JPH0353748B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field of the Invention) The present invention relates to an organic electrolyte battery in which an electrode active material is an electrically conductive organic polymer material doped with an electron-donating substance or an electron-accepting substance. (Technical Background and Problems of the Invention) In recent years, electronic devices have become increasingly smaller, thinner, and lighter, and as a result, there is a strong demand for smaller, thinner, and lighter batteries that serve as power sources. Currently, silver oxide batteries are widely used as small, high-performance batteries, and lithium batteries have been developed and put into practical use as thin dry batteries and small, lightweight, high-performance batteries. However, since these batteries are primary batteries, they cannot be used for long periods of time by being repeatedly charged and discharged. On the other hand, although nickel-cadmium batteries have been put into practical use as high-performance secondary batteries, they are still unsatisfactory in terms of miniaturization, thinness, and weight reduction. Furthermore, lead-acid batteries have been conventionally used as high-capacity secondary batteries in various industrial fields, but the biggest drawback of these batteries is that they are heavy. This is fateful since 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. As described above, each of the batteries currently in practical use has advantages and disadvantages, and is used depending on the purpose, but there is a great need for smaller, thinner, and lighter batteries. As a battery that meets these needs, a battery using a thin film of polyacetylene, which is an organic semiconductor, doped with an electron-donating substance or an electron-accepting substance as an electrode active material has recently been researched and proposed. Although this battery has high performance as a secondary battery and has the potential to be made thinner and lighter, it has a major drawback. The reason is that polyacetylene, which is an organic semiconductor, is an extremely unstable substance, easily oxidized by oxygen in the air, and deteriorated by heat. Therefore, battery manufacturing must be carried out in an inert gas atmosphere, and there are also restrictions on manufacturing the battery into a shape suitable for polyacetylene electrodes. In addition, the present inventors have proposed a secondary battery in which an insoluble and infusible substrate containing a polyacene skeleton structure, which is a type of organic semiconductor, is doped with an electron-donating substance or an electron-accepting substance as an electrode active material. (Special Application No. 59-24165). This battery has high performance, has the possibility of being made thinner and lighter, has a high oxidation stability of the electrode active material, and is also easy to mold, making it a promising secondary battery. However, the insoluble and infusible substrate containing a polyacene skeleton structure, which is an electrode active material, is brittle and its molded product has poor flexibility, so it cannot be bent. Therefore, for example, when the substrate is used as an electrode, There were practical problems such as difficulty in manufacturing flexible, thin, and wide-area secondary batteries. (Purpose of the Invention) In view of the above-mentioned problems with existing batteries, the present inventors have completed the present invention as a result of intensive research. An object of the present invention is to provide a high-performance organic electrolyte battery using a structure made of an insoluble and infusible substrate containing a polyacene skeleton structure with excellent properties. Another object of the present invention is to provide a structure including a flexible polyacene skeleton structure that can be held not only in a planar shape but also in various shapes such as being rolled into a small radius of curvature. Further objects and advantages will become apparent from the description below. (Disclosure of the Invention) The above object is to obtain a non-surface area value determined by the BET method by heat-treating a phenolic fiber structure in a non-oxidizing gas atmosphere and subsequently heat-treating it in an oxidizing gas atmosphere to activate it. is 600 m ² /g or more and the atomic ratio of hydrogen atoms to carbon atoms is 0.05
A structure consisting of an insoluble and infusible substrate containing a polyacene skeleton structure of ~0.5 is used as a positive electrode and/or a negative electrode, and an aprotic organic solvent solution of a compound that can generate ions that can be doped into the electrode by electrolysis is used as an electrolyte. This is achieved using an organic electrolyte battery. The phenolic fiber structure in the present invention is an aggregate of phenolic fibers and has a certain shape and mechanical strength, such as woven fabrics such as plain weave and twill weave, knitted fabrics, non-woven fabrics, paper, etc. It is. The thickness of this structure can be freely selected from thin to thick, but preferably 0.02 to 10 mm. Also, the bulk density of the structure can be any value as long as the structure can be constructed, but it is 0.02
A range of ~0.6 is preferred. The phenolic fiber of the present invention is made by forming an initial condensate of phenols such as phenol, cresol, and xylenol and aldehydes such as formaldehyde and acetaldehyde into fibers, which are then treated with formaldehyde, etc. under heat or a catalyst such as acid or alkali. This is a fiber cured with a crosslinking agent. The fiber diameter may be any value as long as it can be bent freely, but it is 5 to 5.
