JP7054996B2 - Manufacturing method of separator for non-aqueous secondary battery, non-aqueous secondary battery and non-aqueous secondary battery - Google Patents

Description

The present invention relates to a method for manufacturing a separator for a non-aqueous secondary battery, a non-aqueous secondary battery, and a separator for a non-aqueous secondary battery.

Non-aqueous secondary batteries represented by lithium ion secondary batteries have a high energy density and are widely used as a power source for portable electronic devices such as notebook computers, mobile phones, digital cameras, and camcorders. The role of the separator is important in ensuring the safety of this lithium-ion secondary battery, and polyethylene microporous membranes have been used from the viewpoint of high strength and shutdown function, but with the increasing energy density year by year, Heat resistance is also beginning to be required to ensure safety.

From the viewpoint of ensuring safety under such high temperatures, conventionally, as one of the techniques for improving the heat resistance of the separator, a heat-resistant porous material containing a heat-resistant resin such as a total aromatic polyamide on a porous base material made of polyolefin is used. A separator having a layer formed has been proposed (for example, Patent Document 1).
, 2).

On the other hand, with the miniaturization and weight reduction of portable electronic devices, the exterior of non-aqueous secondary batteries has been simplified and reduced in weight, and aluminum cans have been developed as exterior materials in place of stainless steel cans. In addition, aluminum laminated film packs have been developed in place of metal cans. Since this aluminum laminated film pack is soft, in a battery using the pack as an exterior material (so-called soft pack battery), the electrode and the separator are separated by an external impact and expansion and contraction of the electrode due to charge and discharge. Gap is likely to be formed between the electrodes, which not only shortens the cycle life of the battery, but also causes a short circuit between the electrodes in the worst case, which may lead to a fire accident. For this reason, a technique for enhancing the adhesion between the electrode and the separator is also beginning to be required.

As one of the techniques for enhancing the adhesive force between such a separator and an electrode, a separator having a porous layer containing a polyvinylidene fluoride-based resin on a porous substrate has been conventionally proposed (
For example, see Patent Document 3).

Japanese Patent No. 4291392 Japanese Patent No. 4364940 Japanese Patent No. 4127989

However, in the conventional techniques such as Patent Documents 1 and 2 described above, the heat-resistant resin such as all-aromatic polyamide does not exhibit adhesiveness to the electrode, so that the separator and the electrode cannot be adhered to each other. Further, in the separator described in Patent Document 3 described above, the glass transition temperature of the polyvinylidene fluoride-based resin is low, and the heat resistance may not be sufficient. That is, the conventional separators such as Patent Documents 1 to 3 do not have both the functions of heat resistance and adhesiveness to the electrode. In soft pack batteries with higher energy density, a separator that has both heat resistance and adhesiveness is important in order to improve safety at high temperatures and battery cycle life.

In particular, when manufacturing a battery, a laminate in which a separator is arranged between a positive electrode and a negative electrode may be subjected to dry heat pressing (heat pressing treatment performed without impregnating the separator with an electrolytic solution). If the separator and the electrode are well adhered by the press, it is possible to improve the manufacturing yield of the battery. Therefore, a separator having an excellent function of adhering to an electrode by a dry heat press (hereinafter referred to as dry adhesiveness) is desired.

Here, it is conceivable to combine a heat-resistant resin such as aromatic polyamide with a polyvinylidene fluoride-based resin to obtain a separator having both heat resistance and dry adhesiveness. However, the resins have an affinity for each other, and a practical separator cannot be obtained by simply combining resins having different functions. For example, since aromatic polyamide and polyvinylidene fluoride-based resin have poor affinity for each other, when these resins are mixed and coated on a substrate to obtain a composite film, the coated film can be easily obtained from the substrate. It may be peeled off or the coating film itself may be brittle, resulting in poor handleability. Further, for example, when a heat-resistant layer containing an aromatic polyamide is formed on a porous substrate and an adhesive layer containing a polyvinylidene fluoride-based resin is further formed on the heat-resistant layer to obtain a composite film.
The adhesive layer is easily peeled off from the heat-resistant layer, resulting in poor handleability. Therefore, it is necessary to design the separator in consideration of the affinity between the resins and the handleability.

In view of the above background, it is an object of the present invention to provide a separator having both heat resistance and dry adhesiveness and also having excellent handleability, and it is an object of the present invention to solve this problem.

Specific means for solving the above-mentioned problems include the following aspects.
[1] A heat-resistant adhesive porous layer containing a porous base material, a heat-resistant resin provided on one or both sides of the porous base material and having an amide structure having a glass transition temperature of 200 ° C. or higher, and an acrylic resin. A separator for non-aqueous secondary batteries, which is composed of a composite film with and.
[2] The heat-resistant adhesive porous layer has a structure in which the acrylic resin having a particle shape of 10 to 500 nm is dispersed in a porous structure made of the heat-resistant resin.
] The separator for non-aqueous secondary batteries described in.
[3] The separator for a non-aqueous secondary battery according to the above [2], wherein the acrylic resin has a glass transition temperature of 0 to 80 ° C.
[4] The heat-resistant adhesive porous layer has a structure in which the surface and / or the inner surface of the pores of the porous structure made of the heat-resistant resin is coated with the acrylic resin. The above-mentioned separator for non-aqueous secondary batteries.
[5] The separator for a non-aqueous secondary battery according to the above [4], wherein the glass transition temperature of the acrylic resin is less than 0 ° C.
[6] The heat-resistant resin is at least one selected from the group consisting of polyamide-imide, total aromatic polyamide, poly-N-vinylacetamide, polyacrylamide, and copolymerized polyetheramide. The separator for a non-aqueous secondary battery according to any one of [5].
[7] The heat-resistant adhesive porous layer contains 5 to 60% by mass of the acrylic resin with respect to the total mass of the acrylic resin and the heat-resistant resin.
]. The separator for a non-aqueous secondary battery according to any one of.
[8] The non-constant according to any one of [1] to [7] above, wherein the heat-resistant adhesive porous layer contains 5 to 80% by mass of a filler with respect to the total mass of the heat-resistant adhesive porous layer. Separator for water-based secondary batteries.
[9] The separator for a non-aqueous secondary battery according to any one of [1] to [8] above, wherein the porous substrate is a microporous polyolefin membrane containing polypropylene.
[10] The separator for a non-aqueous secondary battery according to any one of [1] to [9] above, wherein the peel strength between the porous substrate and the heat-resistant adhesive porous layer is 0.1 N / 10 mm or more. ..
[11] The non-aqueous secondary according to any one of [1] to [10] above, wherein an adhesive porous layer containing a polyvinylidene fluoride-based resin is further formed on one or both sides of the composite film. Battery separator.
[12] The above [1] to [11] arranged between the positive electrode, the negative electrode, and the positive electrode and the negative electrode.
], Which is provided with the separator for a non-aqueous secondary battery according to any one of the above, and obtains an electromotive force by doping / dedoping lithium.
[13] A heat-resistant adhesive porous layer containing a porous base material, a heat-resistant resin provided on one or both sides of the porous base material and having an amide structure having a glass transition temperature of 200 ° C. or higher, and an acrylic resin. It is a method for manufacturing a separator for a non-aqueous secondary battery made of a composite film provided with and.
(I) A step of applying a coating liquid containing a heat-resistant resin, an acrylic resin, and a solvent capable of dissolving the heat-resistant resin and the acrylic resin onto a porous substrate to form a coating layer.
(Ii) The porous substrate on which the coating layer is formed is immersed in a coagulating liquid containing a poor solvent for the heat-resistant resin and the acrylic resin, and the heat-resistant resin and the acrylic resin are induced while inducing phase separation in the coating layer. To solidify and form a porous layer on a porous substrate to obtain a composite film.
(Iii) A method for manufacturing a separator for a non-aqueous secondary battery, which comprises washing and drying the composite film with water.
[14] A heat-resistant adhesive porous layer containing a porous base material, a heat-resistant resin provided on one or both sides of the porous base material and having an amide structure having a glass transition temperature of 200 ° C. or higher, and an acrylic resin. It is a method for manufacturing a separator for a non-aqueous secondary battery made of a composite film provided with and.
(I) A step of applying a coating liquid containing a heat-resistant resin, an acrylic resin which is an aqueous emulsion, and a solvent capable of dissolving the heat-resistant resin to a porous base material to form a coating layer.
(Ii) The porous substrate on which the coating layer is formed is immersed in a coagulating liquid containing a poor solvent for the heat-resistant resin, and the heat-resistant resin is solidified while inducing phase separation in the coating layer to solidify the porous substrate. The process of forming a porous layer on top and obtaining a composite film,
(Iii) A method for manufacturing a separator for a non-aqueous secondary battery, which comprises washing and drying the composite film with water.
[15] The method for producing a separator for a non-aqueous secondary battery according to the above [14], wherein the coating liquid contains a water-soluble surfactant.

According to the present invention, it is possible to provide a separator having both heat resistance and dry adhesiveness, and also having excellent handleability.

Hereinafter, embodiments of the present disclosure will be described. These explanations and examples are examples of embodiments and do not limit the scope of the embodiments.

The numerical range indicated by using "-" in the present disclosure indicates a range including the numerical values before and after "-" as the minimum value and the maximum value, respectively.

