KR20180077190A - Separator for non-aqueous secondary battery and non-aqueous secondary battery - Google Patents

Abstract

An adhesive porous layer provided on one surface or both surfaces of the porous substrate, wherein the ratio of hexafluoropropylene monomer units is 5.1% by mass or more and 6.9% by mass or less, and the weight average molecular weight is 8,100 to 3,000,000. Wherein the vinylidene fluoride-hexafluoropropylene binary copolymer comprises 95% by mass or more of the total resin, and wherein the vinylidene fluoride-hexafluoropropylene binary copolymer comprises 95% by mass or more of the total resin.

Description

Separator for non-aqueous secondary battery and non-aqueous secondary battery

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

BACKGROUND ART Non-aqueous secondary batteries represented by lithium ion secondary batteries are widely used as power sources for portable electronic devices such as notebook PCs, mobile phones, digital cameras, and camcorders. Along with the miniaturization and weight reduction of the portable electronic device, the exterior of the non-aqueous secondary battery has been simplified and reduced in weight. As an exterior material, a can made of aluminum has been developed instead of a stainless steel can, Packs made of an aluminum laminate film have been developed. However, since the pack made of the aluminum laminate film is flexible, in the battery (so-called soft pack battery) using the pack as the exterior material, due to the external impact and the expansion and contraction of the electrode accompanying charge / discharge, And the cycle life may be lowered in some cases.

In order to solve the above-described problem, there has been proposed a technique for enhancing the adhesiveness between an electrode and a separator. As one of such techniques, there is known a separator provided with an adhesive porous layer containing a polyvinylidene fluoride resin on a polyolefin microporous membrane. When the separator is hot-rolled over the electrode in the state including the electrolyte, the separator adheres well to the electrode via the adhesive porous layer, so that the cycle life of the soft-pack battery can be improved. A separator in which an adhesive porous layer containing a polyvinylidene fluoride resin is formed on a polyolefin microporous membrane is suitable for a soft pack battery and various technical proposals have been made for the purpose of further improving performance.

For example, Patent Document 1 discloses an adhesive porous layer containing two types of polyvinylidene fluoride resins having different proportions of hexafluoropropylene monomer units. For example, Patent Document 2 discloses a porous layer containing a polyvinylidene fluoride resin and inorganic particles. For example, Patent Document 3 discloses a porous organic polymer membrane containing a polyvinylidene fluoride resin as a ternary copolymer. For example, Patent Document 4 discloses an adhesive porous layer containing a polyvinylidene fluoride resin having a proportion of hexafluoropropylene monomer units of 0.1 mol% to 5 mol%. For example, Patent Document 5 discloses a porous layer containing a polyvinylidene fluoride resin having a weight average molecular weight of 1,000,000 or more.

International Publication No. 2013/058367 Japanese Patent Laid-Open Publication No. 2012-74367 Japanese Patent No. 5171150 International Publication No. 2014/021293 International Publication No. 2016/002567

BACKGROUND ART [0002] In recent years, a non-aqueous secondary battery typified by a lithium ion secondary battery has been studied for its application as a battery for electric power storage and electric vehicles because of its high energy density. In the case where a non-aqueous secondary battery is used as a power storage or electric vehicle, it is necessary to increase the size of the battery. Therefore, with the increase in size of the soft pack battery, an adhesive porous layer containing a polyvinylidene fluoride resin Even when the separator is provided, adhesion between the electrode and the separator is insufficient, resulting in deterioration of the battery capacity, deterioration of charge / discharge characteristics, and deterioration of the battery. It has been demanded to improve the adhesiveness of the adhesive porous layer to electrodes as the size of the battery becomes larger.

[0003] A battery provided with a separator having an adhesive porous layer containing a polyvinylidene fluoride resin generally has a structure in which a laminate of an electrode and a separator is manufactured, the laminate is housed in a casing, (Hereinafter referred to as a " wet heat press "). As the size of a battery becomes larger, a separator having better adhesion by a wet heat press is required.

An embodiment of the present disclosure was made under the above circumstances.

An embodiment of the present disclosure aims at providing a separator for a non-aqueous secondary battery which is excellent in adhesion to an electrode by a wet heat press as a separator having an adhesive porous layer containing a polyvinylidene fluoride resin.

It is also an object of the present disclosure to provide a non-aqueous secondary battery having excellent cell strength and cycle characteristics.

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

[1] A porous substrate comprising a porous substrate and an adhesive porous layer provided on one side or both sides of the porous substrate, wherein the ratio of hexafluoropropylene monomer units is 5.1% by mass or more and 6.9% by mass or less, By weight of a vinylidene fluoride-hexafluoropropylene binary copolymer, wherein the vinylidene fluoride-hexafluoropropylene binary copolymer accounts for not less than 95% by mass of the entire resin, .

[2] The separator for a nonaqueous secondary battery according to [1], wherein the thickness of the one surface of the adhesive porous layer is not less than 0.5 탆 and not more than 5 탆.

[3] The separator for a non-aqueous secondary battery according to [1] or [2], wherein the adhesive porous layer further contains an inorganic filler.

[4] The separator for a nonaqueous secondary battery according to [3], wherein the inorganic filler is at least one selected from metal hydroxides and metal oxides.

[5] The separator for a non-aqueous secondary battery according to [3], wherein the inorganic filler is at least one of magnesium hydroxide and magnesium oxide.

[6] The method according to any one of [3] to [5] above, wherein the content of the inorganic filler in the adhesive porous layer is 40% by volume or more and 85% by volume or less of the total solid content of the adhesive porous layer Separator for non-aqueous secondary battery.

[7] A nonaqueous secondary battery separator as described in any one of [1] to [6], wherein the separator is disposed between the positive electrode and the negative electrode and includes an anode, a cathode, Based secondary battery.

According to the embodiment of the present disclosure, a separator provided with an adhesive porous layer containing a polyvinylidene fluoride resin is provided with a separator for a non-aqueous secondary battery excellent in adhesion to an electrode by a wet heat press.

Further, according to the embodiments of the present disclosure, there is provided a non-aqueous secondary battery having excellent cell strength and cycle characteristics.

Hereinafter, an embodiment will be described. Note that these explanations and examples are for illustrating the embodiments and do not limit the scope of the embodiments.

In the present specification, the numerical range indicated by using " ~ " indicates a range including numerical values before and after " ~ " as the minimum value and the maximum value, respectively.

In this specification, the term " process " is included in the term when the intended purpose of the process is achieved, even if it can not be clearly distinguished from other processes as well as independent processes.

With respect to the separator of the present disclosure, the "longitudinal direction" means the longitudinal direction of the porous substrate and the separator, which are produced in the elongated phase, and the "width direction" means the direction perpendicular to the "longitudinal direction". The " longitudinal direction " may be referred to as " MD direction ", and the " width direction "

In the present specification, the " monomer unit " of the polyvinylidene fluoride resin means a constituent unit of a polyvinylidene fluoride resin and means a constitutional unit obtained by polymerizing monomers.

<Separator for Non-aqueous Secondary Battery>

The separator for a non-aqueous secondary battery of the present disclosure (also simply referred to as &quot; separator &quot;) comprises a porous substrate and an adhesive porous layer provided on one surface or both surfaces of the porous substrate. In the separator of the present disclosure, the adhesive porous layer is composed of a vinylidene fluoride-hexafluoropropylene binary copolymer having a hexafluoropropylene monomer unit ratio of 5.1% by mass to 6.9% by mass and a weight average molecular weight of 830,000 to 3,000,000 And the vinylidene fluoride-hexafluoropropylene binary copolymer accounts for 95% by mass or more of the total resin.

