WO2015025763A1 - Condensateur électrochimique - Google Patents

Condensateur électrochimique Download PDF

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WO2015025763A1
WO2015025763A1 PCT/JP2014/071194 JP2014071194W WO2015025763A1 WO 2015025763 A1 WO2015025763 A1 WO 2015025763A1 JP 2014071194 W JP2014071194 W JP 2014071194W WO 2015025763 A1 WO2015025763 A1 WO 2015025763A1
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graphite
positive electrode
active material
material layer
lithium titanate
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PCT/JP2014/071194
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English (en)
Japanese (ja)
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日本ケミコン株式会社
覚 爪田
高木　和典
修一 石本
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Nippon Chemi-Con Corporation
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/04—Hybrid capacitors
    • H01G11/06—Hybrid capacitors with one of the electrodes allowing ions to be reversibly doped thereinto, e.g. lithium ion capacitors [LIC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
    • H01G11/28—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features arranged or disposed on a current collector; Layers or phases between electrodes and current collectors, e.g. adhesives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/34—Carbon-based characterised by carbonisation or activation of carbon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/46—Metal oxides
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/13—Energy storage using capacitors

Definitions

  • the present invention uses activated carbon for the positive electrode and an electrochemical capacitor using spinel type lithium titanate (Li 4 Ti 5 O 12 ) (hereinafter simply referred to as “lithium titanate”) for the negative electrode. About.
  • spinel type lithium titanate Li 4 Ti 5 O 12
  • lithium titanate spinel type lithium titanate
  • an electric double layer capacitor having a positive electrode and a negative electrode mainly composed of activated carbon
  • charging and discharging are performed by desorption of cations and anions in the electrolytic solution to the activated carbon.
  • this electric double layer capacitor has the advantages of being capable of rapid charge / discharge, excellent output characteristics, and excellent charge / discharge cycle characteristics, it has the problem of low energy density.
  • a lithium ion secondary battery using a material capable of occluding and releasing lithium ions as a positive electrode active material and a negative electrode active material lithium ions are released from the positive electrode by charging and stored in the negative electrode, and lithium ions are discharged by discharging. Is released and stored in the positive electrode.
  • Lithium ion secondary batteries have the advantages of being able to operate at high voltage and high energy density compared to electric double layer capacitors, but are difficult to rapidly charge and discharge and have problems with the reliability of the charge and discharge cycle. There is.
  • an electrochemical capacitor using activated carbon for the positive electrode and a material capable of occluding and releasing lithium ions for the negative electrode has been proposed as a power storage device taking advantage of both advantages, and titanic acid is used as the negative electrode active material.
  • titanic acid is used as the negative electrode active material.
  • the use of lithium is being considered.
  • Solid electrolyte interface (SEI) film is hard to be formed on the surface of lithium titanate, lithium dendrite does not precipitate, and there is almost no volume change when lithium ions are inserted into or extracted from lithium titanate, so it operates stably. It is expected that an electrochemical capacitor will be obtained.
  • Patent Document 1 Japanese Patent Laid-Open No. 2002-270175 discloses that a positive electrode including activated carbon, a negative electrode including lithium titanate, and an organic electrolyte including a lithium salt are 1.5 V to about 2.7 V.
  • An electrochemical capacitor operable in a range of is disclosed.
  • the positive electrode in order to reduce the resistance of the positive electrode, it is described that the positive electrode preferably contains 0.1 to 20% by mass of carbon black or graphite as a conductive agent.
  • the conductive carbon black is used as a conductive agent.
  • Patent Document 2 Japanese Patent Laid-Open No.
  • 2003-132945 includes an organic solvent electrolyte containing a lithium salt and a quaternary onium salt, a positive electrode containing activated carbon, and a negative electrode containing lithium titanate.
  • An electrochemical capacitor is disclosed that is operable in the range of .5V to about 3.1V.
  • a lithium salt and an onium salt in the electrolytic solution, the electric conductivity of the electrolytic solution can be increased, and the capacity density in large current discharge can be increased.
  • carbon black or graphite is contained in the positive electrode as a conductive agent in an amount of 0.1 to 20% by mass in order to reduce the resistance of the positive electrode.
  • the conductive carbon black is used as a conductive agent.
  • nanoparticle means a particle having a diameter of 100 nm or less in the case of a spherical particle, and the diameter (short axis) of the particle cross section in the case of a needle-like, tubular or fibrous particle. Means particles of 100 nm or less.
  • the nanoparticles may be primary particles or secondary particles.
  • Patent Document 3 Japanese Patent Application Laid-Open No. 2008-270795 discloses a reaction liquid containing a reaction inhibitor such as acetic acid and a conductive carbon that forms a complex with a titanium alkoxide, a lithium compound, and a titanium alkoxide in a rotatable reactor. Then, the reaction vessel is swirled to apply a shear stress and centrifugal force to the reaction solution to disperse the conductive carbon, and the chemical reaction proceeds to disperse the lithium titanate precursor on the conductive carbon with good dispersibility.
  • a reaction inhibitor such as acetic acid and a conductive carbon that forms a complex with a titanium alkoxide, a lithium compound, and a titanium alkoxide in a rotatable reactor.
