WO2021225107A1 - マンガン／チタン系レドックスフロー電池用炭素電極材 - Google Patents

マンガン／チタン系レドックスフロー電池用炭素電極材 Download PDF

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WO2021225107A1
WO2021225107A1 PCT/JP2021/017008 JP2021017008W WO2021225107A1 WO 2021225107 A1 WO2021225107 A1 WO 2021225107A1 JP 2021017008 W JP2021017008 W JP 2021017008W WO 2021225107 A1 WO2021225107 A1 WO 2021225107A1
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Prior art keywords
carbon
fiber
electrode material
carbonaceous
carbon electrode
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English (en)
French (fr)
Japanese (ja)
Inventor
佳奈 森本
良平 岩原
貴 五十嵐
正幸 大矢
吉恭 川越
康一 橋本
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Sumitomo Electric Industries Ltd
Toyobo Co Ltd
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Sumitomo Electric Industries Ltd
Toyobo Co Ltd
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Priority to JP2022519943A priority Critical patent/JPWO2021225107A1/ja
Publication of WO2021225107A1 publication Critical patent/WO2021225107A1/ja
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/96—Carbon-based electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • 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
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to a carbon electrode material for a negative electrode of a redox flow battery using a manganese / titanium-based electrolytic solution.
  • the redox flow battery mainly includes external tanks 6 and 7 for storing electrolytic solutions (positive electrode electrolytic solution, negative electrode electrolytic solution) and an electrolytic cell EC.
  • electrolytic cell EC In the electrolytic cell EC, an ion exchange membrane 3 is arranged between the opposing current collector plates 1 and 1.
  • the electrolytic solution containing the active material is sent from the external tanks 6 and 7 to the electrolytic cell EC by the pumps 8 and 9, and the electrochemical energy conversion is performed on the electrode material 5 incorporated in the electrolytic cell EC. That is, charging and discharging are performed.
  • Patent Document 1 uses manganese as an active material for the positive electrode and chromium, vanadium, and titanium as active materials for the negative electrode.
  • a manganese / titanium-based electrolytic solution using the containing electrolytic solution has been proposed.
  • Redox flow batteries using a manganese / titanium-based electrolyte (hereinafter sometimes referred to as "Mn-Ti-based redox flow batteries”) are required to reduce resistance.
  • the present invention has been made in view of the above circumstances, and provides a carbon electrode material for the negative electrode of a Mn—Ti-based redox flow battery capable of reducing cell resistance during initial charge and discharge and improving battery energy efficiency.
  • the purpose is to be described in detail below.
  • the carbon electrode material for the negative electrode of the Mn—Ti-based redox flow battery according to the present invention has the following constitution.
  • the carbon electrode material for the negative electrode of the redox flow battery using the manganese / titanium-based electrolytic solution of the present invention includes a fiber structure formed of a carbonaceous fiber (A) and a carbonaceous material (the fiber structure). It is composed of carbon particles (B) bonded in C) (excluding graphite particles, the same applies hereinafter), and satisfies the following requirements.
  • the average curvature R of the carbonaceous fiber (A) is R1 mm -1 or more, and the amount of the carbonaceous fiber (A) in the fiber structure is 40 g / m 2 or more.
  • the crystallite size Lc (B) in the c-axis direction determined by X-ray diffraction is 10 nm or less.
  • the carbonaceous material (C) has a peak intensity ID of 1360 cm -1 determined by laser Raman spectroscopy.
  • 1580 cm -1 peak intensity ratio Rc (ID / IG) to IG is 1.1 or more
  • 1360 cm -1 peak intensity ID obtained by laser Raman spectroscopy of the carbonaceous fiber (A).
  • the peak intensity ratio Rac (Rc / Ra) of the peak intensity ratio Ra (ID / IG) of the peak intensity IG of 1580 cm -1 and the peak intensity ratio Rc of the carbonaceous material (C) is 1.0 or less ( 5)
  • the carbon electrode material has a BET specific surface area of 30 m 2 / g or more of the mesopores determined from the amount of adsorbed nitrogen gas.
  • Roc (O / C) of carbon atom number C is 1.0% or more
  • the carbon electrode material of the present invention has the following configuration as a preferred embodiment.
  • the present invention also includes a method for producing a carbon electrode material.
  • the gist is to include, in this order, a secondary oxidation step of oxidizing the obtained graphitized product under a dry method at a temperature of 500 to 900 ° C.
  • the carbon electrode material of the present invention is used for the negative electrode, the cell resistance at the time of initial charge / discharge of the Mn—Ti redox flow battery can be reduced and the battery energy efficiency can be improved. Further, the carbon electrode material of the present invention is also excellent in handling at the time of scale-up.
