JP2017039250A - Laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate that is excellent in shutdown function and ionic conductivity, also has excellent heat resistance, and can prevent the short circuit of a nonaqueous secondary battery.SOLUTION: A laminate has a laminate material of a polyolefin porous film, and a porous base material comprising one or more resin component different from a polyolefin resin, and an electrolyte membrane, the laminate having the electrolyte membrane on at least one side of the laminate material.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laminate useful as a separator for a nonaqueous secondary battery, including an electrolyte membrane, a porous membrane, and a porous substrate.

  Lithium ion non-aqueous secondary batteries can achieve a large energy density in charge and discharge compared to lead batteries and nickel cadmium batteries. Utilizing this characteristic, lithium ion non-aqueous secondary batteries are widely applied to portable electronic devices such as mobile phones and notebook computers. With the widespread use of lithium ion non-aqueous secondary batteries, lithium ion non-aqueous secondary batteries that are particularly lightweight and capable of obtaining high energy density are being developed as power sources for portable electronic devices. Furthermore, there is a strong demand for a lithium ion non-aqueous secondary battery that is small, has a long life, and is highly safe. In addition, it is essential to ensure high safety in applications such as electric vehicles and power storage equipment that are expected to increase in capacity in the future, and the compatibility between the battery performance and reliability of lithium ion non-aqueous secondary batteries will be stronger. Required.

For example, even in a separator that is a partition material between electrodes, there is a strong demand for improvement in reliability. Examples of general characteristics required for the separator include the following three.
1) To have a shutdown function that shuts down the reaction when a predetermined temperature is exceeded in order to prevent internal short circuit 2) To have good electrolyte and ion permeability while holding the electrolyte 3) To improve mechanical strength (Shutdown function is activated and does not break even when the temperature becomes higher than 180 ° C, for example)

  A composite material that can be used as a separator for non-aqueous secondary batteries in which a low-melting-point material has a shutdown function and a high-melting-point material has high-temperature mechanical strength (shape retention function) to satisfy the above characteristics. Has been proposed (Patent Documents 1 and 2).

JP2007-125821 JP2011-108593A

  The separators (composite materials) described in Patent Documents 1 and 2 have a shutdown function. However, there is still room for further improvement in terms of ion conductivity.

  Then, this invention makes it a subject to provide the laminated body which is excellent in a shutdown function and ion conductivity, is excellent also in heat resistance, and can prevent the short circuit of a non-aqueous secondary battery.

  As a result of intensive studies, the present inventors have valence selectivity on at least one surface of a laminate of a polyolefin-based porous membrane and a porous substrate containing at least one resin component different from the polyolefin-based resin. It has been found that by providing an electrolyte membrane, this laminate is excellent in a shutdown function and ion conductivity and excellent in heat resistance, and can prevent a short circuit of a non-aqueous secondary battery. The present invention has been made based on this finding.

That is, the above problem has been solved by the following means.
<1> a laminate of a polyolefin-based porous membrane and a porous substrate containing at least one resin component different from the polyolefin-based resin, and a laminate having an electrolyte membrane,
A laminate having an electrolyte membrane on at least one surface of the laminate.
<2> The melting point (A) of the polyolefin resin component contained in the polyolefin porous membrane is 100 to 180 ° C., and the melting point (B) of the resin component other than the polyolefin resin contained in the porous substrate is as follows. The laminated body as described in <1> which satisfy | fills the relationship represented by Formula (1).
B−A ≧ 50 ° C. (1)
<3> The laminate according to <1> or <2>, wherein the porosity of the polyolefin-based porous membrane and the porous substrate is 20 to 90%.
<4> The laminate according to any one of <1> to <3>, wherein the thickness of the electrolyte membrane is less than 10 μm.

  In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  The laminate of the present invention is excellent in a shutdown function, ion conductivity and heat resistance, and can prevent a short circuit of a non-aqueous secondary battery.

It is a longitudinal cross-sectional view which shows typically the mechanism of an example of the lithium ion non-aqueous secondary battery which concerns on preferable embodiment for applying the laminated body of this invention. It is a longitudinal cross-sectional view which shows the specific structure of an example of the lithium ion non-aqueous secondary battery which concerns on preferable embodiment for applying the laminated body of this invention.

Hereinafter, the present invention will be described in detail.
In addition, description of the structure described below may be made | formed based on typical embodiment and a specific example. However, the present invention is not limited to such an embodiment.

  The laminate of the present invention has a laminate material of a polyolefin-based porous membrane and a porous substrate containing one or more resin components different from the polyolefin-based resin, and an electrolyte membrane is provided on at least one surface of the laminate material. Are stacked. The laminate of the present invention having such a configuration has a low resistance and is excellent in mechanical strength (shape retention function).

[Polyolefin porous film]
The laminated body of this invention can be used as a separator used for a non-aqueous secondary battery (preferably a lithium ion non-aqueous secondary battery). The polyolefin-based porous membrane used in the present invention is preferably composed of a material that has ion permeability and resistance to oxidation and reduction reactions at the contact surface between the positive electrode and the negative electrode.
Further, from the viewpoint of providing a shutdown function for ensuring safety, the resin component used for the polyolefin porous film is preferably a thermoplastic polyolefin resin having a melting point of 100 to 180 ° C. Examples thereof include polyolefin resins comprising polyethylene (preferably LDPE (low density polyethylene) or HDPE (high density polyethylene)) or polypropylene. These may use one kind of resin, but may contain a plurality of resins.
The polyolefin resin used in the present invention may contain a resin other than polyolefin. In the polyolefin resin used in the present invention, the content of polyolefin is preferably 80% by mass or more, and more preferably 90% by mass or more.
The polyolefin-based porous film used in the present invention may contain a resin other than the polyolefin-based resin component. In the polyolefin-based porous membrane used in the present invention, the content ratio of the polyolefin-based resin component is preferably 70% by mass or more, and more preferably 80% by mass or more.

