JP6725251B2 - Laminated separator for non-aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery member, and non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a non-aqueous electrolyte secondary battery laminated separator, a non-aqueous electrolyte secondary battery member, and a non-aqueous electrolyte secondary battery.

Non-aqueous electrolyte secondary batteries such as lithium secondary batteries are currently widely used as batteries for devices such as personal computers, mobile phones, and personal digital assistants.

These non-aqueous electrolyte secondary batteries typified by lithium secondary batteries have a high energy density, and therefore, when an internal short circuit or an external short circuit occurs due to damage to the battery or damage to equipment using the battery, , A large current may flow and generate heat. Therefore, the non-aqueous electrolyte secondary battery is required to ensure high safety by preventing heat generation above a certain amount.

As a means of ensuring the safety of the non-aqueous electrolyte secondary battery, when abnormal heat is generated, a separator is used to shut down the passage of ions between the positive and negative electrodes to prevent further heat generation. The method of giving is general. That is, in the non-aqueous electrolyte secondary battery, when an abnormal current flows in the separator disposed between the positive electrode and the negative electrode due to an internal short circuit between the positive electrode and the negative electrode, for example. In general, a method of interrupting the current to prevent an excessive current from flowing (shutdown) to further suppress heat generation is generally used. As the separator, a membranous porous film containing a polyolefin resin as a main component, which melts at about 80 to 180° C. when abnormal heat is generated, is generally used.

In addition, there is known a technique of laminating a porous film on at least one surface of the porous film in order to improve the function of the separator made of the porous film. For example, in Patent Document 1, in order to prevent an internal short circuit of a battery, a separator, which is a microporous sheet made of a polyolefin resin, and a porous film containing an inorganic filler and a film binder may be laminated. Have been described. Then, the specular glossiness of 85° of the porous film is regulated to realize a thin and uniform porous film having excellent flexibility.

Further, in Patent Document 2, in a separator in which a composition containing insulating fine particles and an organic binder is applied to a microporous film made of polyethylene, specular glossiness of 60° is specified to prevent short circuit and reliability. We are trying to improve.

JP-A-2005-294216 (Published October 20, 2005) Japanese Unexamined Patent Publication No. 2014-17264 (Published January 30, 2014)

However, the above-mentioned Patent Documents 1 and 2 aim to improve flexibility, prevent short circuits, and improve reliability, and do not consider cycle characteristics.

The present invention has been made in view of such problems, and an object thereof is to provide a laminated separator for a non-aqueous electrolyte secondary battery that suppresses deterioration of cycle characteristics.

The present inventor, in a non-aqueous electrolyte secondary battery laminate separator comprising a porous film and a porous layer, has a specular gloss of 60° on the surface of the porous layer and a non-aqueous electrolyte solution having a volume basis weight of the porous layer. Focusing on the relationship with the cycle characteristics of the secondary battery for the first time, by finding that the specular glossiness and the volume basis weight are within a predetermined range, it is possible to suppress the deterioration of the cycle characteristics of the non-aqueous electrolyte secondary battery, The present invention has been completed.

The non-aqueous electrolyte secondary battery multilayer separator according to the present invention is for solving the above-mentioned problems, and includes a porous film containing a polyolefin-based resin and a porous layer. A laminated separator for a secondary battery, wherein the surface of the porous layer has a specular gloss at 60° of 3 to 26%, and the volume basis weight of the porous layer is 0.1 to 2.5 cm ³ /m ² . It is characterized by

Furthermore, in the laminated separator for a non-aqueous electrolyte secondary battery according to the present invention, it is preferable that the porous layer contains a filler.

Furthermore, in the laminated separator for a non-aqueous electrolyte secondary battery according to the present invention, the porous layer contains a filler and a resin, and the proportion of the filler in the total amount of the filler and the resin is 50 to 99 mass. % Is preferable.

Further, in the non-aqueous electrolyte secondary battery laminated separator according to the present invention, it is preferable that the puncture strength of the porous film is 2 N or more.

Further, in the laminated separator for a non-aqueous electrolyte secondary battery according to the present invention, it is preferable that the porous film has an average pore diameter of 0.14 μm or less.

The member for non-aqueous electrolyte secondary battery according to the present invention is characterized in that the positive electrode, the above-mentioned laminated separator for non-aqueous electrolyte secondary battery, and the negative electrode are arranged in this order.

A non-aqueous electrolyte secondary battery according to the present invention is characterized by including the above-mentioned laminated separator for non-aqueous electrolyte secondary battery.

According to the present invention, there is an effect of suppressing deterioration of cycle characteristics of a non-aqueous electrolyte secondary battery.

One embodiment of the present invention will be described below, but the present invention is not limited to this. The present invention is not limited to each configuration described below, various modifications are possible within the scope shown in the claims, and the technical means disclosed in different embodiments are appropriately combined. The obtained embodiments are also included in the technical scope of the present invention. Unless otherwise specified in this specification, “A to B” representing a numerical range means “A or more and B or less”.

[1. Non-aqueous electrolyte secondary battery laminated separator]
The non-aqueous electrolyte secondary battery laminated separator according to the present invention is disposed between the positive electrode and the negative electrode in the non-aqueous electrolyte secondary battery, and a film-like porous film containing a polyolefin resin as a main component, And a porous layer laminated on at least one surface of the porous film.

[1-1. Porous film]
The porous film may be any porous and membranous base material (polyolefin-based porous base material) containing a polyolefin-based resin as a main component, and has a structure having pores connected to the inside thereof. It is a film that allows gas or liquid to permeate from the surface to the other surface. That is, the porous film in the present invention is a film having pores and is different from a nonwoven fabric in which fibers are folded.

The porous film is melted when the battery generates heat, and by making the non-aqueous electrolyte secondary battery separator non-porous, it gives a shutdown function to the non-aqueous electrolyte secondary battery separator. obtain. The porous film may be composed of one layer or may be formed of a plurality of layers.

The volume-based porosity of the porous film is 0.2 to 0 so as to increase the retention amount of the electrolytic solution and to surely prevent (shut down) the flow of an excessive current at a lower temperature. It is preferably 0.8 (20 to 80% by volume), and more preferably 0.3 to 0.75 (30 to 75% by volume). Further, the average diameter of the pores (average pore diameter) of the porous film can obtain sufficient ion permeability when used as a separator, and prevents the entry of particles into the positive electrode or the negative electrode. Therefore, the thickness is preferably 0.14 μm or less, more preferably 0.1 μm or less, and preferably 0.01 μm or more.