100μ is suitable. The heat treatment temperature for heat-treating phenolic fiber structures in a non-oxidizing atmosphere is usually 400 to 800℃, and the preferable temperature increase conditions for heat treatment are generally a relatively large temperature increase of about 300℃ from room temperature. It is possible to use a temperature rate, for example, a rate of 100° C./hour. When the temperature exceeds 300°C, thermal decomposition of the phenolic fibers begins and gases such as water vapor, hydrogen, methane, and carbon monoxide begin to be generated, so it is advantageous to raise the temperature at a sufficiently slow rate. The heat-treated fiber structure obtained in this way is usually treated at 400 to 700°C for 30 minutes to 100 hours in an oxidizing gas atmosphere to determine the specific surface area value determined by the BET method.
The oxidizing gas should be 600 m ² /g or more, but water vapor, oxygen, air, carbon monoxide, etc. are suitable as the oxidizing gas, and it is generally mixed with a non-oxidizing gas such as nitrogen and used in the reaction system. It is preferable to do so. Through heat treatment in a non-oxidizing atmosphere and high-temperature treatment in an oxidizing gas, the phenolic fiber structure releases hydrogen and oxygen atoms through repeated thermal condensation reactions, and the molecular structure changes to a proportion of carbon atoms. It changes into a shape having an enlarged polyacene skeleton structure, and becomes a fibrous structure consisting of an insoluble and infusible black base. The atomic ratio of hydrogen atoms/carbon atoms of this insoluble and infusible substrate containing a polyacene skeleton structure is 0.05~
A range of 0.5 is preferred, and a range of 0.1 to 0.35 is particularly preferred. If the atomic ratio of hydrogen atoms/carbon atoms of this substrate exceeds 0.5, when a fiber structure made of this substrate is used as an electrode of a secondary battery by the method described later, the efficiency of charging and discharging will decrease.
On the other hand, if the atomic ratio is less than 0.05, a problem arises in the charge efficiency of charging and discharging. Further, it is preferable that the specific surface area value of the insoluble and infusible substrate containing the polyacene skeleton structure as measured by the BET method is 600 m ² /g or more. 600m ² /
If it is less than g, for example, in a secondary battery using a fiber structure made of this base as an electrode, it will be necessary to increase the charging voltage during charging, which will reduce energy efficiency and cause deterioration of the electrolyte. to invite. The atomic ratio of hydrogen atoms/carbon atoms obtained in this way is 0.05 to 0.5, and the specific surface area value by BET method is 600.
