JP2619845B2 - 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 a small-sized, large-capacity coin-type (button-type) organic electrolyte battery using an organic semiconductor having a polyacene skeleton structure as an electrode.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 60-1 filed by the present applicant.
Japanese Patent No. 70163 discloses an organic electrolyte battery in which an organic semiconductor containing a polyacene-based skeleton structure is used as a positive electrode and a negative electrode. Although the battery has the features of high capacity, long life, and excellent safety, there are still many problems when it is put to practical use as a coin-type (button-type) battery. Especially high temperature storage (70 ° C, 2.5V applied)
There was a problem that the later electrical characteristics, especially the internal resistance, increased significantly as compared with the values before storage at high temperature.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies in view of the above-mentioned problems, and as a result, have found that the use of a specific electrolytic solution can solve the above-mentioned problems of the existing technology. The purpose of the completed battery is to provide a coin-type (button-type) battery having excellent high-temperature storage characteristics.

[0004]

An object of the present invention is to provide a coin including a negative electrode can and an electrode made of an organic semiconductor having a polyacene skeleton structure, a separator, a positive electrode can, and an organic electrolyte as constituent members. An organic electrolyte battery, wherein the organic electrolyte is an organic solvent solution of a tetraalkylphosphonium salt represented by the following formula:

Embedded image (Wherein R ₁ , R ₂ , R ₃ and R ₄ represent an alkyl group, which may be the same or different).

[0005] The electrolytic solution used in the battery of the present invention is a solution in which the above tetraalkylphosphonium salt is dissolved in an organic solvent. As the organic solvent, an aprotic organic solvent is preferable, and it is particularly preferable to use propylene carbonate or a mixed solvent of propylene carbonate and ethylene carbonate since the pressure resistance of the battery can be set high. The electrolytic solution is prepared at a concentration of at least 0.5 mol / l, particularly preferably at a concentration of 0.8 mol / l to 1.5 mol / l. What is important in the present invention is to use a tetraalkylphosphonium salt for the electrolyte. As the tetraalkylphosphonium salt, various ones can be applied, and tetraethylphosphonium tetrafluoroborate [(C ₂ H ₅ ) ₄ PBF ₄ ] is particularly preferable. When an insoluble and infusible substrate having a polyacene-based skeleton structure described later was used for the positive electrode and the negative electrode, tetraethylammonium tetrafluoroborate [(C ₂ H ₅ ) NBF ₄ ] was used when a tetraalkylphosphonium salt was used for the electrolyte. As compared with the case, the rise of the internal resistance after the high-temperature storage is significantly suppressed. Generally, it has been reported that both the tetraalkylphosphonium salt and the tetraalkylammonium salt have high withstand voltage, but the reason is not clear in the present invention. The problem was solved.

The positive electrode and the negative electrode of the battery of the present invention contain an organic semiconductor having a polyacene-based skeleton structure. The organic semiconductor is an insoluble and infusible substrate described in JP-A-60-170163, which is a heat-treated product of an aromatic condensation polymer and has a hydrogen atom / carbon atom ratio of 0.05. ~
0.5, an insoluble and infusible substrate having a polyacene-based skeleton structure having 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 condensate of an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde. As the aromatic hydrocarbon compound, for example, so-called phenols such as phenol, cresol and xylenol are suitable, but not limited thereto. As the aldehyde, formaldehyde,
Acetaldehyde, furfural and the like can be used, with formaldehyde being preferred. The phenol aldehyde condensate may be any of a novolak type, a resol type, or a composite thereof.

The insoluble and infusible substrate is a heat-treated product of the aromatic condensation polymer as described above, and can be produced, for example, as follows. An inorganic salt such as zinc chloride or sodium phosphate is mixed with the aromatic condensation polymer.
The amount to be mixed varies depending on the type of the inorganic salt and the shape and performance of the target electrode, but the weight ratio is 10/1 to 1/7.
Is preferred. The mixture of the inorganic salt and the aromatic condensation polymer thus obtained is formed into a desired shape such as a film or a plate, and is cured at a temperature of 50 to 180 ° C. for 2 to 90 minutes to be cured and formed. I do. 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.

[0008] This reaction is a kind of thermal condensation polymerization, and the degree of reaction is represented by the ratio of the number of atoms represented by hydrogen atoms / carbon atoms (hereinafter referred to as H / C) in the final product. The H / C value of the insoluble infusible substrate is 0.05 to 0.5, preferably 0.1 to 0.35. The obtained heat-treated body is sufficiently washed with water or diluted hydrochloric acid to remove the inorganic salt contained in the heat-treated body. Thereafter, the resultant is dried to obtain an insoluble and infusible substrate having a specific surface area of 600 m ² / g or more by a BET method.

