JPH05315007A - Solid electrolyte cell - Google Patents

Abstract

PURPOSE:To get a solid electrode cell which has good characteristics, particular ly excellent charge-and-discharge efficiency by using a film, as an electrolyte, made up by hardening a composition whose main component is a specified high molecular compound. CONSTITUTION:A film obtained by hardening a composition made up of acryloile modified polyalkylene oxide containing an acrylode group structure expressed by Formula I and a polyalkylene oxide structure expressed by Formula II, inorganic salt and a crown ether compound obtained by heating or irradiating such an active light as ultraviolet ray, visible light, electron beam, etc., is used as an electrolyte. As an example of the acryloile modified polyalkylene oxide, triethylene glycol monoacrylate, etc., and as an example of the inorganic salt, LiClO4, LiI, etc., and as an example of the crown ether, 1, 4, 7, 10- tetraoxacyclododecane, etc., may be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolyte battery containing a polymer compound as a main component.

[0002]

2. Description of the Related Art Liquid electrolytes conventionally used as battery electrolytes have a problem of long-term reliability because liquid leaks to the outside of parts and elution of electrode substances easily occur. On the other hand, the solid electrolyte does not have such a problem, and has the advantage that the structure of the parts of each device can be simplified and that the thinning of the parts allows the parts to be made lighter and smaller. Since these features meet the requirements for small, lightweight, and highly reliable parts that accompany the progress of electronics, their research and development are being actively conducted.

As the solid electrolyte material, conventionally, mainly inorganic substances such as β-alumina, silver oxide, rubidium and lithium iodide have been known. However, it is often difficult to mold and form an inorganic material into an arbitrary shape, and since it is generally expensive, there are many problems in practical use.

On the other hand, high molecular substances (polymers) have the advantage that a uniform thin film can be easily processed into an arbitrary shape, so solid electrolytes using various polymers have been proposed so far. That is, polyethylene oxide, polypropylene oxide, polyethyleneimine, polyepichlorohydrin, etc. are used as base polymers, and Li, Na
Solid electrolyte compositions comprising a combination with an inorganic salt such as the above and batteries using these compositions have been already disclosed (for example, JP-A-55-98480 and JP-A-58-108).
No. 667, No. 58-188062, No. 58-1880
63, and U.S. Pat. No. 4,576,882). However, compositions of these polymers and inorganic salts have insufficient ionic conductivity for practical use, and improvements have been demanded.

For example, Japanese Patent Application Laid-Open No. 58-82477 discloses a solid electrolyte having a reticulated structure of a composition comprising polyethylene oxide, an alkali metal salt and a polymer capable of forming a reticulated structure. However, since the polyethylene oxide used here has a high molecular weight and easily forms a crystalline complex with an alkali metal salt, its ionic conductivity is insufficient. Also disclosed is an ion conductive solid electrolyte obtained by curing a composition comprising an acryloyl-modified polyalkylene oxide and an inorganic salt, or a composition obtained by further adding polyethylene alkylene glycol or an organic solvent (JP-A-63-94501). No. 63-94
563 and 63-135477).

Further, an ionic conductor containing a fluorine-containing polymer such as polyvinylidene fluoride and its copolymer and an inorganic salt as main components is known (Japanese Patent Laid-Open No. 59-14960).
No. 1, JP-A-60-31554).

A method of adding crown ether to high molecular weight polyethylene oxide is also known (J. Ele).
ctrochem. Soc. , Vol. 137, 38
30 (1990)). In these solid electrolytes,
Along with ionic conductivity, there is a problem that the cation transport number which is an important characteristic is low. That is, it is considered that the migration of both cations and anions generated by the dissociation of the inorganic salt contributes to the ionic conductivity, but when used as the electrolyte of the battery, the migration of the anion decreases the stability of the electrolyte, and therefore the charge of the battery is reduced. When the discharge cycle is repeated, there is a problem that the efficiency drops sharply. Therefore, it is desirable that the ratio of ionic conductivity contribution by cations, that is, the cation transport number is as high as possible. As a method for improving the cation transport number, for example, Japanese Patent Laid-Open No. 61-47713 discloses a solid electrolyte using a copolymer of lithium methacrylate and methyl ether oligoethylene oxide methacrylic acid ester. However,
Although this solid electrolyte has a high cation transport number, it has a drawback of low ionic conductivity.

