JP2626350B2 - Ion conductive polymer compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion conductive polymer compound and, more particularly, to an improvement in an ion conductive polymer compound useful as a material for batteries, electric double layer capacitors and other electrochemical devices.

[0002]

2. Description of the Related Art Conventionally, as an electrolyte of an electrochemical device such as a battery, an electric double layer capacitor or an electrochromic element utilizing an electrochemical reaction, an ionic compound is generally dissolved in a liquid electrolyte, particularly an organic electrolyte. Although liquid electrolytes have been used, liquid electrolytes are liable to leak out of components, elute elution and volatilization of the electrode material, and thus have problems such as long-term reliability and the scattering of electrolyte during the sealing process. Had been a problem.

[0003] Therefore, in order to improve the liquid leakage resistance and the long-term storage property, ion conductive polymer compounds having high ion conductivity have been reported, and as one means for solving the above-mentioned problems, active research has been conducted. Is being promoted.

[0004] The ion conductive polymer compounds that are currently being studied are homopolymer or copolymer linear polymers having ethylene oxide as a basic unit, and the purpose is to increase the ionic conductivity at low temperatures. As
It has been proposed and implemented to prevent crystallization by making a network crosslinked polymer or comb polymer. In particular, an ion conductive polymer compound using the above network crosslinked polymer is useful because it has high mechanical strength and good ionic conductivity at low temperatures.

When the above-mentioned ion-conductive polymer compound is applied to an electrolyte of an electrochemical device, it is necessary to make the electrolyte thinner in order to lower the internal resistance. In the case of an ion conductive polymer compound, a uniform thin film can be easily processed into an arbitrary shape, but this method poses a problem. For example, a method of casting a solution of an ion-conductive polymer compound to evaporate and remove the solvent, a method of applying a polymerizable monomer or a macromer on a substrate and polymerizing by heating, or a method of curing by irradiation with actinic rays, and the like. There is. In particular, the method of curing by irradiation with actinic rays can be processed at a low temperature in a short time, and thus has advantages such as improved workability.

[0006]

However, although uniform thinning is possible by using the above method, an ion conductive polymer compound thin film is actually laminated between the electrodes.
When a battery, an electrochromic element, or the like is assembled, the electrolyte layer may be damaged by compressive deformation, resulting in a short circuit. Furthermore, when the area of the ion-conductive polymer compound is increased, a slight short circuit is more likely to occur. For this reason, there is a problem with the conventional technique to make the electrolyte layer thinner uniformly.

[0007] As a method for preventing breakage and short circuit of the ion conductive polymer compound thin film, various methods have been reported in which an inorganic oxide is contained in the ion conductive polymer compound.

However, since functional groups such as —OH groups are present on the surface of the inorganic oxide, there is an extremely high risk that these will cause side reactions when a battery or an electrochromic device is assembled. This side reaction is particularly noticeable in the case of a battery when stored for a long period of time, in the form of a decrease in discharge capacity and a decrease in cycle characteristics.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has a high reliability in a battery, an electric double layer capacitor and other electrochemical devices using an ion conductive polymer compound. It is intended to provide a chemical device.

[0010]

In order to solve the above-mentioned problems, the present invention provides an ionic conductive polymer compound containing an ionic compound in an organic polymer, wherein the ionic compound contains an organic compound. This is a first invention, and the second invention is characterized in that the organic compound is a styrene / methacrylic acid ester or a styrene / acrylic acid ester copolymer.

[0011] Further, the ion-conductive polymer compound is obtained by dissolving an ionic compound in a polymer obtained by crosslinking a polyether, and the ion-conductive polymer compound dissolves the ionic compound. The above-mentioned object is achieved by providing an electrolyte thin film made of the above-mentioned ion-conductive polymer compound.

