JP2017066356A - Porous layer, laminated body, member for nonaqueous electrolyte secondary battery including porous layer, and nonaqueous electrolyte secondary battery including porous layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous layer that can be used as a member for a nonaqueous secondary battery having better shutdown characteristics.SOLUTION: A porous layer includes a polyvinylidene fluoride-based resin, where, assuming that the sum of contents of a crystal form α and a crystal form β in the polyvinylidene fluoride-based resin is 100 mol%, the content of crystal form α is 10 mol% or more and 65 mol% or less.SELECTED DRAWING: None

Description

  The present invention relates to a porous layer, a laminate, a non-aqueous electrolyte secondary battery member including a porous layer, and a non-aqueous electrolyte secondary battery including a porous layer.

  Non-aqueous electrolyte secondary batteries such as lithium secondary batteries (hereinafter also referred to as “non-aqueous secondary batteries”) are currently widely used as batteries for devices such as personal computers, mobile phones, and portable information terminals. Yes.

  Devices equipped with lithium-ion batteries are equipped with various types of electrical protection circuits in chargers and battery packs, and measures are taken to make the batteries operate normally and safely. If the lithium ion battery continues to be charged, redox decomposition of the electrolyte solution on the positive and negative electrode surfaces accompanied by heat generation, oxygen release due to decomposition of the positive electrode active material, and precipitation of metallic lithium at the negative electrode will eventually occur. There is a danger of causing the battery to ignite or explode due to a runaway condition.

  In order to safely stop the battery before reaching such a dangerous thermal runaway state, most current lithium ion batteries have a porous substrate at about 130 ° C to 140 ° C when the internal temperature of the battery rises due to some malfunction. A porous base material mainly composed of polyolefin having a shutdown function in which open pores are blocked is used as a separator. By exhibiting this function when the battery internal temperature rises, ions that permeate the separator can be blocked and the battery can be safely stopped.

  On the other hand, since the porous substrate mainly composed of polyolefin has poor adhesion to the electrode, it may cause a decrease in battery capacity and cycle characteristics, and the adhesion of the porous substrate to the electrode. In order to improve the above, development of a separator in which a porous layer containing a polyvinylidene fluoride-based resin is laminated on at least one surface of the porous substrate has been underway.

  For example, in Patent Document 1, in consideration of adhesive strength with an electrode and ion permeability, the porosity of a porous layer containing a polyvinylidene fluoride resin is 30% to 60%, and the average pore diameter is 1 nm to It is shown to be 100 nm.

Japanese Patent No. 5432417

  However, the above-described conventional separator for a non-aqueous secondary battery having a porous layer has room for improvement in the shutdown function (shutdown characteristics).

The present inventor paid attention to the crystalline form of the polyvinylidene fluoride resin in the porous layer containing the polyvinylidene fluoride resin that constitutes the separator for non-aqueous secondary batteries, in particular, non-aqueous secondary batteries. By setting the proportion of α-type crystals and β-type crystals in the vinylidene fluoride resin within a specific range, the porous layer can be used as a member constituting a separator for a non-aqueous secondary battery having excellent shutdown characteristics. The headline and the present invention were conceived.

  In order to solve the above problems, the porous layer according to the present invention is a porous layer containing a polyvinylidene fluoride resin, and contains α-type crystals and β-type crystals in the polyvinylidene fluoride resin. When the total amount is 100 mol%, the content of the α-type crystal is 10 mol% or more and 65 mol% or less.

  Here, the content of α-type crystals is calculated from the absorption intensity around 765 nm in the IR spectrum of the porous layer, and the content of β-type crystals is calculated from the absorption intensity around 840 nm in the IR spectrum of the porous layer. Calculated.

  In the porous layer according to the present invention, the polyvinylidene fluoride resin is a homopolymer of vinylidene fluoride and / or vinylidene fluoride and hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, trichloroethylene, and fluorine. A copolymer with at least one monomer selected from the group consisting of vinyl chloride is preferred. The polyvinylidene fluoride resin preferably has a weight average molecular weight of 300,000 to 3,000,000.

  The porous layer according to the present invention preferably contains 1% by mass or more and 30% by mass or less filler based on the weight of the entire porous layer. Moreover, it is preferable that the volume average particle diameter of the said filler is 0.01 micrometer or more and 10 micrometers or less.

  In addition, the laminate according to the present invention includes a porous substrate mainly composed of a polyolefin-based resin, and a porous layer according to the present invention laminated on at least one surface of the porous substrate. It is characterized by.

  Further, the separator for a non-aqueous electrolyte secondary battery according to the present invention is a porous substrate mainly composed of a polyolefin resin, and is laminated on at least one surface of the porous substrate. And a porous layer.

  The nonaqueous electrolyte secondary battery member according to the present invention is characterized in that the positive electrode, the porous layer according to the present invention, and the negative electrode are arranged in this order.

  Furthermore, the nonaqueous electrolyte secondary battery according to the present invention includes the porous layer according to the present invention.

  The porous layer which concerns on this invention has an effect that it can be utilized suitably as a member which comprises the separator for non-aqueous secondary batteries which is excellent in a shutdown characteristic. Moreover, the laminated body which concerns on this invention has the effect that it can utilize suitably as a separator for non-aqueous secondary batteries which is excellent in a shutdown characteristic including the said porous layer. Furthermore, the non-aqueous secondary battery separator, the non-aqueous electrolyte secondary battery member and the non-aqueous electrolyte secondary battery according to the present invention also include the porous layer and have an effect of providing a shutdown function. .

An embodiment of the present invention will be described below, but the present invention is not limited to this. The present invention is not limited to each configuration described below, and various modifications are possible within the scope shown in the claims, and various technical means disclosed in different embodiments are appropriately combined. The obtained embodiments are also included in the technical scope of the present invention. Unless otherwise specified in this specification, “A to B” indicating a numerical range means “A or more and B or less”.

[Embodiment 1: Porous layer]
In order to solve the above problems, the porous layer according to Embodiment 1 of the present invention is a porous layer containing a polyvinylidene fluoride resin, and the α-type crystal and β in the polyvinylidene fluoride resin When the total content of type crystals is 100 mol%, the content of the α-type crystals is 10 mol% or more and 65 mol% or less.

  Here, the content of α-type crystals is calculated from the absorption intensity around 765 nm in the IR spectrum of the porous layer, and the content of β-type crystals is calculated from the absorption intensity around 840 nm in the IR spectrum of the porous layer. Calculated.

  The porous layer according to the present invention contains a polyvinylidene fluoride resin (PVDF resin). The porous layer has a structure in which a large number of pores are formed inside and these pores are connected to each other, and a gas or liquid can pass from one surface to the other surface. Moreover, when the porous layer which concerns on this embodiment is used as a member which comprises the separator for nonaqueous secondary batteries, the said porous layer turns into a layer which can adhere | attach with an electrode as the outermost layer of the said separator.

  The content of the PVDF resin in the porous layer according to the present invention is 10% by mass or more, preferably 30% by mass or more, more preferably 50% by mass or more with respect to the mass of the porous layer ( The upper limit is 100% by mass).

  Examples of PVDF resins include homopolymers of vinylidene fluoride (ie, polyvinylidene fluoride); copolymers of vinylidene fluoride and other copolymerizable monomers (polyvinylidene fluoride copolymer); and mixtures thereof ; Examples of the monomer copolymerizable with vinylidene fluoride include hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, trichloroethylene, vinyl fluoride and the like, and one kind or two or more kinds can be used. The PVDF resin can be synthesized by emulsion polymerization or suspension polymerization.

  The PVDF resin contains 85 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, and still more preferably 98 mol% or more of vinylidene fluoride as a structural unit. When 85 mol% or more of vinylidene fluoride is contained, it is easy to ensure mechanical strength and heat resistance that can withstand pressurization and heating during battery production.

Moreover, the aspect in which a porous layer contains 2 types of PVDF-type resin (the following 1st resin and 2nd resin below) from which the content of hexafluoropropylene mutually differs is also preferable, for example.
First resin: A vinylidene fluoride / hexafluoropropylene copolymer or a vinylidene fluoride homopolymer (hexafluoropropylene copolymer) having a hexafluoropropylene content exceeding 0 mol% and not more than 1.5 mol% Content is 0 mol%).
Second resin: a vinylidene fluoride / hexafluoropropylene copolymer having a hexafluoropropylene content exceeding 1.5 mol%.

  The porous layer containing the two types of PVDF-based resins has improved adhesion to the electrode as compared with a porous layer not containing any one of them. Further, the porous layer containing the two types of PVDF-based resins is different from the porous layer not containing any one of the other layers (for example, a porous base material) constituting the separator for a non-aqueous secondary battery. Adhesion with the layer) is improved, and the peeling force between these layers is improved. The mixing ratio (mass ratio, first resin: second resin) of the first resin and the second resin is preferably in the range of 15:85 to 85:15.

