JP2009245900A - Electrode active material, and electrode using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode active material which can provide an electrochemical element having a high operating voltage, large capacity, and high energy density. <P>SOLUTION: The electrode active material is formed of poly 9, 9-bis (alkoxycarbonyl) fluorene. When the electrode active material is compared with a conventional electrode active material formed of poly 9, 9-dialkylfluorene providing an electrochemical element having a high operating voltage, they are equivalent to each other in terms of the capacity to p-doping, but the electrode active material formed of poly 9, 9-bis (alkoxycarbonyl) fluorene has high capacity to n-doping whereas the electrode active material formed of poly 9, 9-dialkylfluorene does not have capacity to n-doping. Accordingly, an electrochemical element having a high operating voltage, large capacity, and high energy density can be provided by using the electrode active material as a positive electrode active material and/or a negative electrode active material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrode active material that can provide an electrochemical element having a high operating voltage, a high capacity, and a high energy density, and an electrode using the electrode active material.

  Expectations for low-emission vehicles such as electric vehicles and hybrid vehicles to replace gasoline and diesel vehicles from the viewpoints of reducing oil consumption, mitigating air pollution, and reducing emissions of carbon dioxide that causes global warming. It is growing. As a motor drive power source in such a low pollution vehicle, an electrochemical element such as a secondary battery or an electric double layer capacitor having a high energy density and a high output density is used.

  Secondary batteries include batteries using an aqueous electrolyte and batteries using a non-aqueous electrolyte (organic electrolyte).

  Examples of batteries using acidic or alkaline aqueous electrolyte include lead batteries, nickel / cadmium batteries, nickel metal hydride batteries, and proton batteries. Since these secondary batteries have an electrolysis voltage of water of 1.23 V, a higher operating voltage cannot be obtained. As a power source for an electric vehicle, a high voltage of around 200V is required. To obtain this voltage, many batteries must be connected in series, which is disadvantageous for reducing the size and weight of the power source. is there. However, since the aqueous electrolyte has high ionic conductivity, it has excellent output characteristics that a large current can be obtained during charging and discharging.

On the other hand, lithium ion secondary batteries are well known as batteries using nonaqueous electrolyte solutions. In general, this battery uses a carbon material that occludes and releases lithium ions as a negative electrode, a lithium layered compound such as lithium cobaltate (LiCoO ₂ ) as a positive electrode, and a lithium salt such as lithium hexafluorophosphate (LiPF ₆ ). A solution dissolved in an organic solvent such as ethylene carbonate or propylene carbonate is used as an electrolytic solution. Since such a lithium ion secondary battery has a high electrolysis voltage of the organic solvent, an average operating voltage of 3.6 V can be obtained and the energy density is also high. However, since the charge / discharge reaction is occlusion and release of lithium ions in the electrode, the output characteristics are inferior, and it is disadvantageous as a power source for an electric vehicle that requires a large instantaneous current.

  The electric double layer capacitor uses a polarizable electrode such as activated carbon as positive and negative electrodes, and uses an electric double layer generated at the interface between the electrode surface and the electrolytic solution as a capacitance. An electric double layer capacitor has a high output density, can be rapidly charged and discharged, and has little capacity deterioration even after repeated charging and discharging. This is because in an electric double layer capacitor, electrolyte ions move only in the electrolytic solution along with charging / discharging and are adsorbed / desorbed to / from the electrode interface, and do not involve an electrochemical reaction as in a battery.

  Also in the electric double layer capacitor, there are a capacitor using an aqueous electrolyte and a capacitor using a non-aqueous electrolyte (organic electrolyte).

  Since the operating voltage of an electric double layer capacitor is mainly determined by the electrolysis voltage of the electrolyte, the capacitor using an aqueous electrolyte has a higher operating voltage than the capacitor using a non-aqueous electrolyte (organic electrolyte). It is disadvantageous in terms. However, it has the advantage of high power density and safety.

  On the other hand, an electric double layer capacitor using a non-aqueous electrolyte solution in which a quaternary onium salt such as boron tetrafluoride or phosphorus hexafluoride is dissolved in an organic solvent such as propylene carbonate has an operating voltage of an aqueous electrolyte solution. It is higher than the capacitor, but lower than the secondary battery. In addition, the energy density due to the electric double layer capacity is lower than that of the secondary battery, and the power source of the electric vehicle is greatly insufficient.

  In order to improve such problems, studies on electrode active materials used in electrochemical devices are underway.

  Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-297362) discloses a positive electrode mainly composed of a p-doped conductive polymer, a negative electrode mainly composed of a carbon material capable of inserting and extracting lithium ions, and a lithium salt. A hybrid secondary power source having an organic electrolyte solution is proposed. A secondary power source using a polythiophene having a weight average molecular weight of 50000, a poly (3-methylthiophene) having a weight average molecular weight of 80000, etc. as a positive electrode, an operating voltage of 4.0 V, and a secondary power source using activated carbon as a positive electrode A secondary power source having a capacity equal to or higher than that of the battery and having high charge / discharge cycle reliability is obtained.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 6-104141) discloses an electrolytic double layer for the purpose of increasing the capacity and reducing the internal resistance of an electric double layer capacitor provided with an electrode prepared using a conductive polymer powder paste. An electric double layer capacitor using a conductive polymer film obtained by a legal method as a polarizable electrode is proposed. By using the polypyrrole film obtained by the electrolytic polymerization method, an electric double layer capacitor having an operating voltage of 2.6 V and a higher capacity than an electric double layer capacitor having an electrode using a powder paste has been obtained.

  In order to improve the low energy density of the electric double layer capacitor, an electrochemical capacitor using an additional capacitance due to a redox reaction or a charge transfer reaction on the electrode surface in addition to the electric double layer capacitance has been studied. Yes. As an electrode active material for such an electrochemical capacitor, charge transfer by exchange of π-electrons with metal oxides such as ruthenium oxide, manganese oxide, nickel oxide, etc. where an oxidation-reduction reaction easily occurs, and anions and cations of electrolytes Conductive polymers such as polyaniline, polythiophene, polypyrrole and the like in which the above occurs relatively easily have been studied.

  Patent Document 3 (Japanese Unexamined Patent Publication No. 2000-315527) discloses a conductive polymer containing a thin film of triphenylamine as a repeating unit as a positive electrode and a thin film of 2,2′-bipyridine as a repeating unit. A non-aqueous electrochemical capacitor having a negative electrode made of a conductive polymer has been proposed, and a non-aqueous electrochemical capacitor exhibiting an operating voltage of up to 2.7 V and having an energy density more than three times that of an electric double layer capacitor has been obtained. Yes.

  Further, Patent Document 4 (Japanese Patent Laid-Open No. 2006-48974) discloses an electrode material composed of polyfluorene or a derivative thereof, and the n-doped redox potential of the polyfluorene derivative is compared with a conventional conductive polymer. In comparison, the p-doped redox potential of polyfluorene or its derivatives is higher than that of conventional conductive polymers, indicating that this electrode material has high voltage characteristics. When poly (9,9-dimethylfluorene) is used as the electrode active material, the secondary battery and electrochemical capacitor having a higher operating voltage than the secondary battery and electrochemical capacitor using poly (3-methylthiophene) Is obtained.

JP 2003-297362 A JP-A-6-104141 JP 2000-315527 A JP 2006-48974 A

  However, there is a constant demand for miniaturization and weight reduction of motor drive power supplies for electric vehicles, etc. Therefore, there is a strong demand for higher operating voltage, higher capacity, and higher energy density for electrochemical elements used as power supplies. There is.

  Accordingly, an object of the present invention is to provide an electrode active material having a higher capacity than a conventional conductive polymer capable of providing an electrochemical element having a high operating voltage, a high capacity and a high energy density, and an electrode using the same Is to provide.

  The electrode active material of the present invention for solving the above-mentioned problems is characterized by comprising at least one poly 9,9-bis (alkoxycarbonyl) fluorene.

  The electrode active material composed of poly 9,9-bis (alkoxycarbonyl) fluorene of the present invention is used as the electrode active material composed of poly 9,9-dialkylfluorene which gives an electrochemical device having a high operating voltage as disclosed in Patent Document 4. Compared to the material, although the capacity for p-doping is almost the same, the electrode active material made of poly-9,9-dialkylfluorene has little capacity for n-doping, whereas the poly-9 of the present invention. , 9-bis (alkoxycarbonyl) fluorene has an electrode active material with high capacity against n-doping. That is, the electrode active material comprising the poly 9,9-bis (alkoxycarbonyl) fluorene of the present invention has a high capacity for both p-doping and n-doping, so that the conventional poly 9,9- It is superior to an electrode active material made of dialkylfluorene, and is suitable as a positive electrode active material and / or a negative electrode active material.

