JP3215478B2 - Battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery using a solid electrolyte.

[0002]

2. Description of the Related Art As a conventional battery electrolyte, a liquid electrolyte is generally used. However, this has a problem in long-term reliability and stability because it leaks to the outside. A solid electrolyte is being studied in consideration of this point. As solid electrolytes, β-alumina, lithium iodide, lithium nitride, copper rubidium and the like are known, but these have problems in molding and film forming properties. Therefore, various studies have been made on organic solid electrolytes that can solve the problems of moldability and film formability. For example, an organic polymer electrolyte of polyethylene oxide (PEO), an organic polymer electrolyte containing a polyethylene oxide portion and a polypropylene oxide portion of a polyfunctional polyether molecular structure in a random copolymer type (JP-A-62-249361), A solid polymer electrolyte composed of an ethylene oxide copolymer containing a compound in a dissolved state (Japanese Patent Application Laid-Open No. 61-83249), and a thermoplastic polymer having no cross-links and substantially a branched chain of a homopolymer or a copolymer. Conductive polymer electrolyte using plastic solid polymer material composed of various materials
(JP-A-55-98480). However, in linear PEO, crystallization of PEO occurs at a temperature lower than the melting point (around 60 ° C.), and the ionic conductivity sharply decreases. In addition, in other polymer electrolytes, since crystallization is suppressed, conductivity at room temperature around 25 ° C. is improved, but at a temperature lower than that, sufficient conductivity that can be used for batteries is obtained. In particular, when the temperature is 5 ° C. or lower, an extreme decrease in conductivity is observed.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a battery which can be used stably even at a low temperature and has improved low-temperature characteristics.

[0004]

According to the present invention, in a battery in which at least one of a negative electrode, a positive electrode and a separator comprises a solid electrolyte obtained by doping an organic polymer with an ionic compound, the above organic polymer is represented by the general formula (1): Z -[(A) _m- (E) _p -Y] _k (1) [where Z is an active hydrogen-containing compound residue, and A is the following general formula:
(2)

[0005]

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(N is an integer of 0 to 25, R is a carbon number of 1 to 2)
0 is an alkyl group, an alkenyl group, an aryl group or an alkylaryl group), E is a group represented by — (CH ₂ CH ₂ O) —, Y is a polymerization reactive functional group, and k is an integer of 1 to 12. , M is an integer of 1 to 250, p is an integer of 1 to 450, and A and E are random copolymers.] And an organic compound having a skeleton represented by the following formula: Using an organic polymer obtained by subjecting a part having ethylene oxide added to a part thereof to a cross-linking reaction , and
Contains a substance that can dissolve the ionic compound in the polymer
By doing so , the above problem was solved.

Further, the present invention also includes a lithium battery containing a substance capable of making an ionic salt compatible with the solid electrolyte portion as described above.

The organic compound represented by the general formula or the organic compound used as a raw material of the organic polymer for the solid electrolyte is a polyether compound obtained by reacting an active hydrogen-containing compound with a glycidyl ether alone or a glycidyl ether with ethylene oxide. Or, by further reacting a reactive functional group-containing compound with the polyether compound,
It is obtained by introducing a reactive functional group into the active hydrogen group at the terminal of the main chain, and usually preferably has an average molecular weight of 50,000 or less. When introducing the reactive functional group,
Alternatively, when a cross-linking agent described below is reacted, it is preferable to partially add ethylene oxide to the molecular terminal when the glycidyl ether is reacted with ethylene oxide.

The above-mentioned active hydrogen-containing compounds include, for example, methanol, ethanol, ethylene glycol, propylene glycol, 1.4-butanediol, glycerin,
Polyhydric alcohols such as trimethylolpropane, sorbitol, shoe rose, polyglycerin, butylamine, 2-ethylhexylamine, ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, aniline, benzylamine, Amine compounds such as phenylenediamine, bisphenol A,
Examples thereof include phenolic active hydrogen compounds such as hydroquinone and novolak, and compounds having different types of active hydrogen-containing groups in one molecule such as monoethanolamine and diethanolamine. Among them, polyhydric alcohols are particularly preferable.