  The PVDF resin preferably has a weight average molecular weight in the range of 300,000 to 3,000,000. When the weight average molecular weight is 300,000 or more, the mechanical properties that the porous layer can withstand the adhesion treatment with the electrode can be secured, and sufficient adhesion can be obtained. On the other hand, when the weight average molecular weight is 3 million or less, the viscosity of the coating liquid at the time of coating molding does not become too high and the moldability is excellent. The weight average molecular weight is more preferably in the range of 300,000 to 2,000,000, still more preferably in the range of 500,000 to 1,500,000.

  The fibril diameter of the PVDF-based resin is preferably in the range of 10 nm to 1000 nm from the viewpoint of cycle characteristics of the nonaqueous secondary battery including the porous layer.

  The porous layer according to the present invention may contain a resin other than the PVDF resin. Examples of other resins include styrene-butadiene copolymers; homopolymers or copolymers of vinyl nitriles such as acrylonitrile and methacrylonitrile; polyethers such as polyethylene oxide and polypropylene oxide;

  Furthermore, the porous layer according to the present invention may contain a filler made of an inorganic material or an organic material. By containing the filler, the slipperiness and heat resistance of the separator including the porous layer can be improved. As the filler, any of an organic filler and an inorganic filler which are stable in a non-aqueous electrolyte and electrochemically stable may be used. From the viewpoint of ensuring the safety of the battery, a filler having a heat resistant temperature of 150 ° C. or higher is preferable.

  Examples of the organic filler include cross-linked polymethacrylic acid esters such as cross-linked polyacrylic acid, cross-linked polyacrylic acid ester, cross-linked polymethacrylic acid, and cross-linked polymethyl methacrylate; cross-linked silicone, cross-linked polystyrene, cross-linked polydivinylbenzene, and styrene- Cross-linked polymer fine particles such as cross-linked divinylbenzene copolymer, polyimide, melamine resin, phenol resin, benzoguanamine-formaldehyde condensate; heat-resistant polymer fine particles such as polysulfone, polyacrylonitrile, polyaramid, polyacetal, thermoplastic polyimide; Can be mentioned.

  The resin (polymer) that constitutes the organic filler is a mixture of the molecular species exemplified above, a modified product, a derivative, a copolymer (random copolymer, alternating copolymer, block copolymer, graft copolymer), A crosslinked body may be sufficient.

  Examples of the inorganic filler include metal hydroxides such as aluminum hydroxide, magnesium hydroxide, calcium hydroxide, chromium hydroxide, zirconium hydroxide, nickel hydroxide, and boron hydroxide; metal oxides such as alumina and zirconia; Examples thereof include carbonates such as calcium carbonate and magnesium carbonate; sulfates such as barium sulfate and calcium sulfate; clay minerals such as calcium silicate and talc; From the viewpoint of imparting flame retardancy and charge removal effect, metal hydroxides are preferred.

  The said filler may be used individually by 1 type, may be used in combination of 2 or more types, or may be used in combination of an organic filler and an inorganic filler.

  The volume average particle diameter of the filler is preferably in the range of 0.01 μm to 10 μm from the viewpoint of ensuring good adhesiveness and slipperiness and moldability of the laminate. The lower limit is more preferably 0.1 μm or more, and the upper limit is more preferably 5 μm or less.

  The particle shape of the filler is arbitrary, and may be any of a spherical shape, an elliptical shape, a plate shape, a rod shape, and an indefinite shape. From the viewpoint of preventing a short circuit of the battery, plate-like particles and non-aggregated primary particles are preferable.

  The filler can improve slipperiness by forming fine irregularities on the surface of the porous layer. However, when the filler is a plate-like particle or non-aggregated primary particle, the filler is porous. The unevenness formed on the surface of the porous layer becomes finer, and the adhesion between the porous layer and the electrode becomes better.

  In the porous layer which concerns on this invention, it is preferable that the ratio of the filler to the total amount of PVDF-type resin and a filler is the range of 1 mass%-30 mass%. When the filler content is 1% by mass or more, fine irregularities are formed on the surface of the porous layer, and the effect of improving the slipperiness of the separator including the porous layer is easily exhibited. In this respect, the filler content is more preferably 3% by mass or more. On the other hand, when the content ratio of the filler is 30% by mass or less, the mechanical strength of the porous layer is maintained. For example, when the electrode and the separator including the porous layer are stacked and rolled, an electrode body is produced. The separator is unlikely to crack. In this respect, the filler content is more preferably 20% by mass or less, and further preferably 10% by mass or less.

  In the porous layer according to the present invention, when the separator is slit, the ratio of the filler to the total amount of the PVDF resin and the filler from the viewpoint of suppressing the occurrence of flaking or bending at the slit end face and the occurrence of slit waste. Is preferably 1% by mass or more, and more preferably 3% by mass or more.

  The average film thickness of the porous layer according to the present invention is preferably in the range of 0.5 μm to 10 μm on one side of the porous substrate from the viewpoint of ensuring adhesion with the electrode and high energy density. A range of 5 μm is more preferable.

  The porous layer according to the present invention preferably has a sufficiently porous structure from the viewpoint of ion permeability. Specifically, the porosity is preferably in the range of 30% to 60%. The porous layer according to the present invention preferably has an average pore diameter in the range of 20 nm to 100 nm.

  The surface roughness of the porous layer according to the present invention is ten-point average roughness (Rz), preferably in the range of 0.8 μm to 8.0 μm, more preferably in the range of 0.9 μm to 6.0 μm. The range of 0 μm to 3.0 μm is more preferable. Ten-point average roughness (Rz) is a value measured by a method according to JIS B 0601-1994 (or Rzjis of JIS B 0601-2001). Specifically, Rz is a value measured using a ET4000 manufactured by Kosaka Laboratories under the conditions of a measurement length of 1.25 mm, a measurement speed of 0.1 mm / second, and a temperature and humidity of 25 ° C./50% RH. It is.

  The dynamic friction coefficient of the porous layer according to the present invention is preferably 0.1 to 0.6, more preferably 0.1 to 0.4, and still more preferably 0.1 to 0.3. The dynamic friction coefficient is a value measured by a method according to JIS K 7125. Specifically, the dynamic friction coefficient in the present invention is a value measured using a surface property tester manufactured by Haydon.

<Crystal form of PVDF resin>
The PVDF resin can take three types of crystal forms, α-type, β-type, and γ-type. However, when the IR spectrum of the porous layer in the laminate of the present invention is measured, the following peaks characteristic of α-type crystals or β-type crystals can be observed, but peaks characteristic of γ-type crystals are Not observed. That is, almost all of the PVDF resins in the porous layer are α-type crystals or β-type crystals.

  In the PVDF resin contained in the porous layer according to the present invention, the content of α-type crystals when the total content of α-type crystals and β-type crystals is 100 mol% is 10 mol% or more and 65 mol % Or less, preferably 15 mol% or more, more preferably 20 mol% or more, and further preferably 25 mol% or more. Further, it is preferably 60 mol% or less, more preferably 55 mol% or less, and further preferably 45 mol% or less. In other words, it is preferably 10 mol% or more and 65 mol% or less, more preferably 15 mol% or more and 65 mol% or less, further preferably 20 mol% or more and 65 mol% or less, and further preferably 25 mol%. It is 65 mol% or less, More preferably, it is 25 mol% or more and 55 mol% or less, More preferably, it is 25 mol% or more and 45 mol% or less. When the content of the α-type crystal is in the above range, the porous layer can be used as a member constituting a non-aqueous secondary battery excellent in shutdown characteristics, particularly a non-aqueous secondary battery separator. Furthermore, when the content of the α-type crystal is in the above range, the porous layer is a member constituting a separator for a non-aqueous secondary battery excellent in battery storage stability, particularly a non-aqueous secondary battery. Can also be used.

  The reason why the porous layer of the present invention can be used as a member constituting a non-aqueous secondary battery having excellent shutdown characteristics is that a β-type crystal having a relatively low melting point and an α-type crystal having relatively high heat resistance It is conceivable that the β-type crystals fill the pores and the α-type crystals contribute to maintaining the shape of the separator.

