JPH05290852A - Polymer secondary battery - Google Patents

Abstract

PURPOSE:To enable charge/discharge at a high current density, and provide a high charge/discharge capacity. CONSTITUTION:A three-electrode battery is composed of a positive electrode of a polypyrrole moulded body manufactured in an electrolytic oxidation polymerization method, a negative electrode of platinum, a reference electrode of lithium matel, and electrolyte of LiClO4. When a discharge at a current density of 10mA/cm<2>, and a constant potential charge at 36V are performed, when charging is completed, distribution of anion density in the thickness direction of the moulded body expressed by an expression of {(Imax-Imin)/Iman}X100(%) (where Imax refers to the maximum value of the anion density in the thickness direction of the moulded body, with Imin referring to the minimum value of the anoin density in the thickness direction of the moulded body) is 50% or less. When discharge is completed, the anion density in the moulded body is 30% or less of that when charging is completed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polymer secondary battery using an improved polypyrrole molded product as a positive electrode active material.

[0002]

2. Description of the Related Art In general, conductive polymers are known to have a property of being electrochemically oxidized and reduced in addition to exhibiting high conductivity. It is known that the counterions contained in the conductive polymer move in and out with the oxidation / reduction reaction of the conductive polymer. An electrode using polypyrrole, polythiophene, polyaniline or the like has been proposed by utilizing this function as an electrode.

However, when the conventionally proposed conductive polymer is used as these electrodes, there are problems that the degree of charge / discharge at a high current density is small and a high charge / discharge capacity cannot be obtained. ing. For example, when the discharge current density is high with respect to a high-capacity type battery electrode in which the active material is thick, the discharge capacity per unit weight is low, and it is difficult to obtain a high output, and the time required for charging also becomes long. .. This is because the counter ions in the conductive polymer do not move in and out smoothly.

For the purpose of solving these problems, Japanese Patent Laid-Open No.
JP-A-3-48749 discloses an electrode obtained by polymerization by applying a full-wave rectified voltage, and JP-A-63-48750 discloses an electrode obtained by polymerization by applying an asymmetric voltage. In these proposals, the properties of each part of the conductive polymer produced by conventional constant current and potentiostatic polymerization lack uniformity, and when this is used for the battery electrode, the battery reaction is concentrated on a part of the electrode. As a result, the charging voltage is likely to rise early and the charge / discharge capacity of the battery is lowered, whereas the conductive polymer polymerized using these methods eliminates such a defect. There is.

However, even this method is effective in the case of a thin film, but is not effective in the case of a thick film. That is, since charge / discharge accompanies the inflow / outflow of counterions, charge / discharge in the vicinity of the film surface proceeds smoothly, but the diffusion of counterions does not proceed smoothly inside the film. It's hard to say that it has been improved. Generally, in a secondary battery, in order to obtain a high charge / discharge capacity in a small area, a thick molded film having a thickness of 100 μm or more, and in some cases, a thickness of 1 mm is used. Therefore, it is difficult to obtain a sufficient charge / discharge capacity in a secondary battery using such a film thickness of the molded body even with the improved electrode as described above. In particular, when discharging at a high current density, there is a marked tendency that it is difficult to obtain a high charge / discharge capacity.

On the other hand, Japanese Patent Laid-Open No. 62-2468 proposes to prepare a conductive polymer film containing ions having a large ionic radius in advance and use the ions having a small ionic radius as an electrolyte when incorporating the film into a battery. .. This method has been proposed for the purpose of smoothing the entrance and exit of the ions by reducing the size of the counter ions, and as a result, smoothing the charge and discharge.

However, even in this case, in the case of a coarse film having a fibrillar shape and a high porosity such as polyacetylene disclosed in the specification, the electrolyte easily diffuses and permeates into the inside, but it is effective to some extent. , A dense film such as polypyrrole cannot obtain a sufficient effect. As disclosed in the examples of the specification, at a low doping level of 10 mol% per pyrrole ring, even if a Coulomb efficiency of 100% of charge / discharge is obtained, about 30 mol% per pyrrole ring, which is the theoretical doping level of polypyrrole. It is difficult to charge and discharge the high doping level.
That is, even if charging / discharging corresponding to a doping amount of 30 mol% occurs on the film surface, charging / discharging hardly occurs inside and only charging / discharging corresponding to a doping level of about 10 mol% occurs on average. .. This tendency becomes more remarkable as the thickness of the formed film becomes thicker. In other words, the higher the thickness, the lower the charge / discharge capacity per unit weight of the polymer molded film. A further improvement is the invention described in Japanese Patent Application Laid-Open No. 2-119051. In this publication, it is proposed to improve the discharge capacity of polypyrrole synthesized by using ions larger in size than those used in the above-mentioned Japanese Patent Laid-Open No. 62-2468 during the polymerization of pyrrole. However, even with this, the discharge capacity at high discharge current density in the thick molded film is still much lower than the value calculated from the theoretical value of the doped polymer.

[0008]

SUMMARY OF THE INVENTION In view of the drawbacks of the secondary battery, the present invention provides a polymer secondary battery using a polypyrrole molded article which enables charging / discharging at a high current density and can obtain a high charging / discharging capacity. The purpose is to provide the next battery.

As a result of diligent study on a method for smooth charge / discharge even in the case of using a dense and thick molded body such as polypyrrole, as a result, counter ions come in and go out due to charge / discharge,
That is, in order to smoothly promote the diffusion of anions in the molded body, it is not enough to simply use polypyrrole to evenly move the counterions, and also to exchange large counterions with small counterions. It turns out that just doing is not enough. Then, by repeating electrolytic polymerization of polypyrrole containing a large counterion in advance, in other words, performing synthesis while putting in and out the counterion, and then replacing it with a small ion by an electrochemical or chemical method, these problems occur. The inventors have found that they can be solved and completed the present invention.