In the present disclosure, the term "process" is included in this term not only as an independent process but also as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes.

When referring to the amount of each component in the composition in the present disclosure, if a plurality of substances corresponding to each component are present in the composition, unless otherwise specified, the plurality of species present in the composition. It means the total amount of substances.

In the present disclosure, the "mechanical direction" means the long direction in the porous base material and the separator manufactured in a long shape, and the "width direction" means the direction orthogonal to the "mechanical direction". .. In the present disclosure, the "machine direction" is also referred to as "MD direction", and the "width direction" is also referred to as "TD direction".

As used herein, the "monomer component" of a copolymer means a component of the copolymer and a component unit formed by polymerizing the monomer.

<Separator for non-water-based secondary batteries>
The separator for a non-aqueous secondary battery (also referred to as "separator") of the present disclosure is provided on one side or both sides of a porous base material and the porous base material, and has an amide structure having a glass transition temperature of 200 ° C. or higher. It is composed of a composite film provided with a heat-resistant resin having a heat-resistant resin and a heat-resistant adhesive porous layer containing an acrylic resin.

The separator of the present disclosure has both heat resistance and dry adhesiveness, and is also excellent in handleability.
Specifically, a heat-resistant resin having an amide structure having a glass transition temperature of 200 ° C. or higher can improve safety at high temperatures and reduce the heat shrinkage of the separator at, for example, 175 ° C. Further, since the acrylic resin enhances the adhesiveness with the electrode by the dry heat press, it is difficult for the acrylic resin to be displaced from the electrode in the battery manufacturing process, and the battery manufacturing yield can be improved. In addition, the good adhesion between the separator and the electrode ensures that the battery cycle characteristics (
Capacity maintenance rate) can be improved. Further, it is difficult for a gap to be formed between the electrode and the separator due to an external impact or expansion and contraction of the electrode due to charge and discharge, and it is possible to remarkably suppress an ignition accident due to a short circuit between the electrodes.
Further, in the present disclosure, since the acrylic group of the acrylic resin and the amide bond of the heat-resistant resin have a high affinity, the heat-resistant resin and the acrylic resin are bound to each other in the heat-resistant adhesive porous layer.
The heat-resistant adhesive porous layer is difficult to peel off from the porous substrate, and the heat-resistant adhesive porous layer also maintains a good porous structure, so that it has excellent handleability.

Hereinafter, each component of the separator of the present disclosure will be described in detail.

[Porous medium]
In the present disclosure, the porous base material means a base material having pores or voids inside. Examples of such a base material include a microporous film; a porous sheet made of a fibrous material such as a non-woven fabric and paper; and the like. As the porous substrate, a microporous membrane is preferable from the viewpoint of thinning and strength of the separator. A microporous membrane means a membrane that has a large number of micropores inside and has a structure in which these micropores are connected so that a gas or liquid can pass from one surface to the other. do.

As the material of the porous base material, a material having electrical insulation is preferable, and either an organic material or an inorganic material may be used.

The porous substrate preferably contains a thermoplastic resin in order to impart a shutdown function to the porous substrate. The shutdown function is a function of blocking the movement of ions by melting the constituent materials and closing the pores of the porous substrate when the battery temperature rises to prevent thermal runaway of the battery. As the thermoplastic resin, a thermoplastic resin having a melting point of less than 200 ° C. is preferable. Examples of the thermoplastic resin include polyesters such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; and the like, among which polyolefins are preferable.

As the porous substrate, a microporous membrane containing polyolefin (referred to as "polyolefin microporous membrane") is preferable. Examples of the polyolefin microporous membrane include a polyolefin microporous membrane applied to a conventional battery separator, and it is preferable to select one having sufficient mechanical properties and ion permeability.

The polyolefin microporous membrane preferably contains polyethylene from the viewpoint of exhibiting a shutdown function, and the polyethylene content is preferably 95% by mass or more of the total mass of the polyolefin microporous membrane.

Further, the polyolefin microporous film is preferably a polyolefin microporous film containing polypropylene from the viewpoint of imparting heat resistance to the extent that the film does not easily break when exposed to a high temperature. Examples of such a polyolefin microporous membrane containing polypropylene include a polyolefin microporous membrane in which the content of polypropylene is 30% by mass or more of the total mass of the microporous membrane. Further, a microporous membrane in which polyethylene and polypropylene are mixed in one layer can also be used, and in that case, the polypropylene content is 0.1 of the mass of the entire microporous membrane from the viewpoint of achieving both a shutdown function and heat resistance. It is preferably about 30% by mass. also,
From the viewpoint of achieving both a shutdown function and heat resistance, a polyolefin microporous membrane having a laminated structure of two or more layers, at least one layer containing polyethylene and at least one layer containing polypropylene is also preferable. In particular, a polyolefin microporous membrane having a laminated structure of two or more layers, at least one layer containing polyethylene and at least one layer containing polypropylene is preferable. In the separator of the present disclosure, even when such a polyolefin microporous film containing polypropylene is used as a porous base material, the heat-resistant adhesive porous layer adheres well to the base material containing polypropylene. Sufficient peel strength can be secured. Conventionally, a heat-resistant resin such as an all-aromatic polyamide has a poor affinity with polypropylene, and has a problem that it is easily peeled off between the heat-resistant resin layer and the polypropylene layer. However, in the present disclosure, the acrylic resin plays a role of ensuring the peeling force between both layers, good handling property can be ensured, and a separator having more excellent heat resistance can be obtained.

The weight average molecular weight (Mw) of the polyolefin contained in the microporous polyolefin membrane
However, 100,000 to 5 million polyolefins are preferable. When the Mw of the polyolefin is 100,000 or more, sufficient mechanical properties can be imparted to the microporous membrane. On the other hand, the Mw of polyolefin is 500.
When it is 10,000 or less, the shutdown characteristics of the microporous membrane are good, and the microporous membrane can be easily formed.

As a method for producing a microporous polyolefin film, a melted polyolefin resin is extruded from a T-die to form a sheet, which is crystallized and then stretched, and then heat-treated to form a microporous film: liquid paraffin or the like. Polyolefin resin melted with a plasticizer is T-
Examples thereof include a method of extruding from a die, cooling the sheet, forming a sheet, stretching the resin, extracting a plasticizer, and heat-treating the film to form a microporous film.

Examples of the porous sheet made of a fibrous material include polyesters such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; heat-resistant resins such as aromatic polyamides, polyimides, polyethersulfones, polysulfones, polyetherketones and polyetherimides; celluloses; Examples thereof include porous sheets such as non-woven fabrics and paper made of fibrous materials such as.

Even if the surface of the porous substrate is subjected to various surface treatments for the purpose of improving the wettability with the coating liquid for forming the porous layer, as long as the properties of the porous substrate are not impaired. good. Examples of the surface treatment include corona treatment, plasma treatment, flame treatment, ultraviolet irradiation treatment and the like.

[Characteristics of porous substrate]
In the present disclosure, the thickness of the porous substrate is 5 from the viewpoint of obtaining good mechanical properties and internal resistance.
It is preferably μm to 25 μm.

The galley value (JIS P8117: 2009) of the porous substrate is preferably 50 seconds / 100 cc to 300 seconds / 100 cc from the viewpoint of suppressing a short circuit of the battery and obtaining sufficient ion permeability.

The porosity of the porous substrate is 20% or more from the viewpoint of obtaining appropriate membrane resistance and shutdown function.
60% is preferable. The porosity of the porous substrate is determined according to the following calculation method. That is, the constituent materials are a, b, c, ..., N, and the masses of the constituent materials are Wa, Wb, Wc, ..., Wn (g).
/ Cm ² ), the true densities of each constituent material are da, db, dc, ..., Dn (g / cm ³ ), and the porosity ε (%) when the film thickness is t (cm). Is calculated from the following equation.
ε = {1- (Wa / da + Wb / db + Wc / dc + ... + Wn / dn) / t} × 100

The piercing strength of the porous substrate is preferably 300 g or more from the viewpoint of improving the manufacturing yield of the separator and the manufacturing yield of the battery. The piercing strength of the porous substrate is KES- of Kato Tech Co., Ltd.
Using the G5 handy compression tester, the radius of curvature of the needle tip is 0.5 mm and the piercing speed is 2 mm / s.
It refers to the maximum piercing load (g) measured by performing a piercing test under the condition of ec.

[Heat-resistant adhesive porous layer]
In the present disclosure, the heat-resistant adhesive porous layer is provided as the outermost layer of the separator on one side or both sides of the porous base material, and is a layer that adheres to the electrode when the separator and the electrode are overlapped and pressed or hot-pressed.

In the present disclosure, the heat-resistant adhesive porous layer has a large number of micropores inside and has a structure in which these micropores are connected so that gas or liquid can pass from one surface to the other. It has become. As such a heat-resistant adhesive porous layer, the following two types are preferable,
In the present disclosure, the porous structure is not particularly limited as long as it is a porous layer containing a heat-resistant resin and an acrylic resin.