  The reason why the porous layer of the present invention can be used as a member constituting a non-aqueous secondary battery excellent in battery storage stability is that a β-type crystal having relatively high deformability by force and a deformability by force are compared. The β-type crystal improves the followability of the separator including the porous layer when the electrode is expanded, and the α-type crystal contributes to maintaining the shape of the separator. Furthermore, it is considered that the porous layer can function well as an electrode protective film. When the electrode (particularly the positive electrode) is not sufficiently protected by the separator, the electrolytic solution is decomposed (particularly oxidatively decomposed) by the electrode, so that battery storage stability tends to decrease. In addition, since β-type crystals have a structure in which fluorine atoms are directed outward, a porous layer containing a large amount of β-type crystals tends to have high resistance (particularly oxidation resistance) to electrodes (particularly the positive electrode). Conceivable.

  The α-type crystal PVDF resin is a PVDF skeleton contained in a polymer constituting the PVDF resin, and a fluorine atom (or hydrogen atom) bonded to one main chain carbon atom in a molecular chain in the skeleton. A hydrogen atom (or fluorine atom) bonded to one adjacent carbon atom is present at the trans position, and a hydrogen atom (or fluorine atom) bonded to the carbon atom adjacent to the other (reverse side) is Gauche Exists at the position of (60 ° position), and two or more chains of the three-dimensional structure continue.

It is characterized in that the molecular chain is

The dipole efficiency of C—F ₂ and C—H ₂ bonds in the mold has components in a direction perpendicular to the molecular chain and in a direction parallel to the molecular chain.

PVDF resins α-type crystals, in the IR spectrum, 1212Cm around ^-1 has characteristic peaks (characteristic absorptions) around 1183 cm ^-1 and near 765Cm ^-1, in a powder X-ray diffraction analysis, 2 [Theta] = 17 It has characteristic peaks around 7 °, 18.3 ° and 19.9 °.

  The β-type crystal PVDF resin has a PVDF skeleton contained in a polymer constituting the PVDF resin, and fluorine atoms and hydrogen atoms bonded to a carbon atom adjacent to one main chain carbon of the molecular chain in the skeleton. Each is characterized in that a trans configuration (TT structure), that is, a fluorine atom and a hydrogen atom bonded to adjacent carbon atoms are present at a position of 180 ° when viewed from the direction of the carbon-carbon bond.

In the PVDF skeleton included in the polymer constituting the PVDF resin, the β-crystal PVDF resin may have a TT structure as a whole. Moreover, a part of the skeleton may have a TT structure, and at least four continuous PVDF monomer unit units may have a molecular chain of the TT structure. In any case, the carbon-carbon bond in which the TT-type structure portion constitutes the TT-type main chain has a planar zigzag structure, and the dipole efficiency of C—F ₂ and C—H ₂ bonds is perpendicular to the molecular chain. It has components in various directions.

PVDF resins β-type crystal, in the IR spectrum, 1274Cm around ^-1 has characteristic peaks (characteristic absorptions) around 1163Cm ^-1 and near 840 cm ^-1, in a powder X-ray diffraction analysis, 2 [Theta] = 21 It has a characteristic peak around °.

Note that the PVDF resin of γ-type crystal has a three-dimensional structure in which a TT type structure and a TG type structure are alternately and continuously formed in the PVDF skeleton contained in the polymer constituting the PVDF resin. In the IR spectrum, there are characteristic peaks (characteristic absorption) around 1235 cm ⁻¹ and 811 cm ⁻¹ , and there are characteristic peaks around 2θ = 18 ° in the powder X-ray diffraction analysis.

<Calculation method of α-type crystal and β-type crystal content in PVDF resin>
The contents of α-type crystals and β-type crystals in the PVDF resin can be calculated, for example, by the methods described in (i) to (iii) below.

(I) Formula Beer's law: A = εbC (1)
(In the formula, A is absorbance, ε is molar absorption constant, b is optical path length, and C is concentration)
In the above formula (1), the absorption of the characteristic absorption of the α-type crystal is A ^α , the absorption of the characteristic absorption of the β-type crystal is A ^β , the molar absorption constant of the PVDF resin of the α-type crystal is ε ^α , and Assuming that the molar extinction constant of PVDF resin is ε ^β , the concentration of PVDF resin of α-type crystal is C ^α , and the concentration of PVDF resin of β-type crystal is C ^β , the absorbance of each of α-type crystal and β-type crystal The percentage of
^{A β / A α = (ε} β / ε α) × (C β / C α) ... (1a)
It becomes.

Here, assuming that the correction coefficient (ε ^β / ε ^α ) of the molar absorption constant is E ^{β / α} , the content F (β) of the PVDF resin of the β-type crystal with respect to the sum of the α-type crystal and the β-type crystal = ( C ^β / (C ^α + C ^β )) is expressed by the following formula (2a).

F ([beta]) = {(1 / E [ ^{beta] / [alpha]} ) * (A [ ^alpha] / A [ ^beta] )} / {1+ (1 / E [ ^{beta] / [alpha]} ) * (A [ ^alpha] / A [ ^beta] )}.
= ^Aβ / {( ^{Eβ / α} × ^Aα ) + ^Aβ } (2a)
Therefore, if the correction coefficient E ^{β / α} is determined, the measured value of the absorption A ^α of the characteristic absorption of the α-type crystal and the value of the absorption A ^β of the characteristic absorption of the β-type crystal can be calculated with respect to the sum of the α-type crystal and the β-type crystal. The content F (β) of the PVDF resin of β-type crystal can be calculated. Further, the content F (α) of the PVDF resin of the α-type crystal with respect to the total of the α-type crystal and the β-type crystal can be calculated from the calculated F (β).

(Ii) Determination method of correction coefficient E ^{β / α} A PVDF resin sample consisting only of α-type crystals and a PVDF resin sample consisting only of β-type crystals are mixed to contain a β-type crystal PVDF resin Samples with known F (β) are prepared and IR spectra are measured. In the resulting IR spectrum, the absorbance (peak height) of the light absorption characteristics of the alpha-type crystal A ^alpha, absorbance of light absorption characteristics of the beta-form crystals (peak height) measuring the A ^beta.

Subsequently, it solved with respect to equation (2a) E β ^{/ α,} is substituted in the following equation (3a) to obtain a correction coefficient E ^{beta / alpha.}

E [ ^{beta] / [alpha]} = {A [ ^beta] * (1-F ([beta]))} / (A [ ^alpha] * F ([beta])) (3a)
The IR spectrum is measured for a plurality of samples with different mixing ratios, the correction coefficient ^{Eβ / α} is obtained for each sample by the above method, and the average value thereof is calculated.

(Iii) Calculation of content ratio of α-type crystal and β-type crystal in sample Based on the average value of correction coefficient E ^{β / α} calculated in (ii) above and the measurement result of IR spectrum of sample, The content F (α) of the PVDF resin of the α-type crystal relative to the sum of the α-type crystal and the β-type crystal in the sample is calculated.

Specifically, a laminate including the porous layer is produced by a production method to be described later, and the laminate is cut out to produce a measurement sample, and then subjected to FT-IR spectroscopy at room temperature (about 25 ° C.). meter (Bruker Optics Co.; ALPHA Platinum-ATR model) using, for said sample, with a resolution ^{4 cm -1,} scan number 512 times, the infrared absorption spectrum of the measurement area wavenumber ^{4000cm -1 ~400cm} -1 Measure. Here, the measurement sample cut out is preferably a square of 80 mm × 80 mm square. However, the size and shape of the measurement sample are not limited to this as long as the infrared absorption spectrum can be measured. Then, from the obtained spectrum, an absorption intensity (A ^α ) of 765 cm ⁻¹ that is the characteristic absorption of the α-type crystal and an absorption intensity (A ^β ) of 840 cm ⁻¹ that is the characteristic absorption of the β-type crystal are obtained. The starting point and ending point for forming each peak corresponding to the wave number are connected by a straight line, and the length of the straight line and the peak wave number is defined as the absorption intensity. alpha-type crystal, the maximum value of the absorption intensity possible in the wave number range of ^{775cm -1 ~745cm} -1 and the absorption intensity of 765cm ^-1 (A ^α), β-type crystals, wavenumber ^{850cm -1 ~815cm} -1 The maximum value of absorption intensity that can be taken within the range of 840 cm ^{−1 is taken as} the absorption intensity (A ^β ). In the present specification, the average value of the correction coefficient E ^{β / α} is 1.681 (see the description of JP-A-2005-200263), and the content rate F (α) ( %). The calculation formula is the following formula (4a).

F (α) (%) = [1- {840 cm ⁻¹ absorption intensity (A ^β ) / (765 cm ⁻¹ absorption intensity (A ^α ) × correction coefficient (E ^{β / α} ) (1.681) +840 cm ^{− 1} absorption intensity ( ^Aβ ))}] × 100 (4a).

[Method for producing porous layer]
The porous layer according to the present invention can be produced, for example, by the same method as the method for producing a laminate and a separator for a non-aqueous secondary battery according to the present invention described later.

