JPH0624160B2 - Organic electrolyte battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to an organic electrolyte battery, and more particularly to an organic electrolyte battery having an insoluble and infusible substrate having semiconductor properties as a positive electrode and a negative electrode.

(Prior Art) In recent years, miniaturization, thinning or weight reduction of electronic devices has been remarkable, and accordingly, miniaturization and thinning of a battery serving as a power source,
There is a great demand for weight reduction. Currently, silver oxide batteries are widely used as small size and high performance batteries, and lithium batteries have been developed and put into practical use as thin dry batteries and small and lightweight high performance batteries. However, since these batteries are primary batteries, they cannot be used for a long time by repeating charging and discharging. On the other hand, nickel-cadmium batteries have been put to practical use as high-performance secondary batteries, but they are still unsatisfactory in terms of size reduction, thickness reduction, and weight reduction.

Further, lead-acid batteries have been conventionally used in various industrial fields as large-capacity secondary batteries, but the biggest drawback of these batteries is that they are heavy. This is fatal because lead peroxide and lead are used as electrodes. In recent years, attempts have been made to reduce the weight and improve the performance of batteries for electric vehicles, but they have not been put to practical use. However, there is a strong demand for a large-capacity and lightweight secondary battery as a storage battery.

Each of the batteries that have been put into practical use as described above has advantages and disadvantages, and they are used according to their respective applications.
There is a great need for making batteries smaller, thinner, and lighter. As a battery to meet such needs,
Recently, batteries using an organic semiconductor thin film polyacetylene doped with an electron-donating substance or an electron-accepting substance as an electrode active material have been studied and proposed. The battery has high performance as a secondary battery and has the possibility of being thin and lightweight, but has a serious drawback. That is, polyacetylene, which is an organic semiconductor, is an extremely unstable substance, which is easily oxidized by oxygen in the air and is also deteriorated by heat. Therefore, the battery must be manufactured in an inert gas atmosphere, and there is a limitation in manufacturing polyacetylene into a shape suitable for an electrode.

Further, Japanese Patent Application No. 59-24165 discloses a heat-treated product of an aromatic condensation polymer composed of carbon, hydrogen and oxygen, wherein the atomic ratio of hydrogen atom / carbon atom is 0.05 to 0.5, Moreover, the specific surface area value by the BET method is 600 m ² / g
The insoluble infusible substrate having the polyacene-based skeleton structure as described above is used as a positive electrode and / or a negative electrode, and an aprotic organic solvent solution of a compound capable of generating ions capable of doping the electrode by electrolysis is used as an electrolytic solution. A characteristic organic electrolyte battery has been proposed.

The battery is a promising secondary battery having high performance, possibility of thinning and weight saving, high oxidative stability of electrode active material, and easy molding thereof. However, some problems remain for the practical application of the battery. Among these problems, there is a problem that self-discharge is relatively large.

It is an object of the present invention to provide an organic electrolyte battery having a small self discharge.

Still another object of the present invention is to provide an organic electrolyte battery using an organic semiconductor composed of an insoluble and infusible substrate having a polyacene skeleton structure as an electrode active material.

Still another object of the present invention is to provide a secondary battery having a small internal resistance and capable of being charged and discharged for a long period of time.

(Means and Actions for Solving Problems) According to the present invention, such an object and advantage of the present invention is to provide a heat-treated product of an aromatic condensation polymer composed of carbon, hydrogen and oxygen, which is hydrogen atom / carbon atom. Atomic ratio of 0.05 ~
0.5 and a specific surface area value by the BET method of 600
In a battery having an insoluble and infusible substrate containing a polyacene-based skeleton structure of m ² / g or more as a positive electrode and a negative electrode, (A) a tetraalkylammonium salt as an electrolyte, and (B) a solvent γ-butyrolactone or γ-butyrolactone It is achieved by an organic electrolyte battery characterized by using an electrolytic solution consisting of a mixed solution of propylene carbonate and propylene carbonate.

The most important thing in the present invention is that by applying an electrolytic solution consisting of a specific electrolyte and a specific solvent to a battery having a specific electrode as a constituent element, self-discharge of the battery can be prevented. is there.