[0010]

The present invention relates to a polymer secondary battery using a polypyrrole molded product produced by electrolytic oxidation polymerization as a positive electrode active material for a battery, wherein the polypyrrole molded product has the polypyrrole molded product as a positive electrode. , Platinum as a negative electrode, and lithium metal as a reference electrode, LiCl
A three-electrode battery was constructed using O ₄ as an electrolyte and a current density of 10
At the time of discharging at mA / cm ² and constant potential charging at 3.6V, the anion concentration in the molded body is 30% or less of that at the time of completion of discharging, and is defined by the following formula at the time of completion of charging. The distribution of the anion concentration in the thickness direction of the molded product is 5
It is a polymer secondary battery characterized by being 0% or less.

[0011]

## EQU2 ## {(Imax-Imin) / Imax} × 100 (%) (1) (where Imax is the maximum anion concentration in the thickness direction of the molded body, and Imin is the thickness direction of the molded body. Is the minimum anion concentration.)

The thickness of the polypyrrole molded body of the positive electrode active material for the polymer secondary battery of the present invention is 50 μm or more and 2,000.
It is 0 μm or less. When the thickness is less than 50 μm, the volume is small and a high charge / discharge capacity cannot be obtained. 2,000 thickness
If it is more than μm, the diffusion of the counter ions inside the molded body does not proceed smoothly, so that it becomes difficult to charge and discharge at a high current density.
The preferred thickness of the polypyrrole molded product for polymer secondary battery is 100 to 2,000 μm.

A three-electrode battery is a battery composed of three electrodes, a positive electrode, a negative electrode and a reference electrode. A current flows from the positive electrode to the negative electrode due to the reduction of the oxidized polypyrrole molded product during discharge. On the contrary, at the time of charging, a current flows into the polypyrrole molded product in the reduced state, so that the polypyrrole molded product is oxidized. By placing the reference electrode during charging, it is possible to keep the positive electrode potential constant at the unique potential (oxidation potential) required for the oxidation of the polypyrrole molded body, resulting in an unnecessarily high potential (overvoltage). It is possible to prevent

In this three-electrode battery, the polypyrrole molding of the present invention used for the positive electrode has a current density of 10 mA.
When discharged at / cm ^2, at the time of discharge completion anion concentration in the polypyrrole shaped body than 30% of the fully charged, preferably 25% or less. That is, at the time of discharge, the polypyrrole molded product is reduced, so that it changes from a cationic type to a neutral type. Along with this, the anion (counterion) ClO ₄ ⁻ that offsets the cation is released from the polypyrrole molded article into the electrolytic solution. When the constant potential charging is performed at 3.6 V, the distribution of the anion concentration in the thickness direction of the molded body defined by the formula (1) is 50% or less, preferably 30% or less when the charging is completed. That is, at the time of charging, the polypyrrole molded body is oxidized, so that the neutral type is changed to the cationic type. Along with this, ClO ₄ ⁻ existing in the electrolytic solution diffuses into the molded body. Therefore, in order for charging to proceed smoothly, ClO ₄ ⁻ needs to diffuse smoothly into the inside of the molded body. As a result, the chlorine element concentration distribution in the compact becomes flat. When the polypyrrole molded article of the present invention constitutes a three-electrode battery and is subjected to the constant potential charging,
The distribution of the anion concentration in the thickness direction is flat at 50% or less. If the diffusion does not proceed smoothly, only the surface of the molded product is charged, and as a result, only the halogen concentration near the surface becomes high and its distribution does not become flat.

The anion concentration during charging and discharging can be measured by analyzing the chlorine element contained in the anions with an X-ray microanalyzer.

Thus, in the present invention, the concentration distribution of anions in the thickness direction of the polypyrrole molded product has a value (%) defined by the equation (1) of 50% as described above.
It is below.

The concentration of chlorine contained in the anions in the thickness direction of the polypyrrole molded product by X-ray microanalyzer is shown as a distribution chart as shown in FIGS. 2, (FIG. 4), FIG. 6, FIG. 7 and FIG. .. FIG. 4 is a comparative example, and is a distribution diagram of chlorine in the polypyrrole molded article which belongs to the present invention other than the above.

The distribution chart of chlorine in the thickness direction obtained by these X-ray microanalyzers shows that both surfaces (right and left in the drawing) of the film of the polypyrrole molded product are not shown in the drawing due to problems in measurement of electron beam irradiation. The chlorine concentration is zero or extremely small. However, it is estimated that the concentration of chlorine in the vicinity of both surfaces of the film is actually the same as the concentration of chlorine at a depth of about 20 to 30 μm. Therefore, in the present invention, the concentration distribution of the anion containing chlorine in the thickness direction of the polypyrrole molded product is obtained based on the above formula (1) by reading Imax and Imin by an X-ray microanalyzer. At that time, the chlorine concentration in the vicinity of both surfaces of the film in the distribution chart is not read based on the above reason.

In the present invention, in reality, in the distribution chart,
The film thickness is set to 1 according to the film thickness direction of the polypyrrole molded product.
The concentration distribution of anions is calculated from the values of Imax and Imin obtained by reading the chlorine concentration between about 30% and about 70% from the surface when it is set to 00%. Suitably, most often a chlorine concentration of between about 20% and about 80% may be read from the surface. In the polypyrrole molded product of the present invention, the concentration distribution of the above anions is 50% or less when charging is completed, and as shown in the drawing, it is substantially flat and distributed at a high concentration in the thickness direction.