  • Patent Document 4 Japanese Patent Laid-Open No. 2011-213556
  • a lithium titanate precursor is supported on conductive carbon by a chemical reaction in which shear stress and centrifugal force are applied, and then heat treatment is performed in a nitrogen atmosphere.
  • Patent Document 5 Japanese Patent Laid-Open No. 2011-216747
  • Patent Document 6 Japanese Patent Laid-Open No. 2011-216748
  • Patent Document 7 Japanese Patent Laid-Open No. 2011-216748
  • Patent Document 8 Japanese Patent Laid-Open No. 2012-146663
  • 10% by weight of ketjen black or carbon nanofiber is used as a conductive agent for the positive electrode.
  • the terminal voltage is shown by a line a in FIG. 1 between the terminal voltage and the discharge capacity or the terminal voltage and the discharge time in the constant current discharge in the range of about 2.8V to about 1.5V.
  • a linear change is required.
  • the capacity of the capacitor can be maximized, and the remaining capacity of the capacitor can be accurately predicted.
  • the relationship between the terminal voltage and the discharge capacity or the relationship between the terminal voltage and the discharge time in constant current discharge is measured. As shown by line b in FIG. 1, a phenomenon is observed in which the discharge capacity rapidly decreases when the terminal voltage is about 1.5V.
  • the SEI film is hard to be formed on the surface of the lithium titanate particles, if the capacitor experiences a high temperature of 50 ° C. or higher, gas generation due to decomposition of the electrolyte and formation of the SEI film on the surface of the lithium titanate particles And come to occur. This phenomenon becomes more prominent as the lithium titanate particles are finer. Since electrochemical capacitors are required to have heat resistance that can be used at 60 ° C., changes in capacitor characteristics due to the generation of gas and the formation of SEI film should be avoided. As a result of investigations by the inventors, a terminal voltage of 2.8 V or higher is applied at a temperature of 50 ° C.
  • aging an aging treatment is performed until the growth of the SEI film is substantially stopped (hereinafter referred to as “aging”) , which is referred to as “high temperature aging”), it was possible to suppress changes in characteristics during subsequent use of the capacitor. Since the growth rate of the SEI film and the amount of gas generated are in a proportional relationship, it is possible to confirm whether the growth of the SEI film has substantially stopped by monitoring the amount of gas generated. However, when the relationship between the terminal voltage and the discharge capacity or the terminal voltage and the discharge time in the constant current discharge is measured for the electrochemical capacitor subjected to the above aging, the terminal voltage is about 1. The phenomenon that the discharge capacity rapidly decreases in the vicinity of 5 V has become more prominent.
  • an object of the present invention is to reduce the amount of discharge capacity generated at a terminal voltage of about 1.5 V in an electrochemical capacitor using activated carbon for the positive electrode and lithium titanate for the negative electrode. It is to provide a reduced electrochemical capacitor.
  • the positive electrode is charged from the point A of about 3V relative to Li / Li + to the point B of about 4.3V with respect to Li / Li +, the negative electrode a point approximately 3V against Li / Li + through the point G from D to reduce the rapidly potential to point F of about 1.5V with respect to Li / Li +, to the point E remains subsequent potential was maintained at about 1.5V with respect to Li / Li + Charged.
  • the capacity from point D to point F is 5.8 mAh per gram of lithium titanate.
  • the terminal voltage at the end of charging, that is, the potential difference between point B and point E is about 2.8V.
  • the positive electrode is discharged from point B to point C, and the negative electrode is discharged from point E through point F to point G.
  • the terminal voltage at the end of discharge that is, the potential difference between point C and point G is about 1.5V. Therefore, the potential of the negative electrode at the end of the discharge rises from a potential of about 1.5 V to the positive side with respect to Li / Li + at the point F in the process from the point F to the point G. This is considered to be the reason why the discharge capacity rapidly decreases when the terminal voltage is around 1.5V.
  • the potential difference between point B and point F is about 2.8V.
  • the positive electrode is discharged from point B to point C, and the negative electrode is discharged from point F through point G to point H.
  • the potential difference between point C and point H is about 1.5V. Therefore, the potential of the negative electrode at the end of discharge rises rapidly from the potential of about 1.5 V to the positive side with respect to Li / Li + at point G in the process from point G to point H. This is considered to be the reason why the discharge capacity decreases more rapidly in the vicinity of the terminal voltage of about 1.5V.
  • the inventors have thought that the above phenomenon can be avoided by introducing into the positive electrode a component that causes an electrochemically irreversible reaction during initial charging. This will be described with reference to FIG.
  • the positive electrode is charged from the point A of about 3V relative to Li / Li + to the point B of about 4.3V with respect to Li / Li +, this time, it proceeds electrochemically above ingredients irreversible
  • the reaction causes an irreversible capacity from point B to point C.
  • the negative electrode is charged from the point E to about 3V relative to Li / Li + to the point H, G a point approximately 1.5V through F relative to Li / Li +.
  • the potential difference between point C and point G is about 2.8V.
  • the charge used only for charging in the negative electrode is distributed to the charge and the electrochemical irreversible reaction of the above components in the positive electrode, and the lithium titanate charging depth is equal to the irreversible capacity of the above components.
