KR20140081779A - Method for producing porous membrane, porous membrane, battery separator, and battery - Google Patents

Abstract

A porous film (A) to be treated is placed in a coating treatment apparatus, a specific raw material is present in a gaseous state in the apparatus, and a coating treatment is carried out while the additive gas is coexisted, And a porous film (A ') obtained by forming a film containing constituent elements of the additive gas.
A porous membrane having excellent heat shrinkability, shutdown characteristics, anti-meltdown characteristics, wettability with an electrolytic solution, and electrochemical stability without deteriorating the ion permeability and mechanical properties required for a separator for a battery, and a battery separator using the same do.

Description

TECHNICAL FIELD [0001] The present invention relates to a porous membrane, and a separator and a battery for the same. BACKGROUND ART [0002]

The present invention relates to a porous film excellent in both shutdown and anti-meltdown characteristics and excellent in wettability and oxidation resistance with an electrolytic solution. More specifically, a polyolefin porous film useful as a separator for a battery which is excellent in ion permeability, excellent in safety due to its low heat shrinkage ratio, shutdown characteristic, and anti-meltdown characteristic in the vicinity of 200 캜 and excellent in wettability with electrochemical solution and electrochemical stability A manufacturing method thereof, and a battery and a capacitor using the porous film.

BACKGROUND ART [0002] Thermoplastic resin porous membranes are widely used as separation membranes for materials, selective permeable membranes, barrier ribs, and the like. For example, various kinds of filters such as a reverse osmosis filtration membrane, an ultrafiltration membrane, a microfiltration membrane, and a diaphragm for a battery used for a lithium ion battery or a nickel hydride battery or a diaphragm for an electrolytic capacitor, such as a breathable waterproof medical treatment, are used. Among them, a polyolefin (hereinafter abbreviated as PO) porous film is used as a separator for a lithium ion battery, and the performance of a polyolefin (PO) porous film is deeply related to battery characteristics, battery productivity, and battery safety. Therefore, excellent ion permeability, mechanical properties, low heat shrinkage, shutdown characteristics, and anti-meltdown properties are required.

Lithium-ion batteries are expected to be used in a wide range of applications such as mobile phones, power tools, transportation (automobiles, buses), and battery applications (smart grids, etc.) Is predicted. These batteries are produced by impregnating an electrolyte solution in which a lithium salt is dissolved in a pore of a film with a separator made of an electrically insulating porous film interposed between the positive and negative electrodes and laminating the positive and negative electrodes and the separator, Structure is main. It is necessary to take various safety measures against the problem caused by the high capacity and the high energy density of the lithium secondary battery, for example, the battery temperature rises largely due to a short circuit in and out of the battery. In order to solve such a problem, various attempts have been made to apply various designs to the separator.

Particularly, as a safety measure to which a separator can contribute, shutdown characteristics and anti-meltdown characteristics are attracting attention. For example, when the internal temperature of the battery rises due to overcharging, external or internal short-circuit, etc., a part of the separator melts to close the gap to interrupt the current. This is called shutdown (also referred to as fuse) The temperature is called the shutdown temperature. Further, when the temperature rises, the separator melts and flows to form a large hole. This is referred to as meltdown, and the temperature at this time is referred to as meltdown temperature. When the separator melts and flows, short-circuiting occurs between the electrodes, resulting in a more dangerous state. For this reason, it is required to lower the shutdown temperature of the separator and increase the meltdown temperature of the nonaqueous electrolyte battery separator.

With respect to such safety requirements, it has been proposed to improve the thermoplastic resin composition used in the separator and to form an inorganic particle layer or a heat-resistant resin layer on the surface of the separator. For example, a polyolefin porous film having polypropylene as a main component and a layer mainly composed of polyethylene between both surface layers (Patent Document 1), a porous film (A1) composed of a resin having a melting point of 150 DEG C or less, (Patent Document 2) in which a porous film (B1) made of a resin having a transition temperature higher than 150 占 폚 is integrated (Patent Document 2), a porous film (B2) comprising a polymer having a pyrolysis temperature of 200 占 폚 or higher and an organic powder and / ) And a porous film A2 made of a thermoplastic resin are laminated (Patent Document 3).

However, in improving the composition of the thermoplastic resin reported in Patent Document 1, sufficient anti-meltdown characteristics can not be achieved due to the limit of the heat resistance of the thermoplastic resin as the raw material. In addition, a porous film (B) comprising a porous film (A) made of a thermoplastic resin and a porous film (B) made of a heat resistant resin (which may disperse organic and / or inorganic particles in a heat resistant resin) reported in Patent Document 2 or Patent Document 3 The interlaminar adhesive strength between the porous films is low in the membrane, and the solution, slurry or gel-like heat resistant resin for forming the porous membrane (B) in the pores of the porous membrane (A) There is a problem that the permeation resistance (ion permeability) of the entire laminated porous film is deteriorated. Further, since lamination is required, there is a limit to making the entire multilayer porous film thinner, and there is a possibility that it will not be possible to cope with high capacity of the battery to be advanced in the future.

On the other hand, physical and chemical vapor deposition has also been proposed as a surface treatment method for a porous film. For example, for the purpose of hydrophilizing a porous material, a method of plasma-treating the surface and pores of the porous material by irradiating plasma in an inert gas or a mixed gas of an inert gas and a reactive gas (Patent Document 4) A PO microporous membrane surface-modified with a hydrophilic polymer (Patent Document 5) has been reported. Similarly, there has been reported a battery separator (Patent Document 6) that prevents carbonization of the PO film contacting with the positive electrode by depositing inorganic particles on the organic porous film by physical vapor deposition and is difficult to short-circuit even when charged for a long time. Attempts have been made to improve various properties of the separator by physical and chemical vapor deposition, but no report has been made to improve the anti-meltdown property.

Examples of requirements for the separator include improvement in wettability with an electrolytic solution, improvement in electrochemical stability, and the like. In the case of poor wettability with the electrolytic solution, it takes time to inject the electrolyte at the time of manufacturing the battery, resulting in a problem of deteriorating the productivity. In addition, the electrolyte is liable to be dried out (dry out) There is a fear that it may significantly deteriorate. In addition, when the electrochemical stability is low, the separator may be deteriorated in insulation due to carbonization or the like, and the self-discharge accelerates, which may lead to high capacity and high energy density of the battery.

Japanese Patent Application Laid-Open No. 2008-255307 Japanese Patent Application Laid-Open No. 2007-125821 Japanese Patent Application Laid-Open No. 2006-348280 Japanese Patent Application Laid-Open No. 2007-80588 Japanese Patent Application Laid-Open No. 2011-12238 Japanese Patent Application Laid-Open No. 2005-196999

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a separator for a battery, which does not deteriorate ion permeability and mechanical characteristics required for a separator for a battery, and which has excellent heat shrinkability, shutdown characteristics, A porous film and a battery separator using the porous film are provided.

In order to solve the above problems, the porous film of the present invention has any one of the following (1) or (2). In other words,

(1) A porous film (A) to be treated is placed in a plasma coating treatment apparatus, and at least one raw material selected from a raw material group selected from the group of raw materials shown in the following Group 1 is allowed to exist in a gaseous state in the apparatus, (A ') obtained by forming a coating film containing a raw material and constituent elements of an additive gas on at least one surface of the porous film (A)

or

(2) A porous film (A) to be treated in a plasma coating treatment apparatus is placed, and at least one raw material selected from a raw material group represented by the following group 1 is allowed to exist in a gaseous state in the apparatus, (A ') obtained by forming a film containing constituent elements of a raw material and an additive gas on a surface of a fiber, pulp or fibril to form a porous film (A) by carrying out a coating treatment in coexistence with a gas.