Hereinafter, the vinylidene fluoride monomer unit may be referred to as "VDF unit", the hexafluoropropylene monomer unit may be referred to as "HFP unit", the vinylidene fluoride-hexafluoropropylene binary copolymer may be referred to as "VDF-HFP binary copolymer" , A VDF-HFP binary copolymer having a HFP unit ratio of 5.1 mass% to 6.9 mass% and a weight average molecular weight of 830,000 to 3,000,000 is also referred to as "specific VDF-HFP binary copolymer".

The separator of the present disclosure has an adhesive porous layer containing a specific VDF-HFP binary copolymer in a proportion of 95 mass% or more of the entire resin, and thus is excellent in adhesion to an electrode by a wet heat press. Although this mechanism is not necessarily clear, it is assumed as follows.

The VDF-HFP binary copolymer has higher mobility of the polymer chain when heated, as the ratio of HFP units is larger. Therefore, when the hot press is performed, the VDF-HFP binary copolymer is more likely to adhere to the electrode as the ratio of the HFP units is larger, and also adheres even under a low-temperature hot press condition.

Further, in the VDF-HFP binary copolymer, the larger the proportion of the HFP unit is, the more likely it is to swell in the electrolytic solution. Therefore, when the wet heat press is carried out, the VDF-HFP binary copolymer is likely to adhere to the electrode due to the swelling of the portion having a HFP unit of a certain degree.

Therefore, considering the behavior of the VDF-HFP binary copolymer, the proportion of the HFP unit of the VDF-HFP binary copolymer is advantageous for adhesion to the electrode to some extent.

However, when an adhesive porous layer is formed from a VDF-HFP binary copolymer having a large proportion of HFP units, the porosity tends to be high and the pore size tends to become large. When the porosity of the adhesive porous layer is high and the pore size is large, the area of the VDF-HFP binary copolymer portion as a portion to be adhered to the electrode decreases on the surface of the adhesive porous layer and the VDF-HFP binary copolymer The penis exists. Therefore, the greater the ratio of the HFP unit of the VDF-HFP binary copolymer constituting the adhesive porous layer, the more the adhesion between the adhesive porous layer and the electrode tends to be weakened. In addition, if the porosity of the adhesive porous layer is high and the pore size is large, the ion movement at the electrode interface becomes uneven, adversely affecting the cycle characteristics and the load characteristics of the battery.

If the proportion of the HFP unit of the VDF-HFP binary copolymer is too large, it tends to dissolve in the electrolytic solution and tends to weaken adhesion to the electrode.

Hence, in view of the surface morphology of the adhesive porous layer, it is advantageous that the ratio of the HFP units of the VDF-HFP binary copolymer is small. In order to prevent the VDF-HFP copolymer from dissolving in the electrolytic solution, The ratio of the HFP unit of HFP is preferably not too much.

Thus, the specific VDF-HFP binary copolymer has a proportion of HFP units of 5.1 mass% to 6.9 mass%.

The specific VDF-HFP binary copolymer has a high ratio of HFP units of 5.1 mass% or more, so that the polymer chain has high mobility when heated, and strong adhesion to the electrode can be obtained when hot pressing is performed. On the other hand, the specific VDF-HFP binary copolymer has an HFP unit ratio of 6.9 mass% or less, thereby realizing an adhesive porous layer having a small porosity and small pore size so as not to impair the ion permeability, Realizes a homogeneous surface morphology.

In addition, the specific VDF-HFP binary copolymer swells suitably in the electrolyte due to the ratio of the HFP unit of 5.1 mass% to 6.9 mass%, so that it adheres well to the electrode when the wet heat press is performed and dissolves in the electrolyte It is difficult to swell excessively, so adhesion with the electrode is maintained.

In view of the above, the lower limit of the ratio of the HFP units of the specific VDF-HFP binary copolymer is at least 5.1 mass%, the upper limit of the ratio of the HFP units of the specific VDF-HFP binary copolymer is 6.9 mass% Preferably 6.5 mass% or less, and more preferably 6.0 mass% or less.

In addition, the specific VDF-HFP binary copolymer has a weight average molecular weight (Mw) of 830,000 to 3,000,000.

Since the specific VDF-HFP binary copolymer has a Mw of 810,000 or more, it is possible to sufficiently impart dynamic characteristics to the adhesive porous layer that can withstand the bonding treatment with the electrode. For this reason, it is also possible to increase the pressure under the hot pressing condition, and to firmly adhere the separator to the electrode.

In view of the above, the specific Mw of the VDF-HFP binary copolymer is 810,000 or more, more preferably 1,000,000 or more, and more preferably 1,100,000 or more.

On the other hand, the VDF-HFP binary copolymer having Mw of more than 3000000 makes the viscosity of the coating solution for coating the adhesive porous layer too high, and it is difficult to form the porous adhesive layer having a porous structure.

From the above viewpoint, the Mw of the specific VDF-HFP binary copolymer is 3,000,000 or less, more preferably 2,500,000 or less, and even more preferably 2,000,000 or less.

In this embodiment, 95% by mass or more of the total resin contained in the adhesive porous layer is a specific VDF-HFP binary copolymer. This means that the adhesive porous layer contains substantially no resin other than the specific VDF-HFP binary copolymer and contains substantially only a specific VDF-HFP binary copolymer as the binder resin. As a result, the adhesive porous layer of this embodiment suppresses nonuniformity of the porous structure due to mixing unevenness of a plurality of kinds of resins, and is excellent in uniformity of the porous structure, Realizes the policy.

The effect of the HFP unit ratio of the particular VDF-HFP binary copolymer as described above, the effect of the weight average molecular weight of the particular VDF-HFP binary copolymer, and the effect of the adhesive porous layer containing substantially only the specific VDF-HFP binary copolymer The separator of the present disclosure is excellent in adhesion with the electrode due to the hot press, and particularly excellent in adhesion with the electrode by the wet heat press.

The separator of the present disclosure is excellent in adhesion not only to an electrode using a solvent-based binder (specifically, polyvinylidene fluoride resin) but also to an electrode using an aqueous binder (specifically styrene-butadiene copolymer).

Since the separator of the present disclosure has excellent adhesion to the electrode, the non-aqueous secondary battery to which the separator of the present disclosure is applied has excellent cell strength.

Further, the separator of the present disclosure is excellent in uniformity of the porous structure of the adhesive porous layer and excellent in adhesion to the electrode, so that the non-aqueous secondary battery to which the separator of the present disclosure is applied has excellent cycle characteristics.

According to the separator of the present disclosure, the formation of gaps between the electrode and the separator due to the expansion and contraction of the electrode due to charging and discharging or an external impact is suppressed. Therefore, the separator of the present disclosure is suitable for a soft pack battery using a pack made of an aluminum laminate film as a casing, and according to the separator of the present disclosure, a soft pack battery having a high battery performance is provided.

An embodiment of the separator of the present disclosure is characterized in that the adhesive porous layer contains a specific VDF-HFP binary copolymer at a ratio of 95 mass% or more of the total resin, so that even with a relatively low pressure and a low- Good adhesion. The porous structure of the adhesive porous layer is crushed as the hot press condition is higher at a higher pressure and higher temperature. According to one embodiment of the separator of the present disclosure, the heat press condition can be made relatively mild, And the battery characteristics are excellent. Further, according to the embodiment of the separator of the present disclosure, the temperature at the time of performing the wet heat press can be set to a relatively low temperature, so that the gas generation due to the decomposition of the electrolytic solution and the electrolyte is suppressed.

In one embodiment of the separator of the present disclosure, since the adhesive porous layer contains a specific VDF-HFP binary copolymer in a proportion of 95 mass% or more of the total resin, adhesion between the porous substrate and the adhesive porous layer And the peeling resistance between the layers is improved.

In one embodiment of the separator of the present disclosure, the adhesive porous layer contains a specific VDF-HFP binary copolymer at a ratio of 95 mass% or more of the total resin, so that at the interface between the porous substrate and the adhesive porous layer Is also excellent.