  • the positive electrode is discharged from point C to point D
  • the negative electrode is discharged from point G through point F to point H.
  • the potential difference between point D and point H is about 1.5V.
  • FIG. 2 it has been explained that the capacity from point D to point F is 5.8 mAh per gram of lithium titanate.
  • the irreversible capacity from point B to point C is 5.8 mAh per gram of lithium titanate.
  • graphite and expanded graphite are suitable as components that cause an electrochemical irreversible reaction during initial charging, and have completed the invention.
  • an irreversible reaction occurs in which anions in the electrolyte intercalate between the layer surfaces of graphite and / or expanded graphite. This reaction occupies a major part of the irreversible capacity.
  • graphite and expanded graphite exhibit high electrical conductivity and thus do not increase the internal resistance of the electrochemical capacitor. It has also been found that the use of graphite and / or expanded graphite suppresses changes in capacitor characteristics over time.
  • Patent Documents 1 to 8 describe that graphite can be used as a conductive agent, there is no indication that graphite is included in the positive electrode as a component that causes an electrically irreversible reaction during initial charging.
  • the present invention is disposed between a positive electrode having a positive electrode active material layer containing activated carbon, a negative electrode having a negative electrode active material layer containing lithium titanate, and the positive electrode active material layer and the negative electrode active material layer.
  • the present invention relates to an electrochemical capacitor characterized by exhibiting an initial irreversible capacity of 5.8 mAh or more.
  • expanded graphite is preferable because anions in the electrolytic solution easily intercalate between the layer surfaces.
  • the term “initial irreversible capacity” means an irreversible capacity that is recognized in the first charge / discharge.
  • the initial irreversible capacity of graphite and / or expanded graphite varies depending on the type and shape of the graphite and / or expanded graphite used, but can be determined as follows.
  • a half-cell A in which a positive electrode (working electrode) including a predetermined amount of graphite and / or expanded graphite and a predetermined amount of activated carbon and a lithium counter electrode are combined via a separator including an electrolyte to be used, and graphite and / or expansion.
  • the irreversible capacity is obtained by performing constant voltage charging with respect to Li / Li + in the range of 4.3 V to 4.5 V and subtracting the irreversible capacity of the half battery B from the irreversible capacity of the half battery A. Then, the amount of graphite and / or expanded graphite and the amount of lithium titanate are adjusted so that the graphite and / or expanded graphite exhibits an initial irreversible capacity of 5.8 mAh or more per gram of lithium titanate.
  • the irreversible reaction in which the anion in the electrolyte intercalates between the layer surfaces of graphite and / or expanded graphite is more likely to occur at higher temperatures. Therefore, 4.3 V to about Li / Li + at a temperature of about 60 ° C.
  • the initial irreversible capacity is obtained by performing constant voltage charging in the range of 4.5 V, the initial irreversible capacity can be obtained stably and quickly. At this time, to charge after reaching the 4.3 V ⁇ 4.5V relative to Li / Li +, and maintained at 4.3 V ⁇ 4.5V versus about 70 hours or more Li / Li +, and then discharged More preferably, the initial irreversible capacity is obtained.
  • the graphite and / or expanded graphite in the positive electrode may be contained in the positive electrode active material layer together with the activated carbon, or may be contained in the positive electrode as a layer different from the positive electrode active material layer.
  • graphite and / or expanded graphite is contained in the conductive adhesive layer that bonds the positive electrode active material layer and the current collector supporting the positive electrode active material layer, by adjusting the thickness of the conductive adhesive layer This is preferable because the initial irreversible capacity of the positive electrode can be easily adjusted.
  • the irreversible capacity of the activated carbon is mainly due to the electrochemical irreversible reaction of the surface functional groups occurring in the high temperature region. And when lithium titanate is a nanoparticle, even if high temperature aging is performed until the growth of the SEI film is almost stopped, the total surface area of the lithium titanate is activated carbon and graphite and / or expanded graphite. If the initial irreversible capacity of 4 mAh or more per 1 m 2 is adjusted to an amount that can be expressed, a linear relationship is maintained between the terminal voltage and discharge capacity of the capacitor or the terminal voltage and discharge time in constant current discharge, It was found that a rapid decrease in the discharge capacity in the vicinity of the terminal voltage of about 1.5 V is suppressed. This means that in order to form a stable SEI film on the surface of the lithium titanate nanoparticles, a charge corresponding to about 4 mAh is required per 1 m 2 of the surface area of the lithium titanate.
  • the initial irreversible capacity of the activated carbon varies depending on the type and shape of the activated carbon used, but can be determined as follows. Electrochemical irreversible reaction of the surface functional group of activated carbon hardly occurs at normal temperature, and only occurs at high temperature. Therefore, an electrolyte that is intended to use a positive electrode containing only activated carbon and no graphite and / or expanded graphite and a lithium counter electrode. Half-cells combined through separators containing irreversible capacity in high temperature measurement by charging at constant voltage in the range of 4.3V to 4.5V against Li / Li + at normal temperature and high temperature aging respectively. The value obtained by subtracting the irreversible capacity in the room temperature measurement is the irreversible capacity to be obtained.