The fiber structure made of an insoluble and infusible substrate containing a polyacene skeleton structure of m ² /g can have various shapes such as felt, woven or knitted fabric, or paper, depending on the structure of the phenolic fiber structure before heat treatment. It has
It not only has excellent tensile and compressive strength, but also
Since it can be bent freely, if this heat-treated structure is used as an electrode, it is possible to design a battery of any shape, making it possible to manufacture flexible, thin, wide-area secondary batteries, etc. be. Further, the insoluble and infusible substrate containing the polyacene skeleton structure is
Since the specific surface area value determined by the BET method is as large as 600 m ² /g or more, it is thought that oxygen gas etc. can enter and deteriorate easily, but in reality, even if left in the air for a long time, the electrical conductivity etc. There is no change in physical properties and it has excellent oxidation stability. The battery in the present invention has an atomic ratio of hydrogen atoms/carbon atoms of 0.05 to 0.5, preferably 0.1 to 0.35, and
A fibrous structure made of an insoluble and infusible substrate containing a polyacene skeleton structure with a specific surface area value of 600 m ² /g or more by the BET method is used as a positive electrode and/or a negative electrode, and a compound that can generate ions that can be doped into the electrode by electrolysis is used as the positive electrode and/or negative electrode. It is produced by forming an electrolyte solution by dissolving it in an aprotic organic solvent, but compounds such as alkali metals or tetraalkylammonium that can be used in the electrolyte solution and can generate ions that can be doped into the electrode are used. Halides, perchlorates, hexafluorophosphates, hexafluoroarsenates, 4
Examples include fluoroborates, specifically LiI,
NaI, _NH4I , _LiClO4 , _LiAsF6 , _LiBF4 , _KPF6 ,
NaPF ₆ , (n-C ₄ H ₉ ) ₄ NClO ₄ , (n-
C ₄ H ₉ ) ₄ NAsF ₆ , (n-C ₄ H ₉ ) ₄ NPF ₆ , (n-
Examples include C ₈ H ₇ ) ₄ NClO ₄ and LiHF ₂ . An aprotic organic solvent is used as the solvent for dissolving the compound, such as ethylene carbonate, propylene carbonate, γ-butyrolactone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitrile,
Dimethoxyethane, tetrahydrofuran, methylene chloride, or a mixture thereof may be used, but it is important to select it in consideration of the solubility of the compound used as the electrolyte, battery performance, etc. The concentration of the above compound in the electrolyte is at least 0.1 mol/mol to reduce the internal resistance caused by the electrolyte.
It is preferably more than 0.2 to 1.5 mol/
It is even more preferable. The battery of the present invention uses a fibrous structure made of an insoluble and infusible substrate containing a polyacene skeleton structure as a positive electrode and/or a negative electrode, and uses a doping agent dissolved in an aprotic organic solvent as an electrolyte.
The cell action utilizes electrochemical doping and undoping of a doping agent to an insoluble and infusible substrate used as an electrode. That is, energy is stored or released to the outside by electrochemical doping of a doping agent into an insoluble and infusible substrate, and is extracted to the outside as electrical energy by electrochemical undoping, or is released into the interior by electrochemical undoping. Can be stored. Batteries according to the invention are divided into two types. The first type is a battery that uses a fiber structure made of an insoluble and infusible substrate containing a polyacene skeleton structure in both the positive and negative electrodes, and the second type is a battery that uses a fiber structure made of an insoluble and infusible substrate in the positive electrode. using
This is a battery that uses an electrode made of an alkali metal or an alloy thereof for the negative electrode. Specific examples of the metal include cesium, rubidium, potassium, sodium, lithium, etc. Among these, lithium is the most preferred. The shape and size of the electrode, which uses a structure made of an insoluble and infusible substrate placed inside the battery, can be arbitrarily selected depending on the intended battery, but the battery reaction is an electrochemical reaction on the electrode surface. Therefore, it is advantageous for the electrode to have as large a surface area as possible. Further, as a current collector for extracting current from the base to the outside of the battery, a base or a base doped with a doping agent may be used, but other conductive substances that are resistant to corrosion by the doping agent and the electrolytic solution, For example, carbon, platinum, nickel, stainless steel, etc. can also be used. Next, one example of an embodiment of the present invention will be explained with reference to the drawings. FIG. 1 is a basic configuration diagram of a battery according to the present invention. First, a first type of battery according to the present invention, that is, a battery using a structure made of an insoluble and infusible substrate containing a polyacene skeleton structure in both the positive and negative electrodes will be described. Reference numeral 1 denotes a positive electrode, which is an insoluble and infusible base structure containing a polyacene skeleton structure, and may be doped with a doping agent or may be undoped. Reference numeral 2 denotes a negative electrode, which is a structure of an insoluble and infusible substrate containing a polyacene skeleton structure, and may be doped with a doping agent or may be undoped.