Conventionally, in the separator formed by coating the porous substrate with the adhesive porous layer, the interface between the porous substrate and the porous substrate is likely to be clogged, and the ion movement at the interface is deteriorated, so that it is difficult to realize good battery characteristics.

On the other hand, in the adhesive porous layer in the embodiment of the present disclosure, since the fine porous structure is developed, the distribution of the pores is uniform and the number of pores is large. Therefore, the possibility of connecting the hole of the porous substrate with the hole of the adhesive porous layer is increased, and deterioration of the battery performance due to clogging can be suppressed.

In one embodiment of the separator of the present disclosure, adhesion with the electrode is favorable even by the hot press treatment (herein referred to as &quot; dry heat press &quot;) performed without impregnating the electrolyte solution. Deformation of the laminated body can be suppressed by subjecting the laminated body to the dry heat press before the wet heat press to adhere the electrode and the separator.

Hereinafter, the material, composition, physical properties, etc. of the separator of the present disclosure will be described in detail.

[Porous substrate]

In the present disclosure, a porous substrate refers to a substrate having voids or pores therein. As such a substrate, a microporous membrane; A porous sheet made of fibrous material such as nonwoven fabric or paper; And a composite porous sheet in which one or more other porous layers are laminated on a microporous membrane or a porous sheet. 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 side to the other side.

The porous substrate contains an organic material and / or an inorganic material having electrical insulation.

The porous substrate preferably contains a thermoplastic resin from the viewpoint of imparting a shutdown function to the porous substrate. The shutdown function is a function of preventing the thermal runaway of the battery by blocking the movement of the ions by melting the 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 preferable. Examples of the thermoplastic resin include: polyesters such as polyethylene terephthalate; And polyolefins such as polyethylene and polypropylene. Of these, polyolefins are preferable.

As the porous substrate, a microporous membrane containing a polyolefin (referred to as &quot; polyolefin microporous membrane &quot;) is preferable. As the polyolefin microporous membrane, for example, there can be mentioned a polyolefin microporous membrane which is applied to a conventional separator for a non-aqueous secondary battery, and it is preferable to select a polyolefin microporous membrane having sufficient mechanical properties and ion permeability.

The polyolefin microporous membrane preferably contains polyethylene from the viewpoint of exhibiting a shutdown function, and the content of polyethylene is preferably 95% by mass or more of the mass of the entire polyolefin 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. It is preferable that the microporous membrane contains 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, a polyolefin microporous membrane having a laminated structure of two or more polyolefin microporous membranes, at least one layer containing polyethylene, and at least one layer containing polypropylene is also preferable.

The polyolefin contained in the polyolefin microporous membrane is preferably a polyolefin having a weight average molecular weight (Mw) of 100,000 to 5,000,000. When the Mw of the polyolefin is 100,000 or more, sufficient mechanical properties can be secured. On the other hand, if the Mw of the polyolefin is 5,000,000 or less, the shutdown characteristic is good and the film is easily formed.

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; Nonwoven fabric and paper made of fibrous materials such as heat resistant resins such as aromatic polyamide, polyimide, polyethersulfone, polysulfone, polyether ketone, and polyether imide. Here, 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.

Examples of the composite porous sheet include a microporous membrane or a sheet obtained by laminating a functional layer on a porous sheet. Such a composite porous sheet is preferable from the viewpoint of enabling additional functional addition by the functional layer. From the standpoint of imparting heat resistance, the functional layer is preferably a porous layer containing a heat-resistant resin or a porous layer containing a heat-resistant resin and an inorganic filler. Examples of the heat-resistant resin include aromatic polyamide, polyimide, polyethersulfone, polysulfone, polyether ketone, polyetherimide and the like. Examples of the inorganic filler include metal oxides such as alumina, metal hydroxides such as magnesium hydroxide, and the like. Examples of the method of providing the functional layer on the microporous membrane or the porous sheet include a method of coating the functional layer on the microporous membrane or the porous sheet, a method of bonding the microporous membrane or the porous sheet and the functional layer by an adhesive, And a method of thermocompression bonding.

For the purpose of improving the wettability with the coating liquid for forming the adhesive porous layer, various treatments may be performed on the porous substrate within a range not to impair the properties of the porous substrate. Examples of the surface treatment include a corona treatment, a plasma treatment, a flame treatment, and an ultraviolet ray irradiation treatment.

[Characteristics of porous substrate]

The thickness of the porous substrate is preferably from 3 mu m to 25 mu m, more preferably from 5 mu m to 25 mu m, and further preferably from 5 mu m to 20 mu m, from the viewpoint of obtaining good mechanical properties and internal resistance.

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 gel value (JIS P8117: 2009) of the porous substrate is preferably 50 sec / 100 cc to 800 sec / 100 cc, more preferably 50 s / 100 cc to 400 s / 100 cc, from the viewpoint of preventing short circuit of the battery and obtaining sufficient ion permeability desirable.

The piercing strength of the porous substrate is preferably 200 g or more, more preferably 250 g or more from the viewpoint of improving the production yield. The protruding strength of the porous base material was measured by using a Koto-G5 handy compression tester manufactured by Katotec Corporation under conditions of a curved radius of 0.5 mm and a protrusion speed of 2 mm / sec at the needle tip, and the maximum protrusion load (g) Point.

The average pore size of the porous substrate is preferably 20 nm to 100 nm. When the average pore diameter of the porous substrate is 20 nm or more, ions are easily moved and good cell performance is easily obtained. From this viewpoint, the average pore size of the porous substrate is more preferably 30 nm or more, and more preferably 40 nm or more. On the other hand, when the average pore size of the porous substrate is 100 nm or less, the peeling strength between the porous substrate and the adhesive porous layer can be improved, and a good shutdown function can be also exhibited. From this viewpoint, the average pore diameter of the porous substrate is more preferably 90 nm or less, and more preferably 80 nm or less. The average pore size of the porous substrate is a value measured using a porosimeter. For example, the average pore size of the porous substrate can be measured using a poromerometer (PMI series CFP-1500-A) in accordance with ASTM E1294-89.

[Adhesive porous layer]

In the present disclosure, the adhesive porous layer is a porous layer provided on one side or both sides of the porous substrate and containing a specific VDF-HFP binary copolymer.

The adhesive 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 adhesive porous layer is a layer which is provided as an outermost layer of the separator on one surface or both surfaces of the porous substrate and which can be bonded to the electrode when the separator and the electrode are stacked and thermally pressed.

The adhesive porous layer is preferable from the viewpoint of excellent cell strength and cycle characteristics (capacity retention rate) of the battery, as compared with that on only one side of the porous substrate. If the adhesive porous layer is on both surfaces of the porous substrate, both surfaces of the separator adhere well to both electrodes via the adhesive porous layer.

The adhesive porous layer contains at least a specific VDF-HFP binary copolymer. The adhesive porous layer may further contain a resin or filler other than the specific VDF-HFP binary copolymer.

[Specific VDF-HFP Binary Copolymer]

In this disclosure, a particular VDF-HFP binary copolymer is a binary copolymer having only VDF units and HFP units. The VDF-HFP binary copolymer is preferable from the viewpoint of being able to firmly adhere to the electrode at a proper bonding temperature, as compared with a polybasic copolymer having VDF units, HFP units and other monomer units.

The specific VDF-HFP binary copolymer has a proportion of HFP units of 5.1 mass% to 6.9 mass%. The ratio of HFP units significantly affects the bonding temperature, and if it is less than 5.1% by mass, hot press at high temperature is required, and the hot press process may adversely affect the performance of the battery. When the ratio of the HFP units exceeds 6.9 mass%, the VDF-HFP binary copolymer can not maintain sufficient adhesion with the electrode within the normal battery operating temperature range, which is not preferable. The ratio of the HFP unit of the specific VDF-HFP binary copolymer is more preferably 6.5% by mass or less, and further preferably 6.0% by mass or less.

