JP2021082375A - Separator for nonaqueous electrolyte battery and method for manufacturing the same - Google Patents

Abstract

To provide a separator for a nonaqueous electrolyte battery, which is high in safety, which is well controlled in pores, and low in internal resistance when used as a separator of a nonaqueous electrolyte battery, and which enables the enhancement in battery characteristics including high efficiency and high battery capacity.SOLUTION: A separator for a nonaqueous electrolyte battery consists of a porous film comprising an ethylene-vinyl alcohol based copolymer. As to the porous film, in a micropore distribution measured by a method of mercury penetration, the percentage of a volume of pores in a range of 0.1-1 μm in pore diameter to a volume of pores in a range of 0.01-10 μm in pore diameter is 80% or more.SELECTED DRAWING: None

Description

The present invention relates to a separator for a non-aqueous electrolyte battery, a method for producing the same, and a non-aqueous electrolyte battery using the separator for a non-aqueous electrolyte battery.

In recent years, various non-aqueous electrolyte batteries have been developed with the spread of mobile terminals such as mobile phones, notebook computers, pad-type information terminal devices, electric vehicles, hybrid vehicles, and the like. Non-aqueous electrolyte batteries such as lithium ion secondary batteries differ in form, capacity, performance, etc. depending on their use, but in general, a positive electrode and a negative electrode are installed via a separator (separation film), and LiPF ₆ , LiPF 6, A structure in which a lithium salt such as LiBF ₄ , LiTFSI (lithium (bistrifluoromethylsulfonylimide)), or LiFSI (lithium (bisfluorosulfonylimide)) is stored in a container together with an electrolytic solution dissolved in an organic liquid such as ethylene carbonate. Has.

Compared to aqueous batteries, non-aqueous electrolyte batteries having the above structure are more likely to have a risk of temperature rise due to external heat, overcharging, smoke generation due to internal short circuit or external short circuit, ignition, explosion, etc., and are highly safe. Sex is required. Conventionally, in order to ensure safety, most of the separators that make up a non-aqueous electrolyte battery are made of a porous film (porous film), and when the temperature inside the battery rises, the flow of current and ions is blocked by closing the holes. It has a so-called shutdown function. A porous film made of a polyolefin resin is widely used as such a separator. For example, a porous film made of a polyolefin resin provided with a coating layer containing filler particles and a binder for the purpose of improving safety. A separator has been proposed (Patent Document 1). Further, as a porous membrane, a porous membrane made of an ethylene-vinyl alcohol copolymer produced by a wet coagulation method is known (Patent Document 2), and it is used as a separator for an ethylene-vinyl alcohol copolymer porous membrane. Its use has also been proposed (Patent Document 3).

JP-A-2007-280911 Japanese Unexamined Patent Publication No. 49-113859 Japanese Unexamined Patent Publication No. 56-49157

However, in a separator in which a coating layer containing filler particles and a binder is provided in a porous film as described in Patent Document 1, the internal resistance of the electric element is likely to increase and the output characteristics are likely to be deteriorated, resulting in a charge / discharge cycle. There is a problem that the cycle life is shortened due to the sudden decrease in capacity as the process progresses. In addition, since a step of providing a coating layer on the porous film is required, there are problems such as an increase in production cost and a decrease in productivity. On the other hand, in the method described in Patent Document 2, it is difficult to sufficiently control the pores and porosity, so that the pores of the obtained porous membrane tend to be non-uniform and the pore diameter tends to be relatively small. It is in. Therefore, when such a porous membrane is used as a separator for a non-aqueous electrolyte battery, the performance as a battery component is not always satisfactory, such as an increase in internal resistance due to a decrease in the liquid permeability of the electrolytic solution. It was. Further, the ethylene-vinyl alcohol copolymer porous film as described in Patent Document 3 is not sufficient in terms of mechanical strength as a separator for a non-aqueous electrolyte battery and performance as a battery component, and also has a porosity and fineness. Since an inorganic powder is used to control the pore size, a process such as recovery of unnecessary parts is required, and there is also a problem that productivity is poor.

Therefore, the present invention has high safety, sufficiently controlled pores, low internal resistance when used as a separator for a non-aqueous electrolyte battery, and improves battery characteristics such as high efficiency and high battery capacity. It is an object of the present invention to provide a separator for a non-aqueous electrolyte battery which can be used. The present invention also provides a method for producing a separator for a non-aqueous electrolyte battery, which can easily control pores and porosity and can efficiently produce a separator for a non-aqueous electrolyte battery capable of improving battery characteristics. The purpose.

The present inventors have arrived at the present invention as a result of diligent studies to solve the above problems. That is, the present invention provides the following preferred embodiments.
[1] It is composed of a porous membrane composed of an ethylene-vinyl alcohol-based copolymer, and in the porous membrane, it is fine with respect to the pore volume in the pore diameter range of 0.01 to 10 μm in the pore distribution measured by the mercury intrusion method. A separator for a non-aqueous electrolyte battery, wherein the ratio of the pore volume in the pore diameter range of 0.1 to 1 μm is 80% or more.
[2] The separator for a non-aqueous electrolyte battery according to the above [1], wherein the porosity of the porous membrane is 20% or more.
[3] The endothermic peak calorie derived from the crystal melting of the porous film and the endothermic peak calorie derived from the crystal melting of the ethylene-vinyl alcohol-based copolymer constituting the porous film, as measured by a differential scanning calorimeter. The separator for a non-aqueous electrolyte battery according to the above [1] or [2], wherein the ratio (endothermic peak heat of the porous film / endothermic peak heat of the ethylene-vinyl alcohol-based copolymer) is 1.10 to 3.50. ..
[4] The separator for a non-aqueous electrolyte battery according to any one of [1] to [3] above, wherein the porous membrane is a flat membrane having a thickness of 1 μm or more and less than 50 μm.
[5] The above-mentioned [1] to [4], wherein the ethylene-vinyl alcohol-based copolymer has an ethylene content of 20 to 60 mol% and a saponification degree of 80 mol% or more. Separator for non-aqueous electrolyte batteries.
[6] The separator for a non-aqueous electrolyte battery according to any one of [1] to [5] above, wherein the ethylene-vinyl alcohol-based copolymer has a crosslinked structure.
[7] A method for producing a separator for a non-aqueous electrolyte battery, which comprises a step of wet-coagulating a solution containing an ethylene-vinyl alcohol-based copolymer and a solvent.
The wet coagulation step comprises immersing a solution containing the ethylene-vinyl alcohol copolymer and a solvent, which may be applied to a substrate, in a coagulation liquid for 1 second to 30 minutes.
A production method, wherein the absolute value of the difference between the temperature of the solution and the temperature of the coagulating solution is 35 ° C. or less, and the solvent constituting the solution is a mixed solvent containing water and alcohol.
[8] The production method according to the above [7], wherein the temperature of the coagulating liquid is 10 to 70 ° C.
[9] The production method according to the above [7] or [8], wherein the coagulating liquid contains 50% by mass or more of water with respect to the total mass of the coagulating liquid.
[10] A non-aqueous electrolyte battery comprising the separator for a non-aqueous electrolyte battery according to any one of the above [1] to [6].