  In the poly 9,9-bis (alkoxycarbonyl) fluorene, it is preferable that the fluorene ring is substantially polymerized at the 2-position and the 7-position. The term “substantially polymerized at the 2-position and the 7-position” is 90% or more, preferably 95% or more of the number of fluorene rings contained in poly 9,9-bis (alkoxycarbonyl) fluorene. More preferably, it means that 98% or more, particularly preferably 100%, of the fluorene ring is bonded to the adjacent fluorene ring at the 2nd and 7th positions.

  When poly 9,9-bis (alkoxycarbonyl) fluorene in which the fluorene ring is substantially polymerized at the 2-position and the 7-position is used as an electrode active material, poly 9,9-bis (not controlling the polymerization position of the fluorene ring) It has been found that the capacity is greatly increased compared to the use of (alkoxycarbonyl) fluorene as the electrode active material.

  The present invention also provides an electrode having an active material layer containing an electrode active material made of the above-mentioned poly 9,9-bis (alkoxycarbonyl) fluorene. The electrode active material comprising poly 9,9-bis (alkoxycarbonyl) fluorene of the present invention has a high capacity for both p-doping and n-doping, and is a positive electrode active material and / or a negative electrode active material. It is suitable as. Therefore, the electrode of the present invention can be suitably used to construct an electrochemical device having a high operating voltage, a high capacity and a high energy density, or as one of a pair of electrodes in a secondary battery, or It can be suitably used as one of a pair of electrodes in an electric double layer capacitor or as at least one of a pair of electrodes in an electrochemical capacitor. In particular, since the electrode active material comprising the poly 9,9-bis (alkoxycarbonyl) fluorene of the present invention has a high capacity for both p-doping and n-doping, the electrode of the present invention is used as an electrochemical capacitor. By using it as both the positive and negative electrodes in, it is possible to achieve higher operating voltage, higher capacity, and higher energy of the obtained capacitor.

  In the electrode of the present invention, the active material layer preferably contains at least one kind of carbon nanotube. Since carbon nanotubes have a high electrical conductivity, a composite with a high electrical conductivity can be obtained by compounding with an active material. Further, since the outer surface area is large, the contact surface with the active material is widened, and it is possible to impart conductivity with high efficiency. Furthermore, the carbon nanotubes themselves have a capacity in contact with the electrolyte solution. Therefore, by using poly 9,9-bis (alkoxycarbonyl) fluorene and carbon nanotubes in combination, an electrode having high capacity and low impedance characteristics can be obtained.

  Poly 9,9-bis (alkoxycarbonyl) fluorene is preferably supported on carbon nanotubes. Since the contact resistance between the carbon nanotube and the poly 9,9-bis (alkoxycarbonyl) fluorene is reduced, an electrode having further excellent low impedance characteristics can be obtained.

  The electrode active material composed of poly-9,9-bis (alkoxycarbonyl) fluorene of the present invention is compared with the conventional electrode active material composed of poly-9,9-dialkylfluorene which gives an electrochemical device having a high operating voltage. -Although the capacity for doping is almost the same, the electrode active material made of poly-9,9-dialkylfluorene has almost no capacity for n-doping, whereas the poly 9,9-bis (alkoxy) of the present invention. An electrode active material comprising carbonyl) fluorene has a high capacity for n-doping. Therefore, the electrode active material of the present invention is suitable as a positive electrode active material and / or a negative electrode active material, and an electrode having an active material layer containing the electrode active material of the present invention has a high operating voltage, high capacity and high energy. It is extremely useful for constructing electrochemical devices such as a secondary battery having a density, an electric double layer capacitor, and an electrochemical capacitor.

  The electrode active material of the present invention comprises poly 9,9-bis (alkoxycarbonyl) fluorene. The electrode active material of the present invention has a high capacity for n-doping, although the capacity for p-doping is almost the same as that of a conventional poly-9,9-dialkylfluorene. The electrode active material of the present invention has a capacity for n-doping because the polarity of the alkoxycarbonyl group is higher than that of the alkyl group, so that the ion diffusibility inside the polymer assembly is improved. .

  The poly 9,9-bis (alkoxycarbonyl) fluorene as the electrode active material may be a single material or a mixture of two or more kinds of poly 9,9-bis (alkoxycarbonyl) fluorene. . The alkoxycarbonyl group can have a linear or branched alkyl moiety. Examples of alkoxycarbonyl groups include methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentyloxycarbonyl, hexyloxycarbonyl, heptyloxycarbonyl, octyloxycarbonyl, nonyloxycarbonyl, decyloxycarbonyl, undecyloxycarbonyl, dodecyl And oxycarbonyl.