After assembling the battery, a voltage is applied from an external power source to dope the battery with a doping agent. For example, when undoped, insoluble and infusible substrates are used for both electrodes,
The electromotive voltage of the battery after battery assembly is 0V,
By applying a voltage from an external power source and doping both electrodes with a doping agent, the battery has an electromotive force. 3 is a current collector for extracting current from each electrode to the outside or supplying current for electrochemical doping, that is, charging, and the method described above prevents voltage drop from occurring at each electrode and external terminal 7. are connected like this. 4 is an electrolytic solution in which the above-mentioned compound capable of producing ions that can be doped to both the positive and negative electrodes is dissolved in an aprotic organic solvent. The electrolyte is usually in liquid form, but it can also be used in gel or solid form to prevent leakage. A separator 5 is arranged for the purpose of preventing contact between the positive and negative electrodes and retaining the electrolyte. This separator is a porous body with continuous pores and no electronic conductivity that is resistant to electrolytes, doping agents, and electrode active materials such as alkali metals, and is usually made of a fabric made of glass fiber, polyethylene, polypropylene, etc. Nonwoven fabric or porous material is used. The thickness of the separator is preferably thin in order to reduce the internal resistance of the battery, but it is determined by taking into consideration the amount of electrolyte retained, flowability, strength, etc. Both the positive and negative electrodes and the separator are fixed in the battery case 6 so as not to cause any practical problems. The shape, size, etc. of the electrode are appropriately determined depending on the shape and performance of the intended battery. For example, to manufacture thin batteries, paper or cloth-like electrodes are suitable, and to manufacture large-capacity batteries, it is possible to manufacture large capacity batteries by laminating a large number of felt or cloth-like electrodes alternately with positive and negative electrodes. . Next, FIG. 1 will be used for the second type of battery according to the present invention, that is, the case where the positive electrode uses an insoluble and infusible base structure containing a polyacene skeleton structure, and the negative electrode uses an alkali metal or its alloy. I will explain. 1 in FIG. 1 is a positive electrode, which is a structure of an insoluble and infusible substrate, and 2 is a negative electrode, which is an alkali metal or an alloy thereof. Others 3 to 7 are the same as in the case of the first type. In this type, ie the second type, the doping mechanism, ie the operating mechanism of the cell, is further divided into two mechanisms. In the first mechanism, the insoluble and infusible substrate is doped with an electron-accepting doping agent, which corresponds to charging, and the insoluble and infusible substrate is undoped, which corresponds to discharging. For example, when an undoped insoluble infusible substrate is used as an electrode and a LiClO ₄ 1 mol/propylene carbonate solution is used as an electrolyte with lithium, the electromotive force after battery assembly is 2.5 to 3.0V. Next, when a voltage is applied from an external power source to dope the insoluble and infusible substrate with ClO ₄ ^- ions, the electromotive voltage becomes 3.5 to 4.5V. In the second mechanism, doping an insoluble and infusible substrate with an electron-donating doping agent corresponds to discharging, and undoping corresponds to charging.
For example, in the battery configuration described above, the electromotive force after battery assembly is 2.5 to 3.0V, and if the insoluble and infusible substrate is doped with lithium ions by releasing a current to the outside, the electromotive force becomes 1.0 to 2.5V. ,
When a voltage is applied from an external power source and the lithium ions are undoped, the electromotive force becomes 2.5 to 3.0V again. Doping or undoping may be carried out under constant current, constant voltage, or under conditions of varying current and voltage, but the amount of doping agent doped into the insoluble and infusible substrate depends on the carbon content of the substrate. The percentage of the number of doped ions per atom is preferably 0.5 to 20%. A battery using the insoluble and infusible base structure of the present invention as an electrode is a secondary battery that can be repeatedly charged and discharged, and its electromotive voltage varies depending on the configuration of the battery, but in the first type it is 1.0. ~3.5V, 2nd
When using the first mechanism in the type of 3.5~