  • FIG. 1 is a schematic view of a redox flow battery.
  • FIG. 2 is an exploded perspective view of a liquid flow type electrolytic cell having a three-dimensional electrode preferably used in the present invention.
  • FIG. 3 shows No. 3 in Table 3. 5 (an example satisfying the requirements of the present invention) is an SEM photograph (magnification 100 times).
  • FIG. 4 shows the No. 1 in Table 3. 10 (comparative example not satisfying the requirements of the present invention) SEM photograph (magnification 100 times).
  • the present invention is a carbon electrode material used for the negative electrode of a Mn—Ti-based redox flow battery.
  • the carbon electrode material of the present invention includes a fiber structure formed of a carbonaceous fiber (A) and carbon particles (B) bonded to the fiber structure with a carbonaceous material (C) (however, graphite particles are excluded. , The same applies hereinafter), and the gist is to satisfy all of the following requirements (1) to (6). The above effect can be achieved by satisfying all the requirements (1) to (6).
  • the average curvature R of the carbonaceous fiber (A) is 1 mm -1 or more, and the grain amount of the carbonic fiber is 40 g / m 2 or more.
  • the carbon particles (B) are obtained by X-ray diffraction. was size Lc in the c-axis direction of the crystallite (B) is 10nm or less (3) the carbonaceous material (C) is the peak intensity of the peak intensity ID and 1580 cm -1 in 1360 cm -1 as determined by laser Raman spectroscopy peak intensity ratio Rc of the IG (ID / IG) is 1.1 or more (4) the carbonaceous fibers (a) a laser Raman spectroscopy by the determined peak 1360 cm -1 strength ID and peak 1580 cm -1 The peak intensity ratio Rac (Rc / Ra) of the peak intensity ratio Ra (ID / IG) of the intensity IG and the peak intensity ratio Rc of the carbonaceous material (C) is 1.0 or less.
  • the BET specific surface area of the mesopores determined from the amount of nitrogen gas adsorbed is 30 m 2 / g or more.
  • the carbon electrode material of the present invention will be described with (O / C) of 1.0%
  • the average curvature of the carbonic fiber (A) is R1 mm -1 or more, and the basis weight of the carbonic fiber is 40 g / m 2 or more.
  • a carbon fiber (A) of a fiber structure formed from a plurality of carbon fibers (A) (hereinafter, may be referred to as a "fiber structure") (that is, a carbon fiber (A) forming the fiber structure. ))
  • a fiber structure that is, a carbon fiber (A) forming the fiber structure.
  • the reaction activity is improved and the resistance is reduced.
  • the shape can be maintained by the entanglement of the fibers, so that the flexibility is high and the number of fibers in the thickness direction is large.
  • the basis weight of the fiber structure is 40 g / m 2 or more.
  • the basis weight is preferably 40 g / m 2 or more, more preferably 50 g / m 2 or more, preferably 100 g / m 2 or less, and more preferably 80 g / m 2 or less.
  • the method for measuring the mean curvature R is based on the description of the examples.
  • the carbonic fiber constituting the structure exists in a curved or crimped state.
  • a structure formed of carbonaceous fibers having an average curvature R of 1 mm -1 or more is thick when the cross section in the thickness direction (cross section perpendicular to the fiber length direction) of the structure is observed with a scanning electron microscope. It also has a three-dimensional structure that allows the longitudinal direction of the fibers to be confirmed in the vertical direction.
  • the mean curvature R is preferably 5 mm -1 or more, more preferably 10 mm -1 or more. Considering the defibration of the fiber, the mean curvature R is preferably 200 mm -1 or less.
  • Carbonous fiber (A) The carbonaceous fiber (A) of the present invention is preferably a carbonized fiber in which a mass ratio of 90% or more is composed of carbon. Specifically, it is defined as "carbon fiber” in JIS L 0204-2: 2010, and is a fiber in which 90% or more of the mass ratio obtained by heat-carbonizing an organic fiber precursor is composed of carbon. be.
  • organic fiber precursor examples include acrylic fibers such as polyacrylonitrile; phenol fibers; PBO fibers such as polyparaphenylene benzobisoxazole (PBO); aromatic polyamide fibers; isotropic pitch, anisotropic pitch fibers, and mesophase.
  • Pitch fibers such as pitch; cellulose fibers; etc. are exemplified.
  • acrylic fibers, phenol fibers, cellulose fibers, isotropic pitch fibers, anisotropic pitch fibers, and more preferably acrylic fibers are preferable in consideration of oxidation resistance, strength, and elastic modulus.
  • the raw materials may be used alone or in admixture of two or more.
