JP2532879B2 - Method for manufacturing electrode for organic electrolyte battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an electrode for an organic electrolyte battery.

[Prior Art] In recent years, miniaturization, thinning, or weight reduction of electronic devices has been remarkable, and accordingly, there has been a great demand for miniaturization, thinning, and weight reduction of a battery serving as a power source. Currently, silver oxide batteries are widely used as small size and high performance batteries, and thin dry batteries and lithium batteries have been developed and put into practical use as 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 into practical use as high-performance secondary batteries, but they are still unsatisfactory in terms of miniaturization, thinning, and weight reduction.

In addition, lead storage batteries have conventionally been used in various industrial fields as large capacity secondary batteries, but the biggest disadvantage 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.

As described above, the batteries currently put into practical use each have advantages and disadvantages, and are used properly according to the application, but there is a great need for making the batteries smaller, thinner, or lighter. As a battery that meets such needs, a battery that uses a thin film polyacetylene, which is an organic semiconductor, doped with an electron donor or an electron acceptor as an electrode active substance has recently been studied and proposed. Although this battery has high performance as a secondary battery and has the potential of being thinner and lighter, it has major drawbacks. That is, polyacetylene, which is an organic semiconductor, is a very unstable substance, is easily oxidized by oxygen in the air, and is transformed 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 Laid-Open No. 60-170163 applied for by the applicant of the present application
Japanese Patent Laid-Open Publication No. 2003-187242 discloses a heat-treated product of an aromatic condensation polymer composed of carbon, hydrogen and oxygen, which has a polyacene skeleton structure in which the atomic ratio of hydrogen atoms / carbon atoms is 0.5 to 0.05 and is determined by the BFT method. An insoluble and infusible substance having a specific surface area of at least 600 m ² / g 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 in the electrode by electrolysis is used as an electrolytic solution. An organic electrolyte battery characterized by the above has been proposed.

The battery is a promising secondary battery having high performance, possibility of thinning and weight saving, high oxidation stability of electrode active material, and easy molding thereof. However, the battery still has some points to be improved. That is, to increase the capacity of the battery.

[Problems to be Solved by the Invention] An object of the present invention is to produce a high-performance, thin and lightweight battery, which has high oxidation stability, is easy to mold, and enables a high battery capacity. Another object of the present invention is to provide an electrode for an organic electrolyte battery.

[Means for Solving Problems] The present inventor has surprisingly found that a simple means of subjecting an electrode substance of the type disclosed in JP-A-60-170163 described above to an acid treatment makes it possible to obtain a battery. The present invention has been completed by finding that the capacity can be improved by about 10 to 30%.

That is, the present invention relates to a method for producing an electrode for an organic electrolyte battery, which is a heat-treated product of an aromatic condensation polymer composed of carbon, hydrogen and oxygen, and has a hydrogen atom / carbon atom atomic ratio of 0.5 to 0.05. Has a skeletal structure and B
This is a method characterized in that an insoluble infusible substance having a specific surface area value of at least 600 m ² / g by the ET method is acid-treated with sulfuric acid, nitric acid, phosphoric acid, sulfurous acid or a mixture thereof.

The insoluble and infusible substance is a heat-treated product of an aromatic condensation polymer and has an atomic ratio of hydrogen atoms / carbon atoms of 0.05 to 0.
5. An insoluble and infusible substance having a polyacene skeleton structure with a specific surface area of 600 m ² / g or more as measured by the BET method.

The aromatic condensation polymer as a raw material is, for example, a condensation product of an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde. Suitable aromatic hydrocarbon compounds include, but are not limited to, so-called phenols such as phenol, cresol, and xylenol.

As the aldehyde, formaldehyde, acetaldehyde, furfural and the like can be used, and formaldehyde is preferable. The phenol aldehyde condensate may be a novolac type, a resole type, or a complex thereof.

The insoluble and infusible substance 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.

The aromatic condensation polymer described above is mixed with an inorganic salt such as zinc chloride or sodium phosphate. Thereby, porosity can be imparted to the insoluble and infusible substance. The amount to be mixed varies depending on the type of the inorganic salt and the shape and performance of the target electrode, but is preferably 10/1 to 1/7 by weight. Also,
To obtain a substance that is porous and has communicating pores,
It is preferable to use the inorganic salt in an amount of 2.5 to 10 times by weight the amount of the aromatic condensation polymer. The mixture of the inorganic salt and the aromatic condensation polymer thus obtained is formed into a desired shape in the form of a film or a plate, and is cured and molded by heating at a temperature of 50 to 180 ° C. for 2 to 90 minutes. .

The cured product thus obtained is then heated in a non-oxidizing atmosphere to a temperature of from 350 to 800C, preferably from 350 to 700C, particularly preferably from 400 to 600C. By this heat treatment, the aromatic condensation polymer undergoes a dehydrogenation dehydration reaction, and a polyacene skeleton structure is formed by the condensation reaction of the aromatic ring.