Here, the group 1 refers to the following raw material groups (1) to (9).

(1) a silane compound represented by SiR ¹ R ² R ³ R ⁴ (wherein each of R ¹ to R ⁴ is any one of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group, The carbon chain may be saturated or unsaturated. Further, for example, a ring may be formed of Si and substituent groups R ¹ and R ² , and the carbon chain may be saturated or unsaturated. )

(2) a disiloxane compound represented by O- (SiR ¹ R ² R ³ ) ₂ (wherein each of R ¹ to R ³ is any one of hydrogen, halogen, and an alkyl group having 1 to 10 carbon atoms, The carbon chain may be saturated or unsaturated. Further, for example, a ring may be formed of Si and substituent groups R ¹ and R ² , and the carbon chain may be saturated or unsaturated. )

(3) - (OSiR ¹ R ² ) _n - (wherein R ¹ and R ² are each any one of hydrogen, halogen and alkyl groups of 1 to 10 carbon atoms, and the carbon chain may be linear The carbon chain may be saturated or unsaturated. The ring may be formed of, for example, Si and substituents R ¹ and R ² . N is an integer of 2 to 20)

(4) a silazane compound represented by N- (SiR ¹ R ² R ³ ) _m R ⁴ _{3 -m} wherein each of R ¹ to R ⁴ is any one of hydrogen, halogen and an alkyl group having 1 to 10 carbon atoms , the carbon chain is good even if the branch may be straight chained, and may be each the same or the number of carbon atoms is different. in addition, the carbon chain may be a good and unsaturated may be saturated. also, for example, switch to Si as the substituents R ¹ and R ² M may be an integer of 1 to 3)

(5) - (NR ¹ SiR ² R ² ) ₁ - (wherein R ¹ to R ³ are each any one of hydrogen, halogen, and an alkyl group having 1 to 10 carbon atoms, and the carbon chain is The carbon chain may be saturated or unsaturated. Further, even if Si and the substituent groups R ¹ and R ² form a ring, for example, the carbon chain may be saturated or unsaturated. L is an integer of 2 to 20)

(6) a titanate compound represented by TiR ¹ R ² R ³ R ⁴ wherein each of R ¹ to R ⁴ is any one of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group, The carbon chain may be saturated or unsaturated. Further, for example, a ring may be formed of Ti and substituent groups R ¹ and R ² , and the carbon chain may be saturated or unsaturated. )

(7) Aromatic hydrocarbon compound

(8) Ar- (X) an aromatic compound having a polar group represented by the _k least one at least (wherein, Ar represents an aromatic hydrocarbon or heteroaromatic compound with water, -X is -COOH, -SO ₃ H, -OR , and _{-CO-R, -CONHR, -SO 2} NHR, -NHCOOR, -NHCONHR, -NH 2 any one, k is an integer of 1 or more and 3, R is an alkyl group of 1 to 10 carbon atoms, an alkyl group of carbon The chain may be linear or branched, and may have a different carbon number or the same carbon number. The carbon chain may be saturated or unsaturated)

(9) Lactam compound

The separator for a battery of the present invention has the following constitution. In other words,

And the porous membrane (A ').

Further, the battery of the present invention has the following configuration. In other words,

A positive electrode, a negative electrode, an electrolyte, and at least one separator for a battery according to claim 11.

Further, the porous film of the present invention is preferably coated with a roll-to-roll process.

It is preferable that the porous film of the present invention has at least one kind of additive gas selected from the group 2 gas.

Here, group 2 refers to the next group of gases.

Hydrogen, nitrogen, oxygen, carbon dioxide, nitrous oxide, nitrogen dioxide, hydrocarbons having 3 or less carbon atoms

In the porous film of the present invention, it is preferable that the raw material to be present in a gaseous state at the time of coating treatment is a solid or a liquid at room temperature and normal pressure.

The porous film of the present invention comprises at least one kind of raw material selected from the group of raw materials represented by groups 1- (2), (4), (6) and (8), and the additive gas is nitrogen, a hydrocarbon having 3 or less carbon atoms, Is preferable.

The porous membrane of the present invention has a specular resistance X (sec / 100ccAir / 20 m) of the porous membrane (A) before coating treatment and a specular resistance X '(sec / 100ccAir / Satisfies X '/ X ≤ 2.0.

The relationship between the weight W (g / m2) of the porous film (A) and the weight W '(g / m2) of the coated porous film (A') is W'-W? ) Is satisfied.

It is preferable that the porous film of the present invention is produced by a wet process.

(Effects of the Invention)

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a porous film having excellent low heat shrinkability, shutdown property, anti-meltdown property, wettability with an electrolytic solution and electrochemical stability without deteriorating ion permeability and mechanical properties required for a battery separator, A separator can be provided.

The porous film (A ') of the present invention is required to have a coating formed thereon in order to improve the anti-meltdown property. As a method of forming the coating film, a voltage is applied between the electrodes in the plasma coating apparatus to ionize the raw material molecules present in a gaseous state, and the surface of at least one surface of the porous film (A) or the fiber forming the porous film (A) Or a method of forming a chemical vapor deposition film by depositing a chemical species containing constituent elements of the raw material gas on the fibril surface.

The coating film in the present invention is a chemical vapor deposition film formed by chemical vapor deposition (hereinafter referred to as CVD). It excites a source gas by applying energy such as heat, light, or electromagnetic wave to the raw material gas, And is a deposited film made of a chemical species including a constituent element of a raw material gas formed on a substrate surface by a chemical reaction. The CVD method includes thermal CVD, organic metal CVD, plasma CVD, photo CVD, and laser CVD. The present invention is a porous film formed by plasma CVD. Among them, in the present invention, high-frequency plasma CVD is preferably used from the viewpoint of the cost of the processing apparatus.

The coating film of the present invention needs to have excellent heat resistance in order to improve the anti-meltdown property. It is necessary to use at least one kind of raw material selected from the raw material group shown in the group 1, and a plurality of kinds of raw materials can be used in an arbitrary ratio.

The silane compound represented by the group 1- (1): SiR ¹ R ² R ³ R ⁴ in the present invention means a silane compound represented by the following general formula (1): hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms or an alkoxy group The carbon chain may be saturated or unsaturated. Further, for example, a ring may be formed of Si and substituent groups R ¹ and R ² , and the carbon chain may be saturated or unsaturated. ). Specific examples thereof include tetramethylsilane, diethoxydimethylsilane, and tetraethoxysilane.

The disiloxane compound represented by the group 1- (2): O- (SiR ¹ R ² R ³ ) ₂ in the present invention means a compound in which two silicon atoms are bonded to oxygen and hydrogen, halogen, (Wherein the carbon chain may be linear or branched, and the carbon numbers may be different or the same, respectively.) The carbon chain may be saturated or unsaturated. In addition, for example, Si And R < ² > together with the substituents R < ¹ > and R < ² >). Specifically, hexamethyldisiloxane, hexaethyldisiloxane and the like are exemplified, and hexamethyldisiloxane is preferably used.

The cyclic siloxane compound represented by the group 1- (3): - (OSiR ¹ R ² ) _n - in the present invention means a cyclic siloxane compound in which oxygen and silicon are bonded in a cyclic manner and silicon is further substituted with halogen, , Or an alkoxy group (wherein the carbon chain may be linear or branched or may have a different carbon number or may be the same). The carbon chain may be saturated or unsaturated. And R < ¹ > and R < ² > may form a ring). Specific examples thereof include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane and the like. The number of silicon atoms in the molecule (n in the formula) is preferably in the range of 2 to 20, and more preferably in the range of 2 to 5 from the viewpoint of handling.