(1) Type A: The heat-resistant adhesive porous layer has a structure in which an acrylic resin having a particle shape of 10 to 500 nm is dispersed in a porous structure made of a heat-resistant resin. specifically,
The heat-resistant resin forms a fibril-like body, and a large number of such fibril-like bodies are integrally connected to form a three-dimensional network structure, and the three-dimensional network structure has a particle shape of 10 to 500 nm. It is preferable that the structure is such that the acrylic resin is dispersed. Such a porous structure can be confirmed by, for example, a scanning electron microscope (SEM) or the like.
In the heat-resistant adhesive porous layer of type A, when the particle size of the acrylic resin is 500 nm or less, the permeability becomes good. From this point of view, the particle size of the acrylic resin is 2.
It is preferably 00 nm or less, and preferably 100 nm or less. On the other hand, when the particle size of the acrylic resin exceeds 10 nm, the adhesiveness with the electrode is improved. From this point of view, the particle size of the acrylic resin is preferably 20 nm or more, preferably 25 nm or more.
In forming a heat-resistant adhesive porous layer such as Type A, it is preferable to use an acrylic resin having a glass transition temperature of 0 to 80 ° C. as the acrylic resin.

(2) Type B: The heat-resistant adhesive porous layer has a structure in which the surface of the porous structure made of a heat-resistant resin and / or the inner surface of the pores is coated with an acrylic resin. Specifically, the heat-resistant resin forms a fibril-like body, and a large number of such fibril-like bodies are integrally connected to form a three-dimensional network structure, and the surface and / or the surface of the three-dimensional network structure is formed. It is preferable that the inner surface of the pores is covered with an acrylic resin.
In the type B heat-resistant adhesive porous layer, it is sufficient that the acrylic resin covers at least a part of the surface of the three-dimensional network structure, but from the viewpoint of improving the adhesive force with the electrode, it is preferably three-dimensional. It is more preferable to cover 50% or more, more preferably 80% or more of the surface of the network structure. Such a porous structure can be confirmed by, for example, a scanning electron microscope (SEM) or the like.
In forming a heat-resistant adhesive porous layer such as Type B, it is preferable to use an acrylic resin having a glass transition temperature of less than 0 ° C. as the acrylic resin.

It is preferable that the heat-resistant adhesive porous layer is present on both sides of the porous substrate rather than on only one side, from the viewpoint of excellent battery cycle characteristics. This is because when the heat-resistant adhesive porous layer is on both sides of the porous substrate, both sides of the separator adhere well to both electrodes via the heat-resistant adhesive porous layer. In the present disclosure, the heat-resistant adhesive porous layer may further contain a resin other than the acrylic resin and the heat-resistant resin, an inorganic filler, an organic filler, and the like, as long as the effect of the present invention is not impaired.

(Heat-resistant resin)
In the present disclosure, the heat-resistant resin having an amide structure having a glass transition temperature of 200 ° C. or higher includes, for example, a group consisting of polyamide-imide, total aromatic polyamide, poly-N-vinylacetamide, polyacrylamide, and copolymerized polyetheramide. It is preferable that it is one or more selected from the above. In particular, total aromatic polyamides (meta-type aromatic polyamides, para-aromatic polyamides) are suitable from the viewpoint of durability, and meta-type aromatics are further easily formed into a porous layer and have excellent oxidation-reduction resistance. Polyamides are preferred, especially polymetaphenylene isophthalamides.

The heat-resistant resin may be a homopolymer, and may contain some copolymerization components according to a desired purpose such as exhibiting flexibility. That is, for example, in a total aromatic polyamide, it is also possible to copolymerize, for example, a small amount of an aliphatic component.

(Acrylic resin)
In the present disclosure, the acrylic resin preferably contains an acrylic monomer consisting of one or more selected from the group consisting of acrylic acid, acrylic acid salt, acrylic acid ester, methacrylic acid, methacrylic acid, and methacrylic acid ester. Examples of the acrylate include sodium acrylate, potassium acrylate, magnesium acrylate, zinc acrylate and the like. Examples of the acrylate ester include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, 2-hydroxyethyl acrylate, and hydroxypropyl acrylate. Examples thereof include methoxypolyethylene glycol acrylate, isovonyl allylate, dicyclopentanyl acrylate, cyclohexyl acrylate, and 4-hydroxybutyl acrylate. Examples of the methacrylate include sodium methacrylate, potassium methacrylate, magnesium methacrylate, zinc methacrylate and the like. Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, and so on.
Cyclohexyl methacrylate, lauryl methacrylate, stearyl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, diethylaminoethyl methacrylate, methoxypolyethylene glycol methacrylate, isobonyl methacrylate, dicyclopentanyl methacrylate, cyclohexyl methacrylate, 4-hydroxy Examples include butyl methacrylate and the like.

Among these, acrylic monomers include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, lauryl methacrylate, stearyl methacrylate, 2-ethylhexyl methacrylate, methyl acrylate, ethyl acrylate, and isopropyl acrylate. , N-butyl acrylate, 2-hydroxyethyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, lauryl acrylate, stearyl acrylate, are preferred.

The acrylic resin may be a copolymer of the above acrylic monomer and another monomer, and examples of the other monomer include a styrene-based monomer and an unsaturated carboxylic acid anhydride.

Examples of the styrene-based monomer include styrene, metachlorostyrene, parachlorostyrene, parafluorostyrene, paramethoxystyrene, metatarsial butoxystyrene, paratertiary butoxystyrene, rosevinyl benzoic acid, paramethyl-α-methylstyrene and the like. Can be done.

Examples of the unsaturated carboxylic acid anhydride include maleic acid anhydride, itaconic acid anhydride, citraconic acid anhydride, 4-methacryloxyethyl trimellitic anhydride, trimellitic acid anhydride and the like. The addition of unsaturated carboxylic acid anhydride not only creates an intermolecular interaction with the constituents of the electrode due to its strong polarization, but also the acid anhydride skeleton reacts with the resin component in the electrode or the amine end of the heat resistant resin. In some cases, it develops a strong bond as a result.

The unsaturated carboxylic acid anhydride contained in the acrylic resin is most preferably 50% by mass or less, more preferably 40% by mass or less, and 30% by mass or less with respect to the total amount of the acrylic resin. When the amount of unsaturated carboxylic acid anhydride is 50% by mass or less with respect to the total amount of the acrylic resin, the glass transition temperature of the acrylic resin does not exceed 80 ° C., and the acrylic resin is firmly adhered to the electrode by a dry heat press. Is possible. On the other hand, when the unsaturated carboxylic acid anhydride contained in the acrylic resin is contained in an amount of 1.0% by mass or more based on the total amount of the acrylic resin, it is preferable from the viewpoint of adhesiveness. From this point of view, 5% by mass or more is more preferable, and further 10% by mass or more is particularly preferable.

The glass transition temperature of the acrylic resin used in the separator of the present disclosure is −70 ° C.
The range of -80 ° C is suitable. In general, the lower the glass transition temperature of an acrylic resin, the higher the fluidity of the adhesive porous layer during dry heat pressing. And improve the adhesion of the heat-resistant adhesive porous layer. When the glass transition temperature is −70 ° C. or higher, the heat-resistant adhesive porous layer located on the surface of the separator is less likely to cause blocking, which is preferable. When the glass transition temperature is 80 ° C. or lower, it is preferable because the adhesive effect by the dry heat press can be easily improved.
In forming a heat-resistant adhesive porous layer such as Type A, the glass transition temperature is 0 to 80 ° C.
Acrylic resin is preferable, and in forming type B, it is preferable to use an acrylic resin having a glass transition temperature of less than 0 ° C. Acrylic resins with different glass transition temperatures required for the formation of type A and type B have different copolymer composition ratios of the above-mentioned combinations of acrylic monomers, styrene monomers, unsaturated carboxylic acid anhydrides, and the like. Can be designed with. Specifically, the FOX formula is used to predict the glass transition temperature of the acrylic resin, while the solubility parameter is used to predict the electrolyte resistance and solubility of the acrylic resin in organic solvents.
The copolymer composition ratio of the combination of the acrylic monomer, the styrene monomer, the unsaturated carboxylic acid anhydride and the like may be determined.

The Mw of the acrylic resin used in the separator of the present disclosure is preferably 10,000 to 500,000. When the Mw of the acrylic resin is 10,000 or more, it is preferable in that the adhesive strength with the electrode by the dry heat press is improved. On the other hand, when the Mw of the acrylic resin is 500,000 or less, the fluidity of the adhesive porous layer becomes good at the time of dry heat pressing, which is preferable. The more preferable range of Mw of the acrylic resin is 20,000 to 300,000, and the most preferable range is 30,000 to 200,000.

The content of the acrylic resin in the heat-resistant adhesive porous layer determines the effect of the present invention.
Moreover, from the viewpoint of increasing the peel strength between the porous substrate and the heat-resistant adhesive porous layer, 5% by mass or more is preferable and 10% by mass or more is more preferable with respect to the total mass of the acrylic resin and the heat-resistant resin. It is preferable, 15% by mass or more is more preferable, and 20% by mass or more is further preferable. On the other hand, from the viewpoint of suppressing the cohesive failure of the heat-resistant adhesive porous layer, the content of the acrylic resin in the heat-resistant adhesive porous layer is 60 with respect to the total mass of the acrylic resin and the heat-resistant resin.
It is preferably 5% by mass or less, more preferably 55% by mass or less, further preferably 50% by mass or less, still more preferably 45% by mass or less.