The specific VDF-HFP binary copolymer has a weight average molecular weight (Mw) of 830,000 to 3,000,000. When the Mw of the VDF-HFP binary copolymer is less than 8, 000, sufficient adhesive strength is not exhibited, and good battery performance may not be obtained. If the Mw of the VDF-HFP binary copolymer exceeds 3,000,000, the moldability of the adhesive porous layer is deteriorated, which is not preferable. Further, it is difficult to obtain a polymer having a weight average molecular weight of more than 3,000,000. The Mw of the specific VDF-HFP binary copolymer is more preferably at least 1 million, more preferably at least 1.1 million, more preferably at most 2.5 million, and most preferably at most 2 million.

Examples of the method for producing a specific VDF-HFP binary copolymer include emulsion polymerization and suspension polymerization. It is also possible to select commercially available VDF-HFP binary copolymers satisfying the ratio of HFP units and the weight average molecular weight.

The content of the specific VDF-HFP binary copolymer contained in the adhesive porous layer is 95% by mass or more, more preferably 97% by mass or more, and further preferably 98% by mass or more of the total amount of the total resin contained in the adhesive porous layer. By mass or more, more preferably 99% by mass or more, and particularly preferably 100% by mass.

[Other Resins]

In the present disclosure, the adhesive porous layer may contain a polyvinylidene fluoride resin other than the specific VDF-HFP binary copolymer, or may contain a resin other than the polyvinylidene fluoride resin. However, the resin other than the specific VDF-HFP binary copolymer contained in the adhesive porous layer is 5 mass% or less of the total amount of the total resin contained in the adhesive porous layer.

Examples of the polyvinylidene fluoride resin other than the specific VDF-HFP binary copolymer include VDF-HFP binary copolymer having a ratio of HFP units different from the specific VDF-HFP binary copolymer; A homopolymer of vinylidene fluoride (i.e., polyvinylidene fluoride); A copolymer of vinylidene fluoride and at least one selected from fluorine-containing monomers such as tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene and vinyl fluoride; Vinylidene fluoride, hexafluoropropylene, and at least one selected from fluorine-containing monomers such as tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene and vinyl fluoride.

Examples of the resin other than polyvinylidene fluoride resin include homopolymers or copolymers of fluorine rubber, acrylic resin, styrene-butadiene copolymer, vinylnitrile compound (acrylonitrile, methacrylonitrile, etc.), carboxymethylcellulose, Hydroxyethylcellulose, hydroxyethylcellulose, hydroxyethylcellulose, hydroxyethylcellulose, hydroxyethylcellulose, hydroxyethylcellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyether (polyethylene oxide, polypropylene oxide and the like).

[filler]

In the present disclosure, the adhesive porous layer may contain a filler made of an inorganic material or an organic material for the purpose of improving the slidability and heat resistance of the separator. In this case, it is preferable that the content and particle size are such that the effect of the present disclosure is not hindered.

The average primary particle diameter of the filler is preferably 0.01 to 5 占 퐉, more preferably 0.1 占 퐉 or more as the lower limit value, more preferably 1.5 占 퐉 or less and more preferably 1 占 퐉 or less as the upper limit value.

The particle size distribution of the filler is preferably 0.1 mu m < d90-d10 < 3 mu m. Here, d10 represents the cumulative 10% particle diameter (占 퐉) in the particle size distribution based on the volume basis calculated from the particle side, and d90 represents the cumulative 90% cumulative particle size distribution (Μm). The particle size distribution can be measured, for example, by using a laser diffraction particle size distribution measuring apparatus (for example, Sysmex Corporation Mastersizer 2000), using water as a dispersion medium and Triton X-100 In a trace amount.

[Inorganic filler]

The adhesive porous layer preferably contains an inorganic filler from the viewpoints of heat resistance of the separator, further improvement of the cell strength, and safety of the battery.

As the inorganic filler in the present disclosure, an inorganic filler which is stable to an electrolytic solution and is electrochemically stable is preferable. Specific examples thereof include metal hydroxides such as magnesium hydroxide, aluminum hydroxide, calcium hydroxide, chromium hydroxide, zirconium hydroxide, cerium hydroxide, nickel hydroxide and boron hydroxide; Metal oxides such as magnesium oxide, alumina, titania, silica, zirconia, and barium titanate; Carbonates such as magnesium carbonate, calcium carbonate and the like; Sulfates such as magnesium sulfate, calcium sulfate and barium sulfate; Metal fluorides such as magnesium fluoride and calcium fluoride; Clay minerals such as calcium silicate and talc. These inorganic fillers may be used singly or in combination of two or more kinds. The inorganic filler may be surface-modified with a silane coupling agent or the like.

As the inorganic filler in the present disclosure, at least one kind of metal hydroxide and metal oxide is preferable from the viewpoints of stability in a battery and safety of a battery. As the inorganic filler in the present disclosure, an inorganic compound containing magnesium (for example, magnesium hydroxide, magnesium oxide, magnesium carbonate, magnesium sulfate, magnesium fluoride and the like) is preferable from the viewpoint of suppressing gas generation in the battery And magnesium hydroxide or magnesium oxide is more preferable. The gas generated by decomposition of the electrolytic solution or the electrolyte contains hydrogen fluoride as a main component. The inorganic compound containing magnesium is likely to form a film on the surface of the particles due to the reaction with hydrogen fluoride, whereby the reaction with hydrogen fluoride It is presumed that the generation reaction of gas which is likely to occur in a chain is suppressed.

The particle shape of the inorganic filler is not particularly limited and may be a shape close to a sphere or a plate, but it is preferably a plate-like particle or a non-aggregated primary particle from the viewpoint of suppressing short-circuiting of the battery.

The content of the inorganic filler contained in the adhesive porous layer is preferably 40% by volume to 85% by volume of the total solid content of the adhesive porous layer. When the content of the inorganic filler is 40 vol% or more, it is expected that the heat resistance and the cell strength of the separator are further improved and the safety of the battery is secured. On the other hand, when the content of the inorganic filler is 85% by volume or less, the formability and shape of the adhesive porous layer are maintained, which contributes to improvement of the cell strength. The content of the inorganic filler is more preferably not less than 45% by volume, more preferably not less than 50% by volume, more preferably not more than 80% by volume, further preferably not more than 75% by volume as the total solid content of the adhesive porous layer.

[Organic filler]

Examples of the organic filler in the present disclosure include crosslinked acrylic resins such as cross-linked polymethyl methacrylate and cross-linked polystyrene, and crosslinked polymethyl methacrylate is preferable.

[Other additives]

The adhesive porous layer in the present disclosure may contain additives such as a dispersing agent such as a surfactant, a wetting agent, a defoaming agent, and a pH adjusting agent. The dispersant is added to the coating liquid for forming the adhesive porous layer for the purpose of improving the dispersibility, the coatability and the storage stability. The wetting agent, antifoaming agent and pH adjusting agent may be added to the coating liquid for forming the adhesive porous layer, for example, for the purpose of improving the affinity with the porous substrate, the air inflow to the coating liquid, .

[Characteristics of Adhesive Porous Layer]

The thickness of the adhesive porous layer is preferably 0.5 m to 5 m on one side of the porous substrate. When the thickness is 0.5 mu m or more, adhesion with the electrode is more excellent, and as a result, the cell strength of the battery is superior. From this viewpoint, the thickness is more preferably 1 占 퐉 or more. On the other hand, when the thickness is 5 mu m or less, the cycle characteristics and the load characteristics of the battery are superior. From this viewpoint, the thickness is more preferably 4.5 占 퐉 or less, and more preferably 4 占 퐉 or less.

