WO2014103780A1

WO2014103780A1 - Nonaqueous electrolyte secondary battery, and positive electrode sheet used therein

Info

Publication number: WO2014103780A1
Application number: PCT/JP2013/083662
Authority: WO
Inventors: 敦子水池; 阿部　正男; 弘義武; 由姫加治佐; 愛美松浦
Original assignee: 日東電工株式会社
Priority date: 2012-12-25
Filing date: 2013-12-16
Publication date: 2014-07-03
Also published as: JP2014127274A

Abstract

The present invention is a nonaqueous electrolyte secondary battery having an electrolyte layer, and a positive electrode and a negative electrode disposed so as to sandwich the electrolyte layer. The positive electrode contains (a) a conductive polymer and (b) polysulfonic acid and/or a metal salt thereof. The negative electrode contains a material that allows a base metal or base metal ions to be inserted and eliminated. Thus, in addition to having excellent characteristics like those of an electric double layer capacitor, namely, excellent gravimetric power density and cycle characteristics, the nonaqueous electrolyte secondary battery has a high gravimetric energy density that far exceeds the gravimetric energy density of electric double layer capacitors of the prior art, and has capacitor-like characteristics.

Description

Nonaqueous electrolyte secondary battery and positive electrode sheet used therefor

The present invention relates to a non-aqueous electrolyte secondary battery and a positive electrode sheet used therefor, specifically, a non-aqueous electrolyte secondary battery excellent in both weight energy density and weight output density, and also excellent in cycle characteristics, And a positive electrode sheet used therefor.

In recent years, with the advancement and development of electronic technology in portable PCs, mobile phones, personal digital assistants (PDAs), secondary batteries that can be repeatedly charged and discharged are widely used as power storage devices for these electronic devices. Yes.

Among the secondary batteries described above, by using a lithium-containing transition metal oxide such as lithium manganate or lithium cobaltate as the electrode active material and using a carbon material that can insert and desorb lithium ions in the negative electrode, The so-called rocking chair type lithium secondary battery in which the lithium ion concentration in the electrolytic solution does not substantially change during the charge and discharge can reduce the amount of the electrolytic solution compared to the so-called reserve type secondary battery. Since it can be miniaturized and has a high energy density, it is widely used as an electricity storage device for the electronic devices described above.

However, a lithium secondary battery is an electricity storage device that obtains electric energy by an electrochemical reaction, and has an important problem that the output density is low because the speed of the electrochemical reaction is low.

Therefore, a non-aqueous electrolyte secondary battery using a conductive polymer such as polyaniline having a dopant as a positive electrode active material is also known (see Patent Document 1).

However, in general, a secondary battery having a conductive polymer as a positive electrode active material is an anion transfer type in which an anion is doped into the conductive polymer during charging and the anion is dedoped from the polymer during discharging. Therefore, when a carbon material that can insert and desorb lithium ions is used as the negative electrode active material, a cation-moving rocking chair type secondary battery in which cations move between both electrodes during charge and discharge cannot be configured. . That is, the rocking chair type secondary battery has the advantage that the amount of the electrolyte is small, but the secondary battery having the conductive polymer as the positive electrode active material cannot do so, and contributes to the miniaturization of the electricity storage device. I can't.

In order to solve such problems, a large amount of electrolytic solution is not required, and the ion concentration in the electrolytic solution is not substantially changed, thereby improving the capacity density per volume and weight. Mobile secondary batteries have also been proposed. In this method, a positive electrode is formed using a conductive polymer having a polymer anion such as polyvinyl sulfonic acid as a dopant, and lithium metal is used for the negative electrode (see Patent Document 2).

JP-A-3-129679 Japanese Patent Laid-Open No. 1-132052

However, the proposed secondary battery using the conductive polymer is not yet sufficient in performance, and a lithium secondary battery using a lithium-containing transition metal oxide such as lithium manganate or lithium cobaltate for the electrode. The weight energy density is low.

The present invention has been made in view of such circumstances, and has been made to solve the above-described problems in the conventional secondary battery, and is excellent in weight output density and cycle characteristics. A novel non-aqueous electrolyte secondary battery having a high weight energy density far exceeding the weight energy density of the secondary battery and a positive electrode sheet used therefor are provided.

The present invention relates to a non-aqueous electrolyte secondary battery having an electrolyte layer, and a positive electrode and a negative electrode provided therebetween, wherein the positive electrode comprises (a) a conductive polymer, (b) polysulfonic acid and its metal A first aspect of the present invention is a non-aqueous electrolyte secondary battery that includes at least one of salts and in which the negative electrode includes a material that can insert and desorb base metal or base metal ions.

The present invention also provides a non-aqueous electrolyte secondary comprising a composite having a positive electrode active material layer on a current collector, the positive electrode active material layer including (a) a conductive polymer and (b) at least one of polysulfonic acid and a metal salt thereof. The battery positive electrode sheet is a second gist.

That is, the present inventors made extensive studies in order to obtain a non-aqueous electrolyte secondary battery excellent in weight output density and cycle characteristics. As a result, by using at least one of (a) a conductive polymer and (b) polysulfonic acid and its metal salt as the positive electrode, the intended purpose is achieved, and the weight output density and cycle characteristics are excellent. It has been found that a secondary battery having a high weight energy density far exceeding the weight energy density of the secondary battery can be obtained.

Thus, the present invention is an electricity storage device having an electrolyte layer, a positive electrode and a negative electrode provided between the electrolyte layer, the positive electrode comprising (a) a conductive polymer, (b) polysulfonic acid and a metal salt thereof. The non-aqueous electrolyte secondary battery includes at least one of the above and the negative electrode includes a material that can insert and desorb base metal or base metal ions. Therefore, it is excellent as an electric double layer capacitor having excellent weight output density and cycle characteristics. In addition to having characteristics, it has a high weight energy density far exceeding that of conventional electric double layer capacitors. That is, the non-aqueous electrolyte secondary battery of the present invention is a secondary battery having capacitor characteristics.