[Embodiments 2 and 3: Laminated body, separator for non-aqueous electrolyte secondary battery]
As Embodiments 2 and 3 of the present invention, the laminate according to the present invention and the nonaqueous electrolyte secondary battery separator according to the present invention (also referred to as a nonaqueous secondary battery separator) will be described below.

  The laminate according to the present invention includes a porous substrate mainly composed of a polyolefin-based resin, and a porous layer according to Embodiment 1 of the present invention, which is laminated on at least one surface of the porous substrate. It is characterized by including. A separator for a non-aqueous secondary battery according to the present invention relates to Embodiment 1 of the present invention, in which a porous base material containing a polyolefin-based resin as a main component and at least one surface of the porous base material are laminated. And a porous layer.

  Below, the porous base material which comprises the laminated body which concerns on this invention, and the separator for nonaqueous secondary batteries, and the manufacturing method of the laminated body which concerns on this invention, and the separator for nonaqueous secondary batteries are demonstrated.

<Porous substrate>
The porous substrate in the laminate or the non-aqueous secondary battery separator of the present invention may be a porous and membrane-like substrate (polyolefin-based porous substrate) containing polyolefin as a main component. It is preferable that That is, the porous substrate has a structure having pores connected to the inside thereof, and is a porous film mainly composed of polyolefin that allows gas and liquid to pass from one surface to the other surface. Is preferred. The porous substrate may be formed from one layer or may be formed from a plurality of layers.

The ratio of the polyolefin component in the porous substrate is usually 50% by volume or more, preferably 90% by volume or more, and more preferably 95% by volume or more of the entire porous substrate. The polyolefin component of the porous substrate preferably contains a high molecular weight component having a weight average molecular weight in the range of 5 × 10 ⁵ to 15 × 10 ⁶ . By including a polyolefin component having a weight average molecular weight of 1,000,000 or more as the polyolefin component of the porous substrate, the strength of the porous substrate, the laminate, and the separator for the non-aqueous secondary battery is preferably increased.

  Examples of the polyolefin include high molecular weight homopolymers or copolymers obtained by polymerizing ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene and the like. The porous substrate is a layer containing one kind of these polyolefins and / or a layer containing two or more kinds of these polyolefins. In particular, high molecular weight polyethylene mainly composed of ethylene is preferable. In addition, a porous base material does not prevent containing components other than polyolefin in the range which does not impair the function of the said layer.

  The air permeability of the porous substrate is usually in the range of 30 seconds / 100 cc to 500 seconds / 100 cc as a Gurley value, and preferably in the range of 50 seconds / 100 cc to 300 seconds / 100 cc. When the porous substrate has an air permeability in the above range, the separator can obtain sufficient ion permeability when the porous substrate is used as a member constituting the separator.

  The film thickness of the porous substrate is appropriately determined in consideration of the number of layers of the laminate or the separator for the nonaqueous secondary battery. In particular, when the porous layer is formed on one side (or both sides) of the porous substrate, the thickness of the porous substrate is preferably in the range of 4 μm to 40 μm, more preferably in the range of 7 μm to 30 μm.

The basis weight of the porous substrate is the strength, film thickness, handling property and weight of the laminate, and the weight energy density and volume energy density of the battery when used as a member constituting a separator of a non-aqueous secondary battery. in terms of being able to increase the, ^usually from ^{4g / m 2 ~20g / m 2} , the range of 5g / ^{m 2} ~12g / m 2 is preferred.

  Examples of such a porous substrate include a porous polyolefin layer described in JP2013-14017A, a polyolefin porous film described in JP2012-54229A, and JP2014-0405580A. The polyolefin-based porous film described can be suitably used.

  Also with respect to the method for producing the porous substrate, a known method can be used and is not particularly limited. For example, as described in JP-A-7-29563, there is a method in which a plasticizer is added to a thermoplastic resin to form a film, and then the plasticizer is removed with an appropriate solvent.

Specifically, for example, when the porous substrate is formed from a polyolefin resin containing ultrahigh molecular weight polyethylene and a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, from the viewpoint of production cost, the following is shown. It is preferable to manufacture by the method containing process (1)-(4).
(1) Kneading 100 parts by weight of ultrahigh molecular weight polyethylene, 5 parts by weight to 200 parts by weight of a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, and 100 parts by weight to 400 parts by weight of an inorganic filler such as calcium carbonate. Obtaining a polyolefin resin composition;
(2) A step of forming a sheet using the polyolefin resin composition,
(3) A step of removing the inorganic filler from the sheet obtained in the step (2),
(4) A step of stretching the sheet obtained in the step (3).
In addition, you may utilize the method as described in each patent document mentioned above.

  Moreover, regarding a porous base material, you may use the commercial item which has the characteristic mentioned above.

  Moreover, it is more preferable that the porous substrate is subjected to a hydrophilic treatment before forming the porous layer, that is, before applying a coating liquid described later. By applying a hydrophilic treatment to the porous substrate, the coating property of the coating liquid is further improved, and therefore a more uniform porous layer can be formed. This hydrophilization treatment is effective when the proportion of water in the solvent (dispersion medium) contained in the coating liquid is high. Specific examples of the hydrophilization treatment include known treatments such as chemical treatment with acid or alkali, corona treatment, plasma treatment, and the like. Among the hydrophilization treatments, the porous substrate can be hydrophilized in a relatively short time, and the hydrophilization is limited only to the vicinity of the surface of the porous substrate, and the inside of the porous substrate is not altered. Therefore, corona treatment is more preferable.

  The porous substrate may contain another porous layer in addition to the porous layer according to Embodiment 1 of the present invention, as necessary. Examples of the other porous layer include known porous layers such as a heat-resistant layer, an adhesive layer, and a protective layer. Specific examples of the porous layer include a porous layer having the same composition as the porous layer according to Embodiment 1 of the present invention.

<Shutdown characteristics>
Examples of the method for measuring the shutdown characteristics in the laminate include the following methods. Moreover, the shutdown characteristic in the said separator for non-aqueous secondary batteries can also be measured with the same method.

A circular measurement sample having a diameter of 19.4 mm is cut out from the laminate (laminated porous film) to obtain a measurement sample. In addition, members of 2032 type coin cell (upper lid, lower lid, gasket, Kapton ring (outer diameter 16.4 mm, inner diameter 8 mm, thickness 0.05 mm), spacer (diameter spacer 15.5 mm in diameter, 0.5 mm in thickness) ), Aluminum ring (outer diameter 16m)
m, inner diameter 10 mm, thickness 1.6 mm)) (made by Hosen Co., Ltd.).

Then, after placing the measurement sample and gasket ring in order from the lower lid and impregnating with 10 μmL of the electrolyte, the Kapton ring, spacer, aluminum ring, and upper lid are placed in order from the top of the measurement sample. A coin cell for measurement is produced by sealing with Hosen Co., Ltd.). Here, as an electrolytic solution, LiBF ₄ was dissolved in a mixed solvent having a volume ratio of 91.5: 8.5 of propylene carbonate and NIKKOLBT-12 (manufactured by Nikko Chemicals Co., Ltd.) (LiBF ₄ Concentration: 1.0 mol / L) is used.

While the temperature inside the coin cell for measurement was raised from room temperature to 150 ° C. at a rate of 15 ° C./min, the temperature inside the coin cell was changed to a digital multimeter (manufactured by ADC Corporation; 7352A) at 1 kHz in the coin cell. Is continuously measured with an LCR meter (manufactured by Hioki Electric Co., Ltd .; IM3523).

  Assume that it is confirmed that the coin cell has a shutdown function when the resistance value at 1 kHz of the coin cell becomes 5000Ω or more during measurement.

  The above-mentioned measurement is performed on a plurality of coin cells, and as a result, the ratio of coin cells that are confirmed to have a shutdown function is calculated to evaluate the shutdown characteristics.

<Laminated body, production method of separator for non-aqueous secondary battery>
The method for producing the laminates and separators for non-aqueous secondary batteries according to Embodiments 2 and 3 of the present invention is not particularly limited, and various methods can be mentioned.

  For example, a porous layer containing a PVDF-based resin is formed on the surface of a polyolefin-based resin microporous membrane serving as a porous substrate by using any one of the following steps (1) to (3). In the case of steps (1) and (2), it is produced by further drying the resulting porous layer and removing the solvent.

  (1) After coating the surface of the porous substrate with a coating solution in which the PVDF resin forming the porous layer is dissolved, the porous substrate is a poor solvent for the PVDF resin. The process of depositing the porous layer containing the said PVDF-type resin by being immersed in the precipitation solvent which is.

  (2) After coating the coating liquid in which the PVDF resin forming the porous layer is dissolved on the surface of the porous substrate, the liquidity of the coating liquid is obtained using a low boiling point organic acid. A step of precipitating a porous layer containing the PVDF-based resin by making it acidic.

