JP2581338B2 - Polymer solid electrolyte and battery using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid polymer electrolyte, and more particularly to a solid polymer electrolyte useful as a material for batteries, electric double layer capacitors and other electrochemical devices, and a battery using the same.

[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. Therefore, in order to improve the liquid leakage resistance and the long-term storage property, a polymer solid electrolyte having high ionic conductivity has been reported, and further studies have been made as one of means for solving the above-mentioned problems.

[0003]

In order to apply the above polymer solid electrolyte to batteries, electric double layer capacitors and other electrochemical devices in the future, the following characteristics are required. That is,

[0004] 1) Good ion conductivity 2) Low temperature dependence of ion conductivity 3) High storage stability 4) Excellent film formability and workability 5) Production of materials Easy thing

[0005] However, a solid polymer electrolyte which satisfies such required performance comprehensively has not been developed so far. For example, an organic polymer electrolyte of polyethylene oxide (PEO), an organic polymer electrolyte in which a polyethylene oxide portion and a propylene oxide portion of a polyfunctional polyether molecular structure are randomly copolymerized (Japanese Patent Application Laid-Open No.
Japanese Patent Application Laid-Open No. 2-249361) and a solid polymer electrolyte comprising an ethylene oxide copolymer containing an ionic compound in a dissolved state (Japanese Patent Application Laid-Open No. 61-83249) are known. However, in the linear PEO,
Crystallization of PEO occurs at a temperature lower than the melting point (around 60 ° C.), and the ionic conductivity sharply decreases. In other polymer electrolytes as well, crystallization is suppressed,
Although the conductivity at room temperature around 5 ° C. has been improved, the conductivity below that temperature is not a value that can be actually used, and drops extremely below 5 ° C. That is, there has been a problem that crystallization of an ethylene oxide chain having ion conductivity cannot be prevented.

As described above, since the ionic conductivity of the PEO-based polymer solid electrolyte has a large temperature dependency, it is difficult to incorporate the ionic conductivity into general-purpose electronic equipment that can be used in a wide temperature range. Therefore, ordinary molecular weight PEO
In addition, there has been proposed a method in which low molecular weight (molecular weight of 1,000 or less) PEO is mixed and used (JP-A-62-1392).
No. 66). However, even this method did not satisfy the required performance described above. That is, by mixing a large amount of low molecular weight PEO, the ionic conductivity at room temperature or lower is improved, but the film forming property is reduced, and it becomes difficult to form a thin film.

[0007] From the above, the conventional PEO-based polymer solid electrolyte solves the problem that the ionic conductivity at room temperature or lower has a large temperature dependence, or the film-forming property and workability are extremely poor. It was impossible.

The present invention has been made in view of the above-mentioned problems of the prior art, and has been developed in a battery, an electric double layer capacitor, and other electrochemical devices using a polymer solid electrolyte. High degree,
It is another object of the present invention to provide a highly reliable electrochemical device by producing a polymer solid electrolyte having better film forming properties and processability than conventional PEO-based polymer solid electrolytes.

[0009]

[Means for Solving the Problems]

The present invention has been made in view of the above-mentioned problems of the prior art, and has at least one block copolymer.
A polymer solid electrolyte in which a kind of monomer unit has a liquid crystalline molecular structure and the block copolymer contains an ionic compound, and a battery using the same. The block copolymer is represented by the following general formula: ALB (where L is a liquid crystal molecular structural molecular chain, A is
Is formula 18.

Embedded image Note that R ₁ and R ₂ are a hydrogen atom or an alkyl group having 1 or more carbon atoms, and n is an integer of 5 to 1500.

Embedded image R ₃ and R ₄ are a hydrogen atom or an alkyl group having 1 or more carbon atoms, and m represents an integer of 0 to 1500), and is a block copolymer having a skeleton represented by the following formula: It is characterized by being formed from an acidic molecular chain.

Further, the liquid crystal molecular structural molecular chain is represented by the following chemical formulas

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Embedded image (Where R and R ′ are alkyl groups having 1 to 10 carbon atoms,
k represents an integer of 1 to 20, and h represents an integer of 1 to 6. )
Is selected from at least one or more of the following.