According to the present invention, the safety is high, the pores are sufficiently controlled, the internal resistance is low when used as a separator for a non-aqueous electrolyte battery, and the battery characteristics such as high efficiency and high battery capacity are improved. It is possible to provide a separator for a non-aqueous electrolyte battery which can be used. Further, the present invention can provide a method for producing a separator for a non-aqueous electrolyte battery, which can easily control pores and porosity and can efficiently produce a separator for a non-aqueous electrolyte battery capable of improving battery characteristics. it can.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto.

The separator for a non-aqueous electrolyte battery of the present invention (hereinafter, also referred to as “separator of the present invention”) is composed of a porous film composed of an ethylene-vinyl alcohol-based copolymer, and separates the positive electrode and the negative electrode in the non-aqueous electrolyte battery. Moreover, it has an ion transporting property that allows ions to pass between the positive electrode and the negative electrode by passing or holding the electrolytic solution.

In the present invention, as the ethylene-vinyl alcohol-based copolymer for forming the separator, for example, one obtained by saponifying an ethylene-vinyl ester copolymer such as an ethylene-vinyl acetate copolymer can be used. it can. In the present invention, the ethylene content (ethylene modification amount) of the ethylene-vinyl alcohol-based copolymer is preferably 20 to 60 mol%. When the ethylene content is at least the above lower limit, the water resistance of the obtained porous membrane can be improved, and when the ethylene content is at least the above upper limit, the ethylene-vinyl alcohol-based copolymer is appropriate. Since it has a high degree of hydrophilicity, it can be easily processed into a porous membrane. In the present invention, the ethylene content of the ethylene-vinyl alcohol-based copolymer is more preferably 25 mol% or more, further preferably 30 mol% or more, and even more preferably 55 mol% or less. More preferably, it is 50 mol% or less.

The degree of saponification in the ethylene-vinyl alcohol-based copolymer is preferably 80 mol% or more, more preferably 90 mol% or more, and further preferably 95 mol% or more. When the degree of saponification is at least the above lower limit value, moldability is good and a separator having high mechanical strength can be obtained. The upper limit of the degree of saponification is not particularly limited, but it is 100 mol% or less, and it is particularly preferable to use one that is completely saponified (that is, the degree of saponification is 100 mol%). Normally, if the degree of saponification is 99 mol% or more, it is judged that the saponification is complete. In one embodiment of the present invention, the ethylene-vinyl alcohol-based copolymer for forming the separator of the present invention has an ethylene content of 20 to 60 mol% and a saponification degree of 80 mol% or more. Is preferable.

The copolymerization form of the ethylene-vinyl alcohol-based copolymer is not particularly limited, and may be any of a random copolymer, an alternating copolymer, a block copolymer, a graft copolymer and the like.

In the present invention, the ethylene-vinyl alcohol-based copolymer is a structural unit derived from a monomer copolymerizable with these units in addition to the ethylene unit and the vinyl alcohol unit, as long as the effects of the present invention are not impaired. (Hereinafter, also referred to as “other structural units”) may be included. Such other structural units include, for example, α-olefins such as propylene, isobutylene, α-octene, α-dodecene; non-alkenes such as acrylic acid, methacrylic acid, methyl methacrylate, crotonic acid, maleic acid, itaconic acid and the like. Saturated acids or anhydrides, salts thereof, mono- or dialkyl esters, etc .; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methalkylamide; olefins such as ethylene sulfonic acid, allyl sulfonic acid and metaallyl sulfonic acid. Sulfonic acid or a salt thereof; examples thereof include alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride and the like. When the ethylene-vinyl alcohol-based copolymer contains a structural unit derived from another monomer, its content is preferably 15 mol% or less, and more preferably 10 mol% or less.

In the present invention, the ethylene-vinyl alcohol-based copolymer preferably has a crosslinked structure. When the ethylene-vinyl alcohol copolymer has a crosslinked structure, the mechanical strength of the porous membrane (separator) composed of the copolymer can be improved, and the liquid retention property can also be improved. The crosslinked structure is a structure derived from a compound having at least two functional groups (hereinafter, also referred to as “crosslinking agent”) capable of reacting with a hydroxyl group contained in a vinyl alcohol unit in an ethylene-vinyl alcohol-based copolymer. By reacting the ethylene-vinyl alcohol-based copolymer with a cross-linking agent, it can be introduced as a cross-linked structure formed by using a hydroxyl group in a vinyl alcohol unit as a cross-linking point. In the present invention, examples of the cross-linking agent capable of introducing a cross-linking structure into an ethylene-vinyl alcohol-based copolymer include oxalic acid, malonic acid, methylmalonic acid, succinic acid, methylsuccinic acid, dimethylsuccinic acid, 2,3. -Saturated dicarboxylic acids such as dimethylsuccinic acid, glutamate, 3-methylglutamic acid, adipic acid, 3-methyladipic acid, piceric acid, sebatic acid, azelaic acid, tartaric acid, cyclohexanedicarboxylic acid; maleic acid, fumaric acid, itaconic acid , Unsaturated dicarboxylic acids such as citraconic acid, glutaconic acid, aconitic acid; aromatic dicarboxylic acids such as terephthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid; tricarboxylic acids such as citric acid; polyacrylic acid, polymethacryl Examples thereof include polycarboxylic acids such as acids and polymaleic acids; organic cross-linking agents such as diisocyanate and dialdehyde, and inorganic cross-linking agents such as boron compounds. Of these, citric acid, boric acid, and glyoxylic acid are preferable from the viewpoint that a crosslinked structure can be introduced while maintaining an appropriate pore structure. These may be used alone or in combination of two or more.

In the ethylene-vinyl alcohol-based copolymer, the content of the structural unit derived from the cross-linking agent that introduces the cross-linking structure is preferably 0.01 mol% or more, more preferably 0.1 mol% or more, and also. , Preferably 15 mol% or less, more preferably 10 mol% or less. When the content of the structural unit derived from the cross-linking agent into which the cross-linked structure is introduced is within the above range, an appropriate cross-linked structure is formed between the molecules of the ethylene-vinyl alcohol-based copolymer and the cross-linking agent, and the obtained separator is obtained. It is possible to improve the mechanical strength and the liquid retention property while maintaining the liquid permeability to the electrolyte.

The introduction of the crosslinked structure into the ethylene-vinyl alcohol-based copolymer is as described above with the ethylene-vinyl alcohol-based copolymer before or after the film-forming step for forming the porous film from the copolymer. It can be carried out by reacting with a cross-linking agent. In this case, the amount of the cross-linking agent added is preferably 0.001 to 5% by mass, more preferably 0.01 to 3% by mass, still more preferably 0, based on the total mass of the ethylene-vinyl alcohol-based copolymer. .05-2% by mass. Further, the cross-linking structure may be introduced into the ethylene-vinyl alcohol-based copolymer by adding a cross-linking agent to the coagulating liquid. In this case, the amount of the cross-linking agent added is to form the separator of the present invention. 0.001 to 5% by mass, more preferably 0, based on the total weight of the solution containing the ethylene-vinyl alcohol-based copolymer and the solvent (hereinafter, also referred to as “mixed solution for forming a porous film”). It is 0.01 to 4% by mass, more preferably 0.05 to 3% by mass. Whether or not the crosslinked structure is introduced can be confirmed by, for example, whether or not a peak derived from the crosslinked agent of the film obtained by infrared spectroscopy, elemental analysis, or the like is observed.