The silazane compound represented by the group 1- (4): N- (SiR ¹ R ² R ³ ) _m R ⁴ _{3 -m} in the present invention means a compound in which 1 to 3 silicon atoms are bonded to nitrogen, , A halogen, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group (wherein the carbon chain may be linear or branched, and the carbon numbers may be different or the same). The carbon chain may be saturated or unsaturated . It is also possible to form a ring with Si and substituents R ¹ and R ² , for example). M is an integer of 1 to 3. Specifically, hexamethyldisilazane, hexaethyldisiloxane and the like are exemplified, and hexamethyldisilazane is preferably used.

The cyclic silazane compound represented by the formula 1- (5): - (NR ¹ SiR ² R ² ) _l - in the present invention means a compound in which nitrogen and silicon of the same number are bonded in a cyclic manner, An alkyl group having 1 to 10 carbon atoms, or an alkoxy group (wherein the carbon chain may be linear or branched, and the carbon numbers may be different or the same.) The carbon chain may be saturated or unsaturated. For example, Si may form a ring with substituents R ¹ and R ² ). Specific examples thereof include hexamethylcyclotrisilazane, octamethylcyclotetrasilazane and the like. The number of silicon atoms in the molecule (1 in the formula) is preferably in the range of 2 to 20, and more preferably in the range of 2 to 5 from the viewpoint of handling.

The titanate compound represented by the group 1- (6): TiR ¹ R ² R ³ R ⁴ in the present invention means a titanium compound in which titanium, hydrogen, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group The carbon chain may be saturated or unsaturated. Further, even if Ti and a substituent R ¹ and R ² form a ring, for example, the carbon chain may be saturated or unsaturated. Lt; / RTI > Specific examples thereof include tetramethyl titanium, tetraethoxy titanium and the like.

In the present invention, the group 1- (7): aromatic hydrocarbon compound is a benzene-based aromatic compound, specifically benzene, naphthalene, anthracene, phenanthrene and the like. In the present invention, naphthalene and anthracene which are solid at room temperature and have sublimation properties can be preferably used from the viewpoints of handling property and anti-meltdown property.

The aromatic compound having at least one polar group represented by the group 1- (8): Ar- (X) _k in the present invention means that the hydrogen atom of the aromatic compound is -COOH, -SO ₃ H, -OR, -CO- R, at _{-CONHR, -SO 2 NHR, -NHCOOR,} -NHCONHR, -NH 2 ( where, R is an aromatic group or an alkyl group having 1 to 10 carbon atoms, the carbon chain may optionally have a branch may be straight-chain, respectively, carbon atoms K is an integer of 1 or more and 3 or less, Ar is an aromatic hydrocarbon or a heteroaromatic compound, and k is an integer of 1 or more and 3 or less, The total number of atoms such as carbon, nitrogen, oxygen, and sulfur constituting the aromatic compound is in the range of 5 to 10. Specific examples thereof include aromatic carboxylic acids such as benzoic acid and phthalic acid, and aromatic sulfonic acids such as benzenesulfonic acid. In the present invention, compounds having a room temperature solidity and having a sublimation property, specifically, terephthalic acid, melamine and the like can be preferably used from the viewpoints of handling property and anti-meltdown property.

In the present invention, the group 1- (9): a lactam compound is an intramolecular cyclic amino compound, and specifically,? -Lactam (3-membered ring),? -Lactam (4-membered ring),? -Lactam . In the present invention, from the viewpoint of the anti-meltdown property, a lactam compound having 7 or less ring members can be preferably used.

At the time of forming the coating film in the present invention, at least one raw material selected from the raw material group represented by the group 1 in the coating treatment apparatus is present in a gaseous state, and at least one kind of additive gas From the viewpoint of the anti-meltdown property, the adhesion between the porous film (A) and the coating film, and the flexibility of the coating film. It is presumed that the constituent elements of the additive gas are introduced into the film to improve the flexibility of the film, and at the same time, the adhesion between the porous film and the film and the anti-meltdown property are improved.

Here, the additive gas of group 2 is hydrogen, nitrogen, oxygen, carbon dioxide, nitrous oxide, nitrogen dioxide, and hydrocarbons having 3 or less carbon atoms. Hydrocarbons having 3 or less carbon atoms may be saturated or unsaturated, and specific examples thereof include methane, ethane, propane, ethylene, propylene, and acetylene.

In the coating treatment, a plurality of kinds of gases selected from the group 2 are used in an arbitrary ratio in the coating treatment apparatus in coexistence with the raw material gas. The ratio of the total amount of the raw materials shown in the group 1 existing in the coating apparatus to the total amount of the additive gases selected from the group 2 is not particularly limited and coating treatment can be carried out by coexisting in a coating apparatus at an arbitrary ratio.

Examples of the preferable combination of the raw material (gas) shown in the group 1 and the additive gas shown in the group 2 include a disiloxane compound of the group 1- (2), a silazane compound of the group 1- (4) (6), or a combination of an aromatic hydrocarbon having at least one polar group of the group 1- (8) and carbon dioxide, hydrocarbon or nitrogen as a preferable combination from the viewpoints of anti-meltdown properties and flexibility of the coating . However, the combination of the raw material and the additive gas is not limited to this.

The method of introducing the raw material selected from the raw material group of Group 1 of the present invention and the additive gas selected from Group 2 into the plasma coating apparatus is not particularly limited and a method of introducing the raw material gas directly into the apparatus, A method of vaporizing the solid raw material by heating or the like and introducing it into the apparatus or a method of vaporizing the raw material by installing an evaporation source in the apparatus. In the present invention, in order to make the concentration of various gases in the plasma coating apparatus constant, it is preferable to introduce various kinds of gases which have been vaporized in advance into the plasma coating apparatus through a flow meter or the like. When introduced into the apparatus, the additive gas selected from the group 2 can be used as the carrier gas of the source gas shown in the group 1.

The plasma coating treatment in the present invention is preferably performed in a so-called roll-to-roll process in which the porous film (A) is continuously drawn and the coating process is performed, and the porous film (A ' From the viewpoint of the quality stability of the film.

As a specific example of the plasma coating apparatus according to the present invention, a decompression meter for decompressing the interior of the processing apparatus, a decompression vessel connected to a supply system for introducing the raw material and / or the additive gas into the processing apparatus are exemplified, (A), a plasma generating source, and a winding device for winding the porous film (A ').

In the present invention, the roll of the porous film (A) is set in a coating treatment apparatus, the inside of the apparatus is depressurized and the porous film (A ') is coated as a roll, It is preferable to carry out coating treatment. The porous film (A) and the porous film (A ') are usually wound around a core to form a roll. The material of the core used is a thermoplastic resin such as ABS (acrylonitrile-butadiene styrene) resin, polyethylene resin, Can be preferably used since the amount of volatile components from the core is small and the surface of the porous film and the inside of the coating treatment apparatus are less likely to be contaminated.

In the plasma coating apparatus according to the present invention, in the region irradiated with the plasma, it is preferable that a support is provided for supporting the porous film (A), and the shape of the support is not limited to a plane or a curved surface. The support preferably has a cooling function so that the surface of the support can be kept warm. In the case of having a cooling function, temperature rise due to plasma irradiation is effectively prevented, and the porous film (A) hardly shrinks in heat, so that the planarity is not damaged.

