JPH10154512A - Positive electrode material for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase capacity per unit weight of a positive electrode material by constituting it of a conductive high polymer of a structure having an oxidation-reduction active quinone functional group or a conductive high polymer containing a unit having an oxidation-reduction active quinone type functional group in its repetitive structure. SOLUTION: A positive electrode material is obtained as follows. That is, an aromatic compound containing two or more methoxy groups and one or more amino groups is contained as a reaction matrix in a molecule as shown in a chemical formula 1. An aqueous solution or the like containing an inorganic acid such as a perchloric acid or an organic acid such as an acetic acid is also used as electrolyte. Oxidation-polymerization of these matrix is performed by an electrolytic method, and an insoluble conductive high polymer film is obtained on an electrode, and this is formed as a positive electrode material. For example, amino benzene and the like such as 2,5-dimethoxy aniline having two methoxy groups in a meta position or an ortho position as shown in the chemical formula 1 (1), exists as the aromatic compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode material for a secondary battery, and more particularly to a positive electrode material for a secondary battery having higher energy density per unit weight and higher energy density per unit volume than conventional ones.

[0002]

2. Description of the Related Art A nonaqueous electrolyte secondary battery using lithium, lithium alloy or a carbon material capable of containing lithium as a negative electrode has a high electromotive force and a higher energy density than conventional lead storage batteries and nickel cadmium storage batteries. Is expected. The use of metal sulfides such as titanium disulfide and molybdenum disulfide and metal oxides such as lithium cobalt oxide and lithium nickel oxide as positive electrode materials for such secondary batteries has been studied, and practical batteries have been developed. ing.

However, these materials have resource problems, and are not optimal electrode components from the viewpoint of material supply in a situation where a large battery is required in a wide field such as a power supply for an electric vehicle.

Certain organic conductive polymers, such as polyaniline and polypyrrole, have electrical conductivity and exhibit redox activity, and thus secondary batteries using such materials as positive and / or negative electrode materials have been devised. . Organic conductive polymers are
Compared with the above-mentioned metal sulfides and metal oxides, there are fewer problems in terms of material supply, and there is an advantage that those having various structures and properties can be synthetically designed.

[0005]

However, in a battery using, for example, polyaniline as a positive electrode material, doping and undoping of an anion of an electrolyte occur during charging and discharging of the battery. Therefore, the electrolyte required in the battery container is equal to or greater than the oxidation-reduction equivalent of the positive electrode material. As a result, the energy density of the battery can be much lower than the value expected only from the electrode components. Therefore, there is a demand for a polymer material that does not involve movement of an electrolyte during the charge and discharge process of a battery and has a high charge and discharge capacity.

The present invention has been made in view of such circumstances, and has been made of a conductive polymer having a structure having a redox-active quinone-based functional group or a unit having a redox-active quinone-based functional group. An object of the present invention is to provide a positive electrode material for a secondary battery having a larger capacity per unit weight than that of a conventional positive electrode material for a secondary battery, by adopting a configuration made of a conductive polymer contained therein.

[0007]

Means for Solving the Problems The first invention of the present application is a positive electrode material for a secondary battery, comprising a conductive polymer having a structure having a quinone-based functional group having redox activity. A second invention of the present application is a positive electrode material for a secondary battery, comprising a conductive polymer containing a unit having a quinone-based functional group having redox activity in its repeating structure.

The present inventors have found that the cathode material of the present invention comprises a conductive polymer characterized by having at least one or more redox-active quinone functional groups, and at least one or more redox-active quinone functional groups. Is a conductive polymer that contains a unit having a unique quinone-based functional group in its repeating structure, and has a significantly higher capacity density due to a higher number of mobile electrons per molecular structure than conventional conductive polymers. ,
In addition, they have found that a secondary battery using this as a positive electrode has a high energy density because the necessary minimum amount of the electrolyte is small, thereby realizing a high-performance secondary battery.