In the present invention, the method for producing the ethylene-vinyl alcohol-based copolymer is not particularly limited, and it can be prepared by a conventionally known method.

The separator of the present invention comprises a porous membrane composed of an ethylene-vinyl alcohol-based copolymer. The content of the ethylene-vinyl alcohol-based copolymer in the separator (porous film) of the present invention is usually 90% by mass or more, preferably 95% by mass or more, more preferably 95% by mass or more, based on the total mass of the separator. Is 97% by mass or more, and the separator is a porous film substantially composed of an ethylene-vinyl alcohol-based copolymer (that is, the content of the ethylene-vinyl alcohol-based copolymer based on the total mass of the separator is 100% by mass). It may consist of.

In the porous membrane constituting the separator of the present invention, the ratio of the pore volume in the pore diameter range of 0.1 to 1 μm to the pore volume in the pore diameter range of 0.01 to 10 μm in the pore distribution measured by the mercury intrusion method. Is 80% or more. The porous membrane constituting the separator of the present invention is made of a porous membrane showing a sharp pore distribution as described above and has uniform pores, so that a uniform current distribution can be formed during charging and discharging. It is possible, and the dendride is hard to precipitate. By using such a separator, it is possible to obtain a non-aqueous electrolyte battery which is less likely to cause an internal short circuit, has excellent safety, has a long battery life, and has excellent battery characteristics. On the other hand, in the pore distribution measured by the mercury intrusion method, the ratio of the pore volume in the pore diameter range of 0.1 to 1 μm to the pore volume in the pore diameter range of 0.01 to 10 μm is less than 80%. As a result, the pores become non-uniform, and the performance as a separator for a non-aqueous electrolyte battery tends to be inferior. In the present invention, the ratio of the pore volume in the pore diameter range of 0.1 to 1 μm to the pore volume in the pore diameter range of 0.01 to 10 μm in the pore distribution is preferably 82% or more, more preferably 85. % Or more, more preferably 88% or more. The upper limit of the ratio of the pore volume is not particularly limited, but is usually 99% or less, preferably 98% or less. The measurement of the pore distribution by the mercury intrusion method can be performed according to the method described in Examples described later.

The porosity of the porous membrane constituting the separator of the present invention is preferably 20% or more, more preferably 25% or more, further preferably 30% or more, and particularly preferably 40% or more. When the porosity is at least the above lower limit value, the electrolytic solution has excellent liquid permeability and ion passage is facilitated, so that the resistance can be lowered. The porosity is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. When the porosity is not more than the above upper limit value, the strength of the porous membrane can be improved. Therefore, by using such a separator, a non-aqueous electrolyte battery in which an internal short circuit is unlikely to occur can be obtained. The porosity can be measured and calculated from the thickness and weight of the film and the density of the polymer. Detailed measurement and calculation methods are as described in Examples described later.

The average pore diameter of the porous membrane constituting the separator of the present invention is preferably 0.01 μm or more, more preferably 0.1 μm or more, still more preferably 0.5 μm or more, and preferably 4 μm or less. It is preferably 3.5 μm or less, more preferably 3 μm or less. When the average pore diameter is at least the above lower limit value, sufficient liquid permeability to the electrolytic solution can be ensured, and the resistance can be lowered. Further, when the average pore diameter is not more than the above upper limit value, it is possible to obtain a non-aqueous electrolyte battery in which contact between electrodes is prevented and internal short circuits are unlikely to occur. The average pore diameter is a value in the pores on the surface of the separator (porous film) obtained by observation with an electron microscope (SEM).

The shape of the pores in the porous membrane is not particularly limited, and examples thereof include a monolith shape, a honeycomb shape, a disk shape, and a polygonal plate shape. Of these, a monolith shape including a shape having a three-dimensional network structure skeleton and voids that are difficult to short-circuit while having high electrolyte transportability is preferable.

In the separator of the present invention, the endothermic peak calorie derived from the crystal melting of the porous film and the endothermic peak derived from the crystal melting of the ethylene-vinyl alcohol-based copolymer constituting the porous film, which are measured by a differential scanning calorimeter. The ratio to the calorific value (endothermic peak caloric value of the porous film / endothermic peak calorific value of the ethylene-vinyl alcohol-based copolymer) is preferably 1.10 to 3.50, more preferably 1.20 to 3.00. Yes, more preferably 1.30 to 2.00. The higher the ratio of the heat absorption peak calorific value of the porous film and the ethylene-vinyl alcohol-based copolymer constituting the porous film, the higher the crystallinity of the porous film as compared with the ethylene-vinyl alcohol-based copolymer as a raw material. Means that When the ethylene content of the ethylene-vinyl alcohol-based copolymer as a raw material is the same, it can be said that the higher the ratio of the endothermic peak amount, the higher the crystallinity, and the ratio of the endothermic peak heat amount is usually in the above range. When it is inside, the crystallinity of the porous film is high, and when it is used as a separator for a non-aqueous electrolyte battery, the ion path can easily proceed smoothly, and the conductivity can be improved. As a result, the resistance can be lowered, and a highly efficient non-aqueous electrolyte battery can be obtained. The "endothermic peak calorie derived from crystal melting" is the endothermic heat absorption of the second cycle measured by a differential scanning calorimeter when the porous film or the ethylene-vinyl alcohol-based copolymer constituting the porous film is heated. It means the amount of heat absorption at the peak. The detailed measurement method will be described in Examples described later.

The porous membrane constituting the separator of the present invention is not particularly limited, but is preferably flat membrane-like. The thickness is preferably 1 μm or more and less than 50 μm, more preferably 5 μm or more, further preferably 10 μm or more, still more preferably 40 μm or less, still more preferably 35 μm or less. When the thickness of the porous membrane is at least the above lower limit value, the strength of the porous membrane is sufficiently high, and it is possible to obtain a separator that suppresses the occurrence of cracks and is unlikely to cause a short circuit. Further, when the thickness of the porous membrane is not more than the above upper limit value, the liquid permeability of the electrolytic solution is good, and the battery resistance can be lowered.