As a method for controlling the average pore size of the porous film, for example, when reducing the pore size, a method of uniformizing the dispersed state of the pore-forming agent or the phase separation agent such as an inorganic filler during the formation of the porous film, Examples thereof include a method of reducing the particle size of the inorganic filler pore opening agent, a method of stretching in a state containing a phase separating agent, and a method of stretching at a low stretching ratio. Further, as a method for controlling the porosity of the porous film, for example, in the case of obtaining a porous film having a high porosity, a method of increasing the amount of a pore-forming agent or a phase separating agent such as an inorganic filler with respect to the polyolefin resin. , A method of stretching after removing the phase separation agent, a method of stretching at a high stretching ratio, and the like.

It is considered that when the average pore diameter of the porous film decreases, the capillary force estimated to be the driving force for introducing the electrolytic solution into the pores inside the substrate increases. Further, since the average pore size is small, generation of dendrites (dendritic crystals) due to lithium metal can be suppressed.

Further, it is considered that when the porosity of the porous film increases, the volume of the polyolefin base material where the electrolyte that cannot penetrate the electrolyte is present decreases.

The puncture strength of the porous film is preferably 2N or more, more preferably 3N or more. If the puncture strength is too low, the positive and negative electrode active material particles may be used in a laminated winding operation of the positive and negative electrodes and the separator in the battery assembly process, a pressing operation of a winding group, or when the battery is externally pressured. The separator may be pierced by this, and the positive and negative electrodes may be short-circuited. The puncture strength of the porous film is preferably 10 N or less, more preferably 8 N or less.

The proportion of the polyolefin resin component in the porous film is essentially 50% by volume or more of the entire porous film, preferably 90% by volume or more, and more preferably 95% by volume or more. The polyolefin resin component of the porous film preferably contains a high molecular weight component having a weight average molecular weight of 5×10 ⁵ to 15×10 ⁶ . In particular, the inclusion of a polyolefin component having a weight average molecular weight of 1,000,000 or more as the polyolefin component of the porous film increases the strength of the entire porous film (that is, the separator for the non-aqueous electrolyte secondary battery), which is preferable.

Examples of the polyolefin resin include high molecular weight homopolymers or copolymers obtained by polymerizing ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene and the like. The porous film may be a layer containing these polyolefins alone and/or a layer containing two or more of these polyolefins. In particular, high molecular weight polyethylene mainly composed of ethylene is preferable. In addition, the porous film does not prevent inclusion of components other than the polyolefin as long as the function of the layer is not impaired.

The air permeability of the porous film is usually in the range of Gurley value of 30 to 500 seconds/100 cc, preferably 50 to 300 seconds/100 cc. When the porous film has an air permeability within the above range, sufficient ion permeability can be obtained when it is used as a separator.

The thickness of the porous film is appropriately determined in consideration of the number of laminated non-aqueous electrolyte secondary battery laminated separators. In particular, since a porous layer is formed on one surface (or both surfaces) of the porous film, it is preferably 4 to 40 μm, more preferably 7 to 30 μm. Further, the basis weight of the porous film can increase strength, film thickness, handleability and weight, and further the weight energy density and volume energy density of the battery when used as a separator of a non-aqueous electrolyte secondary battery. And is usually 4 to 20 g/m ² , and preferably 5 to 12 g/m ² .

A known method can be used as a method for producing such a porous film, and is not particularly limited. For example, as described in JP-A-7-29563, there may be mentioned a method of adding a pore-forming agent to a thermoplastic resin to form a film, and then removing the pore-forming agent with a suitable solvent.

Specifically, for example, when the porous film is formed of a polyolefin resin containing ultra-high molecular weight polyethylene and low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, from the viewpoint of manufacturing cost, as shown below. It is preferable to manufacture by various methods.
(1) Polyolefin resin composition obtained by kneading 100 parts by weight of ultrahigh molecular weight polyethylene, 5 to 200 parts by weight of low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, and 100 to 400 parts by weight of inorganic filler such as calcium carbonate. (2) Obtaining step (2) Forming a sheet using a polyolefin resin composition (3) Step (4) Removing inorganic filler from the sheet obtained in step (2) Obtained in step (3) A step of stretching a sheet to obtain a porous film.

[1-2. Porous layer)
The porous layer according to the present invention has a large number of pores inside and has a structure in which these pores are connected, and a gas or a liquid can pass from one surface to the other surface. It can be a layer. Further, in the present embodiment, the porous layer is provided as an outermost layer of the separator on one side or both sides of the porous film, and serves as a layer that can be bonded to the electrode.

As a result of intensive studies, the inventors of the present invention have set the specular glossiness of 60° on the surface of the porous layer to 3 to 26%, whereby the laminated separator for a non-aqueous electrolyte secondary battery containing the porous layer is formed. It was found that the deterioration of the cycle characteristics of the non-aqueous electrolyte secondary battery provided with can be suppressed. Here, the specular glossiness of 60° indicates the glossiness when the incident angle and the light receiving angle are 60°, and is measured by the measuring method defined in JIS Z8741. The specular gloss of the porous layer is a parameter related to the denseness and uniformity of the porous layer.

When the specular gloss is less than 3%, the uniformity of the porous layer is low and the ion permeability is uneven. As a result, the degree of progress of deterioration due to repeated charging and discharging is fast, and the cycle characteristics deteriorate. Therefore, by setting the specular gloss to 3% or more, it is possible to suppress the deterioration of the cycle characteristics due to the non-uniformity of the porous layer.

On the other hand, when the specular glossiness exceeds 26%, the denseness of the porous layer becomes too high, and the insoluble by-product generated by charging/discharging and the clogging of the pores by bubbles increase the internal resistance of the battery. Further, in the interface between the porous layer and the electrode, there are few places where the electrolytic solution is held, and the electrolytic solution is likely to be partially depleted by repeating charging and discharging. As a result, the ion permeability is lowered and the cycle characteristics are lowered. Therefore, by setting the specular gloss to 26% or less, it is possible to suppress deterioration of cycle characteristics due to clogging of pores due to insoluble by-products and depletion of electrolytic solution at the interface between the porous layer and the electrode. it can.