In order to obtain a polypyrrole molded article for a polymer secondary battery of the present invention, a solution in which pyrrole, an anion having a molecular weight of 150 or more and a large ionic size anion and a supporting salt composed of a counter cation thereof are uniformly dissolved The electrode substrate is immersed in it, and electropolymerization is performed to form a thin film. Then, undoping treatment is performed at a reduction potential or lower, and the thin film is produced by electropolymerization and the undoping treatment is repeated at least twice or more. Do it.
At this time, the thickness of the thin film obtained by carrying out the electrolytic polymerization is 0.1 to 50 μm. As a result, a polymer molded body having a thickness suitable for use in an electrode of a polymer secondary battery doped with anions in which the ions of the supporting salt easily escape from polypyrrole and anions that do not easily escape is formed. Thereafter, if necessary, an anion (counterion) having an ion size sufficiently smaller than that of the anion of the supporting salt is introduced into and exchanged with the molded body, whereby the polypyrrole molded body of the present invention is finally obtained.

The polypyrrole constituting the molded polypyrrole of the present invention is a conjugated conductive polymer composed of a hetero five-membered ring unsubstituted or substituted pyrrole. Examples of those having a substituent include those in which the 3-position and / or the 4-position are substituted with an alkyl group, an alkoxy group, a carboxy group, a carboxymethyl group or the like. Further, an azulene, an alkyl, a phenylene substitution product, or a terthiophene compound may be used as a copolymerization component of pyrrole. Further, carbon particles, metal oxides such as manganese dioxide and the like can also be polymerized in the presence of suspension.

Next, polypyrrole is electrolytically polymerized by immersing the electrode substrate for polymerization in a solution in which a supporting salt containing an anion having a large ionic size and anion having a large ionic size and pyrrole are uniformly dissolved. Obtained.
Anions having a large ion size are taken into the molded body as counterions during the production of the polypyrrole molded body,
It is removed by the undoping process.

The ionic size of the anion of the supporting salt used for electrolytic polymerization is preferably 8 angstroms or more.
Here, the ionic size of the anion is the length in the major axis direction of the molecule including the ionized atom.

The anion of the supporting salt must have a molecular weight of 150 or more, preferably 170.
As described above, it is necessary that the molecular weight is 200 or more. If the molecular weight of the anion is less than 150, the ion size is not sufficiently large, and the diffusion rate of the anion in the polypyrrole molded article is not sufficiently large.

These supporting salts having a large ionic size
For Nion, C_nF_{2n + 1}SO₃ ^-(N = 4 to 12)
A perfluoroalkanesulfonate ion represented by
General formula C_nH_{2n + 1}SO₃ ^-(N = 4 to 12)
Rucan sulfonate ion, general formula C_nF_{2n + 1}OSO₃ ^-
Perfluoroalkyl sulfuric acid represented by (n = 4 to 12)
Ester ion, general formula C_nH_{2n + 1}OSO₃ ^-(N = 4
~ 12) alkylsulfate ion, absent
Substituted and substituted benzenesulfonic acid, naphthalene sulfone
Each ion of sulfonic acids such as acid can be used. Well
Further, as the carboxylic acid, unsubstituted and substituted benzoic acids are
Can be mentioned. Of these, more preferred is ion
Based on isose and its shape, benzenesulfonic acid,
Acid, p-tert-butylbenzene sulfone
Acid, 2,4,6-triisopropylbenzene sulfone
Acid, octylbenzenesulfonic acid, dodecylbenzene
Alkylbenzenesulfonic acid such as rufonic acid, methoxy
Benzenesulfonic acid, 5-sulfoisophthalic acid, 5-su
Rufoisophthalic acid dimethyl ester, 5-sulfoisophthalate
Talic acid dihydroxyethyl ester, naphthalene sulfo
Each ion such as acid is mentioned.

The supporting salt containing these as components is
Salts of tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion and other tetraalkylammonium ions, which are counter cations of these anions, and salts of alkali metal ions such as Li, Na and K, Can be mentioned.

In the production of the polypyrrole molding of the present invention, the thickness of the molding is 0.1 to 50 μm, preferably 0.3.
A thin polypyrrole film having a thickness of -30 μm is formed, and thereafter, undoping treatment is performed at a reduction potential or lower. When a thick molded body with a thickness of 50 μm or more is formed from the beginning, charging / discharging near the surface of the molded body proceeds smoothly, but counter ions do not diffuse smoothly inside the molded body. Therefore, a thin film is synthesized and undoped. By repeating this operation at least twice or more, a film having a thickness that can be used for an electrode is synthesized.

The electrolytic polymerization of the present invention is carried out in a solvent, and as the solvent, there are used solvents generally used in electrochemical reactions such as acetonitrile, benzonitrile, water, propylene carbonate, ethylene carbonate, nitrobenzene,
Tetrahydrofuran, nitromethane, sulfolane, dimethoxyethane, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and the like and mixed solvents thereof are used.

The electrode used in the electrolytic polymerization is not particularly limited, but metals such as platinum, palladium, gold, copper, nickel, stainless steel, etc. used in the electrochemical reaction, or a conductive material similar to these or carbon. The material such as an electrode is used.

In the present invention, electrolytic polymerization is performed, for example, by "conductive polymer material" (supervised by Hiroyuki Sparrow, CMC, Showa 5).
(Published in 1988), "New conductive polymer materials" (Supervised by Hiroyuki Sparrow, CMC, published in 1987), "Handbook of
Conducting Polymers "(TASkotheim (ed.), Marcel
Dekker, New York, 1986).

