JP2619842B2 - Organic electrolyte battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electrolyte battery,
More specifically, a mixture of an insoluble infusible substance having a polyacene skeleton structure and a metal oxide was used as a positive electrode active material, and lithium was supported on a molded body containing the insoluble infusible substrate and a thermosetting resin on a negative electrode. The present invention relates to an organic electrolyte battery using the same.

[0002]

2. Description of the Related Art In recent years, a secondary battery using a conductive polymer, a transition metal oxide or the like as a positive electrode and lithium or a lithium alloy as a negative electrode has a high energy density.
It has been proposed as a battery replacing Cd batteries and lead batteries. However, these secondary batteries repeatedly charge and discharge, the positive electrode,
Alternatively, the capacity is greatly reduced due to the deterioration of the negative electrode, and a problem remains in practical use. In particular, the deterioration of the negative electrode involves the formation of moss-like lithium crystals called dentite, and the repetition of charging and discharging eventually causes the dentite to penetrate the separator, causing a short circuit inside the battery, and in some cases, the battery exploding There was also a problem in terms of safety.
In recent years, research on lithium batteries in which lithium is supported on a carbon material such as graphite and a conductive polymer such as polyacetylene and polyparaphenylene has been advanced. However, although the generation of dendrites is extremely small, there is a problem that a change in the structure is large with respect to lithium in / out, and the cycle characteristics are deteriorated.

On the other hand, the present inventors have previously described an insoluble and infusible substrate having a polyacene-based skeleton structure as an organic semiconductor as a positive electrode,
A secondary battery that can be applied to both negative electrodes has been proposed (Japanese Unexamined Patent Publication No.
0-170163). The battery has cycle characteristics,
Although it is excellent in safety in addition to battery performance such as quick chargeability, improvement of battery capacity or battery voltage has been left as an issue. In addition, the present applicant has previously proposed a battery using a mixture of an insoluble infusible substrate containing a polyacene-based skeleton structure and a metal oxide for the positive electrode, and using lithium or the above insoluble infusible substrate for the negative electrode. (JP-A-63-314759). The battery has a high capacity, and although there is little decrease in capacity especially in rapid discharge,
When lithium is used for the negative electrode, there is a problem that deterioration due to the above-described dendrites is large, and when an insoluble and infusible substrate is used, a high voltage cannot be obtained.

[0004]

In view of the above problems, the present inventors have made intensive studies and completed the present invention. An object of the present invention is to provide a secondary battery having a high voltage and capable of being charged and discharged for a long time. Another object of the present invention is to provide a secondary battery having good rapid charge / discharge characteristics. Still another object of the present invention is to provide a secondary battery having excellent safety. Still another object of the present invention is to provide a secondary battery which is easy to manufacture. Still other objects and advantages of the present invention will become apparent from the following description.

[0005]

The object of the present invention is to provide an organic electrolyte battery comprising a positive electrode, a negative electrode and a solution of a lithium salt in an aprotic organic solvent as an electrolytic solution, wherein (1) the positive electrode comprises (a) A) a heat-treated aromatic condensation polymer having an atomic ratio of hydrogen atom / carbon atom of 0.5 to 0.05;
And (b) a mixture of a metal oxide and an insoluble and infusible substrate having a specific surface area value of at least 600 m ² / g by a BET method. It is a heat-treated product of a system condensation polymer having an atomic ratio of hydrogen atom / carbon atom of 0.5 to 0.5.
The present invention is attained by an organic electrolyte battery characterized in that 3% or more by mole of lithium is supported on a molded body containing a thermosetting resin and an insoluble and infusible substrate containing a polyacene-based skeleton structure of No. 05 in a molar percentage.