The lower limit of the specular gloss of 60° on the surface of the porous layer is preferably 4% or more, more preferably 5% or more. That is, the specular gloss is preferably 4% or more and 26% or less, and more preferably 5% or more and 26% or less. The upper limit of the specular gloss is preferably 22% or less, more preferably 18% or less.

The volume basis weight of the porous layer is 0.1 to 2.5 cm ³ /m ² . In the porous layer having a volume basis weight in the range, by setting the specular gloss at 60° to 3 to 26%, it is possible to realize the action of suppressing the deterioration of cycle characteristics. When the volume basis weight of the porous layer is less than 0.1 cm ³ /m ² , the pores are clogged with insoluble by-products and the electrolyte retaining function at the interface between the porous layer and the electrode is insufficient, resulting in cycle characteristics. There is a decrease in Further, when the volume basis weight of the porous layer exceeds 2.5 cm ³ /m ² , the ion permeability of the porous layer is lowered, and the battery characteristics are lowered from the initial stage.

Specific examples of the resin forming the porous layer include polyolefins such as polyethylene, polypropylene, polybutene, and ethylene-propylene copolymer; fluorine-containing resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene; Fluorine-containing rubber such as vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer or ethylene-tetrafluoroethylene copolymer; aromatic polyamide; wholly aromatic polyamide (aramid resin); styrene-butadiene copolymer and its Hydride, methacrylic acid ester copolymer, acrylonitrile-acrylic acid ester copolymer, styrene-acrylic acid ester copolymer, ethylene propylene rubber, rubber such as polyvinyl acetate; polyphenylene ether, polysulfone, polyether sulfone, polyphenylene Resins having a melting point or glass transition temperature of 180° C. or higher such as sulfide, polyetherimide, polyamideimide, polyetheramide, polyester; polyvinyl alcohol, polyethylene glycol, cellulose ether, sodium alginate, polyacrylic acid, polyacrylamide, polymethacrylic acid. Water-soluble polymers and the like.

Specific examples of the aromatic polyamide include poly(paraphenylene terephthalamide), poly(metaphenylene isophthalamide), poly(parabenzamide), poly(metabenzamide), poly(4,4′). -Benzanilide terephthalamide), poly(paraphenylene-4,4'-biphenylene dicarboxylic acid amide), poly(metaphenylene-4,4'-biphenylene dicarboxylic acid amide), poly(paraphenylene-2,6-naphthalene dicarboxylic acid) Acid amide), poly(metaphenylene-2,6-naphthalenedicarboxylic acid amide), poly(2-chloroparaphenylene terephthalamide), paraphenylene terephthalamide/2,6-dichloroparaphenylene terephthalamide copolymer, metaphenylene Examples thereof include a terephthalamide/2,6-dichloroparaphenylene terephthalamide copolymer. Of these, poly(paraphenylene terephthalamide) is more preferable.

Among the above resins, a fluorine-containing resin and an aromatic polyamide are more preferable, and among the fluorine-containing resins, polyvinylidene fluoride (PVDF), a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), and the like are used. A polyvinylidene fluoride resin is more preferable, and PVDF is even more preferable.

The porous layer may include a filler. Examples of the filler that may be contained in the porous layer include a filler made of an organic material and a filler made of an inorganic material. Specific examples of the organic filler include homopolymers of monomers such as styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, and methyl acrylate, or two or more kinds thereof. Copolymers of polytetrafluoroethylene, tetrafluoroethylene, tetrafluoroethylene-6-fluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, fluorine-containing resins such as polyvinylidene fluoride, melamine resin, urea resin, polyethylene; Examples of the filler include polypropylene; polyacrylic acid, polymethacrylic acid; and the like. Specific examples of the inorganic filler include, for example, calcium carbonate, talc, clay, kaolin, silica, hydrotalcite, diatomaceous earth, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, aluminum hydroxide, Examples of the filler include inorganic substances such as magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, titanium nitride, alumina (aluminum oxide), aluminum nitride, mica, zeolite and glass. Only one type of filler may be used, or two or more types may be used in combination.

Of the above-mentioned fillers, fillers made of inorganic material, which are generally referred to as fillers, are preferable, and fillers made of inorganic oxides such as silica, calcium oxide, magnesium oxide, titanium oxide, alumina, mica and zeolite are more preferable. More preferred is at least one filler selected from the group consisting of silica, magnesium oxide, titanium oxide, and alumina, and alumina is particularly preferred. There are many crystal forms of alumina, such as α-alumina, β-alumina, γ-alumina, and θ-alumina, and any of them can be preferably used. Among these, α-alumina is most preferable because it has particularly high thermal stability and chemical stability.

The various fillers may be used alone or in combination of two or more.

The volume average particle diameter of the filler is preferably 0.01 μm to 10 μm from the viewpoint of ensuring good adhesiveness and slipperiness and the moldability of the separator. The lower limit value is more preferably 0.1 μm or more, and the upper limit value is more preferably 5 μm or less.

The particle shape of the filler is arbitrary, and may be spherical, elliptical, plate-shaped, rod-shaped, or amorphous. From the viewpoint of preventing a battery short circuit, plate-like particles and non-aggregated primary particles are preferable.

The filler can improve the slipperiness by forming fine unevenness on the surface of the porous layer, but when the filler is a plate-like particle or a non-aggregated primary particle, the filler is porous. The unevenness formed on the surface of the texture layer becomes finer, and the adhesiveness with the electrode is better.

In the porous layer, the proportion of the filler in the total amount of the resin and the filler is 5% by mass to 99% by mass, more preferably 10% by mass to 99% by mass, further preferably 25% by mass to 99% by mass, particularly A preferable filler ratio is 50% by mass to 99% by mass. When the proportion of the filler is less than 5% by mass, the proportion of the filler in the porous layer is low, the filler is unevenly distributed at the time of coating, and as a result, the uniformity of the porous layer may be deteriorated. It becomes difficult for the filler to exhibit the imparting function such as the property. On the other hand, when the proportion of the filler exceeds 99% by mass, the proportion of the resin in the porous layer is lowered, so that the binding property between the fillers is deteriorated, and the problem such as the dropping of the filler during handling occurs.