These poly-9,9-bis (alkoxycarbonyl) fluorenes are known per se and can be obtained by known methods. For example, poly 9,9-bis (alkoxy) represented by the formula I in which the fluorene ring is polymerized at any position by an electrolytic polymerization method using an electrolytic solution containing 9,9-bis (alkoxycarbonyl) fluorene. Carbonyl) fluorene is obtained.

Poly 9,9-bis (alkoxycarbonyl) fluorene preferably has a fluorene ring substantially polymerized at the 2nd and 7th positions as shown in Formula II.

  In formula I and formula II, R represents an alkyl moiety. FIG. 1 (a) shows the fluorene ring chain in the poly 9,9-bis (alkoxycarbonyl) fluorene represented by the formula II, and FIG. 1 (b) shows the poly 9,9 represented by the formula I. -The fluorene ring chain in bis (alkoxycarbonyl) fluorene was shown. In FIGS. 1A and 1B, the alkoxycarbonyl group is omitted for simplification. There are many branching sites and meta-conjugated sites in the molecular chain of the polymer represented by Formula I, but there are branching sites and meta-conjugated sites in the molecular chain of the polymer represented by Formula II. High charge utilization is expected because it is almost nonexistent. And it has been found that the capacity of the electrode active material composed of the polymer represented by the formula II is greatly increased as compared with the electrode active material composed of the polymer represented by the formula I. Therefore, by using an electrode active material composed of poly 9,9-bis (alkoxycarbonyl) fluorene in which the polymerization position of the fluorene ring represented by the formula II is precisely controlled, the capacity of the electrochemical device can be further increased. The Poly 9,9-bis (alkoxycarbonyl) fluorene in which the polymerization position of such a fluorene ring is precisely controlled includes a Yamamoto coupling method using a known nickel catalyst, a Suzuki-Miyaura coupling method using a palladium catalyst, etc. Can be obtained.

  Poly 9,9-bis (alkoxycarbonyl) fluorene can be doped to impart conductivity. As the doping process, either a chemical doping process or an electrochemical doping process may be employed.

Acceptors for chemical doping treatment include halogens such as Br ₂ , I ₂ and Cl ₂ , Lewis acids such as SO ₃ , BF ₃ , PF ₅ , AsF ₅ and SbF ₅ , HNO ₃ and H ₂ SO _4. Protonic acids such as HClO ₄ , CF ₃ SO ₃ H, FSO ₃ H, transition metal halides such as FeCl ₃ , MoCl ₅ , WCl ₅ , SnCl ₄ , MoF ₅ , tetracyanoethylene, tetracyanoquinodimethane, chloranil, etc. Organic materials such as Li, Na, K, and Cs can be used as donors.

As an acceptor for electrochemical doping treatment, Lewis acids such as BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ and SbF ₆ ⁻ , and halogen anions such as I ⁻ , Br ⁻ and Cl ⁻ can be used. As the donor, alkali metal ions such as Li ⁺ , Na ⁺ , K ⁺ , and Cs ⁺ , alkylammonium ions such as tetraethylammonium ions and tetrabutylammonium ions, and the like can be used.

  The doping amount is not particularly limited, but is preferably 5 to 100 mol% per fluorene monomer unit, more preferably 20 to 50 mol% per fluorene monomer unit. Polymerization may be performed after doping in a stage before polymerization, a method of doping after polymerization may be used, or doping may be performed by charging after electrode formation.

  The positive electrode active material subjected to these doping treatments undergoes a discharge reaction and a reduction reaction due to anodization of the anion. Further, the negative electrode active material subjected to these doping treatments causes a discharge reaction and an oxidation reaction due to cation dedoping.

  An electrode for an electrochemical device can be formed by providing an active material layer containing an electrode active material made of poly 9,9-bis (alkoxycarbonyl) fluorene of the present invention on a current collector.

  As the current collector, a conductive material such as platinum, gold, nickel, aluminum, titanium, steel, or carbon can be used. As the shape of the current collector, any shape such as a film shape, a foil shape, a plate shape, a net shape, an expanded metal shape, and a cylindrical shape can be adopted.