FIG. 1 shows an embodiment of a coin-type (button-type) organic electrolyte battery according to the present invention. In the figure, 1
Is a negative electrode can, 2 is a negative electrode, 3 is a separator, 4 is a positive electrode, 5
Denotes a positive electrode can, and 6 denotes an insulating packing. An insulating packing is disposed between the positive electrode can 5 and the negative electrode can 1, and a separator 3 is disposed between the positive electrode 4 and the negative electrode 2 so as not to cause a short circuit.
The battery is sealed by swaging. The electrolyte is contained in the positive electrode 4, the negative electrode 2 and the separator 3. Therefore, a porous polypropylene film, a glass fiber nonwoven fabric, or the like is preferably used so that the separator 3 can contain an electrolytic solution.

[0010]

By using the organic solvent solution of the tetraalkylphosphonium salt according to the present invention as an electrolyte, an organic electrolyte battery having a special high-temperature storage property was obtained. Hereinafter, the present invention will be described specifically with reference to examples.

[0011]

EXAMPLE An aqueous solution obtained by mixing a water-soluble resol (about 60% concentration) / zinc chloride / water at a weight ratio of 10/25/4 was formed on a glass plate by a film applicator. Next, a glass plate was put on the aqueous solution on which the film was formed, and was heated and cured at a temperature of about 100 ° C. for 1 hour to prevent moisture from evaporating, thereby obtaining a cured product. The cured product was placed in a siliconite electric furnace, heated in a nitrogen stream at a rate of 40 ° C./hour, heat-treated to 500 ° C., and then sufficiently washed with dilute hydrochloric acid and hot water to contain a polyacene-based skeleton structure. Organic semiconductor was obtained.

The electric conductivity of the organic semiconductor is 10 ⁻⁴ (Ωc).
m) ^-1 and the H / C value by elemental analysis was 0.27;
The specific surface area by the BET method was 2,100 m ² / g.
Next, the organic semiconductor is pulverized using a ball mill to form a powder, and 5% by weight of polytetrafluoroethylene and 10% by weight of carbon black are added to the powder, mixed, kneaded, and then pressed to form a layer having a thickness of 0%. A 0.7 mm electrode sheet was obtained.
The electrode sheet was punched into a 15 mm diameter to form a positive electrode and a negative electrode, and a 2020 type (diameter 20 mm, thickness 2 m
m) Ten coin-type batteries were assembled. The following measured values are the average values measured for 10 batteries.

The separator 3 has a thickness of 100 μm.
Was used. The positive electrode can and the negative electrode can are made of stainless steel. The negative electrode can 1 and the negative electrode 2 and the positive electrode 4 and the positive electrode can 5 were bonded using a carbon-based conductive adhesive. 1.0 mol / l (C ₂ H ₅ ) ₄ P as electrolyte
Using a BF ₄ propylene carbonate solution, 0.20 cc was injected in accordance with the positive electrode 4, the separator 3, and the negative electrode 2.

After the electrodes and each component were sufficiently dried to remove water, the battery was assembled in an N ₂ dry box. The voltage at the time of producing the battery was 0 V, and the AC impedance at 1 kHz was 2.1Ω. The battery was charged by applying a voltage of 2.5 V to the battery at room temperature with an external power supply for 1 hour. The electromotive force after charging was 2.5V. Next, when constant current discharge was performed at 2 mA, it took 1.24 hours for the battery voltage to reach 0 V. Subsequently, the battery was stored for 170 hours at a high temperature of 70 ° C. applying a voltage of 2.5 V. After storage, the battery was short-circuited at room temperature for 2 hours, the battery voltage was set to 0 V, and the AC impedance was measured.

Comparative Example 1.0 mol / l in electrolyte
A battery was assembled in the same manner as in Example except that a propylene carbonate solution of (C ₂ H ₅ ) ₄ NBF ₄ was used, and the high-temperature storage characteristics were measured. Battery voltage at the time of battery creation is 0V and 1k
The AC impedance at Hz was 2.0Ω. When charging and discharging were performed in the same manner as in the example, the discharging time was 1.26 hours, and the initial characteristics did not depend on the electrolytic solution. Next, it was stored at a high temperature in the same manner as in the example, and the AC impedance after storage was 26.5Ω.
It increased more than 10 times compared to the initial stage. (C
_It can be seen that the use of ₂ H ₅ ) ₄ PBF ₄ for the electrolyte significantly improved the high-temperature storage characteristics.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a coin-type battery showing an example of an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 negative electrode can 2 negative electrode 3 separator 4 positive electrode 5 positive electrode can 6 insulating packing

Continuation of the front page Examiner Masaki Suzuki (56) References JP-A-2-239571 (JP, A)

Claims (1)

(57) [Claims] 1. A coin-type organic electrolyte battery comprising a negative electrode can, an electrode made of an organic semiconductor containing a polyacene-based skeleton structure, a separator, a positive electrode can, and an organic electrolyte as constituent members, Is an organic solvent solution of a tetraalkylphosphonium salt represented by the following formula: Embedded image (Wherein R ₁ , R ₂ , R ₃ and R ₄ represent an alkyl group, which may be the same or different)