The glycidyl ethers to be reacted with the active hydrogen-containing compound include alkyl-, alkenyl-, aryl- or alkylaryl-polyethylene glycol glycidyl ethers represented by the following formula:

[0011]

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(Where n is an integer of 0 to 25, and R is an alkyl group, alkenyl group, aryl group or alkylaryl group having 1 to 20 carbon atoms). As a typical example, R is, for example, a linear alkyl group such as a methyl group, an ethyl group, or a butyl group, an isopropyl group,
sec-butyl group, branched alkyl group such as tert-butyl group, vinyl group, allyl group, 1-propenyl group, alkenyl group such as 1,3-butadienyl group, phenyl group, nonylphenyl group,
A aryl group or an alkylaryl group such as a tolyl group or a benzyl group, wherein n is an integer of 1 to 25, among which n is 1 to 15 and R has 1 to 12 carbon atoms;
It is preferred that

As the catalyst which can be used in the reaction, a basic catalyst such as sodium methylate, sodium hydroxide, potassium hydroxide and lithium carbonate is generally used, but an acidic catalyst such as boron trifluoride, trimethylamine, triethylamine Amine-based catalysts such as are also useful. The amount of the catalyst used is arbitrary.

As described above, the organic compound used in the present invention is a compound in which glycidyl ethers are bonded to an active hydrogen-containing compound by random copolymerization with ethylene oxide. Preferably, the amount is 1 to 250 mol per active hydrogen of the compound, and the number of moles of ethylene oxide to be randomly copolymerized with the glycidyl ether is 1 to 450 mol per active hydrogen.

[0015]

[0016]

[0017]

Further, in order to make the main chain terminal group Y a co-reactive functional group, a polymerizable reactive group is added to the main chain terminal of the polyether obtained by reacting an active hydrogen-containing compound with glycidyl ether or glycidyl ether and ethylene oxide. Although a functional group is introduced, examples of the polymerization reactive functional group include an alkenyl group such as a vinyl group, a group having an unsaturated bond such as an acryloyl group or a methacryloyl group, and a linear or cyclic moiety containing Si. The groups possessed can be mentioned. These groups are introduced into the molecule by reacting the above-described polyether with a compound having a polymerization-reactive functional group.

The compound having a polymerization-reactive functional group includes a compound having no carboxyl group in one molecule such as acrylic acid, methacrylic acid, cinnamic acid, maleic acid, fumaric acid, itaconic acid and p-vinylbenzoic acid. Those having a saturated bond and / or acid anhydrides of the above compounds such as maleic anhydride and itaconic anhydride, and / or acid chlorides of the above compounds, glycidyls such as allyl glycidyl ether and glycidyl methacrylate, methacryloyl Examples include isocyanates such as isocyanate, and compounds containing Si such as dichlorosilane and dimethylvinylchlorosilane.

Such an organic compound is crosslinked by polymerization, and this polymerization (crosslinking) reaction is carried out by light, heat, ionizing radiation or the like using a polymerization initiator or a sensitizer as necessary. Done.

Next, as the ionic compound to be doped into the organic polymer thus obtained, for example, L
_{iI, LiCl, LiClO 4, LiSCN} , LiBF 4, LiAsF 6, LiCF 3 S
O ₃ , LiCF ₃ CO ₂ , LiHgI ₃ , NaI, NaSCN, NaBr, KI, CsSC
N, AgNO _3, CuC ₁₂ Mg least Li, such as _{(ClO 4) 2, Na,} K
, Cs, Ag, Cu or Mg.
₃ ) ₄ NBF ₄ , (CH ₃ ) NBr, (C ₂ H ₅ ) NClO ₄ , (C ₂ H ₅ ) NI, (C ₃ H ₇ ) ₄
Quaternary ammonium salts such as NBr, (nC ₄ H ₉ ) ClO ₄ , (nC ₄ H ₉ ) ₄ NI, (nC ₅ H ₄ ) ₄ NI, lithium stearyl sulfonate,
Organic ion salts such as sodium octylsulfonate, lithium dodecylbenzenesulfonate, sodium naphthalenesulfonate, lithium dibutylnaphthalenesulfonate, potassium octylnaphthalenesulfonate, potassium dodecylnaphthalenesulfonate, and the like. These ionic compounds may be used in combination of two or more.