As described above, the battery according to the present invention configured by a specific electrolytic solution and a specific electrode has a particularly small self-discharge, and for example, the infusible substrate according to the present invention as an electrode is used as an electrolytic solution. The leakage current when a battery to which the specific electrolytic solution according to the invention is applied is charged at 2V is a battery in which only the electrolytic solution is replaced with the most standard (C ₂ H ₅ ) ₄ NClO ₄ 1 mol / propylene carbonate solution. 2 to 20 times less than that, and the voltage holding ratio becomes higher. Similarly, the leakage current is about 10 to 100 times smaller than that of the battery using LiClO ₄ 1 mol / acetonitrile solution as the electrolytic solution.

The solvent of the electrolytic solution used in the present invention is sulfolane or a mixed solution of sulfolane and γ-butyrolactone. Sufficient self-discharge was obtained with sulfolane alone, but γ-butyrolactone / propylene carbonate = 1
A mixed solvent of 0/0 to 2/8 (weight ratio) is preferable since it also has an effect of reducing internal resistance in addition to the effect of reducing self-discharge, and the above γ-butyrolactone / propylene carbonate = 10/0 to 5 / The mixed solution of 5 is the most preferable.

The electrolyte that can be dissolved in the solvent according to the present invention is a tetraalkylammonium salt, and specific examples thereof include those represented by the following formula.

And in the chemicals represented by the above formula (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ )
₄ NBF ₄ , (nC ₄ H ₉ ) ₄ NClO ₄ and (nC ₄ H ₉ ) ₄ NBF ₄ are particularly preferred.

It is preferable to use a sufficiently dehydrated electrolyte and solvent. The electrolytic solution is easily prepared by dissolving the electrolyte in a solvent, but the concentration of the electrolyte in the electrolytic solution is preferably at least 0.1 mol / more in order to reduce the internal resistance due to the electrolytic solution, and is usually 0.1. 2 to 1.5 mol /
Is more preferable.

The aromatic condensation polymer in the present invention is a condensation product of an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde. As such an aromatic hydrocarbon compound, so-called phenols such as phenol, cresol, and xylenol are preferable, but not limited thereto. For example, the following formula (Where x and y are each independently 0, 1 or 2
And methylene-bisphenols, or hydroxy-biphenyls and hydroxynaphthalenes. Of these, phenols, especially phenols, are suitable for practical use.

As the aromatic condensation polymer in the present invention, a modified aromatic polymer obtained by further substituting a part of an aromatic hydrocarbon compound having a phenolic hydroxyl group with an aromatic hydrocarbon compound having no phenolic hydroxyl group, such as xylene or toluene. For example, a modified aromatic polymer which is a condensate of phenol, xylene and formaldehyde can be used. As the aldehyde, not only formaldehyde but also other aldehydes such as acetaldehyde and furfural can be used, but formaldehyde is preferred. The phenol-formaldehyde condensate may be a novolac type, a resol type, or a complex thereof.

The insoluble and infusible substrate in the present invention is a heat-treated product of the aromatic condensation polymer as described above and can be produced, for example, as follows.

An aromatic hydrocarbon compound having a phenolic hydroxyl group or an aromatic hydrocarbon compound not having a phenolic hydroxyl group and an initial condensation product of an aldehyde are prepared, and an aqueous solution containing this initial condensation product and an inorganic salt is prepared. The aqueous solution is poured into a suitable mold and heated to cure and convert into a plate-like, film-like or cylindrical form in the mold, and then the cured product is heated in a non-oxidizing atmosphere at a temperature of 350 to 800 ° C. The resulting heat-treated body is washed to remove the inorganic salt contained in the heat-treated body.

The inorganic salt used together with the initial condensate is to be removed in a later step, and is added to the insoluble and infusible substrate of the present invention at 600 m ² /
An auxiliary agent for giving a specific surface area value of g or more, such as zinc chloride, sodium phosphate, potassium hydroxide or potassium sulfide. Of these, zinc chloride is particularly preferably used. The inorganic salt can be used in an amount of, for example, 0.05 to 10 times by weight the initial condensate. If the amount is less than the lower limit, the specific surface area will not be 600 m ² / g or more, and if the amount is more than the upper limit, the mechanical strength of the finally obtained molded article tends to decrease, which is not desirable.