  • the amount of activated carbon so that the irreversible capacity resulting from activated carbon and the irreversible capacity resulting from graphite and / or expanded graphite, in total, expresses an initial irreversible capacity of 4 mAh or more per 1 m 2 of lithium titanate surface area
  • the amount of graphite and / or expanded graphite, or both the amount of activated carbon and graphite and / or expanded graphite, and the amount of lithium titanate nanoparticles are adjusted. It is convenient to fix the amount of activated carbon to a desired amount and adjust the amount of graphite and / or expanded graphite.
  • An SEI film is formed on the surface of lithium titanate nanoparticles obtained by high-temperature aging of an electrochemical capacitor using lithium titanate nanoparticles as a negative electrode active material, and graphite and / or expanded graphite
  • An electrochemical capacitor in which an anion constituting a lithium salt is inserted between layer surfaces suppresses changes in characteristics when the capacitor is used, and the terminal voltage and discharge capacity of the capacitor or the terminal voltage and discharge time in constant current discharge. In addition, a good linearity relationship is maintained, and excellent rate characteristics are exhibited in which a decrease in capacity is suppressed even during discharge at a large current.
  • the discharge capacity generated at a terminal voltage of about 1.5 V The amount of decrease is reduced, and a substantially linear relationship is recognized between the terminal voltage and discharge capacity of the capacitor or the terminal voltage and discharge time in constant current discharge. Therefore, more capacitor capacity can be extracted, and the remaining capacity in the capacitor can be easily predicted. Further, the use of graphite and / or expanded graphite suppresses changes in capacitor characteristics over time.
  • the electrochemical capacitor of the present invention is disposed between a positive electrode having a positive electrode active material layer containing activated carbon, a negative electrode having a negative electrode active material layer containing lithium titanate, and the positive electrode active material layer and the negative electrode active material layer. And a separator holding a non-aqueous electrolyte containing a lithium salt, and the positive electrode further contains graphite and / or expanded graphite.
  • a separator holding a non-aqueous electrolyte containing a lithium salt and the positive electrode further contains graphite and / or expanded graphite.
  • the negative electrode includes a negative electrode active material layer containing lithium titanate and a current collector that supports the negative electrode active material layer.
  • the negative electrode active material layer is obtained by dispersing lithium titanate and, if necessary, a conductive agent in a solvent in which a binder is dissolved, and coating the obtained dispersion on a current collector by a doctor blade method or the like. It can be created by drying. Further, the obtained dispersion may be formed into a predetermined shape and may be pressure-bonded on the current collector.
  • Solvents for forming the dispersion include N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide
  • a nonaqueous solvent such as tetrahydrofuran or an aqueous solvent can be used, but a nonaqueous solvent is preferably used.
  • a solvent may be used independently and may be used in mixture of 2 or more types.
  • the binder for forming the dispersion includes polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, polyvinyl fluoride, carboxymethylcellulose, nitrocellulose, styrene.
  • Known binders such as butadiene rubber and acrylonitrile-butadiene rubber are used.
  • a nitrile polymer containing 80% by mass or more of a repeating unit derived from a nitrile group-containing monomer has low electrolyte swellability, and adhesion between particles in the negative electrode active material layer or a current collector with the negative electrode active material layer. It is a preferable binder because it has excellent adhesion to the body, can increase the density of lithium titanate in the negative electrode active material layer, and can reduce the internal resistance of the electrochemical capacitor.
  • nitrile polymer examples include, in addition to polyacrylonitrile and polymethacrylonitrile, modified acrylonitrile resin obtained by copolymerizing acrylonitrile and / or methacrylonitrile with acrylic acid, methacrylic acid, acrylic ester, methacrylic ester and the like. Is mentioned. In particular, acrylic acid-methoxytriethylene glycol acrylate-acrylonitrile terpolymer is preferable. These polymers may be used alone or in combination of two or more.
  • the content of the binder is in the range of 1 to 30% by mass, preferably 1 to 5% by mass with respect to the entire dispersion. If it is 1% by mass or less, the strength of the active material layer is not sufficient, and if it is 30% by mass or more, disadvantages such as a decrease in discharge capacity of the negative electrode and an excessive internal resistance occur.
  • lithium titanate those manufactured by a known method can be used without any particular limitation.
  • titanium dioxide and lithium carbonate or lithium hydroxide are mixed so that the mass ratio of titanium: lithium is 5: 4, and calcined in an oxygen-containing atmosphere at a temperature of 700 to 1000 ° C. to obtain lithium titanate particles. be able to.
  • an aqueous solution containing a lithium salt and a titanium salt may be treated by spray drying or the like to evaporate the solvent, and the resulting mixture may be fired.
  • the lithium titanate obtained by these methods can be pulverized and used.
  • the pulverization may be wet pulverization or dry pulverization.
  • Examples of the pulverizer include a lykai device, a ball mill, a bead mill, a rod mill, a roller mill, a stirring mill, a planetary mill, a hybridizer, a mechanochemical compounding device, and a jet mill.
  • carbon black such as ketjen black, acetylene black, channel black, fullerene, carbon nanotube, carbon nanofiber, amorphous carbon, carbon fiber, natural graphite, artificial graphite, graphitized ketjen black, mesoporous carbon, etc.