In the electropolymerization in the present invention, a symmetrical voltage in which the potential difference between both electrodes, that is, the voltage value alternately and repeatedly changes between positive and negative with time and the period of the positive voltage value is large is applied. It can be performed by an electrolytic polymerization method. It is also possible to apply an asymmetric voltage. In this case, the current during electrolysis repeats the cycle of zero → positive → zero → negative → zero, and zero → positive →
Electropolymerization occurs in the zero period. In this period, the electrolytic polymerization proceeds and the doping of the undoped polypyrrole polymer proceeds in the preceding period. Therefore,
When the positive voltage period is long, both polymerization and doping reactions can sufficiently proceed during this period. In the period of zero → negative → zero, the above-mentioned polymerization does not occur, and undoping occurs.
By the above operation, the anion of the supporting salt described above repeats undoping and doping, and an ion diffusion path is formed in the molded polypyrrole.

The potential applied during the electropolymerization is carried out between the oxidation-reduction potential of the monomer and the upper limit, and below the reduction potential of the polymer and the lower limit. As the upper limit of the applied potential, a potential higher than the polymerization oxidation potential is preferably used within a range in which side reactions such as a monomer, a solvent and a supporting salt do not occur simultaneously. The lower limit of the applied potential is preferably a potential lower than the reduction potential of the polymer. The upper limit potential applied during electrolysis is
0.7 to 1.5 V (vs Ag / AgCl), preferably 0.8 to 1.2 V is used, and the lower limit potential is -1.5 to-.
0.3V, preferably -1.0 to -0.4V is used. If the potential applied to the anode is raised or lowered between a potential higher than the oxidation potential of the polymer and a potential lower than the reduction potential, ions will enter and exit, and polymerization will occur if the potential exceeds the lower limit of the oxidation potential of the monomer. .. Therefore, the potential and the holding time thereof may be set in consideration of the balance between polymer generation and ion entry / exit. Hereinafter, the operation of changing the potential applied to the anode between the upper limit potential and the lower limit potential with time is referred to as raising and lowering the potential.

The waveform of the potential applied to the anode is not particularly limited, but generally a rectangular wave, a triangular wave, a sine wave or a waveform in which they are superimposed is used.

The electropolymerization in the present invention is an electrolysis in which a current flowing between both electrodes is alternately changed over time between positive and negative and a positive current is supplied for a long period. The polymerization method can be used. It is also possible to apply an asymmetric voltage. In this case, the current during electrolysis repeats the cycle of zero → positive → zero → negative → zero, and electrolytic polymerization occurs during the period of passing the positive current. During this period, the electropolymerization proceeds and the doping of the undoped polypyrrole polymer proceeds during the preceding negative current period. Therefore, if the positive current period is made large, both reactions of polymerization and doping can sufficiently proceed during this period. In the period of zero → negative → zero, the above-mentioned polymerization does not occur, and undoping occurs. By the above operation, the anion of the supporting salt described above repeats undoping and doping, and an ion diffusion path is formed in the molded polypyrrole.

The positive current at the electrolytic ^{polymerization, 0.01mA / cm 2 ~100mA / cm} 2 as a current density at the anode, preferably ^{0.05mA / cm 2 ~50mA / cm 2} . If the current density of the positive current is too large, the anode potential may rise too much, and side reactions such as monomers, solvents, supporting salts, etc. may occur simultaneously. If the current density is too low, the time required for the polymerization will be long and the productivity will be extremely reduced. The negative current during electrolytic polymerization was 0.01 mA as the current density at the anode.
/ Cm ^{2 to} 100 mA / cm ² , preferably 0.05 mA /
cm ^{2 to} 50 mA / cm ² . If the current density of the negative current is too high, undoping of anions will be insufficient. Further, if the current density of the negative current is too small, the time required for undoping becomes long, resulting in extremely low productivity. Therefore, as in the case of raising and lowering the potential, the potential and the holding time thereof may be set in consideration of the balance between polymer production and ion ingress and egress. The waveform of the current flowing between the electrodes is not particularly limited, but generally, a rectangular wave, a triangular wave, a sine wave, or a waveform in which they are superimposed is used.

The polymerization temperature is -50 to + 50 ° C, preferably -40 to + 40 ° C. If the temperature is lower than that, the viscosity of the system increases and the voltage between the electrodes rises too much to easily cause a side reaction, which is not preferable.

The thickness of the film formed per cycle of the repeating cycle of electrolytic polymerization and undoping treatment is 0.1 to 50 μm, more preferably 0.3 to 30 μm.
m, particularly preferably 0.5 to 15 μm.

By repeatedly performing such electrolytic polymerization and undoping treatment, a polymer molding having a thickness suitable for use in an electrode of a polymer secondary battery in which anions of the supporting salt are unevenly doped in polypyrrole Can form a body.

By repeating the electrolytic polymerization and the undoping treatment, it is possible to obtain a polypyrrole molded product in which counter ions can easily diffuse into the active material of the secondary battery.

The repetition period of electrolytic polymerization and undoping treatment is preferably 10 to 10,000 seconds / cycle. If the repeating period of electrolytic polymerization and undoping treatment is less than 10 seconds / cycle, the anion exchange reaction cannot catch up and sufficient counterions do not come and go. On the other hand, if this cycle exceeds 10,000 seconds / cycle, the time for holding at the oxidation potential per cycle becomes long, and the thickness of the polymerized film per cycle becomes thick, making it difficult for the anions in and out of the polymer. Becomes

The anions of the supporting salt are released from the polypyrrole molding by the undoping treatment. The easiness of release depends on the fine structure of polypyrrole in the molded body, and not all molecules are in the same state, but anions that are easily released are released.