(A) When the polymer constituting the conductive polymer is polyaniline or a polyaniline derivative, a secondary battery having an even higher weight energy density can be obtained.

When the polysulfonic acid (b) is a specific compound or the polysulfonic acid metal salt (b) is a specific metal salt, a secondary battery having a higher weight energy density can be obtained. It becomes like this.

It is sectional drawing which shows the structure of a nonaqueous electrolyte secondary battery typically. It is a cross-sectional schematic diagram of the non-aqueous electrolyte secondary battery produced using the positive electrode material containing polyaniline and polystyrene sulfonic acid.

Hereinafter, embodiments of the present invention will be described in detail. However, the description described below is an example of embodiments of the present invention, and the present invention is not limited to the following contents.

As shown in FIG. 1, the non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery having a non-aqueous electrolyte layer 3 and a positive electrode 2 and a negative electrode 4 provided therebetween. The positive electrode 2 is a complex composed of (a) a conductive polymer and (b) at least one of polysulfonic acid and a metal salt thereof, and (b) is fixed in the electrode. The negative electrode 4 is made of a material capable of inserting / extracting base metal or base metal ions.

<About positive electrode>
And the positive electrode sheet for non-aqueous electrolyte secondary batteries forming the positive electrode of the non-aqueous electrolyte secondary battery of the present invention comprises: (a) a conductive polymer; and (b) at least one of polysulfonic acid and a metal salt thereof. This is a composite having a positive electrode active material layer containing a current collector on the current collector, and this is a feature of the present invention.

<(A) Conductive polymer>
In the present invention, the above-mentioned (a) conductive polymer means that an ionic species is inserted into the polymer or from the polymer in order to compensate for a change in charge generated or lost by the oxidation reaction or reduction reaction of the polymer main chain. This refers to a group of polymers (hereinafter sometimes referred to as “electrode active materials”) in which the conductivity of the polymer itself is changed by desorption. In such a polymer, an ionic species is inserted into the polymer, and the conductivity is increased. A state with high conductivity is referred to as a doped state, and a state in which ionic species are desorbed from the polymer and conductivity is low is referred to as a dedope state. Even if a polymer having conductivity loses conductivity due to an oxidation reaction or a reduction reaction and becomes insulative (that is, a dedope state), such a polymer is reversibly conductive again by the oxidation-reduction reaction. Thus, the insulating polymer in the dedope state is also included in the category of the conductive polymer in the present invention.

Therefore, in the present invention, (a) one of the conductive polymers is preferably at least one protonic acid selected from inorganic acid anions, aliphatic sulfonate anions, aromatic sulfonate anions, polymer sulfonate anions and polyvinyl sulfate anions. A polymer having an anion as a dopant. In the present invention, another preferable conductive polymer is a polymer in a dedope state obtained by dedoping the conductive polymer.

In the present invention, examples of the polymer constituting the conductive polymer (a) include polypyrrole, polyaniline, polythiophene, polyfuran, polyselenophene, polyisothianaphthene, polyphenylene sulfide, polyphenylene oxide, polyazulene, poly (3,4- Ethylenedioxythiophene), polyacene and the like and various derivatives thereof are used. Especially, since the capacity | capacitance per unit weight of the conductive polymer obtained is large, at least 1 chosen from the group which consists of polyaniline and its derivative (s) is used preferably.

In the present invention, the polyaniline refers to a polymer obtained by electrolytic polymerization or chemical oxidative polymerization of aniline, and the polyaniline derivative refers to a polymer obtained by electrolytic polymerization or chemical oxidative polymerization of an aniline derivative. Say. Here, as the derivative of aniline, at least a substituent such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group, an aryloxy group, an alkylaryl group, an arylalkyl group, and an alkoxyalkyl group is present at a position other than the 4-position of aniline. What has one can be illustrated. Preferable specific examples include o-substituted anilines such as o-methylaniline, o-ethylaniline, o-phenylaniline, o-methoxyaniline, o-ethoxyaniline, m-methylaniline, m-ethylaniline, m Examples include m-substituted anilines such as -methoxyaniline, m-ethoxyaniline, m-phenylaniline.

However, according to the present invention, even if it has a substituent at the 4-position, p-phenylaminoaniline gives polyaniline by oxidative polymerization, so that it can exceptionally be suitably used as an aniline derivative.

Hereinafter, unless otherwise specified, in the present invention, “aniline or a derivative thereof” is simply referred to as “aniline”. Therefore, even when the polymer constituting the conductive polymer is obtained from an aniline derivative, it is referred to as “conductive polyaniline”.

In addition, in the present invention, as is well known, (a) a conductive polymer is obtained by electropolymerizing a monomer such as aniline in the presence of a protonic acid in an appropriate solvent or by using an oxidizing agent. Although it can be obtained by oxidative polymerization, it can be preferably obtained by oxidative polymerization of a monomer such as aniline with an oxidizing agent in the presence of a protonic acid in an appropriate solvent. As the solvent, water is usually used, but a mixed solvent of a water-soluble organic solvent and water or a mixed solvent of water and a nonpolar organic solvent is also used. In this case, a surfactant or the like may be used in combination.

The case where aniline is oxidatively polymerized using the above water as a solvent will be described in more detail. That is, chemical oxidative polymerization of aniline is carried out in water using a water-soluble chemical oxidant in the presence of a protonic acid.