  • the conductive carbon powder can be used.
  • vapor grown carbon fiber can be used.
  • acetylene black is a suitable conductive agent that improves the rate characteristics of the electrochemical capacitor, although it seems to be due to an increase in the electrical conductivity of the active material layer.
  • These carbon powders may be used alone or in combination of two or more.
  • supporting a lithium titanate precursor on electroconductive carbon by the chemical reaction which added the shear stress and the centrifugal force described in patent document 3 and patent document 4, It is suitably used for the negative electrode active material layer in the electrochemical capacitor of the present invention.
  • conductive materials such as aluminum, copper, iron, nickel, titanium, steel, and carbon can be used.
  • Aluminum or copper having high thermal conductivity and electronic conductivity is preferable.
  • 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 conductive adhesive layer may be formed by applying a composition obtained by adding a conductive carbon powder or metal powder as a conductive agent to a solvent and a thermosetting resin or thermoplastic resin as a binder on a current collector. it can. Since the negative electrode active material layer and the current collector are electrically connected by the conductive adhesive layer, the internal resistance of the electrochemical capacitor is reduced.
  • graphite and / or expanded graphite may be contained, but depending on the graphite and / or expanded graphite contained in the negative electrode, the anion in the electrolytic solution between the graphite and / or the expanded graphite layer surface The initial irreversible capacity mainly due to the intercalation of is not expressed.
  • the positive electrode includes a positive electrode active material layer containing activated carbon and a current collector that supports the positive electrode active material layer.
  • the positive electrode further contains graphite and / or expanded graphite.
  • expanded graphite is preferable because anions in the electrolytic solution easily intercalate between the layer surfaces.
  • Graphite and / or expanded graphite may be contained in the positive electrode active material layer together with the activated carbon, may be contained in the positive electrode as a layer different from the positive electrode active material layer, or may be contained in both.
  • graphite having a single multilayer structure as a whole is preferable because intercalation of anions in the electrolyte between the layer surfaces is likely to occur.
  • natural graphite, quiche graphite, highly oriented pyrolytic graphite Etc. are suitable.
  • expanded graphite conventionally known ones can be used without particular limitation. Expanded graphite can be produced by a known method. For example, after immersing natural graphite in a mixed aqueous solution of sulfuric acid and nitric acid, the natural graphite is taken out from the mixed aqueous solution, washed with water, and then rapidly heated to form natural graphite. There is a method of widening the distance between the layer surfaces of natural graphite by decomposing the compound that has entered between the layer surfaces. Functional groups may be artificially bonded to graphite and expanded graphite chemically or by weak interaction.
  • the positive electrode active material layer is, for example, dispersed in activated carbon powder and, if necessary, a conductive agent in a solvent in which a binder is dissolved, and the obtained dispersion is coated on a current collector by a doctor blade method or the like. Then, it can be created by drying. Further, the obtained dispersion may be formed into a predetermined shape and may be pressure-bonded on the current collector.
  • the activated carbon raw material examples include pitch-based raw materials such as petroleum pitch, coal-based pitch, and mesophase pitch, coke-based raw materials obtained by heat-treating these pitch-based materials, palm-based raw materials such as wood flour, phenol Synthetic resin raw materials such as resin, vinyl chloride resin, resorcinol resin, polyacrylonitrile, polybutyral, polyacetal, polyethylene, polycarbonate, polyvinyl acetate, and their carbides can be used.
  • pitch-based raw materials such as petroleum pitch, coal-based pitch, and mesophase pitch
  • coke-based raw materials obtained by heat-treating these pitch-based materials palm-based raw materials such as wood flour
  • phenol Synthetic resin raw materials such as resin, vinyl chloride resin, resorcinol resin, polyacrylonitrile, polybutyral, polyacetal, polyethylene, polycarbonate, polyvinyl acetate, and their carbides can be used.
  • an alkali activation treatment using potassium hydroxide, sodium hydroxide, lithium hydroxide, cesium hydroxide, rubidium hydroxide or the like as an activation agent a chemical activation treatment using zinc chloride, phosphoric acid or the like as an activation agent
  • Examples thereof include a gas activation process using carbon, air or the like as an activator, a steam activation process using water vapor as an activator, and the like.
  • alkali activation treatment is preferable because it gives activated carbon having a highly developed pore structure.
  • the description of the solvent, conductive agent and binder for obtaining the dispersion for the negative electrode active material layer also applies to the positive electrode active material layer.
  • Graphite and / or expanded graphite can be included in the positive electrode active material layer also serving as a conductive agent.
  • the description of the current collector for the negative electrode also applies to the positive electrode.
  • a current collector having a conductive adhesive layer containing graphite and / or expanded graphite as a conductive agent is used.
  • An electric body is preferably used.
  • the positive electrode contains graphite and / or expanded graphite in an amount that develops an initial irreversible capacity of 5.8 mAh or more per gram of lithium titanate constituting the negative electrode active material layer.
  • the amount of decrease in discharge capacity that occurs when the terminal voltage is about 1.5 V is greatly reduced, and there is a substantially linear relationship between the terminal voltage and discharge capacity of the capacitor or the terminal voltage and discharge time in constant current discharge. It will be recognized.