This reaction is a type of thermal condensation polymerization, and the degree of reaction is represented by the atomic number ratio of hydrogen atoms / carbon atoms (hereinafter referred to as H / C) in the final product. The H / C value of the insoluble and infusible substance is 0.05 to 0.5, preferably 0.1 to 0.35. When the H / C value of the insoluble and infusible substance is larger than 0.5, the polyacene skeleton structure is undeveloped and the electric conductivity is low, which is not preferable. On the other hand, when the value of H / C is smaller than 0.05, carbonization has progressed too much, and the performance as an electrode is low.

The heat-treated body thus obtained is thoroughly washed with water, diluted hydrochloric acid or the like to remove the inorganic salt contained in the heat-treated body. Then, this is dried to obtain an insoluble and infusible substance having a specific surface area of 600 m ² / g or more by the BET method.

In the method of the present invention, the insoluble infusible substance is sulfuric acid,
Acid treatment with nitric acid, phosphoric acid, sulfurous acid or a mixture thereof. The acid-treated insoluble and infusible substance thus obtained is
Although the reason is not clear, it is considered that the electrode material has a large capacity because it can store a larger amount of ions in the inside as compared with an insoluble infusible substance that has not been acid-treated.

Since the insoluble and infusible substance is a very stable substance, it is preferable that the acid treatment is performed under strong acidity. Acids that can be used for the acid treatment are sulfuric acid, nitric acid, phosphoric acid, sulfurous acid or a mixture thereof. As the method of acid treatment, any method of bringing an insoluble and infusible substance into contact with an acid can be performed. As a general method, the above-mentioned acid or solution thereof and the insoluble and infusible substance are brought into contact with each other at room temperature or preferably under heating. Mixing acids creates an extremely strong oxidizing atmosphere such as aqua regia, mixed acid,
An insoluble and infusible substance can be immersed in this. Alternatively, a method of placing an insoluble and infusible substance in acid vapor can be adopted. The required acid concentration, treatment temperature and treatment time are interrelated, and it is preferable to raise the treatment temperature when the acid concentration is lowered, for example. Appropriate conditions can be easily determined by experiments, and reference can be made to Examples 1 and 2 below, especially 3 below.

The acid-treated insoluble infusible substance thus obtained is probably oxidized, and there are elements which were not present in the insoluble infusible substance before the acid treatment. For example, H ₂ SO ₄ ,
Elemental sulfur is present when treated with H ₂ SO ₃ , and elemental nitrogen is present when treated with HNO ₃ . The acid-treated insoluble and infusible substance can be used as an electrode of an organic electrolyte battery, and the capacity of the battery is increased by 10 to 30% as compared with a battery using the acid-treated insoluble and infusible substance.

Here, the organic electrolyte battery is typically the positive electrode or negative electrode, or both positive and negative electrodes, the acid-treated insoluble infusible substance, it is possible to generate ions capable of doping the acid-treated insoluble infusible substance by electrolysis An organic electrolyte battery using a solution of a compound dissolved in an aprotic organic solvent as an electrolytic solution.

Whether the acid-treated insoluble and infusible substance is used only for the positive electrode, only the negative electrode, or both the positive and negative electrodes depends on the application of the battery, for example. For example, when an acid-treated insoluble and infusible substance is used for the positive electrode and Li metal or an alloy containing Li is used for the negative electrode, a power source battery with high electromotive voltage can be obtained. When the acid-treated insoluble infusible substance is used for the negative electrode and the electrode made of the acid untreated insoluble infusible substance is used for the positive electrode, a capantor type battery for backup such as IC is obtained.

As the compound capable of generating ions that can be doped into the electrode, for example, a halide of alkali metal or tetraalkylammonium, a perchlorate and the like are used.

Specifically, LiI, NaI, KI, NH ₄ I, LiClO ₄ , LiBF ₄ , LiAsF ₆ , Li
PF ₆ , NaClO ₄ , NaBF ₄ , NaAsF ₆ , NaPF ₆ , KClO ₄ , KBF ₄ , KAsF ₆ , KPF
₆ , (C ₂ H ₅ ) ₄ NClO ₄ , (n-C ₄ H ₉ ) ₄ NClO ₄ , (t-C ₄ H ₉ ) ₄ N
_{ClO 4, (C 2 H 5} ) 4 NBF 4, (n-C 4 H 9) 4 NBF 4, (t-C 4 H 9) 4
NBF ₄ , (C ₂ H ₅ ) ₄ NPF ₆ , (n-C ₄ H ₉ ) ₄ NPF ₆ , (t-C ₄ H ₉ ) ₄
It is a compound such as NPF ₆ , LiB (CH ₃ ) ₄ , LiB (C ₂ H ₅ ) ₄ , LiB (C ₆ H ₅ ) ₄ , LiHF ₂ .

An aprotic organic solvent is used as a solvent for dissolving the compound. Examples thereof include ethylene carbonate, propylene carbonate, γ-butyrolactone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitrile, dimethoxyethane, tetrahydrofuran, sulfolane, dioxolane, methylene chloride, and mixtures thereof. Among them, the material is selected in consideration of the solubility of the compound used as the electrolyte, battery performance, and the like.

The concentration of the compound 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 more preferably 0.2 to 3 mol / normal.