The insoluble and infusible substrate having a polyacene skeleton structure (hereinafter referred to as PAS) according to the present invention is an aromatic base described in Japanese Patent Application Laid-Open No. 59-3806 filed by the present applicant. It is obtained by subjecting the condensation polymer to heat treatment under specific conditions. PAS having a specific surface area of 600 m ² / g or more according to the BET method can be obtained by the method described in Japanese Patent Application Laid-Open No. Sho 60-170163 filed by the present applicant. Specifically, when a high specific surface area is not required, that is, when the present invention is used for a negative electrode, it can be obtained as follows, for example.
As the aromatic condensation polymer used in the present invention,

(A) a condensate of an aromatic hydrocarbon compound having a phenolic hydroxyl group such as a phenol-formaldehyde resin and an aldehyde, (b) a xylene-modified phenol, a formaldehyde resin (a part of phenol is substituted by xylene ), Aromatic hydrocarbon compounds having no phenolic hydroxyl group, aromatic hydrocarbon compounds having no phenolic hydroxyl group, condensates of aldehydes, and (c) furan resins. The aromatic condensation polymer is gradually heated to a suitable temperature of 400 ° C. to 1000 ° C., preferably 600 ° C. to 800 ° C. in a non-oxidizing atmosphere (including a vacuum state) to obtain hydrogen atoms / carbon atoms. When the heat-treated product has an atomic ratio (hereinafter, referred to as H / C) of 0.50 to 0.05, preferably 0.35 to 0.10.

In the case of a PAS having a specific surface area of 600 m ² / g or more according to the BET method used for a positive electrode or a negative electrode in the present invention, an inorganic salt such as zinc chloride or sodium phosphate is mixed with the above-mentioned aromatic condensation polymer. The mixing amount varies depending on the type of the inorganic salt and the shape and performance of the target electrode, but is preferably from 10/1 to 1/7 by weight. The mixture of the inorganic salt and the aromatic condensation polymer thus obtained varies depending on the composition of the polymer, the kind of the inorganic salt and the like, but is usually cured at a temperature of 50 to 180 ° C. by heating for 2 to 90 minutes, thus. The obtained cured product is
Then, the mixture is heated to a temperature of 350 to 800 ° C., preferably 400 to 750 ° C. in a non-oxidizing atmosphere, and the obtained heat-treated body is sufficiently washed with water or dilute hydrochloric acid to contain the heat-treated body. To remove inorganic salts.
Then, when this is dried, H / C = 0.50 to 0.0
A PAS having a specific surface area of at least 600 m < ² > / g, preferably from 0.35 to 0.10, is obtained. In the PAS used in the present invention, the position of a main peak in X-ray diffraction (Cukα ray) occurs at 24 ° or less at 2θ and 41 ° to 2 ° at 2θ.
Those showing a broad peak between 46 ° are preferred. The PAS in the present invention is manufactured into a powder or short fiber shape or in an appropriate shape so that it can be easily molded.
It is preferable to use PAS processed into a short fiber shape or the like.

The PAS used for the positive electrode of the present invention is the above-mentioned PAS.
Of S, those having H / C = 0.5 to 0.05 and specific surface area value of 600 m ² / g or more by BET method are used. H / C
When the ratio exceeds 0.5, the charge efficiency of charge and discharge of the battery of the present invention is deteriorated, and when the H / C ratio is less than 0.05, the capacity of the battery is undesirably reduced. When the specific surface area by the BET method is less than 600 m ² / g, for example, ClO
₄ , BF _{4 and the} like having a relatively large ion radius are difficult to dope smoothly, and it is necessary to increase the charging voltage, which is not preferable. As the metal oxide used for the positive electrode of the present invention, lithium ion intercalation, or those capable of deintercalation,
Among them, transition metal oxides are preferred. More preferably,
Vanadium, chromium and manganese oxides, especially V
Vanadium oxides typified by ₂ O ₅ and V ₆ O ₁₃ are preferred. The positive electrode in the present invention is obtained by mixing PAS and a metal oxide in the form of a powder or the like. Specifically, PAS and a metal oxide in a form that is easy to mix such as powder are mixed with a binder, and a conductive material is added as necessary, and the mixture is sufficiently mixed, and if necessary, kneaded and then molded. Where P
The mixture of AS and metal oxide depends on the use of the battery and the type of PAS and metal oxide, but the weight ratio of PAS / metal oxide is preferably 95/5 to 15/85. 95 /
If it exceeds 5, the effect of the metal oxide is small, while 15
If the ratio is less than / 85, the battery loses rapid charge / discharge properties.