The polymer molded product obtained here has a thickness suitable for being used as an electrode of a secondary battery, that is, 50 μm or more, preferably 50 to 2,000 μm.

Next, an anion (counter ion) having an ion size smaller than that of the anion of the supporting salt is introduced into and exchanged with the obtained polymer molded body to form a polypyrrole molded body for a polymer secondary battery of the present invention. obtain.

It is preferable that the anion of the supporting salt and the counter ion having a smaller ion size than that of the supporting salt have a larger size difference.

Smaller ionic size than the anion of the supporting salt
The anion is a molecule with a size of 8 Å or less.
No more than 150 ions₃ ^-, HSO_Four ^-,
BF _Four ^-, PF₆ ^-, CF₃SO₃ ^-, ClO_Four ^-Such
Can be mentioned. Electrolysis used especially in secondary batteries
BF when considering quality_Four ^-, PF₆ ^-And ClO _Four
^-Are particularly preferred.

As the method of ion-exchanging the anion of the supporting salt with an anion (counterion) having a smaller ion size than that, a method of raising or lowering the potential applied to the polypyrrole molded article in an electrolytic solution containing the anion for exchange and simply dipping There are two methods.

The method of raising and lowering the potential may be carried out under the conditions and conditions according to the above-mentioned polymerization method.

The immersion treatment method is carried out by simply immersing the polymer molded body in an electrolytic solution containing exchange ions. The electrolytic mass in the immersion liquid is required to be at least as large as the amount of anions contained in the immersed polymer, but is preferably 5 times or more, more preferably 10 times or more. Stirring of the dipping solution may be carried out with a stirrer, an ultrasonic oscillator or the like, or may be non-stirring. The immersion temperature is preferably higher because it promotes the exchange of ions. However, if the temperature is too high, undesired reactions such as side reactions occur, so 100 ° C. or lower, and more preferably 50 ° C. or lower. The immersion time for exchanging all the ions in the polymer is determined by the above immersion conditions. Generally, it is used for 1 hour to 100 hours, preferably 2 hours to 40 hours.

In this way, the anions in the polypyrrole are ion-exchanged with the counterions having a smaller ion size. This is because the diffusion of the anion in the polymer is forcibly repeated many times due to the rise and fall of the potential during the polymerization, so that the ion migration path corresponding to the size of the anion is formed over the entire thickness of the molded body. It is thought to be because Therefore, since the formed channels facilitate ion exchange with counter ions having a smaller ion size, the polypyrrole molded article of the present invention can be replaced by at least 50% or more according to the electrochemical or chemical treatment. is there. This exchange amount depends on the application conditions of the polymerization potential, and can be increased by lowering the reduction potential or decreasing the thickness of the polymerization film per cycle. Alternatively, the exchange amount of ions can be increased by increasing the time of negative current flowing between the electrodes in the electrolytic polymerization cycle.

The polymer secondary battery of the present invention is as described above.
The polymer incorporated in polypyrrole during polymerization
The anion of a salt-bearing salt is treated with anion of smaller ion size.
Use polypyrrole ion-exchanged as a positive electrode
It In the present invention, a seed is used as the negative electrode of the polymer secondary battery.
Various substances are used, but they may become mono- or divalent cations.
Metals such as lithium, sodium, and
Alkali metals such as helium, magnesium, calcium
Aluminum, barium, zinc, etc. and alloys containing them (Richiu
Mu-aluminum alloy, lithium-aluminum-lead
Gold or the like) can be preferably used. Furthermore, electrolysis
Something that allows reversible cations to enter and leave the liquid
Quality can be used, for example polyacetylene, poly-
Conducting p-phenylene, polythiophene, polyacene, etc.
An electro-polymer material or graphite is used. Starting
The electrolyte used in Akira's secondary battery is polypyrrole during polymerization.
Of the ionic size of the supporting salt anions
A compound consisting of a combination of small anions and cations
And an example of an anion is 8 angstroms in size.
An ion with a molecular weight of 150 or less at the trohm or lower, and NO
₃ ^-, HSO_Four ^-, BF _Four ^-, PF₆ ^-, CF₃SO₃
^-, ClO_Four ^-, I^-(I^3-), Br^-, Cl^-Etc.
Can be mentioned. Particularly preferably, BF_Four ^-, PF₆
^-And ClO_Four ^-Is mentioned. Also, the power of the secondary battery
Li as a cation for decomposition⁺, Na⁺, K⁺Such as
Lucari metal ion, Mg²⁺, Ca²⁺, Ba²⁺Such as
Lucari earth metal and Zn²⁺, Al²⁺And so on
It The electrolyte consisting of these anions and cations is a solvent
It is used in a secondary battery in a state of being dissolved in. Specific solvent
Examples of are acetonitrile, benzonitrile, water,
Propylene carbonate, ethylene carbonate, nit
Robenzene, tetrahydrofuran, nitromethane, sulfur
Horan, dimethoxyethane, and ethylene glycol
Ethylene glycol monomethyl ether, ethylene
Glycol monoethyl ether etc. and their mixture
Solvents may be mentioned. However, the negative electrode has a strong reactivity with water.
When using an alkali metal, a non-aqueous solvent containing no water
Need to be used. Furthermore, in the secondary battery of the present invention,
The above electrolyte is polyethylene oxide, polypropylene
Oxide, polyvinyl alcohol, polyparabanic acid
Where dissolved solid polymer electrolyte, Li₃N, LiBC
l_FourInorganic ion conductor such as Li_FourSiO_Four, Li₃
BO₃Inorganic solid electrolyte such as lithium glass is used
You can also do it.