The separator of the present invention is, for example,
It includes a step of wet-coagulating a solution containing an ethylene-vinyl alcohol-based copolymer and a solvent.
The wet coagulation step comprises immersing a solution containing the ethylene-vinyl alcohol copolymer and a solvent, which may be applied to a substrate, in a coagulation liquid for 1 second to 30 minutes.
It can be produced by a method in which the absolute value of the difference between the temperature of the solution and the temperature of the coagulating solution is 35 ° C. or less, and the solvent constituting the solution is a mixed solvent containing water and alcohol. .. Therefore, the present invention
A method for producing a separator for a non-aqueous electrolyte battery, which comprises a step of wet-coagulating a solution containing an ethylene-vinyl alcohol-based copolymer and a solvent.
The wet coagulation step comprises immersing a solution containing the ethylene-vinyl alcohol copolymer and a solvent, which may be applied to a substrate, in a coagulation liquid for 1 second to 30 minutes.
The absolute value of the difference between the temperature of the solution and the temperature of the coagulating solution is 35 ° C. or less, and the solvent constituting the solution is a mixed solvent containing water and alcohol. Also referred to as "the manufacturing method of the invention").

The production method of the present invention includes a step of wet-coagulating a solution (mixed solution for forming a porous film) containing an ethylene-vinyl alcohol-based copolymer and a solvent (hereinafter, also referred to as a “coagulation step”). As the ethylene-vinyl alcohol-based copolymer constituting the mixed solution for forming a porous film, the same ethylene-vinyl alcohol-based copolymer as described above with respect to the separator of the present invention can be used.

The solvent used in the mixed solution for forming a porous film is a mixed solvent containing water and alcohol from the viewpoint of solubility of the ethylene-vinyl alcohol-based copolymer. Examples of the alcohol that can be mixed with water in the mixed solvent include methanol, ethanol, butanol, isopropanol, 1-propanol, 1-butanol, ethylene glycol and the like. These may be used alone or in combination of two or more. Among them, from the viewpoint of solubility of the ethylene-vinyl alcohol-based copolymer and formation of pores, the solvent used for the mixed solution for forming the porous film is selected from the group consisting of water, methanol, ethanol, isopropanol and 1-propanol. It is preferably a mixed solvent with one or more alcohols.

In the mixed solvent containing water and alcohol, the mixing ratio of water and alcohol (water / alcohol) is preferably 20/80 to 70/30, more preferably 25/75 to 65/35 in terms of volume ratio. .. By using a mixed solvent containing water and alcohol in a ratio within the above range, it is possible to easily prepare a mixed solution for forming a porous film containing an ethylene-vinyl alcohol-based copolymer having a solid content concentration suitable for forming a porous film. it can. In the production method of the present invention, the mixed solvent used in the mixed solution for forming a porous film may contain a small amount of a solvent other than water and alcohol as long as it can dissolve the ethylene-vinyl alcohol-based copolymer. , Preferably a mixed solvent consisting of water and alcohol.

The solid content concentration of the ethylene-vinyl alcohol-based copolymer in the mixed solution for forming a porous membrane is preferably 3 to 50% by mass, more preferably 5 to 45% by mass. When the solid content concentration of the ethylene-vinyl alcohol-based copolymer is in the above range, the handleability of the mixed solution for forming a porous film is good, and it is easy to form a porous film by wet solidification.

Further, the mixed solution for forming a porous film may contain a cross-linking agent for introducing a cross-linked structure into the ethylene-vinyl alcohol-based copolymer constituting the separator of the present invention. In this case, the amount of the cross-linking agent added is preferably 0.001 to 5% by mass, more preferably 0.01 to 3% by mass, still more preferably 0, based on the total mass of the ethylene-vinyl alcohol-based copolymer. .05-2% by mass.

Further, the mixed solution for forming a porous film is a polymer compound (copolymer) other than the ethylene-vinyl alcohol-based copolymer, as well as an antioxidant, an ultraviolet absorber, and a lubricant, as long as the effects of the present invention are not impaired. , Inorganic fine powders such as antifoaming agents and anti-blocking agents, and additives such as organic substances may be contained. In this case, the content of the above components other than the ethylene-vinyl alcohol-based copolymer is usually 10% by mass or less, preferably 5% by mass or less, based on the solid content of the mixed solution for forming a porous membrane. .. The solid content of the mixed solution for forming a porous film means the total amount of the components excluding the solvent from the mixed solution for forming a porous film.

The mixed solution for forming a porous film is prepared by mixing an ethylene-vinyl alcohol-based copolymer and, if necessary, other components such as a cross-linking agent and an additive with a mixed solvent containing water and alcohol, and stirring the mixture to form ethylene. -It can be obtained by dissolving a vinyl alcohol-based copolymer. A wet film can be obtained by immersing the obtained mixed solution for forming a porous film in a coagulating solution to coagulate it.

Immersion of the mixed solution for forming a porous film in a coagulating solution is not particularly limited as long as a wet film having a desired shape and film thickness can be obtained after solidification, and is based on, for example, the mixed solution for forming a porous film. After being applied to the material, the porous film forming mixed solution may be immersed in the coagulating solution together with the base material, or the porous film forming mixed solution may be directly poured into the coagulating solution through a slit. Specific examples of the method for applying the mixed solution for forming a porous film to a substrate include a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a dipping method, and a brush coating method. And so on. Further, as a method of directly putting the mixed liquid for forming a porous film into the coagulating liquid, for example, extrusion by a T-die method, an inflation method or the like can be mentioned.

Examples of the base material to which the mixed solution for forming a porous film can be applied include polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyethylene (PE), and glass.

The coagulating liquid is not particularly limited as long as it is a solution capable of coagulating the mixed liquid for forming a porous membrane, and examples thereof include a mixed solution of water, water and an organic solvent. Examples of the organic solvent that can be mixed with water include alcohols such as methanol, ethanol, isopropanol and 1-propanol, and ketones such as acetone and methyl ethyl ketone. These may be used alone or in combination of two or more. As the coagulating solution, water or a mixed solution of water and an organic solvent is preferable, and the solvent can be easily prepared and discarded because it has a high coagulation ability with respect to the mixed solution for forming a porous film and makes it easy to obtain uniform pores. Therefore, water or a mixed solution of water and alcohol is more preferable.

When a crosslinked structure is introduced into the ethylene-vinyl alcohol-based copolymer constituting the separator of the present invention, a crosslinked agent may be added to the coagulating liquid. In this case, the amount of the cross-linking agent added is preferably 0.001 to 5% by mass, more preferably 0.01 to 4% by mass, based on the total weight of the porous membrane-forming mixed solution for forming the separator of the present invention. %, More preferably 0.05 to 3% by mass.

The content of water in the coagulation liquid is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, based on the total mass of the coagulation liquid. In other words, when the coagulation liquid is composed of water and an organic solvent (preferably alcohol), the content of the organic solvent in the coagulation liquid is preferably less than 50% by mass with respect to the total mass of the coagulation liquid, and more. It is preferably less than 40% by mass, more preferably less than 30% by mass. The upper limit of the content of water in the coagulation liquid is not particularly limited, and may consist only of water (that is, 100% by mass). Since the higher the water content, the faster the coagulation rate tends to be, the higher the water content in the coagulation liquid, the more preferable. Since it is present, the upper limit of the water content is usually about 98%.