The thin film of the ion-conductive polymer compound of the present invention can be obtained not only by coating a polymerizable monomer or macromer on a substrate and curing it by irradiation with actinic rays, but also by obtaining a uniform thin film. It can be suitably used as an ion-conductive polymer compound thin film that does not cause a slight short circuit of the electrode and does not cause a short circuit even when the area of the thin film is increased.

Further, the organic compound of the present invention, when applied to lithium primary and secondary batteries using, for example, lithium metal or a lithium alloy for the negative electrode, is more effective than conventional inorganic oxides. It is possible to suppress the reaction with the compound surface. That is, since there are almost no -OH groups or functional groups that react with lithium present on the surface, for example, when applied to lithium primary and secondary batteries using lithium metal or lithium alloy for the negative electrode, lithium And the reaction with the inorganic oxide surface can be suppressed. In addition, the organic compound can be dried at 100 to 300 ° C. under reduced pressure as needed to remove surface adsorbed water.

The ion conductive high molecular compound in which an ionic compound is dissolved in an organic polymer obtained by cross-linking a polyether is cross-linked by the above-mentioned organic polymer being ether-bonded to a polyether having a polyfunctional hydroxyl group by diacrylate. Things.

Next, as the ionic compound contained in the organic polymer thus obtained, for example, LiCl
O ₄ , LiSCN, LiBF ₄ , LiAsF ₆ , LiC
F ₃ SO ₃ , LiCF ₃ CO ₂ , NaI, NaSCN,
Inorganic ion salts containing one kind of Li, Na, or K such as NaBr, KSCN, etc., (CH ₃ ) ₄ NBF ₄ , (CH ₃ )
₄ NBr, (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) _{4
NI, (C 3 H 7)} 4 NBr, (n-C 4 H 9) 4 NC
10 ₄ , (n-C ₄ H ₉ ) ₄ NI, (C ₂ H ₅ ) ₄ N-
maleate, (C ₂ H ₅ ) ₄ N-benzoate
_{e, (C 2 H 5)} 4 quaternary ammonium salts such as N-phtalate, lithium stearyl sulfonate, sodium octyl sulfonate, and organic ion salts of lithium dodecylbenzenesulfonate. These ionic compounds may be used in combination of two or more.

The compounding ratio of such an ionic compound is as follows:
The ratio of the ionic compound is 0.0001 to 5.0 mol, preferably 0.005 to 2.0 mol, based on the number of ether bond oxygen atoms of the organic polymer. If the amount of this ionic compound is too large,
Excess ionic compounds, for example, inorganic ionic salts, do not dissociate but are merely mixed, resulting in a reduction in ionic conductivity. Further, the appropriate mixing ratio of the ionic compound differs depending on the electrode active material. For example, in a battery using the intercalation of a layered compound, the vicinity where the conductivity of the electrolyte is maximum is preferable, and in a battery using a conductive polymer using a doping phenomenon as an electrode active material, It is necessary that the ion concentration in the electrolyte can respond to changes due to charge and discharge.

The method of containing the ionic compound is not particularly limited. For example, methyl ethyl ketone (ME
K) or a method of dissolving in an organic solvent such as tetrahydrofuran (THF) and uniformly mixing with an organic compound, and then removing the organic solvent by vacuum reduction.

Next, in the present invention, a substance capable of dissolving the ionic compound contained in the organic polymer may be contained in the ion-conductive polymer compound. The conductivity can be significantly improved without changing the skeleton.

Examples of the substance capable of dissolving the ionic compound include cyclic carbon esters such as propylene carbonate and ethylene carbonate, cyclic esters such as γ-butyrolactone, tetrahydrofuran or derivatives thereof,
Examples thereof include ethers such as 3-dioxane and 1,2-dimethoxyethane, nitriles such as acetonitrile and benzonitrile, dioxolanes and derivatives thereof, and sulfolanes and derivatives thereof alone or a mixture of two or more thereof. However, it is not limited to these. The mixing ratio and the mixing method are arbitrary.