  The active material layer is prepared by dissolving the poly 9,9-bis (alkoxycarbonyl) fluorene described above in a solvent such as chloroform, tetrahydrofuran, N-methylpyrrolidone, isopropyl alcohol, and applying the obtained solution onto a current collector. You may form by drying. The film-shaped active material layer thus formed has a high capacity, is thin and uniform, and reduces the resistance of the electrode. Therefore, the IR drop during discharge can be reduced and the voltage of the electrode can be kept high. it can. Alternatively, an active material layer may be formed by inserting a current collector into a monomer solution for forming poly-9,9-bis (alkoxycarbonyl) fluorene and polymerizing the current collector.

  Alternatively, the active material layer may be formed using a mixed material in which the above-mentioned poly 9,9-bis (alkoxycarbonyl) fluorene is mixed with a binder and a conductive material.

  As the binder, known binders such as polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinyl fluoride, and carboxymethyl cellulose can be used. The content of the binder is preferably 1 to 20% by mass with respect to the total amount of the active material layer. When it is 1% by mass or less, the strength of the active material layer is not sufficient, and when it is 20% by mass or more, electrochemical characteristics such as capacity are insufficient.

  The conductive material may include known conductive materials such as carbon materials such as carbon black, natural graphite and artificial graphite, metal powders such as nickel and iron, and conductive oxides such as ITO. The content of these conductive materials is preferably 1 to 20% by mass with respect to the total amount of the active material layer. When the content is 1% by mass or less, the conductivity of the active material layer is insufficient, and when the content is 20% by mass or more, electrochemical characteristics such as capacity are insufficient.

  Other active materials may be further mixed in the active material layer as necessary. For example, other electrode active materials, for example, electron conductive polymers such as polythiophene, polypyrrole, and polyacene can be included. The amount of the other additive material is preferably 20% by mass or less based on the total amount of the active material layer. When it is 20% by mass or more, electrochemical characteristics such as capacity become insufficient.

  The electrode using the above-mentioned mixed material is obtained by dispersing the electrode active material of the present invention, a conductive material, and optionally other additive substances in a varnish in which a binder is dissolved, and collecting the obtained dispersion by a doctor blade method or the like. It can also be created by coating on top and drying. Alternatively, the obtained mixed material may be sandwiched between a net-like current collector to form an electrode.

  In a preferred form, the active material layer contains poly 9,9-bis (alkoxycarbonyl) fluorene and carbon nanotubes. As carbon nanotubes, carbon nanotubes obtained by arc discharge method, laser evaporation method, chemical vapor deposition (CVD) method, etc. can be used, and both single-walled carbon nanotubes and multi-walled carbon nanotubes can be used. These may be used in combination. Since carbon nanotubes have a high electrical conductivity, a composite with a high electrical conductivity can be obtained by compounding with an active material. Further, since the outer surface area is large, the contact surface with the active material is widened, and it is possible to impart conductivity with high efficiency. Furthermore, the carbon nanotubes themselves have a capacity in contact with the electrolyte solution. Therefore, by using poly 9,9-bis (alkoxycarbonyl) fluorene and carbon nanotubes together, an electrode having a high capacity and a low impedance characteristic can be obtained.

  An active material layer can be formed by mixing poly9,9-bis (alkoxycarbonyl) fluorene and carbon nanotubes. At this time, if necessary, the active material layer may be formed by mixing both using a dispersion medium and then drying. However, it is particularly preferable that poly 9,9-bis (alkoxycarbonyl) fluorene is supported on carbon nanotubes to form an active material layer. The carbon nanotubes are immersed in a solution in which poly 9,9-bis (alkoxycarbonyl) fluorene is dissolved in a solvent such as chloroform, tetrahydrofuran, N-methylpyrrolidone, isopropyl alcohol, and filtered after a predetermined time. It can be performed by collecting and drying. After drying, a poly 9,9-bis (alkoxycarbonyl) fluorene film is formed on the surface of the carbon nanotubes. This film has a high capacity, is thin and uniform and has a low resistance, and has good adhesion between the carbon nanotube and the poly 9,9-bis (alkoxycarbonyl) fluorene film and has a low contact resistance. The IR drop is further reduced, and the voltage of the electrode can be kept higher.

  The mass ratio of poly9,9-bis (alkoxycarbonyl) fluorene and carbon nanotube is generally in the range of 9: 1 to 1: 9, and preferably in the range of 8: 2 to 2: 8. Exceeding this range results in insufficient electrochemical properties.