  • the main component is 95% by mass or more, more preferably 98% by mass or more of the fiber raw material as the main component in the total amount of the raw material monomers of 100% by mass.
  • acrylic fiber contains acrylonitrile as a main component, and when combined with any other fiber raw material, the content of acrylonitrile in the raw material monomer forming the acrylic fiber is preferably 95% by mass or more, more preferably 98% by mass or more. be.
  • the mass average molecular weight of the organic fiber is not particularly limited, and is preferably 10,000 or more, more preferably 15,000 or more, still more preferably 20,000 or more, preferably 100,000 or less, and more preferably 80. It is 000 or less, more preferably 50,000 or less.
  • the mass average molecular weight can be measured by a method such as gel permeation chromatography (GPC) or solution viscosity.
  • the average fiber diameter of the carbonaceous fiber (A) of the present invention is preferably 0.5 ⁇ m or more, more preferably 3 ⁇ m or more, preferably 40 ⁇ m or less, and more preferably 20 ⁇ m or less.
  • the average fiber length of the carbonic fiber (A) of the present invention is preferably 30 mm or more, more preferably 40 mm or more, further preferably 50 mm or more, preferably 100 mm or less, and more preferably 80 mm or less.
  • the fiber structure of the present invention is, for example, a spun yarn, a filament-focused yarn, a non-woven fabric, a knitted fabric, a woven fabric, which is a sheet-like material composed of a carbonaceous fiber (A), and a special one described in JP-A-63-240177. Examples include knitted fabrics, spunlaces, mariflees, and felts.
  • a non-woven fabric, felt, knitted fabric, woven fabric, and special woven knitted fabric made of the carbonaceous fiber (A) are preferable from the viewpoints of handling, processability, manufacturability, and the like. More preferably, it is a non-woven fabric.
  • the non-woven fabric include spunbonded non-woven fabric, spunlaced non-woven fabric, needle punched non-woven fabric, resin-bonded non-woven fabric, and thermal-bonded non-woven fabric.
  • the carbon electrode material When a fiber structure that does not satisfy the above requirement (1) is used for the carbon electrode material, if the charging liquid is reduced to about half of the initial filling amount, the carbonaceous fibers constituting the carbon electrode material may collapse due to oxidative deterioration. The morphology cannot be maintained. Therefore, the space formed by the carbon electrode material disappears, and the liquid flowability in the cell is remarkably deteriorated. As a result, the battery performance is significantly deteriorated.
  • the fiber structure is formed of carbonaceous fibers having an average curvature R of less than R1 mm-1, there is no longitudinal direction of the fibers in the thickness direction, and the fibers are oriented only in the fiber length direction.
  • the body Papers such as carbon paper are exemplified as an example in which the average curvature R of the carbonaceous fiber is less than 1 mm -1. Paper is a two-dimensional structure in which linear carbonaceous fibers are connected and are oriented in the same direction. For example, the fiber structure formed from papermaking uses chopped fibers cut to a predetermined length, so the average curvature R is 0 mm -1 .
  • the papermaking since the papermaking is adhered to each other with polyvinyl alcohol or the like, it becomes a hard structure, and when it is formed into a roll shape, it breaks or breaks. Further, in the fiber structure formed from papermaking, if the basis weight is reduced, it can be handled in a roll shape, but it becomes difficult to increase the amount of carbon particles (B) and carbonaceous material (C) supported.
  • the Mn—Ti-based redox flow battery has low reactivity of titanium ions in the negative electrode, and it is necessary to increase the amount carried in order to reduce the resistance. However, since the fiber structure formed from papermaking has a small number of fibers in the thickness direction and a low loading amount, for example, two or more fibers are required per cell. Therefore, the manufacturing cost is high.
  • the size Lc (B) of crystallites in the c-axis direction obtained by X-ray diffraction of carbon particles (B) is 10 nm or less.
  • the lower limit of the crystallite size Lc (B) of the carbon particles (B) is not limited.
  • the lower limit may be set in consideration of the oxidation resistance of the carbon particles (B) to the electrolytic solution.
  • the crystallite size Lc (B) of the carbon particles (B) is preferably 6 nm or less, more preferably 4 nm or less, preferably 0.5 nm or more, and more preferably 1.0 nm or more.
  • the size of the crystallite Lc (B) is measured based on the conditions of the examples.
  • Particle size of carbon particles (B) It is also preferable to adjust the particle size of the carbon particles (B) of the present invention.
  • the particle size of the carbon particles (B) is preferably 1 ⁇ m or less, more preferably 0.5 ⁇ m or less, still more preferably 0.3 ⁇ m or less, preferably 0.005 ⁇ m or more, and more preferably 0.01 ⁇ m or more.
