JP2003040999A - Fully aromatic polyamide, fully aromatic polyamide porous film and separator for nonaqueous electrolytic solution secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fully aromatic polyamide which hardly causes the decomposition even at a high voltage, a fully aromatic polyamide porous film using it, a separator for a nonaqueous electrolytic solution secondary battery containing the film and a nonaqueous electrolytic solution secondary battery containing the separator. SOLUTION: [1] The fully aromatic polyamide having a homo value of -8.5 eV or less of all nitrogen atoms in a molecular model, which is determined by the molecular orbital method calculation. [2] The fully aromatic polyamide porous film comprising the fully aromatic polyamide in [1]. [3] The separator for the nonaqueous electrolytic solution secondary battery containing the film in [2]. [4] The nonaqueous electrolytic solution secondary battery containing the separator in [3].

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a wholly aromatic polyamide, a wholly aromatic polyamide porous film using the same, a method for producing the same, and a non-aqueous electrolyte secondary battery using the wholly aromatic polyamide porous film. And a non-aqueous electrolyte secondary battery including the separator.

[0002]

2. Description of the Related Art A wholly aromatic polyamide, a porous film made of wholly aromatic polyamide, and a separator using the same are disclosed in US Pat. No. 5,856,426.

[0003]

However, the above-mentioned known wholly aromatic polyamide has a high voltage when it is used as a porous film and used as a separator of a lithium secondary battery having a high operating voltage of about 3 V or more. When applied, there was a problem that the discoloration was large and the alteration was large. The object of the present invention is a wholly aromatic polyamide which is not deteriorated even when a high voltage is applied, a wholly aromatic polyamide porous film using the same and a method for producing the same, and a non-aqueous electrolysis containing the wholly aromatic polyamide porous film. A liquid secondary battery separator, and a non-aqueous electrolyte secondary battery including the separator are provided.

[0004]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that all nitrogen atoms of a wholly aromatic polyamide having a molecular model of the wholly aromatic polyamide are , HO obtained by molecular orbital method calculation
The inventors have found that a wholly aromatic polyamide having an MO (maximum occupied molecular orbital energy) value of a specific value or less has little deterioration even when a high voltage is applied, and has completed the present invention.

That is, the present invention is [1] a wholly aromatic polyamide, in which all nitrogen atoms contained in a molecular model of the wholly aromatic polyamide are calculated by the molecular orbital method calculation.
OMO (maximum occupied molecular orbital energy) value is -8.5e
The present invention relates to a wholly aromatic polyamide having V or less. The present invention also relates to [2] a wholly aromatic polyamide porous film comprising the wholly aromatic polyamide according to [1] above. The present invention also relates to [3] the method for producing a wholly aromatic polyamide porous film according to the above [2], which comprises the following steps (a) to (d). (A) A step of forming a film-like product from a solution containing a polar amide solvent or a polar urea solvent, the wholly aromatic polyamide of [1] above, and a chloride of an alkali metal or an alkaline earth metal. (B) A step of precipitating wholly aromatic polyamide from the film-like material obtained in step (a). (C) A step of removing the solvent and the chloride of the alkali metal or the alkaline earth metal from the film-like material on which the wholly aromatic polyamide obtained in the step (b) is deposited. (D) Step of Drying Membrane Obtained in Step (c) The present invention also provides [4] a separator for a non-aqueous electrolyte secondary battery, which comprises the wholly aromatic polyamide porous film of [2] above. It is related. Furthermore, the present invention provides [5] above [4]
The present invention relates to a non-aqueous electrolyte secondary battery including the non-aqueous electrolyte battery separator.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The wholly aromatic polyamide of the present invention is
The HOMO (highest occupied molecular orbital energy) value of all nitrogen atoms of the molecular model of the wholly aromatic polyamide obtained by the molecular orbital method calculation is −8.5 eV or less.

In the present invention, the wholly aromatic polyamide means a polyamide, and at least 85 mol% of the amide bonds of the polyamide are directly bonded to the aromatic ring.

In the present invention, the content of wholly aromatic polyamide is
The child model is a structure of the wholly aromatic polyamide represented by the following formula.
Modeled in the form of the plane structural formula shown in (1)
Say. Ar₁-X₁-Ar₂-X₂-Ar₃-X₃-Ar_Four-X_Four-Ar_Five-X_Five-Ar₆-X₆-Ar₇-X₇-Ar₈-X₈-Ar₉(1) Ar here₁, Ar₉Are each independently a monovalent aromatic ring
Yes, the same as the aromatic ring at the end of the structure of wholly aromatic polyamide.
The same aromatic ring, and the terminal aromatic ring has a substituent
In the case of Ar₁, Ar₉Has the substituent.
Ar₂~ Ar₈Are each independently a divalent aromatic ring,
X₁~ X₈Are each independently -CONH- or-
An amide bond represented by NHCO-, Ar ₂~ A
r₈, X₁~ X₈Is selected according to the structure of wholly aromatic polyamide.
Barely placed. Polymers of wholly aromatic polyamide structure
If the aromatic ring in the chain has a substituent, A in the molecular model
r₂~ Ar₈Have substituents depending on their number and position.
Let The structure of wholly aromatic polyamide is usually
Raw materials and reaction conditions used to produce aromatic polyamides
The structure deduced from

HO of the nitrogen atom which the above-mentioned molecular model has
The MO (maximum occupied molecular orbital energy) value is obtained by the following procedures (I) and (II) by the molecular orbital method calculation. (I) Commercial program MOPAC93 (JJP Stewart, Fuji
Tsutsu Limited, Tokyo, Japan (1993)) is used to determine the stable structure of the molecular model by the AM1 method. (II) Using the stable structure obtained in (I), Gaussi
In an98, an orbital diagram of the molecular model is created by one-point calculation by the AM1 method, and HOMO values of all nitrogen atoms of the molecular model are obtained from the orbital diagram.