Preferred examples of the oxidizing agent include ammonium peroxodisulfate, manganese dioxide, hydrogen peroxide, potassium dichromate, potassium permanganate, sodium chlorate, cerium ammonium nitrate, sodium iodate, and iron chloride. it can.

The amount of the oxidizing agent used for the oxidative polymerization of the aniline is related to the yield of the conductive polyaniline to be produced. In order to quantitatively react the used aniline, the number of moles of the aniline used (2.5 / N) It is preferable to use a mole of oxidizing agent. However, n represents the number of electrons required when one molecule of the oxidizing agent itself is reduced. Therefore, for example, in the case of ammonium peroxodisulfate, n is 2 as understood from the following reaction formula.

(NH ₄ ) ₂ S ₂ O ₈ + 2e → 2NH ⁴⁺ + 2SO ₄ ^2-

However, in order to suppress the polyaniline from being in a peroxidized state, it is slightly less than (2.5 / n) times the molar value of the aniline used, and the molar number of the aniline (2.5 / n). ) In some cases, a ratio of 30 to 80% with respect to the molar amount is used.

In the production of the conductive polyaniline, the proton acid is doped with the produced polyaniline to make it conductive, and the aniline is salted in water and dissolved in water. The pH of the polymerization reaction system is preferably 1 or less. Used to maintain strong acidity. Accordingly, in the production of the conductive polyaniline, the amount of the protonic acid used is not particularly limited as long as the above object can be achieved, but it is usually 1.1 to 5 times the number of moles of aniline. Used in a range. However, when the amount of the protonic acid used is too large, the cost for the waste liquid treatment is unnecessarily increased in the post-treatment of the aniline oxidative polymerization. Therefore, it is preferably used in the range of 1.1 to 2 moles. It is done. Thus, as the protonic acid, one having strong acidity is preferable, and a protonic acid having an acid dissociation constant pKa value of less than 3.0 is preferably used.

Examples of such protic acids having an acid dissociation constant pKa value of less than 3.0 include sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, tetrafluoroboric acid, hexafluorophosphoric acid, hydrofluoric acid, hydroiodic acid, and the like. Inorganic acids, aromatic sulfonic acids such as benzenesulfonic acid and p-toluenesulfonic acid, and aliphatic sulfonic acids (or alkanesulfonic acids) such as methanesulfonic acid and ethanesulfonic acid are preferably used. A polymer having a sulfonic acid group in the molecule, that is, a polymer sulfonic acid can also be used. Examples of such polymer sulfonic acids include polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, poly (acrylamide-t-butyl sulfonic acid), phenol sulfonic acid novolak resin, and Nafion (registered trademark). Examples thereof include perfluorosulfonic acid. In the present invention, polyvinyl sulfate can also be used as a protonic acid.

However, in addition to the above, for example, certain phenols such as picric acid, certain aromatic carboxylic acids such as m-nitrobenzoic acid, certain fats such as dichloroacetic acid, malonic acid, etc. Since the group carboxylic acid also has an acid dissociation constant pKa value of less than 3.0, it is used as a protonic acid in the production of conductive polyaniline.

Among the various proton acids mentioned above, tetrafluoroboric acid and hexafluorophosphoric acid are the same anions as the lithium salt of the electrolyte salt of the electrolyte solution in a lithium secondary battery which is an example of a non-aqueous electrolyte secondary battery, for example. Since it is a protonic acid containing a seed, it is preferably used.

According to the present invention, (a) the conductive polymer is obtained by doping the above-described polymer with the protonic acid, that is, the above-described polymer has the protonic acid as a dopant. In the non-aqueous electrolyte secondary battery according to, the positive electrode comprises such a conductive polymer and at least one of polysulfonic acid and its metal salt in the molecule. However, at least one of the polysulfonic acid and the metal salt thereof may be used in a free acid form as described later, or may be a metal salt form such as a lithium salt or a sodium salt. In the present invention, at least one of the polysulfonic acid and the metal salt thereof preferably has a pKa of 3.0 or more. Thus, the polysulfonic acid having a pKa of 3.0 or more is difficult to dope the polymer.

(A) The conductive polymer may be in a doped state (charged state) or in a reductive dedope state (discharged state) during charging or discharging.

(A) The conductive polymer is left as it is, and is usually in a doped state (in which ions are inserted). On the other hand, when the (a) conductive polymer is not in a doped state (charged state), a doped state is obtained by performing a doping treatment. Specific examples of the doping method include a method of mixing a dopant containing atoms to be doped into a starting material (for example, aniline in the case of polyaniline), a method of reacting a generated material (for example, polyaniline) with a dopant, and the like. It is done.

As described above, the ion insertion / desorption of the conductive polymer (a) is also referred to as so-called doping / dedoping, and a doping amount per certain molecular structure is called a doping rate, and the doping rate is The higher the material, the higher the capacity of the battery.

Here, in the present invention, the doping rate means the amount of doping / dedoping per certain molecular structure of the conductive polymer (a) conductive polymer as described above.

The non-aqueous electrolyte secondary battery of the present invention is usually an electrode (positive electrode) made of a material containing (a) a conductive polymer and (b) at least one of polysulfonic acid and a metal salt thereof described later. Is made using this. This electrode is made of at least one of the above-mentioned (a) conductive polymer and (b) polysulfonic acid and its metal salt in the form of a porous sheet.

<(B) At least one of polysulfonic acid and its metal salt>
In the present invention, the polysulfonic acid refers to a polymer having a sulfonyl group in the molecule. The polysulfonic acid is preferably polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, phenol sulfonic acid novolak resin, poly-2-acrylamido-2-methylpropane sulfonic acid, polyvinyl sulfuric acid, polymethacryl sulfonic acid. And a copolymer containing at least two kinds of repeating units of these polymers. These may be used alone or in combination of two or more. In the present invention, the copolymer includes a graft copolymer.