  (3) After applying the coating liquid in which the PVDF-based resin forming the porous layer is dissolved to the surface of the porous base material, using far-infrared heating or freeze drying, Evaporating the solvent to deposit a porous layer containing the PVDF resin.

  The solvent (dispersion medium) in the coating solution is not particularly limited as long as it does not adversely affect the porous substrate, can dissolve the PVDF resin uniformly and stably, and can uniformly and stably disperse the filler. It is not something. As the solvent (dispersion medium), for example, N-methylpyrrolidone is more preferably used.

For the precipitation solvent, for example, another solvent (hereinafter, solvent X) that dissolves in the solvent (dispersion medium) contained in the coating liquid and does not dissolve the PVDF resin contained in the coating liquid is used. Can do. The porous substrate on which the coating solution was applied and the coating film was formed was immersed in the solvent X, and the solvent (dispersion medium) in the coating film on the porous substrate or the support was replaced with the solvent X. Thereafter, the solvent (dispersion medium) can be efficiently removed from the coating liquid by evaporating the solvent X. For example, isopropyl alcohol or t-butyl alcohol is preferably used as the precipitation solvent.

  In the step (2), as the low boiling point organic acid, for example, p-toluenesulfonic acid, acetic acid and the like can be used.

  In the step (3), far-infrared heating or freeze-drying has an advantage that the shape of the pores of the porous layer is less likely to be collapsed during deposition as compared with other drying methods (air drying or the like).

  Moreover, the method including the process shown to the following (4) is mentioned as another method of manufacturing the laminated body of this invention.

  (4) A coating liquid in which fine particles of PVDF resin forming the porous layer are dispersed in a dispersion medium such as water is applied onto a porous substrate, and the dispersion medium is dried and removed to make the porous layer porous. Forming a layer;

  In the step (4), the dispersion medium is preferably water, and the dispersion medium such as water may be diluted and replaced by immersing the laminated film before drying in lower alcohols. As the lower alcohol, isopropyl alcohol or t-butyl alcohol is preferable.

The coating amount of the porous layer, from the viewpoint of adhesiveness and ion permeability of the electrode is preferably in the range of 0.5g ^/ m ² ~1.5g / m 2 on one side of the porous substrate. That is, the amount of the coating liquid applied on the porous substrate is adjusted so that the coating amount of the porous layer in the obtained laminate and the separator for the nonaqueous secondary battery is in the above range. Is preferred.

  Further, when a heat resistant layer is further laminated on the laminate, the same method as described above is performed except that the resin constituting the heat resistant layer is used instead of the resin constituting the porous layer. Thus, the heat-resistant layer can be laminated.

  Furthermore, when a filler is contained in the porous layer, the filler is contained by using a solution in which a filler is further dispersed in the solution instead of the solution in which the resin forming the porous layer is dissolved. A porous layer can be formed.

  In the present embodiment, in the steps (1) to (3), by changing the amount of resin in the solution in which the resin that forms the porous layer is changed, 1 square meter of the porous layer after being immersed in the electrolytic solution The volume of the resin that has been absorbed and that has absorbed the electrolyte can be adjusted.

  Moreover, the porosity and average pore diameter of the porous layer after being immersed in electrolyte solution can be adjusted by changing the solvent amount which melt | dissolves resin which forms a porous layer.

<Method for controlling crystal form of PVDF resin>
Moreover, the separator for a non-aqueous secondary battery of the present invention is a drying temperature and a precipitation temperature in the above-described method (in the case where a porous layer containing a PVDF resin is deposited using a deposition solvent or a low boiling point organic acid). By adjusting the deposition temperature, the crystal form of the PVDF resin contained in the obtained porous layer is controlled. Specifically, in the PVDF resin, the α-type crystal content is 10 when the total content of the α-type crystal and the β-type crystal is 100 mol%.
The laminate and the separator for a non-aqueous secondary battery of the present invention are manufactured by adjusting the drying temperature and the deposition temperature so that the mol% is 65 mol% or more and 65 mol% or less.

  In the PVDF resin, when the total content of α-type crystals and β-type crystals is 100 mol%, a drying temperature for setting the content of α-type crystals to 10 mol% or more and 65 mol% or less, and The deposition temperature can be appropriately changed according to the method for producing the porous layer, the solvent (dispersion medium) to be used, the type of the deposition solvent, the low boiling point organic acid, and the like. For example, when N-methylpyrrolidone is used as the solvent for dissolving the PVDF resin and isopropyl alcohol is used as the precipitation solvent and the porous layer is formed in the above-described step (1), the precipitation temperature is set to −30 ° C. to 10 ° C. Preferably, the drying temperature is 30 ° C.

[Embodiments 4 and 5: Non-aqueous secondary battery member, non-aqueous secondary battery]
As Embodiment 4 and 5 of this invention, it demonstrates below regarding the member for nonaqueous secondary batteries, and a nonaqueous secondary battery. The nonaqueous secondary battery member of the present invention is characterized in that the positive electrode, the porous layer according to Embodiment 1 of the present invention, and the negative electrode are arranged in this order. The nonaqueous secondary battery of the present invention is characterized by including a porous layer according to Embodiment 1 of the present invention. A non-aqueous secondary battery is a non-aqueous secondary battery that obtains an electromotive force, for example, by doping or dedoping lithium, and the positive electrode, the porous layer of the present invention, the porous substrate, and the negative electrode It is a lithium ion secondary battery provided with the non-aqueous secondary battery member laminated | stacked in order. Hereinafter, a lithium ion secondary battery will be described as an example. The constituent elements of the nonaqueous secondary battery other than the porous layer are not limited to the constituent elements described below.

  The nonaqueous secondary battery of this invention should just be equipped with the positive electrode, the negative electrode, and the porous layer of this invention, and another structure is not specifically limited. The nonaqueous secondary battery of the present invention preferably further comprises a porous substrate. The non-aqueous secondary battery of the present invention is usually a battery in which a negative electrode and a positive electrode are impregnated with an electrolyte in a structure in which the negative electrode and the positive electrode face each other through the above-described laminate including the porous layer and the porous substrate of the present invention The element has a structure encapsulated in an exterior material. The non-aqueous secondary battery is preferably a non-aqueous electrolyte secondary battery, particularly a lithium ion secondary battery. Doping means occlusion, support, adsorption, or insertion, and means a phenomenon in which lithium ions enter an active material of an electrode such as a positive electrode. A non-aqueous secondary battery manufactured by using the above-described laminate according to the present invention as a separator for a non-aqueous secondary battery is excellent in the handling property of the separator, and thus has a high manufacturing yield.

  As the positive electrode of the nonaqueous secondary battery, a positive electrode sheet having a structure in which an active material layer containing a positive electrode active material and a binder resin is usually formed on a current collector can be used. The active material layer may further include a conductive additive.

Examples of the positive electrode active material include lithium-containing transition metal oxides, and specifically include 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 , LiAl _1/4 Ni _3/4 O _{2 and the} like.

  Examples of the binder resin in the positive electrode include PVDF resins.

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

  Examples of the current collector in the positive electrode include aluminum foil, titanium foil, and stainless steel foil having a thickness of 5 μm to 20 μm.

  As the negative electrode of the non-aqueous secondary battery, a negative electrode sheet having a structure in which an active material layer containing a negative electrode active material and a binder resin is formed on a current collector can be used. The active material layer may further contain a conductive additive.

  Examples of the negative electrode active material include materials that can occlude lithium electrochemically, and specific examples include carbon materials; alloys of silicon, tin, aluminum, and the like with lithium; and the like.

  Examples of the binder resin in the negative electrode include PVDF resins and styrene-butadiene rubber. In the nonaqueous secondary battery of the present invention, sufficient adhesion to the negative electrode can be ensured even when styrene-butadiene rubber is used as the negative electrode binder.

  Examples of the conductive auxiliary in the negative electrode include carbon materials such as acetylene black, ketjen black, and graphite powder.

  Examples of the current collector in the negative electrode include copper foil, nickel foil, and stainless steel foil having a thickness of 5 μm to 20 μm. Moreover, it may replace with the said negative electrode and may use metal lithium foil as a negative electrode.

The electrolytic solution is a solution in which a lithium salt is dissolved in a non-aqueous solvent. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO _{4, and the} like.

  The non-aqueous solvent includes all solvents generally used in non-aqueous secondary batteries, and is not limited to, for example, a mixed solvent (volume ratio of ethyl methyl carbonate, diethyl carbonate and ethylene carbonate is 50:20:30). Absent.

  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-substituted products thereof; γ-butyrolactone, and cyclic esters such as γ-valerolactone; these may be used alone or in combination.