The lower the HOMO value of the nitrogen atom obtained as a result of the calculation, the more stable the nitrogen atom is in terms of energy,
It shows high electrochemical oxidation resistance. Molecular model H
When at least one of the OMO values is larger than -8.5 eV, when a high voltage, for example, a voltage of 3 V or more is applied, the wholly aromatic polyamide tends to be discolored and deteriorated.

The wholly aromatic polyamide of the present invention is not limited as long as it satisfies the above conditions, and examples thereof include para-oriented wholly aromatic polyamide, meta-oriented wholly aromatic polyamide, and ortho-oriented wholly aromatic polyamide. The para-oriented wholly aromatic polyamide is preferable from the viewpoint of heat resistance, high strength, and dimensional stability. The aromatic ring of the wholly aromatic polyamide may have an electron-withdrawing substituent such as halogen and an electron-donating substituent such as lower alkyl.

In the present invention, the para-oriented aromatic polyamide has a structure obtained by condensation polymerization of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid dihalide, and the amide bond is an amide bond of the aromatic ring. With respect to the para position or an orientation position (for example, 4,
It is essentially composed of repeating units such as 4'-biphenylene, 1,5-naphthalene, 2,6-naphthalene, etc., which are bonded in an orientation position extending coaxially or parallel to the opposite direction. Specifically, poly (paraphenylene terephthalamide), poly (parabenzamide), poly (4,
4'-benzanilide terephthalamide), poly (paraphenylene-4,4'-biphenylene dicarboxylic acid amide), poly (paraphenylene-2,6-naphthalene dicarboxylic acid amide), poly (2-chloro-paraphenylene terephthalamide) ), Para-phenylenediamine / 2,6
Examples thereof include those having a para orientation type or a structure conforming to the para orientation type such as a copolymer of dichloroparaphenylenediamine / terephthalic acid dichloride. Further, a part of the amino bond may be replaced with the meta position of the aromatic ring or an orientation position corresponding thereto, or the ortho position of the aromatic ring or an orientation position corresponding thereto.

The meta-oriented wholly aromatic polyamide has a structure obtained by condensation polymerization of a meta-oriented aromatic diamine and a meta-oriented aromatic dicarboxylic acid dihalide, and the amide bond is at the meta position of the aromatic ring or its equivalent. And substantially consists of repeating units bonded at different orientations, and examples thereof include poly (metaphenylene isophthalamide).

As the ortho-oriented wholly aromatic polyamide,
For example, poly (orthophenylene phthalamide), poly (orthophenylene isophthalamide), poly (orthophenylene terephthalamide) and the like can be mentioned.

Of these, those having substantially no amino group in the aromatic ring at the end of the polymer chain are less likely to deteriorate,
preferable. It can be confirmed by, for example, ¹ H-NMR method that the aromatic ring at the terminal of the polymer does not have an amino group. Among them, the aromatic ring at the end of the polymer chain does not substantially have an amino group, and the polymer end and / or
Further, it is more preferable that the aromatic ring in the polymer chain has an electron-withdrawing substituent, and the aromatic ring at the end of the polymer chain does not substantially have an amino group, and the polymer end and the polymer It is more preferable that the aromatic ring in the chain has an electron-withdrawing substituent.

Here, examples of the electron-withdrawing substituent include a carboxyl group, an alkoxycarbonyl group, a nitro group, a cyano group and a halogen atom, and a halogen atom is preferable. As the halogen atom, chlorine atom, fluorine atom and the like are preferable, and chlorine atom is particularly preferable. The number of electron-withdrawing substituents is usually 1 in the aromatic ring at the polymer end.
-5, usually 1-4 in the aromatic ring in the polymer chain.

The wholly aromatic polyamide of the present invention can be produced by combining known methods depending on the structure. For example, among the wholly aromatic polyamides having substantially no amino group in the aromatic ring at the terminal of the polymer, those belonging to the para-oriented wholly aromatic polyamide can be produced, for example, by the method described below.

That is, in a polar amide solvent or polar urea solvent in which an alkali metal or alkaline earth metal chloride is dissolved, 0 to 0.1 mol of an aromatic monoamine and 0.94 to 0. Into a solution obtained by dissolving 99 mol and 1.0 mol of para-oriented aromatic dicarboxylic acid halide 1.0
0 mol is added and condensation polymerization is performed at a temperature of −20 ° C. to 50 ° C. to produce a polymerization solution of wholly aromatic polyamide.