The mixing ratio of such an ionic compound is as follows:
The ionic compound is preferably 0.01 to 100 parts by weight, particularly 0.5 to 100 parts by weight of the organic compound.
It is good to be 50 parts by weight. If the compounding ratio of the ionic compound is too large, an excessive ionic compound, for example, an inorganic ionic salt is not dissociated, but merely mixed, resulting in a reduction in ionic conductivity.

The doping method of the ionic compound is not particularly limited. For example, the ionic compound may be dissolved in an organic solvent such as methyl ethyl ketone (MEK) or tetrahydrofuran (THF) and uniformly mixed with the organic compound. And a method of removing the organic solvent by vacuum decompression.

Next, in the present invention, by Ru contained a substance capable of dissolving the ionic compound contained in the organic polymer in the solid electrolyte, without changing the basic skeleton of the organic polymer, it can significantly improve the conductivity.

Examples of the substance that can dissolve the ionic compound include tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, 4,4-dimethyl-1,3-dioxolan, γ-butyrolactone, ethylene carbonate, Propylene carbonate, butylene carbonate,
Sulfolane, 3-methyl sulfone, tert-butyl ether, iso-butyl ether, 1,2-dimethoxyethane, 1,2-
Examples include ethoxymethoxyethane, ethylene glycol diethyl ether, water, or a mixture of two or more thereof. However, it is not limited to these. The mixing ratio and the mixing method are arbitrary.

As described above, the battery of the present invention comprising a solid electrolyte containing a substance capable of dissolving an ionic compound in an organic polymer includes alkaline metal batteries such as lithium, potassium, and sodium; zinc-silver chloride; Examples thereof include halogen salt batteries such as magnesium-silver chloride and magnesium-copper chloride, and proton conductive batteries such as nickel-hydrogen batteries. In particular, lithium batteries have high voltage, high energy, and high lithium ion conductivity in solid electrolytes.
Suitable for applying solid electrolyte.

Next, a lithium battery will be described as a specific example of the battery of the present invention. Generally, as described above, a lithium battery includes a positive electrode, a negative electrode, and a separator. The following are examples of the electrode active material used for the positive electrode and the negative electrode. The positive electrode active _{material, CuO, Cu 2 O, Ag} 2 O, CuS,
CuSO I metal compounds such as _{4, TiS 2, ZrO 2,} SiO 2, SnO,
Group IV metal compounds such as PbO, V ₂ O ₅ , V ₆ O ₁₃ , VO _x , Nb
Group V metal compounds such as ₂ O ₅ , Bi ₂ O ₃ , Sb ₂ O ₃ , CrO ₃ , Cr ₂ O
₃ , Group VI metal compounds such as MoO ₃ , MoS ₂ , WO ₃ , SeO ₂ , TeO ₂ , Group VII metal compounds such as MnO ₂ , Mn ₂ O ₃ , Fe ₂ O ₃ , FeO
VII such as, Fe ₃ O ₄ , Ni ₂ O ₃ , NiO, NiPS ₃ , CoO ₃ , CoO
Group I metal compound or general formula Li _x MY _y , Li _x MN _y X
Metal compounds such as _Z (M and N are metals of groups I to VIII, X represents a chalcogen compound such as oxygen and sulfur), polypyrrole,
Polyaniline, polyparaphenylene, polyacetylene,
Examples include conductive polymer compounds such as polyacene-based materials, and carbonaceous materials having a pseudo-graphite structure.

The negative electrode active material may be an alloy such as lithium metal, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, wood alloy, or the material used as the positive electrode active material. it can.

As the positive electrode of a lithium battery, a sheet in which the above-mentioned active materials are combined with a solid electrolyte is generally used. In this case, if necessary, acetylene black or the like may be made of carbon or metal powder or the like. By mixing a conductive material in the positive electrode, electron conduction can be improved. When producing a positive electrode sheet as described above, several types of dispersion media and dispersants can be added to obtain a uniform mixed dispersion. Other methods of manufacturing the positive electrode include CVD, evaporation,
There are thinning methods such as sputtering and aerosol deposition, and methods using a substance other than the solid electrolyte (for example, polytetrafluoroethylene) as the binder. In this case, the solid electrolyte can be used together.