The type of the conductive agent is not particularly limited, and a metal powder such as nickel metal may be used. However, a carbon-based material such as activated carbon, carbon black, acetylene black, and graphite is particularly preferable. The mixing ratio varies depending on the electric conductivity of the insoluble and infusible substance, the composite ratio of the composite, and the like, but it is appropriate to add 40 to 2% to the total weight of the composite. The type of the binder is not particularly limited as long as it is insoluble in the electrolytic solution in the present invention described later. For example, a rubber-based binder such as SBR, a fluorine-based resin such as polytetrafluoroethylene, a thermoplastic resin such as polypropylene and polyethylene Resins are preferred, and the mixing ratio is preferably 20% or less based on the total weight of the composite. PAS used for the negative electrode of the present invention
Used is H / C = 0.5 to 0.05 obtained by the above method. PAS suggests that the aromatic polycyclic structure is moderately developed and that the average distance of the planar polyacene skeleton structure is relatively large, so that PAS can stably support lithium.

When the H / C is less than 0.05, the structure of the substrate tends to be changed when lithium is carried or when lithium is taken in and out (during charging and discharging), and the cycle characteristics are deteriorated. When H / C exceeds 0.5, lithium cannot be stably supported, and a battery manufactured using such a negative electrode in which lithium is supported on PAS has a large self-discharge. In the present invention, a molded article containing at least a PAS supporting lithium and a thermosetting resin can be roughly divided into the following two methods. The first method is to use PAS in a form that can be easily mixed, such as powder or short fiber.
And the initial condensate of the thermosetting resin are kneaded by adding a solvent such as methanol, toluene or water, if necessary.
It is a method of pressure molding simultaneously with curing under heating at 00 ° C,
In the second method, the PAS in the above-described form is mixed with a binder generally used for battery electrodes such as polytetrafluoroethylene, polyethylene, and polypropylene, or kneaded and molded as necessary, and then, This is a method of impregnating the molded article with a solution of an initial condensate of a thermosetting resin, followed by drying and curing by heating or the like.

The thermosetting resin in the present invention is PA
Materials that can firmly adhere S powder and the like to prevent the electrode from loosening, such as phenol resin and melamine resin furan resin. The molded body thus obtained may be optionally
Heat treatment in an inert atmosphere (including vacuum) can also be used. For example, when a phenolic resin is used as a thermosetting resin, a large amount of hydroxyl groups, carbonyl groups, and the like that easily react with lithium are present, and extra lithium is required when lithium is supported. It is advantageous to keep the groups reduced. The heating temperature is 150 ° C. or higher, preferably from 250 ° C. to 500 ° C., and as the temperature increases, the electrode strength decreases, and it becomes difficult to obtain the original effects of the present invention.

The ratio of the thermosetting resin in the above-mentioned molded product is PA
It is determined by the shape of S, the specific surface area of PAS, the amount of other kinds of binders, the amount of lithium to be supported, and the like. Preferably, the proportion occupying in the electrode is 1% or more and 70% or less by weight, more preferably 5% or more. 50% or less. If it is less than 1%, the effect of suppressing the loosening of the electrode is small, and if it is more than 70%, the amount of PAS is naturally reduced, so that sufficient lithium cannot be carried, and the battery capacity decreases. The negative electrode applied to the organic electrolyte of the present invention is obtained by supporting lithium on a molded article containing PAS and a thermosetting resin obtained by the above-described method or a heat-treated product of the molded article. The method for supporting lithium may be appropriately selected from known methods such as an electrolytic method, a gas phase method, a liquid phase method, and an ion implantation method. For example, when lithium is supported by the electrolytic method, the PAS molded body is immersed in an electrolyte containing lithium ions as a working electrode, and between the counter electrode in the same electrolyte,
Apply current or apply voltage. Further, it can also be supported by a method in which an appropriate amount of lithium foil is brought into direct contact with the above-mentioned molded body. When the gas phase method is used, the PAS compact is exposed to, for example, lithium vapor. When the liquid phase method is used, for example, a complex containing lithium ions is reacted with an insoluble and infusible substrate. Examples of the complex used in this reaction include, but are not limited to, an alkali metal naphthalene complex and an alkoxide.