  • the particle size of the carbon particles (B) is the average particle size (D50) at a median 50% diameter in the particle size distribution measured by the dynamic light scattering method.
  • the carbon particles (B) may be a commercially available product, and the value described in the catalog can be adopted as the particle size when the commercially available product is used.
  • BET specific surface area of carbon particles (B) It is also preferable to appropriately adjust the BET specific surface area of carbon particles (B). For example, if the BET specific surface area is too small, the exposure of the edge surface of the carbon particles (B) is reduced, the contact area with the electrolytic solution is reduced, and the resistance may not be sufficiently reduced. Further, for example, when bulky carbon particles (B) having an excessively large BET specific surface area are used, the viscosity of the dispersion solution tends to increase, and the processability into a sheet or the like may deteriorate.
  • the BET specific surface area of the carbon particles (B) is preferably 20 m 2 / g or more, more preferably 30 m 2 / g or more, still more preferably 40 m 2 / g or more, preferably 2000 m 2 / g or less, more preferably. It is 1800 m 2 / g or less, more preferably 1500 m 2 / g or less.
  • the BET specific surface area of the carbon particles (B) is calculated from the amount of nitrogen adsorbed, that is, the amount of gas molecules adsorbed by adsorbing nitrogen molecules on solid particles.
  • Carbon particles (B) are carbon particles other than graphite particles. As already mentioned, the "carbon particles (B)" of the present invention do not include graphite particles.
  • the carbon particles (B) are reactive, for example, carbon blacks such as acetylene black (acetylene soot), oil black (furness black, oil soot), ketjen black, and gas black (gas soot). And carbon particles having a high specific surface area and low crystallinity are preferable.
  • carbon particles (B), carbon nanotubes (CNT, carbon nanotube), carbon nanofibers, carbon aerogel, mesoporous carbon, graphene, graphene oxide, N-doped CNT, boron-doped CNT, fullerene and the like may be used. Considering the raw material price, carbon blacks are preferable.
  • Carbonaceous material (C) used in the present invention is a binder that binds carbonaceous fibers (A) (that is, carbon fibers (A) forming a fiber structure) and carbon particles (B). Is.
  • a carbonaceous material (C) that satisfies both the following requirements (3) and (4), the electron conduction resistance between the carbon particles (B) and the carbonaceous fiber (A) becomes low.
  • the electron conduction path between the carbon particles (B) and the carbonaceous fibers (A) is improved.
  • the carbonaceous material (C) enhances the binding property between the carbonaceous fibers (A) via the carbon particles (B).
  • the binding property By improving the binding property, an efficient conductive path can be formed, and the low resistance effect of the carbon particles (B) can be more effectively exhibited. Further, when the highly crystalline carbonaceous material (C) is used, the mesopore volume of the carbon electrode material can be increased, and as a result, the resistance can be significantly reduced.
  • the carbonaceous material (C) is a peak intensity ID of 1360 cm -1 as determined by laser Raman spectroscopy, the peak intensity ratio Rc (ID / IG) of a peak intensity IG of 1580 cm -1 1.1 or more peaks
  • the peak intensity ratio Rc (ID / IG) is preferably 1.2 or more.
  • the upper limit of the peak intensity ratio Rc (ID / IG) is not limited. For example, considering the electron conductivity, it is preferably 3.0 or less.
  • Peak intensity ratio Rac (Rc / Ra) with peak intensity ratio Rc of C is 1.0 or less Peak intensity ratio Ra (ID / IG) of carbonic fiber (A) and peak intensity of carbonaceous material (C) If the peak intensity ratio Rac (Rc / Ra) with the ratio Rc exceeds 1.0, the above effect cannot be obtained.
  • the peak intensity ratio Rac (Rc / Ra) is preferably 0.9 or less, more preferably 0.8 or less.
  • the lower limit is not particularly limited, but is preferably 0.1 or more, more preferably 0.3 or more, in consideration of the imparting property of the oxygen functional group to the carbonaceous material (C).
  • the peak intensity ratio Ra is preferably 1.2 or more, more preferably 1.4 or more, considering the property of imparting an oxygen functional group to the carbonic fiber (A).
  • Peak intensity ratio Rc (ID / IG) of carbonaceous material (C) is not particularly limited as long as the peak intensity ratio Rac (Rc / Ra) is in the above range. From the viewpoint of further reducing the resistance, the peak intensity ratio Rc is preferably 1.1 or more, more preferably 1.3 or more. The lower limit of the peak intensity ratio Rc is not particularly limited from the above viewpoint, but is preferably 3.0 or less in consideration of electron conductivity, oxidation resistance, easiness of imparting an oxygen functional group, and the like.