  The melting point of the polyolefin resin used in the present invention is not particularly limited, but is preferably 100 to 180 ° C, more preferably 100 to 160 ° C, and particularly preferably 110 to 140 ° C. When the melting point of the polyolefin resin is within the above range, the shutdown function can be prevented from operating at an excessively low temperature, and safety can be further enhanced.

  The shape of the pores of the polyolefin-based porous membrane used in the present invention is not particularly limited, but is usually circular or elliptical, and the size is 0.05 μm to 100 μm, preferably 0.1 μm to 50 μm. Furthermore, it may be a rod-like or irregular-shaped hole as in the case of making by a stretching method or a phase separation method. The ratio occupied by these gaps (holes), that is, the porosity, is preferably 20% to 90%, and more preferably 35% to 80%.

  Although it does not specifically limit as thickness of the polyolefin-type porous film used for this invention, 1-50 micrometers is preferable, 2-30 micrometers is further more preferable, and 3-20 micrometers is especially preferable. By being in the said range, the mechanical strength and ion permeability of the laminated body of this invention can be kept favorable.

  The method for producing a polyolefin-based porous membrane used in the present invention is not particularly limited. For example, a method of making a polyolefin-based resin porous by stretching it after forming a polyolefin-based resin into a sheet, or sodium hydrogen carbonate, etc. The method of making it porous by mixing the foaming agent of and making it foam is mentioned.

[Porous substrate]
The porous substrate used in the present invention contains one or more resin components different from the polyolefin resin.
Since the porous substrate used in the present invention is required to have mechanical strength (shape retention function) even at a high temperature after the shutdown function of the polyolefin-based porous membrane is activated, other than the polyolefin-based resin contained in the porous substrate. The melting point of the resin component is desirably 50 ° C. or more higher than the melting point of the polyolefin resin component contained in the polyolefin porous film. That is, the melting point (A) of the polyolefin-based resin component contained in the polyolefin-based porous membrane and the melting point (B) of the resin component other than the polyolefin-based resin contained in the porous substrate satisfy the relationship of the following formula (1). preferable.
B−A ≧ 50 ° C. (1)

Moreover, 180 degreeC or more is preferable and, as for melting | fusing point of resin components other than polyolefin resin contained in the porous base material used for this invention, 200 degreeC or more is more preferable. Although there is no restriction | limiting in particular in an upper limit, 400 degrees C or less is preferable and 380 degrees C or less is more preferable.
In addition, melting | fusing point of the said resin used for this invention is based on the measuring method as described in the term of the below-mentioned Example.

  Further, since mechanical strength (shape retention function) is required even at high temperatures, it is preferable that the resin component other than the polyolefin-based resin contained in the porous substrate is contained in an amount of 30% by mass or more, and 60% by mass or more. It is more preferable that the content is 80% by mass or more.

  The resin component different from the polyolefin resin is not particularly limited. For example, polyacetal resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene sulfide resin, polyether ketone resin, fluorine resin, polyether nitrile. Resin, polyetherimide resin, polycarbonate resin, polyphenylene ether resin, polysulfone resin, polyethersulfone resin, polyarylate (fully aromatic polyester) resin, polyimide resin, polyamideimide resin, polyamide resin, aramid (aromatic polyamide) resin, Examples include polyacrylonitrile resin, polyazomethine resin, polyacetylene resin, polypyrrole resin, and cellulose resin. These may be used alone or in combination of two or more.

The shape of the pores of the porous substrate used in the present invention is not particularly limited, but is usually circular or elliptical, and the size is 0.05 μm to 100 μm, preferably 0.1 μm to 50 μm. Furthermore, it may be a rod-like or irregular-shaped hole as in the case of making by a stretching method or a phase separation method. The ratio occupied by these gaps (holes), that is, the porosity is 20% to 90%, preferably 45% to 80%.
When the porosity of the polyolefin-based porous membrane used in the present invention is in the above range and the porosity of the porous substrate used in the present invention is in the above range, the mechanical strength and ions of the laminate are reduced. The permeability can be further improved.
The porosity of the polyolefin-based porous film and the porosity of the porous substrate are determined by the measurement methods described in the Examples section below.

  Although it does not specifically limit as thickness of the porous base material used for this invention, 10-100 micrometers is preferable, 10-70 micrometers is more preferable, 15-50 micrometers is especially preferable. By being in this range, the mechanical strength and ion permeability of the laminate of the present invention can be further improved.

  The method for producing the porous substrate is not particularly limited. For example, (1) after kneading, dissolving, and forming a film with a solvent and a plasticizer having a plasticizing action, and a layer separation assistant, Method of extracting solvent or plasticizer by heat or washing (stretching may be performed if necessary) (2) After the molten resin component is formed into a sheet by extrusion, it is stretched and cracks are generated. (3) If it is a nonwoven fabric, a dry method, a wet method, a spun bond method, a melt blown method, an airlaid method, etc. are mentioned.

[Electrolyte membrane]
For the electrolyte membrane used in the present invention, it is preferable to use a solid electrolyte having valence selectivity (in the case of a lithium ion non-aqueous secondary battery, monovalent lithium ions). A solid electrolyte is a solid electrolyte that can move (permeate) ions inside. From this point of view, it is sometimes called an ion conductive solid electrolyte in consideration of the distinction from an electrolyte salt (supporting electrolyte) described later.

The thickness of the electrolyte membrane used in the present invention is preferably less than 10 μm, more preferably 8 μm or less. Although there is no restriction | limiting in particular in a minimum, 1 micrometer or more is preferable.
When the thickness of the electrolyte membrane is within the above range, valence selectivity and ion permeability can be improved.
In addition, the film thickness of the electrolyte membrane is based on the measurement method described in the section of Examples described later.