(Other resins)
In the present disclosure, the heat-resistant adhesive porous layer may contain a resin other than the heat-resistant resin and the acrylic resin.
Other resins include fluororubber, styrene-butadiene copolymer, homopolymers or copolymers of vinylnitrile compounds (acrylonitrile, methacrylnitrile, etc.), carboxymethyl cellulose, hydroxyalkyl cellulose, polyvinyl alcohol, polyvinyl butyral, etc. Examples thereof include polyvinyl butyraldone and polyether (polyethylene oxide, polypropylene oxide, etc.).

(Filler)
In the present disclosure, the heat-resistant adhesive porous layer may contain a filler made of an inorganic substance or an organic substance for the purpose of improving the slipperiness and heat resistance of the separator. In that case, it is preferable to set the content and particle size to such an extent that the effects of the present disclosure are not impaired. As the filler, an inorganic filler is preferable from the viewpoint of improving the cell strength and ensuring the safety of the battery.

The average particle size of the filler is preferably 0.01 μm to 5 μm. The lower limit is 0.
1 μm or more is more preferable, and 1 μm or less is more preferable as the upper limit value.

As the inorganic filler, an inorganic filler that is stable to the electrolytic solution and is electrochemically stable is preferable. Specifically, for example, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, chromium hydroxide, zirconium hydride, cerium hydroxide, nickel hydroxide, etc.
Metal hydroxides such as boron hydroxide; Metal oxides such as alumina, titania, magnesia, silica, zirconia, barium titanate; carbonates such as calcium carbonate and magnesium carbonate; sulfates such as barium sulfate and calcium sulfate; Calcium acid, clay minerals such as talc; and the like. These inorganic fillers may be used alone or in combination of two or more. The inorganic filler may be surface-modified with a silane coupling agent or the like.

As the inorganic filler, at least one of metal hydroxide and metal oxide is preferable from the viewpoint of stability in the battery and ensuring the safety of the battery, and metal hydroxide is preferable from the viewpoint of imparting flame retardancy and eliminating static electricity. The material is preferable, and magnesium hydroxide is more preferable.

There is no limitation on the particle shape of the inorganic filler, and it may be a shape close to a sphere or a plate shape, but from the viewpoint of suppressing a short circuit of the battery, it should be a plate shape particle or a non-aggregated primary particle. Is preferable.

When the heat-resistant adhesive porous layer contains an inorganic filler, the content of the inorganic filler in the heat-resistant adhesive porous layer is 5 to 5 of the total amount of the total resin and the inorganic filler contained in the heat-resistant adhesive porous layer. 80% by mass is preferable. When the content of the inorganic filler is 5% by mass or more, heat shrinkage of the separator is suppressed when heat is applied, which is preferable from the viewpoint of dimensional stability. From this point of view
The content of the inorganic filler is more preferably 10% by mass or more, further preferably 20% by mass or more. On the other hand, when the content of the inorganic filler is 80% by mass or less, it is preferable from the viewpoint of ensuring the adhesion of the heat-resistant adhesive porous layer to the electrode. From this viewpoint, the content of the inorganic filler is more preferably 75% by mass or less, further preferably 70% by mass or less.

Examples of the organic filler include crosslinked acrylic resins such as crosslinked polymethylmethacrylate.
Examples thereof include crosslinked polystyrene and crosslinked urethane resin, and crosslinked polymethyl methacrylate is preferable.

(Other ingredients)
In the present disclosure, the heat-resistant adhesive porous layer is a dispersant such as a surfactant, a wetting agent, an antifoaming agent, p.
It may contain an additive such as an H modifier. The dispersant is added to the coating liquid used for coating molding of the heat-resistant adhesive porous layer for the purpose of improving dispersibility, coatability and storage stability. Wetting agents, defoaming agents, and pH adjusters are used for the purpose of improving the compatibility with the coating liquid used for coating molding of the adhesive porous layer, for example, with the porous substrate, and air biting into the coating liquid. It is added for the purpose of suppressing crowding or adjusting the pH.

[Characteristics of heat-resistant adhesive porous layer]
In the present disclosure, the thickness of the heat-resistant adhesive porous layer is preferably 0.5 μm or more, more preferably 1.0 μm or more, and the energy of the battery on one side of the porous substrate from the viewpoint of adhesion to the electrode. From the viewpoint of density, 8.0 μm or less is preferable, and 6.0 μm or less is more preferable.

When the heat-resistant adhesive porous layer is provided on both sides of the porous substrate, the difference between the thickness of the heat-resistant adhesive porous layer on one surface and the thickness of the heat-resistant adhesive porous layer on the other surface is. It is preferably 20% or less of the total thickness of both sides, and the lower the thickness, the more preferable.

The weight of the heat-resistant adhesive porous layer is preferably 0.5 g / m ² or more, more preferably 0.75 g / m ² or more, and ion permeation on one side of the porous substrate from the viewpoint of adhesion to the electrode. From the viewpoint of sex, 5.0 g / m ² or less is preferable, and 4.0 g / m ² or less is more preferable.

The porosity of the heat-resistant adhesive porous layer is preferably 30% or more from the viewpoint of ion permeability, preferably 80% or less, and more preferably 60% or less from the viewpoint of mechanical strength. The method for determining the porosity of the heat-resistant adhesive porous layer in the present disclosure is the same as the method for determining the porosity of the porous substrate.

The average pore size of the heat-resistant adhesive porous layer is preferably 10 nm or more from the viewpoint of ion permeability, and preferably 200 nm or less from the viewpoint of adhesion to the electrode. The average pore diameter of the heat-resistant adhesive porous layer in the present disclosure is calculated by the following formula, assuming that all the pores are columnar.
d = 4V / S
In the formula, d is the average pore diameter (diameter) of the heat-resistant adhesive porous layer, V is the pore volume per 1 m ² of the heat-resistant adhesive porous layer, and S is the pore surface area per 1 m ² of the heat-resistant adhesive porous layer. show.
The pore volume V per 1 m ² of the heat-resistant adhesive porous layer is calculated from the porosity of the heat-resistant adhesive porous layer. The pore surface area S per 1 m ² of the heat-resistant adhesive porous layer is determined by the following method.
First, the specific surface area of the porous substrate (m ² / g) and the specific surface area of the separator (m ² / g) are determined.
It is calculated from the amount of nitrogen gas adsorbed by applying the BET formula to the nitrogen gas adsorption method. These specific surface areas (m ² / g) are multiplied by each basis weight (g / m ² ) to calculate the pore surface area per 1 m ² of each. Then, the pore surface area per 1 m ² of the porous substrate is subtracted from the pore surface area per 1 m ² of the separator to calculate the pore surface area S per 1 m ² of the heat-resistant adhesive porous layer.

The peel strength between the porous substrate and the heat-resistant adhesive porous layer is preferably 0.10 N / 10 mm or more. When the peel strength is 0.10 N / 10 mm or more, the handleability of the separator is excellent in the battery manufacturing process. From this point of view, the peel strength is 0.20N / 10m.
M or more is more preferable, and higher is more preferable. The upper limit of the peel strength is not limited, but is usually 2.0 N / 10 mm or less.

[Other layers]
The composite film provided with the above-mentioned porous substrate and heat-resistant adhesive porous layer can be obtained on one or both sides thereof.
Further, an adhesive porous layer containing a polyvinylidene fluoride-based resin may be formed. In this case, the adhesive porous layer is expected to have the effect of further improving the adhesiveness with the electrode.

Here, when an adhesive porous layer containing a polyvinylidene fluoride-based resin is formed on a heat-resistant layer containing a heat-resistant resin such as a total aromatic polyamide, the affinity between the total aromatic polyamide and the polyvinylidene fluoride-based resin is formed. There is a problem that the adhesive porous layer is easily peeled off and the handleability is deteriorated. In this respect, in the separator of the present disclosure, the acrylic resin in the heat-resistant adhesive porous layer adheres well to the adhesive porous layer containing the polyvinylidene fluoride-based resin, so that the handleability can be improved. Moreover, it has excellent heat resistance and adhesiveness.

As the above-mentioned polyvinylidene fluoride-based resin, for example, a homopolymer of vinylidene fluoride (
That is, polyvinylidene fluoride); a copolymer of vinylidene fluoride and another copolymerizable monomer (polyvinylidene fluoride copolymer); a mixture thereof; Examples of the monomer copolymerizable with vinylidene fluoride include tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, vinyl fluoride, trichlorethylene and the like, and one or more of them should be used. Can be done. Above all, the VDF-HFP copolymer is preferable from the viewpoint of adhesiveness to the electrode. In addition, "
"VDF" refers to the vinylidene fluoride monomer component, "HFP" refers to the hexafluoropropylene monomer component, and "VDF-HFP copolymer" refers to the VDF monomer component and the HFP monomer component. It means a polyvinylidene fluoride-based resin having.

Further, it is preferable that the adhesive porous layer containing the above-mentioned polyvinylidene fluoride-based resin further contains a filler. By forming such a form, it is possible to further enhance the safety (heat resistance, nail piercing test resistance, etc.) of the separator. As the filler, the same filler as the filler in the heat-resistant adhesive porous layer described above can be used.