The method of applying the ion-conductive polymer compound of the present invention may be performed, for example, using a roller coating such as an applicator roll, a screen coating, a doctor blade method, a spin coating, a bar coder or the like. It is desirable to apply the composition, but the composition is not limited thereto.

Examples of the electrode of a battery constituting a battery using the ion conductive polymer compound of the present invention include the following battery electrode materials. As the positive electrode active material, CuO, Cu
Group I metal compounds such as ₂ O, Ag ₂ O, CuS, CuSO ₄ , Group IV metal compounds such as TiS ₂ , SiO ₂ , SnO, V ₂ O ₅ , V ₆ O ₁₂ , VO _x , Nb ₂ O ₅ , Bi ₂
Group V metal compounds such as O ₃ and Sb ₂ O ₃ , CrO ₃ and C
Group VI metal compounds such as r ₂ O ₃ , MoO ₃ , MoS ₂ , WO ₃ and SeO ₂ , Group VII metal compounds such as MnO ₂ and Mn ₂ O ₃ , Fe ₂ O ₃ , FeO, Fe ₃ O ₄ , Ni _Two
Group VIII metal compounds such as O ₃ , NiO, CoO ₃ , CoO, or the general formulas Li _X MX _y , Li _X MN _y X
₂ (M and N are metals of groups I to VIII, and X is a chalcogen compound such as oxygen or sulfur). For example, a metal compound such as a lithium-cobalt-based composite oxide or a lithium-manganese-based composite oxide, polypyrrole,
Polyaniline, polyparaphenylene, polyacetylene,
Examples thereof include, but are not limited to, conductive polymer compounds such as polyacene-based materials, and carbonaceous materials having a pseudo-graphite structure.

Examples of the negative electrode active material include lithium alloys such as lithium metal, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium and wood alloys, and carbonaceous materials such as carbon. However, the present invention is not limited to these. Further, those used as the positive electrode active material can also be used.

As the positive electrode and the negative electrode of the battery, those obtained by binding the above active materials with a binder to form a sheet or a pellet are generally used. In these cases, if necessary, graphite or carbon black may be used. , A carbon such as acetylene black (the carbon has a completely different characteristic from the carbon in the above-mentioned negative electrode active material) and a conductive material such as a metal powder and a conductive metal oxide. It can be mixed in the composite negative electrode to improve electron conduction. Further, when producing the above composite positive electrode and composite negative electrode, several kinds of dispersants and dispersion media can be added to obtain a uniform mixed dispersion system. Further, it is also possible to add a thickener, a bulking agent, a tackifier and the like.

The separator is a sheet of the above-described ion-conductive polymer compound alone and is disposed between the positive electrode and the negative electrode, or the separator is applied and cured on the positive electrode or the negative electrode, Complexing is also possible.

When an electric double layer capacitor is formed by using the ion conductive polymer compound of the present invention, the electrode material of the electric double layer capacitor may be such that the capacitance of the oxide dielectric in the electrolytic capacitor is not involved. An electrode material, for example, activated carbon or carbon fiber having a large specific surface area and being electrochemically inert may be used. It is preferable to use an ion conductive polymer compound as a binder for these carbon materials, but there is a method using a substance other than the ion conductive polymer compound (for example, polytetrafluoroethylene). Molecular compounds can be used in combination.

[0026]

According to the present invention, a uniform ion-conductive polymer compound thin film can be obtained because the ion-conductive polymer compound containing an ionic compound in an organic polymer contains fine particles of an organic compound having a very small particle diameter. In addition, it is possible to provide an ion-conductive polymer compound thin film that does not cause a short circuit between electrodes due to thinning and does not cause a short circuit even when the area of the thin film is increased. .

The inclusion of the fine particles of the above organic compound promotes the amorphization of the organic polymer structure. Further, since the organic polymer has a side chain similar to the main chain, the crystallization temperature of the organic polymer is lowered, and the movement of ions is reduced. Therefore, the ionic conductivity is improved in a temperature range of room temperature or lower, the quality is stabilized, a variety of shapes can be obtained, and a film having excellent adhesion to the electrode surface can be produced.
Also, since there is no fear of liquid leakage to the outside, long-term reliability and safety are extremely high. Therefore, it is possible to provide a very excellent and practical ion-conductive polymer compound having improved reliability, workability and low-temperature characteristics.