The amount of the alkali metal or alkaline earth metal chloride in the polymerization solution is usually 1 to 10% by weight, preferably 2 to 8% by weight. If the chloride of the alkali metal or alkaline earth metal is less than 1% by weight, the solubility of the wholly aromatic polyamide tends to be insufficient, and if it exceeds 10% by weight, the chloride of the alkali metal or alkaline earth metal is It tends to be difficult to dissolve in a polar amide solvent or a polar urea solvent. Further, the amount of the chloride of the alkali metal or the alkaline earth metal in the polymerization solution is determined with respect to the amount of wholly aromatic polyamide (amide group in wholly aromatic polyamide). That is, the amount of the chloride added to the polymerization system is 0.5 to 6 per 1.0 mol of the amide group produced by condensation polymerization.
The range of 0 mol is preferable, and the range of 1.0 to 4.0 mol is more preferable. If the chloride content is less than 0.5 mol, the solubility of the wholly aromatic polyamide produced tends to be insufficient.
If it exceeds 6.0 mol, the amount of chloride dissolved in the solvent tends to be substantially exceeded.

Specific examples of the chloride of the alkali metal or alkaline earth metal include lithium chloride and calcium chloride.

The concentration of wholly aromatic polyamide in the polymerization solution is usually 1 to 15% by weight, preferably 2 to 10% by weight. If the concentration of wholly aromatic polyamide is less than 1% by weight, the productivity is remarkably reduced, which is industrially disadvantageous. If the wholly aromatic polyamide exceeds 15% by weight, the wholly aromatic polyamide tends to precipitate and it is difficult to form a stable polymerization solution.

Para-oriented aromatic diamines include para-phenylenediamine, 4,4'-diaminobiphenyl and 2
-Methyl-paraphenylenediamine, 2-chloro-paraphenylenediamine, 2,6-dichloro-paraphenylenediamine, 2,6-naphthalenediamine, 1,5-naphthalenediamine, 4,4'-diaminobenzanilide, 3, 4'-diamino diphenyl ether etc. can be mentioned. Aromatic diamines may be used alone or as a mixture of two for use in condensation polymerization.

Examples of the para-oriented aromatic dicarboxylic acid dihalide include terephthalic acid dichloride, biphenyl-4,
4'-dicarboxylic acid chloride, 2-chloroterephthalic acid dichloride, 2,5-dichloroterephthalic acid dichloride, 2-methylterephthalic acid dichloride, 2,6
-Naphthalenedicarboxylic acid chloride, 1,5-naphthalenedicarboxylic acid chloride and the like. The aromatic dicarboxylic acid dihalides may be used alone or in combination for condensation polymerization.

Examples of aromatic monoamines include 2-
Halogenated anilines such as chloraniline, 3-chloroaniline and 4-chloroaniline; anisidine, toluidine, phenetidine, aniline and the like can be mentioned. Halogenated aniline is preferred, and 2-chloroaniline and 3-chloroaniline are particularly preferred. When an aromatic monoamine is used, the aromatic ring at the end of the polymer chain becomes an aromatic ring having a substituent which the aromatic monoamine has. When the aromatic monoamine is not used, since the aromatic dicarboxylic acid dihalide is in excess with respect to the aromatic diamine,
The polymer chain terminal group is usually a carboxyl group.

The polymerization is usually carried out in a polar amide solvent or a polar urea solvent. Examples of polar amide solvents include N, N-dimethylformamide, N, N-
Examples thereof include dimethylacetamide and N-methyl-2-pyrrolidone. Examples of polar urea solvents include N, N,
N ', N'- tetramethyl urea is mentioned. Among these, polar amide solvents are preferable, and N-methyl-2-pyrrolidone is particularly preferable.

The wholly aromatic polyamide of the present invention can be isolated from the above-mentioned polymerization solution by a known operation such as a reprecipitation method. The intrinsic viscosity of the wholly aromatic polyamide is usually 1.0 to 3.0 dl / g, preferably 1.5 to 2.8 d.
1 / g. If the intrinsic viscosity is less than 1.0 dl / g, sufficient film strength tends not to be obtained. When the intrinsic viscosity exceeds 3.0 dl / g, it is difficult to form a stable polymerization solution, and wholly aromatic polyamide tends to precipitate to make it difficult to form a film.

Next, the wholly aromatic polyamide porous film of the present invention will be described. The wholly aromatic polyamide porous film of the present invention comprises the wholly aromatic polyamide of the present invention. The method for producing the wholly aromatic polyamide porous film of the present invention is not particularly limited, but for example, it can be produced by the following method.

That is, a wholly aromatic polyamide porous film can be produced by the following steps (a) to (d). (A) A step of forming a film-like material from a solution containing a polar amide-based solvent or polar urea-based solvent, a wholly aromatic polyamide, and an alkali metal or alkaline earth metal chloride. (B) A step of precipitating wholly aromatic polyamide from the film material. (C) A step of removing the solvent and the chloride of the alkali metal or the alkaline earth metal from the film-like material in which the wholly aromatic polyamide obtained in the step (b) is deposited. (D) A step of drying the film-like material obtained in step (c).

The solution used in step (a) is, for example,
The product produced by the above operation may be used as it is, or may be prepared by dissolving the isolated wholly aromatic polyamide and the chloride of alkali metal or alkaline earth metal in a solvent. Suitable examples of the polar amide solvent or polar urea solvent used in step (a), the intrinsic viscosity and content of the wholly aromatic polyamide, and the chloride of the alkali metal or alkaline earth metal and the content thereof are preferred examples. Including, the same as in the case of the above-described example of the method for producing a wholly aromatic polyamide.

In the step (a), when a film-like material is formed, the wholly aromatic polyamide solution is cast on a substrate such as a glass plate or a polyester film to maintain the shape of the film-like material. It can be done by As a casting method, various methods such as a bar coater or a method of extruding from a T-die onto a substrate can be appropriately adopted.

