KR20170022977A - Separator for nonaqueous secondary batteries, and nonaqueous secondary battery - Google Patents

Abstract

One embodiment of the present invention is a fluorine-containing fluorine-containing nonionic surfactant comprising a film containing a fluorine-containing nonionic surfactant having a hydrophobic structural unit containing a fluorine atom and a hydrophilic structural unit, wherein the content of the fluorine-containing nonionic surfactant is 0.001 g / M < 2 > and not more than 1 g / m < 2 >.

Description

TECHNICAL FIELD [0001] The present invention relates to a separator for a non-aqueous secondary battery and a non-aqueous secondary battery,

The present disclosure relates to a separator for a non-aqueous secondary battery and a non-aqueous secondary battery.

BACKGROUND ART A non-aqueous secondary battery typified by a lithium ion secondary battery is widely used as a power source for portable electronic devices such as a notebook PC, a mobile phone, a digital camera, and a camcorder. Further, in recent years, such a non-aqueous secondary battery has been studied for application to automobiles and the like because of its high energy density.

The non-aqueous secondary battery generally has a lower output characteristic than an alkaline secondary battery because a non-aqueous electrolyte having a low ionic conductivity is applied. Therefore, conventionally, improvement of the output characteristics is one of the important problems for the non-aqueous secondary battery. As an effective method for improving the output characteristics, there is a method in which the electrode is made thinner to increase the electrode area to lower the current density (see, for example, Japanese Patent Application Laid-Open No. 2006-32246).

On the other hand, in the separator technology, techniques for improving the output characteristics have been studied.

As a technique to be carried out on the side of the separator, a method of making a structure having a high porosity and a large pore diameter has been studied. From this point of view, a form using a nonwoven fabric or paper has been attracting attention (for example, For example, Japanese Patent No. 4970539).

On the other hand, along with miniaturization and weight reduction of portable electronic devices, the exterior of non-aqueous secondary batteries has been simplified. In recent years, a battery can of aluminum can is developed instead of a battery can made of stainless steel originally used as an outer case, and at present, a soft pack outer cover made of aluminum laminate pack has been developed.

In the case of the soft pack enclosure made of the aluminum laminate, since the enclosure is soft, a gap may be formed between the electrode and the separator with charge and discharge. This is a cause of deteriorating the cycle life, and it is an important technical problem to keep the adhesiveness of the bonding portion such as the electrode or the separator uniform.

As techniques relating to adhesiveness, various techniques for increasing the adhesiveness between an electrode and a separator have been proposed. As one of such techniques, there has been proposed a technique of using a separator in which a porous layer using a polyvinylidene fluoride resin (hereinafter also referred to as an " adhesive porous layer ") is molded into a polyolefin microporous membrane, which is a conventional separator See, for example, Japanese Patent No. 4,127,989). The adhesive porous layer also functions as an adhesive for satisfactorily bonding the electrode and the separator when the electrode is overlaid on the electrode by compression bonding or thermocompression bonding. For this reason, the adhesive porous layer contributes to improvement in the life cycle of the soft pack battery cycle.

The technique of applying such a separator is an effective technique from the viewpoint of adhesion to an electrode, but the polyvinylidene fluoride resin generally has characteristics that are easy to charge, and the handling property may be impaired. As a technique for improving the handling property, for example, a technique of coating a surfactant has been proposed (see, for example, Japanese Patent Application Laid-Open No. 2006-73221).

However, as described above, the method of increasing the electrode area by thinning the electrode increases the production cost of the battery. Therefore, it is a factor that hinders its application to applications requiring high output characteristics.

Further, in the case of using a nonwoven fabric or the like, it is difficult to secure a function of preventing an electrical short between the positive electrode and the negative electrode, which are the original roles of the separator, with an adequate film thickness, and insufficient resistance to dendrites, It is difficult to say that this is a practical method.

Further, the surfactant itself is a well-known material, but the addition of the surfactant causes moisture to be mixed into the inside of the battery, so that the use thereof has been avoided in the past. Therefore, the influence on the battery performance such as output by containing a surfactant has not been clarified up to this point.

As the surfactant, for example, a non-fluorine-based nonionic surfactant having an alkyl chain as a hydrophobic portion and an ionic surfactant containing a salt have been conventionally known, but according to the investigations of the present inventors, It has been recognized that the surfactant of this species may cause a reduction in the output of the battery.

As described above, in the soft pack battery provided with the adhesive porous layer, since the electrode and the separator are bonded to each other via the adhesive porous layer, the cycle life is improved. However, the adhesive porous layer itself increases the electrical resistance . As a result, the trade-off relationship that the output characteristics of the battery is sacrificed is also a problem.

The present disclosure has been made in view of the above, and has as its object to achieve the following objects.

An object of the present invention is to provide a separator for a non-aqueous secondary battery which reduces the internal resistance of the battery and improves the output characteristics. Another embodiment of the present invention is to provide a separator for a non-aqueous secondary battery, which contains a polyvinylidene fluoride resin but is prevented from being charged and reduces the internal resistance of the battery.

It is still another object of the present invention to provide a non-aqueous secondary battery having excellent output characteristics.

Specific means for solving the above-mentioned problems include the following embodiments.

According to an embodiment of the present invention,

A fluorine-containing nonionic surfactant comprising a fluorine-containing nonionic surfactant having a fluorine atom-containing hydrophobic structural unit and a hydrophilic structural unit, wherein the content of the fluorine-containing nonionic surfactant is 0.001 g / m 2 or more and 1 g / And is a separator for a water-based secondary battery.

According to another aspect of the present invention,

(2) A polyvinylidene fluoride resin which is disposed on at least a part of at least one surface, and a fluorine-containing nonionic surfactant having a hydrophilic structural unit at one end and a hydrophobic structural unit containing a fluorine atom at the other end Based secondary battery.

According to one embodiment or another embodiment of the present invention, the following aspects are preferable.

<3> The non-aqueous secondary battery separator according to <2>, wherein the surface layer forming the surface has a layer containing the polyvinylidene fluoride resin and the fluorine-containing nonionic surfactant on one surface or both surfaces.

(4) A method for producing a porous substrate, comprising the steps of: providing a porous substrate (base material) and a layer provided on the one surface or both surfaces of the porous substrate as a surface layer for forming the surface and containing the polyvinylidene fluoride resin and the fluorine-containing nonionic surface active agent Is a separator for a non-aqueous secondary battery according to < 2 > or < 3 >.

<5> The separator for a non-aqueous secondary battery according to <4>, wherein the porous substrate is a polyethylene microporous membrane.

<6> The layer comprising the polyvinylidene fluoride resin and the fluorine-containing nonionic surfactant is a separator for a nonaqueous secondary battery according to any one of <3> to <5>, which is a porous layer.

<7> The separator for a nonaqueous secondary battery according to any one of <1> to <6>, wherein the hydrophobic structural unit has a fluoroalkyl group or a fluoroalkenyl group.

<8> The separator for a nonaqueous secondary battery according to any one of <1> to <7>, wherein the separator has an alkylene oxide chain as the hydrophilic structural unit.

<9> The separator for a non-aqueous secondary battery according to <8>, wherein the alkylene oxide chain is an ethylene oxide chain.

<10> The separator for a non-aqueous secondary battery according to <8> or <9>, wherein the average addition mole number of the alkylene oxide chain is 5 mol or more and 25 mol or less.

<11> The fluorine-containing nonionic surfactant is at least one selected from the group consisting of perfluoroalkylalkylene oxide adducts and perfluoroalkenyl alkylene oxide adducts, Is a separator for a non-aqueous secondary battery.

According to another embodiment of the present invention,

<12> A nonaqueous secondary battery separator according to any one of <1> to <11>, wherein the separator is disposed between the positive electrode and the negative electrode and includes an anode, a cathode, Based secondary battery.

According to one embodiment of the present invention, there is provided a separator for a non-aqueous secondary battery, which improves the output characteristics by reducing the internal resistance of the battery. Further, according to another embodiment of the present invention, it is possible to provide a separator for a non-aqueous secondary battery which contains a polyvinylidene fluoride resin but is prevented from being charged and reduces the internal resistance of the battery.

Further, according to the embodiment of the present invention, a non-aqueous secondary battery having excellent output characteristics is provided.

Hereinafter, a separator for a non-aqueous secondary battery according to an embodiment of the present invention and a non-aqueous secondary battery having the same will be described in detail.

A separator for a nonaqueous secondary battery according to an embodiment of the present invention comprises a film containing a fluorine-containing nonionic surfactant having a fluorine atom-containing hydrophobic structural unit and a hydrophilic structural unit, wherein the fluorine-containing nonionic surfactant Is in the range of 0.001 g / m &lt; 2 &gt; to 1 g / m &lt; 2 &gt;. The film may further contain other components such as a functional resin or a filler if necessary.

As one of preferred embodiments, a separator for a non-aqueous secondary battery according to another embodiment of the present invention comprises a polyvinylidene fluoride resin disposed on at least a part of at least one surface of the polyvinylidene fluoride resin, And the other is a fluorine-containing nonionic surfactant which is a hydrophobic structural unit containing a fluorine atom. The separator for a non-aqueous secondary battery according to another embodiment of the present invention may further contain other components such as a resin other than a polyvinylidene fluoride resin and a filler, if necessary.

Surfactants are well-known materials in the past, but their use as battery materials has generally been avoided from the viewpoint of preventing moisture from entering into the cells. It has also been found that, for example, a non-fluorine-based nonionic surfactant having an alkyl chain as a hydrophobic portion and an ionic surfactant containing a salt tend to increase the internal resistance of the battery. Therefore, there is a possibility that the surfactant of this species may cause the battery output to be lowered rather.

In the separator of the present disclosure, by containing a specific fluorine-containing nonionic surfactant having a hydrophobic structural unit and a hydrophobic structural unit containing a fluorine atom in the molecule, it is possible to provide a separator which does not necessarily achieve high air- The effect of remarkably lowering the internal resistance of the battery as compared with the separator using the surfactant or the ionic surfactant is exhibited and the output characteristic of the battery is improved.

Further, since it is not necessary to set the separator to have a high porosity or a large diameter, the penetration rate of the electrolytic solution is promoted rather than the yield of the battery is reduced, and penetration with high uniformity becomes possible. This makes it possible to improve the productivity and yield of the battery.

It is effective to use a polyvinylidene fluoride resin as a resin component in the case of a separator that can be bonded to an electrode, has high adhesion to an electrode, and is excellent in cycle life. However, the polyvinylidene fluoride resin tends to generate electrification as compared with other resins, and the handling property tends to be impaired. On the other hand, the surfactant can be used for the purpose of preventing electrification. However, for example, a nonionic surfactant such as an alkyl chain constituting a hydrophobic portion tends to increase the internal resistance of the battery, There is a concern.