When the adhesive 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% by mass or less of the total coating amount of both surfaces. When the amount is 20% by mass or less, the separator is hard to curl, so handling is good and the cycle characteristics of the battery are good.

The porosity of the adhesive porous layer is preferably 30% to 80%. When the porosity is 80% or less, it is possible to secure mechanical characteristics capable of enduring the press process for bonding to electrodes, and the surface opening ratio is not excessively high, which is suitable for securing the adhesive force. On the other hand, if the porosity is 30% or more, it is preferable from the viewpoint that the ion permeability becomes good.

The average pore size of the adhesive porous layer is preferably from 10 nm to 300 nm, more preferably from 20 nm to 200 nm. When the average pore diameter is 10 nm or more (preferably 20 nm or more), when the electrolyte is impregnated in the adhesive porous layer, the blocking of the pores is unlikely to occur even when the resin contained in the adhesive porous layer swells. On the other hand, when the average pore size is 300 nm or less (preferably 200 nm or less), nonuniformity of pores is suppressed on the surface of the adhesive porous layer, the adhesive points are dispersed evenly, great. In addition, when the average pore size is 300 nm or less (preferably 200 nm or less), uniformity of ion movement is high, and the cycle characteristics and the load characteristics of the battery are more excellent.

The average pore diameter (nm) of the adhesive porous layer is calculated by the following equation, assuming that all holes are cylindrical.

d = 4V / S

D is the average pore diameter (diameter) of the adhesive porous layer, V is the void volume per 1 m &lt; 2 &gt; of the adhesive porous layer, and S is the void surface area per 1 m &

The void volume V per m &lt; 2 &gt; of the adhesive porous layer is calculated from the porosity of the adhesive porous layer.

The public surface area S per 1 m &lt; 2 &gt; of the adhesive porous layer is obtained by the following method.

First, the specific surface area (m 2 / g) of the porous substrate and the specific surface area (m 2 / g) of the separator are calculated from the nitrogen gas adsorption amount by applying the BET equation to the nitrogen gas adsorption method. The specific surface area (m 2 / g) is multiplied by each basis weight (g / m 2) to calculate the public surface area per 1 m 2 of each. Then, the public surface area per 1 m &lt; 2 &gt; of the porous substrate is subtracted from the public surface area per m &lt; 2 &gt;

[Characteristics of Separator for Non-aqueous Secondary Battery]

The thickness of the separator of the present disclosure is preferably from 5 mu m to 35 mu m, more preferably from 5 mu m to 30 mu m, further preferably from 10 mu m to 25 mu m, from the viewpoints of mechanical strength, energy density of the battery and output characteristics , And more preferably 10 [micro] m to 20 [micro] m.

The porosity of the separator of the present disclosure is preferably 30% to 60% from the viewpoints of mechanical strength, adhesion to electrodes, and ion permeability.

The gel value (JIS P8117: 2009) of the separator of the present disclosure is preferably 50 sec / 100 cc to 800 sec / 100 cc, more preferably 50 s / 100 cc to 400 s / 100 cc in view of good balance between mechanical strength and membrane resistance More preferable.

The separator of the present disclosure has a value obtained by subtracting the Gurley value of the porous base material from the Gurley value of the separator (the state in which the adhesive porous layer is formed on the porous base material) from the viewpoint of ion permeability (hereinafter referred to as & Is preferably 300 sec / 100cc or less, more preferably 150 sec / 100cc or less, and further preferably 100 sec / 100cc or less. When the gel value difference is 300 sec / 100cc or less, the adhesive porous layer is not so dense and ion permeability is maintained favorably, and excellent battery characteristics are obtained. On the other hand, the gel value difference is preferably 0 sec / 100cc or more, and 10 sec / 100 cc or more is preferable from the viewpoint of enhancing the adhesive force between the adhesive porous layer and the porous substrate.

The membrane resistance of the separator of the present disclosure is preferably 1 ohm · cm 2 to 10 ohm · cm 2 from the viewpoint of the 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 is measured at a temperature of 20 캜 using a mixed solvent of 1 mol / L LiBF ₄ -propylene carbonate: ethylene carbonate (1: 1 by mass ratio) as an electrolytic solution, Value.

The protruding strength of the separator of the present disclosure is preferably 200 g to 1000 g, more preferably 250 g to 600 g. The method of measuring the protruding strength of the separator is the same as the method of measuring the protruding strength of the porous substrate.

The heat shrinkage rate of the separator of the present disclosure at 120 캜 is preferably 10% or less in both the MD and TD directions from the viewpoint of balance between the shape stability and the shutdown property.

The curvature ratio of the separator of the present disclosure is preferably 1.5 to 2.5 from the viewpoint of ion permeability.

The moisture content (on a mass basis) contained in the separator of the present disclosure is preferably 1000 ppm or less. The smaller the moisture content of the separator is, the more the reaction between the electrolyte solution and water can be suppressed in the case of constituting the battery, the generation of gas in the battery can be suppressed, and the cycle characteristics of the battery are improved. From this viewpoint, the amount of water contained in the separator of the present disclosure is more preferably 800 ppm or less, and more preferably 500 ppm or less.

[Manufacturing method of separator for non-aqueous secondary battery]

The separator of the present disclosure can be obtained by, for example, applying a coating liquid containing a polyvinylidene fluoride resin onto a porous substrate to form a coating layer, and then solidifying the polyvinylidene fluoride resin contained in the coating layer To form an adhesive porous layer on the porous substrate. Specifically, the adhesive porous layer can be formed by, for example, the following wet coating method.

The wet coating method includes a coating liquid preparation process for preparing a coating liquid by dissolving or dispersing a polyvinylidene fluoride resin in a solvent, (ii) a coating process for forming a coating layer on a porous substrate, , (iii) a solidifying step of bringing the coating layer into contact with a coagulating solution to solidify the polyvinylidene fluoride resin while inducing phase separation to obtain a composite membrane having an adhesive porous layer on the porous substrate, (iv) , And (v) a drying process for removing water from the composite membrane. Details of the wet coating method for the separator of the present disclosure are as follows.

Examples of the solvent for dissolving or dispersing the polyvinylidene fluoride resin (hereinafter also referred to as "good solvent") used for preparing the coating liquid include N-methyl-2-pyrrolidone (NMP), dimethyl A polar amide solvent such as acetamide (DMAc), dimethylformamide, dimethylformamide and the like is suitably used.

From the viewpoint of forming an adhesive porous layer having a good porous structure, it is preferable to mix a phase separating agent that induces phase separation in a good solvent. Examples of the phase-separating agent include water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, and tripropylene glycol (TPG). It is preferable that the phase-separating agent is mixed with a good solvent within a range in which a suitable viscosity can be ensured for the coating.

As the solvent used for preparing the coating liquid, a mixed solvent containing 60% by mass or more of a good solvent and 5% by mass to 40% by mass of a phase-separating agent is preferable from the viewpoint of forming an adhesive porous layer having a good porous structure .

Conventionally, as a coating liquid for forming an adhesive porous layer, a coating liquid prepared by dissolving a polyvinylidene fluoride resin in a mixed solvent of a good solvent such as DMAc or NMP and a poor solvent such as water or TPG (poor solvent) do.

However, the coating liquid containing a poor solvent is easily gelled even in accordance with the environmental conditions after preparation, and in the case of gelling, an adhesive porous layer having a developed fine porous structure can not be formed, There is a possibility that this occurs or may occur. Since the porous structure and the surface morphology of the adhesive porous layer affect the adhesion to the electrode and the cell characteristics, storage stability is required for the coating liquid.