In step (b), wholly aromatic polyamide is precipitated from the film-form material obtained in step (a). As a method for precipitating a wholly aromatic polyamide, for example, a method of holding the filmy material at a temperature of 20 ° C. or higher / humidity of 40% or higher, a polar amide solvent or a polar urea solvent in an amount of 0 to 70 is used.
A method in which the wholly aromatic polyamide is precipitated by immersing in a coagulating liquid containing 30% by weight of water and 30 to 100% by weight of water may be used.

In the step (c), the solvent and the chloride of the alkali metal or the alkaline earth metal are removed from the film-like material obtained by the step (b) on which the wholly aromatic polyamide is deposited. As a removal method, for example, there is a method of immersing the film-like material in an aqueous solution or an alcohol-based solution to elute the solvent and chloride.

In the step (d), the film-like material from which the solvent and the chloride are removed in the step (c) is then dried to produce the desired porous film. The drying method is not particularly limited, and various known methods can be used.

Next, the separator for a non-aqueous electrolyte secondary battery of the present invention will be described. The separator for a non-aqueous electrolyte secondary battery of the present invention is characterized by including the wholly aromatic polyamide porous film of the present invention.

When the wholly aromatic polyamide porous film of the present invention is used as a separator for a non-aqueous electrolyte secondary battery, the size of the voids, or, if the voids can be approximated to a sphere, the diameter of the sphere (hereinafter, It may be called the hole diameter)
Is preferably 3 μm or less, more preferably 1 μm or less. When the average size of the voids or the pore size exceeds 3 μm, there is a possibility that a short circuit may occur when the carbon powder, which is the main component of the positive electrode or the negative electrode, or its small pieces fall off. The porosity of the porous film is 30 to 80.
Volume% is preferable, More preferably, it is 40 to 70 volume%.
Is. If the porosity is less than 30% by volume, the amount of electrolyte retained is small, and if it exceeds 80% by volume, the strength of the porous film tends to be insufficient. The wholly aromatic polyamide porous film has a thickness of preferably 1 to 30 μm, more preferably 2 to 20 μm. If the thickness is less than 1 μm, the effect on safety as the porous film may be insufficient, and if it exceeds 30 μm, the thickness of the separator for a non-aqueous electrolyte secondary battery is too large to achieve high electric capacity. It may be difficult to do. The wholly aromatic porous film may contain particles of an inorganic compound and the like. The inorganic compound to be contained may be any one that has electrochemical oxidation resistance and is inert to the electrolytic solution. Specific examples include aluminum oxide and calcium carbonate, but the present invention is not limited thereto.

In the separator for a non-aqueous electrolyte secondary battery of the present invention, a laminate of the wholly aromatic polyamide porous film of the present invention and a porous film having a shutdown function (hereinafter sometimes referred to as a shutdown layer) What has a structure (hereinafter sometimes referred to as a laminated separator) is
It is preferable from the viewpoint of safety. Here, the "shutdown function" means that when the temperature inside the battery rises due to a short circuit between the positive electrode and the negative electrode in the battery, the porous film such as the polyolefin layer softens and becomes non-porous to insulate between the electrodes. It is a function of suppressing the temperature rise.

In the laminated separator, the preferable pore diameter and porosity of the wholly aromatic polyamide porous film are the same as those described above.

The shutdown layer is not particularly limited, but is usually a porous film made of a thermoplastic resin. The size of the voids, the porosity, and the thickness of the shutdown layer are specifically the size of the voids, or the diameter of the spheres when the voids can be approximated to a sphere (hereinafter, sometimes referred to as a pore diameter), It is preferably 3 μm or less, more preferably 1 μm or less. The average size or pore diameter of the voids is 3μ
If it exceeds m, problems such as easy short circuit may occur when the carbon powder, which is the main component of the positive electrode or the negative electrode, or its small pieces fall off. The porosity of the shutdown layer is preferably 30 to 80% by volume, more preferably 4
It is 0 to 70% by volume. When the porosity is less than 30% by volume, the amount of the electrolytic solution retained may be small, and when it exceeds 80%, the strength of the shutdown layer tends to be insufficient, and the shutdown function may be deteriorated. The thickness of the shutdown layer is preferably 3 to 30 μm,
More preferably, it is 5 to 20 μm. The thickness is 3 μm
If the amount is less than 30 μm, the shutdown function may be insufficient, and if it exceeds 30 μm, the thickness of the separator for a non-aqueous electrolyte secondary battery including the wholly aromatic porous film of the present invention is too large, resulting in high electric capacity. It may not be achieved.

The thermoplastic resin forming the shutdown layer is preferably a thermoplastic resin which is softened at 80 to 180 ° C. to close the porous voids and does not dissolve in the electrolytic solution. Specific examples include polyolefin and thermoplastic polyurethane. As the polyolefin, at least one thermoplastic resin selected from polyethylene such as low-density polyethylene, high-density polyethylene, ultra-high-molecular-weight polyethylene, polypropylene and the like is more preferable.

The porosity of the above-mentioned shutdown layer or wholly aromatic polyamide porous film is 10 per side.
Cut into squares of cm, weight (Wg) and thickness (Dc
m) is measured, the weight of the material in the sample is calculated, the weight of each material (Wi) is divided by the true specific gravity, the volume of each material is calculated, and the porosity (volume%) is calculated from the following formula. Ask for.