In the production method of the present invention, the absolute value of the difference between the temperature of the mixed solution for forming a porous membrane and the temperature of the coagulating solution is 35 ° C. or less. By setting the difference between the temperature of the mixed solution for forming a porous film and the temperature of the coagulating solution to 35 ° C. or less in absolute value, the pores and porosity of the obtained porous film can be effectively and easily controlled. , A porous membrane having a pore diameter suitable as a separator for a non-aqueous electrolyte battery and having uniform pores can be obtained. On the other hand, if the difference between the temperature of the mixed solution for forming a porous film and the temperature of the coagulating liquid becomes too large, the coagulation rate of the ethylene-vinyl alcohol-based copolymer becomes faster than the pore formation rate, and the copolymer coagulates. As a result, sufficient pore formation is not achieved, and it becomes difficult to obtain a desired pore diameter. Further, in the production method of the present invention, the pores and porosity can be controlled by adjusting the temperature of the mixed solution for forming a porous film and the temperature of the coagulating liquid, and further for controlling the pores and porosity. Since it does not require a process or a complicated process, it has the advantages of high productivity and reduction of production cost. Further, the porous film obtained by reducing the difference between the temperature of the mixed solution for forming the porous film and the temperature of the coagulating solution and performing the coagulation step under the conditions within the above temperature range, and the ethylene constituting the porous film. -It becomes easy to control the ratio of the endothermic peak calorific value derived from crystal melting with the vinyl alcohol copolymer within a desired range. In the production method of the present invention, the absolute value of the difference between the temperature of the mixed solution for forming a porous membrane and the temperature of the coagulating solution is preferably 20 ° C. or lower, more preferably 15 ° C. or lower, still more preferably 12 ° C. or lower. The lower limit of the difference between the temperature of the mixed solution for forming a porous membrane and the temperature of the coagulating liquid is not particularly limited, and is usually about 10 ° C., and the temperature of the mixed solution for forming a porous film and the temperature of the coagulating liquid are the same. (Ie, 0 ° C.) may be used. In the present invention, the temperature of the mixed solution for forming a porous film means the temperature of the mixed solution when the mixed solution for forming a porous film is put into the coagulating solution, and immediately after being applied to a substrate or the like, it is transferred to the coagulating solution. In the case of immersion, the temperature at the time of application of the mixed solution for forming a porous film can be regarded as the temperature of the mixed solution for forming a porous film.

The temperature of the coagulating liquid is preferably 10 to 70 ° C., more preferably 15 ° C. or higher, further preferably 20 ° C. or higher, particularly preferably 30 ° C. or higher, particularly preferably higher than 30 ° C., and even more preferably. Is 65 ° C. or lower. When the temperature of the coagulating liquid is within the above range, film formation and porosity formation by coagulation of the ethylene-vinyl alcohol-based copolymer proceed in a well-balanced manner, so that a porous film having desired pores and porosity can be obtained. be able to. Further, the porous film obtained by reducing the difference between the temperature of the mixed solution for forming the porous film and the temperature of the coagulating solution and performing the coagulation step under the conditions within the above temperature range, and the ethylene constituting the porous film. -It becomes easy to control the ratio of the endothermic peak calorific value derived from crystal melting with the vinyl alcohol copolymer within a desired range. On the other hand, if the temperature of the coagulating liquid is too low, phase separation proceeds prior to pore formation, making it difficult to form sufficient pores, and obtaining a porous membrane having a desired pore diameter and porosity. Becomes difficult. Further, if the temperature of the coagulating liquid is too high, spinodal decomposition does not occur sufficiently, and it becomes difficult to form a porous film.

The temperature of the mixed solution for forming a porous membrane is preferably 20 to 90 ° C, more preferably 30 to 80 ° C. When the temperature of the mixed solution for forming a porous film is within the above range, film formation and pore formation due to coagulation of the ethylene-vinyl alcohol-based copolymer can proceed in a well-balanced manner when immersed in the coagulating solution. .. Further, the porous film obtained by reducing the difference between the temperature of the mixed solution for forming the porous film and the temperature of the coagulating solution and performing the coagulation step under the conditions within the above temperature range, and the ethylene constituting the porous film. -It becomes easy to control the ratio of the endothermic peak calorific value derived from crystal melting with the vinyl alcohol copolymer within a desired range.

In the production method of the present invention, the immersion time of the mixed solution for forming a porous membrane in the coagulating liquid is 1 second to 30 minutes, preferably 3 seconds or longer, more preferably 5 seconds or longer, and preferably 25 seconds. Minutes or less, more preferably 20 minutes or less. If the immersion time is too short, the ethylene-vinyl alcohol-based copolymer does not sufficiently solidify, and it becomes difficult to obtain pores having a desired pore diameter. Further, if the immersion time is too long, excessive swelling occurs in the coagulating liquid, and in an extreme case, the porosity is reduced and the desired pores cannot be obtained, and the productivity is also lowered.

In the production method of the present invention, the wet film obtained by the coagulation step may be subjected to a drying treatment for removing the solvent. The method of the drying treatment is not particularly limited, and for example, natural drying; aeration drying with warm air, hot air, and low humidity air; heat drying; decompression / vacuum drying; irradiation ray drying such as infrared rays, far infrared rays, and electron beams, and It may be done by a combination of these. From the viewpoint of improving production efficiency without disturbing the pores and voids formed in the solidification step, aeration drying is preferable. The drying conditions are such that the solvent can be removed as soon as possible according to the type of solvent used, the amount of solvent contained in the wet film, etc., as long as the obtained porous film is not damaged (for example, cracks are generated due to stress concentration). It may be decided as appropriate. For example, the drying temperature is usually 10 to 150 ° C., preferably 25 to 110 ° C., and the drying time is usually about 1 to 90 minutes.

Further, in order to improve the smoothness of the porous membrane, the porous membrane from which the solvent has been removed may be rolled. Examples of the rolling method include a mold press and a roll press.

The separator for a non-aqueous electrolyte obtained by the production method of the present invention is made of a porous membrane showing a sharp pore distribution and has uniform pores, so that a uniform current distribution can be formed during charging and discharging. It is possible, and the dendride is hard to precipitate. By using such a separator, it is possible to obtain a non-aqueous electrolyte battery which is less likely to cause an internal short circuit, has excellent safety, has a long battery life, and has excellent battery characteristics. Therefore, the present invention also covers a non-aqueous electrolyte battery including the separator for the non-aqueous electrolyte battery of the present invention.

The non-aqueous electrolyte battery of the present invention comprises the separator of the present invention. Examples of the non-aqueous electrolyte battery include a lithium ion battery, a sodium ion battery, a lithium sulfur battery, an all-solid-state battery, and a lithium ion capacitor.

The non-aqueous electrolyte battery of the present invention generally includes a positive electrode, a negative electrode, and an electrolytic solution in addition to the separator of the present invention. The non-aqueous electrolyte battery of the present invention can be manufactured using known materials and techniques.