  • the total amount of activated carbon and graphite and / or expanded graphite is adjusted to an amount capable of expressing an initial irreversible capacity of 4 mAh or more per 1 m 2 of lithium titanate surface area.
  • the discharge capacity per unit mass of lithium titanate and the discharge capacity per unit mass of activated carbon are referred to, and 100% discharge capacity of lithium titanate is 100% discharge capacity of activated carbon. It is preferable that the amounts of lithium titanate and activated carbon are adjusted so as to be in the range of 1.75 to 3.7 times the above. When the 100% discharge capacity of lithium titanate is less than 1.75 times the 100% discharge capacity of activated carbon, the increase of the DC internal resistance in the electrochemical capacitor becomes significant, and the change of the DC internal resistance due to high temperature experience becomes significant. .
  • 100% discharge capacity of lithium titanate exceeds 3.7 times the 100% discharge capacity of activated carbon, it is no longer possible to expect a decrease in DC internal resistance, and the capacity per volume of the electrochemical capacitor product will decrease.
  • 100% discharge capacity per unit mass of lithium titanate and 100% discharge capacity per unit mass of activated carbon mean values obtained by the following methods.
  • a half-cell is formed by combining a working electrode having a negative electrode active material layer containing lithium titanate and a lithium counter electrode through a separator containing an electrolyte to be used, and at a rate of 1 C, 3V to Li / Li + Charging / discharging is performed in the range of 1 V, and the discharge capacity per 1 g of lithium titanate during this period is defined as 100% discharge capacity per unit mass of lithium titanate.
  • Charging / discharging is performed in the range of 3 V to 3 V, and the discharge capacity per 1 g of activated carbon during this period is defined as 100% discharge capacity per unit mass of activated carbon.
  • the electrochemical capacitor of the present invention includes a separator holding a non-aqueous electrolyte containing a lithium salt between a positive electrode active material layer and a negative electrode active material layer.
  • a separator well-known separators, such as a polyolefin fiber nonwoven fabric, a glass fiber nonwoven fabric, a polyolefin microporous membrane, a cellulose fiber cloth, can be used without particular limitation, for example.
  • As the electrolytic solution retained in the separator an electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent is used, and a known non-aqueous electrolytic solution can be used without any particular limitation.
  • solvent of the non-aqueous electrolyte solution there is no particular limitation on the solvent of the non-aqueous electrolyte solution, and carbonates, ethers, ketones, lactones, nitriles, hydrocarbons, esters, phosphate ester compounds, sulfolane compounds, etc. may be used. Suitable are ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, sulfolane, 3-methyl sulfolane, ⁇ -butyrolactone, acetonitrile, dimethoxyethane, diethoxyethane or mixtures thereof.
  • a mixed solvent of ethylene carbonate and dimethyl carbonate is considered to be due to an increase in the diffusion rate of lithium ions due to the low viscosity characteristics of the solvent, but is a suitable solvent that improves the rate characteristics of the electrochemical capacitor.
  • vinylene carbonate, vinyl ethylene carbonate, propane sultone, butane sultone, ethylene sulfide, and sulfolene can be added to the electrolytic solution.
  • vinylene carbonate is a suitable additive.
  • a salt that generates lithium ions when dissolved in an organic electrolytic solution can be used without any particular limitation.
  • 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 , LiPF 3 (C 2 F 5 ) 3 or a mixture thereof can be suitably used.
  • the concentration of the lithium salt is generally in the range of 0.1 to 2.5 mol / L, preferably 0.5 to 2 mol / L.
  • a quaternary ammonium salt or a quaternary phosphonium salt having a quaternary ammonium cation or a quaternary phosphonium cation can be used in addition to a salt that generates lithium ions.
  • an electrolytic solution containing a lithium salt and a quaternary ammonium salt improves the rate characteristics of an electrochemical capacitor, although it seems that the solvation structure of the solvent changes to increase the diffusion rate of lithium ions. It is a suitable electrolytic solution.
  • an electrochemical capacitor in which a rapid decrease in discharge capacity when the terminal voltage is reduced is obtained.
  • Example 1 A conductive adhesive layer was formed by applying a composition in which graphite and polyamideimide as a binder were added to water to a predetermined thickness on an aluminum foil.
  • Activated carbon (YP-17 manufactured by Kuraray Chemical Co., Ltd.), ketjen black as a conductive agent, carboxymethoxycellulose as a thickener, and styrene butadiene rubber binder are 10: 1: 0.25: 0.3.
  • the slurry was dispersed in water at a mass ratio of and mixed with a stirrer to obtain a slurry.
  • the obtained slurry was applied to an aluminum foil provided with the above-described conductive adhesive layer containing graphite with a predetermined thickness and dried. Next, the dried sheet was punched out so as to have an area of 3 ⁇ 4 cm 2 and pressed with a roll press to obtain a positive electrode.
  • a binder composition (Hitachi Chemical Co., Ltd.) containing 3.5 g of lithium titanate (LT-109 manufactured by Ishihara Sangyo Co., Ltd., median diameter 6.9 ⁇ m), 1.5 g of carbon nanofiber as a conductive agent, and modified acrylonitrile resin.
