JP5829557B2 - Method for producing metal ion secondary battery separator - Google Patents

Description

The present invention relates to a method for producing a metal ion secondary battery separator.

A metal ion secondary battery, which is one of electrochemical elements, has a feature of high energy density. For example, a lithium ion secondary battery, which is one of them, is a mobile phone, a portable music player, a notebook personal computer. Widely used as a power source for portable electric devices such as computers. In addition, the movement to use lithium ion secondary batteries is spreading in large equipment such as electric bicycles, hybrid cars, and electric cars. In addition, other metal ion secondary batteries such as sodium ion secondary batteries have attracted attention. For this reason, metal ion secondary batteries are required to have high capacity and performance such as charge / discharge characteristics at a large current. However, since metal ion secondary batteries are generally non-aqueous batteries, compared to aqueous batteries, It is known that there is a high risk of smoking, ignition, rupture, etc., and improvement in safety is also required.

  In a metal ion secondary battery, the risk of smoke generation increases due to temperature rise due to external heat, overcharge, internal short circuit, external short circuit, and the like. These can be prevented to some extent by an external protection circuit. In addition, the polyolefin resin porous film used as a metal ion secondary battery separator melts at around 120 ° C, and the pores are blocked to block current and ion flow, thereby suppressing battery temperature rise. Is done. This is called a shutdown function. However, when the temperature rises due to external heat or when a chemical reaction occurs inside the battery due to the temperature rise, the battery temperature further rises even if the shutdown function works, and when the battery temperature reaches 150 ° C or higher, The porous film contracted, causing an internal short circuit, which could cause ignition.

  As described above, it is difficult to suppress the ignition of the battery by the shutdown function of the separator. Therefore, an inorganic pigment is formed on the surface of the polyolefin resin porous film for the purpose of suppressing internal ignition by raising the heat shrink temperature more than that of the polyolefin resin porous film, thereby preventing internal short circuit. In addition, a separator for a non-aqueous secondary battery in which a heat-resistant porous layer made of a heat-resistant resin is applied has been proposed (for example, see Patent Document 1). However, when the heat-resistant porous layer is applied, there is a problem that the internal resistance of the separator increases because the pigment or the resin in the coating liquid blocks the micropores of the porous film.

  Moreover, as a heat-resistant separator with low internal resistance, a nonwoven fabric separator composed of polyester fibers and a nonwoven fabric separator in which aramid fibers that are heat-resistant fibers are blended with polyester fibers have been proposed (see, for example, Patent Documents 2 to 4). . However, although these nonwoven fabric separators are excellent in heat shrinkability, the pore diameter is large, and internal short circuit due to contact of the bipolar active material or micro short circuit due to dendrite generated on the negative electrode is likely to occur, and it has not been practical. In order to suppress these short circuits and further improve the heat resistance, examples in which a pigment or resin is supported on a substrate such as a nonwoven fabric or a woven fabric are disclosed (for example, Patent Documents 5 to 5). 6). However, even if a pigment or resin is applied, the substrate has large pores, so coating defects called pinholes are likely to occur due to back-through of the coating liquid and repellency during the drying stage, preventing micro short circuits. Was insufficient. In addition, unevenness on the surface of the substrate causes unevenness in the coating thickness, and unevenness in internal resistance due to partial penetration of the coating liquid into the substrate increases the local load. There is also a problem that the battery tends to deteriorate and the capacity during repeated charging and discharging tends to decrease.

International Publication No. 2008/062727 Pamphlet JP 2003-123728 A JP 2007-317675 A JP 2006-19191 A JP 2005-536857 A JP 2007-157723 A

An object of the present invention, in producing a high metal ion secondary battery Ikese comparator heat resistance, excellent in coating properties, to provide a coating solution capable of forming a uniform coating film, also excellent in micro short circuit prevention And it is providing the metal ion secondary battery separator with little capacity fall even if charging / discharging is repeated.

As a result of intensive studies, the present inventors have invented a method for producing a metal ion secondary battery separator that can solve the problem. That is,
(1) Diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, boehmite, aluminum hydroxide, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, amorphous silica, calcium silicate, colloidal silica, melamine resins, urea - formaldehyde resin, polyethylene, polystyrene and ethylene - pigments and coated metal-ion secondary battery separator ing contain water selected from the group consisting of vinyl acetate In the method for producing a metal ion secondary battery separator in which a liquid is applied to a nonwoven fabric substrate and dried , the ratio of the viscosity of the coating liquid at a shear rate of 1 sec ^{−1 to} the viscosity at 10 ⁴ sec ⁻¹ (shear rate of 1 sec ⁻¹ viscosity in the viscosity ^/ 10 4 ^{sec -1} in ) Is not less 45 or more and has a viscosity at 1 sec ^-1 is 800 mPa · s or more, the content of the water-soluble component state, and are 5 wt% or less of the total solid content, metal ion rechargeable battery A method for producing a metal ion secondary battery separator , which is a non-aqueous secondary battery,
It is.