[0012] Further, the polymer solid electrolyte contains a substance capable of dissolving an ionic compound, and by providing an electrolyte thin film made of the polymer solid electrolyte, The above object has been achieved. That is, the solid polymer electrolyte of the present invention has a structure in which liquid crystal monomer chains are inserted into blocks in order to prevent crystallization of an alkylene oxide chain exhibiting ionic conductivity. This prevents crystallization or orientation between molecules of an alkylene oxide chain having the following formula, and makes it possible to maximize the molecular motion of the alkylene oxide chain. Therefore, it was possible to exhibit good ionic conductivity in a wider temperature range without hindering the molecular motion of the alkylene oxide chain at room temperature.

Further, since the solid polymer electrolyte of the present invention has an ethylene oxide chain or a propylene oxide chain, it has a high dielectric constant and dissolves an ionic compound.
Excellent ability to dissociate. Further, the solid polymer electrolyte of the present invention has a structure in which the hard part of the liquid crystal molecular chain and the soft part of the ionic polymer chain are microphase-separated (sea-island structure).
have. Therefore, due to the presence of the hard part of the liquid crystal molecular chain, the mechanical strength and the film forming property of the organic polymer were remarkably improved as will be described later.

The molecular chains of the liquid crystal molecular structure are as described above.

Embedded image

Embedded image (However, R and R ′ are alkyl groups having 1 to 10 carbon atoms,
k is an integer of 1 to 20), but is not particularly limited. Polymer solid electrolyte of the present invention, for example,
Chemical 35

Embedded image (Wherein R and R ′ in the formula are the same as above, X is a halogen atom) and at least one liquid crystal molecule represented by MeOH (Me
Represents a sodium, potassium or cesium atom. ) Is dissolved in water at a molar ratio of 2: 1 to carry out condensation polymerization, thereby synthesizing Chemical formula 36.

Embedded image (Wherein R, R 'and X are the same as above, and k represents an integer from 1 to 20).

Embedded image (Wherein R ₁ , R ₂ and n in the formula are the same as above), and an equimolar amount of the polyalkylalkylene oxide is added.

Embedded image (Wherein R ₁ , R ₂ , n, R, R ′ and k are the same as above)
Is synthesized into

Embedded image (Wherein R ₃ and R ₄ are the same as above) to produce a block copolymer.

Here, the molecular weight ratio between the liquid crystal molecular structure molecular chain and the ether molecular chain is not particularly limited.
5:95 to 40:60, more preferably 1
The range of 0:90 to 25:75 is ideal.

At this time, by selecting the starting material of the liquid crystal molecule, the liquid crystal molecular chain according to claim 4 can be produced. Further, as the catalyst used in the polymerization reaction for producing a block copolymer by adding an alkylene oxide, a basic catalyst such as sodium methylate, caustic soda, caustic potash, and lithium carbonate is generally used, and such a catalyst as boron trifluoride is used. Acid catalysts and amine catalysts such as trimethylamine and triethylamine are also useful. The amount of the catalyst used is arbitrary.

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,
One of Li, Na, or K, such as NaBr, KSCN, etc.
Inorganic ionic salts containing species, (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 NCLO ₄ , (n-C ₄ H ₉ ) ₄ NI, (C ₂ H
_{5) 4 N-maleate, (} C 2 H 5) 4 N-ben
quat, quaternary ammonium salts such as (C ₂ H ₅ ) ₄ N-phthalate, lithium stearyl sulfonate,
Organic ion salts such as sodium octylsulfonate and lithium dodecylbenzenesulfonate. These ionic compounds may be used in combination of two or more.

The mixing 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. The method of containing the ionic compound is not particularly limited. For example, the ionic compound is dissolved in an organic solvent such as methyl ethyl ketone (MEK) or tetrahydrofuran (THF) and uniformly mixed with the organic compound. A method of removing by vacuum decompression and the like can be given.

Next, in the present invention, the polymer solid electrolyte may contain a substance capable of dissolving the ionic compound in the organic polymer. By including such a substance, the basic skeleton of the polymer solid electrolyte can be contained. Without changing the conductivity, the conductivity can be significantly improved. As the substance capable of dissolving the ionic compound, propylene carbonate, cyclic carbonate such as ethylene carbonate, cyclic ester such as γ-butyrolactone, tetrahydrofuran or a derivative thereof,
Examples thereof include ethers such as 1,3-dioxane and 1,2-dimethoxyethane, nitriles such as acetonitrile and benzonitrile, dioxolane and derivatives thereof, and sulfolane and derivatives thereof alone and a mixture of two or more thereof. However, it is not limited to these. The mixing ratio and the mixing method are arbitrary. In addition, about the coating method of the polymer solid electrolyte of the present invention, for example, roller coating such as an applicator roll, screen coating, doctor blade method,
It is desirable to apply a uniform thickness using a means such as spin coating or a bar coder, but it is not limited thereto.