In the present embodiment, the binder resin contained in the coating liquid for forming the adhesive porous layer is substantially only a specific VDF-HFP binary copolymer. By this, although the detailed mechanism is unclear, the storage stability of the coating liquid is high, and gelation is difficult. Therefore, even if a coating solution is used instead of immediately after preparation, a fine porous structure is developed, and a good adhesion porous layer of a surface morphology is formed, and the cycle characteristics and load characteristics of the battery are excellent.

The concentration of the polyvinylidene fluoride resin of the coating liquid is preferably 3% by mass to 10% by mass of the total mass of the coating liquid from the viewpoint of forming an adhesive porous layer having a good porous structure.

When a filler or other component is contained in the adhesive porous layer, the filler and other components may be dissolved or dispersed in the coating solution.

The coating liquid may contain a dispersing agent such as a surfactant, a wetting agent, a defoaming agent, a pH adjusting agent and the like. These additives may remain in the adhesive porous layer as long as they are electrochemically stable in the use range of the non-aqueous secondary battery and do not inhibit the reaction in the battery.

The coagulating solution is generally composed of a positive 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 content of the coagulating liquid is preferably 40% by mass to 90% by mass from the viewpoint of formation of the porous structure and productivity.

The application of the coating liquid to the porous substrate may be performed by a conventional coating method using a Meyer bar, a die coater, a reverse roll coater, a gravure coater, or the like. When the adhesive 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 adhesive porous layer can be produced by a dry coating method in addition to the wet coating method described above. The dry coating method is a method in which a porous base material is coated with a coating liquid containing a polyvinylidene fluoride resin and a solvent, and the coating layer is dried to volatilize the solvent to obtain an adhesive porous layer. However, since the dry coating method tends to make the coating layer more dense than the wet coating method, the wet coating method is preferable because a good porous structure can be obtained.

The separator of the present disclosure can also be produced by a method in which the adhesive porous layer is formed as an independent sheet, the adhesive porous layer is overlapped on the porous substrate, and thermocompression bonding or composite formation is performed with an adhesive. As a method for producing the adhesive porous layer as an independent sheet, there is a method of forming the adhesive porous layer on the release sheet by applying the wet coating method or the dry coating method described above.

&Lt; Non-aqueous secondary battery &

The non-aqueous secondary battery of the present disclosure is a non-aqueous secondary battery that obtains electromotive force by doping and dedoping lithium, and includes a positive electrode, a negative electrode, and a separator of the present disclosure. Doping refers to a 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, held, or inserted.

The non-aqueous secondary battery of the present disclosure has, for example, a structure in which a battery element in which a cathode and an anode are opposed to each other with a separator interposed is sealed (enclosed) together with an electrolyte in a casing. The nonaqueous secondary battery of the present disclosure is especially suitable for a lithium ion secondary battery. The non-aqueous secondary battery of the present disclosure can be efficiently produced by using the separator of the present disclosure, which is excellent in adhesion to an electrode.

The non-aqueous secondary battery of the present disclosure has excellent cell strength by having the separator of the present disclosure excellent in adhesion to an electrode.

In addition, the non-aqueous secondary battery of the present disclosure is excellent in cycle characteristics by having the separator of the present disclosure which is excellent in the uniformity of the porous structure of the adhesive porous layer and excellent in adhesion to the electrode.

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

The anode may have a structure in which the active material layer containing the positive electrode active material and the binder resin is molded on the current collector. The active material layer may further contain 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 there may be mentioned _{2 O 4, LiFePO 4, LiCo} 1/2 Ni 1/2 O 2, LiAl 1/4 Ni 3/4 O 2 or the like. 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.

According to one embodiment of the separator of the present disclosure, since the adhesive porous layer is excellent in oxidation resistance, the adhesive porous layer is disposed on the anode side of the non-aqueous secondary battery so that the cathode active material can be operated at a high voltage of 4.2 V or higher applying the _{LiMn 1/2 Ni 1/2} O 2, LiCo 1/3 Mn 1/3 Ni 1/3 O 2 , etc. is easy.

The negative electrode may have a structure in which an active material layer containing a negative electrode active material and a binder resin is molded on a current collector. The active material layer may further contain a conductive auxiliary agent. Examples of the negative electrode active material include a material capable of electrochemically storing lithium, and specifically, for example, a carbon material; Silicon, tin, aluminum, etc., and an alloy of lithium and the like. Examples of the binder resin include polyvinylidene fluoride resin and styrene-butadiene copolymer. 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.

By applying the separator of the present disclosure, the nonaqueous secondary battery of the present disclosure can be applied not only to a negative electrode using a solvent binder (specifically, polyvinylidene fluoride resin), but also to an aqueous binder (specifically, a styrene-butadiene copolymer ) Is also excellent in adhesion to a negative electrode.

From the viewpoint of adhesion with the separator, the electrode preferably contains a large amount of binder resin in the active material layer. On the other hand, from the viewpoint of increasing the energy density of the battery, it is preferable that the active material layer contains a large amount of active material, and that the amount of the binder resin is relatively small. Since the separator of the present disclosure has excellent adhesion with the electrode, it is possible to reduce the binder resin amount of the active material layer and to increase the amount of active material, thereby increasing the energy density of the battery.

The electrolytic solution is a solution in which a lithium salt is dissolved in a non-aqueous solvent. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , and the like. Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, and vinylene carbonate; Chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and fluorine substituents thereof; cyclic esters such as? -butyrolactone,? -valerolactone, and the like, and these may be used alone or in combination. As the electrolytic solution, a cyclic carbonate and a chain carbonate are mixed in a mass ratio (cyclic carbonate: chain carbonate) of 20:80 to 40:60 and the lithium salt is dissolved in an amount of 0.5 mol / L to 1.5 mol / L.

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

In the non-aqueous secondary battery of the present disclosure, after a laminate in which the separator of the present disclosure is disposed between an anode and a cathode is manufactured, the laminate may be used to form a laminate having any one of the following 1) and 2) . &Lt; / RTI &gt;

1) A laminate is placed in a casing (for example, a pack made of an aluminum laminate film, the same shall apply hereinafter), an electrolytic solution is injected into the casing, a laminate is heated from the top of the casing by a hot press (wet heat press) And sealing of the exterior material.

2) The stacked body is subjected to a hot press (dry heat press) to bond the electrode and the separator, and then the envelope is accommodated in the envelope, the electrolyte is injected into the envelope, and the stack is further subjected to hot press , Adhesion between the electrode and the separator, and sealing of the casing.

According to the production method of 1) above, the laminate is thermally pressed in a state in which the specific VDF-HFP binary copolymer contained in the adhesive porous layer of the separator is swollen in the electrolyte, so that the electrode and the separator are adhered well, This excellent non-aqueous secondary battery can be obtained.

According to the production method of 2) above, since the electrode and the separator are adhered to each other before the laminate is housed in the casing, deformation of the laminate that occurs during transportation for accommodating the casing is suppressed.

Further, according to the production method of the above 2), since the laminate is thermally pressed further in a state in which the specific VDF-HFP binary copolymer contained in the adhesive porous layer of the separator is swollen in the electrolyte, adhesion between the electrode and the separator becomes stronger It becomes.

The wet heat press in the production method of the above 2) is only required to be a mild condition to restore adhesion between the electrode and the separator which is slightly weakened by the impregnation of the electrolyte, that is, the temperature of the wet heat press is set to a relatively low temperature The generation of gas due to the decomposition of the electrolytic solution and the electrolyte in the battery during the production of the battery is suppressed.

As the conditions of the hot press in the above production methods 1) and 2), in the wet heat press, the press pressure is preferably 0.5 MPa to 2 MPa, and the temperature is preferably 70 to 110 캜. In the dry heat press, the press pressure is preferably 0.5 MPa to 5 MPa, and the temperature is preferably 20 ° C to 100 ° C.