An inorganic solid electrolyte and / or an organic solid electrolyte can be used for the electrolyte membrane used in the present invention.
The inorganic solid electrolyte is not particularly limited as long as it has monovalent metal ion conductivity, and generally does not have electron conductivity. Specifically, for example, an inorganic solid electrolyte described in JP-A-2015-88486 can be used.

  In the electrolyte membrane used in the present invention, an organic binder can be used in addition to the inorganic solid electrolyte. The kind of binder is not specifically limited, A general purpose polymer can be used.

The content of the binder in the electrolyte membrane used in the present invention is preferably 0 to 20 parts by mass, more preferably 0.3 to 10 parts by mass, and particularly preferably 1 to 5 parts by mass with respect to 100 parts by mass of the inorganic solid electrolyte. preferable.
By using the binder in the above-mentioned range, it is possible to achieve both improvement of the adhesion of the inorganic solid electrolyte and improvement of the interfacial resistance suppression.

Moreover, when using organic solid electrolyte, if it has the conductivity of a monovalent metal ion, it will not specifically limit. Examples thereof include a polyethylene oxide derivative, a polymer containing this derivative, a polypropylene oxide derivative, a polymer containing this derivative, a polymer containing an ion dissociation group, and a phosphate ester polymer. Examples of the polymer include a latex as described in JP-A-6-36754 and a gel as described in JP-A 2000-182602.
Alternatively, a polymer electrolyte membrane can be obtained by applying a monomer on a laminate and then curing the monomer. A monomer having an oligo (oxyalkylene) group, an ion dissociation group and / or a phosphate group is used. Furthermore, it preferably has a reactive crosslinking group, more preferably has a vinyl group, and still more preferably has an acryloyl group or a methacryloyl group. The monomer may be one type of monomer, but it is preferable to mix several types of monomers.
Specific examples of the monomer structure are shown below, but the present invention is not limited thereto.

[Method for creating laminate]
The manufacturing method of the laminated material of a polyolefin-type porous membrane and a porous base material is not specifically limited. For example, it can be produced by bonding a polyolefin-based porous film produced by stretching to a porous substrate, or forming a film on the porous substrate by applying or melt-extruding a polyolefin-based resin.
Although the manufacturing method of the laminated body of this invention is not specifically limited, It can produce by apply | coating the composition for forming the said electrolyte membrane on the said laminated material.

[Non-aqueous secondary battery]
The laminate of the present invention is preferably used for a nonaqueous secondary battery as a separator. Hereinafter, the non-aqueous secondary battery in which the laminate of the present invention can be used as a separator is also referred to as the non-aqueous secondary battery of the present invention.
Regarding the non-aqueous secondary battery of the present invention, the mechanism of a lithium-ion non-aqueous secondary battery (hereinafter also referred to as “lithium-ion non-aqueous secondary battery of this embodiment”) as a preferred embodiment is schematically illustrated. A description will be given with reference to FIG. The lithium ion non-aqueous secondary battery 10 of the present embodiment includes an electrolyte 5, a positive electrode C (positive electrode current collector 1, positive electrode active material layer 2) capable of inserting and releasing lithium ions, and lithium ion insertion / release. A negative electrode A (negative electrode current collector 3, negative electrode active material layer 4) capable of dissolution and precipitation, and a separator 9 disposed between the positive electrode and the negative electrode are provided. In addition to these essential members, the non-aqueous secondary battery is used in consideration of the purpose of use, the shape of the potential, etc., and includes a current collecting terminal (not shown), an exterior case, etc. (not shown). Also good. If necessary, a protective element may be attached to at least one of the inside of the non-aqueous secondary battery and the outside of the non-aqueous secondary battery. By adopting such a structure, lithium ion exchanges a and b are generated in the electrolytic solution 5, charging α and discharging β can be performed, and operation or storage is performed via the circuit wiring 7 and the operation mechanism 6. be able to. Hereinafter, the configuration of a lithium ion non-aqueous secondary battery which is a preferred embodiment of the present invention will be described in more detail.

[Battery shape]
The battery shape to which the lithium ion non-aqueous secondary battery of this embodiment is applied is not particularly limited, and examples thereof include a bottomed cylindrical shape, a bottomed square shape, a thin shape, a sheet shape, and a paper shape. Any of these may be used.

[Battery components]
The lithium ion non-aqueous secondary battery of this embodiment includes an electrolyte solution 5 as shown in FIG. 1, electrode mixtures C and A for positive and negative electrodes, and a separator 9 as basic members. Hereinafter, each of these members will be described.

[Electrolyte]
The electrolytic solution is generally composed of a supporting electrolyte and a solvent. Lithium salt is mainly used as the supporting electrolyte in the lithium ion non-aqueous secondary battery. The lithium salt which can be used in the nonaqueous secondary battery of the present invention, for _example, in _{LiClO 4, LiBF 4, LiPF 6} , LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 Cl 10, LiOSO 2 C n F 2n + 1 Imide salts represented by fluorosulfonic acid (n is a positive integer of 6 or less), LiN (SO ₂ C _n F _{2n + 1} ) (SO ₂ C _m F _{2m + 1} ) (m and n are each 6 or less positive) ), MeNide salt represented by LiN (SO ₂ C _p F _{2p + 1} ) (SO ₂ C _q F _{2q + 1} ) (SO ₂ C _r F _{2r + 1} ) (p, q and r are positive integers of 6 or less, respectively) And Li salts such as lower aliphatic lithium carboxylate, LiAlCl ₄ , LiCl, LiBr, LiI, lithium chloroborane, lithium tetraphenylborate, etc. These can be used alone or in combination of two or more. Among them, an electrolytic solution in which LiBF ₄ and / or LiPF ₆ is dissolved is preferable. The concentration of the supporting electrolyte is not particularly limited, but is preferably 0.2 to 3 mol per liter of the electrolytic solution.