In the present invention, as described above, the polyvinylidene fluoride resin, which is a resin component constituting the separator, is mixed with a specific fluorine-containing nonionic surfactant having a hydrophilic structural unit and a fluorine atom- It is a preferred embodiment (another embodiment described above) to contain together. As a result, the internal resistance of the battery is effectively lowered as compared with the case where the nonionic surfactant other than the specific fluorine-containing nonionic surfactant is used, and the output characteristics An effect of being excellent can be obtained.

~ Membrane structure of separator ~

The separator for a non-aqueous secondary battery (hereinafter, simply referred to as "separator") which is an embodiment of the present invention is not particularly limited as long as it is constituted as a film containing a specific fluorine-containing nonionic surfactant described later, Or a multilayer film, and may be either a porous film or a non-porous film. It is preferable that the separator, which is one embodiment of the present invention, is a single layer film or a multilayer film which is a porous film from the viewpoint of ion permeability.

The film structure of the separator according to one embodiment of the present invention may be any of the following embodiments and a fluorine-containing nonionic surfactant may be added to the separator to form a separator for a nonaqueous secondary battery according to an embodiment of the present invention have.

(1) A microporous membrane made of polyolefin

For example, a single layer polyolefin microporous membrane containing polyolefin and a single layer polyolefin microporous membrane may be laminated.

(2) Single layer film of functional resin

For example, a single-layer film made of a functional resin such as a heat-resistant resin or an adhesive resin, or a single-layer film made of a mixture of a functional resin and a filler can be given.

(3) Composite membrane

For example, there can be mentioned a composite membrane in which a functional resin is provided on the inside and on the surface of a fibrous sheet such as a nonwoven fabric or paper, and a filler may be carried on the composite membrane.

(4)

For example, a laminated film having a porous substrate and a layer (preferably a porous layer) comprising a functional resin such as a heat resistant resin or an adhesive resin laminated on one surface or both surfaces of the porous substrate can be exemplified. May further include a filler.

- Fluorine-containing nonionic surfactant -

The separator for a non-aqueous secondary battery according to one embodiment of the present invention contains at least one of a fluorine-containing nonionic surfactant having a fluorine atom-containing hydrophobic structural unit and a hydrophilic structural unit.

Conventionally various surfactants have been known, but among the surfactants, nonionic surfactants having alkyl groups as the hydrophobic structural units, fluorine surfactants having fluorine atoms in the hydrophobic structural units, anionic surfactants such as sulfonates, quaternary ammonium salts Have not only an effect of suppressing the internal resistance of the battery to a low level but also increase the internal resistance of the battery in some cases. In the present disclosure, by using a nonionic fluorine-containing surfactant having a hydrophobic structural unit and a hydrophobic structural unit including a fluorine atom in the separator, it is possible to reduce the internal resistance of the battery.

For this reason, it is presumed that the fluorine-containing nonionic surfactant attached to the separator elutes into the electrolytic solution and acts on the electrode, thereby reducing the reaction resistance. Further, by attaching the surfactant to the separator, an effect of accelerating the penetration rate of the electrolytic solution into the separator and uniformly penetrating the electrolytic solution is expected, contributing to the improvement of productivity of the battery. In addition, antistatic property and slippery property can be improved, and as a result, handling property is also improved, which contributes to improvement of battery yield.

The fluorine-containing nonionic surfactant in the present disclosure is preferably a fluorine-containing nonionic surfactant having a hydrophobic structural unit at one end of the compound structure and a hydrophobic structural unit containing a fluorine atom at the other end, Fluorine-containing surfactants are preferable.

The fluorine-containing nonionic surfactant in the present disclosure preferably has an alkylene oxide chain as a hydrophilic structural unit on one side of the terminal. Examples of the alkylene oxide chain include an ethylene oxide chain and a propylene oxide chain. Of these, an ethylene oxide chain is preferable in that an antistatic effect is exhibited while suppressing the moisture content in the battery.

The average addition mole number of the alkylene oxide chain in one molecule is preferably not too much from the viewpoint of obtaining a desired antistatic effect while suppressing the moisture content in the battery and is preferably in the range of 5 to 25 moles Do. Since the average addition mole number of the alkylene oxide chain is within the above range, the antistatic effect of the separator is more excellent. The average addition mole number of the alkylene oxide chain is preferably in the range of 5 to 14 moles, and more preferably in the range of 5 to 10 moles, for the same reason as described above.

The fluorine-containing nonionic surfactant in the present disclosure preferably has a fluoroalkyl group or a fluoroalkenyl group as a hydrophobic structural unit on the other side of the terminal.

The fluoroalkyl group is preferably a fluoroalkyl group having 1 to 18 carbon atoms, and examples thereof include fluoromethyl, fluoroethyl, fluoropropyl, fluorobutyl and the like. Among them, a perfluoroalkyl group is more preferable, and specific examples thereof include perfluoromethyl, perfluoroethyl, perfluoropropyl, and perfluorobutyl.

The fluoroalkenyl group is preferably a fluoroalkenyl group having 1 to 12 carbon atoms, and examples thereof include fluoroethylenyl (vinyl fluoride), fluoro-1-propenyl, fluoroallyl, fluoroisopropenyl, Fluoro-1-butenyl, fluoroisobutenyl, and the like. Among them, a perfluoroalkenyl group is more preferable, and specific examples thereof include perfluoroethylenyl, perfluoro-1-propenyl, perfluoroallyl, perfluoroisopropenyl, perfluoro- Decyl, decyl, perfluoroisobutenyl, and the like.

The hydrophobic structural unit at the end of the fluorine-containing nonionic surfactant preferably has an unsaturated double bond in view of prevention of electrification and improvement of the output characteristics of the battery, and more preferably a fluoroalkenyl group.

Further, the prime number structural unit may be either a linear or branched structure, and it is more preferable to have a branched structure from the viewpoint of preventing electrification and improving output characteristics of a battery.

Examples of the fluorine-containing nonionic surfactant in the present disclosure include fluoroalkylethylene oxide adduct, fluoroalkenyl ethylene oxide adduct, fluoroalkylpropylene oxide adduct, fluoroalkenyl propylene oxide adduct, A perfluoroalkyl ethylene oxide adduct, a perfluoroalkenyl ethylene oxide adduct, and the like.

Among the fluorine-containing nonionic surfactants, a fluoroalkyl alkylene oxide adduct having an alkylene oxide chain on one end and a fluoroalkyl group on the other end, an alkylene oxide chain on one end and a fluoroalkyl A perfluoroalkyl alkylene oxide adduct having a perfluoroalkyl group on one end and an alkylene oxide chain on the other end and a perfluoroalkyl group on the other end, A perfluoroalkenyl alkylene oxide adduct having an alkylene oxide chain and a perfluoroalkenyl group on the other side is preferable.

Particularly preferred is a perfluoroalkenyl ethylene oxide adduct having an ethylene oxide chain on one end and a perfluoroalkenyl group on the other end.

Specific examples of the fluorine-containing nonionic surfactant include SURFON S-242, S-243, S-420 (above, AGC SEIMI CHEMICALSHEET; Fractional structural unit = perfluoroalkyl group), Megafac F-444 4430, FC-4432 (manufactured by Sumitomo 3M Limited; minority structural unit = perfluoroalkyl group), and Futagent (manufactured by DIC Corporation; minor structural unit = perfluoroalkyl group) 251, copper 212M, copper 215M, copper 250, copper 222F, copper 245F, copper 208G, copper 240G, copper 228P, copper FTX-218 (manufactured by Neos; minority structural unit = perfluoroalkenyl group) .

The content of the fluorine-containing nonionic surfactant in the separator is in the range of 0.001 g / m 2 to 1 g / m 2. When the content of the fluorine-containing nonionic surfactant is less than 0.001 g / m 2, it is difficult to obtain the effect of reducing the internal resistance, which is an effect of the embodiment of the present invention. When the content of the fluorine-containing nonionic surfactant is more than 1 g / m 2, the water content of the separator is increased, which may deteriorate the durability and reliability of the battery.

The content of the fluorine-containing nonionic surfactant in the separator is preferably in the range of 0.01 g / m 2 to 1 g / m 2, and more preferably in the range of 0.1 g / m 2 to 1 g / m 2 And more preferably in the range of 0.1 g / m 2 or more and 0.5 g / m 2 or less.

The content of the fluorine-containing nonionic surfactant in the separator means the total amount of the amount contained in the separator and the amount adhered to the surface of the separator.

The content of the fluorine-containing nonionic surfactant in the separator was determined by ¹ H-NMR, which was determined by NMR, using dimethylsulfoxide (DMSO) as a separator, immersing the separator in DMSO to extract a soluble component, ^It is calculated from the result of ¹⁹ F-NMR.

The method for incorporating the fluorine-containing nonionic surfactant into the separator for a nonaqueous secondary battery which is an embodiment of the present invention is not particularly limited, and examples include the following methods.

A method in which a solution prepared by dissolving a fluorine-containing nonionic surfactant in an appropriate solvent is prepared, a separator is treated using this solution, and the solvent is removed by drying or the like. In this method, it is necessary to select a solvent which can be removed by drying or the like. Examples of the solvent include low boiling point organic solvents such as methanol and ethanol, and water. The concentration of the fluorine-containing nonionic surfactant in the solution and the treatment conditions (such as the time and temperature for the treatment) may be adjusted so as to exhibit desired properties, and there is no particular limitation.

The treatment of the separator using the solution can be performed by a method such as coating or spraying the solution on the separator, or immersing the separator in the solution.

The water content of the separator for a non-aqueous secondary battery is preferably suppressed to a low level. Concretely, the water content is preferably 500 ppm or less, more preferably 300 ppm or less, and further preferably 100 ppm or less. The water content is a value measured by a Karl Fischer moisture meter.

The content of the fluorine-containing nonionic surfactant is important from the viewpoint of obtaining a separator having a low water content, but also the hydrophilic structural unit of the fluorine-containing nonionic surfactant becomes important. That is, it is important to select the kind or the existence ratio of the hydrophilic structural unit by a desired method. For example, when the hydrophilic structural unit is an alkylene oxide chain (for example, ethylene oxide chain), the addition mole number of the alkylene oxide chain is an indicator thereof. Specifically, from the viewpoint of suppressing the water content of the separator, the average addition mole number of the alkylene oxide chain (for example, ethylene oxide chain) is preferably 5 moles or more and 14 moles or less.

The separator for a nonaqueous secondary battery according to one embodiment of the present invention may be composed of any of the above membrane structures. For example, the separator for a nonaqueous secondary battery may be composed of a microporous membrane containing a fluorine-containing nonionic surfactant in the membrane or attached to the surface of the membrane Or may be composed of a laminated film having a layer containing a functional resin and a fluorine-containing nonionic surfactant.

When the separator, which is one embodiment of the present invention, is constituted as a laminated film, it is preferable that the porous substrate, the functional substrate such as a heat resistant resin or an adhesive resin, A porous layer containing an activator may be provided.

[Porous layer]

The porous layer has a plurality of micropores therein and has a structure in which these micropores are connected to each other, so that gas or liquid can pass from one surface to the other surface. The porous layer may be composed of a functional resin and may be constituted as an adhesive porous layer to which adhesiveness is imparted.