The separator of the present disclosure can be bonded by overlapping with the electrode. Therefore, in the production of a battery, the pressing is not an essential step, but from the viewpoint of making the adhesion between the electrode and the separator stronger, it is preferable to carry out the pressing. From the viewpoint of further strengthening the adhesion between the electrode and the separator, the press is preferably pressed (hot pressed) while being heated.

The method of disposing the separator between the positive electrode and the negative electrode at the time of producing the laminate may be a method of stacking the positive electrode, the separator and the negative electrode at least one layer in this order (so-called stacking method) , And the separator may be overlapped in this order and wound in the longitudinal direction.

(Example)

Hereinafter, the separator and the non-aqueous secondary battery of the present disclosure will be described in more detail by way of examples. However, the separator and the non-aqueous secondary battery of the present disclosure are not limited to the following examples.

&Lt; Measurement method and evaluation method >

The measuring method and evaluation method applied to the examples and comparative examples are as follows.

[Ratio of HFP unit of polyvinylidene fluoride resin]

The ratio of HFP units of the polyvinylidene fluoride resin was determined from the NMR spectrum. Specifically, 20 mg of a polyvinylidene fluoride resin was dissolved in 0.6 mL of an internal dimethyl sulfoxide at 100 占 폚, and a ¹⁹ F-NMR spectrum was measured at 100 占 폚.

[Weight average molecular weight of polyvinylidene fluoride resin]

The weight average molecular weight (Mw) of the polyvinylidene fluoride resin was measured by gel permeation chromatography (GPC). The molecular weight by GPC was measured by using a GPC apparatus "GPC-900" manufactured by Nihon Bunkyo Co., Ltd., using two TSCOgel SUPER AWM-H columns as a column, using dimethylformamide as a solvent, And a flow rate of 10 mL / min to obtain a molecular weight in terms of polystyrene.

[Coating amount of adhesive porous layer]

The separator was cut into 10 cm x 10 cm, the mass was measured, and the mass was divided by the area to obtain the basis weight of the separator. Further, the porous substrate used for the production of the separator was cut into 10 cm x 10 cm, and the mass was measured. The mass was divided by the area to obtain the basis weight of the porous substrate. By subtracting the basis weight of the porous substrate from the basis weight of the separator, the total coating amount on both sides of the adhesive porous layer was determined.

[Thickness]

The thicknesses of the porous substrate and the separator were measured using a contact type thickness meter (LITEMATIC manufactured by Mitutoyo Co., Ltd.). The measurement terminal was a cylindrical one having a diameter of 5 mm, and was adjusted so that a load of 7 g was applied during measurement, and arbitrary 20 points within 10 cm x 10 cm were measured and the average value thereof was calculated.

The layer thickness of the adhesive porous layer was obtained by subtracting the film thickness of the porous substrate from the film thickness of the separator.

[Public rate]

The porosity of the porous substrate and the separator was determined according to the following calculation method.

The constituent materials are a, b, c, ... , n, and the mass of each constituent material is Wa, Wb, Wc, ... , Wn (g / cm2), and the true density of each constituent material is da, db, dc, ... , dn (g / cm3) and the film thickness is t (cm), the porosity? (%) is obtained from the following equation.

? = {1- (Wa / da + Wb / db + Wc / dc + ... + Wn / dn) / t}

[Gully Value]

The gluing value of the porous substrate and the separator was measured by a gel permeation densometer (G-B2C, manufactured by Toyo Seiki Co., Ltd.) according to JIS P8117: 2009.

[Heat resistance]

The separator was placed on a horizontal stand, and the soldering iron having a tip diameter of 2 mm was heated to bring the tip of the soldering iron to the surface of the separator for 60 seconds while the tip temperature was kept at 260 占 폚. The area of the hole (mm 2) was measured. The higher the heat resistance of the separator, the smaller the area of the holes generated in the separator.

[Wet adhesion with electrodes]

91 g of lithium cobaltate powder as a positive electrode active material, 3 g of acetylene black as a conductive additive, and 3 g of polyvinylidene fluoride as a binder were dissolved in N-methyl-pyrrolidone so that the concentration of vinylidene fluoride was 5% by mass, And the mixture was stirred with a complete mixer to prepare a slurry for a positive electrode. The positive electrode slurry was applied to one surface of an aluminum foil having a thickness of 20 占 퐉, dried and pressed to obtain a positive electrode (single-side coating) having a positive electrode active material layer as an electrode for evaluation of wet adhesion between the separator and the electrode.

The electrode and the aluminum foil (thickness: 20 mu m) obtained above were cut into 1.5 cm wide and 7 cm long, respectively, and the separators obtained in the following Examples and Comparative Examples were cut into 1.8 cm wide and 7.5 cm long. (1 mol / L LiBF ₄ - ethylene carbonate: propylene carbonate [mass ratio 1: 1]) was impregnated into the laminate, and the laminate was laminated in an aluminum laminate film pack And vacuum-sealed using a vacuum sealer. Next, the laminate was hot-pressed using a hot press machine to form a pack, and the electrode and the separator were bonded. The conditions of the hot press were a pressure of 1 MPa, a temperature of 90 DEG C, and a pressing time of 2 minutes. Thereafter, the pack was opened to take out the laminate, and the aluminum foil was removed from the laminate.

The martensitic surface of the electrode of the measurement sample was fixed to the metal plate with double-sided tape, and the metal plate was fixed to the lower chuck of Tensilon (A &amp; Digest STB-1225S). At this time, the metal plate was fixed to the tensile column so that the longitudinal direction of the measurement specimen was the gravity direction. The separator was peeled from the electrode about 2 cm from the lower end, and the end of the separator was fixed to the upper chuck so that the tensile angle (angle of the separator relative to the sample to be measured) was 180 °. The separator was pulled at a tensile speed of 20 mm / min to measure the load when the separator peeled from the electrode. The load from 10 mm to 40 mm was measured at intervals of 0.4 mm. This measurement was carried out three times, and the average was calculated to be the wet adhesion force (N / 15 mm, adhesion force between the electrode and the separator by wet heat press) with the electrode.

[Amount of gas generation]

The separator was cut into a size of 600 cm &lt; 2 &gt; and placed in a pack made of an aluminum laminate film. An electrolytic solution was injected into the pack to impregnate the separator with an electrolytic solution, and the pack was sealed to obtain a test cell. As the electrolytic solution, 1 mol / L LiPF ₆ - ethylene carbonate: ethyl methyl carbonate (mass ratio 3: 7) was used. The test cell was placed under an environment of 85 캜 for 3 days, and the volume of the test cell before and after the heat treatment was measured. The gas generation amount V (= V2-V1, unit: ml) was obtained by subtracting the volume V1 of the test cell before the heat treatment from the volume V2 of the test cell after the heat treatment.

[Cell Strength]

91 g of lithium cobaltate powder as a positive electrode active material, 3 g of acetylene black as a conductive additive, and 3 g of polyvinylidene fluoride as a binder were dissolved in N-methyl-pyrrolidone so that the concentration of vinylidene fluoride was 5% by mass, And the mixture was stirred with a complete mixer to prepare a slurry for a positive electrode. The slurry for the positive electrode was applied to an aluminum foil having a thickness of 20 mu m, followed by drying and pressing to obtain a positive electrode having a positive electrode active material layer.

300 g of artificial graphite as a negative electrode active material, 7.5 g of a water-soluble dispersion containing 40% by mass of a modified styrene-butadiene copolymer as a binder, 3 g of carboxymethylcellulose as a thickener and an appropriate amount of water were mixed and mixed by a twin- Was prepared. The slurry for the negative electrode was applied to a copper foil having a thickness of 10 mu m as an anode current collector, followed by drying and pressing to obtain a negative electrode having a negative electrode active material layer.