As the negative electrode, a negative electrode usually used for a non-aqueous electrolyte battery such as a lithium ion secondary battery is used without particular limitation. For example, as the negative electrode active material, graphite, hard carbon, Si-based oxide and the like are used. Further, the negative electrode active material is a conductive auxiliary agent such as metal powder, a conductive polymer, acetylene black or carbon black, and a binder such as SBR, NBR, acrylic rubber, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinylidene fluoride or polyvinyl alcohol. A negative electrode slurry prepared by mixing with water or a solvent having a boiling point of 100 ° C. or higher and 300 ° C. or lower at normal pressure (for example, N-methyl-2-pyrrolidone) is used as a negative electrode current collector such as a copper foil. It can be applied and the solvent dried to obtain a negative electrode.

As the positive electrode, a positive electrode usually used for a non-aqueous electrolyte battery such as a lithium ion secondary battery is used without particular limitation. For example, as the positive electrode active material, TiS ₂ , TiS ₃ , amorphous MoS ₃ , Cu ₂ V ₂ O ₃ , amorphous V ₂ O-P ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O Transition metal oxides such as ₁₃ and lithium-containing composite metal oxides such as _{LiCoO 2} , LiNiO ₂ , LiMnO ₂ and LiMn ₂ O _{4 are used.} Further, the positive electrode active material is a conductive auxiliary agent exemplified in the negative electrode and a binder such as SBR, NBR, acrylic rubber, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinylidene fluoride, and polyvinyl coal, and has a boiling point of 100 ° C. in water or normal pressure. A positive electrode slurry prepared by mixing with a solvent or the like at 300 ° C. or lower can be applied to a positive electrode current collector such as aluminum and dried to obtain a positive electrode.

Further, as the electrolytic solution in the non-aqueous electrolyte battery of the present invention, an electrolytic solution in which an electrolyte is dissolved in a solvent can be used. The electrolytic solution may be liquid or gel-like as long as it is used for a non-aqueous electrolyte battery such as a normal lithium ion secondary battery, and functions as a battery depending on the type of the negative electrode active material and the positive electrode active material. You can select the one that exerts it as appropriate. Specific electrolytes, for example, any known lithium salt can be _{used, LiClO 4, LiBF 6, LiPF} 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 Cl 10, _{LiAlC l4, LiCl, LiBr, LiB} (C 2 H 5) 4, CF 3 SO 3 Li, CH 3 SO 3 Li, LiCF 3 SO 3, LiC 4 F 9 SO 3, Li (CF 3 SO 2) 2 N, Examples thereof include lower aliphatic lithium carboxylate.

The solvent for dissolving such an electrolyte (electrolyte solution solvent) is not particularly limited. Specific examples include, for example, carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate and diethyl carbonate; lactones such as γ-butyl lactone; trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2 -Esters such as ethoxyethane, tetrahydrofuran and 2-methyltetrax; Sulfoxides such as dimethylsulfoxide; Oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane; Nitrogen-containing compounds such as acetonitrile and nitromethane Classes; organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate; inorganic acid esters such as triethyl phosphate, dimethyl carbonate, diethyl carbonate; diglimes; triglimes; Sulfolans; oxazolidinones such as 3-methyl-2-oxazolidinone; sulton compounds such as 1,3-propane sulton, 1,4-butane sulton, nafta sulton, etc., which can be used alone or in admixture of two or more. .. When a gel-like electrolytic solution is used, a nitrile-based polymer, an acrylic-based polymer, a fluorine-based polymer, an alkylene oxide-based polymer, or the like can be added as a gelling agent.

In particular, as the binder used for the negative electrode and the positive electrode, the separator of the present invention is used by using a polymer compound having a copolymer containing vinyl alcohol, vinyl acetal and / or vinyl ester, which is the same material as the separator of the present invention. It is expected that the electrode position will shift and the productivity will be improved by preventing the active material from falling off. Therefore, it is more preferable to use the same kind of material as the separator of the present invention as the binder. On the other hand, from the viewpoint of the balance between availability and productivity improvement, it is one of the preferred embodiments to use an SBR emulsion.

The method for producing the non-aqueous electrolyte battery of the present invention is not particularly limited, and the non-aqueous electrolyte battery can be produced according to a conventionally known method. For example, there is a method in which the negative electrode and the positive electrode are overlapped with each other via the separator of the present invention, wound or folded according to the shape of the battery, placed in a battery container, and the electrolytic solution is injected to seal the battery. In the present invention, the shape of the non-aqueous electrolyte battery may be any of known coin type, button type, sheet type, cylindrical type, square type, flat type and the like.

The non-aqueous electrolyte battery of the present invention containing the separator of the present invention as a constituent member has high safety, is unlikely to cause an increase in internal resistance, and has excellent battery characteristics such as high battery capacity. The non-aqueous electrolyte battery of the present invention can be suitably used for various applications, for example, in a mobile terminal requiring miniaturization, thinning, weight reduction and high performance, high capacity and high current. It is useful as a battery used in large equipment such as electric vehicles that require performance such as charge / discharge characteristics.

Hereinafter, the present invention will be specifically described with reference to Examples, but these do not limit the scope of the present invention.

1. 1. Example 1
(1) Preparation of mixed solution for forming a porous film Ethylene-vinyl alcohol copolymer powder (manufactured by Kuraray, E105B) having an ethylene content of 44 mol% is mixed with water and 1-propanol (water / 1-propanol =). It was dissolved in 35/65 volume ratio) at 70 ° C. for 3 hours to prepare a mixed solution for forming a porous film having a solid content concentration of 10% by mass.

(2) Preparation of Separator The above-mentioned mixed solution for forming a porous film is applied onto a base material made of a glass plate placed on a horizontal table using a bar coater (T101, manufactured by Matsuo Sangyo Co., Ltd.) ( After the temperature of the mixed solution for forming a porous film: 50 ° C.), the mixed solution for forming a porous film was immersed in a water bath at 40 ° C. for 10 minutes together with the glass plate base material to solidify. Next, a wet film made of an ethylene-vinyl alcohol copolymer was taken out, peeled from the substrate, air-dried, and dried at 100 ° C. for 1 hour to obtain a separator made of a porous film. The film thickness of the obtained porous membrane was 28 μm.

(3) Measurement of physical properties of the separator (porous membrane) The pore distribution, pore diameter, porosity, liquid absorption, crystallinity and tensile strength of the obtained separator (porous membrane) are measured and calculated according to the following methods, respectively. did. The results are shown in Table 1.

<Pore distribution>
The pore volume distribution was calculated by the mercury intrusion method under the following conditions.
Measurement condition:
Measuring device: moremaster 33-P-GT manufactured by Kantachrome Instruments Japan GK
Mercury contact angle 130.00 °, surface tension 485.00 erg / cm ²
Pressure range: 12.2 kPa to 123 MPa
Cell volume: 1cc

<Calculation of porosity>
The porosity of the porous membrane was calculated according to the following formula by measuring the thickness and mass of a sample punched to a predetermined size (φ17 mm).
Porosity = {1- (theoretical volume of separator / apparent volume of separator)} x 100
Theoretical volume of separator = (mass of separator) / (theoretical density)
Apparent volume of separator = (thickness) x (area of separator)

<Liquid absorption>
100 ml of a mixed solvent (EC / EMC = 3/7) of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) was placed in a container. The separator was cut into a size of 10 mm in the longitudinal direction and 60 mm in the width direction, and the tip 1 mm in the width direction was immersed in the above-mentioned mixed solvent, and after 1 minute, the height of the mixed solvent sucked up by the capillary phenomenon (the height from the liquid surface). Liquid absorption height) was measured. The evaluation was performed 10 times per sample, and the average value was taken as the electrolyte absorption height.