When the separator according to the embodiment of the present invention has a porous layer, it is preferable that the porous layer has adhesiveness to an object such as an electrode. On the basis of the constitutional view that the porous layer is provided as a surface layer (outermost layer) of the separator on one side or both sides of the porous substrate, the porous layer is a layer capable of bonding with the electrode when the separator and the electrode are superimposed, .

Compared with the case where the porous layer is provided only on one side of the porous substrate, the case having both sides of the porous substrate is preferable in that the cycle characteristics of the battery are excellent. When the porous layer is provided on both surfaces of the porous substrate, both surfaces of the separator can be well bonded to both electrodes via the porous layer.

Although the porous layer having adhesive property includes an adhesive resin, the coating amount of the adhesive resin contained in the porous layer is preferably 0.5 g / m &lt; 2 &gt; More preferably 1.5 g / m 2, and still more preferably 0.75 g / m 2 to 1.25 g / m 2.

When the porous layer is provided on both surfaces of the porous substrate, the coating amount of the porous layer is preferably 1.0 g / m 2 to 3.0 g / m 2 as a total of both surfaces, more preferably 1.5 g / m 2 to 2.5 g / Do.

If the coating amount of the porous layer is 1.0 g / m 2 or more (0.5 g / m 2 in the case of one side), the adhesion with the electrode becomes better and the cycle characteristics in the case of a battery are more excellent. When the coating amount of the porous layer is 3.0 g / m 2 (or 1.5 g / m 2 in the case of one side), the ion permeability is better and the load characteristic of the battery is excellent.

When the porous layer is provided on both surfaces of the porous substrate, the difference between the coating amount of one surface and the coating amount of the other surface is preferably 20% or less with respect to the total coating amount of both surfaces. If the difference is 20% or less, the separator is difficult to curl, and as a result, the handling property is further improved, and the cycle characteristics are hardly deteriorated.

The average thickness of the porous layer is preferably 0.5 mu m to 4 mu m, more preferably 1 mu m to 3 mu m, and most preferably 1 mu m to 3 mu m, from the viewpoint of ensuring adhesion with the electrode and ensuring high energy density. Mu] m to 2 [mu] m.

If the average thickness is 0.5 占 퐉 or more, adhesion with the electrode is good and excellent in cycle characteristics in the case of a battery. Further, if the average thickness is 4 탆 or less, the ion permeability is further improved and excellent due to the load characteristics of the battery, and the coefficient of thermal expansion in the width direction of the separator can be controlled within a range of more than 0% to 10% .

The average thickness is a value obtained by measuring arbitrary 20 points within 10 cm x 10 cm and arithmetically averaging the measured values.

The porosity of the porous layer is preferably 30% to 80%, more preferably 30% to 60%. When the porosity is 30% or more, the ion permeability is more excellent. When the porosity is 80% or less, the mechanical strength to withstand the thermal press when bonding to the electrode can be secured, the surface opening ratio is not excessively increased, and it is suitable for securing the adhesive force.

The porosity is a value obtained from the following formula.

   ? = {1-Ws / (ds? t)} 100

 (%), Ws: basis weight (g / m2), ds: true density (g / cm3), and t: film thickness (占 퐉).

The average pore diameter of the porous layer is preferably 10 nm to 200 nm. When the average pore size is 200 nm or less, non-uniformity of pores is suppressed, the bonding points are dispersed evenly, and the adhesiveness is good. When the average pore diameter is 200 nm or less, the ion movement is uniform, and the cycle characteristics and the load characteristics are good. On the other hand, when the average pore diameter is 10 nm or more, it is difficult to cause the resin constituting the porous layer to swell and block the pores when the porous layer is impregnated with the electrolyte solution.

The average pore diameter (diameter, unit: nm) of the porous layer is determined by using the void volume S of the porous layer calculated from the void ratio and the void surface area S of the porous layer made of the PVDF resin calculated from the nitrogen gas adsorption amount , And assuming that all holes are circumferential, the following formula is obtained.

   d = 4 V / S

 In the formula, d represents the average pore diameter (nm) of the porous layer, V represents the void volume per square meter of the porous layer, and S represents the void surface area per square meter of the porous layer.

Further, the pore area S of the porous layer is obtained as follows.

The specific surface area (m 2 / g) of the porous substrate and the specific surface area (m 2 / g) of the composite membrane obtained by laminating the porous substrate and the porous layer are measured by applying the BET equation in the nitrogen gas adsorption method. Each specific surface area is multiplied by each basis weight (g / m 2) to calculate the public surface area per 1 m 2 of each. Subsequently, the public surface area per square meter of the porous substrate is subtracted from the public surface area per square meter of the separator to calculate the public surface area S per 1 square meter of the porous layer.

As the functional resin constituting the porous layer, a heat-resistant resin and an adhesive resin can be used. The functional resin may contain only one kind or two or more kinds.

The heat-resistant resin includes a resin having a melting point of 200 占 폚 or higher and a resin having substantially no melting point and a thermal decomposition temperature of 200 占 폚 or higher, in addition to a resin having a melting point of 200 占 폚 or higher.

Specific examples of the heat resistant resin include a thermoplastic resin such as a wholly aromatic polyamide, a fluorine resin, polyimide, polyamideimide, polysulfone, polyketone, polyether ketone, polyether sulfone, polyether imide, cellulose, . Among them, a wholly aromatic polyamide is preferable from the viewpoints of easiness of forming a porous structure, bonding property with a filler when an inorganic filler is used, strength of a porous film accompanied thereby and durability such as oxidation resistance. Also in the case of the wholly aromatic polyamide, the meta-type wholly aromatic polyamide is preferable, and the poly (meta-phenylene isophthalamide) is particularly preferable in view of ease of molding when the para-form and meta form are compared.

When the porous layer is provided with an adhesive property, it is preferable that the functional resin contains an adhesive resin having adhesiveness to an adherend such as an electrode. The adhesiveness of the adhesive resin means that the separator is capable of forming a state in which the electrode surface and the separator surface are in contact with each other and do not fall off when the separator is subjected to compression bonding or thermocompression bonding by overlapping the electrodes It says.

Specific examples of the adhesive resin include homopolymers or copolymers of vinylnitriles such as polyvinylidene fluoride, polyvinylidene fluoride copolymer, styrene-butadiene copolymer, acrylonitrile and methacrylonitrile, polyethylene oxide, polypropylene And polyethers such as oxides.

As the adhesive resin contained in the porous layer, a polyvinylidene fluoride resin is preferable from the viewpoint of better adhesion with an electrode.

Examples of the polyvinylidene fluoride resin include a homopolymer of vinylidene fluoride (that is, polyvinylidene fluoride) and a copolymer of vinylidene fluoride and another copolymerizable monomer (that is, polyvinylidene fluoride copolymer).

As the polyvinylidene fluoride resin, a mixture of polyvinylidene fluoride and polyvinylidene fluoride copolymer may be used.

Examples of the monomer copolymerizable with vinylidene fluoride include tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, trichlorethylene, vinyl fluoride and the like, and one or more of them can be used .

The polyvinylidene fluoride resin is obtained by emulsion polymerization or suspension polymerization.

When a polyvinylidene fluoride copolymer is used as the polyvinylidene fluoride resin, a vinylidene fluoride-hexafluoropropylene copolymer is preferable from the viewpoint of adhesion with an electrode. By copolymerizing hexafluoropropylene with vinylidene fluoride, the crystallinity and heat resistance of the resin can be controlled within an appropriate range. As a result, it is possible to suppress the flow of the porous layer during the bonding treatment with the electrode.

The polyvinylidene fluoride resin preferably has a weight average molecular weight in the range of 300,000 to 3,000,000. If the weight average molecular weight is 300,000 or more, the mechanical properties that the porous layer can withstand the bonding treatment with the electrode can be secured, and sufficient adhesion can be obtained. On the other hand, if the weight-average molecular weight is 3,000,000 or less, the viscosity at the time of molding is not excessively increased, and moldability and crystal formation are good, and the polycarbonate is good.

The weight average molecular weight (Mw) of the polyvinylidene fluoride resin is a molecular weight as measured by gel permeation chromatography (hereinafter also referred to as GPC) under the following conditions in terms of polystyrene.

 <Condition>

GPC: GPC-900 (Nippon Bunko)

Column: TSKgel Super AWM-H x 2 (Tosoh Co.)

· Mobile compatibilizer: Dimethylformamide (DMF)

Standard sample: Monodisperse polystyrene (manufactured by TOSOH CORPORATION)

Column temperature: 140 ° C

· Flow rate: 10 ml / min

-filler-

The porous layer may contain a filler. By including the filler, the slidability and the heat resistance of the separator can be improved.

As the filler, a filler and other components made of an inorganic material or an organic material may be contained. Examples of the inorganic filler include metal oxides such as alumina, metal hydroxides such as magnesium hydroxide, and the like. As the organic filler, for example, acrylic resin and the like can be mentioned.

[Porous substrate]

A porous substrate means a substrate having voids or pores therein. As such a substrate, a microporous membrane; A porous sheet made of a fibrous material such as a nonwoven fabric or a paper sheet; A composite porous sheet in which one or more other porous layers are laminated on these microporous membranes or porous sheets; And the like.

The microporous membrane means a membrane having a plurality of micropores therein and a structure in which these micropores are connected to each other so that gas or liquid can pass from one surface to the other surface.

The material constituting the porous substrate may be either an organic material or an inorganic material as long as it is a material having electrical insulation.

The material constituting the porous substrate is preferably a thermoplastic resin from the viewpoint of imparting a shutdown function to the porous substrate. Here, the shutdown function refers to a function of preventing the thermal runaway of the battery by shutting off the movement of the ions by dissolving the constituent material and closing the pores of the porous substrate when the battery temperature becomes high. As the thermoplastic resin, a thermoplastic resin having a melting point of less than 200 占 폚 is suitable, and polyolefin is particularly preferable.

As the porous substrate, a microporous membrane containing a polyolefin (referred to as &quot; polyolefin microporous membrane &quot; in this specification) is preferable.

As the polyolefin microporous membrane, those having sufficient mechanical properties and ion permeability may be selected from among the polyolefin microporous membranes applied to the conventional separator for a non-aqueous secondary battery.

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

The polyolefin microporous membrane is preferably a polyolefin microporous membrane containing polyethylene and polypropylene from the viewpoint of imparting heat resistance to such an extent that it is not easily broken when exposed to high temperatures. Examples of such a polyolefin microporous membrane include microporous membranes in which polyethylene and polypropylene are mixed in one layer. In such a microporous membrane, it is preferable to include 95 mass% or more of polyethylene and 5 mass% or less of polypropylene from the viewpoint of compatibility between the shutdown function and heat resistance. From the viewpoint of compatibility between the shutdown function and heat resistance, the polyolefin microporous membrane having a laminated structure of two or more layers, at least one layer containing polyethylene, and at least one layer containing polypropylene desirable.