  After forming an active material layer containing poly 9,9-bis (alkoxycarbonyl) fluorene and carbon nanotubes into a predetermined shape such as a sheet, the obtained molded body and a current collector are joined to obtain an electrode. Can do. For example, an electrode can be obtained by pressure-bonding the obtained molded body on a current collector. You may add a binder etc. as needed at the time of shaping | molding.

  The electrode of the present invention can be suitably used in an electrochemical device having a pair of electrodes, a separator disposed between the electrodes, and an electrolyte solution.

  As a separator used for an electrochemical element, a polyolefin fiber nonwoven fabric, a glass fiber nonwoven fabric, etc. are used suitably, for example. There are a nonaqueous electrolytic solution and an aqueous electrolytic solution as the electrolytic solution, and they are appropriately selected according to the application.

  As the solvent for the non-aqueous electrolyte, electrochemically stable ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, sulfolane, 3-methyl sulfolane, γ-butyrolactone, acetonitrile, and dimethoxyethane, N-methyl-2-pyrrolidone, dimethylformamide or a mixture thereof can be preferably used.

As a solute of the nonaqueous electrolytic solution, a salt that generates lithium ions when dissolved in an organic electrolytic solution can be used without any particular limitation. For _{example, LiPF 6, LiBF 4, LiClO} 4, LiN (CF 3 SO 2) 2, LiCF 3 SO 3, LiC (SO 2 CF 3) 3, LiN (SO 2 C 2 F 5) 2, LiAsF 6, LiSbF 6 Or a mixture thereof can be preferably used. Further, a quaternary ammonium salt or a quaternary phosphonium salt having a quaternary ammonium cation or a quaternary phosphonium cation can be used as a solute of the nonaqueous electrolytic solution. For example, a cation represented by R ¹ R ² R ³ R ⁴ N ⁺ or R ¹ R ² R ³ R ⁴ P ⁺ (where R ¹ , R ² , R ³ , and R ⁴ have 1 to 6 carbon atoms) Represents an alkyl group), PF ₆ ⁻ , BF ₄ ⁻ , ClO ₄ ⁻ , N (CF ₃ SO ₃ ) ₂ ⁻ , CF ₃ SO ₃ ⁻ , C (SO ₂ CF ₃ ) ₃ ⁻ , N (SO ₂ C _A salt composed of an anion composed of ₂ F ₅ ) ₂ ⁻ , AsF ₆ ^— or SbF ₆ ^— , or a mixture thereof can be suitably used. In particular, a salt using PF ₆ ⁻ , BF ₄ ⁻ , ClO ₄ ⁻ or N (CF ₃ SO ₃ ) ₂ ⁻ as the anion is preferable as the solute.

  Examples of the solute cations in the acidic, neutral or alkaline aqueous electrolyte include cations of alkali metals such as sodium and potassium, and protons. Solute anions in aqueous electrolytes include anions of inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, tetrafluoroboric acid, hexafluorophosphoric acid, hexafluorosilicic acid, saturated monocarboxylic acids, aliphatic carboxylic acids And anions of organic acids such as oxycarboxylic acid, p-toluenesulfonic acid, polyvinylsulfonic acid and lauric acid.

  The electrode of the present invention can be suitably used as at least one of a pair of electrodes in an electrochemical device. Poly-9,9-bis (alkoxycarbonyl) fluorene is approximately equivalent in capacity to p-doping compared to conventional electrode active materials consisting of poly9,9-dialkylfluorene that provide electrochemical devices with high operating voltages. However, the electrode active material composed of poly 9,9-dialkylfluorene has almost no capacity for n-doping, whereas the electrode active material composed of poly 9,9-bis (alkoxycarbonyl) fluorene of the present invention. Also has a high capacity for n-doping. Therefore, by using the electrode of the present invention as an electrode of any electrochemical element, an electrochemical element having a high operating voltage, a high capacity and a high energy density can be obtained. Hereinafter, each case where the electrochemical element is a secondary battery, an electric double layer capacitor, or an electrochemical capacitor will be described.

(Secondary battery)
In the case of a lithium secondary battery, a non-aqueous electrolyte solution having a lithium salt as a solute is used as the electrolyte solution. Then, the electrode of the present invention is used as the positive electrode, and an electrode using an electrode active material that occludes and releases lithium ions such as conventional lithium metal or natural graphite, artificial graphite, and petroleum coke is used as the negative electrode.

  In the lithium secondary battery having this configuration, the positive electrode of the present invention operates in a state in which the redox potential of p-doping is high in the same manner as the positive electrode using the conventional poly-9,9-dialkylfluorene, and further the non-aqueous electrolyte solution. Since the electrolysis voltage is high, the operating voltage can be increased, so the operating voltage is high, the capacity is high, and the energy density is high.