The positive electrode and the negative electrode were wound with each other through the separators obtained in the following examples and comparative examples, and the lead tabs were welded to obtain a battery element. This battery element was housed in a pack made of an aluminum laminated film and impregnated with an electrolytic solution and then subjected to a hot press (wet heat press) at a pressure of 1 MPa and a temperature of 90 캜 for 2 minutes, 65 mm, width 35 mm, thickness 2.5 mm, capacity 700 mAh). As the electrolytic solution, 1 mol / L LiPF ₆ -ethylene carbonate: diethyl carbonate (weight ratio 3: 7) was used.

The test secondary battery obtained above was subjected to a three-point bending test in accordance with ISO178 to determine the cell strength (N).

[Cycle characteristics]

A test secondary battery was produced by the same manufacturing method as described above. Discharge cycle of 300 cycles under the condition of 4.2 V constant-current constant-voltage charge at 1 C for 2 hours and constant-current discharge at 3 V cut-off at 1 C under an environment of 25 캜. The ratio of the discharge capacity obtained after 300 cycles based on the discharge capacity obtained in the first cycle was determined as a percentage and used as an index of the cycle characteristics.

&Lt; Preparation of separator &

[Example 1]

VDF-HFP binary copolymer (ratio of HFP units: 5.1 mass%, weight average molecular weight: 1,130,000) was dissolved in a mixed solvent of dimethylacetamide and tripropylene glycol (dimethylacetamide: tripropylene glycol = 80: 20 [mass ratio]) to prepare a coating liquid for forming an adhesive porous film. This coating solution was applied on both surfaces of a polyethylene microporous membrane (film thickness 9 占 퐉, porosity of 38%, gull value of 160 sec / 100 cc), and a coagulating solution (water: dimethylacetamide: tripropylene glycol = 62: 30: [Mass ratio], temperature: 40 占 폚) to solidify. Next, this was washed with water and dried to obtain a separator in which an adhesive porous layer was formed on both surfaces of a polyethylene microporous membrane.

[Examples 2 to 5]

A separator in which an adhesive porous layer was formed on both surfaces of a polyethylene microporous membrane was prepared in the same manner as in Example 1 except that the VDF-HFP binary copolymer was changed to another VDF-HFP binary copolymer shown in Table 1. [

[Example 6]

The VDF-HFP binary copolymer was mixed with the first VDF-HFP binary copolymer (ratio of HFP units: 5.4 mass%, weight average molecular weight: 11.3 million) and the second VDF-HFP binary copolymer (HFP units: 2.5 mass% A weight average molecular weight of 1,500,000) (mass ratio of 99: 1), a separator in which an adhesive porous layer was formed on both surfaces of a polyethylene microporous membrane was prepared.

[Comparative Example 1]

A separator having an adhesive porous layer formed on both surfaces of a polyethylene microporous membrane was produced in the same manner as in Example 6 except that the mixing ratio of the first VDF-HFP binary copolymer and the second VDF-HFP binary copolymer was changed to 90:10 did.

[Comparative Examples 2 to 4]

A separator in which an adhesive porous layer was formed on both surfaces of a polyethylene microporous membrane was prepared in the same manner as in Example 1 except that the VDF-HFP binary copolymer was changed to another VDF-HFP binary copolymer shown in Table 1. [

[Comparative Example 5]

The VDF-HFP binary copolymer was changed to another VDF-HFP binary copolymer (ratio of HFP units: 5.4 mass%, weight average molecular weight: 3,1 million), and an adhesive porous layer was formed on both surfaces of the polyethylene microporous membrane in the same manner as in Example 1 However, the viscosity of the coating liquid was too high, and the adhesive porous layer could not be formed.

[Comparative Example 6]

VDF-HFP binary copolymer was changed to vinylidene fluoride-hexafluoropropylene-chlorotrifluoroethylene terpolymer (ratio of HFP unit: 5.2 mass%, ratio of CTFE unit: 3.8 mass%, weight average molecular weight: 600,000) A separator in which an adhesive porous layer was formed on both surfaces of a polyethylene microporous membrane was produced in the same manner as in Example 1 except for the above.

[Examples 7 to 13]

Magnesium hydroxide (KUWA KAGAKU KOGYO CHEMICAL CO., LTD. 5P, average primary particle diameter 0.8 μm, BET specific surface area 6.8 m 2 / g) as an inorganic filler was added to the coating solution in which the resin was dissolved, ), And the mixture was stirred until it became homogeneous to prepare a coating liquid. In the same manner as in Example 5 except that the coating amount of the coating liquid was changed as shown in Table 1, adhesion to both surfaces of the polyethylene microporous film A separator having a porous layer formed thereon was produced.

[Example 14]

A separator in which an adhesive porous layer was formed on both surfaces of a polyethylene microporous membrane was prepared in the same manner as in Example 5 except that the coating amount of the coating liquid was changed as shown in Table 1. [

[Example 15]

The inorganic filler was mixed with two kinds of magnesium hydroxide (magnesium hydroxide: alumina = 95: 5 [volume ratio]), magnesium hydroxide (Kyohei Kagakugo Seisakushima 5P) and alumina (Showa Denkusha AL-160SG- ), A separator in which an adhesive porous layer was formed on both surfaces of a polyethylene microporous membrane was produced in the same manner as in Example 11. [

[Example 16]

A separator in which an adhesive porous layer was formed on both surfaces of a polyethylene microporous membrane was produced in the same manner as in Example 11 except that the inorganic filler was changed to magnesium oxide (PUREMAG FNM-G manufactured by Datafugar Chemical Industries, Ltd., average primary particle size: 0.5 mu m) .

[Example 17]

A separator in which an adhesive porous layer was formed on both surfaces of a polyethylene microporous membrane was produced in the same manner as in Example 11 except that the inorganic filler was changed to alumina (AL-160SG-3 manufactured by Showa Denkusha Co., Ltd., average primary particle size: 0.5 탆).

[Example 18]

A separator in which an adhesive porous layer was formed on both surfaces of a polyethylene microporous membrane was produced in the same manner as in Example 11 except that the VDF-HFP binary copolymer was changed to another VDF-HFP binary copolymer shown in Table 1.

Table 1 shows physical properties and evaluation results of the separators of Examples 1 to 18 and Comparative Examples 1 to 6.

[Table 1]

The disclosure of Japanese Patent Application No. 2015-221570, filed on November 11, 2015, is incorporated herein by reference in its entirety. The disclosure of Japanese Patent Application No. 2015-221600 filed on November 11, 2015 is incorporated herein by reference in its entirety.

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

Claims (7)

A porous substrate,
Wherein the adhesive porous layer provided on one side or both sides of the porous substrate has a ratio of hexafluoropropylene monomer units of 5.1 mass% or more and 6.9 mass% or less, and a weight average molecular weight of vinylidene fluoride-hexafluoro Propylene binary copolymer and the vinylidene fluoride-hexafluoropropylene binary copolymer accounts for not less than 95% by mass of the whole resin,
And a separator for a non-aqueous secondary battery. The method according to claim 1,
Wherein the thickness of the one surface of the adhesive porous layer is 0.5 占 퐉 or more and 5 占 퐉 or less. 3. The method according to claim 1 or 2,
Wherein the adhesive porous layer further contains an inorganic filler. The method of claim 3,
Wherein the inorganic filler is at least one selected from metal hydroxides and metal oxides. The method of claim 3,
Wherein the inorganic filler is at least one of magnesium hydroxide and magnesium oxide. 6. The method according to any one of claims 3 to 5,
Wherein the content of the inorganic filler in the adhesive porous layer is not less than 40% by volume and not more than 85% by volume of the entire solid content of the adhesive porous layer. A nonaqueous secondary battery separator according to any one of claims 1 to 6, which is disposed between the positive electrode and the negative electrode, comprising a positive electrode, a negative electrode, and a nonaqueous secondary battery separator for separating lithium, Aqueous secondary battery.