Porosity (%) = 100-{(W1 / true specific gravity 1) + (W2 / true specific gravity 2) + ... + (Wn / true specific gravity n)} / (100 × D)

In the laminated separator of the present invention, the wholly aromatic porous film and / or the shutdown layer are
It may contain particles of an inorganic compound. The inorganic compound to be contained may be any one that has electrochemical oxidation resistance and is inert to the electrolytic solution. Specific examples include aluminum oxide and calcium carbonate, but the present invention is not limited thereto.

In the laminated separator of the present invention, the wholly aromatic polyamide porous film and the shutdown layer are
Although they may be simply superposed, they are preferably bonded by physical force from the viewpoint of handleability.

A preferred method for laminating the laminated separator of the present invention is to use either the wholly aromatic polyamide porous film of the present invention or the shutdown layer as a substrate, and apply the other material to the substrate in a solution state to form a solution layer. Is formed, and the solvent layer is removed from the solution layer to obtain a laminated separator. Hereinafter, preferred examples of the method for producing a laminated separator by coating the solution containing the wholly aromatic polyamide of the present invention on the shutdown layer are shown below, but the present invention is not limited thereto.

(E) A solution containing a polar amide solvent or a polar urea solvent and the wholly aromatic polyamide of the present invention and an alkali metal or an alkaline earth metal is applied on the shutdown layer to form a film-like material. Process. (F) A step of precipitating wholly aromatic polyamide from the film-like material obtained in step (e). (G) A step of removing the solvent and the chloride of the alkali metal or the alkaline earth metal from the film-like material obtained by depositing the wholly aromatic polyamide obtained in the step (f). (H) A step of drying the film-like material obtained in the step (g).

The non-aqueous electrolyte secondary battery of the present invention is characterized by including the above-described separator for non-aqueous electrolyte secondary battery of the present invention. Hereinafter, non-aqueous electrolyte solution other than the separator of the non-aqueous electrolyte secondary battery, the positive electrode sheet, the negative electrode sheet, the constituent elements such as the negative electrode current collector / negative electrode active material will be described.
It is not limited to these.

As the non-aqueous electrolyte solution used in the non-aqueous electrolyte secondary battery of the present invention, for example, a non-aqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent can be used. Examples of lithium salts include LiClO ₄ , LiPF ₆ , and LiAs.
F ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , Li
N (SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B
₁₀ Cl ₁₀ , lower aliphatic carboxylic acid lithium salt, LiAl
One or a mixture of two or more of Cl _{4 and the} like can be mentioned. As the lithium salt, LiPF ₆ containing fluorine Among _{these, LiAsF 6, LiSbF 6, LiBF} 4, L
_{iCF 3 SO 3, LiN (CF} 3 SO 2) 2, and LiC
At least 1 selected from the group consisting of (CF ₃ SO ₂ ) ₃
It is preferable to use those containing seeds.

Examples of the organic solvent used in the non-aqueous electrolyte solution of the present invention include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, Carbonates such as 1,2-di (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether,
Ethers such as 2,2,3,3-tetrafluoropropyldifluoromethyl ether, tetrahydrofuran and 2-methyltetrahydrofuran; esters such as methyl formate, methyl acetate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; N, Amides such as N-dimethylformamide, N, N-dimethylacetamide; carbamates such as 3-methyl-2-oxazolidone; sulfolane, dimethyl sulfoxide,
A sulfur-containing compound such as 1,3-propanesultone; or a compound obtained by introducing a fluorine substituent into the above organic solvent can be used, but usually two or more of these are mixed and used.

Among these, a mixed solvent containing a carbonate is preferable, and a mixed solvent of a cyclic carbonate and an acyclic carbonate, or a mixed solvent of a cyclic carbonate and an ether is more preferable. As a mixed solvent of a cyclic carbonate and an acyclic carbonate, the operating temperature range is wide, the load characteristics are excellent, and it is difficult to decompose even when a graphite material such as natural graphite or artificial graphite is used as the negative electrode active material. Therefore, a mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferable.

As the positive electrode sheet in the present invention, one in which a mixture containing a positive electrode active material, a conductive material and a binder is carried on a current collector is usually used. Specifically, as the positive electrode active material, a material containing a material capable of being doped / dedoped with lithium ions, a carbonaceous material as a conductive material, and a thermoplastic resin or the like as a binder can be used. As the material capable of doping / dedoping the lithium ion,
Examples thereof include lithium composite oxides containing at least one transition metal such as V, Mn, Fe, Co, and Ni. Among them, α-NaFeO ₂ such as lithium nickelate or lithium cobaltate is preferable in that the average discharge potential is high.
Examples thereof include a layered lithium composite oxide having a mold structure as a matrix, and a lithium composite oxide having a spinel structure as a matrix such as lithium manganese spinel.

The lithium composite oxide may contain various additive elements, in particular Ti, V, Cr, Mn, Fe and C.
for the sum of the number of moles of at least one metal selected from the group consisting of o, Cu, Ag, Mg, Al, Ga, In and Sn and the number of moles of Ni in lithium nickelate,
It is preferable to use the composite lithium nickel oxide containing the metal such that the content of the at least one metal is 0.1 to 20 mol% because the cycle property in use in a high capacity is improved.

As the thermoplastic resin as the binder,
Polyvinylidene fluoride, vinylidene fluoride copolymer, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer Examples thereof include polymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, thermoplastic polyimides, polyethylene and polypropylene.