In the present invention, the discharge condition of the plasma is not particularly limited, but the pressure is preferably in the range of 0.01 to 1,000 Pa, more preferably in the range of 0.1 to 100 Pa. When the pressure is within the preferable range, the plasma is efficiently generated, and the film is efficiently formed because the raw material gas is appropriately present.

In the coating process of the present invention, in the case where the film thickness uniformity of the coating can not be maintained in the region to be coated, the shape of the plasma electrode is appropriately changed, and a shielding plate or the like It is possible to ensure the uniformity of film thickness of the film by controlling the amount of plasma irradiated.

Hereinafter, the characteristics of the porous film (A ') of the present invention will be described in detail.

The porous film (A ') of the present invention needs to have a film formed from at least one kind of raw material selected from the group 1 and at least one kind of additive gas selected from the group 2. The deposition amount of the coating film is preferably 0.05 g / m 2 or more and 2 mg / m 2 or less. When the deposition amount of the coating film is within the preferable range, it is possible to improve the anti-meltdown characteristic and to effectively prevent the rise of the durability of the durability, so that the degree of inhibition of ion movement in the battery is small, outstanding. The deposition amount can be obtained as W'-W when the weight of the porous film (A) is W (g / m 2) and the weight of the porous film (A ') is W' (g / .

The deposition amount of the coating film of the porous film (A ') of the present invention can be appropriately selected depending on the type and concentration of the raw material gas and the additive gas in the treatment apparatus, the pressure in the treatment apparatus, the output of microwave or high frequency for generating plasma, It is possible to arbitrarily adjust the speed by adjusting the speed.

The durability of the porous membrane (A ') of the present invention is such that the durability of the porous membrane (A) before coating is Xsec / 100 ccir / 20 m and the durability of the porous membrane (A' sec / 100ccAir / 20 mu m, it is preferable that X '/ X ≤ 2.0 is satisfied. When the value of X '/ X is 2.0 or less, the movement of ions in the battery is not inhibited and the charge / discharge characteristics are excellent. The value of X '/ X is preferably 1.5 or less, more preferably 1.2 or less.

The heat shrinkage ratio of the porous membrane (A ') of the present invention is preferably lower than that of the porous membrane (A). In addition, it is preferable that the heat shrinkage rate at 105 ° C for 8 hours and the heat shrinkage rate at 150 ° C for 30 minutes near the meltdown temperature of the separator, which mimic the use of the battery at a high temperature, are lower than those of the porous film (A). From the viewpoint of safety, the heat shrinkage ratio is preferably as low as possible, and more preferably as low as both MD and TD from the viewpoint of safety.

The porous film (A ') of the present invention has a shutdown characteristic, and has a shutdown temperature in the range of 70 to 150 占 폚 from the viewpoint of safety. The shutdown temperature of the porous film A 'can be controlled by the selection of the porous film A, but the shutdown temperature T' of the porous film A 'may vary depending on the composition of the film, the deposition amount, A " of the shutdown temperature Ts. From the viewpoint of safety, it is preferable that the rise width (T's-Ts) of the shutdown temperature is small, preferably (T's-Ts) 5 deg. C, more preferably (T's-Ts) 0 deg.

The melt down temperature (T'm) of the porous film (A ') of the present invention is preferably higher than the melt down temperature of the porous film (A). From the viewpoint of safety, it is preferable that the increase (T'm-Tm) of the meltdown temperature is as large as possible, preferably (T'm-Tm)? 20 deg. C, more preferably to be.

The puncture strength of the porous film (A ') of the present invention can be controlled by the design and selection of the porous film (A), but the puncture strength of the porous film (A') may vary depending on the composition of the film, May be slightly lower than the puncture strength (P) of the porous film (A). (1-P '/ P) = 0.2 or less, more preferably (1-P' / P) = 0.2 or less, 0.1 or less. The rate of decrease of the puncture strength can be suppressed to a low level by controlling the output of microwave or high frequency for generating the additive gas or the plasma so that the porous film (A) is not etched by the plasma.

The wettability of the porous film (A ') with the electrolytic solution of the present invention is preferably higher than that of the porous film (A). When the wettability is high, it means that the electrolyte solution is easily diffused from the surface of the porous membrane, and also means that it is easy to permeate in the thickness direction of the porous membrane. Since the wettability is high, the time required for injecting the electrolyte during the production of the battery is shortened and the productivity can be expected to be improved. In addition, occurrence of dryout of the electrolyte is prevented, There is no risk of degradation.

The electrochemical stability of the porous film (A ') of the present invention is preferably higher than that of the porous film (A). The electrochemical stability is a property related to the oxidation resistance of a separator exposed to a relatively high temperature during storage or use. If the electrochemical stability is low, the separator may be deteriorated in insulation due to carbonization or the like, and the self-discharge may accelerate to cause a problem of high capacity and high energy density of the battery.

Next, the composition of the porous film (A) will be described.

As the porous film (A) in the present invention, a porous woven fabric, a nonwoven fabric, a paper or a porous film made of an electrically insulating organic, inorganic fiber or pulp can be used. However, the electrical insulating property, uniformity of film thickness, A porous film is preferable.

The material of the porous film (A) in the present invention may be an organic material, an organic material, an inorganic material, a composite material, a natural material, or a pulp of organic fibers and / or inorganic fibers and / Pulp and the like. Specific examples of the organic fiber include synthetic fibers made of a thermoplastic polymer and natural fibers such as manila hemp. Examples of synthetic fibers made of the thermoplastic polymer include polyolefins such as polyethylene and polypropylene, and synthetic fibers such as rayon, vinylon, polyester, acrylic, polystyrene and nylon. Examples of the inorganic fibers include glass fibers and alumina fibers.

As the material of the porous film (A), polyolefins such as polyethylene and polypropylene are preferably exemplified from the viewpoint of electrical insulation and shutdown characteristics. When the porous film (A) is composed of a polyolefin, it may be a single substance or a mixture of two or more different polyolefin resins, for example, a mixture of a polyethylene resin and a polypropylene resin, and may be a copolymer of another olefin such as a copolymer of ethylene and propylene . Of the polyolefin-based resins, polyethylene and polypropylene are particularly preferred. In addition to the basic properties such as electrical insulation and ion permeability, shutdown characteristics for shutting off current at the time of abnormally increasing the temperature of the battery to suppress excessive temperature rise, and electrochemical stability.

The mass average molecular weight (Mw) of the polyolefin-based resin is not particularly limited, but is usually in the range of 1 × 10 ^{4 to} 1 × 10 ⁷ , preferably in the range of 1 × 10 ^{4 to} 5 × 10 ⁶ , And preferably in the range of 1 x 10 ^{5 to} 5 x 10 ⁶ .

The polyolefin-based resin preferably includes polyethylene. Examples of the polyethylene include ultrahigh molecular weight polyethylene, high density polyethylene, medium density polyethylene and low density polyethylene. The polymerization catalyst is not particularly limited, and polyethylene produced by a polymerization catalyst such as a chitosan catalyst, a Phillips catalyst, or a metallocene catalyst may be used. These polyethylene may be not only homopolymers of ethylene but also copolymers containing small amounts of other? -Olefins. Examples of the? -Olefins other than ethylene include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, (meth) acrylic acid, esters of (meth) Can be used.

The polyethylene may be a single material, but is preferably a mixture of two or more kinds of polyethylene. As the polyethylene mixture, a mixture of two or more kinds of ultra-high molecular weight polyethylene having different Mw, a mixture of high density polyethylene, a mixture of the same high density polyethylene, and a mixture of low density polyethylene may be used, and ultra high molecular weight polyethylene, high density polyethylene, medium density polyethylene and low density polyethylene May be used as a mixture of two or more kinds of polyethylene.