In a coating solution for a metal ion secondary battery separator containing a pigment, the ratio of the viscosity at a shear rate of 1 sec ^{−1 to} the viscosity at 10 ⁴ sec ⁻¹ of the coating solution is 45 or more, and at 1 sec ⁻¹ When the viscosity is 800 mPa · s or more, it is possible to provide a coating liquid that has excellent coating properties and can form a uniform coating film.

  Moreover, the capacity | capacitance fall at the time of repeated charging / discharging can be decreased by making content of the water-soluble component in this coating liquid into 5 mass% or less with respect to the total solid.

  By coating and drying the coating liquid on a nonwoven fabric, it is possible to obtain a metal ion secondary battery separator that is excellent in preventing micro short-circuits and that has little capacity reduction during repeated charge and discharge.

The coating liquid of the present invention contains a pigment, and the ratio of the viscosity at a shear rate of 1 sec ^{−1 to} the viscosity at 10 ⁴ sec ⁻¹ of the coating liquid is 45 or more, and the viscosity at 1 sec ⁻¹ is 800 mPa · s. -It is more than s.

  Moreover, it is preferable that content of the water-soluble component in this coating liquid is 5 mass% or less with respect to the total solid.

In order to improve the heat resistance of the separator, when a coating layer is provided by applying and drying a coating liquid containing pigment on a substrate such as a nonwoven fabric or a woven fabric, the coating liquid is exposed through or dried. In order to suppress the repellency and obtain a coating film free of pinholes, it is conceivable to increase the viscosity of the coating solution to accelerate the immobilization of the coating solution after coating. By increasing the coating liquid viscosity, partial penetration of the coating liquid into the substrate can also be suppressed. However, on the other hand, when the coating solution viscosity is increased, the leveling property of the coating solution is lowered, the film thickness is likely to be non-uniform, and there is a concern of causing deterioration during repeated charging and discharging. In the present invention, the ratio of the viscosity at a shear rate of 1 sec ^{−1 to} the viscosity at 10 ⁴ sec ⁻¹ of the coating liquid is 45 or more, and the viscosity at 1 sec ⁻¹ is 800 mPa · s or more. In addition, the inventors have found that a separator having a uniform film thickness and excellent repeatability can be obtained by suppressing the penetration of the coating liquid into the substrate and ensuring sufficient leveling properties. This is presumed that the coating liquid has sufficient fluidity and leveling under the shear at the time of coating, but when the shearing after coating becomes small, the viscosity immediately increases and immobilizes quickly. . More preferably, the viscosity at 1 sec ⁻¹ is 1000 mPa · s or higher, more preferably the ratio of the viscosity at shear rate 1 sec ^{−1 to} the viscosity at 10 ⁴ sec ⁻¹ is 70 or higher, and the viscosity at 1 sec ⁻¹ is 1000 mPa · s. s or more. The viscosity at 10 ⁴ sec ⁻¹ is preferably 10 to 30 mPa · s because good leveling properties can be obtained. The viscosity mentioned here is a measured value at a liquid temperature of 23 ° C.

  By applying the coating liquid of the present invention to a nonwoven fabric substrate, a separator having no pinholes and excellent in suppressing short-circuiting can be obtained. Moreover, since the penetration of the coating liquid into the base material is suppressed, a metal ion secondary battery separator that can obtain good discharge characteristics can be obtained without impairing the low resistance characteristic of the nonwoven fabric separator. In addition, a metal ion secondary battery separator having a uniform coating film and excellent repeatability can be obtained.

In the present invention, a method in which the ratio of the viscosity at a shear rate of 1 sec ^{−1 to} the viscosity at 10 ⁴ sec ⁻¹ of the coating liquid is 45 or more and the viscosity at 1 sec ⁻¹ is 800 mPa · s or more is arbitrarily selected. For example, the specific surface area and particle diameter of the pigment to be used can be selected, or can be adjusted with an additive such as a thickener.