  • Peak intensity ratio Ra (ID / IG) of carbonaceous fiber (A) The peak intensity ratio Ra of the carbonic fiber (A) is not particularly limited, but if appropriately controlled, effects such as good electron conductivity, oxidation resistance to a sulfuric acid solvent, and easy addition of an oxygen functional group can be obtained.
  • the peak intensity ratio Ra is preferably 1.2 or more, more preferably 1.4 or more, preferably 2.0 or less, and more preferably 1.8 or less.
  • the carbonaceous fiber (A) is coated with the carbonaceous material (C), and at least a part of the surface of the carbon particles (B) is coated with the carbonaceous material (C). It is preferably in an unexposed state. Further, it is preferable that the carbonaceous material (C) after binding is not in a film state.
  • the fact that the carbonaceous material (C) is not in a film state means that the carbonic material (C) does not form a webbed state such as a whole foot (boxoku) or a foot. To say.
  • the carbonaceous material (C) is in a film state, the liquid permeability of the electrolytic solution deteriorates and the reaction surface area of the carbon particles (B) cannot be effectively used.
  • FIG. 3 shows a state in which the carbon fiber (A) and the carbon particles (B) constituting the carbon electrode material of the present invention are bound by the carbon material (C).
  • FIG. 3 it can be seen that the surface of the carbon particles (B) is exposed while the carbon fiber (A) is covered with the carbon material (C).
  • FIG. 4 shows a state in which the carbonaceous fiber (A) and the carbon particles (B) are not bound.
  • the carbonaceous material (C) used in the present invention may be any material that can obtain the above-mentioned binding effect.
  • pitches such as coal tar pitch and coal pitch; benzoxazine resin, epoxide resin, furan resin, vinyl ester resin, melanin-formaldehyde resin, urea-formaldehyde resin, resorcinol-formaldehyde resin, cyanate ester resin, bismaleimide resin.
  • Polyurethane resin resin such as polyacrylonitrile; furfuryl alcohol; rubber such as acrylonitrile-butadiene rubber and the like.
  • a commercially available product may be used as the carbonaceous material (C).
  • pitches such as coal tar pitch and coal-based pitch, which are particularly easily crystalline, are preferable because the desired carbonaceous material (C) can be obtained at a low firing temperature. Further, the polyacrylonitrile resin is also preferable because a desired carbonaceous material (C) can be obtained by raising the firing temperature. Of these, pitches are more preferable.
  • the content rate of the mesophase phase can be controlled by the temperature and time of the infusibilization treatment. If the content of the mesophase phase is low, a carbonaceous material (C) that melts at a relatively low temperature or is in a liquid state at room temperature can be obtained. On the other hand, if the content of the mesophase phase is high, it melts at a high temperature and a carbonic material having a high carbonization yield can be obtained.
  • the pitches applied to the carbonaceous material (C) preferably have a high content of the mesophase phase, that is, a high carbonization rate.
  • the mesophase phase content is preferably 30% or more, more preferably 50% or more.
  • the fluidity at the time of melting is suppressed and the surface of the carbon particles (B) is not excessively coated, and the carbonic fibers (B) are interposed through the carbon particles (B).
  • the mesophase phase content is preferably 90% or less.
  • the melting point of the pitches is preferably 100 ° C. or higher, more preferably 200 ° C. or higher, and preferably 350 ° C. or lower. Is.
  • phenol resin for the carbonaceous material (C) of the present invention.
  • the use of phenolic resin has disadvantages in terms of cost and work, such as the generation of formaldehyde and the need to control the formaldehyde concentration during manufacturing.
  • the carbon particles (B) and the carbon fibers (A) can be bound by the carbon material (C).
  • the carbon electrode material (C) not only has an efficient conductive path, but also can achieve low resistance and high oxidation resistance due to the carbon particles (B).
  • (C / (A + B + C)) is preferably 14.5% or more, more preferably 15% or more, still more preferably 17% or more, still more preferably 30% or more, preferably 90% or less, more preferably. Is 80% or less, more preferably 70% or less.
  • Content of carbon particles (B) It is also preferable to appropriately adjust the content of carbon particles (B) in the carbon electrode material of the present invention. If the content of carbon particles (B) is increased, the effect of reducing resistance can be obtained, but if it is too large, the binding by the carbonaceous material (C) becomes insufficient and the carbon particles (B) may fall off. Further, if the number of carbon particles (B) is too large, the liquid permeability may deteriorate and the resistance may increase. In the present invention, since the mesopore ratio is high, a desired low resistance can be achieved even if the ratio of carbon particles (B) is low.