[0009]

The present invention provides a solid electrolyte battery having excellent characteristics.

[0010]

The present invention has the general formula

[Chemical 1] (In the formula, R ₁ represents hydrogen or a lower alkyl group) and an acryloyl group structure represented by the general formula

[Chemical 2] (Wherein, R ₂ represents hydrogen or a lower alkyl group, and n represents an integer of 1 to 30) and an acryloyl-modified polyalkylene oxide, an inorganic salt and a crown ether compound. The present invention relates to a solid electrolyte battery using a thin film obtained by curing a composition as an electrolyte.

Specific examples of the acryloyl-modified polyalkylene oxide in the present invention include, for example, triethylene glycol monoacrylate, tetraethylene glycol monoacrylate, polyethylene glycol monoacrylate, methoxytetraethylene glycol monoacrylate, phenoxytetraethylene glycol monoacrylate, Methoxy polyethylene glycol monoacrylate, triethylene glycol monomethacrylate, polyethylene glycol monomethacrylate, methoxy polyethylene glycol monomethacrylate, polyethylene glycol cinnamate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, triethylene glycol trimethylolpropane triacryl DOO, and ethylene glycol structure in the above compounds can be used as the compound was changed to propylene glycol structure. The molecular weight of the acryloyl-modified polyalkylene oxide is not particularly limited,
Usually, the molecular weight is 200 to 10,000, preferably 250 to
The one of 3000 is used. Further, two or more kinds of the above-mentioned acryloyl-modified polyalkylene oxide can be used in combination.

Specific examples of the inorganic salt in the present invention include:
LiClO ₄ , LiI, LiSCN, LiBF ₄ , Li
AsF ₆ , LiCF ₃ SO ₃ , LiPF ₆ , NaI, N
aClO ₄ , NaSCN, NaBr, KI, CsSC
An inorganic salt containing one of alkali metals or alkaline earth metals such as N, AgNO ₃ , CuCl ₂ , and Mg (ClO ₄ ) ₂ can be used. In addition, an ammonium salt containing a quaternary nitrogen, that is, (CH ₃ ) ₄ NSCN,
(CH ₃ ) ₄ NClO ₄ , (CH ₃ ) ₄ NCl, (CH
₃ ) ₄ NBr, (CH ₃ ) ₄ NBF ₄ , (C ₂ H ₅ ) _{4
NSCN, (C 2 H 5)} 4 NClO 4, (C 2 H 5) 4
_{NCl, (C 2 H 5)} 4 NBr, (C 2 H 5) 4 NCF
₃ SO ₃ , (C ₆ H ₅ ) (CH ₃ ) ₃ NCl, (C ₆ H
_{5) (CH 3) 3 NBr} , (C 6 H 5) (C 2 H 5) 3
_NBr, it is possible to use an inorganic salt such as _{(C 6 H 5) (C} 2 H 5) 3 NBF 4.

The content of the above-mentioned inorganic salt is (inorganic salt / EO) × 100 (mol%) based on the alkylene oxide unit (hereinafter abbreviated as EO) of acryloyl-modified polyalkylene oxide and polyalkylene glycol. It is preferably 0.05 to 50 mol%, more preferably 0.
The amount is 1 to 30 mol%. If the content of the above-mentioned inorganic salt is too large, the excess inorganic salt does not dissociate, but simply mixes, and the ionic conductivity is reduced. Also, if the content is too small, the number of dissociated ions is reduced, and the ionic conductivity is reduced. Further, two or more kinds of the above inorganic salts can be used in combination.