  Examples of the pigment used in the present invention include diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, boehmite, aluminum hydroxide, magnesium hydroxide, titanium dioxide, sulfuric acid. Examples thereof include barium, zinc sulfate, amorphous silica, calcium silicate, colloidal silica, melamine resin, urea-formaldehyde resin, polyethylene, polystyrene, and ethylene-vinyl acetate. These may be used alone or in combination of two or more. Of these, boehmite is preferable from the viewpoint of thermal stability and coating suitability. From the viewpoint of heat resistance, the pigment contained in the coating liquid of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more in the solid content of the coating liquid.

The particle size of the pigment used in the present invention is preferably 0.1 to 10.0 μm, more preferably 0.2 to 7.5 μm, and still more preferably 0.3 to 5.0 μm. When the particle size is 0.1 μm or more, the stability of the coating liquid is increased, and when the particle size is 10.0 μm or less, a flat coating surface is easily obtained. Further, when an inorganic pigment having a particle size of 1.0 μm or less is used alone or in combination with pigments having different particle sizes, a viscosity of 800 mPa · s at 1 sec ⁻¹ is easily obtained. In addition, the average particle diameter here refers to the average particle diameter (D50) measured by a laser diffraction scattering method.

In the present invention, even when a water-soluble polymer such as polyvinyl alcohol is used as the binder, the ratio of the viscosity at a shear rate of 1 sec ^{−1 and} the viscosity at 10 ⁴ sec ⁻¹ which is a feature of the present invention is 45 or more. In addition, it becomes easy to obtain a coating liquid having a viscosity at 1 sec ⁻¹ of 800 mPa · s or more. On the other hand, the water-soluble polymer has a high water content after coating and drying, and even after passing through the cell drying process, there is a possibility of bringing water into the metal ion secondary battery cell, which is generally a non-aqueous system. There is a concern that causes deterioration. Therefore, in the present invention, the content of the water-soluble component in the coating liquid is preferably 5% by mass or less based on the total solid content, and it is preferable to use a water-dispersible resin as the main component of the binder.

  In the present invention, a water-dispersible resin can be mainly used as a binder. It is also possible to use a water-soluble resin in combination. Specific examples include, for example, styrene / butadiene copolymers, acrylonitrile / butadiene copolymers, methyl acrylate / butadiene copolymers, acrylonitrile / butadiene / styrene terpolymers, polyvinyl acetate, vinyl acetate / acrylate esters. Copolymer, ethylene / vinyl acetate copolymer, polyacrylate, styrene / acrylate copolymer, water-dispersible resin such as polyurethane, starches, hydroxymethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, gelatin, casein , Polyvinyl alcohol, modified polyvinyl alcohol, sodium alginate, polyvinyl pyrrolidone, polyacrylamide, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / Tacrylic acid terpolymer, alkali salt of polyacrylic acid, alkali salt of polymaleic acid, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, isobutylene / maleic anhydride Although water-soluble resin, such as an alkali salt of a copolymer, is mentioned, It is not limited to these. In the present invention, from the viewpoint of the internal resistance of the separator, the amount of the binder in the coating layer is preferably 20% by mass or less, more preferably 10% by mass or less in the solid content. The amount of water-soluble resin in the binder is preferably less than 50% by mass.

  In the present invention, the liquidity can be adjusted with various thickeners. Specific examples include synthetic polymers such as polyethylene glycol, polyacrylic acid, polyvinyl alcohol, vinyl methyl ether-maleic anhydride copolymer, xanthan gum, welan gum, gellan gum, guar gum, carrageenan, cellulose derivatives, dextrin, pregelatinized starch. Natural polysaccharides such as starches, etc., viscosity minerals such as montmorillonite and hectorite, and inorganic oxides such as fumed silica, fumed alumina, and fumed titania. Moreover, various additives, such as a dispersing agent and a wetting agent, can be used for the coating liquid of this invention in the range which does not impair the effect of invention.

Coating solution of the present invention, a porous film, a woven fabric, can be applied to a substrate such as a nonwoven fabric, preferably a woven fabric base material is coated on the nonwoven substrate, more preferably a nonwoven substrate Coated. As the nonwoven fabric substrate, those produced by a conventionally known method can be used. For example, what was manufactured by methods, such as the spun bond method, the melt blow method, the dry method, the wet method, and the electrospinning method, can be used.

  In the present invention, the nonwoven fabric substrate may be smoothed by calendaring or thermal calendaring for the purpose of controlling the surface and thickness of the nonwoven fabric substrate.