The polyolefin contained in the polyolefin microporous membrane has a weight average molecular weight of 100,000 to 5,000,000. When the weight average molecular weight is 100,000 or more, sufficient mechanical properties can be secured. On the other hand, if the weight-average molecular weight is 5,000,000 or less, shutdown characteristics are good and film formation is easy.

The polyolefin microporous membrane can be produced, for example, by the following method. That is, the molten polyolefin resin is extruded from a T-die into a sheet, crystallized, stretched, and further heat-treated to form a microporous membrane. Alternatively, a polyolefin resin melted together with a plasticizer such as liquid paraffin is extruded from a T-die, cooled to form a sheet, stretched, extracted with a plasticizer, and heat treated to form a microporous membrane.

Examples of the porous sheet made of fibrous material include polyesters such as polyethylene terephthalate; Polyolefins such as polyethylene and polypropylene; Heat-resistant resins such as aromatic polyamide, polyimide, polyethersulfone, polysulfone, polyether ketone, and polyether imide; Nonwoven fabric made of fibrous material such as polyolefin, and porous sheet such as paper.

The heat-resistant resin means a polymer having a melting point of 200 ° C or higher, or a polymer having no melting point and having a decomposition temperature of 200 ° C or higher.

As the composite porous sheet, a structure in which a functional layer is laminated on a porous sheet made of a microporous membrane or a fibrous material can be adopted. Such a composite porous sheet is preferable in that functional layers can be further added by the functional layer. As the functional layer, for example, from the viewpoint of imparting heat resistance, a porous layer made of a heat-resistant resin, or a porous layer made of a heat-resistant resin and an inorganic filler can be employed. Examples of the heat-resistant resin include one or two or more heat-resistant resins selected from aromatic polyamide, polyimide, polyether sulfone, polysulfone, polyether ketone and polyetherimide. As the inorganic filler, metal oxides such as alumina; Metal hydroxides such as magnesium hydroxide; And the like. Examples of the composite method include a method of coating a functional layer on a microporous membrane or a porous sheet, a method of bonding a microporous membrane, a porous sheet and a functional layer with an adhesive, a method of thermocompression bonding a microporous membrane or a porous sheet and a functional layer, have.

The thickness of the porous substrate is preferably 5 탆 to 25 탆 from the viewpoint of obtaining good mechanical properties and internal resistance.

The gel value (JIS P8117 (2009)) of the porous substrate is preferably 50 seconds / 100 cc to 800 seconds / 100 cc from the viewpoint of preventing short circuit of the battery and obtaining ion permeability.

The porosity of the porous substrate is preferably 20% to 60% from the viewpoint of obtaining an appropriate film resistance or a shutdown function.

The piercing strength of the porous substrate is preferably 300 g or more from the viewpoint of improving the production yield.

The surface of the porous substrate may be subjected to a corona treatment, a plasma treatment, a flame treatment, an ultraviolet ray irradiation treatment or the like for the purpose of improving the wettability with the coating liquid for forming the porous layer.

~ Physical Properties of Separator for Non-aqueous Secondary Battery ~

The separator for a non-aqueous secondary battery according to one embodiment of the present invention preferably has a total thickness of 5 to 35 mu m from the viewpoints of the mechanical strength and the energy density when the battery is used.

The porosity of the separator for a non-aqueous secondary battery according to one embodiment of the present invention is preferably in the range of 30% or more and 60% or less from the viewpoints of the effect of the embodiment of the present invention and the mechanical strength, handling property and ion permeability Do.

The JIS value (JIS P8117) of the separator for a non-aqueous secondary battery according to one embodiment of the present invention is preferably in the range of 50 sec / 100 cc to 800 sec / 100 cc from the viewpoint of good balance between mechanical strength and membrane resistance.

It is preferable that the separator for a non-aqueous secondary battery which is one embodiment has a multi-pillar structure from the viewpoint of ion permeability. Specifically, the value obtained by subtracting the Gurley value of the porous substrate from the Gurley value of the separator for a non-aqueous secondary battery in which the porous layer is formed is preferably 300 seconds / 100 cc or less, more preferably 150 seconds / 100 cc or less And more preferably 100 sec / 100cc or less. When this value is 300 sec / 100 cc or less, the porous layer is not too dense and the ion permeability is maintained well, and excellent battery characteristics are obtained.

The membrane resistance of the separator for a non-aqueous secondary battery according to one embodiment of the present invention is preferably 1 ohm · cm 2 to 10 ohm · cm 2 from the viewpoint of load characteristics of the battery. Here, the membrane resistance is a resistance value when the separator is impregnated with an electrolytic solution, and is measured by an alternating current method. The value of the membrane resistance varies depending on the type and temperature of the electrolyte. However, the above values are obtained by using a mixed solvent of 1 M LiBF ₄ -propylene carbonate / ethylene carbonate (= 1/1; mass ratio) to be.

The curvature ratio of the separator for a non-aqueous secondary battery which is one embodiment of the present invention is preferably 1.5 to 2.5 from the viewpoint of ion permeability.

~ Manufacturing Method of Separator for Non-aqueous Secondary Battery ~

A separator for a non-aqueous secondary battery, which is an embodiment of the present invention, is produced, for example, by the following method.

In the case where the separator is a single-layer film, as a first method, a solution of a specific fluorine-containing nonionic surfactant of the description (described above) is applied to a microporous membrane made of polyolefin, which is an example of a porous layer, and a fluorine-containing nonionic surfactant . As a second method, a coating solution containing a functional resin (and, if necessary, a filler or the like) is coated on the release sheet to form a coating film, the resin of the coating film is solidified, Or a specific fluorine-containing nonionic surfactant of the fluorine-containing nonionic surfactant to the fluorine-containing nonionic surface-active agent, followed by peeling from the release sheet.

In the first and second methods, the application of the dissolution liquid can be carried out by a coating method, a dipping method, a spraying method, or the like.

When the separator is a laminated film, as a first method, a coating liquid containing a functional resin (and, if necessary, a filler or the like) is coated on a porous substrate to form a coating film. Next, after the resin of the coating film is solidified, A fluorine-containing nonionic surfactant is adhered to a coating film by applying a specific solution of a fluorine-containing nonionic surfactant of the present invention to a coating film to form a porous layer containing a fluorine-containing nonionic surfactant on the porous substrate Or the like. As a second method, a coating solution containing a functional resin and a specific fluorine-containing nonionic surfactant of the art (optionally, a filler or the like) is prepared and the coating solution is coated on the porous substrate to form a coating film , And then solidifying the resin of the coating film to form a porous layer containing the fluorine-containing nonionic surfactant on the porous substrate.

When the separator is a composite film, a solution containing a specific fluorine-containing nonionic surfactant of the present invention is prepared, and this solution is applied to a porous sheet such as a nonwoven fabric or paper (the filler may be carried in advance, if necessary) Followed by drying, and then impregnating the fluorine-containing nonionic surfactant on the porous sheet. The application of the solution can be carried out by a coating method, a dipping method, or a spraying method.

The porous layer containing the functional resin can be formed by, for example, the following wet coating method.

The wet coating method is a wet coating method which comprises: (i) dissolving and dispersing a functional resin in a solvent to prepare a coating liquid, coating the coating liquid on the porous substrate, and (ii) thereafter subjecting the functional resin in the coating film to phase separation And (iii) washing with water and drying to form a porous layer on the porous substrate. The coating liquid may contain a fluorine-containing nonionic surfactant, a filler, or the like, depending on purposes and the like.

The separator for a non-aqueous secondary battery according to one embodiment of the present invention can be produced by a method in which the porous layer is formed as an independent sheet, the porous layer is superposed on the porous substrate, and the porous layer is subjected to thermocompression bonding or composite formation with an adhesive.

Next, a separator for a non-aqueous secondary battery according to another embodiment of the present invention will be described.

A separator for a nonaqueous secondary battery according to another embodiment of the present invention (also referred to as a &quot; separator &quot; in the same manner as described above) is formed by a polyvinylidene fluoride resin (hereinafter simply referred to as &quot; PVDF resin ), And it is not particularly limited as long as it is composed of a film containing a specific fluorine-containing nonionic surfactant to be described later, and may be either a single layer film or a multilayer film, and either a porous film or a non- It is acceptable. From the viewpoint of ion permeability, the separator of the present invention is preferably a single-layer film or a multi-layer film which is a porous film.

The film structure in the case of the separator according to another embodiment may be any of the following embodiments.

(1) Single layer film of PVDF resin

For example, a single layer film composed of a PVDF resin and a fluorine-containing nonionic surfactant, or a single layer film formed by mixing a PVDF resin, a filler, and a fluorine-based nonionic surfactant.

(2) Composite film of PVDF resin

For example, a composite film in which a PVDF resin and a fluorine-containing nonionic surfactant are provided on the inside and on the surface of a fibrous sheet such as a nonwoven fabric or a paper, and the composite film may also be provided with a filler.

(3) A laminated film of PVDF resin

For example, a laminated film having a porous substrate and a layer (preferably a porous layer) comprising a PVDF resin and a fluorine-containing nonionic surfactant laminated on one surface or both surfaces of the porous substrate can be exemplified. The PVDF system The layer containing the resin and the fluorine-containing nonionic surfactant may further include a filler.

- polyvinylidene fluoride resin -

Examples of the polyvinylidene fluoride resin include a homopolymer of vinylidene fluoride (that is, polyvinylidene fluoride) and a copolymer of vinylidene fluoride and another copolymerizable monomer (that is, polyvinylidene fluoride copolymer).

As the polyvinylidene fluoride resin, a mixture of polyvinylidene fluoride and polyvinylidene fluoride copolymer may be used.

The details of the polyvinylidene fluoride resin in the separator according to another embodiment are not limited to the polyvinylidene fluoride resin as the preferable adhesive resin contained in the porous layer in the embodiment of the present invention, The same is true of the preferred embodiment.

- Fluorine-containing nonionic surfactant -

A separator for a nonaqueous secondary battery according to another embodiment of the present invention is a fluorine-based surfactant which has a hydrophilic structural unit at one end of a compound structure and a hydrophobic structural unit containing a fluorine atom at the other end And at least one nonionic fluorine-containing surfactant having a structural unit.

A separator using a polyvinylidene fluoride (PVDF) resin has a hydrophobic structural unit at one end and a hydrophobic structural unit containing a fluorine atom at the other end while being easily charged by the presence of a PVDF resin on the surface thereof. By the presence of the ionic fluorine-based surfactant having a specific structure, charging is suppressed, and furthermore, the internal resistance of the battery can be remarkably reduced. This not only improves the handling property but also improves the output characteristics of the battery.

This is presumably because, in the fluorine-based surfactant, the hydrophobic structural unit is friendly to the resin of the separator and the hydrophilic structural unit, particularly the alkylene oxide chain, is friendly to the electrolytic solution. However, It is not necessarily clear.

