JP2000248054A - Functional polymer, its production, electrode material and electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a functional polymer utilizable for a light battery having high energy density, an electrochromic element having a large area, a biochemical sensor using a micro electrode, or the like by polymerizing a specific aromatic compound or a heterocyclic compound. SOLUTION: This functional polymer is obtained by polymerizing an aromatic compound or heterocyclic compound having two or more thioamide groups. The functional polymer can be produced by subjecting an aromatic compound or a heterocyclic compound having two or more of the thioamide groups to oxidation in an acidic medium to polymerize the compound. The aromatic compound having two or more thioamide groups is preferably dithiobenzamide (derivative) or the like. The functional polymer having the structure of the formula (X- is an anion; n is >=2; the benzene ring may have a substituent group) is obtained by polymerizing the dithiobenzamide (derivative).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a functional polymer in which an oxidation-reduction reaction is reversibly performed, a method for producing the same, and an electrode using the functional polymer. In this case, a characteristic feature is that a lightweight and high energy density battery can be obtained.

[0002]

2. Description of the Related Art In recent years, as a new type of battery having a high output and a high energy density, a lithium secondary battery of high electromotive force utilizing oxidation and reduction of lithium has been used.

Here, in such a lithium secondary battery, metal oxides such as manganese, cobalt, nickel, iron, vanadium and niobium have been generally used as a positive electrode material for the positive electrode.

However, when such a metal oxide is used for the positive electrode, its weight increases and its cost increases, and the number of reactive electrons is small, so that the capacity per unit weight is not necessarily sufficient. However, it was difficult to obtain a lightweight and high energy density lithium secondary battery.

On the other hand, recently, a conductive polymer has been used as an electrode material, and has been used for a light-weight, high-energy-density battery, a large-area electrochromic element, and a biochemical sensor using microelectrodes. Is being considered.

[0006] As such a conductive polymer,
In the past, polyaniline, polypyrrole, polyacene, polythiophene, and the like have been studied, and their use as a conductive polymer battery electrode has been studied. In recent years, high capacity and high energy density have been obtained. As a polymer, an organic sulfur compound is proposed in EP 415856.

Here, the above-mentioned organic sulfur compound performs charge and discharge by utilizing a redox reaction of sulfur. Such an organic sulfur compound is used as a positive electrode material of a positive electrode, and has a high energy density. Obtaining a lithium secondary battery is being studied.

However, in the case of the above-mentioned organic sulfur compounds, the oxidation-reduction reaction is slow, the charge / discharge current is small, and
There are problems such as being limited to use at a high temperature of 00 ° C. or higher.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a novel functional polymer which can be suitably used for a light-weight, high-energy-density battery, a large-area electrochromic device, a biochemical sensor using microelectrodes, and the like. The oxidation-reduction reaction of the novel functional polymer is appropriately performed even at a low temperature, and when the functional polymer is used for an electrode of a battery, the temperature is low. ,
For example, it is an object of the present invention to provide an appropriate charge / discharge reaction even at room temperature to enable charge / discharge with a large current and to obtain a battery with high capacity and high energy density.

[0010]

In order to solve the above-mentioned problems, the present invention has developed a functional polymer obtained by polymerizing an aromatic compound or a heterocyclic compound having two or more thioamide groups. It was done.

As the aromatic compound having two or more thioamide groups as described above, for example, dithiobenzamide and a derivative thereof described in claim 2 can be used.

[0012] Further, by polymerizing the dithiobenzamide and the derivative thereof according to the second aspect, the third aspect is achieved.
A functional polymer having the structure shown in the above-mentioned chemical formula 1 is obtained. Here, the anion in the chemical formula 1 X ^- is an inorganic ion or an organic ion such as perchlorate ion, and as the substituent bonded to the benzene ring, a lower alkyl group, an amino group, a halogen group, hydroxyl group, sulfonic And the like.

In producing a functional polymer obtained by polymerizing an aromatic compound or a heterocyclic compound having two or more thioamide groups, an aromatic compound or a heterocyclic compound having two or more thioamide groups is used. It can be produced by oxidizing and polymerizing in an acidic medium.

Here, in oxidizing and polymerizing an aromatic compound or a heterocyclic compound having two or more thioamide groups in an acidic medium, for example, using hydrogen peroxide or perchloric acid as an oxidizing agent, In addition to oxidation in an acidic solution such as formic acid, oxidation can also be performed in an acidic solution by an electrochemical oxidation reaction.