  As an electrolytic solution, 0.5M lithium salt is added to a solvent in which cyclic carbonate and chain carbonate are mixed at a volume ratio (cyclic carbonate / chain carbonate) of 20/80 to 40/60 (more preferably 30/70). Those dissolved in ~ 1.5M are preferred.

  Examples of the exterior material include metal cans and aluminum laminate film packs. The battery has a square shape, a cylindrical shape, a coin shape, and the like.

  A non-aqueous secondary battery is, for example, an exterior material (for example, an aluminum laminate film) by impregnating a member for a non-aqueous secondary battery in which the above-described laminate is disposed as a separator between a positive electrode sheet and a negative electrode sheet. And can be manufactured by pressing the non-aqueous secondary battery member from above the exterior material.

  Moreover, the laminated body according to the present invention as the separator can be bonded by overlapping with the electrode. Therefore, although the said press is not an essential process in battery manufacture, in order to improve the adhesiveness with the laminated body which concerns on this invention as an electrode and a separator, it is preferable to perform a press. Furthermore, in order to improve the adhesiveness between the electrode and the laminate according to the present invention as a separator, the press is preferably a press while heating (hot press).

  The method of disposing the laminate according to the present invention as a separator between the positive electrode sheet and the negative electrode sheet is a method of laminating at least one layer of the positive electrode sheet, the laminate according to the present invention as a separator, and the sheets in this order ( A so-called stack method) may be used, and a positive electrode sheet, a laminate according to the present invention as a separator, a negative electrode sheet, and a laminate according to the present invention as a separator may be stacked in this order and rolled in the length direction.

[Other Embodiments]
In the above description, a laminate according to the present invention as a separator for a nonaqueous secondary battery in which a porous layer is formed on a porous substrate is manufactured, and the present invention as a separator for the nonaqueous secondary battery is manufactured. By stacking the positive electrode sheet and the negative electrode sheet so as to sandwich the laminated body, a non-aqueous secondary battery member including the laminated body and the electrode according to the present invention as a non-aqueous secondary battery separator is manufactured. . However, the manufacturing method of the non-aqueous secondary battery according to the present invention is not limited to this.

  For example, the porous layer may be formed by applying a solution in which the PVDF-based resin contained in the porous layer is dissolved onto at least one surface of the positive electrode sheet or the negative electrode sheet. As this formation method, a method including any of the above-described steps (1) to (4) may be used. Then, the positive electrode sheet and the negative electrode sheet are stacked so as to sandwich the porous base material, and hot-pressed, whereby the laminate and the electrode according to the present invention as a separator for a non-aqueous secondary battery are used. A member is manufactured. At this time, the electrode sheet on which the porous layer is formed may be arranged so that the porous layer faces the porous substrate. Thereby, the member for nonaqueous secondary batteries by which the electrode, the porous layer, the porous base material, (porous layer), and the electrode were laminated | stacked in this order can be manufactured. As a result, the non-aqueous secondary battery obtained has an α-type crystal content of 100 mol% when the total content of the α-type crystal and the β-type crystal is between the electrode and the porous substrate. A non-aqueous secondary battery in which a porous layer containing a PVDF resin that is 10 mol% or more and 65 mol% or less is disposed can be manufactured.

  The non-aqueous secondary battery of the present invention has a total of the content of α-type crystals and β-type crystals laminated on one or both sides of a porous base material mainly composed of polyolefin and the porous base material. Since a laminate including a porous layer containing a PVDF-based resin having an α-type crystal content of 10 mol% or more and 65 mol% or less in the case of mol% is provided as a separator, a shutdown function is provided. .

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

[Shutdown characteristics test]
[Various measurement methods]
Regarding the laminates obtained in the following Examples 1 to 4 and Comparative Examples 1 to 4, the calculation of the α ratio and the shutdown test were performed by the following methods.

(1) α ratio calculation method The α-type crystal is compared with the total content of the α-type crystal and the β-type crystal of the PVDF resin contained in the porous layer in the laminates obtained in the following examples and comparative examples. The molar ratio (%) was α ratio (%), and the α ratio was measured by the following method.

The laminate was cut into a square of 80 mm × 80 mm, and FT-IR spectrometer (manufactured by Bruker Optics; ALPHA Platinum) at room temperature (about 25 ° C.).
m-ATR model) and according to the resolution of ^{4 cm -1,} scan number 512 times to obtain an infrared absorption spectrum at a wavenumber of ^{4000cm -1 ~400cm} -1 is measured region. From the obtained spectra, it was determined and the absorption intensity of 840 cm ^-1 which is the characteristic absorption of an absorption intensity and β-form crystals of 765cm ^-1 which is the characteristic absorption of an α-type crystal. The starting point and the ending point for forming each peak corresponding to the wave number are connected by a straight line, and the length of the straight line and the peak wave number is taken as the absorption intensity. The α-type crystal has a wave number of 775 cm ^{−1 to} 745 cm ^−1. maximum absorption intensity that can be taken within the scope of the absorption intensity of 765cm ^-1, β-type crystals, absorption of 840 cm ^-1 to a maximum value of the absorption intensity possible in the wave number range of ^{850cm -1 ~815cm} -1 Strength.

α ratio calculation determines the absorption intensity of 840 cm ^-1 corresponding to the absorption intensity and the β-form crystals of 765cm ^-1 which corresponds to α-type crystal as described above, with reference to the description of JP-A-2005-200623, Using the numerical value obtained by multiplying the absorption intensity of the α-type crystal by a correction coefficient of 1.681, the calculation was performed by the following equation (4a).

α ratio (%) = [1- {absorption intensity of 840 cm ^-1 / (absorption intensity of absorption intensity × correction coefficient (1.681) + 840 cm ^-1 of 765cm ^-1)}] × 100 ... (4a).

(2) Shutdown test A circular measurement sample having a diameter of 19.4 mm was cut out from the laminates (laminated porous films) obtained in Examples 1 to 4 and Comparative Examples 1 to 4, and used as measurement samples. In addition, members of 2032 type coin cell (upper lid, lower lid, gasket, Kapton ring (outer diameter 16.4 mm, inner diameter 8 mm, thickness 0.05 mm), spacer (diameter spacer 15.5 mm in diameter, 0.5 mm in thickness) ), An aluminum ring (outer diameter 16 mm, inner diameter 10 mm, thickness 1.6 mm)) (made by Hosen Co., Ltd.) was prepared.

Then, after placing the measurement sample and gasket ring in order from the lower lid and impregnating with 10 μmL of the electrolyte, the Kapton ring, spacer, aluminum ring, and upper lid are placed in order from the top of the measurement sample. A coin cell for measurement was produced by sealing with Hosen Co., Ltd.). Here, as an electrolytic solution, LiBF ₄ was dissolved in a mixed solvent having a volume ratio of 91.5: 8.5 of propylene carbonate and NIKKOLBT-12 (manufactured by Nikko Chemicals Co., Ltd.) (LiBF ₄ Concentration: 1.0 mol / L) was used.

While the temperature inside the coin cell for measurement was raised from room temperature to 150 ° C. at a rate of 15 ° C./min, the temperature inside the coin cell was changed to a digital multimeter (manufactured by ADC Corporation; 7352A) at 1 kHz in the coin cell. Was continuously measured by an LCR meter (manufactured by Hioki Electric Co., Ltd .; IM3523).

  During the measurement, when the resistance value of the coin cell at 1 kHz was 5000Ω or more, it was confirmed that the coin cell had a shutdown function.

  The above measurement was performed on a plurality of (three) coin cells, and as a result, the proportion of coin cells that were confirmed to have a shutdown function was calculated. As a result, it has been confirmed that a shutdown function is provided, and the ratio of coin cells (shutdown function occurrence rate) is 60% or more, “◯”, 30% or more and less than 60% “△”, and less than 30% Is shown in Table 1 as "x".

[Example 1]
N-methyl-2-pyrrolidone (hereinafter also referred to as “NMP”) solution of PVDF resin (polyvinylidene fluoride homopolymer) (manufactured by Kureha Corporation; trade name “L # 7305”)
The weight average molecular weight: 1,000,000) was used as the coating liquid, and the PVDF resin in the coating liquid was 1 by a doctor blade method on the polyethylene porous film (thickness 12 μm, porosity 44%). It apply | coated so that it might become 5.0g per square meter. The obtained coated material was immersed in 2-propanol while the coating film was in an NMP wet state and allowed to stand at -25 ° C. for 5 minutes to obtain a laminated porous film (1-i). The obtained laminated porous film (1-i) was further immersed in another 2-propanol in a dipping solvent wet state and allowed to stand at 25 ° C. for 5 minutes to obtain a laminated porous film (1-ii). It was. The obtained laminated porous film (1-ii) was dried at 30 ° C. for 5 minutes to obtain a laminate (1). Table 1 shows the evaluation results of the obtained laminate (1).