Although the aqueous solution of the initial condensate and the inorganic salt varies depending on the kind of the inorganic salt used, it can be prepared by using, for example, 0.1 to 1 times by weight of water of the inorganic salt, and the aqueous solution is poured into a suitable mold. For example, it is heated at a temperature of 50 to 200 ° C. to mold and cure.

Further, when the above-mentioned initial condensate and the inorganic salt are mixed and made into an aqueous solution, phenolic fibers (for example, Kynol fiber manufactured by Nippon Kynol Co., Ltd.) may be mixed together, or the cloth, felt or the like made of the fibers may be mixed with the above. Molding and curing may be performed using a prepreg sufficiently impregnated with an aqueous solution.

Further, as shown in Japanese Patent Application No. 60-58604, the amount of the inorganic salt is 2.5 to 10 times the initial condensate, the viscosity of the mixed aqueous solution is adjusted to 100,000 to 100 centipoise, and the aqueous solution is heated at the time of heating. When the evaporation of water in the inside is suppressed, the initial condensate is gradually hardened by being heated in the aqueous solution, and it is also possible to grow it into a three-dimensional network structure having continuous pores with an average pore diameter of 10 μ or less. .

The cured product thus obtained is then in a non-oxidizing atmosphere (including a vacuum state) at a temperature of 350 to 800 ° C., preferably 350 to 700 ° C., particularly preferably 400 to 60.
It is heated to a temperature of 0 ° C. and heat-treated.

The preferable heating rate at the time of heat treatment is somewhat different depending on the degree of the aromatic condensation polymer to be used or its curing treatment, its shape, etc., but generally a relatively high heating rate from room temperature to about 300 ° C. It is also possible, for example, to set a rate of 100 ° C./hour. When the temperature reaches 300 ° C or higher, thermal decomposition of the aromatic condensation polymer starts, and gases such as water vapor (H ₂ O), hydrogen, methane, and carbon monoxide start to be generated. It is advantageous to heat.

Such heating and heat treatment of the aromatic condensation polymer are performed in a non-oxidizing atmosphere. The non-oxidizing atmosphere is, for example, nitrogen, argon helium, neon, carbon dioxide or the like, and nitrogen is preferably used. The non-oxidizing atmosphere may be stationary or flowing.

The obtained heat-treated body can be sufficiently washed with water, dilute hydrochloric acid or the like to remove inorganic salts contained in the heat-treated body, and then dried to obtain an atomic ratio of hydrogen atoms / carbon atoms (hereinafter referred to as H / C ratio) is 0.5
.About.0.05, preferably 0.35 to 0.1, having a polyacene skeleton structure, and having a specific surface area value of 600 according to the BET method.
An insoluble and infusible substrate having m ² / g or more is obtained.

According to X-ray diffraction (CuK _α ), the position of the main peak is 2
Expressed by θ, it exists between 20.5 and 23.5 °, and other broad peaks exist between 41 and 46 ° in addition to the main peak. Further, according to the infrared absorption nuspect, the absorbance ratio of D = D _{2000 to 2940} / D _{1560 to 1640} ) is usually 0.5 or less, preferably 0.3 or less.

That is, it is understood that the insoluble and infusible substrate has a polyacene-based benzene polycyclic structure uniformly and moderately developed among polyacene-based molecules.

If the H / C ratio is more than 0.5 or less than 0.05, the charge / discharge efficiency when using the substrate as an electrode of a secondary battery according to the method described below is not preferable.