In the present invention, the metal salt of the polysulfonic acid is at least one of an alkali metal salt and an alkaline earth metal salt of polysulfonic acid, and the alkali metal salt is preferably a lithium salt or a sodium salt. The alkaline earth metal salt is preferably a magnesium salt or a calcium salt.

In the non-aqueous electrolyte secondary battery of the present invention, when (a) a conductive polymer and at least one of (b) polysulfonic acid and its metal salt are used, at least one of (b) polysulfonic acid and its metal salt is Since it functions as a binder and also as a dopant, it has a rocking chair type mechanism and is considered to be involved in improving the characteristics of the non-aqueous electrolyte secondary battery according to the present invention.

In the non-aqueous electrolyte secondary battery of the present invention, at least one of the (b) polysulfonic acid and the metal salt thereof is not limited at all, but has a function as a binder in the production of the positive electrode sheet, On the other hand, as will be described later, it seems to be involved in the improvement of the characteristics of the nonaqueous electrolyte secondary battery of the present invention.

In the positive electrode sheet for a non-aqueous electrolyte secondary battery in the present invention, the blending amount of at least one of the (b) polysulfonic acid and the metal salt thereof is usually 1 to 100 parts by weight of the conductive polymer (a). It is used in the range of 100 parts by weight, preferably 2 to 70 parts by weight, most preferably 5 to 40 parts by weight. When the blending amount of at least one of (b) polysulfonic acid and its metal salt with respect to (a) conductive polymer is too small, it becomes difficult to obtain a non-aqueous electrolyte secondary battery having excellent weight output density, and (a) conductive When the blending amount of at least one of (b) polysulfonic acid and its metal salt with respect to the conductive polymer is too large, it is difficult to obtain a non-aqueous electrolyte secondary battery having a high weight energy density.

Further, as the positive electrode sheet forming material, a binder other than the above (b), a conductive auxiliary agent, and the like are appropriately used together with at least one of the above (a) conductive polymer and (b) polysulfonic acid and a metal salt thereof. Can be blended.

The conductive auxiliary agent may be any conductive material whose properties do not change depending on the potential applied during the discharge of the electricity storage device, and examples thereof include conductive carbon materials and metal materials, among which acetylene black and ketjen black A conductive carbon black such as carbon fiber, or a fibrous carbon material such as carbon fiber or carbon nanotube is preferably used. Particularly preferred is conductive carbon black.

The conductive assistant is preferably 1 to 30 parts by weight, more preferably 4 to 20 parts by weight, particularly preferably 8 to 18 parts by weight based on 100 parts by weight of the conductive polymer (a). is there. When the blending amount of the conductive aid is within this range, the shape and characteristics as the active material can be prepared without abnormality, and the rate characteristics can be effectively improved.

Examples of the binder other than the above (b) include vinylidene fluoride and the like.

According to the present invention, a positive electrode sheet for a non-aqueous electrolyte secondary battery includes (a) a conductive polymer, (b) a solid positive electrode active material containing at least one of polysulfonic acid and a metal salt thereof, and And a composite sheet having a layer made of a conductive assistant or the like appropriately blended on the current collector, and the layer containing the positive electrode active material and the conductive assistant usually forms a solid porous layer.

The positive electrode sheet for a non-aqueous electrolyte secondary battery according to the present invention includes, for example, at least one of the above (b) polysulfonic acid and its metal salt dissolved in water to form an aqueous solution, and (a) a conductive polymer and necessary Depending on the current collector, a conductive additive such as conductive carbon black is added and dispersed sufficiently to prepare a paste. After applying this paste onto the current collector, water is evaporated, (A) a conductive polymer and (b) a sheet-like electrode as a composite having a layer of a uniform mixture of (polysulfuric acid and / or its metal salt) and (optionally a conductive aid), A positive electrode sheet can be obtained.

<About positive electrode>
Of the electrodes according to the non-aqueous electrolyte secondary battery of the present invention, the positive electrode is composed of a composite comprising (a) the conductive polymer and (b) at least one of polysulfonic acid and a metal salt thereof, It is formed into a porous sheet. The thickness of the electrode is preferably 1 to 1000 μm, more preferably 10 to 700 μm.

The thickness of the positive electrode is obtained by measuring using a standard dial gauge (manufactured by Ozaki Mfg. Co., Ltd.), which is a flat plate with a tip shape of 5 mm in diameter, and obtaining the average of 10 measured values with respect to the surface of the electrode. .

The positive electrode according to the nonaqueous electrolyte secondary battery of the present invention is produced, for example, as follows. (B) At least one of the polysulfonic acid and its metal salt is dissolved in water to form an aqueous solution, to which the above (a) conductive polymer and, if necessary, a conductive auxiliary agent and a binder other than the above (b) Is appropriately added and sufficiently dispersed to prepare a paste. After this is applied on the current collector, water is evaporated, and on the current collector, (a) a conductive polymer, (b) at least one of polysulfonic acid and its metal salt, and conductive as necessary. A sheet electrode (electrode) can be obtained as a composite (porous sheet) having a layer of a mixture of an auxiliary agent and a binder other than the above (b).

In the positive electrode formed as described above, (b) at least one of polysulfonic acid and its metal salt exists as a layer of a mixture with (a) a conductive polymer, and is thereby fixed in the electrode. . Thus, (a) at least one of (b) polysulfonic acid and its metal salt fixedly arranged in the vicinity of the conductive polymer is also used for charge compensation during oxidation-reduction of the conductive polymer (a). .