The aromatic or heterocyclic compound H ₂ NSC having two or more thioamide groups as described above.
-R-CSNH ₂ (Note, R is an aromatic compound or a heterocyclic compound.) When is oxidized in an acidic medium, as shown in the reaction scheme of 3 below, aromatic compound or heterocyclic The thioamide group in the compound —CSNH ₂ sulfur bonds to each other, and then the amino group is condensed to form NH ₃
Is released to form a 5-membered ring having an SS bond.

[0016]

Embedded image

The functional polymer obtained in this manner is characterized in that the five-membered ring having the above-mentioned SS bond has a π-electron cloud, and the aromatic polymer has a π-electron cloud on both sides of the five-membered ring. When a group compound or a heterocyclic compound is bonded, the transfer of electrons is performed smoothly in this functional polymer, and when this functional polymer is used for an electrode of a battery,
Charge and discharge with a large current becomes possible.

In the above functional polymer, it is considered that a three-electron oxidation-reduction reaction as shown in the following chemical formula (4) is reversibly performed, and when this functional polymer is used for an electrode of a battery, Thus, a battery having a high capacity and a high energy density can be obtained. In the following chemical formula 3, X ⁻ is an anion, and Y ⁺ is a cation such as a metal ion.

[0019]

Embedded image

Further, in the present invention, an electrode material having the structure shown in Chemical Formula 2 has been developed as an electrode material used for the electrode.

Here, the electrode material shown in Chemical formula 2 also has a 5-membered ring having an SS bond having a π electron cloud and a π electron cloud on both sides of the 5-membered ring, similarly to the above-mentioned functional polymer. It is considered that an aromatic compound having a π-electron cloud is bonded, whereby electrons can be smoothly transferred and a three-electron oxidation-reduction reaction is reversibly performed.

In the electrode according to the present invention,
As the electrode material, the above-mentioned functional polymer or the electrode material shown in Chemical formula 2 was used.

Here, the above-mentioned functional polymer or the above-mentioned compound 2
When manufacturing electrodes using the electrode materials shown in
If necessary, a conductive material, an ion conductive material, a binder, and the like are added to these materials.

As the conductive material, metal powder, carbon material, conductive polymer and the like can be used.
Nickel, stainless steel, etc. are used as the metal powder, acetylene black, vapor grown carbon, graphite, etc. are used as the carbon material, and polyaniline, polypyrrole, polyparaphenylene, polyacetylene, and the like are used as the conductive polymer. And the like.

As the ion conductive material, an inorganic ion solid electrolyte or an organic ion solid electrolyte is used. As the organic ion solid electrolyte, for example, polyethylene oxide (PEO), polyacrylonitrile (PAN) and derivatives thereof are used. Polymer containing salt,
For example, a gel polymer impregnated with an electrolyte solution can be used.

As the binder, for example, a polymer such as polyvinylidene fluoride (PVDF) which is usually used for producing an electrode can be used.

Further, when producing an electrode using the above functional polymer, other organic sulfur compounds such as 2,5-dimercapto-1,3-thiadiazole and sulfur may be mixed, if necessary. Further, in order to increase the specific surface area of the electrode or to improve the film forming property, it is possible to mix fibrous or particulate solids such as zeolite and whisker.

As a method for producing an electrode using the above functional polymer, a known method can be used. For example, a conductive material or the like is added to the above functional polymer and mixed in a mortar. Applying the mixture to a current collector etc. to form
A method of compacting with a press machine and molding can be used.

The electrode prepared using the above functional polymer can be used as a positive electrode of a lithium secondary battery.

Here, when an electrode prepared using the above-mentioned functional polymer is used as a positive electrode of a lithium secondary battery, a known negative electrode and an electrolyte of the lithium secondary battery are conventionally used. Can be used. As the negative electrode, for example, lithium metal, a lithium alloy, a material made of a carbon material or an inorganic material capable of inserting and extracting lithium can be used, and as the electrolyte, for example, ethylene carbonate or the like can be used. A liquid in which a lithium compound such as LiClO ₄ is dissolved as an electrolyte salt in an organic solvent, a solid electrolyte using an inorganic material, a solid electrolyte using a polymer, or the like can be used. It is also possible to use a gelled polymer electrolyte.