Further, the specific surface area value of the insoluble and infusible substrate containing the polyacene skeleton structure by the BET method is extremely large because it is produced by using an inorganic salt such as zinc chloride. In the present invention, 600 m ² / g The above is used. 600
When it is less than m ² / g, for example, when charging a secondary battery using the substrate as an electrode, it is necessary to increase the charging voltage, which lowers the energy density and is likely to prevent deterioration of the electrolytic solution. Absent. As shown in Japanese Patent Application No. 60-58604, the viscosity of the aqueous solution is adjusted to 100,000 to 100 centipoise by using an inorganic salt in an amount of 2.5 to 10 times the amount of the initial condensate to prevent evaporation of water during heating. When the molded product thus cured is heat-treated in a non-oxidizing atmosphere, a porous insoluble infusible substrate of the present invention having continuous pores with an average pore diameter of 10 μm or less is obtained. It is more preferable to use the substrate as an electrode because the electrolytic solution can easily flow into and out of the details through the communication hole.

The electric conductivity of the insoluble and infusible substrate is usually 10 ^−11.
It is -10 ¹ Ω ^-1 cm ^-1 . Then, as will be described later, in the case of using it as an electrode material by doping with electrolyte ions, the conductivity is greatly increased, so that the electrode material also has a current collecting property.

Further, since the insoluble and infusible substrate can take various forms such as a film plate, when used as an electrode material, it enables a small battery, a thin battery or a lightweight battery.

The porous insoluble infusible substrate used in the present invention is 6
Despite having a large specific surface area value of 00 m ² / g or more, in reality, even if it is left in the air for a long time, there is no change in physical properties such as electric conductivity and it is excellent in oxidation stability. Further, since it has excellent heat resistance and chemical resistance, it does not cause the problem of electrode deterioration when used as an electrode material to construct a battery.

As described above, the organic electrolyte battery of the present invention uses the insoluble and infusible substrate as a positive electrode and a negative electrode, a tetraalkylammonium salt as an electrolyte, a mixed solvent of γ-butyrolactone and propylene carbonate as a solvent (including γ-butyrolactone alone). It is an organic electrolyte battery using.

The battery function of the battery of the present invention utilizes the electrochemical doping and the electrochemical undoping of the above-described electrolyte ions on the insoluble and infusible substrate used as an electrode. That is, energy is stored by doping the insoluble and infusible substrate, and is taken out as electric energy by undoping.

The shape and size of the electrode made of an insoluble and infusible substrate placed in the battery can be arbitrarily selected according to the type of the target battery, but since the battery reaction is an electrochemical reaction on the electrode surface, Advantageously, the electrodes have as large a surface area as possible. An insoluble and infusible substrate can be used as a current collector for extracting a current from the substrate to the outside of the battery, but other conductive material having corrosion resistance, for example, carbon, platinum, nickel, stainless steel or the like is used. You can also

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a basic configuration diagram of a battery according to the present invention. In FIG. 1, (1) is a positive electrode, a film-shaped or plate-shaped insoluble infusible substrate, and (2) is a negative electrode, similarly a film-shaped or plate-shaped insoluble infusible substrate. It is a fusible substrate.
After the battery is assembled, the electromotive voltage of the battery is 0 V, and the voltage is applied by an external power source to dope the both electrodes with electrolyte ions, so that the battery has the electromotive voltage. (3) and (3) 'are current collectors for extracting electric current from each electrode to the outside or supplying electric current for electrochemical doping, that is, charging, and each electrode and external terminal.
They are connected to (7) and (7) 'so that no voltage drop occurs. (4) is an electrolytic solution, which is a separator arranged for the purpose of preventing contact between the positive and negative electrodes of (5) and holding the electrolytic solution. The separator is a porous body having durable continuous pores and no electron conductivity, and a cloth, a nonwoven fabric or a porous body made of glass fiber, polyethylene or polypropylene is usually 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 electrolyte retained, flowability and strength. The positive electrode, negative electrode and separator are inside the battery case,
It is fixed so that there is no problem in practical use. Electrode shape,
The size and the like are appropriately determined according to the intended shape and performance of the battery. For example, a film-shaped electrode is suitable for manufacturing a thin battery, and a large-capacity battery can be manufactured by laminating a large number of film-shaped or plate-shaped electrodes alternately with positive and negative electrodes.