Among them, as the polyethylene mixture, a mixture of ultra high molecular weight polyethylene of 5 x 10 ⁵ or more and polyethylene having Mw of 1 x 10 ⁴ or more and less than 5 x 10 ⁵ is preferable. The Mw of the ultrahigh molecular weight polyethylene is preferably in the range of 5 10 ^{5 to} 1 10 ⁷ , more preferably in the range of 1 10 ^{6 to} 1 10 ⁷ , more preferably in the range of 1 10 ^{6 to} 5 10 ⁶ Is particularly preferable. As the polyethylene having Mw of 1 x 10 ⁴ or more and less than 5 x 10 ⁵ , any of high density polyethylene, medium density polyethylene and low density polyethylene can be used, and it is particularly preferable to use high density polyethylene. May be with a Mw of more than 1 × 10 ⁴ 5 × 10 ⁵ or more is less than a polyethylene as the Mw of the other two species, may be used in the different densities of two or more. By setting the upper limit of Mw of the polyethylene mixture to 1 x 10 ⁷ , melt extrusion can be facilitated. The content of ultrahigh molecular weight polyethylene in the polyethylene mixture is preferably 1% by weight or more, more preferably 10 to 80% by weight, based on the total weight of the mixture of polyethylene.

When containing the ultra high molecular weight polyethylene having Mw of 5 × 10 ⁵ or more in the polyethylene mixture according to the addition amount of the ultra-high molecular weight polyethylene increases and therefore there are cases in which a porous membrane pore size may be decreased. Here, for example, when the solution of the high heat-resistant resin is applied to the porous film (A) to improve the anti-meltdown property, a step for making the high heat-resistant resin layer porous is required. In addition, Heat resistance resin enters into the pores of the resin (A), thereby significantly increasing the durability of the durability. On the other hand, in the present invention, since the surface of the fibril forming the porous film (A) can be coated, the step of making the porous film is unnecessary and it is also easy to suppress the increase of the durability. A porous film having a small pore diameter and containing ultra-high molecular weight polyethylene can be used without any problem.

The ratio of the number average molecular weight (Mw) to the number average molecular weight (Mn) of the polyolefin resin and the molecular weight distribution (Mw / Mn) are not particularly limited, but are preferably in the range of 5 to 300, more preferably in the range of 10 to 100. When Mw / Mn is within the preferable range, the polyolefin solution can be easily extruded because a high molecular weight component is suitable, and a low molecular weight component is suitable, so that the strength of the obtained porous film is excellent. Mw / Mn is used as a measure of the molecular weight distribution, that is, in the case of a single polyolefin, the larger the value, the larger the molecular weight distribution is. The Mw / Mn of the polyolefin composed of a single material can be suitably adjusted by multi-terminal polymerization of polyolefin. The multistage polymerization method is preferably a two-step polymerization in which a high molecular weight component is polymerized in a first stage and a low molecular weight component is polymerized in a second stage. When the polyolefin is a mixture, the larger the Mw / Mn, the larger the difference in Mw between the components to be mixed and the smaller the difference in Mw is between the smaller Mw / Mn. The Mw / Mn of the polyolefin mixture can be appropriately adjusted by adjusting the molecular weight and mixing ratio of each component.

When a polyethylene porous film is used, polypropylene may be included together with polyethylene for the purpose of improving the anti-meltdown property and the high-temperature storage property of the battery. The Mw of the polypropylene is preferably in the range of 1 x 10 ⁴ to 4 x 10 ⁶ . As the polypropylene, block copolymers or random copolymers containing a homopolymer or other? -Olefin may be used. As other? -Olefins, ethylene is preferable. The content of the polypropylene is preferably 80% by weight or less based on 100% by weight of the entire polyolefin mixture (polyethylene + polypropylene).

For the purpose of improving the characteristics of the battery separator, the polyethylene porous film may contain polyolefin which imparts a shutdown characteristic. As the polyolefin imparting the shutdown characteristic, for example, low density polyethylene can be used. As the low-density polyethylene, at least one member selected from the group consisting of ethylene / alpha -olefin copolymers produced by a branched, linear, single site catalyst is preferable. The amount of the low-density polyethylene added is preferably 20% by weight or less based on 100% by weight of the entire polyolefin. If the addition amount of the low-density polyethylene is within the preferable range, breakage hardly occurs at the time of stretching.

The polyethylene composition containing the ultrahigh molecular weight polyethylene may optionally contain, as optional components, poly-1-butene having an Mw within a range of 1 x 10 ⁴ to 4 x 10 ⁶ , polyethylene wax having an Mw within a range of 1 x 10 ³ to 4 x 10 ⁴ , At least one polyolefin selected from the group consisting of an ethylene /? - olefin copolymer having a Mw within a range of 1 × 10 ⁴ to 4 × 10 ⁶ may be added. The amount of these optional components added is preferably 20% by weight or less based on 100% by weight of the polyolefin composition.

Hereinafter, the production method and characteristics will be described taking the case where the porous film (A) is a polyolefin porous film.

The production method of the porous film (A) in the present invention is not particularly limited, and the phase structure according to the purpose can be freely obtained by the production method. As the production method of the porous film (A), there are a foaming method, a phase separation method, a dissolution recrystallization method, a drawing pore forming method, a powder sintering method and the like. Of these, the phase separation method is preferable from the viewpoints of uniformity of the fine holes and cost. But is not limited thereto.

Examples of the production method by the phase separation method include a method in which a polyolefin and a solvent for film formation are melt kneaded, the obtained molten mixture is extruded from a die and cooled to form a gel-like molded product, and the resulting gel- And removing the film-forming solvent to obtain a porous film.

The porous film (A) may be a single-layer film or a multilayer film of two or more layers (for example, a three-layer structure of polypropylene / polyethylene / polypropylene or a three-layer structure of polyethylene / polypropylene / polyethylene).

As a method for producing a multilayered film composed of two or more layers, for example, each of the polyolefins constituting the first layer and the second layer is melted and kneaded with a solvent for film formation, and the obtained molten mixture is supplied to one die from each extruder A method of integrating the gel sheets constituting each component and pneumatic shipment, and a method of polymerizing the gel sheet constituting each layer and thermally fusing the same. The coextrusion method is more preferable because it is easy to obtain a high interlaminar bond strength and easily form a communication hole between the layers and is easy to maintain high permeability and is excellent in productivity.

The porous film (A) has a shutdown characteristic in which a hole is closed at the time of abnormality of a charge-discharge reaction, from the viewpoint of safety at the time of using the battery. Therefore, the melting point (softening point) of the constituting resin is preferably 70 to 150 占 폚, more preferably 100 to 140 占 폚. When the melting point (softening point) of the constituting resin is within the preferable range, the shutdown function is exhibited during normal use and there is no possibility that the battery is unusable. On the other hand, when the abnormal reaction occurs, the shutdown function is quickly exhibited, .

The film thickness of the porous film (A) is preferably 5 mu m or more and less than 30 mu m. The upper limit of the film thickness is more preferably 25 占 퐉, and still more preferably 20 占 퐉. The lower limit of the film thickness is more preferably 7 占 퐉, and most preferably 10 占 퐉. When the film thickness is in this preferable range, it is possible to have a film strength for maintaining practical workability and a shutdown function, and on the other hand, since the electrode area per unit volume in the battery case is not restricted, it is possible to cope with high capacity of the battery in the future. From the viewpoint of high capacity of the battery, it is preferable that the thickness of the porous film (A) is thin within a range in which no problem occurs in processability.