The average film thickness of the porous layer is preferably 0.5 μm to 10 μm on one surface of the porous film, and more preferably 1 μm to 5 μm, from the viewpoint of ensuring adhesiveness to the electrode and high energy density. ..

The porous layer preferably has a sufficiently porous structure from the viewpoint of ion permeability. Specifically, the porosity is preferably 30% to 60%. The porous layer preferably has an average pore size of 20 nm to 100 nm.

The dynamic friction coefficient of the porous layer is preferably 0.1 to 0.6, more preferably 0.1 to 0.4, and even more preferably 0.1 to 0.3. The dynamic friction coefficient is a value measured by a method according to JIS K7125. Specifically, the dynamic friction coefficient in the present invention is a value measured using a surface property tester manufactured by Haydon.

[2. Method for manufacturing laminated separator for non-aqueous electrolyte secondary battery]
The laminated separator for non-aqueous electrolyte secondary batteries according to the present invention is not particularly limited as long as the laminated separator for non-aqueous electrolyte secondary batteries described above can be obtained, and can be manufactured by various methods. For example, it is manufactured by forming a porous layer containing a resin by using one of the following methods (1) to (3).

(1) After applying a coating liquid in which a resin forming the porous layer is dissolved to the surface of the porous film, the film is immersed in a deposition solvent, which is a poor solvent for the resin. A method for depositing a porous layer composed of the above resin.

(2) After coating the coating liquid in which the resin forming the porous layer is dissolved on the surface of the porous film, the liquid property of the coating liquid is changed to acidic by using a low boiling point protic acid. By depositing a porous layer composed of the resin.

(3) After being coated on the surface of the porous film with a coating liquid in which the resin forming the porous layer is dissolved, the solvent in the coating liquid is evaporated to form the resin. A method of depositing a porous layer.

Further, in the case of the above methods (1) and (2), a step of further drying the obtained laminate after the porous layer is deposited can be included.

The solvent that dissolves the resin (dispersion medium) does not adversely affect the porous film, can dissolve the resin uniformly and stably, and can disperse the filler uniformly and stably, and is not particularly limited. Absent. Specific examples of the solvent (dispersion medium) include water; lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and t-butyl alcohol; acetone, toluene, xylene, hexane, and N. -Methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and the like can be mentioned. The solvent (dispersion medium) may be used alone or in combination of two or more. In the above method, for example, when the resin forming the porous layer is a polyvinylidene fluoride (PVDF) resin, an amide solvent such as N-methylpyrrolidone is used as a solvent for dissolving the PVDF resin. Preferably, N-methylpyrrolidone is more preferable.

As the deposition solvent, for example, another solvent (hereinafter, solvent X) which is soluble in the solvent (dispersion medium) contained in the coating liquid but does not dissolve the resin contained in the coating liquid can be used. The porous film on which the coating solution is applied to form the coating film is immersed in the solvent X, and the solvent (dispersion medium) in the coating film on the porous film or the support is replaced with the solvent X, By evaporating the solvent X, the solvent (dispersion medium) can be efficiently removed from the coating liquid. Specific examples of the deposition solvent include water; lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol and t-butyl alcohol; acetone and the like. The deposition solvent may be used alone or in combination of two or more. In the above method (1), for example, when the resin forming the porous layer is a PVDF resin, the solvent for depositing the porous layer is preferably isopropyl alcohol or t-butyl alcohol.

In the method (2), examples of the low boiling point protic acid include hydrochloric acid, acetic acid and the like.

In the above method (3), a conventionally known drying method is adopted as the method of evaporating the solvent. Among them, far-infrared heating or freeze-drying has an advantage that the shape of the pores of the porous layer is less likely to collapse during precipitation, as compared with other drying methods (air drying, etc.).

In addition, the laminated separator for a non-aqueous electrolyte secondary battery according to the present invention is produced by forming a resin-containing porous layer on the surface of a porous film serving as a substrate by the method shown in (4) below. May be done.

(4) A method of forming a porous layer by applying a coating liquid prepared by dispersing the resin fine particles forming the porous layer in a dispersion medium such as water to a base material and drying and removing the dispersion medium.

In the method (4), the dispersion medium is preferably water, and the dispersion medium such as water may be diluted or replaced by immersing the laminated film before drying in a lower alcohol. The lower alcohols are preferably isopropyl alcohol or t-butyl alcohol.

Further, when the porous layer contains a filler, the coating liquid in which the resin forming the porous layer is dissolved is used to further disperse the filler, thereby providing a porous material containing the filler. Layers can be formed.

The method for applying the coating liquid to the porous film, that is, the method for forming the porous layer on the surface of the porous film that has been subjected to hydrophilic treatment as necessary is not particularly limited. In the case of laminating the porous layer on both sides of the porous film, after the porous layer is formed on one surface of the porous film, a sequential laminating method of forming the porous layer on the other surface, or the porous film The simultaneous laminating method of simultaneously forming the porous layers on both surfaces can be performed.

The thickness of the porous layer is the thickness of the coating film in a wet state (wet) after coating, the weight ratio of the resin and the filler, and the solid content concentration of the coating liquid (the sum of the resin concentration and the filler concentration). And the like can be controlled.

The method of applying the above coating liquid to the porous film is not particularly limited as long as it is a method that can achieve the required basis weight and coating area. As the coating method of the coating liquid, a conventionally known method can be adopted, and specifically, for example, a gravure coater method, a small diameter gravure coater method, a reverse roll coater method, a transfer roll coater method, a kiss coater method, a dip Examples thereof include a coater method, a knife coater method, an air doctor blade coater method, a blade coater method, a rod coater method, a squeeze coater method, a cast coater method, a bar coater method, a die coater method, a screen printing method and a spray coating method.

A normal drying device can be used for the drying. The drying temperature is a temperature at which the air permeability of the porous film does not decrease, specifically 10 to 120° C., in order to prevent the pores of the porous film from shrinking and the air permeability decreasing. It is desirable to carry out at 20 to 80°C.