  Further, when the electrode active material of the present invention is used for the negative electrode and a conventional layered compound such as lithium cobaltate or a conductive polymer such as polyaniline or polyphenylene is used as the electrode active material for the positive electrode, lithium ion intercalation is caused. Therefore, a lithium secondary battery with improved output characteristics and cycle characteristics, high operating voltage, high capacity and high energy density can be obtained.

  In the case of forming a proton battery, an acid aqueous solution having protons is used as an electrolytic solution. And the electrode of this invention is used as a positive electrode, and the negative electrode in well-known proton batteries, such as a quinoxaline type polymer, is used as a negative electrode. The proton battery having this configuration uses an electrolytic solution made of an acid aqueous solution, so that the charge / discharge characteristics are good, the energy density is high, and the positive electrode of the present invention is a positive electrode using a conventional poly-9,9-dialkylfluorene. Similarly, it operates in a state where the redox potential of p-doping is high, and shows 1.2 V which is the maximum operating voltage in a battery using an aqueous electrolyte.

(Electric double layer capacitor)
As the electrolytic solution for the electric double layer capacitor, any of the above-mentioned non-aqueous electrolytic solution and aqueous electrolytic solution can be used. In an electric double layer capacitor using a non-aqueous electrolyte, the electrode of the present invention is used as a positive electrode or a negative electrode, and the other electrode is an electric material such as activated carbon, carbon fiber, phenol resin carbide, vinylidene chloride resin carbide, or microcrystalline carbon. An electrode having a double layer capacity is used. The positive electrode of the present invention operates in a state where the redox potential of p-doping is high like the conventional positive electrode using poly 9,9-dialkylfluorene, or the negative electrode of the present invention has a redox potential of n-doping. It operates in a low state and has a greatly increased capacity, and since the electrolysis voltage of the non-aqueous electrolyte is high, the operating voltage can be increased, so the operating voltage is high, high capacity and high energy density An electric double layer capacitor having the following can be obtained.

  In addition, in an electric double layer capacitor using an aqueous electrolyte, the electrode of the present invention is used as a positive electrode, and the other electrode is made of an electric two-layer such as activated carbon, carbon fiber, phenol resin carbide, vinylidene chloride resin carbide, and microcrystalline carbon. An electrode having a multilayer capacity is used. The electric double layer capacitor having this configuration can use acidic, neutral and alkaline aqueous solutions, has good charge / discharge characteristics, high energy density, and the positive electrode of the present invention is a conventional poly 9,9-dialkylfluorene. It operates in a state where the redox potential of p-doping is high as in the positive electrode using, and shows 1.2 V which is the maximum operating voltage in an electric double layer capacitor using an aqueous electrolyte.

(Electrochemical capacitor)
As an electrolytic solution for the electrochemical capacitor, a nonaqueous electrolytic solution having a quaternary ammonium salt or a quaternary phosphonium salt as a solute is used. Then, the electrode of the present invention can be used as the positive electrode, and an electrode using a conventional conductive polymer such as polyacetylene, polyacene, or polyphenylene having redox reaction characteristics as the negative electrode can be used as the electrode active material. In the electrochemical capacitor of this configuration, the positive electrode of the present invention has a capacity equivalent to that of a positive electrode using conventional poly-9,9-dialkylfluorene and a p-doping oxidation-reduction potential. And has a high energy density.

  In addition, a conventional conductive polymer such as polyaniline, polyacetylene and polyphenylene having redox reaction characteristics or an electrode using a metal oxide such as ruthenium oxide, manganese oxide and nickel oxide as an electrode active material is used as a positive electrode, and this electrode is used as a negative electrode. The electrode of the invention can also be used. In the electrochemical capacitor having this configuration, the negative electrode according to the present invention has a significantly increased capacity as compared with the conventional negative electrode using poly9,9-dialkylfluorene or metal oxide as an electrode active material, and n-doping redox. Since it operates at a low potential, it has a high operating voltage, high capacity and high energy density.

  Furthermore, when the electrode of the present invention is used for both of the pair of electrodes in the electrochemical capacitor, the redox potential of the negative electrode n-doping is low, the redox potential of the positive electrode p-doping is high, However, since it has a high capacity for n-doping, an electrochemical capacitor having an unprecedented high operating voltage, high capacity, and high energy density can be obtained.