  Solvents that can be used in the non-aqueous secondary battery of the present invention include propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, methyl formate, methyl acetate, 1,2-dimethoxyethane. , Tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, dioxane, acetonitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, 3- Methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ethyl ether, 1,3-propane sultone, etc. It can be mentioned aprotic organic solvents can be used as a mixture of two or more thereof. Among these, carbonate-based solvents are preferable, and it is particularly preferable to use a mixture of a cyclic carbonate and an acyclic carbonate. As the cyclic carbonate, ethylene carbonate and propylene carbonate are preferable. Moreover, as an acyclic carbonate, diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate are preferable.

As an electrolytic solution that can be used in the non-aqueous secondary battery of the present invention, LiCF ₃ SO ₃ , LiClO ₄ , LiBF are mixed with an electrolytic solution in which ethylene carbonate, propylene carbonate, 1,2-dimethoxyethane, dimethyl carbonate or diethyl carbonate is appropriately mixed. ₄ and / or an electrolytic solution in which LiPF ₆ is dissolved is preferable. In particular, electrolysis comprising at least one salt selected from LiCF ₃ SO ₃ , LiClO ₄ and LiBF ₄ and LiPF ₆ in a mixed solvent of at least one of propylene carbonate or ethylene carbonate and at least one of dimethyl carbonate or diethyl carbonate Liquid is preferred. The amount of the electrolytic solution added to the non-aqueous secondary battery is not particularly limited, and can be determined according to the amount of the positive electrode material and the negative electrode material and the size of the non-aqueous secondary battery.

[Electrode compound]
An electrode mixture is obtained by applying a dispersion of an active material and a conductive agent, a binder, a filler, etc. on a current collector (electrode substrate). In a lithium ion non-aqueous secondary battery, an active material is It is preferable to use a positive electrode mixture which is a positive electrode active material and a negative electrode mixture whose active material is a negative electrode active material. Next, each component in the dispersion (electrode composition) constituting the electrode mixture will be described.

[Positive electrode active material]
The positive electrode active material is preferably one that can reversibly insert and release lithium ions. The material is not particularly limited, and may be a transition metal oxide or an element that can be combined with Li such as sulfur. Among them, it is preferable to use a transition metal oxide, and it is more preferable to have one or more elements selected from the group consisting of Co, Ni, Fe, Mn, Cu, and V as the transition metal element.
Specific examples of the transition metal oxide include (MA) transition metal oxide having a layered rock salt structure, (MB) transition metal oxide having a spinel structure, (MC) lithium-containing transition metal phosphate compound, and (MD And lithium-containing transition metal halide phosphate compounds and (ME) lithium-containing transition metal silicate compounds.

(MA) As specific examples of the transition metal oxide having a layered rock salt structure, LiCoO ₂ (lithium cobaltate [LCO]), LiNi ₂ O ₂ (lithium nickelate) LiNi _0.85 Co _0.10 Al _0.05 O ₂ (nickel cobalt lithium aluminum oxide [NCA]), LiNi _0.33 Co _0.33 Mn _0.33 O ₂ (nickel manganese lithium cobalt oxide [NMC]), LiNi _0.5 Mn _0.5 O ₂ (manganese) Lithium nickelate).
Specific examples of the transition metal oxide having an (MB) spinel structure include LiCoMnO _4, Li ₂ FeMn ₃ O ₈ , Li ₂ CuMn ₃ O ₈ , Li ₂ CrMn ₃ O _{8, and} Li ₂ NiMn ₃ O _8. .
Examples of (MC) lithium-containing transition metal phosphate compounds include olivine-type iron phosphate salts such as LiFePO ₄ and Li ₃ Fe ₂ (PO ₄ ) ₃ , iron pyrophosphates such as LiFeP ₂ O ₇ , LiCoPO _{4 and the} like. And monoclinic Nasicon type vanadium phosphate salts such as Li ₃ V ₂ (PO ₄ ) ₃ (vanadium lithium phosphate).
The (MD) lithium-containing transition metal halogenated phosphate compound, for _example, Li 2 FePO ₄ F such fluorinated phosphorus iron _salt, Li 2 MnPO ₄ hexafluorophosphate manganese salts such as _F, Li 2 CoPO ₄ F Cobalt fluorophosphates such as
Examples of the (ME) lithium-containing transition metal silicate compound include Li ₂ FeSiO ₄ , Li ₂ MnSiO ₄ , Li ₂ CoSiO _{4, and the} like.

In the non-aqueous secondary battery of the present invention, the average particle size of the positive electrode active material used is not particularly limited, but is preferably 0.1 μm to 50 μm. No particular limitation is imposed on the specific surface area, preferably from 0.01m ² / g~50m ² / g by the BET method. Further, the pH of the supernatant when 5 g of the positive electrode active material is dissolved in 100 ml of distilled water is preferably 7 or more and 12 or less.

  In order to make the positive electrode active material have a predetermined particle size, an ordinary pulverizer or classifier is used. For example, a mortar, a ball mill, a vibration ball mill, a vibration mill, a satellite ball mill, a planetary ball mill, a swirling air flow type jet mill, a sieve, or the like is used. The positive electrode active material obtained by the above firing method may be used after washing with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent.

  Although content of a positive electrode active material is not specifically limited, It is preferable that it is 60-98 mass% among 100 mass% of all the solid components of the electrode composition used for this invention, and it is 70-95 mass%. More preferred.

[Negative electrode active material]
As the negative electrode active material, those capable of reversibly inserting and releasing lithium ions are preferable, and there is no particular limitation. Carbonaceous materials, metal oxides such as tin oxide and silicon oxide, metals Examples thereof include composite oxides, lithium alloys such as lithium alone and lithium aluminum alloys, and metals capable of forming alloys with lithium such as Sn and Si.
These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. Of these, carbonaceous materials or lithium composite oxides are preferably used from the viewpoint of reliability.
Further, the metal composite oxide is preferably capable of occluding and releasing lithium, and preferably contains titanium and / or lithium as a constituent component from the viewpoint of high current density charge / discharge characteristics.