The fluorine-containing nonionic surfactant preferably has an alkylene oxide chain as a hydrophilic structural unit on one side of the terminal. The fluorine-containing nonionic surfactant in the present invention preferably has a fluoroalkyl group or fluoroalkenyl group as a hydrophobic structural unit on the other side of the terminal.

The details of the fluorine-containing nonionic surfactant in the separator for a non-aqueous secondary battery according to another embodiment of the present invention are not particularly limited as far as the content of the fluorine-containing nonionic surfactant in the separator is not limited, Containing nonionic surfactant having a fluorine atom-containing hydrophobic structural unit and a hydrophilic structural unit, and the same also applies to preferred embodiments.

The content of the fluorine-containing nonionic surfactant in the separator for a non-aqueous secondary battery according to another embodiment of the present invention is not particularly limited as long as the content of the fluorine-containing nonionic surfactant in the separator for antireflection, reduction in internal resistance of the cell, Is preferably in the range of 0.1 mass% to 20 mass%, and more preferably in the range of 5 mass% to 15 mass%, with respect to the polyvinylidene fluoride resin from the viewpoint of adjustment to the polyvinylidene fluoride resin.

When the content of the fluorine-containing nonionic surfactant is 0.1 mass% or more, it is possible to prevent electrification and to reduce the internal resistance of the battery, thereby achieving excellent handling properties. When the content of the fluorine-containing nonionic surfactant is 20 mass% or less, it is advantageous in that the water content in the separator can be suppressed.

The content of the fluorine-containing nonionic surfactant in the separator indicates the total amount of the amount contained in the separator and the amount adhered to the surface of the separator. The content of the fluorine-containing nonionic surfactant in the separator was determined by ¹ H-NMR and ¹⁹ F-NMR, which were determined by NMR, using dimethylsulfoxide (DMSO) as a separator, immersing the separator in DMSO, .

The method for containing the fluorine-containing nonionic surfactant in the separator for a nonaqueous secondary battery according to another embodiment of the present invention is not particularly limited, and for example, the following two methods can be mentioned.

First, there is a method of preparing a solution in which a fluorine-containing nonionic surfactant is dissolved in an appropriate solvent, treating the separator using the solution, and removing the solvent by a method such as drying . In this method, it is necessary to select a solvent which can be removed by drying or the like. Examples of the solvent include low-boiling organic solvents such as methanol and ethanol, and water. The concentration of the fluorine-containing nonionic surfactant in the solution and the treatment conditions (such as the time and temperature for the treatment) may be adjusted so as to exhibit desired properties, and there is no particular limitation.

The treatment of the separator using the solution can be performed by a method such as coating or spraying the solution on the separator, or immersing the separator in the solution.

Secondly, there is a method of dissolving a fluorine-containing nonionic surfactant in a solution of a polyvinylidene fluoride resin used for molding a separator. Also in this method, the concentration of the fluorine-containing nonionic surfactant may be adjusted so as to exhibit desired properties and is not particularly limited.

-filler-

The separator for a non-aqueous secondary battery according to another embodiment of the present invention may contain at least one of fillers. By including the filler, the slidability and the heat resistance of the separator can be improved. As the filler, a filler and other components made of an inorganic material or an organic material may be contained. Examples of the inorganic filler include metal oxides such as alumina, metal hydroxides such as magnesium hydroxide, and the like. As the organic filler, for example, acrylic resin and the like can be mentioned.

A separator for a nonaqueous secondary battery according to another embodiment of the present invention is a separator for a nonaqueous secondary battery having a layer comprising a polyvinylidene fluoride resin and a specific fluorine-containing nonionic surfactant of the art as a surface layer forming at least one surface And may be composed of any of the film structures described above.

The separator according to another embodiment of the present invention is preferably composed of the above-described laminated film in that the effect according to another embodiment of the present invention can be more effectively exhibited. Specifically, the following laminated film is used.

A separator according to another embodiment of the present invention is a separator comprising a porous substrate and a porous substrate provided as a surface layer for forming a surface on one side or both surfaces of the porous substrate and comprising a polyvinylidene fluoride resin and a specific fluorine- Is preferably a laminated film having a porous layer.

[Porous substrate]

A porous substrate means a substrate having voids or pores therein. As such a substrate, a microporous membrane; A porous sheet made of a fibrous material such as a nonwoven fabric or a ground sheet; A composite porous sheet in which one or more other porous layers are laminated on these microporous membranes or porous sheets; And the like. The microporous membrane means a membrane having a plurality of micropores therein and a structure in which these micropores are connected to each other so that gas or liquid can pass from one surface to the other surface.

The separator for a non-aqueous secondary battery according to another embodiment of the present invention is synonymous with the porous substrate in the embodiment of the present invention, and preferable embodiments thereof are also the same. However, the pore strength of the porous substrate may be 200 g or more from the viewpoint of improving the production yield.

[Porous layer]

In another embodiment of the present invention, the porous layer has a plurality of micropores therein and has a structure in which these micropores are connected to each other, so that the gas or liquid can pass from one surface to the other surface to be. In another embodiment of the present invention, when the separator has a porous layer, it is preferable that the porous layer has adhesiveness to an object such as an electrode. The porous layer contains a polyvinylidene fluoride resin, so that the porous layer can be formed as a layer imparted with adhesiveness.

To the porous layer, a filler composed of the aforementioned inorganic substance or organic substance may be added for the purpose of improving the heat resistance and improving the handling property.

In another embodiment of the present invention, the porous layer is composed of a layer which is provided as a surface layer (outermost layer) of the separator on one surface or both surfaces of the porous substrate and in which, when the separator and the electrode are stacked and thermally pressed, . The porous layer is preferred because the sun's side on both sides of the porous substrate is superior to the sun on one side of the porous substrate in that the cycle characteristics of the battery are excellent. When the porous layer is provided on both surfaces of the porous substrate, both surfaces of the separator can be well bonded to both electrodes via the porous layer.

The coating amount of the polyvinylidene fluoride resin of the porous layer is preferably from 0.5 g / m 2 to 1.5 g / m 2 on one side of the porous substrate from the viewpoint of adhesion with the electrode and ion permeability, more preferably from 0.75 g / To 1.25 g / m &lt; 2 &gt;.

When the porous layer is provided on both surfaces of the porous substrate, the coating amount of the polyvinylidene fluoride resin of the porous layer is preferably 1.0 g / m 2 to 3.0 g / m 2 as a total of both surfaces, g / m &lt; 2 &gt;.

If the coating amount of the porous layer is 1.0 g / m 2 or more (0.5 g / m 2 in the case of one side), adhesion with the electrode becomes better, and in the case of a battery, excellent in cycle characteristics. When the coating amount of the porous layer is 3.0 g / m 2 (or 1.5 g / m 2 in the case of one side), the ion permeability is better and the load characteristic of the battery is excellent.

When the porous layer is provided on both surfaces of the porous substrate, it is preferable that the difference between the coating amount of one surface and the coating amount of the other surface is 20% or less with respect to the coating amount of both surfaces. If the difference is 20% or less, the separator is difficult to curl, and as a result, the handling property is further improved, and the cycle characteristics are hardly deteriorated.

In the separator for a non-aqueous secondary battery according to another embodiment of the present invention, the average thickness, porosity and average pore size of the porous layer are the same as in the case of the porous layer in the embodiment of the present invention , And the preferred embodiment is the same.

~ Physical Properties of Separator for Non-aqueous Secondary Battery ~

The total thickness, porosity, gage value, membrane resistance, and curling ratio of the separator for a non-aqueous secondary battery according to another embodiment of the present invention can be measured by using a separator for a non-aqueous secondary battery according to one embodiment of the present invention And the preferred embodiment is the same. The separator for a non-aqueous secondary battery according to another embodiment of the present invention preferably has a multi-structure structure from the viewpoint of ion permeability, and therefore it is preferable that the separator for a non-aqueous secondary battery, The value obtained by subtracting the Gurley value of the porous substrate is also the same as that in the case of the separator for a non-aqueous secondary battery according to one embodiment of the present invention, and preferable examples are the same.

The chargeability (antistatic effect) in the separator for a non-aqueous secondary battery according to another embodiment of the present invention can be confirmed by a half-life measuring method described in JIS L 1094 (1997). However, since the environment for use of the separator is under a dry environment, it is preferable to confirm the antistatic effect by assuming the environment.

In another embodiment of the present invention, the half life measured under an environment of a dew point of -50 deg. C after the separator is allowed to stand for one day under an environment of a dew point of -50 deg. C is taken as an index of the antistatic effect. In order to ensure good handling properties, the half life measured by this method is preferably 100 seconds or less, more preferably 50 seconds or less.

The effect of reducing the internal resistance of the battery in the separator for a non-aqueous secondary battery according to another embodiment of the present invention is the effect of the fluorine-containing nonionic surfactant applied for the above-mentioned antistatic. This improves the output characteristics of the battery. The detailed reason why the internal resistance is reduced is not necessarily clarified, but is presumed as follows.

That is, it is presumed that the specific fluorine-containing nonionic surfactant of the technique attached to the separator elutes into the electrolytic solution and the fluorine-containing nonionic surfactant eluted, acts on the electrode to reduce the reaction resistance.

In order to obtain a good internal resistance reduction effect, the fluorine-containing nonionic surfactant may be attached to the separator to such an extent that a half-life period for securing handling properties as described above can be obtained. Therefore, from the viewpoint of reducing the internal resistance, the aforementioned half-life period is preferably 100 seconds or less, more preferably 50 seconds or less.

The water content of the separator for a non-aqueous secondary battery according to another embodiment of the present invention is preferably suppressed to be low. The water content is preferably 500 ppm or less, more preferably 300 ppm or less, and even more preferably 100 ppm or less. The water content is a value measured by a Karl Fischer moisture meter.

From the viewpoint of obtaining a separator with a low water content, the hydrophilic structural unit of the fluorine-containing nonionic surfactant contained in the separator becomes important, and it is necessary to select the type and the existence ratio of the hydrophilic structural unit as desired. For example, when the hydrophilic structural unit is an alkylene oxide chain (for example, ethylene oxide chain), the addition mole number of the alkylene oxide chain is an indicator thereof. Specifically, from the viewpoint of suppressing the water content of the separator, the case where the average addition mole number of the alkylene oxide chain (for example, ethylene oxide chain) is 5 mol or more and 14 mol or less is particularly preferable.

In the separator for a non-aqueous secondary battery according to another embodiment of the present invention, the amount of the non-fluorine-based nonionic surfactant to be adhered is not particularly limited as long as the half life and the moisture content can be realized.

~ Manufacturing Method of Separator for Non-aqueous Secondary Battery ~

A separator for a non-aqueous secondary battery according to another embodiment of the present invention is produced, for example, by the following method.

As a first method, when the separator is a laminated film, a coating liquid containing a polyvinylidene fluoride resin (and a filler if necessary) is coated on the porous substrate to form a coating film, and then the resin of the coating film The solidified coating film is solidified, and a solution of a specific fluorine-containing nonionic surfactant of the present invention is applied to the solidified coating film to adhere the fluorine-containing nonionic surfactant to the coating film. As a result, a porous film containing the fluorine-containing nonionic surfactant Layer may be formed on a porous substrate.