On the other hand, pure lithium and lithium alloy sheets are often used for the negative electrode, but a method similar to the above-described method for producing a positive electrode can also be used.

The separator may be a sheet of the solid electrolyte alone and disposed between the positive electrode and the negative electrode, or a composite may be formed by applying a solid electrolyte composition solution to the positive electrode or the negative electrode. Further, a porous material such as a polypropylene nonwoven fabric or a polyolefin microporous membrane can be used as another separator material. In this case, a liquid electrolyte or a solid electrolyte may be present in the porous body. As a method for forming the composite, a positive electrode or negative electrode composition liquid can be applied to a solid electrolyte sheet or a porous body, and the method is not particularly limited.

Although the present invention is characterized in that an organic solid electrolyte is used, an inorganic solid electrolyte may be used in combination.

In the present invention, since an organic polymer composed of a monomer having a specific structure is used, the organic polymer structure becomes amorphous and further has side chains similar to the main chain, so that the crystallization temperature of the organic polymer is lowered. When an ionic compound such as a lithium salt is contained, the movement of lithium ions is facilitated, and as a result, lithium ion conductivity in a temperature range of room temperature or lower is improved, and low-temperature characteristics are excellent, and a battery of stable quality is provided. Can be obtained. Further, since the organic polymer is thermosetting, it can be formed into various shapes, and can be formed into a film having excellent adhesion to the electrode surface, so that various practical batteries can be obtained.

[0034]

Reference Example A positive electrode composite for a lithium battery was prepared by mixing manganese dioxide and acetylene black in a ratio of 85:15 and having a structure represented by the general formula (1).

[0035]

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10 parts by weight of an organic compound (1 part by weight of ethylene oxide added to the molecular terminal before introducing the polymerizable functional group), 1 part by weight of lithium perchlorate and 0.1 part by weight of azobisisobutyronitrile. A solution prepared by dissolving 05 parts by weight was mixed at a ratio of 1: 1, cast on a stainless steel substrate, and left standing at 100 ° C. for 1 hour in an inert atmosphere to be cured. The thickness of the coating formed on the stainless steel substrate was 30 μm.

Next, in order to form an electrolyte film on the positive electrode composite, 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 compound. Was cast on the positive electrode composite and cured in the same manner as described above. The thickness of the electrolyte film thus obtained was 20 μm.

The stainless steel / positive electrode composite / electrolyte composite sheet thus obtained was cut into a 1 cm × 1 cm sheet, and lithium was attached as a negative electrode on the above-mentioned electrolyte coating, and as shown in FIG. 1, the stainless steel (1) / positive electrode composite
A cell consisting of (2) / electrolyte (3) / negative electrode (4) / stainless steel (5) was prepared, and a load of 1 kg / cm ² was applied at 5 ° C. to 1 μA /
Constant current continuous tests of cm ² and 10 μA / cm ² were performed. As a result, 86% and 16% positive electrode utilization rates were recognized. Next, the same cell was stored at 80 ° C. for 30 days, and then stored at 5 ° C.
The back, the was similarly discharged at 1 .mu.A / cm ² and 10μA / cm ^2, 80% respectively, it was observed 15% of the positive electrode utilization, capacitance change due to storage was hardly observed. FIGS. 2 and 3 show the discharge curves obtained in the constant current continuous test.

Example 1 As a positive electrode composite for a lithium battery, a mixture of manganese dioxide and acetylene black in a ratio of 85:15 was mixed with 10 parts by weight of the same organic compound as in Reference Example , 1 part by weight of lithium perchlorate and Bisisobutyronitrile 0.
05 parts by weight, and a mixture of 40 parts by weight of propylene carbonate were mixed at a ratio of 1: 1 and cast on a stainless steel substrate.
It was cured by leaving it at a temperature of 1 hour for 1 hour. The thickness of the coating formed on the stainless steel was 30 μm.