The voltage is 4.5V, or 2.5 to 3.0V if the second type uses the second mechanism. Furthermore, the battery of the present invention has a particularly high energy density per weight, which is 100 to 350 WH/Kg if an appropriate amount of doping is applied. In addition, although there are differences in power density depending on the structure of the battery, it has a much higher power density than a lead-acid battery. Furthermore, the structure made of the insoluble and infusible substrate in the present invention has excellent mechanical strength and can be bent freely, so when used as an electrode, there is no breakage, etc., and it is an extremely stable material. The battery of the present invention can be repeatedly charged and discharged, and the battery performance does not deteriorate over a long period of time. (Effects of the Invention) The secondary battery manufactured by the method of the present invention has an insoluble and infusible structure that includes a polyacene skeleton structure that has superior heat resistance, oxidation resistance, and mechanical strength compared to conventionally known organic semiconductors. A structure consisting of a neutral substrate is used as an electrode, and the electrode is doped with an electron-donating or electron-accepting substance as an electrode active material, and a compound that can generate ions that can be doped into the electrode by electrolysis is used as an aprotic solvent. It is a battery that uses a dissolved electrolyte as an electrolyte, and is a high capacity, high output, long life secondary battery that can be made smaller and lighter, and can also be made flexible and thin. The present invention will be specifically explained below using Examples. Example 1 Plain-woven fabric made of phenolic fibers (Japan Kynor Co., Ltd., trade name Kynor, fabric weight 200 g/m ² )
up to 300℃ in an electric furnace under _N2 atmosphere at 100℃/
The temperature was increased at a rate of 50°C/hr from 300°C to 550°C, and heat treatment was performed at 550°C for 2 hours. Next, H ₂ O vapor was fed into the electric furnace with N ₂ gas to create an oxidizing atmosphere in the furnace, and oxidation treatment was performed at a temperature of 550 to 650° C. for 5 hours. The sample taken out of the electric furnace was a black fabric with high mechanical strength and did not break even when bent. Elemental analysis of this sample revealed that the atomic ratio of hydrogen atoms/carbon atoms was 0.12~
0.33, and the main peak in X-ray diffraction is 2θ.
It existed at 20-22°C, and a small peak was observed at 41-46°, confirming that this sample was composed of an insoluble and infusible substrate containing a polyacene skeleton structure. Further, when the specific surface area value was measured by BET method, it was 700 to 1200 m ² /g. Next, thoroughly dehydrated propylene carbonate.
LiClO ₄ was dissolved to make a solution of about 1 mol/ml. Then, a battery was assembled as shown in FIG. 1, with lithium metal as the negative electrode, the above solution as the electrolyte, and the fabric substrate as the positive electrode. A platinum mesh was used as a current collector, and a felt made of glass fiber was used as a separator. This example is a battery that utilizes the second type of first mechanism of the present invention. That is, ClO ₄ ^- which is an electron-accepting doping agent
Doping an insoluble and infusible substrate with ions corresponds to charging, and undoping corresponds to discharging. Further, the doping amount is expressed by the number of doped ions per carbon atom in the substrate, but in the present invention, the number of doped ions is determined from the value of the current flowing through the circuit during doping. The voltage immediately after the battery with the above configuration is assembled is the first voltage.
Shown in the table. Next, a voltage was externally applied to this battery, and the insoluble and infusible substrate was doped with ClO ₄ ^- ions at a constant current for 3.5 hours so that the doping amount per hour was 1%. Table 1 shows the open circuit voltage after doping. Next, a constant current is passed through the circuit so that the amount of undoping per hour is 1%.
Undoping of ClO ₄ ^-ions was carried out until the open circuit voltage reached the voltage immediately after cell assembly. Table 1 shows the undoping amount relative to the doping amount in this test as charge efficiency.

[Table] Example 2 A felt made of phenolic fiber (manufactured by Nippon Kynol Co., Ltd., basis weight 200 g/m ² ) was subjected to oxidation heat treatment in the same manner as in Example 1. However, the temperature of the oxidation treatment was 550°C. The atomic ratio of hydrogen atoms/carbon atoms was 0.30, and the specific surface area value determined by the BET method was 800 m ² /g. Next, (n-C ₄ H ₉ ) ₄ NClO ₄ was dissolved in tetrahydrofuran to prepare a solution of about 0.3 mol/mole, and this solution was used as an electrolyte. A battery was assembled using the base. A polypropylene sheet is used as the battery case, creating a thin and flexible structure. The open circuit voltage immediately after the battery was assembled was 0V.