  • 4.29 g of LSR-7) manufactured by company and 27 g of N-methylpyrrolidone were mixed with a thin film swirl mixer to obtain a slurry.
  • the obtained slurry was applied to an aluminum foil provided with the above-described conductive adhesive layer containing graphite with a predetermined thickness and dried.
  • the dried sheet was punched out to an area of 3 ⁇ 4 cm 2 and pressed with a roll press to obtain a negative electrode.
  • the positive electrode and the negative electrode were laminated via a cellulose separator, impregnated with a propylene carbonate electrolyte containing 1M LiBF 4 and sealed with an aluminum laminate to obtain an electrochemical capacitor.
  • the thickness of the conductive adhesive layer was set so that the graphite had an initial irreversible capacity of 5.8 mAh with respect to 1 g of lithium titanate.
  • the thicknesses of the positive electrode active material layer and the negative electrode active material layer were set so that the magnification of the 100% discharge capacity of lithium titanate to the 100% discharge capacity of activated carbon was 2.7.
  • the obtained electrochemical capacitor was charged to 2.8 V at a current of 12 mA at room temperature, maintained at 2.8 V for 30 minutes, and charged and discharged twice to discharge to 1.5 V at a current of 12 mA.
  • the discharge capacity of this electrochemical capacitor was 0.95 mAh.
  • Comparative Example 1 The procedure of Example 1 was repeated except that an aluminum foil without a conductive adhesive layer containing graphite was used in the production of the positive electrode. In each charge / discharge cycle, no linear relationship was observed between the terminal voltage and the discharge time, and the discharge capacity decreased rapidly when the terminal voltage was around 1.5V. Further, the discharge capacity of this electrochemical capacitor was 0.85 mAh, which was smaller than the discharge capacity of the capacitor of Example 1.
  • Example 2 Utilization of lithium titanate nanoparticles
  • a conductive adhesive layer was formed by applying a composition in which graphite and polyamideimide as a binder were added to water to a predetermined thickness on an aluminum foil.
  • Activated carbon (YP-17 manufactured by Kuraray Chemical Co., Ltd.), ketjen black as a conductive agent, carboxymethoxycellulose as a thickener, and styrene butadiene rubber binder are 10: 1: 0.25: 0.3.
  • the slurry was dispersed in water at a mass ratio of and mixed with a stirrer to obtain a slurry.
  • the obtained slurry was applied to an aluminum foil provided with the above-described conductive adhesive layer containing graphite with a predetermined thickness and dried. Next, the dried sheet was punched out so as to have an area of 3 ⁇ 4 cm 2 and pressed with a roll press to obtain a positive electrode.
  • Lithium titanate (LT-109 manufactured by Ishihara Sangyo Co., Ltd., median diameter 6.9 ⁇ m) was wet-ground by a bead mill using ethanol as a dispersion medium to obtain nanoparticles having an average particle diameter of 35 nm. The average particle size of the nanoparticles was derived from observation by SEM photographs. 3.5 g of the obtained lithium titanate nanoparticles, 1.5 g of carbon nanofibers as a conductive agent, 4.29 g of a binder composition (LSR-7, manufactured by Hitachi Chemical Co., Ltd.), N A slurry was obtained by mixing 27 g of methylpyrrolidone with a thin film swirling mixer.
  • the obtained slurry was applied to an aluminum foil provided with the above-described conductive adhesive layer containing graphite with a predetermined thickness and dried. Next, the dried sheet was punched out to an area of 3 ⁇ 4 cm 2 and pressed with a roll press to obtain a negative electrode.
  • the positive electrode and the negative electrode were laminated via a cellulose separator, impregnated with a propylene carbonate electrolyte containing 1M LiBF 4 and sealed with an aluminum laminate to obtain an electrochemical capacitor.
  • the magnification of the 100% discharge capacity of lithium titanate with respect to the 100% discharge capacity of activated carbon is adjusted to 2.7.
  • the initial irreversible capacity in charging and discharging of 70 ° C., the initial irreversible capacity due to the activated carbon is 3.35mAh per surface area 1 m 2 of lithium titanate, surface area 1 m 2 of the initial irreversible capacity of lithium titanate due to the graphite Per 1.45 mAh.
  • the obtained electrochemical capacitor was charged at a current of 12 mA to 2.9 V under a condition of 70 ° C., left at 2.9 V for 72 hours, and then subjected to high temperature aging for discharging.
  • the battery was charged to 2.8 V at a current of 12 mA, maintained at 2.8 V for 30 minutes, and charged and discharged twice to discharge to 1.5 V at a current of 12 mA.
  • a decrease in the discharge capacity generated in the vicinity of the terminal voltage of about 1.5 V was not recognized, and a linear relationship was observed between the terminal voltage and the discharge time.
  • the discharge capacity of this electrochemical capacitor was 1.1 mAh.