  The carbonaceous material used as the negative electrode active material is a material substantially made of carbon. Examples thereof include carbonaceous materials obtained by baking various synthetic resins such as artificial pitches such as petroleum pitch, natural graphite, and vapor-grown graphite, and PAN-based resins and furfuryl alcohol resins. Furthermore, various carbon fibers such as PAN-based carbon fiber, cellulose-based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, dehydrated PVA-based carbon fiber, lignin carbon fiber, glassy carbon fiber, activated carbon fiber, mesophase micro Examples thereof include spheres, graphite whiskers, and flat graphite.

  These carbonaceous materials can be divided into non-graphitizable carbon materials and graphite-based carbon materials depending on the degree of graphitization. Further, the carbonaceous material preferably has the surface spacing, density, and crystallite size described in JP-A-62-222066, JP-A-2-6856, and 3-45473. The carbonaceous material does not need to be a single material, and a mixture of natural graphite and artificial graphite described in JP-A-5-90844, graphite having a coating layer described in JP-A-6-4516, or the like is used. You can also.

  It is preferable that the metal oxide and metal composite oxide which are negative electrode active materials used in the non-aqueous secondary battery of the present invention contain at least one of them. As the metal oxide and metal complex oxide, amorphous oxide is particularly preferable, and chalcogenite, which is a reaction product of a metal element and an element of Group 16 of the periodic table, is also preferably used. The term “amorphous” as used herein means an X-ray diffraction method using CuKα rays, which has a broad scattering band having an apex in the region of 20 ° to 40 ° in terms of 2θ values, and is a crystalline diffraction line. You may have. The strongest intensity of crystalline diffraction lines seen from 2 ° to 40 ° to 70 ° is 100 times the diffraction line intensity at the peak of the broad scattering band seen from 2 ° to 20 °. It is preferable that it is 5 times or less, and it is particularly preferable not to have a crystalline diffraction line.

Among the group of compounds consisting of the above amorphous oxide and chalcogenide, amorphous metal oxides and chalcogenides are more preferable, and elements in Groups 13 (IIIB) to 15 (VB) of the periodic table, Particularly preferred are oxides and chalcogenides composed of one kind of Al, Ga, Si, Sn, Ge, Pb, Sb, Bi or a combination of two or more kinds thereof. Specific examples of preferable amorphous oxides and chalcogenides include, for example, Ga ₂ O ₃ , SiO, GeO, SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₂ O ₄ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , Bi ₂ O ₃ , Bi ₂ O ₄ , SnSiO ₃ , GeS, SnS, SnS ₂ , PbS, PbS ₂ , Sb ₂ S ₃ , Sb ₂ S ₅ , such as SnSiS ₃ may preferably be mentioned. Moreover, these may be a complex oxide with lithium oxide, for example, Li ₂ SnO ₂ .

  In the nonaqueous secondary battery of the present invention, the average particle size of the negative electrode active material used is preferably 0.1 μm to 60 μm. In order to obtain a predetermined particle size, an arbitrary pulverizer or classifier is used. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a swirling air flow type jet mill or a sieve is preferably used. When pulverizing, wet pulverization in the presence of water or an organic solvent such as methanol can be performed as necessary. In order to obtain a desired particle size, classification is preferably performed. The classification method is not particularly limited, and a sieve, an air classifier, or the like can be used as necessary. Classification can be used both dry and wet.

  The chemical formula of the compound obtained by the above firing method can be calculated from an inductively coupled plasma (ICP) emission spectroscopic analysis method as a measurement method and from a mass difference between powders before and after firing as a simple method.

  In the present invention, the negative electrode active material that can be used in combination with the amorphous oxide negative electrode active material centering on Sn, Si, and Ge can occlude and release lithium ions or lithium metal. Preferred examples include carbon materials that can be used, lithium, lithium alloys, and metals that can be alloyed with lithium.

  Although content of a negative electrode active material is not specifically limited, It is preferable that it is 60-98 mass% among 100 mass% of all the solid components of the electrode composition used for this invention, and it is 70-95 mass%. More preferred.

[Conductive material]
The conductive material is preferably an electron conductive material that does not cause a chemical change in the constructed nonaqueous secondary battery, and a normal conductive material can be used as appropriate. Usually, natural graphite (scale-like graphite, scale-like graphite, earth-like graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber and metal powder (copper, nickel, aluminum, silver (Japanese Patent Laid-Open No. Sho 63- , Etc.), etc.), metal fibers or polyphenylene derivatives (described in JP-A-59-20971) can be contained as one kind or as a mixture thereof. Among these, the combined use of graphite and acetylene black is particularly preferable. Among 100% by mass of the total solid component of the electrode composition used in the present invention, the content of the conductive agent is preferably 11 to 50% by mass, and more preferably 2 to 30% by mass. In the case of carbon or graphite, 2 to 15% by mass is particularly preferable.

[Binder]
Examples of the binder include polysaccharides, thermoplastic resins, and polymers having rubber elasticity. Among them, for example, starch, carboxymethylcellulose, cellulose, diacetylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, sodium alginate, Polyacrylic acid, sodium polyacrylate, polyvinyl phenol, polyvinyl methyl ether, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylonitrile, polyacrylamide, polyhydroxy (meth) acrylate, water-soluble polymers such as styrene-maleic acid copolymer, polyvinyl chloride , Polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene (Meth) acrylic acid such as ride-tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, polyvinyl acetal resin, methyl methacrylate, 2-ethylhexyl acrylate (Meth) acrylic acid ester copolymer containing ester, (meth) acrylic acid ester-acrylonitrile copolymer, polyvinyl ester copolymer containing vinyl ester such as vinyl acetate, styrene-butadiene copolymer, acrylonitrile- Butadiene copolymer, polybutadiene, neoprene rubber, fluororubber, polyethylene oxide, polyester polyurethane resin, polyether polyurethane resin, polycarbonate polyurethane Resins, polyester resins, phenolic resins, emulsion (latex) or suspension is preferably such as epoxy resin, polyacrylic acid ester-based latex, carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride is more preferable.