As a second method in the case where the separator is a laminated film, a coating solution containing a polyvinylidene fluoride resin and a specific fluorine-containing nonionic surfactant of the art (and a filler if necessary) is prepared, May be coated on a porous substrate to form a coating film, and then the resin of the coating film may be solidified to form a porous layer containing the fluorine-containing nonionic surfactant on the porous substrate.

As a third method, when the separator is a single-layer film, a coating liquid containing a polyvinylidene fluoride resin (and a filler if necessary) is coated on the release sheet to form a coating film, and the resin of the coating film is solidified , Or by applying a solution of a specific fluorine-containing nonionic surfactant of the present invention to the solidified coating film to attach the fluorine-containing nonionic surfactant to the solidified coating film, followed by peeling from the release sheet. The solution may be applied by a coating method, a dipping method, or a spraying method.

As a fourth method, when the separator is a composite membrane, a solution containing a polyvinylidene fluoride resin and a specific fluorine-containing nonionic surfactant of the art (optionally, a filler or the like) is prepared, Or may be produced by applying a porous sheet such as a nonwoven fabric or paper (optionally, a filler may be carried in advance), and drying the resultant, and carrying the polyvinylidene fluoride resin and the fluorine-containing nonionic surfactant on the porous sheet. The application of the solution can be carried out by a coating method, a dipping method, or a spraying method.

The porous layer containing the polyvinylidene fluoride resin can be formed by, for example, the following wet coating method.

The wet coating method comprises (i) dissolving and dispersing a polyvinylidene fluoride resin in a solvent to prepare a coating liquid, coating the coating liquid on the porous substrate, (ii) thereafter, (Iii) washing with water and drying to form a porous layer on the porous substrate while inducing phase separation by the coagulating liquid.

In addition, the coating liquid may contain a fluorine-containing nonionic surfactant, a filler, and the like as the case may be.

Details of the wet coating method according to the present invention are as follows.

Examples of the solvent for dissolving the polyvinylidene fluoride resin (hereinafter also referred to as &quot; good solvent (good solvent) &quot;) used for preparing the coating liquid include N-methylpyrrolidone, dimethylacetamide, dimethylformamide, dimethyl A polar amide solvent such as formamide is suitably used.

From the viewpoint of forming a good porous structure, it is preferable to mix a phase separator which induces phase separation in addition to both solvents. Examples of the phase-separating agent include water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, and tripropylene glycol. The phase separation agent is preferably added in such a range that a suitable viscosity can be ensured for the coating.

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

From the viewpoint of forming a good porous structure, it is preferable that the coating liquid contains polyvinylidene fluoride resin in a concentration of 3% by mass to 10% by mass.

When a filler or other component is contained in the porous layer, it may be mixed or dissolved in the coating liquid.

The application of the coating liquid to the porous substrate may be performed by a conventional coating method such as Meyer bar, die coater, reverse roll coater, or gravure coater. The porous substrate may be coated by immersing the porous substrate in the coating liquid.

When the porous layer is formed on both surfaces of the porous substrate, it is preferable from the viewpoint of productivity that the coating liquid is coated on both surfaces of the substrate simultaneously.

The porous layer can be produced by a dry coating method in addition to the wet coating method described above. Here, the dry coating method is a method of coating a porous substrate with a coating liquid containing, for example, a polyvinylidene fluoride resin and a filler, drying the coating layer and volatilizing the solvent to remove the porous layer . However, since the dry coating method tends to make the coating layer more dense as compared with the wet coating method, the wet coating method is preferable in that a good porous structure can be obtained.

The coagulating solution is generally composed of a good solvent used for preparing the coating liquid, a phase separating agent, and water. The mixing ratio of the good solvent and the phase separation agent is preferably adjusted to the mixing ratio of the mixed solvent used for preparation of the coating solution. The concentration of water is suitably 40% by mass to 90% by mass in view of formation of a porous structure and productivity.

Examples of the method for coagulating the heat-resistant resin or the adhesive resin include a method of spraying a coagulating solution onto a porous substrate after coating, a method of immersing the porous substrate in a bath containing a coagulating solution (coagulating bath), and the like.

The drying method is not particularly limited, but the drying temperature is suitably from 50 캜 to 100 캜. When a high drying temperature is applied, it is preferable to employ a method of bringing the roll into contact with a heat roll so that dimensional changes due to heat shrinkage do not occur.

After the step (i) and step (ii), the step (v) may further comprise a step of drying the porous substrate after coating. In this case, the drying temperature in the step (v) may be a temperature at which the solvent can be removed, and a range of 50 ° C to 200 ° C is suitable.

The separator for a non-aqueous secondary battery according to another embodiment of the present invention can also be produced by a method in which the porous layer is formed as an independent sheet and the porous layer is superimposed on the porous substrate and subjected to thermocompression bonding or composite formation with an adhesive . As a method for producing the porous layer as an independent sheet, a coating liquid containing a polyvinylidene fluoride resin and a filler is coated on a release sheet and a porous layer is formed by applying the above wet coating method or dry coating method , And a method of peeling the porous layer from the release sheet.

[Non-aqueous secondary battery]

A non-aqueous secondary battery according to an embodiment of the present invention is a non-aqueous secondary battery that obtains an electromotive force by doping and dedoping lithium, and includes a positive electrode, a negative electrode, and a separator Respectively. The non-aqueous secondary battery has a structure in which a battery element in which an electrolyte is impregnated into a structure in which a cathode and an anode are opposed to each other with a separator interposed therebetween is sealed (enclosed) in a casing.

Doping refers to the phenomenon in which lithium ions enter the active material of an electrode such as a positive electrode, which means that the electrode is inserted, held, adsorbed, or inserted.

The non-aqueous secondary battery, which is an embodiment of the present invention, is suitable for a nonaqueous electrolyte secondary battery, particularly a lithium ion secondary battery.

The non-aqueous secondary battery according to the embodiment of the present invention is provided with the separator of the art as a separator, so that the internal resistance of the battery is suppressed to be low, and the output characteristic is excellent.

The positive electrode includes an active material layer including a positive electrode active material and a binder resin

Or may be formed on a current collector. The active material layer may further include a conductive auxiliary agent.

As the positive electrode active material, such as and the like such lithium-containing transition metal oxide, _{specifically, LiCoO 2, LiNiO 2, LiMn} 1/2 Ni 1/2 O 2, LiCo 1/3 Mn 1/3 Ni 1 / ₃ O ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiCo _1/2 Ni _1/2 O ₂ , and LiAl _1/4 Ni _3/4 O ₂ .

As the binder resin, for example, a polyvinylidene fluoride resin can be given.

Examples of the conductive agent include carbon materials such as acetylene black, ketjen black and graphite powder.

As the collector, for example, an aluminum foil, a titanium foil and a stainless foil having a thickness of 5 mu m to 20 mu m can be given.

In the embodiment of the non-aqueous secondary battery of the present invention, when placing a porous layer on the anode side of the separator, since the poly-vinylidene fluoride resin to the oxidation resistance excellent, possible to operate a high voltage more than 4.2V LiMn _1/2 Ni _1/2 O _2, LiCo advantageously _{1/3 Mn 1/3 Ni} 1/3 O easier to apply the positive electrode active material _2, and so on.

The negative electrode may have a structure in which the active material layer including the negative electrode active material and the binder resin is molded on the current collector. The active material layer may further include a conductive auxiliary agent.

Examples of the negative electrode active material include a material capable of electrochemically occluding lithium, and specifically, for example, a carbon material; An alloy of silicon, tin, aluminum, etc. with lithium; And the like.

Examples of the binder resin include polyvinylidene fluoride resin and styrene-butadiene rubber.

Examples of the conductive agent include carbon materials such as acetylene black, ketjen black and graphite powder.

As the current collector, for example, copper foil, nickel foil and stainless foil having a thickness of 5 mu m to 20 mu m can be cited.

Instead of the above-described negative electrode, a metal lithium foil may be used as the negative electrode.

The electrolytic solution is, for example, a solution in which a lithium salt is dissolved in a non-aqueous solvent.

Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , and the like.

Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate; Chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and fluorine substituents thereof; cyclic esters such as? -butyrolactone and? -valerolactone; These may be used alone or in combination.

As the electrolytic solution, the mass ratio of the cyclic carbonate to the chain carbonate (cyclic carbonate / chain carbonate) is mixed in the range of 20/80 to 40/60 and the lithium salt is dissolved in the range of 0.5M to 1.5M.

Examples of the exterior material include metal cans and aluminum laminate film packs.

The shape of the battery is square, cylindrical, coin-shaped, and the like, but the separator according to the embodiment of the present invention is suitable for any shape.

The separator for a non-aqueous secondary battery according to the embodiment of the present invention is not only difficult to charge, but also includes a polyvinylidene fluoride resin and is excellent in adhesion to an electrode, And a good battery output is obtained from both chemical sides.

From this point of view, deterioration of output characteristics due to impact from the outside, formation of gaps between the electrodes and the separator due to expansion and contraction of electrodes due to charging and discharging, charging accompanying charging and discharging, A separator for a non-aqueous secondary battery according to an embodiment of the present invention is suitable for a soft pack battery using an aluminum laminate film pack as an exterior material.

A non-aqueous secondary battery according to an embodiment of the present invention is a nonaqueous secondary battery, for example, in which a laminate in which a separator of the technology is disposed between an anode and a cathode is impregnated with an electrolyte to be accommodated in a casing (for example, an aluminum laminate film pack) , And pressing the laminate from above the casing (press (preferred press pressure is 0.5 to 40 kg / cm 2). By this thermal press, the electrode and the separator are adhered well. For details of the manufacturing method, reference can be made, for example, to the description of paragraphs 0059 to 0067 of International Publication No. 2014/021289.

The separator for a non-aqueous secondary battery according to an embodiment of the present invention includes a polyvinylidene fluoride resin and can be bonded to an electrode by overlapping. Therefore, in the manufacturing process of the battery, the above-described pressing is not essential, but it is preferable to perform the pressing in view of enhancing the adhesion between the electrode and the separator. From the viewpoint of enhancing the adhesion between the electrode and the separator, a method of pressurizing (hot pressing; preferable temperature is 80 to 100 占 폚) while heating is preferable.

As a battery structure, a method of disposing the separator between the positive electrode and the negative electrode may be a method of stacking the positive electrode, the separator and the negative electrode in this order at least one layer at a time (so-called stacking method) Or may be a method of winding in the longitudinal direction.

(Example)

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. It should be noted, however, that the embodiments of the present invention are not limited to the following embodiments unless they exceed the general inventive concept.

(Measurement and evaluation)

The following measurements and evaluations were made on the separator and the lithium ion secondary battery produced in the following examples and comparative examples. The results of measurement and evaluation are shown in Table 1 below.