The electrodes constituting a battery using the solid polymer electrolyte of the present invention include the following battery electrode materials. As the positive electrode active material, CuO, Cu ₂ O, Ag
Group I metal compounds such as ₂ O, CuS, CuSO ₄ , Ti
Group IV metal compounds such as S ₂ , SiO ₂ and SnO, V ₂ O
_{5, V 6 O 12, VOx} , Nb 2 O 5, Bi 2 O 3, Sb
Group V metal compounds such as ₂ O ₃ , CrO ₃ , Cr ₂ O ₃ ,
Group VI metal compounds such as 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 ₂ O ₃ , N
Group VIII metal compounds such as iO, CoO ₃ , CoO, or the general formula LixMXy, LixMNyX ₂ (M and N are I
Group VIII metals, X represents a chalcogen compound such as oxygen or sulfur. ), Conductive polymer compounds such as polypyrrole, polyaniline, polyparaphenylene, polyacetylene, and polyacene-based materials, and carbonaceous materials having a pseudo-graphite structure, but are not limited thereto.

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

As the positive electrode of the battery, a sheet or pellet formed by binding the above active materials with a binder is generally used. In this case, if necessary, acetylene black or the like may be carbon or metal. A conductive material such as powder can be mixed in the positive electrode to improve electron conduction. When producing a so-called positive electrode composite as described above, several kinds of dispersants and a dispersion medium can be added in order to obtain a uniform mixed dispersion system.

On the other hand, a lithium metal or lithium alloy sheet is often used for the negative electrode. However, when a carbonaceous material such as carbon is used for the negative electrode active material, a method similar to the above-described method for producing the positive electrode should be used. Can be.

The separator may be a sheet of the solid polymer electrolyte alone and disposed between the positive electrode and the negative electrode, or the separator may be formed by applying the solid polymer electrolyte composition to the positive electrode or the negative electrode, curing the mixture, and forming a composite. Is also possible.

The electrode material of the electric double layer capacitor constituting the electric double layer capacitor using the solid polymer electrolyte of the present invention is an electrode material which does not involve the capacitance of the oxide film dielectric in the electrolytic capacitor. Activated carbon or carbon fiber which has a large specific surface area and is electrochemically inert may be used. It is preferable to use a polymer solid electrolyte as a binder for these carbon materials, but there is a method using a substance other than the polymer solid electrolyte (eg, polytetrafluoroethylene). In this case, it is possible to use a polymer solid electrolyte in combination. It is possible.

[0026]

The polymer solid electrolyte of the present invention has a structure in which liquid crystal monomer chains are inserted into blocks to prevent crystallization of alkylene oxide chains exhibiting ion conductivity. It is possible to prevent crystallization or orientation between molecules of the alkylene oxide chain, and to maximize the molecular motion of the alkylene oxide chain,
It is possible to exhibit good ionic conductivity over a wider temperature range without hindering the molecular motion of the alkylene oxide chain at room temperature.

Also, by having a liquid crystal molecular chain,
Not only can a uniform polymer solid electrolyte thin film be obtained, but also a short-circuit of electrodes does not occur due to thinning, and a short-circuit does not occur even when the area of the thin film is increased. It is possible to provide. Therefore, it is possible to provide a very excellent practical solid polymer electrolyte having improved ion conductivity, reliability and workability, and a battery using the same.

[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 A solid polymer electrolyte of the present invention was synthesized by the following method. That is, the structure of Chemical Formula 40 is used as a liquid crystal molecule,

Embedded image R: C ₂ H ₄ R ′: C ₂ H ₄ X: Cl NaOH is dissolved in water at a molar ratio of 2: 1.
Reaction was conducted at 60 ° C. for 2 hours to synthesize an organic compound having the structure of Chemical Formula 41.

Embedded image R: C ₂ H ₄ R ′: C ₂ H ₄ X: Cl k: 12

Embedded image R ₁ : HR ₂ : H n: 300 An equimolar amount of polyethylene oxide was added, and the structure of Formula 43 was obtained by a dehydrochlorination reaction.