  A binder can be used individually by 1 type or in mixture of 2 or more types. 1-100 mass% is preferable and, as for content of a binder, 100 mass% of all the solid components of the electrode composition used for this invention, 2-10 mass% is more preferable. By being in the said range, the retention strength and cohesion force of an electrode mixture can be raised more, and the increase in electrode volume can be suppressed efficiently.

[Filler]
The electrode mixture may contain a filler. The material forming the filler is preferably a fibrous material that does not cause a chemical change in the non-aqueous secondary battery of the present invention. Usually, fibrous fillers made of materials such as olefin polymers such as polypropylene and polyethylene, glass, and carbon are used. Although the addition amount of a filler is not specifically limited, 0-30 mass% is preferable among 100 mass% of all the solid components of the electrode composition used for this invention.

[Current collector]
As the current collector of the electrode, an electronic conductor that does not cause a chemical change in the nonaqueous secondary battery of the present invention is used. As the current collector of the positive electrode, in addition to aluminum, stainless steel, nickel, titanium, etc., the surface of aluminum or stainless steel is preferably treated with carbon, nickel, titanium, or silver. Among them, aluminum and aluminum alloys are preferable. More preferred.

  As the negative electrode current collector, aluminum, copper, stainless steel, nickel, and titanium are preferable, and aluminum, copper, and a copper alloy are more preferable.

As the shape of the current collector, a film sheet shape is usually used, but a net, a punched material, a lath body, a porous body, a foamed body, a molded body of a fiber group, and the like can also be used. Although it does not specifically limit as thickness of the said electrical power collector, 1 micrometer-500 micrometers are preferable. Moreover, it is also preferable that the current collector surface is roughened by surface treatment.
An electrode mixture of a lithium ion non-aqueous secondary battery is formed by a member appropriately selected from these materials.

[Production of non-aqueous secondary battery]
Various shapes can be applied to the non-aqueous secondary battery of the present invention as described above. A positive electrode active material or a mixture of negative electrode active materials is mainly used after being applied (coated), dried and compressed on a current collector.

  Hereinafter, with reference to FIG. 2, a configuration and a manufacturing method thereof will be described using a bottomed cylindrical lithium ion nonaqueous secondary battery 100 as an example. In a bottomed cylindrical lithium-ion non-aqueous secondary battery, the external surface area for the power generating element to be filled is small, so it is possible to design the design to efficiently escape Joule heat generated by internal resistance during charging and discharging. preferable. Moreover, it is preferable to design so that the filling ratio of the substance having high thermal conductivity is increased and the temperature distribution inside is reduced. In FIG. 2, a bottomed cylindrical lithium ion non-aqueous secondary battery 100 in which a positive electrode sheet 14 and a negative electrode sheet 16 overlapped with each other via a separator 12 are wound and stored in an outer can 18 is illustrated. 2, 20 is an insulating plate, 22 is a sealing plate, 24 is a positive electrode current collector, 26 is a gasket, 28 is a pressure sensitive valve body, and 30 is a current interrupting element. In addition, although the illustration in the enlarged circle has changed hatching in consideration of visibility, each member corresponds to the whole drawing by reference numerals.

  First, a negative electrode active material and a binder or filler used as desired are dissolved in an organic solvent to prepare a slurry-like or paste-like negative electrode mixture. The obtained negative electrode mixture is uniformly applied over the entire surface of both surfaces of the metal core as a current collector, and then the organic solvent is removed to form a negative electrode mixture layer. Further, the laminate of the current collector and the negative electrode composite material layer is rolled with a roll press or the like to prepare a predetermined thickness to obtain a negative electrode sheet (electrode sheet). At this time, the coating method of each agent, the drying of the coated material, and the method of forming the positive and negative electrodes may be in accordance with conventional methods.

  In the present embodiment, a cylindrical lithium ion non-aqueous secondary battery has been described as an example. However, the present invention is not limited to this, and for example, a positive / negative electrode sheet manufactured by the above-described method may be interposed via a separator. After being stacked, they are processed into a sheet-like lithium ion non-aqueous secondary battery as it is, or after being folded and inserted into a rectangular can, the can and the sheet are electrically connected, and then the electrolyte is injected. The rectangular lithium ion non-aqueous secondary battery may be formed by sealing the opening using a sealing plate.

  In any embodiment, the safety valve can be used as a sealing plate for sealing the opening. Moreover, you may equip a sealing member with various safety elements other than a safety valve. For example, a fuse, bimetal, PTC element, or the like is preferably used as the overcurrent prevention element.

  In addition to the safety valve, as a countermeasure against the increase in internal pressure of the battery can, a method of cutting the battery can, a method of cracking the gasket, a method of cracking the sealing plate, or a method of cutting the lead plate can be used. Further, the charger may be provided with a protection circuit incorporating measures against overcharge and overdischarge, or may be connected independently.

  For the can and lead plate, a metal or alloy having electrical conductivity can be used. For example, metals such as iron, nickel, titanium, chromium, molybdenum, copper, and aluminum, or alloys thereof are preferably used.

  As a welding method for the cap, can, sheet, and lead plate, a normal method (eg, direct current or alternating current electric welding, laser welding, ultrasonic welding) can be used. As the sealing agent for sealing, a compound such as asphalt or a mixture can be used.