  As the constituent material of the nonwoven fabric substrate, polyethylene terephthalate, polybutylene terephthalate and derivatives thereof, polyester such as aromatic polyester, wholly aromatic polyester, polyolefin, acrylic, polyacetal, polycarbonate, aliphatic polyketone, aromatic polyketone, aliphatic Polyamide, aromatic polyamide, wholly aromatic polyamide, polyimide, polyamideimide, polyphenylene sulfide, polybenzimidazole, polyetheretherketone, polyethersulfone, poly (para-phenylenebenzobisthiazole), poly (para-phenylene-2, 6-benzobisoxazole), polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyurethane, and polyvinyl chloride. Wei and cellulose fibers. The non-woven fabric substrate may contain two or more of these constituent materials.

As a nonwoven fabric base material used for the metal ion secondary battery separator of this invention, it is preferable that a fabric weight is 5-30 g / m < ² >, More preferably, it is 7-20 g / m < ² >. By setting the basis weight to 5 g / m ² or more, it becomes easy to obtain uniformity as a nonwoven fabric, and by setting it to 30 g / m ² or less, the thickness is suitable for a metal ion secondary battery separator. The basis weight means the basis weight based on the method defined in JIS P 8124 (paper and paperboard—basis weight measurement method).

The coating solution of the present invention is not particularly limited in method of applying a nonwoven substrate, for example, conventional air doctor coater, a blade coater, a knife coater, a rod coater, squeeze coater, immersion coater, a gravure coater, a kiss roll coater , Die coater, reverse roll coater, transfer roll coater, spray coater and the like. In particular, an impregnation coater, a gravure coater, and a die coater are preferably used from the viewpoint of uniform coating.

In this invention, as a coating amount of a coating layer, 5-30 g / m < ² > is preferable, More preferably, it is 10-20 g / m < ² >. By making the coating amount 5 g / m ² or more, it becomes easy to sufficiently cover the surface of the nonwoven fabric base material, and it becomes easy to prevent internal short circuit. Moreover, the raise of the internal resistance of a separator can be suppressed by making a coating amount into 30 g / m < ² > or less.

  In the present invention, the method of drying after coating is not particularly limited, and a known drying method can be used. In particular, a method of drying by heating, such as a method of blowing hot air or a method of irradiating infrared rays, is productivity. Is preferably used.

In the metal ion secondary battery separator of the present invention, the basis weight of the separator is preferably 10 to 50 g / m ² , and more preferably 17 to 40 g / m ² . Moreover, 10-50 micrometers is preferable and, as for the thickness of a separator, More preferably, it is 15-40 micrometers. The density of the separator is preferably 0.4 to 1.2 g / cm ³ , more preferably 0.5 to 1.0 g / cm ³ .

  In the present invention, after coating and drying, the metal ion secondary battery separator may be smoothed by calendaring for the purpose of controlling the flatness and thickness of the coating layer surface.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In Examples,% and part are all based on mass unless otherwise specified. The coating amount is an absolutely dry coating amount. Example 1 is a reference example.

Example 1
(1) Production of Non-woven Fabric Base Material 45 parts by mass of oriented crystallized polyethylene terephthalate (PET) short fibers having a fineness of 0.06 dtex (average fiber diameter of 2.4 μm) and a fiber length of 3 mm and a fineness of 0.1 dtex (average fiber diameter of 3. 0 μm), 15 mass parts of oriented crystallized PET short fibers with a fiber length of 3 mm, fineness of 0.2 dtex (average fiber diameter 4.3 μm), and a fiber length of 3 mm PET short fibers for a single-component binder (softening point 120 ° C. , Melting point 230 ° C.) and 40 parts by mass were mixed together, disaggregated in water by a pulper, and a uniform papermaking slurry having a concentration of 1% by mass was prepared under stirring by an agitator. Using a circular paper machine, this papermaking slurry is made up by a wet method, and a PET dryer short fiber is bonded to the binder with a cylinder dryer at 120 ° C. to develop a nonwoven fabric strength, and a nonwoven fabric having a basis weight of 12 g / m ² did. Further, this nonwoven fabric was subjected to a heat treatment at a roll temperature of 185 ° C., a linear pressure of 740 N / cm, and a conveying speed of 20 m / min using a 1-nip thermal calendar composed of a metal roll and a metal roll, and a nonwoven fabric base having a thickness of 19 μm. A material was prepared. In addition, the maximum pore diameter of this nonwoven fabric base material measured using PMI palm porometer CFP-1500A was 18 micrometers.