[0028]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

Example 1 Dimethacrylic acid ester of ethylene oxide (molecular weight:
4000) and a 7: 3 mixture of polyethylene glycol monoacrylate (molecular weight: 400), 30 parts by weight of an organic polymer, 6 parts by weight of lithium perchlorate and 64 parts by weight of propylene carbonate 100
Parts by weight and Nippon Paint Micro Jiel (Part No. P-5
002) and 7 parts by weight. The microjewel is a styrene / acrylate copolymer.
The average particle size is 1 μm or less, more preferably 100 μm.
nm or less can be used. This liquid was cast on a glass plate and irradiated with 6 Mrad of electron beam to be cured. The thickness of the obtained ion-conductive polymer compound thin film was 100 μm. After punching this thin film into a diameter of 13 mm, the ionic conductivity of this thin film was measured by a complex impedance method using a conductivity measuring cell using a Pt electrode. As a result, 1.7 × 10 ⁻³ Scm ⁻ at 25 ° C. ¹ , 7.0 × 10 ⁻⁴ Scm ⁻¹ at 0 ° C., 2.2 × 10 ⁻⁴ S at −20 ° C.
cm ^-1 . Regarding the flexibility of the ion-conductive polymer compound, as a result of conducting a 90 ° bending test and a 180 ° bending test, no crack was generated in any case.

Comparative Example 1 An ion-conductive polymer compound was prepared in the same manner as in Example 1 except that the microgel was not used. The thickness of the obtained ion-conductive polymer compound thin film was 100 μm. As a result of measuring the ionic conductivity of this thin film by the complex impedance method, 1.5 × 10 ⁻³ Scm ⁻¹ at 25 ° C., 6.4 × 10 ⁻⁴ Scm ⁻¹ at 0 ° C., and 1.9 at −20 ° C. × 10 ^-4
It was Scm ^-1 .

However, when measuring the ionic conductivity using a conductivity measuring cell using a Pt electrode, there are problems that the ion conductive polymer compound thin film is easily damaged and a uniform thin film is hardly obtained. occured. As a result, the thin film was damaged and short-circuited in 16 cells out of 65 cells of the measurement sample.

(Example 2) A sheet-like battery was experimentally manufactured using the ion-conductive polymer compound of Example 1. Hereinafter, a)
1 to c), a method for manufacturing a sheet-shaped battery will be described.

A) Manganese dioxide is used as a positive electrode active material of a battery, acetylene black is used as a conductive agent, and dimethacrylate of ethylene oxide (molecular weight:
5000) and an organic polymer obtained by mixing polyethylene glycol monoacrylate (molecular weight: 400) in a ratio of 7: 3 were used as the positive electrode composite.

The method for producing this positive electrode composite is as follows. That is, in a mixture of manganese dioxide and acetylene black in a ratio of 85:15, 1 part by weight of lithium perchlorate and 0.05 part by weight of azobisisobutyronitrile were dissolved in 10 parts by weight of the organic polymer. And 1: 1 in a dry inert gas atmosphere. These mixtures are cast on a current collector having a conductive carbon film formed on the surface of a positive electrode current collector plate made of stainless steel, and cured by being left at 100 ° C. for 1 hour in an inert gas atmosphere. Was. The thickness of the positive electrode composite coating formed on the stainless steel current collector was 60 μm.

B) Lithium metal was used as the negative electrode active material of the battery, and this was pressed onto a negative electrode current collector plate made of stainless steel. Next, in order to form the ion conductive polymer compound layer of the present invention on the lithium metal, the organic polymer 3
100 parts by weight of a mixture of 0 parts by weight, 6 parts by weight of lithium perchlorate and 64 parts by weight of propylene carbonate, and a microgel manufactured by Nippon Paint Co., Ltd. (Part No. P-5002)
And 7 parts by weight were cast on the lithium metal, and cured by irradiating with 6 Mrad of electron beam.
The thickness of the electrolyte layer thus obtained was 20 μm.