  • the mass ratio of the carbon particles (B) to the total amount of the carbon fibers (A) (that is, the carbon fibers (A) forming the fiber structure), the carbon particles (B), and the carbon material (C) ( B / (A + B + C)) is preferably 5% or more, more preferably 10% or more, still more preferably 15% or more, still more preferably 20% or more, preferably 90% or less, more preferably 80%. Below, it is more preferably 70% or less, still more preferably 60% or less.
  • Mass ratio of carbon particles (B) and carbonaceous material (C) it is also preferable to adjust the mass ratio of carbon particles (B) and carbonaceous material (C). By adjusting these mass ratios, the carbon particles (B) can be suppressed from falling off, and the oxidation resistance can be further improved. Further, the coating of the carbon edge surface of the carbon particles (B) can be suppressed, and the resistance can be further reduced.
  • the mass ratio (C / B) of the carbonaceous material (C) to the carbon particles (B) is preferably 0.2 or more, more preferably 0.3 or more, still more preferably 0.5 or more, and preferably 0.5 or more. It is 10.0 or less, more preferably 7.0 or less, still more preferably 6.5 or less.
  • Total content of carbon particles (B) and carbonaceous material (C) in the present invention, it is also preferable to adjust the total content of carbon particles (B) and carbonaceous material (C). By adjusting the total content of these, the amount of carbon particles (B) supported can be increased, which contributes to lowering the resistance.
  • the total mass ratio ((B + C) / (A + B + C)) of the carbon particles (B) and the carbon material (C) to the total amount of the carbon fiber (A), the carbon particles (B), and the carbon material (C) is It is preferably 20% or more, more preferably 40% or more, further preferably 50% or more, preferably 70% or less, and more preferably 65% or less.
  • the carbonaceous material is also used in Patent Document 1, there is only a partial adhesive action of fixing (adhering) only the contact portion between the carbonaceous fiber and the carbon fine particles. Therefore, the binder content of the carbon electrode material of the example is about 14.4% by mass.
  • Carbon electrode material The carbon electrode material of the present invention satisfies the following requirements (5) and (6).
  • the carbon electrode material has a BET specific surface area of mesopores of 30 m 2 / g or more, which is determined from the amount of nitrogen gas adsorbed. When it is 2 / g or more, the contact area with the electrolytic solution increases and the cell resistance can be remarkably reduced.
  • the BET specific surface area of the mesopores is preferably 40 m 2 / g or more, 60 m 2 / g or more, 100 m 2 / g or more, 150 m 2 / g or more, and 180 m 2 / g or more in this order.
  • the upper limit is not limited, it is preferably 300 m 2 / g or less, more preferably, in consideration of good conductive path formation between the carbon particles (B) and improvement of the adhesiveness of the carbon particles (B) to the carbon fiber (A). Is 240 m 2 / g or less.
  • the BET specific surface area of the mesopores is according to the method described in Examples.
  • the ratio Roc (O / C) of the number of bonded oxygen atoms O on the surface of the carbon electrode material to the total number of carbon atoms C on the surface of the carbon electrode material is 1.0% or more, and the number of bonded oxygen atoms O on the surface of the carbon electrode material.
  • the electrode reaction rate can be significantly improved and the resistance can be reduced.
  • the hydrophilicity of the carbon electrode material is improved, and a good water flow rate can be ensured.
  • the ratio Roc (O / C) of the number of bonded oxygen atoms O and the total number of carbon atoms C on the surface of the carbon electrode material is 1.0% or more
  • the oxygen atoms introduced into the carbon edge surface or the defect structure are carbonyl groups.
  • the ratio Roc of the number of bonded oxygen atoms O to the total number of carbon atoms C is preferably 2.0% or more, more preferably 3.0% or more, further preferably 4.0% or more, and preferably 15% or less. It is more preferably 10% or less, still more preferably 8.0% or less.
  • the number of bonded oxygen atoms O and the total number of carbon atoms C on the surface of the carbon electrode material are according to the methods described in the examples.
  • the BET specific surface area of carbon electrode material It is also preferable to adjust the BET specific surface area of the carbon electrode material of the present invention. Increasing the BET specific surface area of the carbon electrode material increases the exposure of the edge surface of the carbon particles (B) and also increases the contact area with the electrolytic solution, which contributes to the reduction of resistance. Since such an effect can be obtained as the BET specific surface area increases, the upper limit is not limited. For example, an upper limit may be set in consideration of forming a good conductive path between the carbon particles (B) and the adhesiveness of the carbon particles (B) to the carbon fiber (A).