Next, a voltage was applied from an external power supply to charge the battery by doping the positive electrode with ClO ₄ ⁻ ions and the negative electrode with (n-C ₄ H ₉ ) ₄ N ⁺ ions. The charging rate was 1% per hour for 2 hours. The open circuit voltage at this time was approximately 1.8V. Next, at approximately the same rate as during charging, ClO ₄ ^- ions and (n-C ₄ H ₉ ) ₄ N ⁺
Discharge was achieved by undoping ions. After 1.4 hours the open circuit voltage was 0 volts. Example 3 Plain-woven fabric made of phenolic fibers (Japan Kynor Co., Ltd., trade name Kynor, basis weight 200 g/m ² )
up to 300℃ in an electric furnace under _N2 atmosphere at 100℃/
The temperature was increased at a rate of 50°C/hr from 300°C to 550°C, and heat treatment was performed at 550°C for 2 hours. Next, H ₂ O vapor was sent into the electric furnace with N ₂ gas to create an oxidizing gas atmosphere inside the furnace, and oxidation treatment was performed at a temperature of 550 to 650° C. for 5 hours. 1cm from the black fabric taken out from the electric furnace
A sample piece was prepared by cutting out 5cm x 5cm (thickness 500μm). The sample piece was bent along a cylinder with a radius of 1 cm, but it could be bent without breaking. Comparative Example 1 A black fabric was produced in the same manner as in Example 3 except that the heat treatment in an oxidizing gas atmosphere was not performed. A sample piece of 1 cm x 5 cm was cut out from the fabric, and when it was bent along a cylinder with a radius of 1 cm in the same manner as in Example 3, it broke. The results of Example 3 and Comparative Example 1 show that a product with excellent flexibility can be obtained by heat treatment in a non-oxidizing gas atmosphere and then heat treatment in an oxidizing gas atmosphere.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the basic configuration of a battery according to the present invention, in which 1 is a positive electrode, 2 is a negative electrode, 3 is a current collector,
4 is an electrolyte, 5 is a separator, 6 is a battery case,
7 represents an external terminal.

Claims (1)

[Claims] 1. A heat-treated product of a phenolic fiber structure that has been heat-treated in a non-oxidizing gas atmosphere is subsequently heat-treated and activated in an oxidizing gas atmosphere, and has a specific surface area value of 600 m ² / A structure made of an insoluble and infusible substrate containing a polyacene skeleton structure having a molecular weight of at least 100 g and an atomic ratio of hydrogen atoms to carbon atoms of 0.05 to 0.5 is used as a positive electrode and/or a negative electrode, and ions that can be doped into the electrode by electrolysis are used as a positive electrode and/or a negative electrode. An organic electrolyte battery whose electrolyte is an aprotic organic solvent solution of a compound that can be produced. 2. The organic electrolyte battery according to claim 1, wherein the phenolic fiber structure is a knitted fabric or a nonwoven fabric. 3 The atomic ratio of hydrogen atoms to carbon atoms is 0.10~
0.35, the organic electrolyte battery according to claim 1 or 2. 4. Claim 1, wherein the positive electrode is a structure made of an insoluble and infusible substrate containing a polyacene skeleton structure, and the negative electrode is an alkali metal or an alloy of alkali metals.
The organic electrolyte battery according to any one of items 1 to 3. 5. The organic electrolyte battery according to claim 4, wherein the alkali metal is lithium. 6. The organic electrolyte battery according to any one of claims 1 to 3, wherein the positive electrode and the negative electrode are structures made of an insoluble and infusible substrate containing a polyacene skeleton structure. 7 Compounds that can generate dopable ions include LiClO ₄ , LiAsF ₅ , LiBF ₄ , (n-
The organic electrolyte battery according to any one of claims 1 to 6, which is C ₄ H ₉ ) ₄ NClO ₄ , (n-C ₃ H ₇ ) ₄ NClO ₄ or LiHF ₂ .