[Applications of non-aqueous secondary batteries]
Non-aqueous secondary batteries, called lithium batteries, include secondary batteries that use lithium storage and release for charge and discharge reactions (lithium ion non-aqueous secondary batteries), and secondary batteries that use lithium deposition and dissolution (lithium). Metal non-aqueous secondary battery). In the present invention, application as a lithium ion non-aqueous secondary battery is preferable.
Since the nonaqueous secondary battery of the present invention can produce a secondary battery with good cycle performance, it is applied to various applications. The application mode is not particularly limited. For example, when installed in an electronic device, a notebook computer, pen input personal computer, mobile personal computer, electronic book player, mobile phone, cordless phone, pager, handy terminal, mobile fax, mobile copy , Portable printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, minidisc, electric shaver, transceiver, electronic notebook, calculator, memory card, portable tape recorder, radio, backup power supply, memory card, etc. . Other consumer products include automobiles, electric vehicles, motors, lighting equipment, toys, game equipment, road conditioners, watches, strobes, cameras, medical equipment (such as pacemakers, hearing aids, and shoulder grinders). Furthermore, it can be used for various military use and space use. Moreover, it can also combine with a solar cell.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not construed as being limited thereto. Unless otherwise specified, parts and% are based on mass.

[Measuring method]
(1) Melting point The melting point of the resin was measured according to JIS K 7121 using a high-sensitivity differential scanning calorimeter manufactured by SII Nano Technology, Inc., trade name: X-DSC7000, and the area of the melting peak according to JIS K7122. I asked for it. In the case of a series of a plurality of overlapping peaks, the peak area was determined using this as one melting peak, and the higher peak height was taken as the melting point.
(2) Porosity Cross-sectional observation is performed with a scanning electron microscope (manufactured by Hitachi High-Technology Corporation, product name: S3400N) and an optical microscope (manufactured by Olympus, product name: BX-51), and the area of the void portion and the resin portion. The ratio was defined as porosity.
(3) Film thickness Cross-sectional observation is performed with a scanning electron microscope (manufactured by Hitachi High-Technology Corporation, product name: S3400N) and an optical microscope (manufactured by Olympus, product name: BX-51), and the thickness of each layer constituting the laminate. Was measured.

Example 1
[Preparation of separator]
Nonwoven fabric N1 (polyester, porosity 68%, thickness 30 μm was used as the porous substrate. Resin P1 was extruded and laminated on nonwoven fabric N1, and a polyolefin-based porous film was laminated on nonwoven fabric N1 (on the porous substrate). The laminated material obtained was extruded under the conditions described in Japanese Patent No. 3590680. The resin P1 was 95 parts by mass of LDPE (low density polyethylene, density 0.94, MFR = 3) as a foaming agent. A master batch (trade name: Polyslen EE 205, manufactured by Eiwa Kasei Kogyo Co., Ltd.) is added 5 parts by mass, where MFR represents melt flow rate (g / 10 min) and measured by the method of JIS K 7210. The LDPE used in the foaming agent master batch had a specific gravity of 0.94 and MFR = 4, and the thickness of the obtained laminate was 50 μm.

Next, an electrolyte membrane having a film thickness of 5 μm was formed on the opposite surface of the polyolefin-based porous membrane of the laminate material to the surface in contact with the porous substrate as described below to produce a laminate.
4: 3: 1 (molar ratio) of the above monomer 1-1, monomer 2-2, monomer 3-3 mixture 16.5 parts by weight, LiPF ₆ 11 parts by weight, 2,2′-azobis (methylisobutyrate) Rate) 1.1 parts by mass, ethylene carbonate: diethyl carbonate = 2: 8 (mass ratio) 71.4 parts by mass were mixed to obtain a uniform solution. This solution was applied onto the surface of the laminate using an applicator (trade name: Baker Applicator, manufactured by Yoshimi Seiki Co., Ltd.), and then heated at 70 ° C. for 5 minutes to obtain the desired laminate.

[Production of non-aqueous secondary battery]
The positive electrode is active material: LiNi _0.33 Mn _0.33 Co _0.33 O ₂ (NMC) 85% by mass, conductive aid: carbon black 7.5% by mass, binder: PVDF (polyvinylidene fluoride) 7.5% by mass The negative electrode was made of active material: 85% by mass of graphite, conductive auxiliary agent: 7.5% by mass of carbon black, and binder: 7.5% by mass of PVDF (polyvinylidene fluoride). The electrolyte solution is ethylene carbonate: diethyl carbonate = 2: 8 (mass ratio) 87.5 parts by mass with a small amount of LiBF ₄ 0.4 parts by mass and LiPF ₆ 12.1 parts by mass so that the liquid temperature does not exceed 30 ° C. It was prepared by dissolving each one. A nonaqueous secondary battery (2032 type coin battery) was produced using the positive electrode, the negative electrode, the electrolytic solution and the laminate as a separator.

[Initialization of 2032 type coin battery]
Charged at a constant current of 0.2 C until the battery voltage reaches 4.3 V (positive electrode potential 4.4 V) in a thermostat at 30 ° C., and then charged until the battery voltage reaches a current value of 0.12 mA at a constant voltage of 4.3 V. Went. However, the upper limit of the time was 2 hours. Next, 0.2 C constant current discharge was performed until the battery voltage became 2.75 V in a 30 ° C. constant temperature bath. This operation was repeated twice. The following items were evaluated using the 2032 type coin battery produced by the above method. The results are shown in Table 1 below.

[Measurement of ion conductivity]
The 2032 type coin battery was subjected to AC impedance measurement up to a voltage amplitude of 5 mV and a frequency of 1 MHz to 1 Hz in a constant temperature bath at 30 ° C., thereby determining the resistance in the film thickness direction of the separator and calculating by the following formula.