Doping or undoping may be carried out under a constant current or a constant voltage, or under conditions of varying current and voltage, but the amount of the doping agent with which the insoluble and infusible substrate is doped is determined by the carbon content of the substrate. The percentage of the number of doped ions per atom is preferably 0.5 to 20%. The battery of the present invention using an insoluble and infusible substrate as an electrode is a secondary battery that can be repeatedly charged and discharged, and its electromotive voltage is 1.0 to 3 although it depends on the doping amount (charge amount) of the battery. It is 0.5V. Further, since the specific gravity of the insoluble and infusible substrate and the electrolytic solution constituting the battery of the present invention is small, the capacity per weight is large. Regarding the power density, the power density is much higher than that of the lead storage battery, although there is a difference depending on the structure of the battery. Further, when the insoluble and infusible substrate in the present invention is used as an electrode, it is possible to manufacture a secondary battery which has a small internal resistance, can be repeatedly charged and discharged, and does not deteriorate in battery performance for a long period of time.

(Effects of the Invention) A secondary battery produced by the method of the present invention has an insoluble insoluble content containing a polyacene-based skeleton structure superior in oxidation resistance, heat resistance, moldability and mechanical strength as compared with conventionally known organic semiconductors. The fusible substrate is used as an electrode, and the tetraalkyl ammonium salt is
-A battery that uses a solution of a solution of butyrolactone and propylene carbonate dissolved in a mixed solvent as an electrolytic solution, which is downsized.
It is a secondary battery that can be made thin and lightweight, has high capacity and high output, and has a small self-discharge. The present invention will be specifically described below with reference to examples.

Example 1 An aqueous solution prepared by mixing water-soluble resol (about 60% concentration) / zinc chloride / water at a weight ratio of 10/25/4 was formed on a glass plate with a film applicator. Next, a glass plate was covered on the formed aqueous solution to prevent water 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 silicon knit electric furnace and heated at a rate of 40 ° C./hour under a nitrogen stream to 500 ° C.
Heat treatment was performed. Next, the heat-treated product was washed with dilute hydrochloric acid, washed with water, and then dried to obtain a film-shaped porous body. The thickness of the film was about 200 μm, the apparent density was about 0.35 g / cm ² , and the film had excellent mechanical strength. Next, the electric conductivity of the film was measured at room temperature by a direct current 4-terminal method to be 10 ⁻⁴ (Ω
・ Cm) ^-1 . Further, when elemental analysis was performed, the atomic ratio of hydrogen atoms / carbon atoms was 0.27. The shape of the peak from X-ray diffraction is a pattern based on the polyacene skeleton structure, and a broad main peak was present at around 20 to 22 ° at 2θ, and a small peak was confirmed at around 41 to 46 °.

When the specific surface area was measured by the BET method, it was 2
It was an extremely large value of 100 m ² / g.

Then, in a fully dehydrated mixed solvent of γ-butyrolactone and propylene carbonate (2: 1 by weight), (C ₂ H ₅ ) ₄ NCl was added.
A battery was assembled as shown in FIG. 1 using O ₂ dissolved at a concentration of 1 mol / mol as an electrolytic solution and the above insoluble and infusible substrate dried under vacuum at about 400 ° C. as a positive electrode and a negative electrode. A stainless mesh was used as the current collector, and a felt made of glass fiber was used as the separator.

The doping amount is represented by the number of ions to be doped per carbon atom of the porous film substrate.
In the present invention, the number of ions to be doped is obtained from the current value flowing through the circuit. The voltage immediately after the battery was assembled was 0V. Next, a voltage of 2.5 V was applied by an external power source, and the positive electrode was charged for about 1 hour by doping the positive electrode with ClO ₄ ⁻ ion negative electrode (C ₂ H ₅ ) ₄ N ⁺ ions. The electromotive voltage of the battery was 2.5 V as a matter of course.

Next, when the battery was discharged at a rate such that the amount of undoping per hour was 3%, the voltage of the battery returned to 0V in about 1 hour.

Next, the battery was charged again for 1 hour by applying a voltage of 2.0 V from an external power source. The leakage current flowing through the circuit at the end of charging was 5 μA. The electromotive voltage of the battery at this time was 2.0 V, but the electromotive voltage after leaving for 10 hours was examined and found to be 1.94 V, which revealed that self-discharge was extremely small.