The amount of lithium supported on the PAS by the above-mentioned method is 3% or more, preferably 10% or more, expressed as a molar percentage (percentage of the number of lithium to one carbon atom of the PAS). The amount of lithium varies depending on the specific surface area of the PAS, and it is preferable to support lithium so that the potential of the PAS compact supporting lithium is 1.0 to ⁰ V with respect to Li / Li ⁺ . When the amount of lithium is small, the voltage of the battery of the present invention decreases, and when the amount is large, excessive lithium precipitates on the surface of the PAS molded body, which is not preferable. When lithium is supported on a PAS compact obtained by molding the PAS powder or the like by a conventionally known method without using a thermosetting resin, the electrode has a large slack and sufficient cycle characteristics cannot be obtained. , The internal resistance increased, rapid discharge became difficult, and sufficient cycle characteristics could not be obtained.

In particular, when a PAS having a comparatively high surface area is used, the amount of lithium carried is large, so that the electrode is easily loosened by the conventional method, and the effect of the present invention is apparent. In other words, it has been confirmed that PAS having a specific surface area of 600 m ² / g or more by the BET method can reduce the internal resistance of the battery due to the high diffusion rate of Li in the substrate, but there is a problem in the molding method and it cannot be used in practice. However, by using the method of the present invention, a high-performance battery can be obtained.

As a solvent constituting the electrolytic solution used in the present invention, an aprotic organic solvent is used. Examples of the aprotic organic solvent include, for example, ethylene carbonate, propylene carbonate, γ-butyrolactone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitrile, dimethoxyethane, tetrahydrofuran, dioxolan, methylene chloride, sulfolane, or a mixture of these aprotic organic solvents. Any mixture of more than one species may be used.

The electrolyte mixed or dissolved in a single solvent may be any electrolyte capable of generating lithium ions. As such an electrolyte, for example, Li
I, LiClO ₄ , LiAsF ₆ , LiBF ₄ , or L
iHF _{2 and the} like. The above electrolyte and solvent are mixed in a sufficiently dehydrated state to form an electrolyte. The concentration of the electrolyte in the electrolyte is at least 0.1 mol / l or more in order to reduce the internal resistance due to the electrolyte. And more preferably 0.2 to 1.5 mol / l. As a current collector for extracting a current to the outside of the battery, a conductive material having corrosion resistance to a doping agent and an electrolytic solution, for example, carbon, platinum, nickel, stainless steel, or the like can be used.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating the basic configuration of a battery according to the present invention. In FIG. 1, (1) is a positive electrode, and (2) is a negative electrode. (3) and (3 ') are current collectors, which are connected to each electrode and the external terminals (7) and (7') so as not to cause a voltage drop. (4) is an electrolytic solution in which the above-mentioned compound capable of generating ions that can be doped is dissolved in an aprotic organic solvent. The electrolyte is usually liquid, but may be used in a gel or solid state to prevent liquid leakage. (5) is a separator arranged for the purpose of preventing contact between the positive and negative electrodes and holding the electrolytic solution.

The separator is a porous material having a non-electron conductive material having continuous air holes that are durable with respect to an electrolytic solution or an electrode active material such as a doping agent or an alkali metal. Usually, a cloth, a nonwoven fabric or a porous body made of glass fiber, polyethylene or polypropylene is used. The thickness of the separator is preferably thin in order to reduce the internal resistance of the battery, but is determined in consideration of the amount of retained electrolyte, flowability, strength, and the like. The positive and negative electrodes and the separator are fixed in the battery case (6) so that there is no practical problem. The shape, size, and the like of the electrode are appropriately determined depending on the shape and performance of the intended battery.

[0020]

The organic electrolyte battery of the present invention has a PAS
By using a mixture of metal oxides and a PAS bonded with a thermosetting resin carrying lithium on the negative electrode, a secondary battery with high capacity, high voltage and excellent long-term cycle characteristics is used. Battery. Hereinafter, the present invention will be described specifically with reference to examples.