  • the BET specific surface area of the carbon electrode material is preferably 40 m 2 / g or more, more preferably 60 m 2 / g or more, and preferably 500 m 2 / g or less.
  • the carbon electrode material of the present invention has excellent hydrophilicity.
  • the water flow rate may be increased from the viewpoint of ensuring sufficient affinity for the electrolytic solution.
  • the water flow rate is preferably 0.5 mm / sec or more, 1 mm / sec or more, 5 mm / sec or more, and 10 mm / sec or more in that order.
  • the water flow rate can be adjusted by appropriately adjusting the above requirements of the carbon electrode material.
  • the water flow rate is the rate at which water droplets are dropped on the surface of the carbon electrode material that has been subjected to the dry oxidation treatment, and the water droplets reach the back surface of the carbon electrode material.
  • the basis weight of the carbon electrode material is preferably 50 g / m 2 or more, more preferably 100 g / m 2 or more, preferably 500 g / m 2 or less, and more preferably 400 g / m 2 or less.
  • the basis weight of the carbon electrode material is the total basis weight of the fiber structure, the carbonaceous material (C), and the carbon particles (B).
  • the ion exchange membrane tends to be thinned in order to reduce resistance and is easily damaged.
  • the carbon electrode of the present invention having the above-mentioned grain amount can prevent damage to the ion exchange membrane while ensuring liquid permeability.
  • the carbon electrode material of the present invention is made of a non-woven fabric or paper having a flat surface processed on one side as a base material. For the flattening process, a method of applying the slurry to one side of the carbonaceous fiber and drying it; various known methods such as impregnation and drying on a smooth film such as PET can be adopted.
  • Thickness of carbon electrode material It is also preferable to appropriately adjust the thickness of the carbon electrode material.
  • the thickness of the carbon electrode material is preferably larger than the spacer thickness, and is preferably 1.5 to 6.0 times the spacer thickness.
  • the compressive stress of the carbon electrode material is preferably 9.8 N / cm 2 or less.
  • the compressive stress may be adjusted by changing the basis weight and thickness of the carbon electrode material. Further, the compressive stress may be adjusted by forming the carbon electrode material into a laminated structure such as, for example, two layers or three layers, or by combining the carbon electrode material with another form of the carbon electrode material.
  • the carbon electrode material of the present invention is used for the negative electrode of a Mn—Ti-based redox flow battery.
  • an electrode material used for an Mn—Ti-based redox flow battery such as an electrode material using a carbon fiber non-woven fabric or the like, can be used.
  • a carbon electrode material having the same composition as the carbon electrode material for the negative electrode of the present invention, or a carbon electrode material appropriately adjusted within the range of the present invention may be used. If it is used for a short period of time, for example, if the charge / discharge test is performed for about 3 hours as shown in Examples, the cell resistance reduction effect at the time of initialization charge / discharge can be confirmed by using the carbon electrode material of the present invention for the positive electrode.
  • a positive electrode having oxidation resistance for example, polyacrylonitrile-based carbon fiber felt fired at 2000 ° C. or higher, may be used as the positive electrode in order to suppress electrode decomposition due to the oxidizing power of Mn. preferable.
  • FIG. 2 shows an example of a liquid flow type electrolytic cell using the carbon electrode material of the present invention.
  • an ion exchange membrane 3 is arranged between two opposing current collector plates 1, 1, and an electrolytic solution along the inner surface of the current collector plates 1, 1 is provided by spacers 2 on both sides of the ion exchange membrane 3.
  • the liquid passages 4a and 4b are formed.
  • the electrode material 5 is arranged in at least one of the liquid passages 4a and 4b.
  • the current collector plate 1 is provided with a liquid inlet 10 and a liquid outlet 11 for the electrolytic solution.
  • the electrode is composed of the electrode material 5 and the current collector plate 1, and the structure is such that the electrolytic solution passes through the electrode material 5 (three-dimensional electrode structure).
  • the charge / discharge efficiency can be improved by using the entire surface of the pores of the electrode material 5 as an electrochemical reaction field while ensuring transportation. As a result, the charging / discharging efficiency of the electrolytic cell is improved.
  • carbon particles (B) and a carbon material (C) before carbonization (hereinafter, may be referred to as "carbon material precursor") are used as a base material.
  • adhering step After adhering to the structure composed of the fiber (A) or its precursor (hereinafter, may be referred to as "adhering step"), the carbonization step, the primary oxidation step, the graphitization step, and the secondary oxidation step are carried out in this order. It has a gist to include in. Unless otherwise specified, known methods and manufacturing conditions can be appropriately applied to each step.
  • the carbonaceous fiber (A) may be appropriately selected from the various materials described above.