The upper limit of the permeation resistance (JIS P 8117) of the porous film (A) is preferably 800 sec / 100ccAir / 20um, more preferably 700sec / 100ccAir / 20um, and most preferably 600sec / 100ccAir / 20um. The lower limit of the durability is preferably 50 sec / 100ccAir, more preferably 70sec / 100ccAir, and most preferably 100sec / 100ccAir. From the viewpoint of high output of the battery, it is preferable that the porous membrane (A) has a low permeation resistance within a range not causing problems in processability.

The upper limit of the porosity of the porous film (A) is preferably 70%, more preferably 60%, and most preferably 55%. The lower limit of the porosity is preferably 25%, more preferably 30%, and most preferably 35%.

The permeation resistance and porosity of the porous film (A) are greatly influenced by the ion permeability (charge / discharge operation voltage), the charge / discharge characteristics of the battery, the lifetime of the battery (closely related to the amount of electrolyte retained) When the upper limit of the degree or the lower limit of the porosity is in the above-mentioned preferable range, the function as a battery can be sufficiently exerted. On the other hand, if the lower limit of the durability or the upper limit of the porosity is in the above-mentioned preferable range, sufficient mechanical strength and electrical insulation between the electrodes can be maintained, and short-circuiting does not occur during charging and discharging.

The average pore diameter of the porous film (A) largely affects the shutdown speed, so it is preferably 0.01 to 1.0 占 퐉, more preferably 0.02 to 0.5 占 퐉, and most preferably 0.03 to 0.3 占 퐉.

When the average pore diameter is within this preferable range, the durability of the durability does not significantly deteriorate at the time of forming the film, and the response to the temperature of the shutdown phenomenon is rapid, for example, due to overcharging, external or internal short- The shutdown function effectively functions even when the internal temperature of the battery rises sharply.

The present invention will be described in further detail with reference to the following examples, but the present invention is not limited to these examples.

Example

[Porous film (A)]

Here, the effect of the present invention was confirmed by using "Setela" (registered trademark) E20MMS manufactured by Toray Battery Separator Film Co., Ltd. as the porous film (A).

E20MMS is a porous membrane made of polyethylene, and various physical properties were measured as Comparative Example 1 for comparison with the present invention.

[Coating Treatment Apparatus]

The coating processing apparatus has a film winding shaft, a winding shaft, a cooling drum (150 mm) and a plasma electrode in a container (chamber) capable of being reduced in pressure. A vacuum pump is connected to the coating processing apparatus to reduce the pressure in the chamber.

The film supplied from the unwinding side is transported while being held by the cooling drum opposed to the plasma electrode and wound around the take-up shaft side. Further, the unwinding and winding tension can be appropriately set by adjusting the shaft torque.

The plasma electrode was a flat plate magnetron type and the electrode material was graphite. The effective size of the electrode is 50 mm in the transport direction of the film and 100 mm in the width direction of the film. A 13.56 MHz high frequency power source is connected to the plasma electrode through a matching box.

Further, a liquid raw material vaporizer is connected to the coating apparatus. This is to pressurize the liquid feedstock with argon gas and feed it to the vaporizer while weighing with a digital liquid mass flow controller to produce the feedstock vapor. Further, the raw material vapor is supplied between the cooling drum of the coating apparatus and the plasma electrode. The opposite axis of the cooling drum and the plasma electrode is horizontal, and the shortest distance is 100 mm.

Further, this coating treatment apparatus is also connected to a gas introduction system by a mass flow controller, and for example, an additive gas can be supplied between the cooling drum and the plasma electrode.

In this coating treatment apparatus, a crucible for vaporizing the solid raw material by heating can be provided. By arranging the crucible between the cooling drum and the plasma electrode, the raw material vapor can be supplied from below the oblique side of the cooling drum.

The crucible shape has a square shape with an opening of 50 mm x 50 mm and a height of 40 mm. The material of the crucible is stainless steel SUS306 having a thickness of 1.0 mm. Under the crucible, a copper heater plate having a size of 50 mm x 50 mm x 10 mm is disposed through a carbon sheet for increasing the thermal conductivity.

Heater and thermocouple are embedded in the heater plate, and temperature can be controlled by PID. The heater plate is placed on the chamber base plate through an alumina spacer made of heat insulating material.

The opening of the crucible was covered with an aluminum mesh having a pitch of 1.5 mm so that the surface of the material in the crucible was prevented from being exposed to the plasma when the plasma was generated at the top.

Further, a quartz oscillator film is provided on the side of the cooling drum toward the plasma electrode side, so that the coating process can be monitored.

(Example 1)

Hexamethyldisiloxane (HMDSO; manufactured by Shin-Etsu Chemical Co., Ltd.) was charged into a liquid raw material container, and the mixture was purged with argon gas after vacuum evacuation. On the other hand, a roll wound with a porous film (A) having a thickness of 20 μm, a width of 50 mm and a length of 20 m was set on a coating apparatus, and the inside of the apparatus was evacuated to 3.0 × 10 ^-3 Pa or less.

Thereafter, HMDSO was supplied to the vaporizer at a flow rate of 0.65 cc / min, the vapor was introduced into the coating apparatus, and the exhaust valve was adjusted to set the pressure in the chamber to 1.0 Pa. The setting of the mass flow controller of the gas introducing system was adjusted so that the partial pressure ratio of the additive gas to the HMDSO was the partial pressure ratio shown in Table 1 and added to the chamber.

After setting the pressure, the high frequency power applied to the plasma electrode was set to be 100 W to generate plasma. Further, after the elapse of 5 minutes from the plasma generation, the winding of the film was started. The winding speed was set to 0.1 m / min.

The raw materials and coating conditions in each of the Examples and Comparative Examples are as shown in Table 1 and Table 2.

(Example 2)

Except that the added gas was changed to carbon dioxide, and the pressure in the chamber was set to 5.0 Pa.

(Comparative Example 2)

Except that no additive gas was added and the pressure in the chamber was set to 10.0 Pa.

(Example 3)

Hexamethyldisilazane (HMDS: manufactured by Wako Pure Chemical Industries, Ltd.) was added to the liquid raw material container, and the mixture was purged with argon gas after vacuum evacuation. The pressure in the chamber was set to 5.0 Pa. In addition, the same procedure as in Example 1 was performed.

(Example 4)

Hexamethyldisilazane (HMDS: manufactured by Wako Pure Chemical Industries, Ltd.) was added to the liquid raw material container, and the mixture was purged with argon gas after vacuum evacuation. The other gas was carbon dioxide, and the other steps were carried out in the same manner as in Example 1.

(Comparative Example 3)

Hexamethyldisilazane (HMDS: manufactured by Wako Pure Chemical Industries, Ltd.) was added to the liquid raw material container, and the mixture was purged with argon gas after vacuum evacuation. The same procedure as in Example 1 was carried out except that no additive gas was added.

(Example 5)

Titanium isopropoxide (TTIP, manufactured by Wako Pure Chemical Industries, Ltd.) was charged into a liquid raw material container, and the mixture was purged with argon gas after vacuum evacuation. The procedure of Example 1 was repeated except that the additive gas was changed to carbon dioxide.

(Examples 6 to 9 and Comparative Example 4)

20 g of terephthalic acid monomer powder (manufactured by Wako Pure Chemical Industries, Ltd.) was added to the crucible and uniformly diffused in the crucible. Further, a roll wound with a porous film (A) having a thickness of 20 탆, a width of 50 mm and a length of 20 m was wound around the coating apparatus to start the evacuation.