Next, in order to form an electrolyte coating on the positive electrode composite, 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 compound, and propylene was dissolved. Carbonate 40
The mixture of parts by weight was cast on the positive electrode composite and cured by the same method as described above. The thickness of the electrolyte film thus obtained was 20 μm.

The stainless steel / positive electrode composite / electrolyte composite sheet thus obtained was cut into 1 cm × 1 cm.
Lithium was attached as a negative electrode on the electrolyte film to form a cell, and a load of 1 kg / cm ² was applied at 5 ° C. to 10 μA /
A constant current continuous test of cm ² and 100 μA / cm ² was performed. As a result, 97% and 92% positive electrode utilization rates were recognized.

In this embodiment, since the conductivity of the electrolyte can be increased by adding propylene carbonate, a sufficient discharge capacity can be obtained even if the discharge is performed at a current density 10 to 100 times that of the reference example. I was able to do it. Next, the same cell as above was stored at 80 ° C. for 30 days,
Thereafter, the temperature was returned to 5 ° C., and 10 μA / cm ² and 10
When discharged at 0 μA / cm ² , 96%, 90%
% Of the positive electrode was observed, and almost no change in capacity due to storage was observed. FIG. 3 shows a discharge curve (10 μA / cm ² ) obtained in this example.

Examples 2 to 7 Using the organic compounds shown in Table 1 in place of the above organic compounds,
A battery was assembled in the same manner as in Example 1 at 5 ° C. and 100 μA /
Discharge at cm ² , check initial cathode utilization,
It was stored for 30 days, and then discharged at 5 ° C. and 100 μA / cm ² , and the positive electrode utilization was examined. Table 1 shows the results. In these examples using the organic polymer according to the present invention, both the initial discharge capacity and the storage performance were good.

Example 8 As a positive electrode composite for a lithium battery, manganese dioxide and acetylene black were mixed at a ratio of 85:15, 10 parts by weight of the same organic compound as in Reference Example , 1 part by weight of lithium trifluoromethanesulfonate and Azobisisobutyronitrile (0.05 part by weight) was dissolved and γ-butyrolactone (40 parts by weight) was mixed in a ratio of 1: 1 and cast on a stainless steel substrate. It was cured by leaving it at a temperature of 1 hour for 1 hour. The thickness of the film formed on stainless steel is 30μ
m.

Next, 1 part by weight of lithium trifluoromethanesulfonate and 0.05 part by weight of azobisisobutyronitrile were dissolved in 10 parts by weight of the organic compound to form an electrolyte film on the positive electrode composite, A mixture obtained by mixing 40 parts by weight of γ-butyrolactone was cast on the above-described positive electrode composite, and cured by the same method as described above. The thickness of the electrolyte film thus obtained is 20 μm.
m.

The stainless steel / positive electrode composite / electrolyte composite sheet thus obtained was cut into 1 cm × 1 cm.
Lithium was attached as a negative electrode on the electrolyte film to form a cell, and a load of 1 kg / cm ² was applied at 5 ° C. to 10 μA /
A constant current continuous test of cm ² and 100 μA / cm ² was performed. As a result, 97% and 94% positive electrode utilization rates were observed.
Next, the same cell as described above was stored at 80 ° C. for 30 days, and then returned to 5 ° C., and the same was applied to 10 μA / cm ² and 100 μA / cm ^2.
, Discharge rates of 96% and 92%, respectively, were observed, and almost no change in capacity due to storage was observed.

Example 9 Polypyrrole was formed on a platinum plate by electrolytic polymerization as a positive electrode for a lithium battery. The amount of polypyrrole formed was 1.4 mg per cm ^{2 of} electrode area.

Next, in order to form an electrolyte film on this positive electrode, 1 part by weight of lithium perchlorate and 0.1 part by weight of azobisisobutyronitrile were added to 10 parts by weight of the same organic compound as in the reference example .
A mixture prepared by dissolving 05 parts by weight and mixing with 40 parts by weight of propylene carbonate was cast on the above-mentioned positive electrode composite, and cured by being left at 100 ° C. for 1 hour in an inert atmosphere. The thickness of the electrolyte film thus obtained was 20 μm.