[0031]

EXAMPLES Hereinafter, the functional polymer according to the examples of the present invention and the method for producing the same will be specifically described, and excellent effects will be obtained when the functional polymers according to the examples are used for battery electrodes. Clarify what you can get. In addition, the functional polymer in this invention and its manufacturing method are not limited to those shown in the following examples, and can be carried out by appropriately changing the scope without changing the gist thereof. The application is not limited to the battery electrode.

As an example of the present invention, a case where a functional polymer having the structure shown in the following Chemical Formula 5 is produced will be described.

[0033]

Embedded image

Here, in producing the functional polymer having the structure shown in Chemical Formula 5, 1,4-dithiobenzamide shown in Chemical Formula 6 produced as follows is used as a reaction initiating monomer. .

[0035]

Embedded image

Here, in producing 1,4-dithiobenzamide, 750 mg of terephthalonitrile was dissolved in 20 ml of ethanol to which several drops of triethylamine had been added. Next, the solution was reacted at 50 ° C. for 6 hours while blowing hydrogen sulfide into the solution. Yellow crystals precipitated by the reaction were collected, washed with ethanol, and then recrystallized with a dimethylform-amide ether solution. 870 mg of 1,4-dithiobenzamide was obtained.

In polymerizing the above 1,4-dithiobenzamide, a thermometer was installed.
7.5 ml of 95% formic acid and 7 ml
A mixed solution was prepared by adding 7.5 ml of 0% perchloric acid, and 1.8 g of the above 1,4-dithiobenzamide was added to the three-necked flask, and the mixture was stirred in the mixed solution. Then, 0.75 ml of 30% aqueous hydrogen peroxide was added dropwise over 10 minutes, and stirring was continued for another 15 minutes. Then, the mixture was heated to 70 ° C. with further stirring to react for 24 hours. Thereafter, suction filtration was performed to obtain a purple solid. Then, the solid is washed with water, ethanol, and acetone in this order to remove the reaction solution and low-molecular compounds remaining on the solid, and then dried under vacuum to obtain the function of the structure shown in Chemical Formula 4. 0.4
g was obtained. In addition, it is considered that the above-mentioned reaction in which 1,4-dithiobenzamide is polymerized is carried out according to a reaction formula shown in the following Chemical Formula 7.

[0038]

Embedded image

Here, the functional polymer obtained as described above and 3,5-diphenyl-1,2,4-dithiazolium shown in the following Chemical Formula 8, which is a model monomer of the functional polymer, are used. The infrared absorption spectra with perchlorate were compared.

[0040]

Embedded image

As a result, the infrared absorption spectrum of the above functional polymer has an infrared absorption spectrum characteristic derived from 3,5-diphenyl-1,2,4-dithiazolium perchlorate. It is considered that this functional polymer has the structure shown in Chemical Formula 4 above.

When the cyclic voltammograms of the above functional polymer and 3,5-diphenyl-1,2,4-dithiazolium perchlorate were compared, it was found that the above functional polymer was 3,5 It is considered that, similar to -diphenyl-1,2,4-dithiazolium perchlorate, it shows a reversible three-electron redox reaction as shown in the following chemical formula 9, and the above-mentioned functional polymer has a reaction peak. The distance between is 3,
It is shorter than 5-diphenyl-1,2,4-dithiazolium perchlorate, and it is considered that the electron transfer speed was accelerated by polymerization as described above.

[0043]

Embedded image

Next, when an electrode is produced using the above functional polymer and this electrode is used as a positive electrode of a lithium secondary battery, a large battery capacity can be obtained even when charging and discharging with a large current. To reveal.

Here, in preparing an electrode using the above functional polymer, 0.4 g of the above functional polymer powder was sufficiently pulverized in a mortar, and then 0.4 g of acetylene black was added thereto. The mixture was added several times, pulverized and mixed, further added with 0.1 g of polyvinylidene fluoride (PVDF), mixed well, and then mixed with 50 ml of dimethylformamide (DMF) and kneaded. Was printed on a titanium foil having a size of 30 μm and a size of 10 cm × 10 cm, which was then subjected to a vacuum heat treatment at 80 ° C. for 3 hours, and then cut into a size of 1 cm × 1 cm to prepare an electrode for evaluation. .

Next, this evaluation electrode was used as a positive electrode, metallic lithium was used for each of a negative electrode and a reference electrode, and propylene carbonate was used as an electrolyte solution and LICLO was used as an electrolyte solution.
Using a solution in which ₄ was dissolved at a ratio of 1 mol / l, a three-electrode test battery was produced. All of the test batteries were manufactured in a glove box with an argon gas flow.