(2) coating liquid produced a volume average particle diameter of 2.3 .mu.m, 90 parts of boehmite and a volume average particle diameter 0.3μm specific surface area ^3m 2 / g, 10 parts of boehmite having a specific surface area of ^17m 2 / g, the 1% A boehmite dispersion was prepared by dispersing in 120 parts of a 0.3% aqueous solution of carboxymethyl cellulose sodium salt having a viscosity of 200 mPa · s at 25 ° C. and stirring well. Next, 100 parts of a 0.5% aqueous solution of carboxymethylcellulose sodium salt having a viscosity of 7000 mPa · s at 25 ° C. of the 1 mass% aqueous solution is mixed and stirred, and further 100 parts of a 10% polyvinyl alcohol aqueous solution is mixed and stirred. A coating liquid was prepared.

(3) Production of separator On the nonwoven fabric substrate produced in (1), the coating liquid produced in (2) was applied and dried so that the dry coating amount was 15 g / m ^2, and the thickness was 35 μm. The metal ion secondary battery separator was obtained.

(4) Production of Battery Using the separator produced in (3), the positive electrode active material is lithium manganate, the negative electrode active material is artificial graphite, the positive and negative electrode area is 15 cm ² , and the electrolyte is lithium hexafluorophosphate. A laminate type lithium ion secondary battery having a design capacity of 30 mAh, which is a 7/3 (capacity ratio) mixed solvent solution (1 mol / L) of diethyl carbonate, was produced.

Example 2
A metal ion secondary battery separator and a lithium ion secondary battery were produced in the same manner as in Example 1 except that in the production of (2) coating liquid of Example 1, 45 parts of 100% 10% polyvinyl alcohol aqueous solution was used.

Example 3
In the preparation of the coating liquid of Example 1 (2), a metal ion secondary battery separator and the same as in Example 1 except that 11 parts of 45% styrene butadiene latex was used instead of 100 parts of 10% polyvinyl alcohol aqueous solution. A lithium ion secondary battery was produced.

Example 4
In the preparation of the coating liquid of Example 1 (2), boehmite having a volume average particle size of 2.3 μm and a specific surface area of 3 m ² / g is 80 parts, and the volume average particle size is 0.3 μm and the specific surface area of 17 m ² / g. The metal ion secondary battery separator and the lithium ion secondary were the same as in Example 1, except that 20 parts of boehmite was used, and 11 parts of 45% styrene butadiene latex was used instead of 100 parts of the 10% polyvinyl alcohol aqueous solution. A battery was produced.

Example 5
In the preparation of the coating liquid in Example 1 (2), boehmite having a volume average particle size of 2.3 μm and a specific surface area of 3 m ² / g is taken as 100 parts, and the volume average particle size is 0.3 μm and the specific surface area of 17 m ² / g. No boehmite was used. Also, 250 parts of a 0.5% aqueous solution of carboxymethylcellulose sodium salt having a viscosity of 7000 mPa · s at 25 ° C. in a 1% by weight aqueous solution is used, and 11 parts of 45% styrene butadiene latex is used instead of 100 parts of a 10% polyvinyl alcohol aqueous solution. A metal ion secondary battery separator and a lithium ion secondary battery were produced in the same manner as in Example 1 except that was used.

Comparative Example 1
In the preparation of the coating liquid in Example 1 (2), boehmite having a volume average particle size of 2.3 μm and a specific surface area of 3 m ² / g is taken as 100 parts, and the volume average particle size is 0.3 μm and the specific surface area of 17 m ² / g. No boehmite and 1% by weight aqueous solution of 0.5% aqueous solution of carboxymethylcellulose sodium salt having a viscosity of 7000 mPa · s at 25 ° C. Further, a metal ion secondary battery separator and a lithium ion secondary battery were produced in the same manner as in Example 1 except that 11 parts of 45% styrene butadiene latex was used instead of 100 parts of 10% polyvinyl alcohol aqueous solution.

Comparative Example 2
The metal ion secondary battery was prepared in the same manner as in Example 1 except that 200 parts of a 7.5% polyvinyl alcohol aqueous solution was used instead of 100 parts of the 10% polyvinyl alcohol aqueous solution in the preparation of the coating liquid of Example 1 (2). A separator and a lithium ion secondary battery were produced.