[Characteristics of separator]
The thickness of the separator of the present disclosure is preferably 5 μm or more from the viewpoint of mechanical strength, and is preferably 35 μm or less from the viewpoint of the energy density of the battery.

The puncture strength of the separator of the present disclosure is preferably 250 g to 1000 g, preferably 300 g to 60.
0 g is more preferable. The method for measuring the puncture strength of the separator is the same as the method for measuring the puncture strength of the porous substrate.

The porosity of the separator of the present disclosure is preferably 30% to 65%, more preferably 30% to 60%, from the viewpoint of adhesiveness to the electrode, handleability, ion permeability, and mechanical strength.

The galley value (JIS P8117: 2009) of the separator of the present disclosure is preferably 100 seconds / 100 cc to 300 seconds / 100 cc from the viewpoint of mechanical strength and battery load characteristics.

[Manufacturing method of separator]
(Manufacturing method of type A)
The above-mentioned type A separator can be produced, for example, by a wet coating method having the following steps (i) to (iii).

(I) A coating liquid containing a heat-resistant resin having an amide structure having a glass transition temperature of 200 ° C. or higher, an acrylic resin, and a solvent capable of dissolving the heat-resistant resin and the acrylic resin is applied to the porous substrate. The process of forming a coating layer.
(Ii) The porous substrate on which the coating layer is formed is immersed in a coagulating liquid containing a poor solvent of the heat-resistant resin and the acrylic resin, and the heat-resistant resin and the acrylic resin are induced while inducing phase separation in the coating layer. Is solidified to form a porous layer on a porous substrate to obtain a composite film.
(Iii) A step of washing and drying the composite membrane with water.

The coating liquid is prepared by dissolving or dispersing a heat-resistant resin having an amide structure having a glass transition temperature of 200 ° C. or higher and an acrylic resin in a solvent. When the heat-resistant adhesive porous layer contains a filler, the filler is dispersed in the coating liquid.

The solvent used for preparing the coating liquid includes a solvent that dissolves the heat-resistant resin and the acrylic resin (hereinafter, also referred to as “good solvent”). Examples of the good solvent include polar amide solvents such as N-methylpyrrolidone, dimethylacetamide, dimethylformamide and dimethylformamide.

The solvent used to prepare the coating liquid is from the viewpoint of forming a porous layer having a good porous structure.
It is preferable to include a phase separating agent that induces phase separation. Therefore, the solvent used for preparing the coating liquid is preferably a mixed solvent of a good solvent and a phase separating agent. The phase separation agent is preferably mixed with a good solvent in an amount that can secure an appropriate viscosity for coating. Phase separating agents include water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol,
Examples thereof include ethylene glycol, propylene glycol and tripropylene glycol.

The solvent used for preparing the coating liquid is a mixed solvent of a good solvent and a phase separation agent from the viewpoint of forming a good porous structure, and contains 60% by mass or more of the good solvent and 40% by mass of the phase separation agent. A mixed solvent containing% or less is preferable.

The resin concentration of the coating liquid is preferably 1% by mass to 20% by mass from the viewpoint of forming a good porous structure. In particular, the heat-resistant resin having an amide structure and the acrylic resin are phase-separated into two phases at a high temperature in a mixed solvent of a good solvent and a phase separating agent, and become one phase that is compatible at a low temperature near room temperature, so-called L.
It may be a CST (low temperature critical co-solution temperature) type phase diagram. When producing the separator of the present invention, it is preferable to use a one-phase or two-phase coating liquid in a translucent state and in a partially compatible state. The heat-resistant resin and the acrylic resin are coated on the porous substrate in such a compatible or partially compatible state and separated into a solidified phase, whereby 10 to 10 to 10 in the three-dimensional network structure of the heat-resistant resin.
Acrylic resin having a particle shape of 500 nm can form a dispersed structure. From such a viewpoint, the resin concentration of the coating liquid is preferably 2 to 13% by mass, more preferably 3 to 10% by mass.

Examples of the means for applying the coating liquid to the porous substrate include a Meyer bar, a die coater, a reverse roll coater, a gravure coater and the like. When the porous layer is formed on both sides of the porous base material, it is preferable to apply the coating liquid to the base material at the same time on both sides from the viewpoint of productivity.

The coagulation liquid may be water alone, but generally contains water and the good solvent and phase separation agent used in the preparation of the coating liquid. It is preferable in terms of production that the mixing ratio of the good solvent and the phase separating agent is adjusted to the mixing ratio of the mixed solvent used for preparing the coating liquid. The content of water in the coagulation liquid is preferably 40% by mass to 90% by mass from the viewpoint of forming a porous structure and productivity. The temperature of the coagulant is, for example, 20 ° C to 50 ° C.

The separator of the present invention is produced by washing the solidified separator with water and drying it. The heat-resistant adhesive porous layer of the separator obtained after washing with water has a structure in which an acrylic resin having a particle shape of 10 to 500 nm is dispersed in a three-dimensional network structure of aromatic polyamide. When the glass transition temperature of the acrylic resin is 0 to 80 ° C., the structure after washing with water is almost maintained even after drying. The drying temperature is preferably 55 to 105 ° C.

(Manufacturing method of type B)
The above-mentioned type B separator can be manufactured by using an acrylic resin having a glass transition temperature of less than 0 ° C. as the acrylic resin in the above-mentioned type A manufacturing method. Acrylic resins with a glass transition temperature of less than 0 ° C often contain long-chain alkyl groups in the molecular skeleton, and the surface tension of the acrylic resin itself tends to decrease, compared to heat-resistant resins having an amide skeleton. May also have low surface tension. Therefore, when the acrylic resin itself is subjected to high temperature treatment in the drying step, the acrylic resin itself induces spontaneous wetting, resulting in a heat-resistant adhesive porous layer having a structure that covers the surface of the three-dimensional network structure of the heat-resistant resin.

The type B separator can also be manufactured by other methods, for example, the following steps (
It can be produced by a wet coating method having i) to (iii). The description of the parts common to the above-mentioned type A manufacturing conditions will be omitted.
(I) A coating liquid containing a heat-resistant resin having an amide structure having a glass transition temperature of 200 ° C. or higher, an acrylic resin which is an aqueous emulsion, and a solvent capable of dissolving the heat-resistant resin is applied to the porous substrate. The process of forming the coating layer and
(Ii) The porous substrate on which the coating layer is formed is immersed in a coagulating liquid containing a poor solvent for the heat-resistant resin, and the heat-resistant resin is solidified while inducing phase separation in the coating layer to solidify the porous substrate. The process of forming a porous layer on top and obtaining a composite film,
(Iii) A method for manufacturing a separator for a non-aqueous secondary battery, which comprises washing and drying the composite film with water.

As the solvent capable of dissolving the heat-resistant resin in the above step (i), the solvent in the above-mentioned type A production method can be used.
In this method, since water becomes a poor solvent for the coating liquid, a predetermined amount of acrylic resin cannot be added unless the solid content concentration of the aqueous emulsion is increased. Therefore, the solid content concentration of the aqueous emulsion in the coating liquid is preferably 30 to 80 wt%. Solid content concentration is 8
When it is 0 wt% or less, the aggregation of the emulsion particles can be suppressed, and the acrylic resin having a particle shape can be dispersed in the three-dimensional network structure of the heat-resistant resin. On the other hand, when the solid content concentration is 30 wt% or more, it is possible to add an amount of acrylic resin particles capable of exhibiting adhesive performance.

As the acrylic resin which is an aqueous emulsion, it is preferable that the acrylic resin has a glass transition temperature of less than 0 ° C.
The average particle size of the emulsion particles is preferably in the range of 10 to 500 nm. When the emulsion particle size is 500 nm or less, gas or liquid can pass from one surface to the other. On the other hand, when the emulsion particle size exceeds 10 nm, sufficient adhesion with the electrode can be obtained. A more preferable range of the emulsion particle size is 20 to 200 nm, more preferably 25 to 100 nm.

In this production method, since the aqueous emulsion is added to a good solvent, the surface tension of the coating liquid tends to be high. Therefore, the wettability of the coating liquid on the porous substrate is lowered, and the coating film may be peeled off from the porous substrate in the coagulation or washing step. In such a case, it is preferable to add a water-soluble surfactant to the coating liquid. If it is a water-soluble surfactant, it can be extracted in the washing step. The type of the water-soluble surfactant is not particularly limited, but the fluorine-based surfactant is more preferable in that it can reduce the surface tension of the organic solvent.

(Other manufacturing methods)
The separator of the present disclosure can also be manufactured by a dry coating method. In the dry coating method, a coating liquid containing a resin is applied to a porous base material to form a coating layer, and then the coating layer is dried to solidify the coating layer.
This is a method of forming a porous layer on a porous substrate. However, since the porous layer tends to be denser in the dry coating method than in the wet coating method, the wet coating method is preferable from the viewpoint of obtaining a good porous structure.

The separator of the present disclosure can also be produced by producing a porous layer as an independent sheet, superimposing the porous layer on a porous substrate, and laminating by thermocompression bonding or an adhesive. As a method for producing the porous layer as an independent sheet, a method of forming a porous layer on the release sheet by applying the above-mentioned wet coating method or dry coating method and peeling the release sheet from the porous layer can be mentioned. Be done.