[Example 2]
The coated product obtained in the same manner as in Example 1 was immersed in 2-propanol while the coating film was in an NMP wet state, and allowed to stand at −5 ° C. for 5 minutes to obtain a laminated porous film (2-i ) The obtained laminated porous film (2-i) was immersed in another 2-propanol in a dipping solvent wet state and allowed to stand at 25 ° C. for 5 minutes to obtain a laminated porous film (2-ii). It was. The obtained laminated porous film (2-ii) was dried at 30 ° C. for 5 minutes to obtain a laminate (2). Table 1 shows the evaluation results of the obtained laminate (2).

[Example 3]
An NMP solution of PVDF resin (polyvinylidene fluoride homopolymer) (manufactured by Kureha Co., Ltd .; trade name “L # 1120”, weight average molecular weight: 280,000) was used as the coating liquid, and polyethylene was obtained in the same manner as in Example 1. The porous film (thickness 12 μm, porosity 44%) was applied. The obtained coated material was immersed in 2-propanol while the coating film was in an NMP wet state, and was allowed to stand at −5 ° C. for 5 minutes in the same manner as in Example 1, to obtain a laminated porous film (3- i) was obtained. The obtained laminated porous film (3-i) was further immersed in another 2-propanol in a dipping solvent wet state and allowed to stand at 25 ° C. for 5 minutes to obtain a laminated porous film (3-ii). It was. The obtained laminated porous film (3-ii) was dried at 30 ° C. for 5 minutes to obtain a laminated body (3) having a porous layer. Table 1 shows the evaluation results of the obtained laminate (3).

[Example 4]
Example 1 with an NMP solution of PVDF resin (polyvinylidene fluoride-hexafluoropropylene copolymer) (manufactured by Kureha Co., Ltd .; trade name “L # 9305”, weight average molecular weight: 1,000,000) as a coating solution In the same manner, it was coated on a polyethylene porous film (thickness 12 μm, porosity 44%). The obtained coated material was immersed in 2-propanol while the coating film was in an NMP wet state, and allowed to stand at 10 ° C. for 5 minutes to obtain a laminated porous film (4-i). The obtained laminated porous film (4-i) was immersed in another 2-propanol in a dipping solvent wet state and allowed to stand at 25 ° C. for 5 minutes to obtain a laminated porous film (4-ii). It was. The obtained laminated porous film (4-ii) was dried at 30 ° C. for 5 minutes to obtain a laminated body (4) having a porous layer. Table 1 shows the evaluation results of the obtained laminate (4).

[Comparative Example 1]
The coated product and the coating film obtained by the same method as in Example 3 were immersed in 2-propanol with the NMP wet state, and allowed to stand at 0 ° C. for 5 minutes to give a laminated porous film (4-i). Got. The obtained laminated porous film (5-i) was immersed in another 2-propanol in a dipping solvent wet state and allowed to stand at 25 ° C. for 5 minutes to obtain a laminated porous film (4-ii). . The obtained laminated porous film (5-ii) was dried at 65 ° C. for 5 minutes to obtain a laminate (5). Table 1 shows the evaluation results of the obtained laminate (5).

[Comparative Example 2]
PVDF resin (polyvinylidene fluoride-hexafluoropropylene copolymer, manufactured by Kureha Co., Ltd .; trade name “W # 9300”, weight average molecular weight; 1,000,000) was added to dimethyl so that the solid content was 5% by mass. The mixture was stirred and dissolved in a mixed solvent of acetamide / tripropylene glycol = 7/3 [mass ratio] at 65 ° C. for 30 minutes. The obtained solution was used as a coating solution, and the PVDF resin in the coating solution was 5.0 g per square meter by a doctor blade method on a polyethylene porous film (thickness 12 μm, porosity 44%). It was applied to. The obtained coated material was immersed in water / dimethylacetamide / tripropylene glycol = 57/30/13 [mass ratio] while the coating film was in an NMP wet state, and allowed to stand at 40 ° C. for 5 minutes to obtain a laminated porous film. A quality film (6-i) was obtained. The obtained laminated porous film (6-i) was washed with water to obtain a laminated porous film (6-ii). The obtained laminated porous film (6-ii) was dried at 65 ° C. for 5 minutes to obtain a laminated body (6) having a porous layer. Table 1 shows the evaluation results of the obtained laminate (6).

[Comparative Example 3]
The coated product obtained by the same method as in Example 3 was immersed in 2-propanol cooled with dry ice while the coating film was in an NMP wet state, and allowed to stand at 25 ° C. for 5 minutes, and laminated porous material A film (7-i) was obtained. The obtained laminated porous film (7-i) was further immersed in another 2-propanol in a dipping solvent wet state and allowed to stand at 25 ° C. for 5 minutes to obtain a laminated porous film (7-ii). . The obtained laminated porous film (7-ii) was dried at 30 ° C. for 5 minutes to obtain a laminate (7). Table 1 shows the evaluation results of the obtained laminate (7).

[Comparative Example 4]
The coated product obtained by the same method as in Example 3 was immersed in 2-propanol cooled with dry ice while the coating film was in an NMP wet state, and allowed to stand at 25 ° C. for 5 minutes, and laminated porous material A film (8-i) was obtained. The obtained laminated porous film (8-i) was further immersed in another 2-propanol in a dipping solvent wet state and allowed to stand at 25 ° C. for 5 minutes to obtain a laminated porous film (8-ii). . The obtained laminated porous film (8-ii) was dried at 65 ° C. for 5 minutes to obtain a laminate (8). Table 1 shows the evaluation results of the obtained laminate (8).

[result]
The content (α ratio) of α-type crystals in the PVDF resin comprising α-type crystals and β-type crystals contained in the porous layer in the laminate produced in Examples 1 to 4 is 10 mol% or more. It was shown that 60% or more of the coin cells (non-aqueous secondary batteries) including the laminates (1) to (4) that are 65 mol% or less as a separator have a shutdown function.

  In addition, the α-type crystal content (α ratio) in the PVDF resin made of α-type crystals and β-type crystals contained in the porous layer in the laminate produced in Comparative Examples 1 to 4 was 10 mol. % Of the coin cells (non-aqueous secondary battery) containing the laminates (5) to (8) higher than 65% by mole as separators are less than 60%, and Example 1 It turned out that the ratio which shows a shutdown characteristic is smaller than the coin cell containing laminated body (1)-(4) obtained by ~ 4.

  Therefore, among PVDF resins composed of α-type crystals and β-type crystals, a laminate including a porous layer having an α-type crystal content (α ratio) of 10 mol% or more and 65 mol% or less has a shutdown function. It turned out that it is preferable as a separator in the coin cell (non-aqueous secondary battery) provided.

[Battery storage stability test]
Next, a non-aqueous secondary battery was produced by the production method shown below. And the battery storage stability of the manufactured nonaqueous secondary battery was measured by the battery storage stability test method shown below.

[Method for producing non-aqueous electrolyte secondary battery, test method for battery storage stability]
<Method for producing non-aqueous electrolyte secondary battery>
The following positive electrode, negative electrode, and each of the laminates produced in Examples 5 and 6 and Comparative Example 5 were used as non-aqueous secondary battery separators, and the non-aqueous secondary battery was assembled as follows. It produced according to.

(Positive electrode)
A commercially available positive electrode manufactured by applying LiNi _0.5 Mn _0.3 Co _0.2 O ₂ / conductive material / PVDF (weight ratio 92/5/3) to an aluminum foil was used. Cut the aluminum foil so that the size of the positive electrode active material layer formed on the positive electrode is 40 mm × 35 mm and the outer periphery of the positive electrode active material layer is 13 mm wide and no positive electrode active material layer is formed. A positive electrode was obtained. The positive electrode active material layer had a thickness of 58 μm and a density of 2.50 g / cm ³ .

(Negative electrode)
A commercially available negative electrode produced by applying graphite / styrene-1,3-butadiene copolymer / sodium carboxymethylcellulose (weight ratio 98/1/1) to a copper foil was used. Cut off the copper foil from the negative electrode so that the size of the portion where the negative electrode active material layer was formed was 50 mm × 40 mm and the outer periphery had a portion with a width of 13 mm and no negative electrode active material layer formed. A negative electrode was obtained. The thickness of the negative electrode active material layer was 49 μm, and the density was 1.40 g / cm ³ .