[One. Content of Surfactant]

From the results of ¹ H-NMR and ¹⁹ F-NMR obtained by immersing the separator (size: 20 cm x 20 cm) in dimethylsulfoxide, extracting the dimethyl sulfoxide soluble component in the separator, and incorporating it into the separator The amount of the surfactant was calculated.

[2. Moisture content]

The moisture content (ppm) with respect to the weight of the separator after leaving the separator after being left to stand for 1 hour in a drier at a dew point of -50 DEG C was measured with a Karl Fischer moisture meter (AQ-22010S, NUMASAN CO., LTD.).

[3. Internal resistance of battery]

The operation of charging and discharging the test lithium ion secondary battery under a constant current and constant voltage charge of 0.2C, 4.2V, 8 hours under a charging condition of 0.2C and a constant current discharge of 2.75V cutoff at 25 DEG C Charging and discharging of 5 cycles) was carried out, and then 0.2C, 4.2V and 8 hours of constant current charging were carried out. In this state, the AC impedance measurement was carried out at 25 占 폚. At this time, the conditions of the AC impedance measurement were set to an amplitude of 10 mV and a frequency of 0.1 Hz.

The resistance (ohm 占 ㎠ m2) obtained under the above measuring conditions was defined as the internal resistance of the battery.

[4. Chargeability (half-life)]

The half life period (second) of the separator was measured by using a half-life measuring method described in JIS L 1094 (1997) using an Onestrometer-V1 (manufactured by Shimadzu Corporation), and the charging performance was evaluated did. The measurement was performed by allowing the separator to stand in a drier at a dew point of -50 占 폚 for one day and humidifying the sample after being left in a dryer at a dew point of -50 占 폚.

(Example 1)

- Fabrication of Separator for Non-aqueous Secondary Battery -

0.12% by mass of a fluorine-containing nonionic surfactant, Futagent 222F (perfluoroalkenyl ethylene oxide adduct (ethylene oxide average addition mole number: 22 moles); NEOSSHAE) was dissolved in methanol, and a polyethylene microporous membrane Film thickness: 16 탆, gull value: 150 sec / 100 ml, porosity: 40%). Thereafter, it was dried to obtain a separator for a non-aqueous secondary battery, which is an embodiment of the present invention.

Futagent 222F is a polyoxyethylene ether in which one end is a perfluoroalkyl structure and the other end is an ethylene oxide chain.

The Gurley value was measured with a Gurley type Densometer (G-B2C, manufactured by Toyoseki) according to JIS P8117 (2009).

The porosity was obtained from the following formula [?: Porosity%, Ws: basis weight (g / m 2), ds: true density (g / cm 3), t: film thickness (μm)]. The film thickness t may be, for example, a value obtained by subtracting the thickness of the porous substrate from the thickness of the separator.

  ? = {1-Ws / (ds? t)} 100

- Fabrication of non-aqueous secondary battery -

(1) Production of cathode

87 g of artificial graphite as a negative electrode active material, 3 g of acetylene black as a conductive additive, and 10 g of polyvinylidene fluoride as a binder were dissolved in N-methyl-pyrrolidone (NMP) so that the concentration of polyvinylidene fluoride became 8.5% And the mixture was stirred with a twin-screw type mixer to prepare a negative electrode slurry. The slurry for the negative electrode was applied to a copper foil having a thickness of 25 mu m as the negative electrode current collector, followed by drying and pressing to obtain a negative electrode having a negative active material layer.

(2) Fabrication of anode

89.5 g of lithium cobaltate powder as a positive electrode active material, 4.5 g of acetylene black as a conductive additive, and 6 g of polyvinylidene fluoride as a binder were dissolved in N-methyl-pyrrolidone (NMP) so that the concentration of vinylidene fluoride was 6% , And the mixture was stirred with a twin-screw type mixer to prepare a positive electrode slurry. The slurry for the positive electrode was applied to an aluminum foil having a thickness of 20 占 퐉 as a positive electrode current collector, followed by drying and pressing to obtain a positive electrode having a positive electrode active material layer.

(3) Preparation of lithium ion secondary battery for testing

The lead tabs were welded to the obtained positive electrode and negative electrode, and then the positive electrode, the separator and the negative electrode were laminated in this order, and the electrolyte solution was impregnated. Then, the battery was sealed in an aluminum pack using a vacuum sealer to prepare a test lithium ion secondary battery .

A mixed solution of 1M LiPF _{6 in which} ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a mass ratio (EC: EMC) of 3: 7 was used as the electrolytic solution.

(Example 2)

The procedure of Example 1 was repeated except that the amount of fluorine-containing nonionic surfactant (Futagent 222F) dissolved in methanol was changed from 0.12 mass% to 0.95 mass%, and a nonaqueous secondary battery separator And a lithium ion secondary battery for testing was produced.

(Example 3)

A nonaqueous secondary battery separator (non-aqueous secondary battery) was produced in the same manner as in Example 1, except that the amount of the fluorine-containing nonionic surfactant (Futagent 222F) in methanol was changed from 0.12 mass% to 0.011 mass% And a lithium ion secondary battery for testing was produced.

(Example 4)

A nonaqueous secondary battery separator (non-aqueous secondary battery) was produced in the same manner as in Example 1, except that the amount of the fluorine-containing nonionic surfactant (Futagent 222F) in methanol was changed from 0.12 mass% to 0.0013 mass% And a lithium ion secondary battery for testing was produced.

(Example 5)

In Example 1, 0.12 parts by mass of a fluorine-containing nonionic surfactant (Futagent 222F) was added to a fluorine-containing nonionic surfactant Futagent 212M (perfluoroalkenyl ethylene oxide adduct (average addition number of ethylene oxide: 12 moles) ; NEOSSHAE Co., Ltd.) was used in place of 0.14 parts by mass of the nonaqueous secondary battery, and a lithium ion secondary battery for testing was produced.

Futagent 212M is a polyoxyethylene ether in which one end is a perfluoroalkenyl structure and the other end is an ethylene oxide chain.

(Example 6)

In Example 1, 0.12 parts by mass of a fluorine-containing nonionic surfactant (Futagent 222F) was added to a fluorine-containing nonionic surfactant, Futagent 208G (perfluoroalkenyl ethylene oxide adduct (ethylene oxide average addition mole number: 8 moles) Manufactured by Nissan Chemical Industries, Ltd.) was replaced by 0.13 parts by mass, and a separator for a non-aqueous secondary battery was obtained in the same manner as in Example 1, and a lithium ion secondary battery for testing was produced.

Futagent 208G is a polyoxyethylene ether in which one end is a perfluoroalkenyl structure and the other end is an ethylene oxide chain.

(Example 7)

0.12 parts by mass of a fluorine-containing nonionic surfactant (FutaGent 222F) was dissolved in 0.12 parts by mass of FutaGent FTX-218 (perfluoroalkenyl ethylene oxide adduct (ethylene oxide average addition mole number: 18 moles) Mass part, a separator for a non-aqueous secondary battery was obtained in the same manner as in Example 1, and a lithium ion secondary battery for testing was produced.

Futagent FTX-218 is a polyoxyethylene ether in which one end is a perfluoroalkenyl structure and the other end is an ethylene oxide chain.

(Comparative Example 1)

A nonaqueous secondary battery separator (nonaqueous secondary battery) was produced in the same manner as in Example 1, except that the amount of the fluorine-containing nonionic surfactant (Futagent 222F) in methanol was changed from 0.12 mass% to 0.00065 mass% And a lithium ion secondary battery for testing was produced.

(Comparative Example 2)

A nonaqueous secondary battery separator (nonaqueous secondary battery) was produced in the same manner as in Example 1, except that the amount of the fluorine-containing nonionic surfactant (Futagent 222F) in methanol was changed from 0.12 mass% to 1.8 mass% And a lithium ion secondary battery for testing was produced.

(Comparative Example 3)

The procedure of Example 1 was repeated except that the fluorine-containing nonionic surfactant (Futagent 222F) was replaced with fluorine-containing anionic surfactant Futagent 110 (Neos Force) A battery separator was obtained, and a lithium ion secondary battery for testing was produced.

(Comparative Example 4)

In the same manner as in Example 1 except that 0.12 parts by mass of a fluorine-containing nonionic surfactant (Futagent 222F) was replaced with 0.14 parts by mass of a fluorine-based cationic surfactant Futagent 310 (Neosusa Co., Ltd.) A separator for a non-aqueous secondary battery was obtained, and a lithium ion secondary battery for testing was produced.

(Comparative Example 5)

Except that 0.12 parts by mass of a fluorine-containing nonionic surfactant (Futagent 222F) was replaced with 0.13 parts by mass of Emerygen 108 (polyoxyethylene lauryl ether; Kaosha), which is a nonionic surfactant, in Example 1 A separator for a non-aqueous secondary battery was obtained in the same manner as in Example 1, and a lithium ion secondary battery for testing was produced.

(Comparative Example 6)

A separator for a non-aqueous secondary battery was obtained in the same manner as in Example 1, except that the polyethylene microporous membrane was immersed in methanol to obtain a separator for a non-aqueous secondary battery in Example 1, without using a fluorine-containing nonionic surfactant , A lithium ion secondary battery for testing was produced.

[Table 1]

As shown in Table 1, the internal resistance of the battery drastically decreased as compared with Comparative Example 6, which did not contain a surfactant, in Examples containing a predetermined amount of the fluorine-containing nonionic surfactant. This is advantageous in that good battery characteristics are obtained.

On the other hand, in Comparative Example 1 in which the adhesion amount of the fluorine-containing nonionic surfactant was small, the effect of reducing the internal resistance of the battery was not observed. On the contrary, in Comparative Example 2 in which the amount of the fluorine-containing nonionic surfactant exceeded a predetermined amount, the effect of reducing the internal resistance was obtained, but the water content in the battery was remarkably increased. If the moisture content is too large, hydrogen fluoride is generated in the battery, so that the durability and reliability of the battery may be significantly damaged.

Further, in Comparative Examples 3 to 4 using an ionic fluorine-containing surfactant and Comparative Example 5 using a non-fluorine-based nonionic surfactant, not only the internal resistance of the battery was not reduced but the internal resistance of the battery was rather increased, Resulting in deterioration of battery characteristics.

(Example 8)

- Fabrication of Separator for Non-aqueous Secondary Battery -

A copolymer (weight average molecular weight = 195,000) of vinylidene fluoride / hexafluoropropylene (= 98.9 mol% / 1.1 mol%) was prepared as a polyvinylidene fluoride resin.

3.8% by mass of the polyvinylidene fluoride resin was dissolved in a mixed solvent of dimethylacetamide (DMAc) and tripropylene glycol (TPG) mixed at a ratio of 7/3 (= DMAc / TPG; mass ratio) . This coating solution was applied on both surfaces of a polyethylene microporous membrane (film thickness: 9 탆, gull value: 150 sec / 100 ml, porosity: about 40%) and this was dissolved in water, dimethylacetamide and tripropylene glycol And immersed in a coagulating solution (water / DMAc / TPG = 57/30/13 [mass ratio]) at 40 ° C to solidify the polyvinylidene fluoride resin.