Therefore, as described above, the non-aqueous electrolyte secondary battery according to the present invention has a rocking chair type ion transfer mechanism, so that the amount of anion in the electrolyte that acts as a dopant is small. As a result, the power storage device can exhibit good characteristics even when the amount of the electrolytic solution used is small.

The porosity (%) of the electrode can be calculated by {(apparent volume of electrode−true volume of electrode) / apparent volume of electrode} × 100, preferably 30 to 95%, more preferably 50 to 90. %.

In the present invention, the apparent volume of the electrode refers to “electrode area of electrode × electrode thickness”. Specifically, the volume of the electrode substance, the volume of the voids in the electrode, and the space of the uneven portions on the electrode surface The total volume of

In the present invention, the true volume of the electrode means the “volume of the electrode constituent material” excluding the current collector such as an aluminum foil. Specifically, the constituent weight ratio of the positive electrode constituent material and the true volume of each constituent material. Using the density value, the average density of the entire electrode constituent material is calculated, and the total weight of the electrode constituent material is divided by this average density.

As the true density (true specific gravity) of each of the constituent materials, for example, (a) the true density of polyaniline, which is an example of a conductive polymer, is 1.2 (including a dopant), (b) polysulfonic acid and its metal salt The true density of polystyrene sulfonic acid, which is at least one example, was 1.0.

<About the electrolyte layer>
The electrolyte layer used in the non-aqueous electrolyte secondary battery of the present invention is composed of an electrolyte. For example, a sheet obtained by impregnating a separator with an electrolyte or a sheet made of a solid electrolyte is preferably used. The sheet made of the solid electrolyte itself also serves as a separator.

The electrolyte is composed of a solute and, if necessary, a solvent and various additives. Examples of such solutes include metal ions such as lithium ions and appropriate counter ions, sulfonate ions, perchlorate ions, tetrafluoroborate ions, hexafluorophosphate ions, hexafluoroarsenic ions, bis ions. A combination of (trifluoromethanesulfonyl) imide ion, bis (pentafluoroethanesulfonyl) imide ion, halogen ion and the like is preferably used. Therefore, specific examples of such an electrolyte include LiCF ₃ SO ₃ , LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiCl. Etc.

As the solvent used as necessary, for example, at least one nonaqueous solvent such as carbonates, nitriles, amides, ethers, that is, an organic solvent is used. Specific examples of such an organic solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, propionitrile, N, N′-dimethylacetamide, N-methyl-2- Examples include pyrrolidone, dimethoxyethane, diethoxyethane, and γ-butyrolactone. These may be used alone or in combination of two or more. In addition, what melt | dissolved the said solute in the said solvent may be called "electrolyte solution."

In the present invention, the separator can be used in various modes. As the separator, it is possible to prevent an electrical short circuit between the positive electrode and the negative electrode that are arranged to face each other across the separator. Furthermore, the separator is electrochemically stable, has a large ion permeability, and has a certain level. Any insulating porous sheet having mechanical strength may be used. Therefore, as the material of the separator, for example, a porous porous sheet made of a resin such as paper, nonwoven fabric, polypropylene, polyethylene, or polyimide is preferably used. These may be used alone or in combination of two or more.

<About negative electrode>
The negative electrode according to the nonaqueous electrolyte secondary battery of the present invention is formed using a negative electrode active material which is a base metal or a carbon material into which base metal ions can be inserted and desorbed during oxidation / reduction. Examples of the base metal include alkali metals such as metal lithium, metal sodium, and metal potassium, and alkaline earth metals such as metal magnesium and metal calcium, and examples of the base metal ion include ions of the base metal. be able to. In the present invention, a preferable nonaqueous electrolyte secondary battery is a lithium secondary battery, and therefore lithium can be used as a preferable base metal and lithium ion can be used as a preferable base metal ion. As the material capable of inserting and desorbing the base metal ions, a carbon material is preferably used, but silicon, tin and the like can also be used. In the present invention, “use” means not only the case where only the forming material is used, but also the case where the forming material is used in combination with another forming material. Is used at less than 50% by weight of the forming material.

Further, the non-aqueous electrolyte secondary battery of the present invention can use a current collector in addition to the above-described positive electrode, electrolyte layer, negative electrode and the like. The current collector is not particularly limited as long as it has good conductivity and stability, but a metal foil or mesh such as nickel, aluminum, stainless steel or copper is preferably used, and a stainless steel material is preferably used. Furthermore, when the negative electrode is a metal, the negative electrode itself may also serve as a current collector.

<About non-aqueous electrolyte secondary batteries>
A non-aqueous electrolyte secondary battery is assembled using the above materials. The battery is preferably assembled in a glove box under an inert gas atmosphere such as ultra-high purity argon gas.

The non-aqueous electrolyte secondary battery of the present invention has an excellent weight capacity density of (a) the weight capacity density per weight of the conductive polymer is usually 40 mAh / g or more, preferably 50 mAh / g or more.

Such a non-aqueous electrolyte secondary battery according to the present invention is excellent in weight output density and cycle characteristics as in an electric double layer capacitor, and is much higher than the weight energy density of a conventional electric double layer capacitor. Therefore, it can be said that the non-aqueous electrolyte secondary battery of the present invention is a capacitor-type secondary battery. The reason why the non-aqueous electrolyte secondary battery according to the present invention has such capacitor characteristics is not yet clear, but (a) at least one of polysulfonic acid and metal salt thereof combined with (a) conductive polymer. Dissociates moderately in the electrolyte and has a negative charge. This negative charge facilitates the movement of base metal ions (for example, lithium ions) between the electrodes, and rocking chair type non-aqueous electrolyte secondary It is inferred that it constitutes a battery.