The method for obtaining the cathode material of the present invention will be described below. First, aminobenzenes having two methoxy groups at the meta or ortho position, for example,
2,5-dimethoxyaniline shown in (1),
3,3-dimethoxyaniline shown in (2),
3,6-dimethoxy-1,2-diaminobenzene represented by (3), aminonaphthalenes having two methoxy groups at the meta or ortho position, for example, 5,5 represented by the following formula (4)
8-dimethoxy-1-aminonaphthalene,
5,6-dimethoxy-1-aminonaphthalene shown in (5) or aminoanthracenes having two methoxy groups in the meta or ortho position, for example, 1,4,6,9 shown in the following chemical formula (6) Including, as a reaction substrate, an aromatic compound containing two or more methoxy groups and one or more amino groups in the molecule, such as -tetramethoxy-5-aminoanthracene;
Using an aqueous solution or an organic solvent solution containing an inorganic acid such as perchloric acid, hydrochloric acid or sulfuric acid or an acetic acid, methanesulfonic acid, or an organic acid such as trifluoromethanesulfonic acid as an electrolyte, and performing oxidative polymerization of those substrates by an electrolytic method,
An insoluble conductive polymer film is obtained on the electrode.

[0010]

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At this time, the organic solvent is not particularly limited as long as it can dissolve both the reaction substrate and the electrolyte. However, in order to obtain a polymerization product efficiently,
A mixed solvent with water can also be used. In order to increase the polymerization reactivity of the substrate and to improve the properties of the polymerization product, aniline or pyrrole is added to the electrolyte solution containing the substrate, and the aniline or pyrrole is polymerized by an electrolytic oxidation method to obtain polyaniline, respectively. Alternatively, a polymer in which a quinone functional group is complexed with a polypyrrole structure may be used.

Next, an aqueous solution containing an inorganic acid such as perchloric acid, hydrochloric acid or sulfuric acid, an organic acid such as methanesulfonic acid or trifluoromethanesulfonic acid, an organic solvent solution, By conducting a potential scan in the mixed solution thereof, the methoxy group during polymerization is hydrolyzed and converted into a hydroxyl group to obtain a conductive polymer having a quinone-sensitive group having redox activity. In the reaction process during this time, when 2,5-dimethoxyaniline shown in the above chemical formula (1) is used as a substrate, the formula (1) shown in the following chemical formula (2)
It is represented as

[0013]

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The basic components of the secondary battery according to the present invention include a positive electrode using the material of the present invention, a negative electrode, a non-aqueous solvent, a supporting electrolyte, a separator, a current collector, a container, and the like.

The negative electrode material is not particularly limited, but, for example, lithium metal, a lithium-containing alloy, a carbon material containing lithium, and a conductive polymer are used. The non-aqueous solvent is not particularly limited,
It is only necessary to dissolve the supporting electrolyte and be aprotic,
Examples thereof include carbonates, ethers, nitriles, esters, and sulfur-containing organic compounds.

Specifically, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, dimethoxyethane, tetrahydrofuran, acetonitrile, dioxane, sulfolane, methyl formate, ethyl acetate, methyl propionate, butyrolactone, etc. are used alone or in combination. The above may be used as an appropriate mixture.

The supporting electrolyte is not particularly limited. For example, LiClO ₄ , LiBF ₄ , LiPF ₆ ,
LiCF ₃ SO ₃ and LiN (CF ₃ SO ₂ ) ₂ can be used.

Here, the reaction mode of the battery according to the present invention is as follows.
For example, the case where poly (2,5-dihydroxyaniline) is used for the positive electrode and metallic lithium is used for the negative electrode is shown in the following formula (2) and the following formula (3), respectively.

[0019]

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[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to the following examples. (Example 1) 0.2 moldm ^-3 (hereinafter, moldm ^-3)
Is represented by M) 2,5-dimethoxyaniline and 0.2
Using a water-acetonitrile mixed solution (volume ratio = 1: 1) containing 5M HClO ₄ as a polymerization electrolyte, the potential range from 0.0 V to +0.9 V (vs. SCE) is set to 0.02 Vs ^−1.
The methoxy group in the polymer was converted to a hydroxy group by a hydrolysis reaction by repeating potential scanning at a scanning speed of 1. to obtain the desired poly (2,5-dihydroxyaniline). Next, when this material was subjected to potential scanning in a buffered aqueous solution of pH 7, a current peak pair indicating a reversible redox response was observed at about 0 V (vs. SCE), and the quinone-based functional group in the polymer was oxidized. The activity was confirmed to be reducing.