  Examples of the present invention are shown below, but the present invention is not limited to the following examples.

Example An acetonitrile solution in which 10 mM 9,9-bis (hexyloxycarbonyl) fluorene monomer and 1M tetraethylammonium tetrafluoroborate were dissolved was used as a polymerization solution, a platinum electrode as a working electrode, an activated carbon sheet as a counter electrode, and silver as a reference electrode. Poly 9,9-bis (hexyloxycarbonyl) fluorene was polymerized and precipitated by a potential sweep method using a silver ion electrode. The sweep potential range was 0 V to +1.6 V, and the potential scanning speed was 100 mVs ⁻¹ . The polymer was peeled from the working electrode, dispersed in acetonitrile, filtered and washed to obtain poly 9,9-bis (hexyloxycarbonyl) fluorene represented by the following formula III.

Next, 20 mg of poly 9,9-bis (hexyloxycarbonyl) fluorene powder and 9.9 mg of carbon nanotube powder (specific surface area: 200 m ² / g) are added to 50 mL of isopropyl alcohol, and a dispersion is obtained by mechanical stirring. It was. The dispersion was filtered to obtain a sheet of poly 9,9-bis (hexyloxycarbonyl) fluorene / carbon nanotube composite in which poly 9,9-bis (hexyloxycarbonyl) fluorene was supported on carbon nanotubes. The sheet was cut to about 2 cm ² and crimped to an aluminum current collector of the same size to obtain a poly 9,9-bis (hexyloxycarbonyl) fluorene / carbon nanotube composite electrode. The thickness of the composite layer (active material layer) was 20 μm.

Next, a poly9,9-bis (hexyloxycarbonyl) fluorene / carbon nanotube composite electrode was used as the working electrode, an activated carbon sheet as the counter electrode, and a silver-silver ion electrode as the reference electrode, in a tripolar cell. Click voltammograms were measured. As the electrolytic solution, propylene carbonate in which 1M tetraethylammonium tetrafluoroborate was dissolved was used. The potential range was −3 V to +1.2 V, and the potential scanning speed was 5 mVs ⁻¹ .

Comparative Example Instead of the poly 9,9-bis (hexyloxycarbonyl) fluorene used in Example 1, a poly 9,9-dioctyl fluorene represented by the following formula IV (manufactured by Aldrich, product number 571652) was used. The procedure of Example 1 was repeated.

Table 1 shows the capacity density in the range of −0.65 to +1.2 V (capacity density with respect to p-doping) obtained from the results of the cyclic voltammograms of Examples and Comparative Examples, and −3.0 to − The value of capacity density (capacity density with respect to n-doping) in the range of 0.65 V is shown.

  As is apparent from Table 1, the poly 9,9-bis (hexyloxycarbonyl) fluorene / carbon nanotube composite electrode of the example was compared with the 9,9-dioctylfluorene / carbon nanotube composite electrode of the comparative example. Although the capacity for p-doping is almost the same, the comparative poly 9,9-dioctylfluorene / carbon nanotube composite electrode has little capacity for n-doping, whereas the poly 9 , 9-bis (hexyloxycarbonyl) fluorene / carbon nanotube composite electrode has high capacity for n-doping.

(A) is a figure which shows the fluorene ring chain | strand in the poly 9, 9-bis (alkoxycarbonyl) fluorene which the fluorene ring has superposed | polymerized in the 2nd and 7th position substantially, (b) It is a figure which shows the fluorene ring chain in the poly 9,9-bis (alkoxycarbonyl) fluorene polymerized in any position.

Claims (8)

  An electrode active material comprising at least one poly-9,9-bis (alkoxycarbonyl) fluorene.   The electrode active material according to claim 1, wherein in the poly-9,9-bis (alkoxycarbonyl) fluorene, a fluorene ring is substantially polymerized at the 2-position and the 7-position.   An electrode having an active material layer containing the electrode active material according to claim 1.   The electrode according to claim 3, wherein the active material layer contains at least one carbon nanotube.   The electrode according to claim 4, wherein the poly 9,9-bis (alkoxycarbonyl) fluorene is supported on the carbon nanotube.   The electrode according to any one of claims 3 to 5, which is used as one of a pair of electrodes in a secondary battery.   The electrode according to any one of claims 3 to 5, which is used as one of a pair of electrodes in an electric double layer capacitor.   The electrode according to any one of claims 3 to 5, which is used as at least one of a pair of electrodes in an electrochemical capacitor.

Images