<Pore diameter>
The diameter of 100 openings observed in the scanning electron micrograph was averaged and calculated.

<Crystallinity>
The ratio of the heat absorption peak calorimetry derived from the crystal melting of the porous film to the heat absorption peak calorimetry derived from the crystal melting of the ethylene-vinyl alcohol-based copolymer constituting the porous film (heat absorption peak calorimetry of the porous film / ethylene-vinyl). The heat absorption peak calorific value of the alcohol-based copolymer) is the peak of the second cycle obtained by measuring the porous film and the ethylene-vinyl alcohol-based copolymer with a differential scanning calorimeter (DSC) under the following conditions. The values were calculated as the heat absorption peak calorimetry derived from the crystal melting of the porous membrane and the heat absorption peak calorimetry derived from the crystal melting of the ethylene-vinyl alcohol-based copolymer constituting the porous membrane, respectively.
Measurement condition:
Measuring device: TA Instruments Japan Inc. DISCOVERY DSC / DSC25
Sample weight 2 mg
Heating rate 10 ° C / min Scanning temperature 0-200 ° C

<Tensile strength>
The tensile strength was calculated with a test piece of JIS K 7162-1B by a tensile tester under the following conditions.
Measurement condition:
Measuring device: Autograph AG5000B, manufactured by Shimadzu Corporation Temperature: 25 ° C
Distance between chucks: 70 mm
Test speed: 500 mm / min Test piece: Dumbbell type (test part width 10 mm)

(4) Evaluation of Battery Characteristics of Separator The battery characteristics of the non-aqueous electrolyte battery using the obtained separator were evaluated according to the following method.

<Manufacturing of negative electrode for batteries>
96 parts by mass of artificial graphite (FSN-1, manufactured by Sugisugi, China) as an active material for a negative electrode, and 2 mass by mass of an SBR emulsion aqueous solution (TRD2001, manufactured by JSR Co., Ltd., 48.3% by mass) as a binder. 1 part by mass of CMC-Na (sodium carboxymethyl cellulose; cellogen BSH-6, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., 10% by mass) as a thickener, and Super-P as a conductivity aid (conductivity-imparting agent). 1 part by mass of (manufactured by Timcal Co., Ltd.) as a solid content was put into a special container and kneaded using a planetary stirrer (ARE-250, manufactured by Shinky Co., Ltd.) to prepare a slurry for electrode coating. The composition ratio of the active material and the binder in the slurry is graphite powder: conductive auxiliary agent: SBR: CMC-Na = 96: 1: 2: 1 (mass ratio) as a solid content.

<Manufacturing of negative electrode for batteries>
The obtained electrode coating slurry was coated on the copper foil (CST8G, manufactured by Fukuda Metal Leaf Powder Industry Co., Ltd.) of the current collector using a bar coater (T101, manufactured by Matsuo Sangyo Co., Ltd.) at room temperature (T101, manufactured by Fukuda Metal Leaf Powder Industry Co., Ltd.). After primary drying at 24.5 ° C.), it was rolled using a roll press (manufactured by Hosen Co., Ltd.). Then, after punching as a battery electrode (φ14 mm), a coating electrode for a coin battery was produced by secondary drying at 140 ° C. for 3 hours under reduced pressure conditions.

<Making coin batteries>
The coating electrode for the coin battery obtained above was transferred to a glove box (manufactured by Miwa Seisakusho Co., Ltd.) in an argon gas atmosphere. A metallic lithium foil (thickness 0.2 mm, φ16 mm) was used for the positive electrode. Further, the porous film obtained above was used as a separator, and vinylene carbonate (VC) was added to ethylene carbonate (EC) and ethyl methyl carbonate (EMC) of _{lithium hexafluorophosphate (LiPF 6) as an electrolytic solution.} A coin cell (2032 type) was prepared by injecting using a mixed solvent system (1M-LiPF ₆ , EC / EMC = 3/7% by volume, VC2% by mass).

<Resistance measurement>
Using the coin battery produced above, AC impedance measurement was performed with an impedance measuring device (potential / galvanostat (SI1287, manufactured by Solartron) and a frequency response analyzer (FRA, manufactured by Solartron)). Place the coin battery in a constant temperature bath at 25 ° C. and -20 ° C., a frequency 0.01-10 ⁶ Hz, by the AC impedance method at a voltage amplitude 10 mV, was measured impedance spectrum of the test battery. A diagram of the measured impedance spectrum on a complex plane (call call plot) defined by a resistance component axis (Z axis, real number axis) and a capacitive component axis (Z axis, imaginary number axis), including an arcuate part. The diameter of the arcuate part when represented by is the value of the interface resistance (Rin) with the separator, and the value of the resistance component axis (Z axis, real number axis) when the capacitive component axis (Z axis, imaginary axis) is 0. The conductivity at 25 ° C. and −20 ° C. was calculated as the solution resistance (Rsol), respectively. The results are shown in Table 1.

2. Example 2
A separator was prepared in the same manner as in Example 1 except that an ethylene-vinyl alcohol copolymer powder (manufactured by Kuraray, F101B) having an ethylene content of 32 mol% was used and the temperature of the coagulating solution was set to 30 ° C. Each physical property was evaluated. Further, a coin battery was manufactured in the same manner as in Example 1, and resistance was measured. The results are shown in Table 1.

3. 3. Example 3
Except for the fact that 27 mol% ethylene-vinyl alcohol copolymer powder (manufactured by Kuraray, L171B) containing ethylene was used and dissolved in a mixed solvent of water / 1-propanol = 45/55 (volume ratio) at 70 ° C. for 3 hours. Prepared a separator by the same method as in Example 2, and evaluated each physical property by the same method as in Example 1. Further, a coin battery was produced in the same manner as in Example 1, and resistance was measured. The results are shown in Table 1.

4. Example 4
Separators were prepared in the same manner as in Example 1 except that an ethylene-vinyl alcohol copolymer powder having an ethylene content of 48 mol% (manufactured by Kuraray, G156B) was used, and each physical characteristic was evaluated. Further, a coin battery was produced in the same manner as in Example 1, and resistance was measured. The results are shown in Table 1.

5. Example 5
A separator was prepared in the same manner as in Example 1 except that a mixed solvent of water / 1-propanol = 40/60 (volume ratio) was used as the mixed solvent of the mixed solution for forming a porous membrane. Each physical property was evaluated. Further, a coin battery was produced in the same manner as in Example 1, and resistance was measured. The results are shown in Table 1.

6. Example 6
A separator was prepared in the same manner as in Example 1 except that a mixed solvent of water / 1-propanol = 45/55 (volume ratio) was used as the mixed solvent of the mixed solution for forming a porous membrane, and each physical property was adjusted. evaluated. Further, a coin battery was produced in the same manner as in Example 1, and resistance was measured. The results are shown in Table 1.