Examples 2 to 4 A phenol resin film having a thickness of about 200 μm obtained in the same manner as in Example 1 was placed in a silicon knit electric furnace under a nitrogen flow of about 30.
The temperature was raised at a rate of ° C / hour to heat up to various predetermined temperatures shown in Table 1 to perform heat treatment. Then, it was washed with dilute hydrochloric acid and water and dried to obtain an insoluble and infusible substrate film. The obtained base film was subjected to elemental analysis and measurement of the specific surface area value by the BET method. The results are summarized in Table 1.

Next, in a fully dehydrated mixed solvent of γ-butyrolactone and propylene carbonate (3: 1 by weight), (C ₂ H ₅ ) ₄ NBF was added.
_The self-discharge was examined in the same manner as in Example 1 except that the solution in which ₄ was dissolved at a concentration of 1 mol / mol was used as the electrolytic solution, the above-mentioned substrate film was used as the positive electrode and the negative electrode. 2.
Table 1 shows the electromotive voltage when the battery was charged at 0 V and left for 10 hours.

In all cases, a small self-discharge was shown.

Example 5 The film-form insoluble infusible substrate obtained in Example 1 was used as a positive electrode and a negative electrode in a solvent prepared by sufficiently dehydrating γ-butyrolactone and propylene carbonate at a ratio (weight ratio) shown in Table 2 (C _Using a solution prepared by dissolving ₂ H ₅ ) ₄ NClO ₄ at a concentration of 1 mol / mol as an electrolytic solution, a battery was assembled and self-discharge was examined in the same pattern as in Example 1. These are summarized in Table 2.

Was examined self-discharge, except that Comparative Example 1 electrolytic solution _{(C 2 H 5) 4 NClO} 4 with 1 mol / propylene carbonate solution in the same manner as in Example 1. After charging at 2.0V and leaving for 10 hours, the electromotive voltage of the battery was 1.85V.

Comparative Example 2 Self-discharge was examined in the same manner as in Example 1 except that 1 mol of LiClO ₄ / dimethoxyethane solution was used as the electrolytic solution. When the battery was charged at 2.0V and left for 10 hours, the electromotive voltage of the battery was 1.65V.

[Brief description of drawings]

FIG. 1 shows the basic structure of the battery according to the present invention.
(1) is the positive electrode (2) is the negative electrode, (3), (3) 'is the current collector (4) is the electrolyte
(5) is a separator, (6) is a battery case, and (7) and (7) 'are external terminals.

Claims (6)

[Claims] 1. A heat-treated product of an aromatic condensation polymer composed of carbon, hydrogen and oxygen, wherein the atomic ratio of hydrogen atoms / carbon atoms is 0.05 to 0.5, and the specific surface area value by the BET method is A battery having an insoluble and infusible substrate containing a polyacene skeleton structure of 600 m ² / g or more as a positive electrode and a negative electrode, (A) a tetraalkylammonium salt as an electrolyte,
(B) An organic electrolyte battery characterized by using an electrolytic solution containing γ-butyrolactone or a mixed solution of γ-butyrolactone and propylene carbonate as a solvent. 2. The organic electrolyte battery according to claim 1, wherein the aromatic condensation polymer is a condensation product of phenol and formaldehyde. 3. The atomic ratio of hydrogen atoms / carbon atoms is 0.1 to 0.1.
The organic electrolyte battery according to claim 1 or 2, which is 0.35. 4. The organic electrolyte battery according to claim 1, wherein the insoluble and infusible substrate has a large number of communicating holes having an average pore diameter of 10 μm or less. 5. A tetraalkylammonium salt is (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NBF ₄ , (nC ₄ H ₉ ) ₄ NClO ₄ or (nC ₄
The organic electrolyte battery according to any one of claims 1 to _4, which is H ₉ ) ₄ NBF ₄ . 6. The organic electrolyte battery according to claim 1, wherein the solvent is a mixed solvent having a weight ratio of γ-butyrolactone / propylene carbonate = 10/0 to 5/5.