In the charging / discharging mechanism of the polymer secondary battery, at the time of charging, the polypyrrole molded body of the positive electrode is electrochemically oxidized, and the anions present in the electrolytic solution are doped into the polypyrrole. On the other hand, at the time of discharging, the polypyrrole molded body of the positive electrode is reduced, and the undoping occurs in which the anions doped in the polypyrrole are released into the electrolytic solution. The polymer secondary battery using the polypyrrole molded article of the present invention as the positive electrode is obtained by ion-exchange with the counterion having a smaller ion size than the anion of the supporting salt incorporated into the polypyrrole at the time of polymerization by the above method. The anion doping and undoping reaction accompanying charge / discharge can proceed smoothly. Therefore, the polymer secondary battery using the molded body as a positive electrode can be charged and discharged at a high current density and can have a high charge and discharge capacity.

The anion concentration distribution during charge / discharge of the polypyrrole molded article was evaluated as follows. That is, the polypyrrole obtained by the above method was used as a positive electrode, platinum was used as a negative electrode, and lithium metal was used as a reference electrode (Ag as an auxiliary reference electrode).
/ AgCl electrode), a three-electrode battery was constructed by using a solution of 1 M LiClO ₄ dissolved in propylene carbonate as an electrolytic solution. Charging is 3.6 V (vs. Li / Li ⁺ , this value corresponds to 0.6 V in the case of Ag / AgCl)
Was subjected to constant-potential charging, and the distribution of anions in this direction in the thickness direction was examined by analyzing the chlorine element with an X-ray microanalyzer. The discharge was performed at a current density of 10 mA / cm ² , and the distribution of anions in the thickness direction was examined in the same manner.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0054]

Example 1 0.1M pyrrole monomer and 0.1M
P-toluenesulfonic acid tetraethylammonium salt of ((Et) ₄ NTsO) was dissolved in propylene carbonate containing 1% by volume of water to prepare an electrolytic solution. A platinum plate was used as the anode and a platinum foil was used as the counter electrode in this electrolytic solution to form a polymerization cell.

Next, with the waveform shown in FIG. 1, polymerization was carried out by holding the upper limit potential of 1.0 V (against Ag / AgCl) per cycle for 300 seconds, and sweeping the potential at a potential ascending / descending speed of 5 mV / sec. The lower limit potential is -1.0 V (against Ag / AgCl),
The holding time was set to 0 seconds, and the potential was swept to the upper limit potential again at a potential rising rate of 5 mV / sec, and the polypyrrole film thickness of 100 μm (10
Cycle) and electrolytic oxidation polymerization was carried out.

Then, the electrolytic solution used for the polymerization was replaced with propylene carbonate containing 1.0 M of lithium perchlorate (LiClO ₄ ), and the counter ion TsO ⁻ in the molded polypyrrole was used for a battery by an electrochemical method. A counterion exchange operation was performed to replace ClO ₄ ⁻ . Ion exchange is performed by using a triangular wave as a waveform for raising and lowering the potential.
The upper limit potential of the cycle was 1.5 V (vs Ag / AgCl), the lower limit potential was -1.5 V (vs Ag / AgCl), and the potential rising / falling rate was 5 mV / sec. The potential raising / lowering cycle was repeated 5 times.

Then, the polypyrrole film obtained by counterion exchange was cut out together with a platinum plate to form a positive electrode,
A platinum foil was used as a negative electrode, a lithium metal was used as a reference electrode (Ag / AgCl electrode as an auxiliary reference electrode), and a three-electrode battery was constructed using a solution of 1M LiClO ₄ dissolved in propylene carbonate as an electrolytic solution, with a current density of 10 mA. /
After discharging until the positive electrode potential became −1.0 V (vs Ag / AgCl) at cm ² , the polypyrrole film was taken out from the electrolytic solution and dried. Similarly, the polypyrrole film obtained by counter-ion exchange was cut out together with a platinum plate to form a positive electrode to form a three-electrode battery, and 0.6 V (against Ag / AgC
After carrying out constant potential charging in 1), the polypyrrole film was taken out from the electrolytic solution and dried.

As a result of examining the distribution of counterions in the thickness direction of the obtained film by analyzing chlorine with an X-ray microanalyzer, the chlorine distribution in the thickness direction of the film at the completion of charging is as shown in FIG. Was evenly distributed in the thickness direction of, and the distribution of chlorine was 13%. The chlorine concentration of the film at the completion of discharging was 14% or less of the concentration at the completion of charging. From this result, it is considered that p-toluenesulfonate ion, which is an anion taken in during the polymerization, is replaced with about 85% ClO ₄ ⁻ .

Next, the above-mentioned polypyrrole molded body having undergone counterion exchange was used as a positive electrode, lithium metal was used as a negative electrode, and the positive electrode and the negative electrode were immersed in an electrolytic solution in which 1M LiClO ₄ was dissolved in propylene carbonate. A secondary battery was prepared and the battery characteristics were examined. In addition, an Ag / AgCl electrode was used as a reference electrode to measure the positive electrode potential.