The specular gloss of 60° on the surface of the porous layer is obtained by applying known treatments such as surface treatment with sandpaper, acid treatment, alkali treatment, chemical treatment with organic solvent, corona treatment, and plasma treatment to the porous surface. It can be adjusted by applying. By appropriately adopting this treatment, it is possible to manufacture a porous layer having a specular gloss of 60° of 3 to 26%. Among them, chemical treatment with an organic solvent or the like is preferable. Examples of the organic solvent include ketones such as acetone; amides such as N-methyl-2-pyrrolidone (NMP), dimethylacetamide, dimethylformamide and dimethylformamide; ethylene carbonate, propylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate and the like. Cyclic carbonates; chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and fluorine-substituted compounds thereof; cyclic esters such as γ-butyrolactone and γ-valerolactone, and the like, with diethyl carbonate being preferred. The chemical treatment with an organic solvent such as diethyl carbonate tends to increase the specular gloss of 60° on the surface of the porous layer.

[2. Non-aqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery according to the present invention is a non-aqueous secondary battery that obtains an electromotive force by doping/dedoping lithium, a positive electrode sheet, and a laminated separator for the non-aqueous electrolyte secondary battery described above. And a negative electrode sheet are laminated to form a laminated body (member for non-aqueous electrolyte secondary battery), and other configurations are not particularly limited. The non-aqueous electrolyte secondary battery is a battery element in which the negative electrode sheet and the positive electrode sheet are impregnated with the electrolyte solution in the structure facing each other through the above-mentioned laminated separator for non-aqueous electrolyte secondary battery, in the exterior material. It has an enclosed structure. The non-aqueous electrolyte secondary battery is particularly suitable for a lithium ion secondary battery. Note that the dope means occlusion, loading, adsorption, or insertion, and means a phenomenon in which lithium ions enter an active material of an electrode such as a positive electrode.

The positive electrode sheet may have a structure in which an active material layer containing a positive electrode active material and a binder resin is formed on a current collector. The active material layer may further contain a conductive auxiliary agent.

Examples of the positive electrode active material include lithium-containing transition metal oxides, and specifically, LiCoO ₂ , LiNiO ₂ , LiMn _1/2 Ni _1/2 O ₂ , LiCo _1/3 Mn _1/3 Ni _{1 /. 3 O 2, LiMn 2 O 4} , LiFePO 4, LiCo 1/2 Ni 1/2 O 2, LiAl 1/4 Ni 3/4 O 2 and the like.

Examples of the binder resin include polyvinylidene fluoride resin.
Examples of the conductive auxiliary agent include carbon materials such as acetylene black, Ketjen black, and graphite powder.

Examples of the current collector include aluminum foil, titanium foil, and stainless steel foil having a thickness of 5 μm to 20 μm.

The negative electrode sheet may have a structure in which an active material layer containing a negative electrode active material and a binder resin is formed on a current collector. The active material layer may further contain a conductive auxiliary agent. Examples of the negative electrode active material include materials that can occlude lithium electrochemically, and specific examples thereof include carbon materials; alloys of lithium with silicon, tin, aluminum, and the like.

Examples of the binder resin include polyvinylidene fluoride resin and styrene-butadiene rubber. The separator of the present invention can secure sufficient adhesiveness to the negative electrode even when styrene-butadiene rubber is used as the negative electrode binder.
Examples of the conductive auxiliary agent include carbon materials such as acetylene black, Ketjen black, and graphite powder.

Examples of the current collector include copper foil, nickel foil, and stainless steel foil having a thickness of 5 μm to 20 μm. Moreover, you may use a metallic lithium foil as a negative electrode instead of the said negative electrode.

The electrolytic solution is a solution in which a lithium salt is dissolved in a non-aqueous solvent. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , and LiClO ₄ .

The non-aqueous solvent includes all solvents generally used in non-aqueous electrolyte secondary batteries. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and fluorine-substituted compounds thereof; γ-butyrolactone, γ-valerolactone, etc. And the like. These may be used alone or in combination.

As the electrolytic solution, 0.5 M of lithium salt is mixed with a solvent in which a cyclic carbonate and a chain carbonate are mixed in a mass ratio (cyclic carbonate/chain carbonate) of 20/80 to 40/60 (more preferably 30/70). What melt|dissolved-1.5M is suitable.

Examples of the exterior material include metal cans and aluminum laminated film packs. The shape of the battery may be rectangular, cylindrical, coin-shaped or the like.

The non-aqueous electrolyte secondary battery is, for example, a laminate in which the above-described laminated separator for non-aqueous electrolyte secondary battery is arranged between a positive electrode sheet and a negative electrode sheet, and impregnated with the electrolytic solution to form an exterior material (for example, aluminum). It can be manufactured by pressing the laminated body from above the exterior material by accommodating it in a laminate film pack). At this time, in order to enhance the adhesiveness between the electrode and the laminated separator for non-aqueous electrolyte secondary battery, the press is preferably a press while heating (hot press).

The method of disposing the separator between the positive electrode sheet and the negative electrode sheet may be a method of stacking at least one layer of the positive electrode sheet, the separator, and the negative electrode in this order (so-called stack method), and the positive electrode sheet, the separator, the negative electrode sheet, the separator. Alternatively, a method of stacking in this order and winding in the length direction may be used.

The present invention will be described below with reference to examples, but the present invention is not limited thereto.

<Measurement of specular gloss>
The specular gloss is measured by using a gloss meter (PG-IIM type manufactured by Nippon Denshoku Industries Co., Ltd.), 5 sheets of KB paper (manufactured by KOKUYO Co., Ltd., product number: KB-39N) are overlaid, and the highest non-water measurement The laminated separator for electrolytic solution secondary battery was placed, and the incident angle and the light receiving angle of the laminated separator for nonaqueous electrolytic solution secondary battery were set to 60°.

In addition, if there is a resin powder or an attached substance such as an inorganic substance on the surface of the laminated separator for a non-aqueous electrolyte secondary battery, the separator may be replaced with an organic solvent such as diethyl carbonate (DEC) and/or before the specular gloss measurement if necessary. Alternatively, a pretreatment such as drying the solvent or water after immersing in water to wash and remove the deposits may be performed.

<Measurement of piercing strength>
Using a handy compression tester (Kato Tech Co., Ltd., model number: KES-G5), the porous film was fixed with a 12 mmΦ washer, and the maximum stress (N) when the pin was pierced at 200 mm/min was applied to the film. The piercing strength of The pin used had a pin diameter of 1 mmΦ and a tip of 0.5R.