Thereafter, the heater was heated to 200 캜 and exhausted to 3.0 x 10 ^-3 Pa or less during the evacuation. At this temperature, the monomer was found to be almost evaporated, but the film was confirmed to be a crystal vibrating film.

After stabilizing for about 5 minutes in this state, the heater temperature was set to 400 DEG C to generate material vapor. Incidentally, plasma was applied in the range of 5 Pa to 10 Pa and high frequency power applied to the plasma electrode in the range of 50W to 100W by introducing the additive gas. In any case, the transporting speed of the film was set in the range of 0.1 m / min to 0.4 m / min.

The method of adding the additive gas is the same as in Example 1, and the raw materials and coating conditions in each of the Examples and Comparative Examples are as shown in Tables 1 and 2.

(Examples 10 and 11 and Comparative Example 5)

20 g of a melamine monomer powder (manufactured by Wako Pure Chemical Industries, Ltd.) was added to the crucible and uniformly diffused in the crucible. Further, a roll wound with a porous film (A) having a thickness of 20 탆, a width of 50 mm and a length of 20 m was wound around the coating apparatus to start the evacuation.

After that 3.0 × 10 ^-3 ㎩ in a state of heating by the heater 200 in the exhaust ℃ Or less. At this temperature, the monomer was found to be almost evaporated, but the film was confirmed to be a crystal vibrating film.

After stabilizing in this state for about 5 minutes, the heater temperature was set to 350 DEG C to generate material vapor. Incidentally, plasma was applied in the range of 5 Pa to 10 Pa and high frequency power applied to the plasma electrode in the range of 50W to 100W by introducing the additive gas. In either case, the transporting speed of the film was set at 0.1 m / min to 0.4 m / min.

The method of adding the additive gas is the same as in Example 1, and the raw materials and coating conditions in each of the Examples and Comparative Examples are as shown in Tables 1 and 2.

[result]

The physical properties of the porous films obtained in Examples 1 to 11 and Comparative Examples 1 to 5 were measured by the following methods. The results are shown in Tables 1 and 2.

Film thickness: Measured by a contact thickness meter (manufactured by Mitsutoyo Corporation).

Specular resistance: The Gurley value was measured according to JIS P 8117 (in terms of a film thickness of 20 μm).

Unit weight: The porous membrane was punched to 50 mm x 50 mm to measure the weight of the porous membrane to 0.1 mg. The weight was converted into g / m 2.

Perforation strength: The maximum load when the porous membrane was perforated at a speed of 2 mm / sec using a needle having a diameter of 1 mm (0.5 mm R) was measured and converted into a thickness of 20 탆.

(TD) x 3 mm (MD) sample at a rate of 5 DEG C / min using a shutdown temperature: thermal / stress / strain measuring device (TMA / SS6000, Seiko Denshi Corp.) The temperature was raised from room temperature, and the temperature was pulled up to a load of 2 g. The terminal pole point observed near the melting point was set as the shutdown temperature.

Meltdown temperature: A 10 mm (MD) x 3 mm (TD) porous film sample was heated at a rate of 5 占 폚 / min from room temperature using a tensile / stress / The temperature at which the film was broken by the melt-down temperature.

Flexibility: A blade of a new design cutter was inserted from the coating side of the porous film (A '), and a slit of about 5 mm was placed. The slit portion was observed with an electron microscope at a magnification of 1000 times, and the presence or absence of cracks (cracks or peeling of the coating surface derived from the slits) was observed and qualitative evaluation was made according to the following criteria.

Excellent: No crack

good: There seems to be a crack

failure: there is a big crack

Heat shrinkage (105 ° C × 8h): mark the center of gravity (bisector) of each side of the porous film made 50 × 50 mm in MD and TD directions. The porous film is heat-treated at 105 deg. C for 8 hours in a free state without being fixed, and the dimensions of the MD and TD after the heat treatment are measured at the marked positions.

The heat shrinkage percentage was calculated by subtracting the dimension after heating from the dimension before heating (50 mm) and dividing it by the dimension before heating (50 mm).

Heat shrinkage (150 DEG C x 30 minutes): When the heat shrinkage rate in the TD direction is measured, a porous film having dimensions of 50 x 50 mm in MD and TD directions is formed so as to be parallel to the TD direction in a frame having openings of 50 x 35 mm Fix both ends in the MD direction with tape or the like. Accordingly, the MD direction is fixed at an interval of 35 mm, and the TD direction is positioned in a state in which the film end portions follow the frame opening portions. Together with the frame in which the porous film is fixed, is heat-treated in an oven at 150 占 폚 for 30 minutes and cooled. The end of the porous film parallel to the MD is curved slightly inward (toward the center of the opening of the frame) due to heat shrinkage in the TD direction. The heat shrinkage percentage (%) in the TD direction was calculated by subtracting the shortest dimension in the TD direction after heating from the TD dimension (50 mm) before heating, and dividing by the TD dimension (50 mm) before heating.

In the case of measuring the heat shrinkage ratio in the MD direction, the TD and MD directions are changed in the above method.

· Wettability with electrolytic solution

The wet tensile strength test mixture No. 42.0 (manufactured by Wako Pure Chemical Industries, Ltd.) was applied onto the surface of the porous film (A) kept in a horizontal state and the surface of the porous film (A ' One drop was added dropwise, and the state of dispersion of the droplet on the surface of the porous film after 30 seconds passed after the dropwise addition was observed. When the diffusion of the liquid droplet on the surface of the porous membrane (A ') on which the coating was formed was larger than that of the porous membrane (A)

· Electrochemical stability

A porous film having a size of 70 mm in the MD direction and 60 mm in the TD direction is prepared, and a porous film is sandwiched between negative and positive electrodes of the same size to manufacture a battery. At this time, a 1M solution in which LiPF ₆ was dissolved in a mixture of a natural graphite, a positive electrode and LiCoO ₂ and a mixture of ethylene carbonate and dimethyl carbonate (3/7, v / v) was used. In the case of the porous film (A '), the coated surface was disposed so as to be in contact with the positive electrode, and the porous film was impregnated with an electrolyte to complete the battery.

Subsequently, an applied voltage of 4.3 V was applied to the prepared battery at 60 캜, and the " electrochemical stability " was determined as the magnitude of the integral current flowing between the voltage source and the battery. It is generally preferable that the integrated current indicating that the filling loss during overcharging is small is small.

In the examples, the integrated current value (mAh) up to 120 hours after the application of the voltage is described.

As shown in Table 1 and Table 2, it was found that the porous film (A) of the present invention, having the coating film formed of the raw material selected from the raw material group shown in the group 1 and the additive gas shown in the group 2, have.

(Industrial availability)

According to the present invention, it is possible to provide a porous film having excellent low heat shrinkability, shutdown property, anti-meltdown property, wettability with an electrolytic solution, and electrochemical stability without deteriorating the ion permeability and mechanical properties required for the battery separator , Which can be used as a battery separator.