The battery characteristics of polypyrrole were measured by charging at a constant potential of positive electrode potential of 0.6 V (against Ag / AgCl) for 1 hour, and then discharging at a constant current of 1 to 10 mA / cm ² to obtain positive electrode potential. The discharge capacity was changed to −1.0 V (against Ag / AgCl) to examine the change in discharge capacity. Results are shown in FIG.
As is clear from FIG. 3, the discharge capacity per unit weight (discharge capacity density) at a discharge current density of 1 mA / cm ² is
It was 91 Ah / kg, which was an extremely high value. Also, 10
Discharge capacity density of 82A even with high discharge current density of mA / cm ^2.
h / kg was maintained. However, as the weight in the calculation of the discharge capacity density, the weight calculated from the amount of polymerization electricity was used, assuming that 0.33 counterions of the polypyrrole molded product were contained per unit of the pyrrole monomer.

[0061]

Comparative Example 1 Using the polymerization system shown in Example 1, 1.0
The anodic potential of V (against Ag / AgCl) was applied to carry out low-potential polymerization until the thickness of the polypyrrole molded article reached 100 μm, and counter ion exchange of polypyrrole was carried out under the same conditions as in Example 1.

As a result of X-ray microanalyzer analysis of this film, a large amount of sulfur element derived from TsO ⁻ introduced at the time of polymerization was confirmed.
It was shown that a large amount of chlorine element derived from ₄ ⁻ was present on and near the surface of the molded body, and only a part of TsO ⁻ was exchanged.

A three-electrode battery was constructed for this molded body in the same manner as in Example 1, and the distribution of ClO ₄ ⁻ was examined by analyzing the chlorine element concentration in the molded body during charging and discharging. At times, the vicinity of the surface was high, and it was hardly observed at a depth of 50 μm or more. The chlorine element concentration distribution at the time of completion of charging is shown in FIG.

Next, a secondary battery was prepared in the same manner as in Example 1 and the battery characteristics were examined. The discharge current density was 1 mA /
The discharge capacity density at cm ² is as low as 28 Ah / kg and 10
With a large current discharge of mA / cm ^2, the capacity further decreased to 21 Ah / kg. These results show that, when polymerized by the commonly used potentiostatic method without raising or lowering the applied potential, only a small amount of counterions were exchanged, and charging / discharging accompanying counterion entry and exit was also effective. It has not happened.
However, although the discharge capacity per unit weight was small, the ratio of the discharge capacity to the charge capacity in that range, that is, the Coulomb efficiency of charging and discharging was maintained at almost 100%. This indicates that the ratio of counter ions that can enter and exit is small, but the charge and discharge in that range is 100%.

[0065]

Comparative Example 2 A polypyrrole molded article containing TsO ⁻ as a counter ion obtained by the polymerization method in Example 1 was cut out together with a platinum plate without exchanging the counter ion to form a positive electrode, and lithium metal was used as a negative electrode. 1.0M lithium p
-Toluenesulfonic acid (LiTsO) was dissolved in propylene carbonate to prepare a secondary battery using an electrolytic solution, and the battery characteristics were investigated. Also, to measure the positive electrode potential, A
A g / AgCl electrode was used as a reference electrode. The battery characteristics of polypyrrole were measured with a positive electrode potential of 0.6 V (against Ag /
AgCl) constant potential for 30 minutes, followed by 1-10
Positive electrode potential is -1.0V after discharging with constant current of mA / cm ^2.
It was discharged until it became, and the change of the discharge capacity was examined. As a result, the discharge capacity at a discharge current of 1 mA / cm ² was 22 Ah / k.
At 10 mA / cm ² , g was 16 Ah / kg, and only a low discharge capacity was obtained.

[0066]

Comparative Example 3 (Et) ₄ N used for polymerization in Examples
Using (Et) ₄ NClO ₄ instead of TsO, polypyrrole was subjected to electrolytic oxidative polymerization under the same conditions as in Example 1 to a thickness of 100 μm.

Then, a three-electrode battery was constructed in the same manner as described above, and the distribution of ClO ₄ ⁻ was examined by analyzing the chlorine element under the same conditions as in Example 1 of the three-electrode battery. ClO ₄
^- concentration distribution of have decreased only film surface during discharge completion, was almost uniformly distributed throughout the film thickness at the time of completion of charging. In this case, Example 1 and Comparative Examples 1 and 2
Unlike in, ClO ₄ as an anion during polymerization ^-
As a result, a flat distribution of ClO ₄ ⁻ is naturally observed over the entire thickness during charging. However, at the time of discharging, the concentration of this anion was lower than that at the time of charging, but the degree of the decrease was small. This means that anions are not sufficiently removed.

Further, the discharge characteristics of a secondary battery prepared by using this polypyrrole in the same manner as above were examined. As a result, the capacities at current densities of 1 mA / cm ² and 10 mA / cm ² were 39 Ah / kg and 21 Ah / kg, respectively, and high discharge capacity could not be obtained. This result shows that even if the potential is raised or lowered, a high discharge capacity cannot be obtained unless ion exchange is performed from a large counter ion to a small counter ion as in the present invention.

[0069]

Example 2 In the same manner as in Example 1, a polypyrrole molded body having a thickness of 900 μm and containing TsO ⁻ as a counterion was prepared, and subsequently counterion exchange was performed with ClO ₄ ⁻ .

Using this molded body, a three-electrode battery was prepared in the same manner as in Example 1, and the chlorine element concentration distribution and the battery characteristics were examined. The distribution upon completion of charging was almost flat in the thickness direction of the molded body.

A secondary battery was prepared in the same manner as in Example 1 by using this polypyrrole molding. The relationship between the discharge current density and the discharge capacity of this battery is shown in FIG. As is clear from the figure, the discharge capacity is 8 at 1.0 mA / cm ^2.
It showed a high capacity density of 5 Ah / kg and maintained a high level of 78 Ah / kg even at 10 mA / cm ² .