Embedded image (Wherein R ₁ , R ₂ , n, R, R ′ and k are the same as above)
An organic compound was synthesized, and this was

Embedded image R ₃ : H R ₄ : H Ethylene oxide and a small amount of lithium carbonate were added and block-polymerized to finally produce an organic polymerized product 45 of the present invention.

Embedded image (Wherein R ₁ , R ₂ , R, R ′, k, R ₃ and R ₄ are the same as above, n ′: 400, m: 100)

Next, the following operation was carried out in order to dissolve lithium perchlorate as an ionic compound in the organic polymerizer 45. That is, a lithium perchlorate / methyl ethyl ketone solution is mixed with the organic polymer so that the ratio of ethylene oxide units to Li in the organic polymer is (ethylene oxide units) / Li = 10/1, and the solution is mixed. Cast on a glass plate.
After leaving this thin film at 25 ° C. for 24 hours to remove excess methyl ethyl ketone, it was further dried under reduced pressure at 80 ° C. for 24 hours to obtain a uniform polymer solid electrolyte thin film. The thickness of the thin film was 100 μm, and the ionic conductivity of the electrolyte was measured by a complex impedance method.
It was 0 ^-4 Scm ^-1 . The ionic conductivity at -20 ° C is
It was 3.6 × 10 ⁻⁵ Scm ⁻¹ .

Regarding the flexibility of the solid polymer electrolyte, as a result of conducting a 90 ° bending test and a 180 ° bending test, no crack was generated in any case. next,
A sheet-like battery was prototyped using the solid polymer electrolyte of the present invention. Hereinafter, a method for manufacturing a sheet-shaped battery will be described in the order of a) to c).

A) Vanadium pentoxide as a positive electrode active material of a battery, acetylene black as a conductive agent, and dimethacrylic acid ester of ethylene oxide (molecular weight: 4000) and monomethacrylic acid ester of methoxylated polyethylene glycol (molecular weight: 400) ) To 7: 3
The mixture obtained by mixing the organic polymer mixed with the above was used as a positive electrode composite. The method for producing this positive electrode composite is as follows. That is, a mixture of vanadium pentoxide and acetylene black at a ratio of 85:15 was added to 10 parts by weight of the organic polymer and lithium perchlorate was added.
Parts by weight and 0.05 parts by weight of azobisisobutyronitrile were dissolved in a dry inert gas atmosphere at 1:
1 was mixed. 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 a 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 polymer solid electrolyte layer of the present invention on the lithium metal, a solution prepared by dissolving 1 part by weight of lithium perchlorate in the organic polymer of Chemical Formula 45 was cast on the lithium metal, and an inert gas was used. The composition was cured by discharging at 100 ° C. for 1 hour in an atmosphere. The thickness of the electrolyte layer thus obtained was 20 μm.

C) A sheet-shaped battery was prepared by bringing the electrolyte / lithium / negative electrode current collector obtained in b) into contact with the positive electrode current collector / positive electrode composite obtained in a).

FIG. 1 is a cross section of a sheet-shaped battery using the polymer solid electrolyte of the present invention. In the figure, 1 is a positive electrode current collector made of stainless steel, 2 is a positive electrode composite, and vanadium pentoxide is used as a positive electrode active material, acetylene black is used as a conductive agent, and dimethacrylate of ethylene oxide is methoxylated with a binder. An organic polymer mixed with monomethacrylate of polyethylene glycol was used. Reference numeral 3 denotes an electrolyte layer made of the solid polymer electrolyte of the present invention. 4 is metallic lithium, 5 is
A negative electrode current collector made of stainless steel, which also serves as the exterior. 6 is a sealing material made of modified polypropylene.

The electrode area of the sheet battery using the solid polymer electrolyte of the present invention can be variously changed depending on the manufacturing process.
One having a size of 0 cm ² was produced. Using this sheet-shaped battery, a charge / discharge cycle test was performed at 25 ° C. and a constant current of 100 μA. A charge / discharge cycle test was performed with a charge end voltage of 3.2 V and a discharge end voltage of 2.0 V. FIG. 2 shows the relationship between the number of charge / discharge cycles and the battery capacity. In FIG. 2, (1) represents the battery of Example 1, and (2) represents the battery of Comparative Example.