The coating film was solidified, washed with water, immersed in a 0.1 mass% aqueous solution of Futazent 212M (average molar number of addition of ethylene oxide: 12 moles, fluorine-containing nonionic surfactant manufactured by NEOS Corporation), and dried.

Thus, a separator for a non-aqueous secondary battery was obtained. Table 2 shows the physical properties of the obtained separator.

Here, Futagent 212M is a polyoxyethylene ether in which one end is a perfluoroalkenyl group and the other is an ethylene oxide chain.

The Gurley value was measured with a Gurley type Densometer (G-B2C, manufactured by Toyoseki) according to JIS P8117 (2009).

The porosity was obtained from the following formula [?: Porosity%, Ws: basis weight (g / m 2), ds: true density (g / cm 3), t: film thickness (μm)]. The film thickness t may be, for example, a value obtained by subtracting the thickness of the porous substrate from the thickness of the separator.

  ? = {1-Ws / (ds? t)} 100

- Fabrication of non-aqueous secondary battery -

(1) Production of cathode

87 g of artificial graphite as a negative electrode active material, 3 g of acetylene black as a conductive additive, and 10 g of polyvinylidene fluoride as a binder were dissolved in N-methyl-pyrrolidone (NMP) so that the concentration of polyvinylidene fluoride became 8.5% And the mixture was stirred with a twin-screw type mixer to prepare a negative electrode slurry. The slurry for the negative electrode was applied to a copper foil having a thickness of 25 mu m as the negative electrode current collector, followed by drying and pressing to obtain a negative electrode having a negative active material layer.

(2) Fabrication of anode

89.5 g of lithium cobaltate powder as a positive electrode active material, 4.5 g of acetylene black as a conductive additive, and 6 g of polyvinylidene fluoride as a binder were dissolved in N-methyl-pyrrolidone (NMP) so that the concentration of vinylidene fluoride was 6% , And the mixture was stirred with a twin-screw type mixer to prepare a positive electrode slurry. The slurry for the positive electrode was applied to an aluminum foil having a thickness of 20 占 퐉 as a positive electrode current collector, followed by drying and pressing to obtain a positive electrode having a positive electrode active material layer.

(3) Preparation of lithium ion secondary battery for testing

The lead tabs were welded to the obtained positive electrode and negative electrode, and then the positive electrode, the separator and the negative electrode were laminated in this order, and the electrolyte solution was impregnated. Then, the battery was sealed in an aluminum pack using a vacuum sealer to prepare a test lithium ion secondary battery .

A mixed solution of 1M LiPF _{6 in which} ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a mass ratio (EC: EMC) of 3: 7 was used as the electrolytic solution.

(Example 9)

In Example 8, a fluorine-containing nonionic surfactant (Futagent 212M) was replaced with a 0.1 mass% aqueous solution of Futagent 215M (average molar number of ethylene oxide: 15 moles, a fluorine-containing nonionic surfactant manufactured by NEOS Corporation) , A separator for a non-aqueous secondary battery was obtained in the same manner as in Example 8, and a lithium ion secondary battery for testing was produced. The physical properties of the separator are shown in Table 2.

Here, Futagent 215M is a polyoxyethylene ether in which one end is a perfluoroalkenyl group and the other is an ethylene oxide chain.

(Example 10)

In Example 8, a fluorine-containing nonionic surfactant (Futagent 212M) was replaced with a 0.1 mass% aqueous solution of Futagent 250 (average molar number of addition of ethylene oxide: 22 moles, a fluorine-containing nonionic surfactant available from NEOS Corporation) , A separator for a non-aqueous secondary battery was obtained in the same manner as in Example 8, and a lithium ion secondary battery for testing was produced. The physical properties of the separator are shown in Table 2.

Herein, Futagent 250 is a polyoxyethylene ether in which one end is a perfluoroalkenyl group and the other is an ethylene oxide chain.

(Example 11)

A fluorine-containing nonionic surfactant (Futagent 212M) was obtained in the same manner as in Example 8 except that the fluorine-containing nonionic surfactant (Futagent 212M) was replaced with a 0.1 mass% aqueous solution of Futagent 251 (average molar number of ethylene oxide added: 8 moles, fluorine-containing nonionic surfactant manufactured by NEOS Corporation) , A separator for a non-aqueous secondary battery was obtained in the same manner as in Example 8, and a lithium ion secondary battery for testing was produced. The physical properties of the separator are shown in Table 2.

Here, Futagent 251M is a polyoxyethylene ether in which one end is a perfluoroalkenyl group and the other is an ethylene oxide chain.

(Comparative Example 7)

Example 8 was repeated except that the fluorine-containing nonionic surfactant (Futagent 212M) was replaced with a fluorine-containing anionic surfactant 0.1% by mass aqueous solution of Futagent 110 Thus, a separator for a non-aqueous secondary battery was obtained, and a lithium ion secondary battery for testing was produced. The physical properties of the separator are shown in Table 2.

(Comparative Example 8)

A fluorine-containing nonionic surfactant (Futagent 212M) was obtained in the same manner as in Example 8 except that the fluorine-containing nonionic surfactant (Futagent 212M) was replaced with a 0.1 mass% aqueous solution of Futagent 310 (Neosusa Co.), a fluorochemical cationic surfactant , A separator for a non-aqueous secondary battery was obtained, and a lithium ion secondary battery for testing was produced. The physical properties of the separator are shown in Table 2.

(Comparative Example 9)

A fluorine-containing nonionic surfactant (Futagent 212M) was obtained in the same manner as in Example 8, except that 0.1 mass% aqueous solution of Futagent 245F (average molar number of ethylene oxide: 45 moles, fluorine-containing nonionic surfactant of Neosse , A separator for a non-aqueous secondary battery was obtained in the same manner as in Example 8, and a lithium ion secondary battery for testing was produced. The physical properties of the separator are shown in Table 2.

Here, Futagent 222F is a polyoxyethylene ether having a perfluoroalkenyl group at both ends and an ethylene oxide chain arranged in the center.

(Comparative Example 10)

Except that the fluorine-containing nonionic surfactant (Futagent 212M) was replaced with a 0.1% by mass aqueous solution of Emerygen 120 (polyoxyethylene lauryl ether, Kaosha), which is a nonionic surfactant, A separator for a non-aqueous secondary battery was obtained in the same manner as in Example 8, and a lithium ion secondary battery for testing was produced. The physical properties of the separator are shown in Table 2.

(Comparative Example 11)

A separator for a non-aqueous secondary battery was obtained in the same manner as in Example 8, except that the coating film was solidified and rinsed and then immersed in a 0.1 mass% aqueous solution of Futagent 212M without being subjected to an operation to obtain a separator for a nonaqueous secondary battery, . Table 2 shows the physical properties of the obtained separator.

[Table 2]

As shown in Table 2, in Examples using a fluorine-containing nonionic surfactant having a hydrophilic structural unit and a fluorine atom-containing hydrophobic structural unit at each end, the half-life was small and the charging was suppressed, The resistance was suppressed to be low and good battery characteristics were exhibited.

On the other hand, in Comparative Examples 7 to 8 using an ionic fluorine-containing surfactant, the effect of preventing electrification could not be obtained. Further, even in Comparative Example 9 using a fluorine-containing surfactant having a both-end structure of both terminals, the antistatic effect could not be expected. On the other hand, in Comparative Example 10 in which a non-fluorine-based nonionic surfactant was used, the half-life was small and the antistatic effect was seen, but conversely, the internal resistance of the battery was increased and the battery characteristics were impaired. In Comparative Example 11 which did not contain a surfactant, charging was easy and the internal resistance of the battery was high, which was inferior to the battery characteristics.

The separator for a non-aqueous secondary battery according to an embodiment of the present invention is suitable for a non-aqueous secondary battery, specifically, a lithium ion secondary battery, because it reduces the internal resistance of the battery and improves the output characteristics. The secondary battery provided with the separator according to the embodiment of the present invention can be suitably used for applications in which output characteristics are important.

In the separator for a non-aqueous secondary battery according to another embodiment of the present invention, the separator including a polyvinylidene fluoride resin that can be bonded to the electrode is prevented from being charged, thereby achieving a good handling property, And the output characteristics are improved. Therefore, it can be suitably applied to a non-aqueous secondary battery, specifically, a lithium ion secondary battery. In particular, it is suitable for a lithium ion secondary battery comprising a soft pack enclosure made of an aluminum laminate.

The disclosures of Japanese Application 2014-135222 and Japanese Application 2014-135223 are hereby incorporated by reference in their entirety.

All publications, patent applications, and technical specifications described in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, and technical specification were specifically and individually indicated to be incorporated by reference .

Claims (12)

And a film containing a fluorine-containing nonionic surfactant having a hydrophobic structural unit containing a fluorine atom and a hydrophilic structural unit,
Wherein the content of the fluorine-containing nonionic surfactant is not less than 0.001 g / m 2 and not more than 1 g / m 2. A polyvinylidene fluoride resin disposed on at least a part of at least one surface,
A fluorine-containing nonionic surfactant whose one end is a hydrophilic structural unit and the other is a hydrophobic structural unit containing a fluorine atom
And a separator for a non-aqueous secondary battery. 3. The method of claim 2,
A separator for a non-aqueous secondary battery, wherein the surface layer forming the surface has a layer containing the polyvinylidene fluoride resin and the fluorine-containing nonionic surfactant on one surface or both surfaces. The method according to claim 2 or 3,
A porous substrate,
Wherein the porous substrate is provided as a surface layer that forms the surface on one or both surfaces of the porous substrate, and the layer comprising the polyvinylidene fluoride resin and the fluorine-containing nonionic surfactant
And a separator for a non-aqueous secondary battery. 5. The method of claim 4,
Wherein the porous substrate is a polyethylene microporous membrane. 6. The method according to any one of claims 3 to 5,
Wherein the layer comprising the polyvinylidene fluoride resin and the fluorine-containing nonionic surfactant is a porous layer. 7. The method according to any one of claims 1 to 6,
And a fluoroalkyl group or a fluoroalkenyl group as said fugitive structural unit. 8. The method according to any one of claims 1 to 7,
A separator for a non-aqueous secondary battery having an alkylene oxide chain as the hydrophilic structural unit. 9. The method of claim 8,
Wherein the alkylene oxide chain is an ethylene oxide chain. 10. The method according to claim 8 or 9,
Wherein the average addition mole number of the alkylene oxide chain is 5 mol or more and 25 mol or less. 11. The method according to any one of claims 1 to 10,
Wherein the fluorine-containing nonionic surfactant is at least one selected from a perfluoroalkyl alkylene oxide adduct and a perfluoroalkenyl alkylene oxide adduct. A non-aqueous secondary battery comprising a positive electrode, a negative electrode, and a separator for a non-aqueous secondary battery according to any one of claims 1 to 11 disposed between the positive electrode and the negative electrode, Secondary battery.