Examples of the carbonaceous material as the conductive agent include natural graphite, artificial graphite, cokes and carbon black. As the conductive material, each may be used alone, or a composite conductive material system in which, for example, artificial graphite and carbon black are mixed and used may be selected.

As the negative electrode sheet in the present invention, for example, a material capable of being doped with lithium ions and dedoped, lithium metal, lithium alloy, or the like can be used. Materials that can be doped or dedoped with lithium ions include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and organic polymer compound calcined materials; lower potential than the positive electrode A chalcogen compound such as an oxide or a sulfide that is doped or dedoped with lithium ions. As a carbonaceous material, a carbonaceous material whose main component is a graphite material such as natural graphite or artificial graphite in that a large energy density can be obtained when combined with a positive electrode because of high potential flatness and low average discharge potential. Is preferred.

As the negative electrode current collector used in the non-aqueous electrolyte secondary battery of the present invention, Cu, Ni, stainless steel or the like can be used, but especially in a lithium secondary battery, it is difficult to form an alloy with lithium, and Cu is preferable because it can be easily processed into a thin film. As a method of supporting the mixture containing the negative electrode active material on the negative electrode current collector, a method of pressure molding or a method of forming a paste by using a solvent or the like, coating on the current collector and drying and then pressing is performed. Is mentioned.

The shape of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited and may be any of paper type, coin type, cylindrical type, prismatic type and the like.

[0057]

EXAMPLES The present invention will now be described in more detail by way of examples, which should not be construed as limiting the invention thereto. The physical properties in Examples and Comparative Examples are as follows.
It was measured by the following method.

(1) Intrinsic viscosity Intrinsic viscosity was measured by the following measuring method. 96-98
% Of 100% sulfuric acid dissolved in 0.5 g of wholly aromatic polyamide and 96-98% sulfuric acid, the flow time was measured by a capillary viscometer at 30 ° C. The viscosity was determined. Intrinsic viscosity = ln (T / T ₀ ) / C [unit: dl / g] Here, T and T ₀ are the flowing times of the wholly aromatic polyamide sulfuric acid solution and sulfuric acid, respectively, and C is the wholly aromatic polyamide sulfuric acid. Total aromatic polyamide concentration in solution (g / d
1) is shown. (2) Air permeability The air permeability was measured according to JIS-P8117. (3) Thickness The thickness of the wholly aromatic polyamide porous film, the shutdown layer, etc. was measured according to JIS standard K7130-1992.

Example 1 (1) Synthesis of a chlorine-substituted wholly aromatic polyamide solution having a chlorine group terminal A 0.5 liter (l) separable column having a stirring blade, a thermometer, a nitrogen inflow tube and a powder addition port. Using a flask, chlorine-substituted poly (paraphenylene terephthalamide) having a chlorine group terminal (hereinafter referred to as Cl-terminal Cl-PPTA
Abbreviated) was synthesized. 12. The flask was thoroughly dried, charged with 400 g of dimethylacetamide (hereinafter abbreviated as DMAc), and dried at 200 ° C. for 2 hours. Lithium chloride 12.
79 g was added and the temperature was raised to 100 ° C. After the lithium chloride was completely dissolved, the temperature was returned to room temperature, and 4.36 g (0.0403 m) of paraphenylenediamine (hereinafter abbreviated as PPD).
ol) and 2-chloro-paraphenylenediamine 1
3.39 g (0.0939 mol) was added and completely dissolved. While keeping this solution at 20 ± 2 ° C, terephthalic acid dichloride (hereinafter abbreviated as TPC) 27.94.
g (0.1377 mol) was added all at once. Thereafter, the solution was aged for 30 minutes while being kept at 20 ± 2 ° C. Next, 0.88 g (0.0007 mol) of orthochloroaniline
Was added, and the reaction was carried out for 1 hour while maintaining the temperature at 20 ± 2 ° C.
The obtained polymerization liquid showed optical anisotropy. A part of the polymerization liquid was sampled, reprecipitated with water and taken out as a polymer, and the intrinsic viscosity of the obtained Cl-terminated Cl-PPTA was measured and found to be 1.88 dl / g. Next, this polymerization liquid 8
1 g was weighed into a 0.5 L separable flask having a stirring blade, a thermometer, a nitrogen inflow tube and a liquid addition port, and D
MAc was added slowly. Finally, Cl-terminal Cl-P
A solution having a PTA concentration of 2.0% by weight was prepared. To this liquid, 1.78 g of lithium carbonate was added, neutralized, and filtered. Next, the same amount of alumina powder (average particle size = 13 nm) as the weight of the polymer in the liquid was added, and the nanomizer (LA
-30S / manufactured by Cosmo Keiso Co., Ltd.). This is designated as solution A.

(2) Preparation of laminated separator As a shutdown layer, a polyethylene (PE) porous film (film thickness 25 μm, air permeability 700 sec / 100 cc,
The average pore radius (mercury intrusion method) 0.04 μm) was used.
Tester Sangyo Co., Ltd. bar coater (clearance 2
Solution (A) was applied onto the above-mentioned PE porous membrane with a thickness of 00 μm). After coating, the product was kept in a thermo-hygrostat (30 ° C., 65% RH) for about 5 minutes, and Cl-terminal Cl-PPTA was precipitated to give a cloudy film. 30% NM of the film
After being immersed in the P aqueous solution for 5 minutes, it was thoroughly washed with ion-exchanged water. Then, the wet film-like material was taken out from water, and free water was wiped off. The film-like material was sandwiched between nylon cloths and further sandwiched between aramid felts. With the membrane material sandwiched between nylon cloth and aramid felt, put an aluminum plate, cover it with a nylon film, seal the nylon film and aluminum plate with gum, and attach a conduit for decompression. . The whole was placed in a hot oven and the film was dried under reduced pressure at 60 ° C. The obtained separator had a thickness of 28 μm and an air permeability of 1410 seconds / 1.
It was 00 cc.