COMPARATIVE EXAMPLE Organic Polymerization 45 of Example 1
In place of the main chain linear type ethylene oxide (molecular weight 2
Using an organic compound having the formula (500), a sheet-like battery was prototyped in the same manner as in Example 1. As can be seen from FIG.
Sheet battery using the polymer solid electrolyte of the present invention (1)
It can be seen that shows excellent charge / discharge cycle characteristics as compared with the sheet battery (2) of the comparative example.

(Example 2) Instead of the liquid crystal molecular structure molecular chain (Chemical formula 3) of Example 1, the liquid crystal molecular structure molecular chain of Chemical formulas (4), (5), (7), (8), (9) and (11) Were prepared in the same manner as in Example 1, and their ionic conductivities at 25 ° C. and −20 ° C. were measured by a complex impedance method. Table 1 shows the results. Note that R, R ′, and k in each of the general formulas are R ₁ , R ₂ , R ₃ , and R as in Example 1.
₄ , n ′ and m are the same as in the first embodiment.

[0039]

[0040]

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[0041]

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[0042]

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[0043]

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[0044]

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[0045]

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Regarding the flexibility of these solid polymer electrolytes, as a result of conducting a 90 ° bending test and a 180 ° bending test, no crack was generated in any case.

(Example 3) Instead of the liquid crystal molecular structure molecular chain (Chemical Formula 3) of Example 1, an organic polymer is prepared using the liquid crystal molecular structure molecular chains of Chemical Formulas 13, 14, 15, and 16. 1
At 25 ° C. and −2 ° C.
The ionic conductivity at 0 ° C. was measured by the complex impedance method. Table 2 shows the results. In addition, R in each general formula,
R ′ and k are the same as in Example 1, and R ₁ , R ₂ , R ₃ , R ₄ ,
The same applies to n ′ and m as in the first embodiment.

[0048]

[0049]

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[0050]

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[0051]

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[0052]

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Regarding the flexibility of these polymer solid electrolytes, as a result of conducting a 90 ° bending test and a 180 ° bending test, no crack was generated in any case.

[0054]

As is apparent from the above description, the solid polymer electrolyte of the present invention has a liquid crystal monomer molecular chain in a block shape in order to prevent crystallization of an alkylene oxide chain exhibiting ionic conductivity. Because of the structure, the liquid crystal molecular chains prevent crystallization or orientation between the molecules of the alkylene oxide chain, and make it possible to maximize the molecular motion of the alkylene oxide chain. It is possible to exhibit good ionic conductivity over a wider temperature range without hindering movement.

Further, by having a liquid crystal molecular chain,
Not only can a uniform polymer solid electrolyte thin film be obtained, but also a short-circuit of electrodes does not occur due to thinning, and a short-circuit does not occur even when the area of the thin film is increased. It is possible to provide. From these facts, there is an effect that the performance of the polymer solid electrolyte can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a battery of the present invention.

FIG. 2 is a diagram showing the relationship between the number of charge / discharge cycles and the battery capacity.

[Explanation of symbols]

 (1) Battery of Example 1 (2) Battery of Comparative Example

Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H01B 1/06 H01B 1/06 A H01M 10/40 H01M 10/40 B // C08G 65/28 C08G 65/28

Claims (3)

(57) [Claims] 1. A block copolymer containing an ionic compound.
A polymer solid electrolyte comprising
A copolymer having a skeleton represented by the following general formula: ALB ...
Decomposition. However, A is Chemical formula 1, B is Chemical formula 2, L is Chemical formula 3 to Chemical formula 1.
At least one selected from the group consisting of Embedded image (R ₁ and R ₂ are a hydrogen atom or an alkyl having 1 or more carbon atoms.
And n is an integer of 5 to 1500. ) (R ₃ and R ₄ are a hydrogen atom or an alkyl having 1 or more carbon atoms.
And m is an integer of 0 to 1500. ) Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image (R and R ′ are an alkyl group having 1 to 10 carbon atoms and k is 1
And h is an integer of 1 to 6. ) 2. The method according to claim 1, wherein the solid polymer electrolyte is an ionic compound.
2. A substance comprising a substance capable of dissolving a substance.
The polymer solid electrolyte described above. 3. The polymer solid electrolyte according to claim 1 or 2.
Battery.