The reason why the non-aqueous electrolyte secondary battery of the present invention has such a high weight capacity density is that, as described above, in the electrode formed as described above, (b) at least one of polysulfonic acid and its metal salt Is arranged as a layer of a mixture with (a) a conductive polymer, so that it is fixed in the electrode. Thus, (a) at least one of (b) polysulfonic acid and its metal salt fixedly arranged in the vicinity of the conductive polymer is also used for charge compensation during oxidation-reduction of the conductive polymer (a). . In addition, the ion environment of at least one of (b) polysulfonic acid and its metal salt facilitates the movement of ions to be inserted / extracted from (a) the conductive polymer. In addition, since it has a rocking chair type ion transfer mechanism, the amount of anions in the electrolytic solution acting as a dopant can be reduced. As a result, it is presumed that a non-aqueous electrolyte secondary battery capable of exhibiting good characteristics (such as high weight capacity density) even when the amount of electrolyte used is small.

As a preferred embodiment of the non-aqueous electrolyte secondary battery of the present invention, charge and discharge are exemplified by (a) using a conductive polyaniline as a conductive polymer and (b) a lithium secondary battery using a positive electrode containing polysulfonic acid. The doping mechanism for conductive polyaniline by polysulfonic acid in is shown below. In the following chemical formula, charging is shown from the upper formula to the lower formula, (a) the conductive polyaniline is doped with anion ions, and from the lower formula to the upper formula is discharge (Discharge), ( a) It shows the behavior that anion ions are dedope in conductive polyaniline. That is, when charging a lithium secondary battery, in the following chemical formula, as shown from the upper formula to the lower formula, a nitrogen atom having an unpaired potential in polyaniline is one-electron oxidized, and as a result, is generated. It is considered that as the counter ion of the cation radical, the electrolyte anion in the electrolytic solution or the polysulfonic acid anion present in the electrode is doped into the polyaniline to form a doped conductive polyaniline. On the other hand, when discharging a lithium secondary battery, in the following chemical formula, as shown from the lower formula to the upper formula, the cation radical site in the conductive polyaniline is reduced, and the initial state having an unshared electron pair is reduced. Return to electrically neutral polyaniline. At this time, if the anion that has interacted with Coulomb at the cation radical site is an electrolyte anion, the electrolyte anion moves from the vicinity of the conductive polymer to the electrolyte side.

However, when the anion that has interacted with Coulomb at the cation radical site is a sulfoxylate anion of polysulfonic acid as shown in the lower formula in the following chemical formula, the sulfoxy anion is a polymeric anion. Therefore, unlike the electrolyte anion, it cannot move to the electrolyte solution side and stays in the vicinity of the polyaniline. Therefore, in order to make the sulfoxylate anion electrically neutral, the lithium cation moves from the electrolyte solution to the vicinity of the conductive polymer, and the above formula shows the counter cation of the sulfoxylate anion. It seems to form a salt.

As an example of such a non-aqueous electrolyte secondary battery, a lithium secondary battery formed of a material containing (a) conductive polyaniline and (b) polysulfonic acid as a positive electrode and using lithium as a negative electrode is schematically shown. FIG. 2 shows the behavior of lithium ions and anion ions.

Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples.

First, prior to the production of non-aqueous electrolyte secondary batteries (lithium secondary batteries) as examples and comparative examples, the following components were prepared and prepared.

[(A) Preparation of conductive polymer]
As polyaniline (a) which is an electrode active material, conductive polyaniline powder using tetrafluoroboric acid as a dopant was prepared as follows.

(Conductive polyaniline powder)
To a 300 mL glass beaker containing 138 g of ion-exchanged water, 84.0 g (0.402 mol) of a 42 wt% concentration tetrafluoroboric acid aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd., reagent grade) is added to a magnetic stirrer. While stirring, 10.0 g (0.107 mol) of aniline was added thereto. When aniline was first added to the tetrafluoroboric acid aqueous solution, the aniline was dispersed as oily droplets in the tetrafluoroboric acid aqueous solution, but then dissolved in water within a few minutes to obtain a uniform and transparent aniline aqueous solution. Got. The aniline aqueous solution thus obtained was cooled to −4 ° C. or lower using a low temperature thermostat.

Next, 11.63 g (0.134 mol) of manganese dioxide powder (manufactured by Wako Pure Chemical Industries, Ltd., reagent grade 1) as an oxidizing agent is added little by little to the aqueous aniline solution, and the temperature of the mixture in the beaker is −1. The temperature was not exceeded. Thus, by adding an oxidizing agent to the aniline aqueous solution, the aniline aqueous solution immediately turned black-green. Thereafter, when stirring was continued for a while, a black-green solid started to be formed.

Thus, after adding the oxidizing agent over 80 minutes, the reaction mixture containing the produced reaction product was further stirred for 100 minutes while cooling. Thereafter, using a Buchner funnel and a suction bottle, the obtained solid was No. Suction filtration was performed with two filter papers (manufactured by ADVANTEC) to obtain a powder. This powder was stirred and washed in an aqueous solution of about 2 N tetrafluoroboric acid using a magnetic stirrer, then stirred and washed several times with acetone, and this was filtered under reduced pressure. The obtained powder was vacuum-dried at room temperature for 10 hours to obtain 12.5 g of conductive polyaniline having tetrafluoroboric acid as a dopant (hereinafter simply referred to as “conductive polyaniline”) as a bright green powder.

<Conductivity of conductive polyaniline powder>
After pulverizing 130 mg of the conductive polyaniline powder in a smoked mortar, vacuum-pressing was performed for 10 minutes under a pressure of 75 MPa using a KBr tablet molding machine for infrared spectrum measurement, and a conductive polyaniline disk having a thickness of 720 μm was formed. Obtained. The conductivity of the disk measured by the 4-terminal method conductivity measurement by the Van der Pau method was 19.5 S / cm.