Example 2 Poly (2,5-dihydroxyaniline) obtained by the same method as in Example 1 was used in an amount of 1.0%.
When a potential scan was performed in a propylene carbonate solution containing M LiClO 4, the potential scan was about 3 V (vs. Li / Li ⁺
A current peak pair representing a reversible redox response was observed at the reference electrode), confirming that the quinone functional group in the polymer had redox activity.

Example 3 A poly (2,5-dihydroxyaniline) film obtained by the same method as in Example 1 was used as a positive electrode and metallic lithium was used as a negative electrode.
When a battery was constructed using a propylene carbonate solution containing 10 ₄ as an electrolyte, an electromotive force of about 3.3 V was obtained. When the battery was charged and discharged at a constant current of 0.05 mAcm ^-2 , a discharge capacity of 280 mAhg ^-1 per positive electrode weight was obtained.

Example 4 0.1M 2,5-dimethoxyaniline, 0.1M aniline and 0.25M HC
Water-acetonitrile mixed solution containing 10 ₄ (volume ratio 1:
Using 1) as an electrolyte for polymerization, 0.0V to + 0.9V
By repeating the potential scanning in the potential range of (to SCE) at a scanning speed of 0.02 Vs ^-1 , a polymer in which polyaniline and poly (2,5-dihydroxyaniline) were composited on a platinum electrode plate was obtained.

[0024] The obtained membrane was mixed with ion-exchanged water and 0.5 MHC.
After washing with l _4, in 0.5VHClO ₄ aqueous solution, -
The potential range from 0.2 V to +0.9 V (vs. SCE)
By repeating the scanning at a scanning speed of 0.02 Vs ^-1 , the methoxy group in the polymer was exchanged with a hydroxy group by a hydrolysis reaction to obtain a conductive polymer containing a quinone functional group.

Next, when a battery was constructed using this material as a positive electrode, metallic lithium as a negative electrode, and a propylene carbonate solution containing 1.0 M LiClO ₄ as an electrolyte, an electromotive force of about 3.3 V was obtained. Was done. Replace this battery with 0.0
When the battery was charged and discharged at a constant current of 5 mA / cm ^-2 , a discharge capacity of 250 mAg ^-1 was obtained per weight of the positive electrode.

Comparative Example 1 A polyaniline polymer was obtained on a platinum electrode substrate in the same manner as in Example 1 except that aniline was used as a polymerization reaction substrate. Next, this material was used as a positive electrode, and lithium metal was used as a negative electrode.
_When a battery was constructed using a propylene carbonate solution containing ₄ as an electrolyte, an electromotive force of about 3.3 V was obtained.
When the battery was charged and discharged at a constant current of 0.05 mA / cm ^-2 , a discharge capacity of 140 mAg ^-1 was obtained per weight of the positive electrode.

[0027]

As described above in detail, according to the present invention, it is possible to provide a cathode material having a larger capacity per unit weight than a conventional cathode material for a secondary battery. Further, since the mode of the battery reaction is different from that of a conventional polymer material such as polyaniline or polypyrrole, the energy density of the battery can be remarkably improved.

Continued on the front page (72) Inventor Bunsei Anan 2-1-147 Shiobara, Minami-ku, Fukuoka City, Fukuoka Prefecture Inside Kyushu Electric Power Co., Inc. (72) Inventor Kazuyuki Adachi 2-1-1 Shiobara, Minami-ku, Fukuoka City, Fukuoka Prefecture No. 47 Inside Kyushu Electric Power Co., Ltd.

Claims (2)

[Claims] 1. A cathode material for a secondary battery, comprising a conductive polymer having a structure having a quinone-based functional group having redox activity. 2. A positive electrode material for a secondary battery, comprising a conductive polymer containing a unit having a quinone functional group having redox activity in its repeating structure.