<Non-water-based secondary battery>
The non-aqueous secondary battery of the present disclosure is a non-aqueous secondary battery that obtains an electromotive force by doping / dedoping lithium, and includes a positive electrode, a negative electrode, and a separator for the non-aqueous secondary battery of the present disclosure. Dope means occlusion, support, adsorption, or insertion, and means a phenomenon in which lithium ions enter the active material of an electrode such as a positive electrode.

The non-aqueous secondary battery of the present disclosure has, for example, a structure in which a battery element in which a negative electrode and a positive electrode face each other via a separator is enclosed in an exterior material together with an electrolytic solution. The non-aqueous secondary battery of the present disclosure is suitable for a non-aqueous electrolyte secondary battery, particularly a lithium ion secondary battery.

In the non-aqueous secondary battery of the present disclosure, the separator of the present disclosure adheres well to the electrode by dry heat pressing, so that the manufacturing yield is high and the cycle characteristics (capacity retention rate) of the battery are excellent. Further, since the heat-resistant adhesive porous layer has high heat resistance, even when the temperature of the battery becomes high, the heat shrinkage of the porous substrate is suppressed, and a battery with further improved safety can be obtained.

Hereinafter, morphological examples of the positive electrode, the negative electrode, the electrolytic solution, and the exterior material included in the non-aqueous secondary battery of the present disclosure will be described.

Examples of the embodiment of the positive electrode include a structure in which an active material layer containing a positive electrode active material and a binder resin is arranged on a current collector. The active material layer may further contain a conductive additive. Examples of the positive electrode active material include lithium-containing transition metal oxides, specifically LiCoO ₂ and the like.
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
Examples include Ni _3/4 O ₂ and the like. Examples of the binder resin include polyvinylidene fluoride-based resins and styrene-butadiene copolymers. 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, stainless steel foil and the like having a thickness of 5 μm to 20 μm.

In the non-aqueous secondary battery of the present disclosure, since the heat-resistant resin having an amide structure contained in the heat-resistant adhesive porous layer of the separator of the present disclosure has excellent oxidation resistance, the heat-resistant adhesive porous layer is used as a non-aqueous secondary battery. LiMn _1/2 Ni _1/2 O ₂ and LiCo _1/3 Mn _1/3 Ni _1/3 O that can be operated at a high voltage of 4.2 V or higher by arranging it on the positive electrode side of the battery. It is easy to apply _2nd grade.

Examples of the embodiment of the negative electrode include a structure in which an active material layer containing a negative electrode active material and a binder resin is arranged on a current collector. The active material layer may further contain a conductive additive. Examples of the negative electrode active material include materials capable of electrochemically occluding lithium, and specific examples thereof include carbon materials; alloys of silicon, tin, aluminum and the like with lithium; wood alloys, and the like. Examples of the binder resin include polyvinylidene fluoride-based resins and styrene-butadiene copolymers. Examples of the conductive auxiliary agent include carbon materials such as acetylene black, ketjen black, graphite powder, and ultrafine carbon fibers. Examples of the current collector include copper foil, nickel foil, stainless steel foil and the like having a thickness of 5 μm to 20 μm. Further, instead of the above-mentioned negative electrode, a metallic lithium foil may be used as the 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 , LiClO ₄ , and the like. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, fluoroethylene carbonate, and the like.
Cyclic carbonates such as difluoroethylene carbonate and vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate and their fluorine-substituted products; cyclic esters such as γ-butyrolactone and γ-valerolactone; and the like. These may be used alone or in combination. As the electrolytic solution, the mass ratio of cyclic carbonate and chain carbonate (cyclic carbonate: chain carbonate)
A solution obtained by mixing at 20:80 to 40:60 and dissolving 0.5 mol / L to 1.5 mol / L of the lithium salt is suitable.

Examples of the exterior material include metal cans and aluminum laminated film packs. The shape of the battery includes a square shape, a cylindrical shape, a coin shape, and the like, and the separator of the present disclosure is suitable for any shape.

As a method for manufacturing a non-aqueous secondary battery of the present disclosure, a separator is not impregnated with an electrolytic solution but is subjected to a hot press treatment (referred to as "dry heat press" in the present disclosure) to be adhered to an electrode.
After that, a manufacturing method including impregnating the separator with an electrolytic solution can be mentioned. The manufacturing method includes, for example, a laminating step of manufacturing a laminated body in which the separator of the present disclosure is arranged between a positive electrode and a negative electrode, and a dry bonding step of performing a dry heat press on the laminated body to bond the electrode and the separator. It has a post-process of injecting an electrolytic solution into a laminate housed in the exterior material and sealing the exterior material.

In the laminating step, the method of arranging the separator between the positive electrode and the negative electrode may be a method of laminating at least one layer of the positive electrode, the separator, and the negative electrode in this order (so-called stack method), and the positive electrode, the separator, the negative electrode, and the separator are used. A method of stacking them in order and winding them in the length direction may also be used.

The dry bonding step may be performed before accommodating the laminate in the exterior material (for example, a pack made of an aluminum laminated film), or may be performed after accommodating the laminate in the exterior material. That is, the laminate in which the electrodes and the separator are adhered by a dry heat press may be accommodated in the exterior material.
After the laminate is housed in the exterior material, a dry heat press may be performed on the exterior material to bond the electrode and the separator.

The press temperature in the dry bonding step is preferably 70 ° C to 120 ° C, and is preferably 75 ° C to 110 ° C.
° C is more preferred, and 80 ° C to 100 ° C is even more preferred. Within this temperature range, the adhesion between the electrode and the separator is good, and the separator can expand appropriately in the width direction, so that a short circuit of the battery is unlikely to occur.
The press pressure in the dry bonding process is 0.5 kg to 4 as a load per 1 cm ² of the electrode.
0 kg is preferable. The press time is preferably adjusted according to the press temperature and the press pressure, and is adjusted in the range of, for example, 0.1 minute to 60 minutes.

In the above manufacturing method, the laminate may be temporarily bonded by applying a room temperature press (pressurization at room temperature) to the laminate before dry heat pressing.

In the post-process, after performing a dry heat press, an electrolytic solution is injected into the exterior material containing the laminate to seal the exterior material. After injecting the electrolytic solution, the laminate may be further heat-pressed from above the exterior material. It is preferable that the inside of the exterior body is evacuated before sealing.
Examples of the method for sealing the exterior material include a method of adhering the opening of the exterior material with an adhesive and a method of thermocompression bonding the opening of the exterior material by heating and pressurizing.

Hereinafter, the separator and the non-aqueous secondary battery of the present disclosure will be described in more detail with reference to examples. The materials, amounts, ratios, treatment procedures, etc. shown in the following examples may be appropriately changed as long as they do not deviate from the gist of the present disclosure. Therefore, the scope of the separators and non-aqueous secondary batteries of the present disclosure should not be construed as limiting by the specific examples shown below.

<Measurement method, evaluation method>
The measurement methods and evaluation methods applied in the examples and comparative examples are as follows.

[Weight average molecular weight of resin]
For the weight average molecular weight (Mw) of the resin, a gel permeation chromatography analyzer (JASCO Corporation GPC-900) was used, and Tosoh TSKgel SUPER AWM-H was used as a column.
In this use, N, N-dimethylformamide is used as a solvent, the temperature is 40 ° C., and the flow rate is 10 ml / m.
It was measured as a polystyrene-equivalent molecular weight under the condition of in.

[Resin glass transition temperature]
The glass transition temperature of the resin is measured by differential scanning calorimetry (Differential Scan).
It was obtained from the differential scanning calorimetry curve (DSC curve) obtained by performing ing Calimetry (DSC). The glass transition temperature is the temperature at which the straight line extending the baseline on the low temperature side to the high temperature side and the tangent line of the curve of the stepped change portion and having the maximum gradient intersect.

[Film thickness of porous substrate and separator]
The film thickness (μm) of the porous substrate and separator is a contact-type thickness gauge (LITEM manufactured by Mitutoyo Co., Ltd.).
It was calculated by measuring 20 points with ATIC) and averaging them. As the measurement terminal, a columnar terminal having a diameter of 5 mm was used, and the measurement was adjusted so that a load of 7 g was applied during the measurement.

[Layer thickness of heat-resistant adhesive porous layer]
For the layer thickness (μm) of the heat-resistant adhesive porous layer, the total layer thickness on both sides was obtained by subtracting the film thickness of the porous substrate from the film thickness of the separator, and half of this was taken as the layer thickness on one side. ..

[Gare value]
The Gale value (seconds / 100cc) of the porous substrate and separator is JIS P8117: 2.
According to 009, the measurement was performed using a Gale type densometer (Toyo Seiki Co., Ltd. GB2C).

[Porosity]
The porosity (%) of the porous substrate and the heat-resistant adhesive porous layer was determined according to the following formula.
ε = {1-Ws / (ds · t)} × 100
In the formula, ε is the porosity (%), Ws is the basis weight (g / m ² ), ds is the true density (g / cm ³ ), and t.
Is the thickness (μm).