Comparative Example 3
In the preparation of the coating liquid in Example 1 (2), boehmite having a volume average particle size of 2.3 μm and a specific surface area of 3 m ² / g is taken as 100 parts, and the volume average particle size is 0.3 μm and the specific surface area of 17 m ² / g. In the same manner as in Example 1 except that 11 parts of 45% styrene butadiene latex was used in place of 100 parts of 10% polyvinyl alcohol aqueous solution instead of 100 parts of 10% polyvinyl alcohol aqueous solution, and a lithium ion secondary battery. Was made.

<Evaluation>
The coating liquid, lithium ion battery separator, and lithium ion secondary battery obtained in Examples and Comparative Examples were evaluated as follows, and the results are shown in Table 1.

[Coating fluid viscosity]
The viscosity of the prepared coating liquid at shear rates of 1 sec ⁻¹ and 10 ⁴ sec ⁻¹ was measured with MCR301 manufactured by Anton Paar, and the viscosity ratio was calculated. The measurement was performed at 23 ° C.

[Content of water-soluble components in coating liquid]
The content of the water-soluble component relative to the total solid content of the coating liquid was calculated by rounding off one decimal place. The unit is mass%.

[Variation in air resistance of separator]
About the produced separator, the Gurley air permeability resistance of arbitrary 5 places was measured, and it evaluated by the following degree as a parameter | index of the dispersion | variation in the internal resistance of a separator.
(Double-circle): The dispersion | variation in air permeability resistance is less than +/- 10% from the average value of five measurement places.
○: Variation in air resistance is ± 10% or more and ± 15% or less from the average value of the five measurement points.
(Triangle | delta): The dispersion | variation in air permeability resistance is more than +/- 15 and less than +/- 20% from the average value of five places of measurement.
X: The variation in the air resistance is ± 20% or more from the average value of the five measured points.

[Coulomb efficiency during initial charge / discharge]
About the produced battery, when it becomes 30mA constant current charge-> 4.2V constant voltage charge-> charge current 3mA, constant current discharge is carried out to 2.8V at 30mA, charge capacity and discharge capacity are measured, (Coulomb efficiency) = ( Discharge capacity) / (charge capacity) was calculated. Those with low Coulomb efficiency are considered to have a micro short circuit.

[Repetitive charge / discharge characteristics of battery]
For the manufactured battery, charge and discharge for 100 cycles in the sequence of the next cycle when 30 mA constant current charge → 4.2 V constant voltage charge → charge current 3 mA becomes 30 mA constant current discharge → 2.8 V , [1- (discharge capacity at 100th cycle / discharge capacity at 4th cycle)] × 100 (%), the capacity reduction rate was determined.

As is clear from Table 1, the ratio of the viscosity at a shear rate of 1 sec ^{−1 to} the viscosity at 10 ⁴ sec ⁻¹ of the coating liquid is 45 or more, and the viscosity at 1 sec ⁻¹ is 800 mPa · s or more. As for 1-5, compared with Comparative Examples 1-3, the uniform coating layer with few dispersion | variation in air permeability resistance is obtained. Moreover, the metal ion secondary battery separator which is excellent in the Coulomb efficiency at the time of initial charging / discharging and excellent in repeated charging / discharging characteristics is obtained.

  In addition, Example 2 in which the water-soluble component is 5% by mass or less is excellent in repeated charge / discharge characteristics as compared with Example 1 in which the water-soluble component is more than 5% by mass.

The manufacturing method of the metal ion secondary battery separator of this invention can be utilized for a metal ion polymer battery, a metal ion capacitor, etc. besides a metal ion secondary battery use.

Claims (1)

Diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, boehmite, aluminum hydroxide, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, amorphous silica, calcium silicate, colloidal silica, melamine resins, urea - formaldehyde resin, polyethylene, polystyrene and ethylene - metal ion secondary battery separator coating solution ing contain pigment and water selected from the group consisting of vinyl acetate, In the method for producing a metal ion secondary battery separator that is applied to a nonwoven fabric substrate and dried , the ratio of the viscosity at a shear rate of 1 sec ^{−1 to} the viscosity at 10 ⁴ sec ⁻¹ of the coating liquid (viscosity at a shear rate of 1 sec ⁻¹ / 10 viscosity at ⁴ sec ^-1) is 5 or more, and is the viscosity at 1 sec ^-1 is 800 mPa · s or more, the content of the water-soluble component state, and are 5 wt% or less of the total solid content, metal ion rechargeable battery nonaqueous A method for producing a metal ion secondary battery separator, which is a secondary battery.