[0021]

【Example】

(1) Method for producing PAS An aqueous solution in which a water-soluble resol (about 60% concentration), zinc chloride and water were mixed at a weight ratio of 10: 25: 4 was formed into a film on a glass plate using a film applicator. Next, a glass plate was placed on the formed aqueous solution to prevent moisture from evaporating, and then heated at a temperature of about 100 ° C. for 1 hour to be cured. The phenol resin film was placed in a siliconite electric furnace and heated at a rate of 10 ° C./hour in a nitrogen atmosphere at 650 ° C.
(PAS1) Heat treatment was performed to 500 ° C. (PAS2). Next, the heat-treated product was washed with dilute hydrochloric acid, washed with water, and then dried to obtain a PAS film having a high specific surface area.
This PAS film was pulverized with a disk mill to obtain a PAS powder. The H / C ratio of PAS1 and PAS2 was 0.17 and 0.22, respectively, and the specific surface area values by the BET method were 1850 m ² / g and 2100 m ² / g.

Next, PAS2 powder 70 parts, V ₂ O ₅ powder 3
0 parts, 10 parts of polytetrafluoroethylene powder, and 20 parts of acetylene black were sufficiently mixed with milk stick, and then formed into a film of about 500 μm with a roller to obtain a positive electrode. PAS1
After sufficiently mixing 100 parts of the powder and 10 parts of the polytetrafluoroethylene powder, a film of about 500 μm was formed with a roller. Subsequently, the film is immersed in a methanol solution (about 20% concentration) of a resol type phenol resin precondensate,
After impregnating with the phenol resin, it was dried and cured at 100 ° C. for 4 hours. The weight of the film before impregnation relative to the film before impregnation was 1.24. 200 μm
Of Li foil (lithium carrying amount about 55%)
When left in a 1 / l LiClO ₄ -propylene carbonate solution for 48 hours, the Li metal foil completely disappeared, and all the Li could be supported on the PAS compact. This Li-supported PAS was used as a negative electrode.

A battery as shown in FIG. 1 was assembled using the above positive and negative electrodes. A stainless steel wire mesh was used as a current collector, and a felt made of glass fiber was used as a separator. In addition, a 1 mol / l LiClO ₄ -propylene carbonate solution was used as an electrolytic solution. The electromotive voltage of the battery was 2.9V. A voltage of 4.0 V was applied to the above battery from an external power source for about 1 hour, charging was performed, and then 1 mA /
The battery was discharged to 2.0 V at a current density of cm ² to determine the initial capacity. Further, this charge / discharge cycle was repeated and measured up to 100 times. When the initial capacity was 100, the capacity at the 100th time was 92.

[0024]

Comparative Example 1 A battery was assembled in the same manner as described below without impregnating the PAS used for the negative electrode with the phenol resin, and the electromotive voltage of the battery was 2.6 V. The cycle characteristics were measured in the same manner. When the initial capacity was 100, the capacity at the 100th time was 61.

[0025]

COMPARATIVE EXAMPLE 2 A battery was assembled in the same manner as in the example, except that no Li foil was attached to the negative electrode (without carrying Li). The electromotive voltage of the battery was 0.3V. The cycle characteristics were measured between 4V-2V and 2V-0V by the same method. When the initial capacity is set to 100, the 100th capacity is 4V-
The value was 52 for 2V and 88 for 2V-0V.
The stable operating voltage of the battery was low because no Li foil was attached.

[Brief description of the drawings]

FIG. 1 is a diagram showing the basic configuration of a battery according to the present invention, wherein (1) is a positive electrode, (2) a negative electrode, (3) and (3 ') are current collectors, and (4).
Is an electrolytic solution, (5) is a separator, (6) a battery case,
(7) and (7 ') represent external terminals.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-233862 (JP, A) JP-A-4-34870 (JP, A)

Claims (1)

(57) [Claims] 1. An organic electrolyte battery comprising a positive electrode, a negative electrode and a solution of a lithium salt in an aprotic organic solvent as an electrolyte, wherein (1) the positive electrode is (a) a heat-treated aromatic condensation polymer; Hydrogen atom / carbon atom ratio is 0.5 to 0.05
And (b) a mixture of a metal oxide and an insoluble and infusible substrate having a specific surface area value of at least 600 m ² / g by a BET method. It is a heat-treated product of a system condensation polymer having an atomic ratio of hydrogen atom / carbon atom of 0.5 to 0.5.
An organic electrolyte battery comprising a molded body containing a thermosetting resin and an insoluble infusible substrate containing a polyacene-based skeleton structure of No. 05 and supporting lithium by 3% or more by mole percentage.