(3) Molecular model of chlorine-substituted wholly aromatic polyamide having a chlorine group terminal The composition of the polymer is PPD based on the molar ratio of the raw materials charged.
/ Cl-PPD / TPC / 2-chloroaniline = 29.
It becomes 25 / 68.25 / 100/5 (mol%). The following molecular model was obtained by modeling the polymer according to the structure estimated from the charged molar ratio.

Example 2 (1) Synthesis of a wholly aromatic polyamide solution having a chlorine group terminal A 0.5 liter (l) separable flask having a stirring blade, a thermometer, a nitrogen inflow tube and a powder addition port was used. Then, poly (paraphenylene terephthalamide) having a chlorine group terminal (hereinafter, abbreviated as Cl terminal PPTA) was synthesized. The flask was thoroughly dried and charged with 400 g of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP), 20
28.38 g of calcium chloride dried at 0 ° C. for 2 hours was added, and the temperature was raised to 100 ° C. After the calcium chloride was completely dissolved, the temperature was returned to room temperature and 0.73 g of 2-chloroaniline
(0.0057 mol), PPD 12.19 g (0.1
127 mol) was added and completely dissolved. While keeping this solution at 20 ± 2 ° C, 23.24 g (0.1%) of TPC was used.
145 mol) was added all at once. Then add 20 ±
It was aged for 1 hour while being kept at 2 ° C. The obtained polymerization liquid showed optical anisotropy. A part was sampled, reprecipitated with water and taken out as a polymer.
When the intrinsic viscosity of A was measured, it was 1.29 dl / g. Next, 150 g of this polymerization liquid was weighed into a 0.5 L separable flask having a stirring blade, a thermometer, a nitrogen inflow tube, and a liquid addition port, and the NMP solution was gradually added. Finally, a solution having a Cl-terminal PPTA concentration of 2.0% by weight was prepared. To this liquid, 2.04 g of calcium oxide was added, neutralized, and filtered. This is designated as solution B.

(2) Application of wholly aromatic polyamide solution having a chlorine group terminal and preparation of separator The same shutdown layer as in Example 1 was used. Solution B was applied onto the above-mentioned PE porous membrane using a bar coater (clearance: 135 μm) manufactured by Tester Sangyo Co., Ltd. After the application, the product was kept in a thermo-hygrostat for about 3 minutes, whereupon Cl-terminated PPTA was precipitated and a cloudy film was obtained. The membrane-like material was immersed in a 30% NMP aqueous solution for 5 minutes, washed sufficiently with flowing ion-exchanged water, the wet membrane-like material was taken out of the water, and free water was wiped off. This film-like material was dried in the same manner as in Example 1.
The air permeability of the obtained separator is about 3000 seconds / 100.
It was cc.

(3) Molecular model of chlorine-substituted wholly aromatic polyamide having a chlorine group terminal The composition of the polymer is PPD based on the molar ratio of the raw materials charged.
/TPC/2-chloroaniline=98.5/100/5
(Mol%). The following molecular model was obtained by modeling the polymer according to the structure estimated from the charged molar ratio.

Comparative Example 1 (1) Synthesis of wholly aromatic polyamide solution 5 having a stirring blade, thermometer, nitrogen inflow pipe and powder addition port 5
Using a liter (l) separable flask, poly (paraphenylene terephthalamide) (hereinafter referred to as PPTA
Abbreviated) was synthesized. Dry the flask thoroughly, N-
Methyl-2-pyrrolidone (hereinafter abbreviated as NMP) 420
0 g was charged, 272.65 g of calcium chloride dried at 200 ° C. for 2 hours was added, and the temperature was raised to 100 ° C. After the calcium chloride is completely dissolved, return to room temperature, and use PPD1
32.91 g was added and completely dissolved. 2 this solution
While maintaining the temperature at 0 ± 2 ° C, 243.32 g of TPC was divided into 10 portions and added every about 5 minutes. Then the solution is 20 ± 2 ℃
Aging for 1 hour while keeping at room temperature, and under reduced pressure to remove air bubbles 30
Stir for minutes. The obtained polymerization liquid showed optical anisotropy.
A part of the polymer was sampled, reprecipitated with water, taken out as a polymer, and the intrinsic viscosity of the obtained PPTA was measured to be 1.97 dl / g. Next, 100 g of this polymerization liquid
Was weighed into a 500 ml separable flask equipped with a stirring blade, thermometer, nitrogen inflow tube and liquid addition port, and NMP
The solution was added slowly. Finally, the PPTA concentration was 2.
A 0 wt% PPTA solution was prepared and designated as solution C.