Ionic conductivity (mS / cm) = 1000 × film thickness (cm) / (resistance (Ω) × area (cm ² ))

  An ionic conductivity of 0.8 mS / cm or more was designated as A: very good, 0.2 or more and less than 0.8 as B: good, and less than 0.2 as C: poor.

[Cycle test and observation of dendrite generation]
The 2032 type coin battery is charged at a constant current of 0.7 C in a thermostatic chamber at 30 ° C. until the battery voltage becomes 4.3 V, and then charged until the current value becomes 0.12 mA at a constant voltage of the battery voltage of 4.3 V. went. However, the upper limit of the time was 2 hours. A cycle in which 0.5C constant current discharge of this 2032 type coin battery was performed in a thermostat at 30 ° C. until the battery voltage reached 2.75 V was repeated 300 times. The presence or absence of lithium dendrite generation on the negative electrode surface after the cycle test was confirmed by visual observation.

[Evaluation of shutdown function and heat resistance test]
The 2032 type coin battery initialized above was charged at a constant current of 0.7 C until the battery voltage in the thermostatic bath at 30 ° C. reached 4.3 V, and then discharged while immersed in a thermostatic bath with a temperature adjustment function. The electrical resistance value was measured, and the shutdown function and heat resistance were evaluated by comparing with the resistance value after maintaining the temperature rise below.
-Shutdown function-
When the temperature rises from 30 ° C. at 30 ° C./min and is held at 130 ° C. for 1 minute, if the resistance value increases, A: shut down function is good, and if the resistance value does not change, B: judge that the shutdown function is bad did.
-Heat resistance-
The temperature was raised from 30 ° C. at 30 ° C./minute, held at 130 ° C. for 1 minute, then again heated at 30 ° C./minute, held at 180 ° C. for 1 minute, then heated again, and at 200 ° C. for 1 minute. When held, if resistance value did not change, A: good heat resistance, resistance value did not change at 180 ° C, but if resistance value dropped significantly at 200 ° C, B: heat resistance was slightly insufficient When the resistance value significantly decreased at 180 ° C., it was determined that C: insufficient heat resistance. The results are shown in Table 1.

(Examples 2-6, Comparative Examples 1-4)
As shown in Table 1, a separator and a 2032 coin cell were prepared in the same manner as in Example 1 except that a porous substrate, a polyolefin-based porous membrane, and an electrolyte membrane were used, and the 2032 coin cell was tested. went. In Table 1, the unit of porosity is%, the unit of film thickness is μm, and the unit of melting point is ° C., which is omitted in the table.
The materials used in Table 1 are shown below.
N2: Nonwoven fabric made of polyphenylene sulfide (PPS) N3: Nonwoven fabric made of cellulose N4: Nonwoven fabric made of polypropylene N5: Nonwoven fabric made of polyethylene / polyester (mixing ratio = 70/30 mass%)
P2: Polyester porous membrane

  In Examples 1-6, the non-aqueous secondary battery uses the laminate of the present invention as a separator, has good ionic conductivity, no dendrites are observed, and has a shutdown function at high temperatures and heat resistance. outstanding. As a result, the laminate of the present invention is excellent in ion conductivity, shutdown function, and heat resistance, and can be used as a separator for non-aqueous secondary batteries to prevent abnormal temperature rise of non-aqueous secondary batteries. It is clear that it is excellent.

  On the other hand, from the result of Comparative Example 1, when the porous base material does not contain a resin component different from the polyolefin resin and the melting point is low, the film melts and the electrodes are short-circuited, and suddenly reaches 400 to 500 ° C. There is a possibility that the battery temperature rises, and there is a safety concern.

  The non-aqueous secondary battery (Comparative Example 2) having a porous film using a resin component having a high melting point instead of the polyolefin-based resin and the non-aqueous secondary battery not having the polyolefin-based porous film (Comparative Example 3) The shutdown function was bad. From this result, in the nonaqueous secondary batteries as in Comparative Examples 2 and 3, it is not possible to prevent the permeation of ions when the temperature rises abnormally. In order to ensure safety, it is necessary to shut down below the ignition temperature of lithium metal, and in Comparative Examples 2 and 3, there is a concern about safety.

  From the results of Comparative Example 4, it can be seen that dendrites are generated without an electrolyte membrane, and there is a possibility of short-circuiting between electrodes.

C positive electrode (positive electrode composite)
1 Positive electrode conductive material (current collector)
2 Positive electrode active material layer A Negative electrode (negative electrode composite)
3 Negative electrode conductive material (current collector)
4 Negative electrode active material layer 5 Electrolyte 6 Operating mechanism 7 Circuit wiring 9 Separator 10 Lithium ion non-aqueous secondary battery 12 Separator 14 Positive electrode sheet 16 Negative electrode sheet 18 Exterior can 20 also serving as negative electrode Insulating plate 22 Sealing plate 24 Positive electrode current collector 26 Gasket 28 Pressure sensitive valve element 30 Current interrupting element 100 Bottomed cylindrical shape lithium non-aqueous secondary battery

Claims (4)

A laminate comprising a polyolefin-based porous membrane and a porous substrate containing one or more resin components different from the polyolefin-based resin, and a laminate having an electrolyte membrane,
A laminate having the electrolyte membrane on at least one surface of the laminate. The melting point (A) of the polyolefin-based resin component contained in the polyolefin-based porous membrane is 100 to 180 ° C., and the melting point (B) of the resin component other than the polyolefin-based resin contained in the porous substrate is represented by the following formula: The laminated body of Claim 1 which satisfy | fills the relationship represented by (1).
B−A ≧ 50 ° C. (1)   The laminate according to claim 1 or 2, wherein the porosity of the polyolefin-based porous membrane and the porous substrate is 20 to 90%.   The laminated body according to any one of claims 1 to 3, wherein a thickness of the electrolyte membrane is less than 10 µm.

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