Specific examples of the crown ether in the present invention include 1,4,7,10-tetraoxacyclododecane, 1,4,7,10,13-pentaoxacyclopentadecane (hereinafter abbreviated as 15Cr5), 1 , 4, 7, 1
0,13,16-hexaoxacyclooctadecane,
2,3,11,12-dibenzo-1,4,7,10,1
3,16-hexaoxacyclooctadeca-2,11-
Diene, 2,3,11,12-dicyclohexyl-1,
4,7,10,13,16-hexaoxacyclooctadecane or the like can be used.

In the present invention, polyalkylene glycol or an organic solvent may be added in addition to the above-mentioned three components of acryloyl-modified polyalkylene oxide, inorganic salt and crown ether. The polyalkylene glycol preferably has a molecular weight of 2000 or less,
Examples thereof include tetraethylene glycol, hexaethylene glycol, octaethylene glycol, and mono- or dimethyl ethers thereof, and compounds in which the ethylene glycol structure of the above compound is replaced with a propylene glycol structure.

Specific examples of the organic solvent include propylene carbonate, γ-butyrolactone, ethylene carbonate, diethyl carbonate, tetrahydrofuran, acetonitrile, dimethoxyethane, dimethylsulfoxide, dioxolane and sulfolane. The content of the polyalkylene glycol or the organic solvent is preferably 500% by weight or less, more preferably 4% by weight based on the acryloyl-modified alkylene oxide.
It is not more than 00% by weight. If the content of the polyalkylene glycol or the organic solvent is too large, the mechanical properties of the cured product deteriorate, which is not preferable in practice. Two or more polyalkylene glycols can be used in combination.

The ion conductive solid electrolyte of the present invention is prepared by adding a polyalkylene glycol or an organic solvent.
As the ionic conductivity is improved by plasticization,
The interaction between the acryloyl-modified polyalkylene oxide, the inorganic salt and the crown ether components and the polyalkylene glycol or the organic solvent has the effect of improving the ion conductivity and the cation transport number.

As a method for curing the composition of the present invention comprising each of the above-mentioned components, a heating method or a method of irradiating with actinic rays such as ultraviolet rays, visible rays and electron rays is preferably used.

In the case of the above heating method, if necessary, it is preferable to add a peroxide such as benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxy carbonate or the like to the above composition.

Further, in the case of the method of irradiating with the above-mentioned actinic rays, if necessary, the above-mentioned composition is added to the composition as benzoin, 2-methylbenzoin, trimethylsilylbenzophenone, 4-methoxybenzophenone, benzoin methyl ether, It is preferable to add acetophenone, anthraquinone, 2,2-dimethoxy-2-phenylacetophenone, and the like.

As a method of curing and thinning the above composition, a substrate such as a metal such as aluminum and stainless steel or a substrate such as glass is coated with the above composition, for example, by roller coating, doctor blade, bar coder, sicle screen, or Using a means such as spin coating, apply to a uniform thickness to form a coating film,
Examples of the method include heating the coating film or irradiating the coating film with an actinic ray to cure and thin the coating film.

Although the thin film of the electrolyte synthesized as described above may be stuck on the electrode active material, the above composition or composition solution is applied on the battery active material and cured to form a thin film. Good.

As the negative electrode active material in the present invention, lithium, a lithium alloy such as lithium and aluminum,
Examples include alloys with mercury and zinc.

The positive electrode active material is not particularly limited, but examples thereof include manganese dioxide, molybdenum trioxide, vanadium pentoxide, titanium or niobium sulfides, chromium oxides and copper oxides. The material is further mixed with graphite as a conductive agent and, if necessary, a binder, for example, polytetrafluoroethylene, which is pressure-molded and used as a positive electrode plate.

The battery formation in the present invention is carried out, for example, as follows. A mixture of graphite and Teflon powder as a binder is mixed with a positive electrode active material, which is pressure-molded and further heat-treated to prepare a positive electrode plate. Further, as the negative electrode active material, for example, a foil of lithium metal is coated with the above-mentioned electrolyte composition and cured to form a thin film of a solid electrolyte. to this,
A battery can be obtained by stacking the positive electrode plates described above.

[0026]

The solid electrolyte battery of the present invention has excellent characteristics, especially excellent charge / discharge efficiency.