The platinum / cathode / electrolyte composite sheet obtained in this manner was cut into 1 cm × 1 cm, and lithium was attached as a negative electrode on the electrolyte coating to prepare a cell.
With a load of ² m2 and a range of 2V to 4V at 5 ° C, 10
A constant current continuous discharge cycle test of μA / cm ² was performed. As a result, the initial discharge capacity was 0.1 mAh, and no large capacity decrease was observed thereafter, indicating good cycle performance.

As described above, in the embodiment of the present invention using a solid electrolyte, as expected in a normal non-aqueous electrolyte system,
No decrease in capacity due to dendrite formation of the negative electrode lithium was observed. This is probably because the use of a solid electrolyte has an effect of suppressing the growth of lithium dendrite in the electrolyte bulk. FIG. 4 shows the results of the constant current continuous discharge cycle test.

[0051]

[Table 1]

[0052]

The battery of the present invention can be stably stored for a long period of time, and can be used stably even at a low temperature.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a battery evaluation cell used in Reference Examples and Examples.

FIG. 2 is a graph showing a discharge curve at 1 μA / cm ² of a cell of a reference example .

FIG. 3 is a graph showing a discharge curve at 10 μA / cm ² of the cells of Reference Example and Example 1 .

FIG. 4 is a graph showing the results of a constant current continuous discharge cycle test of Example 3 .

[Explanation of symbols]

 1 Stainless steel 2 Positive electrode composite 3 Electrolyte 4 Negative electrode 5 Stainless steel

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Imachi 6-6 Josaicho, Takatsuki-shi, Osaka Yuasa Battery Co., Ltd. (72) Inventor Kazunari Takeda 6-6 Josaicho, Takatsuki-shi, Osaka Yuasa Battery Co., Ltd. In-house (72) Inventor Michiyuki Kono 14-1 Korihondoricho, Neyagawa-shi, Osaka (72) Inventor Kenji Honjo 2A-25-106 Noboricho, Takatsuki-shi, Osaka (72) Inventor Shigeo Mori Kyoto 35-1 Katsura-Chiyohara-cho, Nishikyo-ku, Kyoto-shi (56) References JP-A-3-200865 (JP, A) JP-A-4-36959 (JP, A) (58) Fields studied (Int. Cl. ⁷⁾ , DB name) H01M 10/40

Claims (4)

(57) [Claims] 1. A battery comprising at least one of a negative electrode, a positive electrode and a separator comprising a solid electrolyte obtained by doping an organic polymer with an ionic compound, wherein the organic polymer has a general formula (1): Z-[(A) _m- (E _P- Y] _k (1) [where Z is an active hydrogen-containing compound residue, and A is the following general formula:
(2) (N is 0 to 25 integer, R represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group, an aryl group or alkylaryl groups), E - is a group represented _{by, - (CH 2 CH 2 O} ) Y is a polymerization reactive functional group, k is an integer of 1 to 12, m is an integer of 1 to 250, p is an integer of 1 to 450, and A and E are random copolymers.] An organic compound having ethylene oxide added to a part of the molecular terminal before the introduction of Y, the organic polymer having been subjected to a cross-linking reaction , and
Lahydrofuran, 2-methyltetrahydrofuran,
1,3-dioxolan, 4,4-dimethyl-1,3-di
Oxolan, γ-butyrolactone, ethylene carbonate
G, propylene carbonate, butylene carbonate,
Sulfolane, 3-methylsulfone, tert-butyl ether
-Tel, iso-butyl ether, 1,2-dimethoxy
Ethane, 1,2-ethoxymethoxyethane, ethyleneg
Selected from the group consisting of recall diethyl ether and water
Characterized by being mixed with at least one kind of substance . 2. The organic compound having an average molecular weight of 50,0.
2. The battery according to claim 1, wherein the value is not more than 00. 3. The battery according to claim 1, wherein the solid electrolyte contains a substance capable of dissolving an ionic compound. 4. The battery according to claim 1, wherein said battery is a lithium battery.