(Assembly method)
By laminating (arranging) the positive electrode, the non-aqueous secondary battery separator (laminated body), and the negative electrode in this order in a laminate pouch, a non-aqueous electrolyte secondary battery member was obtained. At this time, the positive electrode and the negative electrode were disposed so that the entire main surface of the positive electrode active material layer of the positive electrode was included in the range of the main surface of the negative electrode active material layer of the negative electrode (overlaid on the main surface). The separator for a non-aqueous secondary battery was obtained by cutting the laminate obtained in each of Examples 5 and 6 and Comparative Example 5 into a rectangular shape having a size of 5.5 cm × 4.0 cm. It is.

Subsequently, the non-aqueous electrolyte secondary battery member was put in a bag in which an aluminum layer and a heat seal layer were laminated, and 0.20 mL of the non-aqueous electrolyte was put in this bag. The non-aqueous electrolyte was prepared by dissolving LiPF ₆ having ethylene carbonate and diethyl carbonate concentration of 1.0 mol / L in a mixed solvent having a volume ratio of ethyl methyl carbonate, diethyl carbonate and ethylene carbonate of 50:20:30. The electrolyte solution was used. And the non-aqueous secondary battery was produced by heat-sealing the said bag, decompressing the inside of a bag.

[Battery storage stability test method]
With respect to a new non-aqueous secondary battery produced by the method shown above and not subjected to a charge / discharge cycle, the voltage range at 25 ° C .; 4.1 to 2.7 V, current value; 0.2 C (1 hour) The initial charge / discharge of 4 cycles was performed with 1 cycle as the current value for discharging the rated capacity with a discharge capacity of 1% in 1 hour, and the same for the following.

  Subsequently, charging was performed at 55 ° C. with a constant current of charging current value: 1 C, voltage: 4.2 V, and after the voltage reached the 4.2 V charging state, the storage test was performed while maintaining the voltage at 4.2 V. I went for a week. In the storage test, the total amount of current values at which less than 0.02 C was detected was calculated as “integrated capacity by decomposition consumption current” (mAh). The calculated “integrated capacity based on the decomposition consumption current” means that the larger the value is, the more the current during storage is consumed for the decomposition of the electrolyte or the like. Therefore, a small value of “integrated capacity by decomposition consumption current” indicates that the non-aqueous secondary battery is excellent in battery storage stability. Table 2 shows the calculated value of “integrated capacity based on decomposition current consumption”.

[Example 5]
An NMP solution of PVDF resin (polyvinylidene fluoride-hexafluoropropylene copolymer) (manufactured by Kureha Co., Ltd .; trade name “L # 9305”, weight average molecular weight: 1,000,000) as a coating liquid, and a polyethylene porous film On the (thickness 12 μm, porosity 44%), by a doctor blade method, the PVDF resin in the coating solution was applied to 1.0 g per square meter. The obtained coating was immersed in 2-propanol while the coating film was in an NMP wet state, and allowed to stand at -25 ° C. for 5 minutes to obtain a laminated porous film (9-i). The obtained laminated porous film (9-i) was further immersed in another 2-propanol in a dipping solvent wet state and allowed to stand at 25 ° C. for 5 minutes to obtain a laminated porous film (9-ii). It was. The obtained laminated porous film (9-ii) was dried at 30 ° C. for 5 minutes to obtain a laminated body (9) having a porous layer. Table 2 shows the evaluation results of the battery storage stability of the non-aqueous secondary battery using the obtained laminate (9) as a separator.

[Example 6]
The coated product obtained in the same manner as in Example 5 was immersed in 2-propanol while the coating film was in an NMP wet state, and allowed to stand at 0 ° C. for 5 minutes to give a laminated porous film (10-i). Got. The obtained laminated porous film (10-i) was further immersed in another 2-propanol in a dipping solvent wet state and allowed to stand at 25 ° C. for 5 minutes to obtain a laminated porous film (10-ii). It was. The obtained laminated porous film (10-ii) was dried at 30 ° C. for 5 minutes to obtain a laminate (10) having a porous layer. Table 2 shows the evaluation results of the battery storage stability of the nonaqueous secondary battery using the obtained laminate (10) as a separator.

[Comparative Example 5]
The coated product obtained in the same manner as in Example 5 was immersed in 2-propanol while the coating film was in an NMP wet state, and allowed to stand at 5 ° C. for 5 minutes to give a laminated porous film (11-i). Got. The obtained laminated porous film (11-i) was further immersed in another 2-propanol in a dipping solvent wet state and allowed to stand at 25 ° C. for 5 minutes to obtain a laminated porous film (11-ii). It was. The obtained laminated porous film (11-ii) was dried at 30 ° C. for 5 minutes to obtain a laminate (11) having a porous layer. Table 2 shows the evaluation results of the battery storage stability of the nonaqueous secondary battery using the obtained laminate (11) as a separator.

[result]
The content (α ratio) of α-type crystals in the PVDF resin composed of α-type crystals and β-type crystals contained in the porous layer in the laminate produced in Examples 5 to 6 is 10 mol% or more. The non-aqueous secondary battery including the laminates (9) to (10) that is 65 mol% or less as a separator is manufactured in Comparative Example 5, and the α-type crystals and β contained in the porous layer in the laminate Batteries can be stored more stably than non-aqueous secondary batteries that include a laminate (11) in which the content (α ratio) of α-type crystals in the PVDF resin made of type crystals is outside the above range (67%). It was shown to be excellent in properties.

  Therefore, among PVDF resins composed of α-type crystals and β-type crystals, a laminate including a porous layer having an α-type crystal content (α ratio) of 10 mol% or more and 65 mol% or less is stored in a battery. It was found that the separator is more preferable as a separator in a non-aqueous secondary battery having stability.

  The porous layer which concerns on this invention can be utilized suitably for manufacture of the non-aqueous secondary battery which has a shutdown function. Therefore, the laminate according to the present invention can be widely used in the field of manufacturing non-aqueous secondary batteries.

Here, the content of the α-type crystal is calculated from the absorption intensity near 765 cm ⁻¹ in the IR spectrum of the porous layer, and the content of the β-type crystal is 840 cm ⁻ in the IR spectrum of the porous layer. It is calculated from the absorption intensity near ¹ .

Here, the content of the α-type crystal is calculated from the absorption intensity near 765 cm ⁻¹ in the IR spectrum of the porous layer, and the content of the β-type crystal is 840 cm ⁻ in the IR spectrum of the porous layer. It is calculated from the absorption intensity near ¹ .

Subsequently, the non-aqueous electrolyte secondary battery member was put in a bag in which an aluminum layer and a heat seal layer were laminated, and 0.20 mL of the non-aqueous electrolyte was put in this bag. The nonaqueous electrolyte solution, concentration 1.0 mol / L ethyl methyl carbonate of LiPF _6, 25 ° C. of the electrolyte mixture is dissolved in a solvent in a volume ratio of diethyl carbonate and ethylene carbonate 50:20:30 a Using. And the non-aqueous secondary battery was produced by heat-sealing the said bag, decompressing the inside of a bag.

Claims (9)

A porous layer containing a polyvinylidene fluoride resin,
In the polyvinylidene fluoride resin, when the total content of α-type crystals and β-type crystals is 100 mol%, the content of the α-type crystals is 10 mol% or more and 65 mol% or less. A porous layer characterized by
(Here, the content of α-type crystal is calculated from the absorption intensity around 765 nm in the IR spectrum of the porous layer, and the content of β-type crystal is the absorption intensity around 840 nm in the IR spectrum of the porous layer. Calculated from   The polyvinylidene fluoride resin is at least selected from the group consisting of a homopolymer of vinylidene fluoride and / or vinylidene fluoride and hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, trichloroethylene, and vinyl fluoride. The porous layer according to claim 1, wherein the porous layer is a copolymer with one kind of monomer.   The porous layer according to claim 1 or 2, wherein the polyvinylidene fluoride resin has a weight average molecular weight of 300,000 to 3,000,000. It also contains a filler
The porosity according to any one of claims 1 to 3, wherein a ratio of the filler to a total amount of the polyvinylidene fluoride resin and the filler is 1% by mass or more and 30% by mass or less. Quality layer.   The porous layer according to claim 4, wherein the filler has a volume average particle diameter of 0.01 μm or more and 10 μm or less.   A laminate comprising a porous substrate comprising a polyolefin-based resin as a main component and the porous layer according to any one of claims 1 to 5 laminated on at least one surface of the porous substrate. body.   A non-porous material comprising: a porous base material comprising a polyolefin-based resin as a main component; and the porous layer according to any one of claims 1 to 5 laminated on at least one surface of the porous base material. Separator for water electrolyte secondary battery.   A member for a nonaqueous electrolyte secondary battery, wherein the positive electrode, the porous layer according to any one of claims 1 to 5, and the negative electrode are arranged in this order.   A non-aqueous electrolyte secondary battery comprising the porous layer according to claim 1.