[(B) Preparation of polysulfonic acid]
An 18% by weight polystyrene sulfonic acid aqueous solution (manufactured by Sigma-Aldrich Japan Co., Ltd., weight average molecular weight 75000) was prepared.

[Preparation of anode material]
A metal lithium foil (made by Honjo Metal Co., Ltd.) having a thickness of 0.05 mm was prepared.

[Preparation of electrolyte]
An ethylene carbonate / dimethylene carbonate solution (volume ratio 50:50) of lithium hexafluorophosphate having a concentration of 1 mol / dm ³ (LGB-00002, manufactured by Kishida Chemical Co., Ltd.) was prepared.

[Preparation of separator]
A separator nonwoven fabric (manufactured by Nippon Kogyo Paper Industries Co., Ltd., TF40-50) was prepared.

[Example 1]
<Forming a positive electrode using the above (a) and (b)>

[Production of positive electrode sheet containing conductive polyaniline powder]
After 0.27 g of the conductive polyaniline powder was mixed with 0.4 g of conductive carbon black powder (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.), this was mixed with a polystyrene sulfonic acid aqueous solution (Sigma Aldrich Japan Co., Ltd., weight average molecular weight 75000). ) In addition to 29.33 g, after kneading well with a spatula, dispersion treatment was performed for 6 minutes with an ultrasonic homogenizer to obtain a fluid dispersion. This dispersion is subjected to mild dispersion treatment (peripheral speed 20 m / min, stirring for 30 seconds) using a thin-film swirl type high-speed mixer (Plymix, Filmix 40-40 type) and has fluidity. A paste was obtained. Further, this paste was stirred and defoamed using a rotating / revolving mixer (manufactured by Shinky Co., Ltd., Awatori Nertaro MH-500).

Next, using a tabletop automatic coating apparatus (manufactured by Tester Sangyo Co., Ltd.), the above-mentioned defoamed paste was etched aluminum for an electric double layer capacitor at a coating speed of 10 mm / sec using a doctor blade type applicator with a micrometer. It apply | coated on foil (the Hosen company make, 30CB). Subsequently, after leaving at room temperature (25 degreeC) for 180 minutes, it dried on the hotplate of temperature 100 degreeC for 1 hour, and obtained the composite sheet.

In this composite sheet, the positive electrode active material layer made of conductive polyaniline powder, conductive carbon black and polysulfonic acid had a thickness of 30 μm and a porosity of 62%.

<Production of lithium secondary battery>
First, the composite sheet is cut into a size of 35 mm × 27 mm, a part of the active material is removed so that the active material layer of the composite sheet has an area of 27 mm × 27 mm, and a part of the active material layer Using the precision-resisting welding machine (NSW System, NSW-15) as the tab electrode attachment portion, the aluminum tab was welded to the composite sheet to obtain a positive electrode sheet.

On the other hand, as a negative electrode, a lithium metal foil roll (Honjo Metal Co., Ltd., width 29 mm × thickness 0.05 mm) was used, and the lithium metal foil roll was cut into a size of 29 mm × 29 mm in a glove box, and meshed. A negative electrode sheet was prepared by pressing and adhering a nickel tab to a SUS of 35 mm × 29 mm in shape, which was previously welded by ultrasonic welding.

As the separator, a separator nonwoven fabric for EDLC having a porosity of 55% (manufactured by Nippon Kogyo Paper Industries Co., Ltd., TF40-50) was used. In addition, the separator was cut into 35 mm × 35 mm so as to be slightly larger than the positive electrode sheet or the negative electrode sheet.

Using these positive electrode sheet, negative electrode sheet, separator, aluminum laminate film, and tab film, a lithium secondary battery was produced. That is, the positive electrode sheet, the negative electrode sheet, the separator, the aluminum laminate film, and the tab film were all put in a glove box immediately after being dried at 80 ° C. for 2 hours with a vacuum dryer. Then, the negative electrode sheet, the separator, and the positive electrode sheet were combined in this order so that the negative electrode sheet and the positive electrode sheet were not in contact with each other, and sandwiched between aluminum laminate films and heat sealed. The electrode tab portion was heat-sealed with the tab film sandwiched between them for the purpose of improving the adhesiveness with the aluminum laminate film. As the electrolytic solution, an ethylene carbonate / dimethylene carbonate solution (volume ratio 50:50) of lithium hexafluorophosphate having a concentration of 1 mol / dm ³ was used (LGB-00002, manufactured by Kishida Chemical Co., Ltd.), which was used as the positive electrode active material. And after adding so that it might become 1.3 times the volume of separator porosity, it sealed by heat sealing, and produced the laminated cell lithium secondary battery.

<Characteristics of lithium secondary battery>
The characteristics of the assembled lithium secondary battery were measured in a constant current-constant voltage charge / constant current discharge mode using a battery charging / discharging device (TOSCAT-3000, manufactured by Toyo System Co., Ltd.). Unless otherwise specified, the end-of-charge voltage is 4.2 V. After the voltage reaches 4.2 V by constant current charging, constant voltage charging is performed at a current value of 20% of the current value during constant current charging. Thereafter, constant current discharge was performed up to a discharge end voltage of 2.0V.

The lithium secondary battery was subjected to a charge / discharge cycle test at a charge / discharge current of 0.1 mA. As a result, the weight capacity density per positive electrode active material was 80.7 mAh / g and the weight energy with respect to the fifth discharge capacity. The density was 276 mWh / g.