  • Example 3 Charging to 2.9V at a current of 12mA under the condition of 70 ° C, and leaving it at 2.9V for 72 hours, then charging to 3.0V at a current of 12mA under the condition of 40 ° C instead of high temperature aging to discharge, The procedure of Example 2 was repeated, except that aging was performed after discharging at 3.0 V for 12 hours and then discharging. In each charge / discharge cycle, a decrease in the discharge capacity generated in the vicinity of the terminal voltage of about 1.5 V was not recognized, and a linear relationship was observed between the terminal voltage and the discharge time. The discharge capacity of this electrochemical capacitor was 1.1 mAh.
  • Comparative Example 2 The procedure of Example 2 was repeated except that an aluminum foil without a conductive adhesive layer containing graphite was used in the production of the positive electrode. In each charge / discharge cycle, no linear relationship was observed between the terminal voltage and the discharge time, and the discharge capacity decreased rapidly when the terminal voltage was around 1.5V. Further, the discharge capacity of this electrochemical capacitor was 0.9 mAh, which was smaller than the discharge capacity of the capacitor of Example 2.
  • Example 3 The procedure of Example 3 was repeated except that an aluminum foil without a conductive adhesive layer containing graphite was used in the production of the positive electrode. In each charge / discharge cycle, no linear relationship was observed between the terminal voltage and the discharge time, and the discharge capacity decreased rapidly when the terminal voltage was around 1.5V. Further, the discharge capacity of this electrochemical capacitor was 0.9 mAh, which was smaller than the discharge capacity of the capacitor of Example 3.
  • the electrochemical capacitor provided with the conductive adhesive layer containing graphite on the positive electrode has a capacity retention ratio as compared with the electrochemical capacitor not provided with the conductive adhesive layer containing graphite on the positive electrode. Is high. It can also be seen that the electrochemical capacitor that has been subjected to high temperature aging has a higher capacity retention rate than the electrochemical capacitor that has not been subjected to high temperature aging.
  • the electrochemical capacitor of Example 2 provided with a conductive adhesive layer containing graphite on the positive electrode and subjected to high temperature aging showed a very high capacity retention rate.
  • an electrochemical capacitor having stable capacitor characteristics in which a rapid decrease in the discharge capacity when the terminal voltage is reduced is suppressed.

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  • Microelectronics & Electronic Packaging (AREA)
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Abstract

La présente invention concerne un condensateur électrochimique qui présente une réduction de la décroissance de capacité de décharge qui survient à une tension aux bornes d'environ 1,5V. Ce condensateur électrochimique comporte: une électrode positive qui comprend une couche de matériau actif d'électrode positive contenant du charbon actif; une électrode négative qui comprend une couche de matériau actif d'électrode négative contenant du titanate de lithium du type spinelle; et un séparateur qui est disposé entre la couche de matériau actif d'électrode positive et la couche de matériau actif d'électrode négative et qui retient un électrolyte non aqueux qui contient un sel de lithium. Le condensateur électrochimique est caractérisé en ce que: l'électrode positive contient du graphite et/ou du graphie expansé; et le graphite et/ou le graphite expansé présentent une capacité irréversible initiale de 5,8 mAh ou plus par gramme du titanate de lithium. Cette capacité irréversible initiale due au graphite et/ou au graphite expansé réduit la décroissance de capacité de décharge survenant à une tension aux bornes d'environ 1,5V, de manière que le condensateur présente une relation presque linéaire entre la tension aux bornes et la capacité de décharge ou entre la tension et bornes et le temps de décharge en décharge à courant constant.
PCT/JP2014/071194 2013-08-19 2014-08-11 Condensateur électrochimique WO2015025763A1 (fr)

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EP3477670A4 (fr) * 2016-06-22 2020-07-29 Nippon Chemi-Con Corporation Condensateur hybride et procédé de fabrication de celui-ci

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WO2018043481A1 (fr) * 2016-08-31 2018-03-08 積水化学工業株式会社 Matériau d'électrode pour dispositifs de stockage d'électricité, électrode pour dispositifs de stockage d'électricité, et dispositif de stockage d'électricité

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JP2002270175A (ja) * 2001-03-09 2002-09-20 Asahi Glass Co Ltd 二次電源
JP2013045984A (ja) * 2011-08-26 2013-03-04 Nippon Zeon Co Ltd 蓄電デバイス用電極、蓄電デバイスおよび蓄電デバイス用電極の製造方法
JP2013145761A (ja) * 2013-04-08 2013-07-25 Nippon Zeon Co Ltd 電気化学素子用電極の製造方法

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JP2002289214A (ja) * 2001-03-27 2002-10-04 Nichias Corp 燃料電池用セパレータ

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JP2002270175A (ja) * 2001-03-09 2002-09-20 Asahi Glass Co Ltd 二次電源
JP2013045984A (ja) * 2011-08-26 2013-03-04 Nippon Zeon Co Ltd 蓄電デバイス用電極、蓄電デバイスおよび蓄電デバイス用電極の製造方法
JP2013145761A (ja) * 2013-04-08 2013-07-25 Nippon Zeon Co Ltd 電気化学素子用電極の製造方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3477670A4 (fr) * 2016-06-22 2020-07-29 Nippon Chemi-Con Corporation Condensateur hybride et procédé de fabrication de celui-ci
US11152159B2 (en) 2016-06-22 2021-10-19 Nippon Chemi-Con Corporation Hybrid capacitor and manufacturing method thereof

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