<Measurement of volume basis weight of porous layer>
By measuring the basis weight (weight per 1 square meter) of the porous layer in the dry state and dividing the basis weight by the specific gravity of the porous layer at 25°C, the volume basis weight of the porous layer in the dry state ( The resin volume per square meter) was calculated.

<Production of separator>
Laminated separators for non-aqueous electrolyte secondary batteries according to Examples 1 to 4 and Comparative Examples 1 to 4 were produced as follows.

(Example 1)
As the binder resin, sodium carboxymethyl cellulose (CMC) (manufactured by Daicel Ltd.; CMC1110) was used. As the filler, fluoroapatite (manufactured by Wako Pure Chemical Industries, Ltd.; apatite FAP, hexagonal crystal) was used. The fluoroapatite, CMC, and the solvent (mixed solvent of water and isopropyl alcohol) were mixed in the following proportions. That is, 3 parts by weight of CMC was mixed with 100 parts by weight of the above fluoroapatite, and the solid content concentration (fluoroapatite+CMC) in the obtained mixed liquid was 27.7% by weight, and the solvent composition was 95% by weight of water. And the solvent was mixed so that isopropyl alcohol was 5% by weight. Thereby, a dispersion liquid was obtained. Then, the obtained dispersion liquid was subjected to high pressure dispersion (high pressure dispersion condition; 100 MPa×3 passes) using a high pressure dispersion device (manufactured by Sugino Machine Ltd.; Starburst) to obtain a coating liquid. The obtained coating liquid was applied onto a polyethylene porous film (thickness 16.5 μm, porosity 51%, average pore size 0.096 μm) by a gravure method and dried to obtain a laminated porous film (1-i ) Got. The obtained laminated porous film (1-i) was immersed in diethyl carbonate at 70° C. for 5 minutes while standing still. The film was taken out from the diethyl carbonate and dried at room temperature to obtain a laminated separator for a non-aqueous electrolyte secondary battery of Example 1. Table 1 shows the battery characteristic retention ratio after 100 cycles of the laminated separator for non-aqueous electrolyte secondary batteries of Example 1.

(Example 2)
Lamination for a non-aqueous electrolyte secondary battery of Example 2 in the same manner as in Example 1 except that fluorine-containing mica (manufactured by Wako Pure Chemical Industries, Ltd.; synthetic mica, non-swelling) was used as the filler. A separator was obtained. Table 1 shows the battery characteristic retention ratio after 100 cycles of the laminated separator for non-aqueous electrolyte secondary batteries of Example 2.

(Example 3)
A PVDF resin (manufactured by Arkema; trade name “KYNAR2801”) was dissolved in N-methyl-2-pyrrolidone by stirring at 65° C. for 30 minutes so that the solid content was 10 mass %. The obtained solution was used as a binder solution. Alumina fine particles (Sumitomo Chemical Co., Ltd.; trade name "AKP3000") were used as the filler. The alumina fine particles, the binder solution, and the solvent (N-methyl-2-pyrrolidone) were mixed in the following proportions. That is, the binder solution was mixed so that the PVDF-based resin was 90 parts by weight with respect to 10 parts by weight of the alumina particles, and the solid content concentration (alumina particles+PVDF-based resin) in the resulting mixed solution was 7% by weight. A solvent was mixed so that a dispersion was obtained. Then, the obtained dispersion was stirred and mixed twice at room temperature under the conditions of 2000 rpm and 30 seconds with an autorotation/revolution mixer (manufactured by Shinky Co., Ltd.; trade name "Awatori Kentaro"). The obtained mixed liquid was used as a coating liquid, and was applied by a doctor blade method onto a polyethylene porous film (thickness 12 μm, porosity 44%, average pore diameter 0.035 μm). The laminate (2-i) which is the obtained coated product was immersed in 2-propanol while the coating film was in a NMP wet state, and allowed to stand at 25° C. for 5 minutes to obtain a laminated porous film (2- ii) was obtained. The obtained laminated porous film (2-iii) was dipped in another solvent of 2-propanol while being wet with the immersion solvent, and allowed to stand at 25° C. for 5 minutes to obtain a laminated porous film (2-iii). .. The obtained laminated porous film (2-iii) was dried at 65° C. for 5 minutes to obtain a laminated porous film (2-iv). The obtained laminated porous film (2-iv) was immersed in diethyl carbonate at 70° C. for 1 minute while still standing. The film was taken out of the diethyl carbonate and dried at room temperature to obtain a non-aqueous electrolyte secondary battery laminated separator of Example 3. Table 1 shows the battery characteristic retention ratio after 100 cycles of the laminated separator for non-aqueous electrolyte secondary batteries of Example 3.

(Example 4)
A laminated separator for a non-aqueous electrolyte secondary battery of Example 4 was obtained by the same method as that of Example 3 except that it was immersed in diethyl carbonate at 70° C. for 15 minutes. Table 1 shows the battery characteristic retention ratio after 100 cycles of the laminated separator for non-aqueous electrolyte secondary batteries of Example 4.

(Comparative Example 1)
A PVDF resin (manufactured by Arkema; trade name “KYNAR2801”) was dissolved in N-methyl-2-pyrrolidone by stirring at 65° C. for 30 minutes so that the solid content was 7 mass %. The obtained solution was used as a coating solution and applied on a polyethylene porous film (thickness 12 μm, porosity 44%, average pore size 0.035 μm) by a doctor blade method. The laminated body (3-i) as the obtained coated product was immersed in 2-propanol while the coating film was in a NMP wet state, and allowed to stand at 25° C. for 5 minutes to form a laminated porous film (3- ii) was obtained. The obtained laminated porous film (3-ii) was dipped in another 2-propanol in a wet state of the immersion solvent and allowed to stand at 25° C. for 5 minutes to obtain a laminated porous film (3-iii). .. The obtained laminated porous film (3-iii) was dried at 65° C. for 5 minutes to obtain a laminated porous film (3-iv). The obtained laminated porous film (3-iv) was fold-wrinkled to obtain a laminated separator for a non-aqueous electrolyte secondary battery of Comparative Example 1. Table 1 shows the battery characteristic retention ratio after 100 cycles of the laminated separator for non-aqueous electrolyte secondary batteries of Comparative Example 1.