Claims (12)

A porous film (A) to be treated is placed in a plasma coating treatment apparatus, and at least one kind of raw material selected from the raw material groups (1) to (9) (A ') is obtained by forming a film containing constituent elements of a raw material and an additive gas on at least one surface of the porous film (A) by carrying out a coating treatment while coexisting with an additive gas.
County 1
(1) a silane compound represented by SiR ¹ R ² R ³ R ⁴ (wherein each of R ¹ to R ⁴ is any one of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group, The carbon chain may be saturated or unsaturated. Further, for example, a ring may be formed of Si and substituent groups R ¹ and R ² , and the carbon chain may be saturated or unsaturated. )
(2) a disiloxane compound represented by O- (SiR ¹ R ² R ³ ) ₂ (wherein each of R ¹ to R ³ is any one of hydrogen, halogen, and an alkyl group having 1 to 10 carbon atoms, The carbon chain may be saturated or unsaturated. Further, for example, a ring may be formed of Si and substituent groups R ¹ and R ² , and the carbon chain may be saturated or unsaturated. )
(3) - (OSiR ¹ R ² ) _n - (wherein R ¹ and R ² are each any one of hydrogen, halogen and alkyl groups of 1 to 10 carbon atoms, and the carbon chain may be linear The carbon chain may be saturated or unsaturated. The ring may be formed of, for example, Si and substituents R ¹ and R ² . N is an integer of 2 to 20)
(4) a silazane compound represented by N- (SiR ¹ R ² R ³ ) _m R ⁴ _{3 -m} wherein each of R ¹ to R ⁴ is any one of hydrogen, halogen and an alkyl group having 1 to 10 carbon atoms , the carbon chain is good even if the branch may be straight chained, and may be each the same or the number of carbon atoms is different. in addition, the carbon chain may be a good and unsaturated may be saturated. also, for example, switch to Si as the substituents R ¹ and R ² M may be an integer of 1 to 3)
(5) - (NR ¹ SiR ² R ² ) ₁ - (wherein R ¹ to R ³ are each any one of hydrogen, halogen, and an alkyl group having 1 to 10 carbon atoms, and the carbon chain is The carbon chain may be saturated or unsaturated. Further, even if Si and the substituent groups R ¹ and R ² form a ring, for example, the carbon chain may be saturated or unsaturated. L is an integer of 2 to 20)
(6) a titanate compound represented by TiR ¹ R ² R ³ R ⁴ wherein each of R ¹ to R ⁴ is any one of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group, The carbon chain may be saturated or unsaturated. Further, for example, a ring may be formed of Ti and substituent groups R ¹ and R ² , and the carbon chain may be saturated or unsaturated. )
(7) Aromatic hydrocarbon compound
(8) Ar- (X) an aromatic compound having a polar group represented by the _k least one at least (wherein, Ar represents an aromatic hydrocarbon or heteroaromatic compound with water, -X is -COOH, -SO ₃ H, -OR , and _{-CO-R, -CONHR, -SO 2} NHR, -NHCOOR, -NHCONHR, -NH 2 any one, k is an integer of 1 or more and 3, R is an alkyl group of 1 to 10 carbon atoms, an alkyl group of carbon The chain may be linear or branched, and may have a different carbon number or the same carbon number. The carbon chain may be saturated or unsaturated)
(9) Lactam compound A porous film (A) to be treated is placed in a plasma coating processing apparatus, and at least one kind of raw material selected from a raw material group shown in the following Group 1 is allowed to exist in a gaseous state in the apparatus, (A ') is obtained by forming a coating film containing a constituent element of an additive gas on the surface of the fiber, pulp or fibril forming the porous film (A).
County 1
(1) a silane compound represented by SiR ¹ R ² R ³ R ⁴ (wherein each of R ¹ to R ⁴ is any one of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group, The carbon chain may be saturated or unsaturated. Further, for example, a ring may be formed of Si and substituent groups R ¹ and R ² , and the carbon chain may be saturated or unsaturated. )
(2) a disiloxane compound represented by O- (SiR ¹ R ² R ³ ) ₂ (wherein each of R ¹ to R ³ is any one of hydrogen, halogen, and an alkyl group having 1 to 10 carbon atoms, The carbon chain may be saturated or unsaturated. Further, for example, a ring may be formed of Si and substituent groups R ¹ and R ² , and the carbon chain may be saturated or unsaturated. )
(3) - (OSiR ¹ R ² ) _n - (wherein R ¹ and R ² are each any one of hydrogen, halogen and alkyl groups of 1 to 10 carbon atoms, and the carbon chain may be linear The carbon chain may be saturated or unsaturated. The ring may be formed of, for example, Si and substituents R ¹ and R ² . N is an integer of 2 to 20)
(4) a silazane compound represented by N- (SiR ¹ R ² R ³ ) _m R ⁴ _{3 -m} wherein each of R ¹ to R ⁴ is any one of hydrogen, halogen and an alkyl group having 1 to 10 carbon atoms , the carbon chain is good even if the branch may be straight chained, and may be each the same or the number of carbon atoms is different. in addition, the carbon chain may be a good and unsaturated may be saturated. also, for example, switch to Si as the substituents R ¹ and R ² M may be an integer of 1 to 3)
(5) - (NR ¹ SiR ² R ² ) ₁ - (wherein R ¹ to R ³ are each any one of hydrogen, halogen, and an alkyl group having 1 to 10 carbon atoms, and the carbon chain is The carbon chain may be saturated or unsaturated. Further, even if Si and the substituent groups R ¹ and R ² form a ring, for example, the carbon chain may be saturated or unsaturated. L is an integer of 2 to 20)
(6) a titanate compound represented by TiR ¹ R ² R ³ R ⁴ wherein each of R ¹ to R ⁴ is any one of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group, The carbon chain may be saturated or unsaturated. Further, for example, a ring may be formed of Ti and substituent groups R ¹ and R ² , and the carbon chain may be saturated or unsaturated. )
(7) Aromatic hydrocarbon compound
(8) Ar- (X) an aromatic compound having a polar group represented by the _k least one at least (wherein, Ar represents an aromatic hydrocarbon or heteroaromatic compound with water, -X is -COOH, -SO ₃ H, -OR , and _{-CO-R, -CONHR, -SO 2} NHR, -NHCOOR, -NHCONHR, -NH 2 any one, k is an integer of 1 or more and 3, R is an alkyl group of 1 to 10 carbon atoms, an alkyl group of carbon The chain may be linear or branched, and may have a different carbon number or the same carbon number. The carbon chain may be saturated or unsaturated)
(9) Lactam compound 3. The method according to claim 1 or 2,
A porous film (A ') which is coated with a roll-to-roll process. 4. The method according to any one of claims 1 to 3,
And the additive gas is at least one kind selected from the gases shown in the following group 2.
County 2
Hydrogen, nitrogen, oxygen, carbon dioxide, nitrous oxide, nitrogen dioxide, hydrocarbons having 3 or less carbon atoms 5. The method according to any one of claims 1 to 4,
A porous film (A ') characterized in that the raw material present in a gaseous state at the time of coating treatment is a solid at normal temperature and normal pressure. 5. The method according to any one of claims 1 to 4,
A porous film (A ') characterized in that the raw material present in a gaseous state at the time of coating treatment is a liquid at normal temperature and normal pressure. 7. The method according to any one of claims 1 to 6,
The raw material is at least one kind selected from the group of raw materials represented by groups 1- (2), (4), (6) and (8), and the additive gas is any one of nitrogen, (A '). 8. The method according to any one of claims 1 to 7,
The relationship between the air permeability resistance X (sec / 100ccAir / 20 占 퐉) of the porous film (A) before coating treatment and the air permeability resistance X '(sec / 100ccAir / 20 占 퐉) of the porous film (A' / X < / = 2.0. ≪ / RTI > 9. The method according to any one of claims 1 to 8,
The relationship between the weight W (g / m 2) of the porous film (A) and the weight W '(g / m 2) of the coated porous film (A') satisfies W'-W 2 (g / (A '). 10. The method according to any one of claims 1 to 9,
The porous film (A ') is produced by a wet process. A separator for a battery, characterized by comprising the porous membrane (A ') according to any one of claims 1 to 10. A battery comprising at least one positive electrode, negative electrode, electrolyte, and separator for a battery according to claim 11.