Using the test battery, charging and discharging were performed repeatedly at a constant current of 0.1 mA at a discharge end voltage of 1.75 V and a charge end voltage of 3.75 V.

Then, the discharge characteristics of the functional polymer at the time of the first discharge were examined, and the results are shown in FIG. 1. In addition, the change in the discharge capacity with the number of discharges was examined. ClO ₄ in ^- such as asking the change in discharge capacity per polymer substrate 1g excluding anions, and the results are shown in Table 1 below. The theoretical capacity per unit weight when the above-mentioned polymer substrate shows a three-electron redox reaction is 452 mAh.

[0049]

[Table 1]

As is apparent from the results, charging and discharging can be performed using the electrode using the above-mentioned functional polymer as the positive electrode of the lithium secondary battery. In particular, at the time of the first discharging, The discharge capacity of the above-mentioned functional polymer per 1 g of the polymer substrate was as large as 422 mAh / g, which was a value close to the above theoretical capacity. It is thought to show a redox reaction.

In the above embodiment, the electrode using the functional polymer having the structure shown in Chemical Formula 4 has been described.
It is considered that an electrode using 1,2,4-dithiazolium perchlorate also exhibits the same three-electron oxidation-reduction reaction as in the case of the above-mentioned functional polymer, and a large discharge capacity can be obtained.

[0052]

As described in detail above, the functional polymer of the present invention is obtained by polymerizing an aromatic compound or a heterocyclic compound having two or more thioamide groups. As shown in the above chemical formula 1, a 5-membered ring having a π-electron cloud having an SS bond is formed, and an aromatic compound or a heterocyclic compound having a π-electron cloud on both sides of the 5-membered ring. Are considered to be bonded to each other, so that electrons can be smoothly transferred, and in this functional polymer, a three-electron oxidation-reduction reaction is considered to be performed.

It is also considered that the electrode material having the structure shown in the above chemical formula 2 can smoothly transfer electrons and perform a three-electron oxidation-reduction reaction similarly to the above-mentioned functional polymer. .

When the above-mentioned functional polymer or electrode material is used for an electrode of a battery, charging / discharging with a large current becomes possible, and a battery with high capacity and high energy density is obtained. It became so.

The functional polymer and the electrode material of the present invention are used not only for electrodes of a battery, but also for sensors such as an electrochromic element having a fast coloring / fading speed, a glucose sensor having a fast response speed, and a writing / reading speed. It can also be used for fast analog electrochemical memories.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first discharge characteristic of a test battery manufactured in an example of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) // G02F 1/155 G02F 1/155 (72) Inventor Hiroshi Uemachi 1-8 Asahidai, Tatsunokuchi-cho, Nomi-gun, Ishikawa Pref. 1-310 Dormitory at Hokuriku University (72) Inventor Yoshihiro Iwasa 1-50-A52, Asahidai, Tatsunokuchi-cho, Nomi-gun, Ishikawa Prefecture (72) Inventor Tadaoki Mitani 1-50-A34 Asahidai, Tatsunokuchi-cho, Nomi-gun, Ishikawa F-term (reference) 2K001 CA15 4J032 BA02 BA12 BA20 BB01 BC01 BD01 BD02 BD07 CG01 5H003 AA02 BA07 BB03 BD00 5H014 AA01 EE01 EE03 HH00 5H029 AK15 AL06 AL12 AM03 AM07 CJ14 HJ02

Claims (6)

[Claims] 1. A functional polymer obtained by polymerizing an aromatic compound or a heterocyclic compound having two or more thioamide groups. 2. A functional polymer obtained by polymerizing dithiobenzamide and a derivative thereof. 3. A functional polymer having a structure represented by the following chemical formula 1. Embedded image In the formula 1, X ⁻ is an anion, n is an integer of 2 or more, and a substituent may be bonded to the benzene ring. 4. A method for producing a functional polymer, comprising oxidizing and polymerizing an aromatic compound or a heterocyclic compound having two or more thioamide groups in an acidic medium. 5. An electrode material having a structure represented by the following chemical formula 2. Embedded image In the formula 2, X ⁻ is an anion, and a substituent may be bonded to the benzene ring. 6. An electrode comprising the functional polymer according to any one of claims 1 to 3 or the electrode material according to claim 5.