[Peeling strength between the porous substrate and the heat-resistant adhesive porous layer]
Adhesive tape was attached to one surface of the separator (when the adhesive tape was attached, the length direction of the adhesive tape was made to match the MD direction of the separator), and the separator was attached together with the adhesive tape, 1.2 cm in the TD direction.
, Cut out in the MD direction 7 cm. The adhesive tape was slightly peeled off together with the heat-resistant adhesive porous layer directly underneath, and the two separated ends were gripped by Tensilon (RTC-1210A manufactured by Orientec Co., Ltd.) to perform a T-shaped peeling test. The adhesive tape is used as a support for peeling the heat-resistant adhesive porous layer from the porous substrate. The tensile speed of the T-shaped peeling test is 20 mm / m.
In, the load (N) when the heat-resistant adhesive porous layer was peeled from the porous substrate was measured. After the start of measurement, the load from 10 mm to 40 mm was collected at 0.4 mm intervals and the average was calculated.
It was converted into a load per 10 mm width (N / 10 mm), and the measured values of three test pieces were averaged to obtain a peel strength (N / 10 mm). This peel strength was used as one index of the handleability of the separator.

[Adhesion with adhesive porous layer]
For the separators produced in the following Examples and Comparative Examples, an adhesive porous layer containing a polyvinylidene fluoride-based resin is laminated as follows, and the adhesiveness between the adhesive porous layer and the heat-resistant porous layer It was confirmed.
VDF-HFP binary copolymer, which is a polyvinylidene fluoride-based resin (ratio of HFP units 5)
.. 1% by mass, weight average molecular weight 1.13 million) is dissolved in a mixed solvent of dimethylacetamide and tripropylene glycol (dimethylacetamide: tripropylene glycol = 80: 20 [mass ratio]) so that the resin concentration is 5% by mass. bottom. Further, carbon powder having an average diameter of 1 μm was added to this solution as an inorganic filler, and the mixture was stirred until it became uniform to prepare a coating liquid. In the coating liquid, the composition ratio of the PVDF resin and the inorganic filler was 60:40 (mass ratio).
An equal amount of this coating liquid was applied to both sides of each separator prepared in Examples and Comparative Examples, and a coagulating liquid (water::
Dimethylacetamide: Tripropylene glycol = 62:30: 8 [mass ratio], temperature 4
It was immersed in (0 ° C.) and solidified. Then, this was washed with water and dried to obtain a separator having an adhesive porous layer formed on both sides of the heat-resistant adhesive porous layer.
An adhesive tape was attached to one surface of the obtained separator, and the adhesive tape was peeled off from the separator, and the adhesion between the adhesive porous layer and the heat-resistant porous layer was evaluated according to the following criteria.
A: Strong adhesion (the adhesive surface of the adhesive tape is white, no peeling has occurred between the adhesive porous layer and the heat-resistant porous layer)
B: Sufficient adhesion (the adhesive surface of the adhesive tape is entirely black and partly white, and the heat-resistant porous layer is slightly adhered to a part of the adhesive porous layer).
C: Weak adhesion (the adhesive surface of the adhesive tape is almost black, only the adhesive porous layer is peeled off)

[Adhesive strength with positive electrode: Dry heat press]
89.5 g of lithium cobalt oxide powder as a positive electrode active material, 4.5 g of acetylene black as a conductive additive, and 6 g of polyvinylidene fluoride as a binder are added to N-methyl so that the concentration of vinylidene fluoride is 6% by mass. -It was dissolved in pyrrolidone and stirred with a dual-arm mixer to prepare a slurry for a positive electrode. This slurry for a positive electrode was applied to one side of an aluminum foil having a thickness of 20 μm, dried and pressed to obtain a positive electrode having a positive electrode active material layer.

The positive electrode obtained above is cut out to a width of 1.5 cm and a length of 7 cm, and the separator is 1.8 in the TD direction.
It was cut out in cm and 7.5 cm in the MD direction. The positive electrode and the separator were overlapped and hot-pressed under the conditions of a temperature of 80 ° C., a pressure of 5.0 MPa, and a time of 3 minutes to bond the positive electrode and the separator, and this was used as a test piece. At one end in the length direction of the test piece (that is, the MD direction of the separator), the separator was slightly peeled off from the positive electrode, and the end separated into two was Tensilon (RTC manufactured by Orientec).
A T-shaped peeling test was performed by gripping it with -1210A). The tensile speed of the T-shaped peeling test is 20 mm.
Set to / min, measure the load (N) when the separator peels off from the positive electrode, and 10 after the start of measurement.
A load from mm to 40 mm was collected at intervals of 0.4 mm, the average was calculated, and the measured values of three test pieces were averaged to obtain the adhesive strength (N) of the separator.

[Adhesive strength with negative electrode]
A water-soluble dispersion containing 300 g of artificial graphite as a negative electrode active material, a modified product of a styrene-butadiene copolymer as a binder in an amount of 40% by mass, 7.5 g of a water-soluble dispersion, 3 g of carboxymethyl cellulose as a thickener, and an appropriate amount of water. The mixture was stirred with a formula mixer to prepare a slurry for a negative electrode. This slurry for a negative electrode was applied to one side of a copper foil having a thickness of 10 μm, dried and pressed to obtain a negative electrode having a negative electrode active material layer.

Using the negative electrode obtained above, a T-shaped peeling test was performed in the same manner as in the above [Adhesive strength with positive electrode: dry heat press] to determine the adhesive strength (N) of the separator.

[Heat shrinkage rate]
A sample separator was cut out in a size of 18 cm (MD direction) × 6 cm (TD direction). Points (point A, point B) 2 cm and 17 cm from the top were marked on the line that bisects the TD direction. In addition, points (point C, point D) 1 cm and 5 cm from the left were marked on the line that bisects the MD direction. A clip was attached to this (the place where the clip was attached was within 2 cm above the MD direction), and the clip was hung in an oven adjusted to 150 ° C. and heat-treated for 30 minutes under no tension. The length between the two points AB and the CD was measured before and after the heat treatment, and the heat shrinkage rate was obtained from the following formulas 4 and 5.
Heat shrinkage rate in the MD direction = {(length of AB before heat treatment-length of AB after heat treatment) / length of AB before heat treatment} × 100 ... (Equation 4)
Thermal shrinkage in the TD direction = {(length of CD before heat treatment-length of CD after heat treatment) / length of CD before heat treatment} × 100 ... (Equation 5)

[Cycle characteristics (capacity retention rate)]
Lead tabs were welded to the positive electrode and the negative electrode, and the positive electrode, the separator, and the negative electrode were laminated in this order.
This laminate is inserted into a pack made of aluminum laminated film, the inside of the pack is evacuated using a vacuum sealer and temporarily sealed, and the entire pack is hot-pressed in the laminating direction of the laminate using a hot press machine. As a result, the electrode and the separator were bonded together. The conditions for hot pressing were a temperature of 90 ° C., a load of 20 kg per 1 cm ² of electrodes, and a pressing time of 2 minutes. Next, an electrolytic solution (1 mol / L LiPF ₆ -ethylene carbonate: ethylmethyl carbonate [mass ratio 3: 7]) is injected into the pack, the laminate is impregnated with the electrolytic solution, and then the inside of the pack is used with a vacuum sealer. Was sealed in a vacuum state to obtain a battery.

The battery was charged and discharged for 500 cycles in an environment with a temperature of 40 ° C. Charging is 1C and 4.
2V constant current constant voltage charge and discharge were 1C and 2.75V cutoff constant current discharge. 5
The discharge capacity at the 00th cycle was divided by the initial capacity, the average of 10 batteries was calculated, and the obtained value (
%) Was used as the capacity retention rate.

[Load characteristics]
A battery was manufactured in the same manner as the battery manufacturing in the above [cycle characteristics (capacity retention rate)].
In an environment with a temperature of 15 ° C., the battery is charged and discharged, the discharge capacity when discharged at 0.2 C and the discharge capacity when discharged at 2 C are measured, the latter is divided by the former, and 10 batteries are used. The average was calculated and the obtained value (%) was used as the load characteristic. The charging condition was 0.2C, 4.2V constant current constant voltage charging for 8 hours, and the discharging condition was 2.75V cutoff constant current discharge.

<Making a separator>
[Example 1]
Conex (registered trademark; manufactured by Teijin Techno Products Co., Ltd.), which is a meta-type total aromatic polyamide, and acrylic in a mixed solvent of dimethylacetamide and tripropylene glycol (dimethylacetamide: tripropylene glycol = 80: 20 [mass ratio]). System resin (butyl acrylate-methyl methacrylate-styrene copolymer, polymerization ratio [mass ratio] 20:40: 4
0, weight average molecular weight 32,000, glass transition temperature 60 ° C.) was dissolved to prepare a coating liquid for forming a heat-resistant adhesive porous material. The mass ratio of the meta-type total aromatic polyamide contained in the coating liquid to the acrylic resin was 55:45, and the resin concentration of the coating liquid was 9.0% by mass. The obtained coating liquid was transparent.