(Comparative example 2)
A PVDF resin (manufactured by Arkema; trade name “KYNAR2801”) was dissolved in N-methyl-2-pyrrolidone by stirring at 65° C. for 30 minutes so that the solid content was 7 mass %. The obtained solution was used as a coating solution and applied on a polyethylene porous film (thickness 12 μm, porosity 44%, average pore size 0.035 μm) by a doctor blade method. The obtained laminated product (4-i) was dried at 85° C. for 5 minutes to obtain a non-aqueous electrolyte secondary battery laminated separator of Comparative Example 2. Table 1 shows the battery characteristic retention ratio after 100 cycles of the laminated separator for non-aqueous electrolyte secondary batteries of Comparative Example 2.

(Comparative example 3)
A PVDF resin (manufactured by Arkema; trade name “KYNAR2801”) was dissolved in N-methyl-2-pyrrolidone by stirring at 65° C. for 30 minutes so that the solid content was 0.3% by mass. .. The obtained solution was used as a coating solution and applied on a polyethylene porous film (thickness 12 μm, porosity 44%, average pore size 0.035 μm) by a doctor blade method. The laminate (5-i), which is the obtained coated product, was immersed in 2-propanol with the coating film remaining in the NMP wet state, and allowed to stand at 25° C. for 5 minutes to obtain a laminated porous film (5-ii). ) Got. The obtained laminated porous film (5-ii) was immersed in another solvent of 2-propanol in a state of being wet with an immersion solvent, and allowed to stand at 25° C. for 5 minutes to obtain a laminated porous film (5-iii). .. The obtained laminated porous film (5-iii) was dried at 65° C. for 5 minutes to obtain a laminated separator for a non-aqueous electrolyte secondary battery of Comparative Example 3. Table 1 shows the battery property retention ratio after 100 cycles of the laminated separator for non-aqueous electrolyte secondary batteries of Comparative Example 3.

(Comparative Example 4)
As the binder resin, sodium carboxymethyl cellulose (CMC) (manufactured by Daicel Ltd.; CMC1110) was used. As the filler, hydroxyapatite (manufactured by Wako Pure Chemical Industries, Ltd.; apatite HAP, monoclinic) was used. The hydroxyapatite, CMC, and the solvent (mixed solvent of water and isopropyl alcohol) were mixed in the following proportions. That is, 3 parts by weight of CMC was mixed with 100 parts by weight of the above fluoroapatite, and the solid content concentration (hydroxyapatite+CMC) in the resulting mixed solution was 27.7% by weight, and the solvent composition was 95% by weight of water. And the solvent was mixed so that isopropyl alcohol was 5% by weight. Thereby, a dispersion liquid was obtained. Then, the obtained dispersion liquid was subjected to high pressure dispersion (high pressure dispersion condition; 100 MPa×3 passes) using a high pressure dispersion device (manufactured by Sugino Machine Ltd.; Starburst) to obtain a coating liquid. A porous film of polyethylene (thickness: 16.5 μm, porosity: 51%, average pore size: 0.096 μm) was used so that the resulting coating liquid had a volume basis weight of the resulting porous layer of 7.52 cm ³ /m ^2. The above was applied by a gravure method and dried to obtain a laminated separator for a non-aqueous electrolyte secondary battery of Comparative Example 4. Table 1 shows the battery characteristic retention ratio after 100 cycles of the laminated separator for non-aqueous electrolyte secondary batteries of Comparative Example 4.

<Preparation of non-aqueous electrolyte secondary battery>
Next, a non-aqueous electrolyte secondary battery was produced as follows using each of the laminated separators for non-aqueous electrolyte secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 4 produced as described above.

(Positive electrode)
A commercially available positive electrode manufactured by applying LiNi _0.5 Mn _0.3 Co _0.2 O ₂ /conductive material/PVDF (weight ratio 92/5/3) to an aluminum foil was used. The above positive electrode was cut into aluminum foil so that the size of the part where the positive electrode active material layer was formed was 40 mm×35 mm, and the part where the positive electrode active material layer was not formed remained with a width of 13 mm on the outer periphery. It was used as the positive electrode. The positive electrode active material layer had a thickness of 58 μm and a density of 2.50 g/cm ³ .

(Negative electrode)
A commercially available negative electrode manufactured by applying graphite/styrene-1,3-butadiene copolymer/sodium carboxymethyl cellulose (weight ratio 98/1/1) to a copper foil was used. A copper foil was cut off from the negative electrode so that the size of the portion where the negative electrode active material layer was formed was 50 mm×40 mm, and a portion where the width was 13 mm and the negative electrode active material layer was not formed remained on the outer periphery. The negative electrode was used. The negative electrode active material layer had a thickness of 49 μm and a density of 1.40 g/cm ³ .

(assembly)
A member for a non-aqueous electrolyte secondary battery was obtained by stacking (arranging) the positive electrode, the non-aqueous electrolyte secondary battery multilayer separator, and the negative electrode in this order in a laminate pouch. At this time, the positive electrode and the negative electrode were arranged such that the entire main surface of the positive electrode active material layer of the positive electrode was included in (covered with) the main surface of the negative electrode active material layer of the negative electrode.

Subsequently, the non-aqueous electrolyte secondary battery member was placed in a bag in which an aluminum layer and a heat seal layer were laminated, and 0.25 mL of the non-aqueous electrolyte solution was placed in this bag. The non-aqueous electrolyte solution is prepared by dissolving ethylene carbonate and LiPF ₆ having a diethyl carbonate concentration of 1.0 mol/liter in a mixed solvent of ethyl methyl carbonate, diethyl carbonate and ethylene carbonate at a volume ratio of 50:20:30 at 25° C. Was used. Then, the inside of the bag was depressurized and the bag was heat-sealed to manufacture a non-aqueous electrolyte secondary battery.

<Cycle test>
For a new non-aqueous electrolyte secondary battery that has not undergone a charge/discharge cycle, at 25°C, voltage range: 4.1 to 2.7 V, current value: 0.2 C (rated capacity based on discharge capacity of 1 hour rate The initial charging/discharging was performed for 4 cycles, with 1 cycle being the current value for discharging for 1 hour, and the same applies hereinafter).

Subsequently, at 55° C., the following formula initial battery characteristic maintenance rate (%)=(20 C discharge capacity/0.2 C discharge capacity)×100
According to the above, the initial battery characteristic retention rate was calculated.