[0072]

Examples 3 to 5 Instead of (Et) ₄ TsO shown in Example 1, tetraethylammonium β-naphthalenesulfonate (Example 3) and tetraethylammonium p-tert-butylbenzenesulfonate (Example 4) were used. Using triethylammonium salt of 5-sulfodimethylisophthalic acid ester (Example 5), 1% by volume of water was added to a mixed solvent of ethylene glycol and propylene carbonate (volume ratio 1: 1) as a solvent for the electrolytic solution. hand,
By the same method as in Example 1, a 100 μm-thick polypyrrole molded article containing the corresponding anion was prepared. Subsequently, ClO ₄ ⁻ was exchanged for a counterion in the same manner as in Example 1.

Using this molded body, a three-electrode battery was prepared, and in the same manner as in Example 1, from the chlorine element concentration distribution, ClO ₄
^- examined the distribution of.

In any case, the chlorine element concentration distributions at the completion of charging are shown in FIGS. 6 to 8 (FIG. 6: Example 3, FIG. 7: Example 4,
As shown in FIG. 8: Example 5), the ClO ₄ ⁻ distribution in the thickness direction was a flat distribution of 14% or less in all cases. At the end of discharging, the concentration of ClO ₄ ⁻ is 2 at the end of charging.
It was below 0%.

Table 1 shows the results of measuring the discharge characteristics of secondary batteries prepared by the same method as in Example 1 using these polypyrrole moldings. All of these results showed high battery characteristics as in the case of TsO ⁻ shown in Examples 1 and 2 of the present invention.

[0076]

[Table 1]

[0077]

[Effect] It is possible to provide a polymer secondary battery which uses a polypyrrole molded article and can be charged and discharged at a high current density and has a high charge and discharge capacity.

[Brief description of drawings]

FIG. 1 is a potential waveform diagram applied to an anode when electrolytically oxidatively polymerizing a polypyrrole molded article in Example 1 of the present invention.

FIG. 2 is a diagram showing the distribution of the chlorine element concentration in the thickness direction of the polypyrrole molded article according to Example 1 of the present invention by X-ray microanalyzer analysis.

FIG. 3 is a diagram showing a relationship between discharge current and capacity in Example 1 of the present invention.

FIG. 4 is a diagram showing a distribution of chlorine element concentration in a thickness direction of a polypyrrole molded article according to Comparative Example 1 by X-ray microanalyzer analysis.

FIG. 5 is a diagram showing the relationship between discharge current and capacity in Example 2 of the present invention.

FIG. 6 is a diagram showing the distribution of the chlorine element concentration in the thickness direction of the polypyrrole molded article according to Example 3 of the present invention by X-ray microanalyzer analysis.

FIG. 7 is a diagram showing the distribution of the chlorine element concentration in the thickness direction of the polypyrrole molded article according to Example 4 of the present invention by X-ray microanalyzer analysis.

FIG. 8 is a diagram showing the distribution of the chlorine element concentration in the thickness direction of the polypyrrole molded article according to Example 5 of the present invention as determined by X-ray microanalyzer analysis.

Claims (7)

[Claims] 1. A polymer secondary battery using a polypyrrole molded article produced by an electrolytic oxidation polymerization method as a positive electrode active material for a battery, wherein the polypyrrole molded article uses the polypyrrole molded article as a positive electrode and platinum as a negative electrode. A lithium metal was used as a reference electrode and LiClO ₄ was used as an electrolyte to form a three-electrode battery, which was discharged at a current density of 10 mA / cm ² and charged at a constant potential of 3.6 V. The anion concentration of 30% or less when the charging is completed, and the distribution of the anion concentration in the thickness direction of the molded body defined by the following formula is 50% or less when the charging is completed. Next battery. ## EQU1 ## {(Imax-Imin) / Imax} × 100 (%) (1) (where Imax is the maximum anion concentration in the thickness direction of the molded body, and Imin is the thickness direction of the molded body. Is the minimum anion concentration.) 2. The polypyrrole molded article has a thickness of 50 μm.
The polymer secondary battery according to claim 1, having a size of 2000 μm or less. 3. The pyrrole and anion have a molecular weight of 150.
As described above, a supporting ion composed of an anion having a large ionic size and its counter cation is immersed in a solution in which the electrode substrate is uniformly dissolved, and electrolytic polymerization is performed to form a thin film. Undoping treatment is performed, and at least 2 times of electrolytic polymerization and undoping treatment of this thin film are performed.
The polymer secondary battery according to claim 1, wherein a polypyrrole molded body formed by repeating the process at least once is used. 4. The polymer secondary battery according to claim 3, wherein the polypyrrole molded article is a polypyrrole molded article in which an anion having an ion size sufficiently smaller than the anion of the supporting salt is introduced and exchanged in the molded article. 5. An anion having a large ion size is contained by electrolytic polymerization in which a voltage value is alternately repeated between positive and negative with time, and a voltage having a large positive voltage period is applied. The polymer secondary battery according to claim 3, wherein a polypyrrole molded body is formed from a homogeneous solution of a supporting salt and pyrrole, and then an anion having a small ion size is introduced and exchanged in the molded body. 6. The polymer secondary battery according to claim 3, wherein the repeating period of the electrolytic polymerization and the undoping treatment is 10 to 10,000 seconds / cycle. 7. The polymer secondary battery according to claim 3, wherein the thickness of the molded body formed per one cycle of the electrolytic polymerization and the undoping treatment is 0.1 μm to 50 μm.