7. Example 7
Separator was prepared by the same method as in Example 1 except that the temperature of the coagulating liquid was set to 15 ° C., and each physical property was evaluated. Further, a coin battery was produced in the same manner as in Example 1, and resistance was measured. The results are shown in Table 1.

8. Example 8
Separator was prepared by the same method as in Example 1 except that the immersion time was set to 1 minute, and each physical property was evaluated. Further, a coin battery was produced in the same manner as in Example 1, and resistance was measured. The results are shown in Table 1.

9. Comparative Example 1
Separator was prepared by the same method as in Example 1 except that the immersion time was set to 60 minutes, and each physical property was evaluated. Further, a coin battery was manufactured in the same manner as in Example 1 and an attempt was made to measure the resistance, but 3 out of 20 short-circuited cells were generated, and the cell manufacturing stability was poor.

10. Comparative Example 2
Separator was prepared by the same method as in Example 1 except that the temperature of the coagulating liquid was set to 5 ° C., and each physical property was evaluated. Further, a coin battery was produced in the same manner as in Example 1, and resistance was measured. The results are shown in Table 1.

11. Comparative Example 3
A coin battery was produced by the same method as in Example 1 except that a commercially available polypropylene-based separator (Cellguard # 2400, film thickness: 25 μm, pore diameter 0.043 μm, manufactured by Polypore) was used as the separator. Further, the resistance was measured by the same method as in Example 1. The results are shown in Table 1.

12. Example 9
Separator was prepared in the same manner as in Example 1 except that citric acid (Wako Pure Chemical Industries, Ltd. was added in an amount of 0.05% by mass) to the coagulated liquid, and each physical property was evaluated. Further, Example 1 was carried out. A coin cell was produced in the same manner as in the above, and resistance was measured. The results are shown in Table 2. In Examples 9 to 12, a structure derived from citric acid, oxalic acid or terephthalic acid was contained in the obtained separator. Was confirmed by infrared spectroscopy.

13. Example 10
Separators were prepared in the same manner as in Example 9 except that the amount of citric acid was 0.10% by mass, and each physical property was evaluated. Further, a coin battery was produced in the same manner as in Example 1, and resistance was measured. The results are shown in Table 2.

14. Example 11
Separators were prepared in the same manner as in Example 9 except that the amount of citric acid was 1.00% by mass, and each physical property was evaluated. Further, a coin battery was produced in the same manner as in Example 1, and resistance was measured. The results are shown in Table 2.

15. Example 12
Separators were prepared in the same manner as in Example 10 except that an ethylene-vinyl alcohol copolymer powder (manufactured by Kuraray, F101B) having an ethylene content of 32 mol% was used, and each physical characteristic was evaluated. Further, a coin battery was manufactured in the same manner as in Example 1, and resistance was measured. The results are shown in Table 2.

16. Example 13
Separators were prepared in the same manner as in Example 10 except that oxalic acid (Wako Pure Chemical Industries, Ltd.) was used instead of citric acid, and each physical property was evaluated. Further, in the same manner as in Example 1, the coin battery Fabrication was performed and resistance was measured. The results are shown in Table 2.

17. Example 14
Separators were prepared in the same manner as in Example 10 except that terephthalic acid (Wako Pure Chemical Industries, Ltd. was used instead of citric acid, and each physical property was evaluated. Further, the coin battery was evaluated in the same manner as in Example 1. Fabrication was performed and resistance was measured. The results are shown in Table 2.

The separators of Examples 1 to 14 according to the present invention showed an improvement in conductivity at a low temperature, which is useful as a battery, as compared with the general-purpose separator shown in Comparative Example 3. In addition, the liquid absorbency is high, the permeation time of the electrolytic solution after the injection is sufficiently short, and the aging time after the injection of the electrolytic solution, which is a factor that lowers the productivity in the battery assembly process, can be shortened. It is considered that productivity can be improved not only in the separator manufacturing process but also in the battery manufacturing process. On the other hand, in the separator produced in Comparative Example 1 having a long immersion time, the pore volume in the pore diameter range of 0.1 to 1 μm with respect to the pore volume in the pore diameter range of 0.01 to 10 μm in the pore distribution. The ratio of these was less than 80%, the pore diameter was large, the porosity was high, and the number of short-circuited batteries increased. On the other hand, in the separator produced by Comparative Example 2 in which the temperature of the coagulating liquid was low and the temperature of the mixed liquid for forming a porous membrane was large, the porosity and the pore diameter were small, and the separator had high resistance. Further, in the separators of Examples 9 to 14 using the ethylene-vinyl alcohol-based copolymer having a crosslinked structure, improvement in tensile strength and liquid absorption was confirmed.

Claims (10)

It is composed of a porous membrane composed of an ethylene-vinyl alcohol-based copolymer, and in the porous membrane, the pore diameter is 0. A separator for a non-aqueous electrolyte battery having a pore volume ratio in the range of 1 to 1 μm of 80% or more. The separator for a non-aqueous electrolyte battery according to claim 1, wherein the porosity of the porous membrane is 20% or more. The ratio of the endothermic peak heat quantity derived from the crystal melting of the porous film and the endothermic peak heat quantity derived from the crystal melting of the ethylene-vinyl alcohol-based copolymer constituting the porous membrane (porous) measured by the differential scanning calorimeter. The separator for a non-aqueous electrolyte battery according to claim 1 or 2, wherein the endothermic peak calorie of the film / the endothermic peak calorie of the ethylene-vinyl alcohol-based copolymer) is 1.10 to 3.50. The separator for a non-aqueous electrolyte battery according to any one of claims 1 to 3, wherein the porous membrane is in the form of a flat membrane having a thickness of 1 μm or more and less than 50 μm. The non-aqueous electrolyte battery according to any one of claims 1 to 4, wherein the ethylene-vinyl alcohol-based copolymer has an ethylene content of 20 to 60 mol% and a saponification degree of 80 mol% or more. Separator. The separator for a non-aqueous electrolyte battery according to any one of claims 1 to 5, wherein the ethylene-vinyl alcohol-based copolymer has a crosslinked structure. A method for producing a separator for a non-aqueous electrolyte battery, which comprises a step of wet-coagulating a solution containing an ethylene-vinyl alcohol-based copolymer and a solvent.
The wet coagulation step comprises immersing a solution containing the ethylene-vinyl alcohol copolymer and a solvent, which may be applied to a substrate, in a coagulation liquid for 1 second to 30 minutes.
A production method, wherein the absolute value of the difference between the temperature of the solution and the temperature of the coagulating solution is 35 ° C. or less, and the solvent constituting the solution is a mixed solvent containing water and alcohol. The production method according to claim 7, wherein the temperature of the coagulating liquid is 10 to 70 ° C. The production method according to claim 7 or 8, wherein the coagulating liquid contains 50% by mass or more of water with respect to the total mass of the coagulating liquid. A non-aqueous electrolyte battery comprising the separator for a non-aqueous electrolyte battery according to any one of claims 1 to 6.