Subsequently, 100 cycles of charging/discharging were performed at 55° C., where charging/discharging was performed at a constant current of 1 C for charging current value and 1 C for discharging current value as one cycle. Then, the following formula: battery characteristic maintenance rate (%)=(20C discharge capacity at 100th cycle/0.2C discharge capacity at 100th cycle)×100
According to the above, the battery characteristic retention rate after 100 cycles was calculated. The results are shown in Table 1.

As shown in Table 1, in the non-aqueous electrolyte secondary battery using the laminated separator for non-aqueous electrolyte secondary batteries according to Comparative Example 2 having a specular gloss of more than 26%, the initial battery property retention rate was 43%. %, and the battery property retention rate after 100 cycles was 27%, which was remarkably low. This is because when the specular glossiness exceeds 26%, the denseness of the porous layer becomes too high, the insoluble by-products and bubbles generated by charge and discharge clog pores, and the interface between the separator and the electrode. This is because the ion permeability is lowered due to the deterioration of the electrolyte retaining function.

Further, even in a non-aqueous electrolyte secondary battery using the laminated separator for non-aqueous electrolyte secondary batteries according to Comparative Example 1 having a specular gloss of less than 3%, the initial battery characteristic retention rate is 65%, and It was confirmed that the battery characteristic retention rate after 100 cycles was as low as 32%. This is because when the specular gloss is less than 3%, the uniformity of the porous layer is low and the ion permeability is uneven.

Furthermore, in the non-aqueous electrolyte secondary battery using the laminated separator for non-aqueous electrolyte secondary batteries according to Comparative Example 3 in which the volume basis weight of the porous layer is less than 0.1 cm ³ /m ² , the initial battery specific maintenance is performed. Although the rate was as high as 80%, it was confirmed that the battery characteristic retention rate after 100 cycles was as low as 35%. This is because the volume of the porous layer is too small and the effect of suppressing deterioration of cycle characteristics due to the porous layer is small.

Furthermore, in the non-aqueous electrolyte secondary battery using the laminated separator for non-aqueous electrolyte secondary batteries according to Comparative Example 4 in which the volume basis weight of the porous layer exceeds 2.5 cm ³ /m ² , the initial battery specific maintenance rate was Was as low as 63%, and the battery property retention rate after 100 cycles was as low as 15%. This is because the volume of the porous layer is too large and the ion permeability of the porous layer decreases.

On the other hand, the non-water according to Examples 1 to 4 in which the specular gloss of the surface of the porous layer is 3 to 26%, and the volume basis weight of the porous layer is 0.1 to 2.5 cm ³ /m ^2. In the non-aqueous electrolyte secondary battery using the laminated separator for the electrolyte secondary battery, the initial battery property retention rate is 70% or more, and the battery property retention rate after 100 cycles is 39% or more, which causes deterioration of cycle characteristics. It was confirmed that it could be suppressed.

Claims (9)

A porous film comprising a polyolefin resin, a non-aqueous electrolyte laminated separator for a secondary battery comprising a porous layer,
The porous layer is the outermost layer of the non-aqueous electrolyte secondary battery laminated separator,
The specular gloss of 60° on the surface of the porous layer is 3 to 26%,
The volume basis weight of the porous layer is Ri 0.1~2.5cm ³ / ^{m 2} der,
The average film thickness of the porous layer is 0.5 μm to 10 μm on one surface of the porous film,
The porous layer contains a filler and a resin,
The proportion of the filler in the total amount of the filler and the resin is 5 to 99% by mass,
The filler is at least one filler selected from the group consisting of alumina (aluminum oxide), mica, and fluoroapatite,
The volume-based porosity of the porous film is 0.2 to 0.8,
The average pore diameter of the porous film is 0.01 μm or more and 0.14 μm or less,
The air permeability of the porous film at Gurley value, 30 to 500 sec / 100 cc der Rukoto nonaqueous electrolyte secondary battery stack separator according to claim. The laminated separator for a non-aqueous electrolyte secondary battery according to claim 1, wherein the porous layer has a porosity of 30% to 60%. The porous layer, the porous least one of which is laminated on the surface, according to claim 1 or 2 for the nonaqueous electrolyte secondary battery stack separator according to the film. The resin is polyolefin, fluorine-containing resin, fluorine-containing rubber, aromatic polyamide, wholly aromatic polyamide, styrene-butadiene copolymer and its hydride, methacrylic acid ester copolymer, acrylonitrile-acrylic acid ester copolymer, At least one selected from the group consisting of a styrene-acrylic acid ester copolymer, ethylene propylene rubber, polyvinyl acetate, a resin having a melting point or a glass transition temperature of 180° C. or higher, and a water-soluble polymer . 3. The non-aqueous electrolyte secondary battery laminated separator according to any one of 3 above. The resin is at least one selected from the group consisting of a fluororesin, a fluororubber, and a water-soluble polymer, and a laminated separator for a non-aqueous electrolyte secondary battery according to claim 1. .. Non-aqueous electrolyte secondary battery stack separator according to any one of claims 1 to 5, wherein the piercing strength of the porous film is not less than 2N. The positive electrode, the non-aqueous electrolyte secondary battery stack separator, and a non-aqueous electrolyte secondary battery member which negative electrode, which are arranged in this order according to any one of claims 1-6. Non-aqueous electrolyte secondary battery comprising a nonaqueous electrolyte laminated separator for secondary battery according to any one of claims 1-6. A step of forming a porous layer on the surface of the porous film,
The specular gloss of 60° on the surface of the porous layer is adjusted by subjecting the surface of the porous layer to a chemical treatment with an organic solvent selected from a ketone, an amide, a cyclic carbonate, a chain carbonate and a cyclic ester. a step of, only including,
The porous layer has a specular gloss of 60° of 3 to 26%, an average film thickness of 0.5 μm to 10 μm on one side of the porous film, and a volume basis weight of 0.1 to 2. 5 cm ³ /m ² ,
The porous layer contains a filler and a resin,
The proportion of the filler in the total amount of the filler and the resin is 5 to 99% by mass,
The volume-based porosity of the porous film is 0.2 to 0.8,
The average pore diameter of the porous film is 0.01 μm or more and 0.14 μm or less,
The method for producing a laminated separator for a non-aqueous electrolyte secondary battery, wherein the porous film has an air permeability of 30 to 500 seconds/100 cc in Gurley value .