The coating liquid was applied to a polyethylene microporous film (film thickness 9.0 μm, galley value 150), which is a porous base material.
Apply on both sides of the second (100 cc, porosity 43%) (at that time, apply so that the amount of application on the front and back is equal), and the coagulant (water: dimethylacetamide: tripropylene glycol = 62).
.. It was immersed in 5:30: 7.5 [mass ratio], liquid temperature 35 ° C.) to solidify. Then, this was washed with water and dried to obtain a separator having a heat-resistant adhesive porous layer formed on both sides of the polyethylene microporous membrane. The drying temperature was 60 ° C. As a result of microscopic (SEM) observation, the heat-resistant adhesive porous layer had a structure in which an acrylic resin having a particle shape of 80 nm was dispersed in a porous structure made of a meta-type total aromatic polyamide.

[Example 2]
As an acrylic resin, a quaternary copolymer of butyl acrylate-methyl methacrylate-styrene-unsaturated carboxylic acid anhydride (polymerization ratio [mass ratio] 20:39:39: 2, weight average molecular weight 35,000, A separator was prepared in the same manner as in Example 1 except that the glass transition temperature was changed to 61 ° C.). The obtained coating liquid was transparent. As a result of microscopic (SEM) observation of the separator, the heat-resistant adhesive porous layer had a structure in which an acrylic resin having a particle shape of 78 nm was dispersed in a porous structure made of a meta-type total aromatic polyamide.

[Example 3]
Dimethylacetamide and Cornex (registered trademark), which is a meta-type total aromatic polyamide.
Teijin Techno Products Co., Ltd. and acrylic resin (lauryl acrylate-ethylhexyl acrylate-styrene ternary copolymer (polymerization ratio [mass ratio] 40:40:20, weight average molecular weight 65,000, glass transition Aqueous emulsion consisting of (temperature -18 ° C) (solid content concentration: 40)
Wt%, average particle size: 170 nm) and water-soluble fluorine-based surfactant (AGC Seimi Chemical Co., Ltd .: Surflon S233) are added in an amount of 0.1 wt% to the coating liquid to coat 8.2% by mass. A working solution was prepared. A separator was prepared in the same manner as in Example 1 except that this coating liquid was used. The obtained coating liquid was opaque because the acrylic particles were insoluble in the coating liquid.
As a result of microscopic observation of the separator, no acrylic resin particles having an average particle diameter of 170 nm were observed, and the surface of the porous structure made of meta-type total aromatic polyamide was coated with the acrylic resin.

[Example 4]
A separator was prepared in the same manner as in Example 1 except that Cornex (registered trademark; manufactured by Teijin Techno Products Co., Ltd.), which is a meta-type all-aromatic polyamide, was changed to all-aromatic polyamide-imide (manufactured by Solvay, Toron 4000TF). bottom. The obtained coating liquid was transparent. As a result of microscopic observation of the separator, the heat-resistant adhesive porous layer had a structure in which an acrylic resin having a particle shape of 68 nm was dispersed in a porous structure made of a total aromatic polyamide-imide.

[Example 5]
Magnesium hydroxide particles (volume average particle size of primary particles 0.8 μm, BET specific surface area 6.8 m ² / g) were further dispersed in the coating liquid so as to have the contents shown in Table 1. A separator was prepared in the same manner as in Example 1.

[Example 6]
Separator in the same manner as in Example 1 except that the porous substrate was changed to Cellguard (polypropylene / polyethylene / polypropylene three-layer structure, film thickness 16.0 μm, galley value 185 seconds / 100 cc, porosity 48%). Was produced.

[Comparative Example 1]
A separator was prepared in the same manner as in Example 1 except that the coating liquid did not contain an acrylic resin.

[Comparative Example 2]
A separator was prepared in the same manner as in Example 4 except that the coating liquid did not contain an acrylic resin.

[Comparative Example 3]
A separator was prepared in the same manner as in Example 1 except that the coating liquid did not contain a heat-resistant resin.

[Comparative Example 4]
Examples except that a polyvinylidene fluoride resin (VDF-HFP binary copolymer, ratio of HFP unit: 5.1% by mass, weight average molecular weight: 1.13 million) was used as the coating liquid instead of the acrylic resin. A separator was prepared in the same manner as in 1. The coating liquid was cloudy.

[Comparative Example 5]
Examples except that a polyvinylidene fluoride resin (VDF-HFP binary copolymer, ratio of HFP unit: 5.1% by mass, weight average molecular weight: 1.13 million) was used as the coating liquid instead of the acrylic resin. A separator was prepared in the same manner as in 4. The coating liquid was cloudy.

Claims (15)

Porous substrate and
A heat-resistant porous layer provided on one or both sides of the porous substrate and having an amide structure having a glass transition temperature of 200 ° C. or higher, and a heat-resistant adhesive porous layer containing an acrylic resin.
Consists of a composite membrane with
The heat-resistant resin is a total aromatic polyamide, and the heat-resistant resin is a total aromatic polyamide.
However, the acrylic resin is a copolymer of an unsaturated carboxylic acid and an unsaturated carboxylic acid ester, and has an unsaturated carboxylic acid unit of 1% by mass or more and 70% by mass or less, and is the unsaturated carboxylic acid unit. A separator for a non-aqueous secondary battery, except when the carboxyl group is a water-soluble resin in which at least a part of the carboxyl group is an ammonium salt or an alkali metal salt . The non-according to claim 1, wherein the heat-resistant adhesive porous layer has a structure in which the acrylic resin having a particle shape of 10 to 500 nm is dispersed in a porous structure made of the heat-resistant resin. Separator for water-based secondary batteries. The separator for a non-aqueous secondary battery according to claim 2, wherein the acrylic resin has a glass transition temperature of 0 to 80 ° C. The non-aqueous layer according to claim 1, wherein the heat-resistant adhesive porous layer has a structure in which the surface and / or the inner surface of the pores of the porous structure made of the heat-resistant resin is coated with the acrylic resin. Separator for secondary batteries. The separator for a non-aqueous secondary battery according to claim 4, wherein the acrylic resin has a glass transition temperature of less than 0 ° C. The separator for a non-aqueous secondary battery according to any one of claims 1 to 5, wherein the heat-resistant resin is a meta-aromatic polyamide or a para-aromatic polyamide, which is a total aromatic polyamide. The invention according to any one of claims 1 to 6, wherein the heat-resistant adhesive porous layer contains 5 to 60% by mass of the acrylic resin with respect to the total mass of the acrylic resin and the heat-resistant resin. Separator for non-aqueous secondary batteries. The separator for a non-aqueous secondary battery according to any one of claims 1 to 7, wherein the heat-resistant adhesive porous layer contains 5 to 80% by mass of a filler with respect to the total mass of the heat-resistant adhesive porous layer. .. The separator for a non-aqueous secondary battery according to any one of claims 1 to 8, wherein the porous substrate is a microporous polyolefin membrane containing polypropylene. The separator for a non-aqueous secondary battery according to any one of claims 1 to 9, wherein the peel strength between the porous substrate and the heat-resistant adhesive porous layer is 0.1 N / 10 mm or more. The separator for a non-aqueous secondary battery according to any one of claims 1 to 10, wherein an adhesive porous layer containing a polyvinylidene fluoride-based resin is further formed on one side or both sides of the composite film. The non-aqueous secondary battery separator according to any one of claims 1 to 11 is provided with a positive electrode, a negative electrode, and a separator arranged between the positive electrode and the negative electrode, and an electromotive force is obtained by doping / dedoping lithium. Non-aqueous secondary battery. A heat-resistant porous base material, a heat-resistant resin provided on one or both sides of the porous base material and having an amide structure having a glass transition temperature of 200 ° C. or higher, and a heat-resistant adhesive porous layer containing an acrylic resin. It is a method for manufacturing a separator for a non-aqueous secondary battery made of a provided composite film.
(I) A step of applying a coating liquid containing a heat-resistant resin, an acrylic resin, and a solvent capable of dissolving the heat-resistant resin and the acrylic resin onto a porous substrate to form a coating layer.
(Ii) The porous substrate on which the coating layer is formed is immersed in a coagulating liquid containing a poor solvent of the heat-resistant resin and the acrylic resin, and the heat-resistant resin and the acrylic resin are induced while inducing phase separation in the coating layer. To solidify and form a porous layer on a porous substrate to obtain a composite film.
(Iii) A method for manufacturing a separator for a non-aqueous secondary battery, which comprises washing and drying the composite film with water. A heat-resistant porous base material, a heat-resistant resin provided on one or both sides of the porous base material and having an amide structure having a glass transition temperature of 200 ° C. or higher, and a heat-resistant adhesive porous layer containing an acrylic resin. It is a method for manufacturing a separator for a non-aqueous secondary battery made of a provided composite film.
(I) A step of applying a coating liquid containing a heat-resistant resin, an acrylic resin which is an aqueous emulsion, and a solvent capable of dissolving the heat-resistant resin to a porous base material to form a coating layer.
(Ii) The porous substrate on which the coating layer is formed is immersed in a coagulating liquid containing a poor solvent for the heat-resistant resin, and the heat-resistant resin is solidified while inducing phase separation in the coating layer to solidify the porous substrate. The process of forming a porous layer on top and obtaining a composite film,
(Iii) A method for manufacturing a separator for a non-aqueous secondary battery, which comprises washing and drying the composite film with water. The method for producing a separator for a non-aqueous secondary battery according to claim 14, wherein the coating liquid contains a water-soluble surfactant.