[Example 2]
In Example 1, 36.90 g of a 25 wt% sodium polyvinyl sulfonate aqueous solution (manufactured by Sigma-Aldrich Japan Co., Ltd., weight average molecular weight 130000) was used instead of polystyrene sulfonic acid in the production of the positive electrode sheet. Otherwise, a positive electrode sheet was produced in the same manner as in Example 1, and a lithium secondary battery was produced in the same manner as in Example 1 using this positive electrode sheet. The lithium secondary battery thus obtained was subjected to a charge / discharge cycle test at a charge / discharge current of 0.1 mA in the same manner as in Example 1. As a result, the discharge capacity per positive electrode active material was measured for the fifth discharge capacity. The weight capacity density was 53.5 mAh / g, and the weight energy density was 171.3 mWh / g.

[Comparative Example 1]
In Example 1, styrene butadiene rubber was used instead of polystyrene sulfonic acid. Otherwise, a positive electrode sheet was produced in the same manner as in Example 1, and a lithium secondary battery was produced in the same manner as in Example 1 using this positive electrode sheet. The lithium secondary battery thus obtained was subjected to a charge / discharge cycle test at a charge / discharge current of 0.1 mA in the same manner as in Example 1. As a result, the discharge capacity per positive electrode active material was measured for the fifth discharge capacity. The weight capacity density was 44.8 mAh / g, and the weight energy density was 148 mWh / g. From this, it was confirmed that both the weight capacity density and the weight energy density were lower than those of Examples 1 and 2.

The results (weight capacity density, weight energy density) of the charge / discharge cycle test conducted at the charge / discharge current of 0.1 mA are also shown in Table 1 below.

Thus, it was confirmed that the weight capacity density and the weight energy density of the lithium secondary battery of Comparative Example 1 were lower than those of the lithium secondary batteries of Examples 1 and 2.

In the above embodiments, specific forms in the present invention have been described. However, the above embodiments are merely examples and are not construed as limiting. Various modifications apparent to those skilled in the art are contemplated to be within the scope of this invention.

The nonaqueous electrolyte secondary battery of the present invention can be suitably used as a secondary battery such as a lithium secondary battery. The non-aqueous electrolyte secondary battery of the present invention can be used for the same applications as conventional secondary batteries. For example, portable electronic devices such as portable PCs, cellular phones, and personal digital assistants (PDAs), Widely used in driving power sources for hybrid electric vehicles, electric vehicles, fuel cell vehicles and the like.

1 Current collector (for positive electrode)
2 Positive electrode 3 Electrolyte layer 4 Negative electrode 5 Current collector (for negative electrode)

Claims

A non-aqueous electrolyte secondary battery having an electrolyte layer, a positive electrode and a negative electrode provided therebetween, wherein the positive electrode is (a) a conductive polymer, and (b) at least one of polysulfonic acid and a metal salt thereof. And the negative electrode contains a material capable of inserting and releasing base metal or base metal ions.
(A) A polymer in which the conductive polymer has at least one proton acid anion selected from the group consisting of an inorganic acid anion, an aliphatic sulfonate anion, an aromatic sulfonate anion, a polymer sulfonate anion, and a polyvinyl sulfate anion as a dopant. The non-aqueous electrolyte secondary battery according to claim 1.
(A) The non-aqueous electrolyte secondary battery according to claim 1, wherein the conductive polymer is a polymer in a dedope state.
The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein (a) the polymer constituting the conductive polymer is polyaniline or a polyaniline derivative.
The polysulfonic acid of (b) is polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, phenol sulfonic acid novolak resin, poly-2-acrylamido-2-methylpropane sulfonic acid, polyvinyl sulfuric acid, polymethacryl sulfonic acid, and these The nonaqueous electrolytic secondary battery according to any one of claims 1 to 4, which is at least one selected from the group consisting of copolymers containing at least two types of polymer repeating units.
The nonaqueous electrolytic secondary battery according to any one of claims 1 to 5, wherein the polysulfonic acid metal salt of (b) is at least one of a polysulfonic acid alkali metal salt and a polysulfonic acid alkaline earth metal salt.
The nonaqueous electrolytic secondary battery according to any one of claims 1 to 6, which is a lithium secondary battery.
A non-aqueous electrolyte secondary battery comprising a composite having a positive electrode active material layer on a current collector containing (a) a conductive polymer and (b) at least one of polysulfonic acid and a metal salt thereof Positive electrode sheet.
(A) A polymer in which the conductive polymer has at least one proton acid anion selected from the group consisting of an inorganic acid anion, an aliphatic sulfonate anion, an aromatic sulfonate anion, a polymer sulfonate anion, and a polyvinyl sulfate anion as a dopant. The positive electrode sheet for a non-aqueous electrolyte secondary battery according to claim 8.
(A) The positive electrode sheet for a non-aqueous electrolyte secondary battery according to claim 8, wherein the conductive polymer is a polymer in a dedope state.
The positive electrode sheet for a nonaqueous electrolyte secondary battery according to any one of claims 8 to 10, wherein (a) the polymer constituting the conductive polymer is polyaniline or a polyaniline derivative.
The polysulfonic acid of (b) is polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, phenol sulfonic acid novolak resin, poly-2-acrylamido-2-methylpropane sulfonic acid, polyvinyl sulfuric acid, polymethacryl sulfonic acid, and these polymers. The positive electrode sheet for a non-aqueous electrolytic secondary battery according to any one of claims 8 to 11, wherein the positive electrode sheet is at least one selected from the group consisting of copolymers comprising at least two types of repeating units.
The positive electrode sheet for a non-aqueous electrolytic secondary battery according to any one of claims 8 to 12, wherein the polysulfonic acid metal salt of (b) is at least one of an alkali metal polysulfonate and an alkaline earth metal polysulfonate. .
The positive electrode sheet for a nonaqueous electrolytic secondary battery according to any one of claims 8 to 13, which is for a lithium secondary battery.