[0027]

EXAMPLES Examples of the present invention will be described below. Example 1 (1) Preparation of Electrolyte Composite Membrane Polyethylene oxide (EO chain) as a side chain as a monomer
A mixture of 1.35 g of methoxy polyethylene glycol methacrylate (M-90G manufactured by Shin-Nakamura Chemical Co., Ltd.) and 0.45 g of polyethylene glycol dimethacrylate (9G manufactured by Shin-Nakamura Chemical Co., Ltd.) was added to propylene carbonate of LiBF ₄ . Solution (LiBF ₄ concentration 1.0m
ol / dm ³ ) 4.20 g, and 15Cr5 as a crown ether in propylene carbonate solution (15Cr
0.067 g of 5 concentrations of 0.1 mol / dm ³ was added.
Next, as a photopolymerization initiator, 2,2-dimethoxy-2-
Phenylacetophenone 0.4 wt% was added, and UV light was irradiated for 900 seconds by an ultraviolet lamp 6W (FL6BLB manufactured by Toshiba) to polymerize the mixture. Thereby, a transparent polyethylene oxide-grafted polymethylmethacrylate composite film (thickness 1.0 mm) was obtained.

(2) Preparation of manganese-based composite oxide positive electrode Chemically synthesized manganese dioxide and lithium hydroxide (LiOH)
Was mixed with Mn: Li = 7: 3 (molar ratio), mixed well in an agate mortar, put in a quartz bow, and placed at 375 ° C. in an electric furnace.
It was baked for 20 hours. 20 mg of powdered acetylene black as a conductive agent with respect to 30 mg of the obtained composite oxide,
And powdered polytetrafluoroethylene 5 mg as a binder
Was added and mixed well in an agate mortar. The mixture was made into pellets by using a tablet molding machine, in which case nickel (Ni) mesh (manufactured by Nippon Bulb Industries Co., Ltd .: 100
A mesh (diameter 13 mm, thickness 0.1 mm) was pressure bonded. Molding conditions are 4500 kg / cm after 5 minutes of pre-evacuation
Pressurization was performed while evacuating at ² for 30 minutes. The obtained positive electrode is a pellet having a thickness of 0.5 mm. The pellets were calcined in air at 100 ° C. for 24 hours before use.

(3) Constant current charge / discharge measurement 13 Manganese-based composite oxide positive electrode prepared in (2) Diameter 13
The electrolyte composite membrane prepared in (1) was sandwiched between the mm-sized pellet and the lithium electrode negative electrode pressed onto a Ni mesh having a diameter of 13 mm, and a model cell was tightened with a Teflon screw. In addition, the diameter 1 between the current collector and the electrode
By inserting a 2 mm Ni plate, the electrolyte composite membrane was prevented from being damaged when the cell was tightened. 0.1 m
Charge / discharge is performed at a constant current density of A / cm ² , and the charge end voltage and the discharge end voltage are + 3.75V and + 2.5V, respectively.
(Vs. Li ^/ Li ⁺ ) was measured by a method of starting discharge immediately after battery preparation. FIG. 1 shows a plot of the discharge capacity for each charge / discharge cycle.

Example 2 A model cell was prepared in the same manner as in Example 1 except that the concentration of the 15Cr5 propylene carbonate solution was 0.1 mol / dm ³ . FIG. 1 shows a plot of the discharge capacity for each charge / discharge cycle.

Comparative Example A model cell was prepared in the same manner as in Example 1 except that 15Cr5 was not added. FIG. 1 shows a plot of the discharge capacity for each charge / discharge cycle.

[0032]

[Brief description of drawings]

FIG. 1 is a plot of discharge capacity for each cycle of repeated charging and discharging.

Claims (1)

[Claims] 1. A general formula: (Wherein R ₁ represents hydrogen or a lower alkyl group) and an acryloyl group structure represented by the general formula: (Wherein, R ₂ represents hydrogen or a lower alkyl group, and n represents an integer of 1 to 30) and an acryloyl-modified polyalkylene oxide, an inorganic salt and a crown ether compound. A solid electrolyte battery using a thin film obtained by curing a composition as an electrolyte.