous base material and containing a heat-resistant resin;
A separator for a nonaqueous electrolyte battery. The polyolefin is a polyethylene composition containing 5 to 90% by mass of ultrahigh molecular weight polyethylene having a weight average molecular weight of 1 million or more and high density polyethylene having a density of 0.942 g / cm ³ (JIS K 6748-1981) or more. The separator for nonaqueous electrolyte batteries according to claim 1. A non-aqueous electrolyte comprising: a positive electrode; a negative electrode; and a separator for a non-aqueous electrolyte battery according to claim 1 disposed between the positive electrode and the negative electrode, wherein an electromotive force is obtained by doping or dedoping lithium. Electrolyte battery.