[Effect of the Invention] According to the present invention, by using an insoluble infusible substance treated with an acid as an electrode of an organic electrolyte battery, the battery capacity can be significantly improved.

[Examples] Hereinafter, the present invention will be further described with reference to Examples. The battery used for measuring the battery capacity in the examples has a structure as shown in FIG.

In FIG. 1, 1 is a positive electrode, 2 is a negative electrode,
Reference numerals 3 and 3'are current collectors for extracting current from each electrode to the outside or supplying current for charging, and are connected so as not to cause a voltage drop to each current and the external terminals 7 and 7 '. ing. 4 is an electrolytic solution, and 5 is a glass separator. The positive and negative electrodes and the separator are fixed in the battery case 6 so that there is no practical problem.

Example 1 (1) An insoluble and infusible substance was prepared.

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, place a glass plate on the formed aqueous solution to prevent water from evaporating, then
It was cured by heating at a temperature of 0 ° C. for 1 hour.

The phenol resin film was placed in a siliconite 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 is about 200 μm,
The apparent density was about 0.35 g / cm ³ , and the film was excellent in mechanical strength. Next, the electric conductivity of the film was measured at room temperature by a DC 4-terminal method and found to be 10 ⁻³ Scm.
Elemental analysis showed that the atomic ratio of hydrogen atoms / carbon atoms was
It was 0.27.

When the specific surface area was measured by the BET method, it was 2100 m
It was an extremely large value of ² / g.

(2) The insoluble and infusible substance was placed in concentrated sulfuric acid at 100 ° C. for 30 minutes for acid treatment. Next, wash thoroughly with distilled water, 70 ℃
And dried under reduced pressure for 12 hours.

Elemental analysis of the acid-treated insoluble infusible substance and the insoluble infusible substance not treated with acid was carried out by the techniques of CHN analysis and fluorescent X-ray analysis. The results of elemental analysis are summarized in Table 1. As shown in Table 1, a new element S, which was not contained in the untreated insoluble infusible substance, was contained in the acid-treated insoluble infusible substance.

(3) A battery was assembled as shown in FIG. 1 using the acid-treated insoluble and infusible substance as a positive electrode and lithium metal as a negative electrode. The doping amount in the battery is represented by the number of ions doped per carbon atom, and in the present invention, the number of doped ions is obtained from the sum of the current values flowing in the circuit at the time of doping. 1 mol / LiClO ₄ / as electrolyte
A propylene carbonate solution was used. The voltage immediately after the battery was assembled was 3.1V, and the battery was charged by applying a voltage of 4V. After charging for 1 hour, the electromotive voltage was measured and found to be 4V. Next, the undoped amount per hour is 5%
When discharged at a rate of, the time required for the voltage of the battery to reach 2 V was 80 minutes.

Comparative Example 1 The characteristics of the battery were measured in the same manner as in Example 1 (3) except that the acid-treated insoluble infusible substance used in Example 1 (3) was replaced with an untreated insoluble infusible substance. The result of Comparative Example 1
The results are shown in Table 2 together with the results of Example 1. The present invention significantly improved the capacity.

Example 2 (a) Using the insoluble infusible substance obtained in Example 1 (1) as a positive electrode and the acid-treated insoluble infusible substance prepared in Example 1 (2) as a negative electrode, a battery was prepared as shown in FIG. Teamed up. Immediately after the battery was assembled, the electromotive voltage was 0.1V. Next, the battery was charged by applying a voltage of 2.5 V from an external power source. Next, when the discharge amount per hour was 5% with respect to the carbon atoms of the acid-treated insoluble and infusible substance, the voltage of the battery became 0 V in about 50 minutes.

Comparative Example 2 A battery was assembled and the capacity was measured in the same manner as in Example 2 except that the negative electrode was also an acid untreated insoluble and infusible substance. The discharge time was about 40 minutes. Comparing Example 2 above according to the present invention with Comparative Example 2, it is clear that the present invention significantly improved the capacity.

Example 3 Example 1 (2) except that the acid treatment is performed under the conditions shown in Table 3.
An acid-treated insoluble and infusible substrate was obtained in exactly the same manner as in. Next, a battery was assembled by the method of Example 1 (3) and the capacity was measured.

[Brief description of drawings]

FIG. 1 shows a basic configuration according to the present invention.
Is a positive electrode, 2 is a negative electrode, 3, 3'is a current collector, 4 is an electrolytic solution, 5 is a separator, 6 is a battery case, and 7 and 7'are external terminals.

Claims (3)

(57) [Claims] 1. A method of manufacturing an electrode for an organic electrolyte battery, comprising:
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 0.5.
Acid treatment of sulfuric acid, nitric acid, phosphoric acid, sulfurous acid, or a mixture thereof, which has a polyacene skeleton structure of ~ 0.05 and a specific surface area by BET method of at least 600 m ² / g A method characterized by the following. 2. The method according to claim 1, wherein the aromatic condensation polymer is a condensation polymer of phenol and formaldehyde. 3. The method according to claim 1, wherein the acid treatment is carried out with sulfuric acid, nitric acid, phosphoric acid or a mixture thereof.