C) By contacting the electrolyte / lithium / negative electrode current collector obtained in b) with the positive electrode current collector / positive electrode composite obtained in a), sheet batteries were respectively produced.

FIG. 1 is a sectional view of a sheet-shaped battery using the ion-conductive polymer compound of the present invention. In the figure, 1 is a positive electrode current collector made of stainless steel, 2 is a positive electrode composite, manganese dioxide is used as a positive electrode active material, acetylene black is used as a conductive agent, and a monoacrylate of ethylene oxide diacrylate and polyethylene glycol is used as a binder. An organic polymer mixed with an acrylate was used. Reference numeral 3 denotes an electrolyte comprising the ion-conductive polymer compound of the present invention. Reference numeral 4 denotes metallic lithium, and reference numeral 5 denotes a negative electrode current collector plate made of stainless steel, which also serves as an exterior. 6
Is a sealing material made of modified polypropylene.

The electrode area of a sheet-shaped battery using the ion-conductive polymer compound of the present invention can be variously changed depending on the manufacturing process. In this embodiment, the electrode area is set to 100 cm ^2. Produced. The sheet-shaped battery using the ion-conductive polymer compound of Example 1 was referred to as Battery A below.
Called.

Comparative Example 2 Using the ion-conductive polymer compound of Comparative Example 1, a sheet-like battery was prototyped under the same conditions and under the same method as in Example 2. The electrode area is 100cm
² was produced. The sheet-shaped battery fabricated in this manner is hereinafter referred to as Battery B.

(Experiment) Battery A of Example 2 of the present invention
The initial discharge characteristics of the battery B of Comparative Example 2 were examined. The result is shown in FIG. FIG. 2 shows the initial discharge characteristics when the battery was assembled and discharged at 25 ° C. and a load of 3 kΩ.

As is clear from FIG. 2, the battery A of the present invention
It is recognized that the initial discharge characteristics are superior to that of the battery B of Comparative Example 2. Regarding the cause, not only a uniform thin film can be obtained with the ion-conductive polymer compound of the present invention, but also a short circuit of the electrode does not occur due to thinning, but the ion-conductive polymer compound of the comparative example does not It is considered that a slight short circuit has occurred.

[0042]

As is clear from the above description, the ion-conductive polymer compound of the present invention contains fine particles of an organic compound in the ion-conductive polymer compound, so that a uniform ion-conductive polymer compound thin film is obtained. Not only do not cause any short-circuiting of the electrodes due to thinning, but also do not cause short-circuiting even when the area of the thin film is increased, so that the workability is excellent and the ion conductivity is excellent. Ionic conductive polymer compounds can be produced. From these facts, there is an effect that the performance of the ion conductive polymer compound can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a sheet-shaped battery using the ion-conductive polymer compound of the present invention.

FIG. 2 is a diagram showing initial discharge characteristics of a battery A of the present invention and a battery B of a comparative example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 positive electrode current collector 2 positive electrode composite 3 electrolyte 4 metallic lithium 5 negative electrode current collector 6 sealing material

Claims (3)

(57) [Claims] Claims: 1. An ion conductive polymer compound containing an ionic compound in an organic polymer, wherein the ion conductive polymer compound contains styrene / methacrylic ester or
An ion conductive polymer compound comprising fine particles of a styrene / acrylate copolymer . 2. The ion-conductive polymer compound according to claim 1, wherein said ion-conductive polymer compound is obtained by dissolving an ionic compound in a polymer obtained by crosslinking polyether. 3. The ion conductive polymer compound according to claim 1, wherein the ion conductive polymer compound contains a substance capable of dissolving the ionic compound.