(2) Preparation of laminated separator The same shutdown layer as in Example 1 was used. A film coater of liquid C, which is a heat-resistant resin solution, was prepared on a glass plate using a bar coater (clearance: 200 μm) manufactured by Tester Sangyo Co., Ltd.
When it was held for 0 minutes, PPTA was precipitated and a cloudy film-like material was obtained. The membrane material was immersed in ion exchange water.
The film was peeled from the glass plate after 5 minutes. After thoroughly washing with flowing ion-exchanged water, the moist film was taken out of the water and the free water was wiped off. The film-like material was sandwiched between nylon cloths and further sandwiched between aramid felts. With the film-like material sandwiched between nylon cloth and aramid felt, put an aluminum plate, cover it with a nylon film, seal with a nylon film, aluminum plate and gum,
A conduit for vacuum was attached. Put the whole in the heat oven 6
The film was dried under reduced pressure at 0 ° C.

(3) Molecular model The polymer was modeled according to the structure estimated from the charged amount of the above raw materials to obtain the following molecular model.

Example 3 <Preparation of flat plate battery and alteration evaluation test under high voltage use condition>
Dissolve 3 parts by weight of polyvinylidene fluoride in NMP,
9 parts by weight of artificial graphite powder as a conductive material, 1 part by weight of acetylene black, and 87 parts by weight of lithium cobalt oxide powder as a positive electrode active material were dispersed and kneaded to obtain a positive electrode mixture paste.
The paste was applied to an Al foil having a thickness of 20 μm as a current collector, dried and roll-pressed to obtain a positive electrode sheet-shaped electrode. The positive electrode sheet and metallic lithium as a negative electrode,
Laminated through the laminated separator prepared in Example 1 and Comparative Examples 1 and 2, 30% ethylene carbonate, 35%
An electrolytic solution in which 1M LiPF ₆ was dissolved was added to a mixed solvent of ethyl methyl carbonate and 35% dimethyl carbonate to prepare a flat plate battery. Here, the separator was laminated so that the wholly aromatic polyamide porous film side was in contact with the positive electrode sheet. The plate battery thus obtained was
Constant-current constant-voltage charging was carried out under the condition that the state of 5 V was maintained for 1 day. The battery after charging was disassembled, and the separators produced in Examples 1 and 2 and Comparative Example 1 were taken out and observed. The observation results are shown in Table 1.

[0069]

[Table 1] HOMO value and separator observation result after alteration evaluation test ^* Discoloration of the wholly aromatic polyamide porous film side of the laminated separator ^** HOMO of the nitrogen atom of the amino group of the terminal phenyl group
value

[0070]

EFFECT OF THE INVENTION The wholly aromatic polyamide of the present invention undergoes little deterioration even when a high voltage is applied. Therefore, the wholly aromatic polyamide porous film using it is useful as a separator for a non-aqueous electrolyte secondary battery.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) // C08L 77:10 C08L 77:10 (72) Inventor Yuki Nishida 6 Kitahara, Tsukuba-shi, Ibaraki Sumitomo Chemical Co., Ltd. 72) Inventor Tsutomu Takahashi 6 Kitahara, Tsukuba City, Ibaraki Prefecture Sumitomo Chemical Co., Ltd. (72) Inventor Fumihiro Sakano 6 Kitahara, Tsukuba City, Ibaraki Prefecture F Term (reference) 4F074 AA72 CB14 CB34 DA49 4J001 DB04 DC16 DD03 DD04 DD06 DD07 DD16 EB28 EB44 EB46 EC36 EC46 EC54 EC56 EC67 EE53F EE64F GA13 GB02 JA20 5H021 AA06 BB01 BB13 CC04 EE02 EE04 EE07 HH00 5H029 AJ13 AK03 AJJJJJJJ04 J04 AJAMJ AMJ AM14 AM12 AM04 AM12 AM04 AM04 AM05 AM04 AM05 AM12 AM04 AM05 AM12 AM04 AM12 AM04 AM05

Claims (8)

[Claims] 1. A wholly aromatic polyamide having a HOMO (highest occupied molecular orbital energy) value of -8.5 eV obtained by a molecular orbital method calculation of all nitrogen atoms of a molecular model of the wholly aromatic polyamide. A wholly aromatic polyamide characterized by being: 2. The wholly aromatic polyamide according to claim 1, wherein the aromatic ring at the end of the polymer chain has substantially no amino group. 3. A substitution in which the aromatic ring at the end of the polymer chain has substantially no amino group, and the aromatic ring at the end of the polymer chain and / or the aromatic ring in the polymer chain is electron-withdrawing The wholly aromatic polyamide according to claim 2, which has a group. 4. A wholly aromatic polyamide porous film comprising the wholly aromatic polyamide according to claim 1. 5. The method for producing a wholly aromatic polyamide porous film according to claim 4, comprising the following steps (a) to (d). (A) A step of forming a film-like product from a solution containing a polar amide-based solvent or a polar urea-based solvent, and the wholly aromatic polyamide according to any one of claims 1 to 3 and an alkali metal or an alkaline earth metal. (B) A step of precipitating wholly aromatic polyamide from the film-like material obtained in step (a). (C) A step of removing the solvent and the chloride of the alkali metal or the alkaline earth metal from the film-like material on which the wholly aromatic polyamide obtained in the step (b) is deposited. (D) A step of drying the film-like material obtained in step (c). 6. A separator for a non-aqueous electrolyte secondary battery, which comprises the wholly aromatic polyamide porous film according to claim 4. 7. The separator for a non-aqueous electrolyte secondary battery according to claim 6, which has a laminated structure of a wholly aromatic polyamide porous film and a porous film having a shutdown function. 8. A non-aqueous electrolyte secondary battery comprising the separator for a non-aqueous electrolyte battery according to claim 6 or 7.