  • the above-mentioned "heat carbonization treatment" of the carbonaceous fiber (A) preferably includes at least a flame resistance step and a carbonization step. The order of the flame resistance process and the carbonization process does not matter. Further, the carbonization step after the flame resistance may be omitted, and the carbonized fiber (A) may be carbonized in the carbonization step after being treated in the attachment step.
  • the flame-resistant process is a process of heating an organic fiber precursor in an air atmosphere to obtain a flame-resistant organic fiber.
  • the heat treatment temperature is appropriately set, the content of nitrogen and hydrogen in the organic fiber can be reduced and the carbonization rate can be improved while preventing the thermal decomposition of the organic fiber and maintaining the form of the carbonic fiber.
  • the heat treatment temperature is preferably 180 ° C. or higher, more preferably 190 ° C. or higher, still more preferably 200 ° C. or higher, preferably 350 ° C. or lower, more preferably 330 ° C. or lower, still more preferably 300 ° C. or lower.
  • the organic fiber In the flame resistance process, if the organic fiber is heat-treated in a relaxed state, it may heat shrink and the molecular orientation may collapse, resulting in a decrease in the conductivity of the carbonic fiber.
  • the organic fiber In order to prevent a decrease in conductivity, the organic fiber is preferably flame-resistant under tension or stretching, and more preferably flame-resistant under tension.
  • the carbonization step is a step of heating the obtained flame-resistant organic fiber in an inert atmosphere, preferably in a nitrogen atmosphere to obtain carbonic fiber.
  • the heating temperature is preferably 1000 ° C. or higher, more preferably 1100 ° C. or higher, still more preferably 1200 ° C. or higher, preferably 2000 ° C. or lower, and more preferably 1900 ° C. or lower.
  • the heating temperature in the carbonization step can be selected according to the type of the organic fiber used as a raw material.
  • the heating temperature is preferably 800 ° C. or higher, more preferably 1000 ° C. or higher, preferably 2000 ° C. or lower, more preferably 1800 ° C. or lower. be.
  • the flame resistance step and the carbonization step are continuously performed.
  • the rate of temperature rise is preferably 20 ° C./min or less, more preferably 15 ° C./min or less, and preferably 5 ° C./min or more.
  • the fiber structure is a precursor of a carbonaceous fiber structure, for example, a non-woven fabric that has been heat-carbonized.
  • the precursor of the structure of the carbonaceous fiber is formed by using the above carbonaceous fiber.
  • the method for forming the precursor of the fiber structure is not particularly limited. For example, when forming a non-woven fabric, known manufacturing methods such as entanglement, fusion, and adhesion can be adopted.
  • the above fiber structure is used as a base material for a carbon electrode material.
  • the use of the fiber structure improves the strength and facilitates handling and workability.
  • the carbon particles (B) and the carbonaceous material (C) may be appropriately selected from the above-mentioned various materials.
  • Adhesion step is a step of adhering the carbon particles (B) and the precursor of the carbonaceous material (C) to the carbonaceous fiber (A).
  • Various known methods can be adopted as a method for adhering the carbon particles (B) and the precursor of the carbonaceous material (C) to the carbonaceous fiber (A) structure or its precursor.
  • a suitable bonding method is to disperse the precursor of the carbonaceous material (C) and the carbon particles (B) in a solvent such as water or alcohol to which a binder that disappears during carbonization, such as polyvinyl alcohol, is added as a temporary adhesive. This is a method in which the structure of the carbonic fiber (A) is immersed in the dispersion liquid, and then heated and dried.
  • the precursor of the carbonaceous material (C) is heated and melted, and carbon particles (B) are dispersed in the obtained melt to prepare a melt dispersion, and carbon fibers are added to the melt dispersion.
  • An example is a method of cooling to room temperature after immersion.
  • the excess melt dispersion liquid or dispersion liquid (hereinafter referred to as “surplus dispersion liquid”) is passed through a nip roller provided with a predetermined clearance. It is desirable to squeeze the excess dispersion liquid to remove it from the structure, or to scrape the surface of the excess dispersion liquid with a doctor blade or the like to remove it from the structure.
  • the structure of the carbonaceous fiber (A) impregnated with the obtained carbon particles (B) and the precursor of the carbonaceous material (C) (hereinafter, referred to as “adhesive material”) is produced in an air atmosphere, for example, from 80 to 80. It is desirable to dry at 150 ° C.
  • Carbonization step is a step of calcining an adhering material to obtain a carbonized product.
  • the carbon particles (B) are bound to the carbonaceous fibers (A).
  • the carbonization conditions are as follows. Atmosphere: Inactive atmosphere, preferably nitrogen atmosphere Heating temperature: 600 ° C. or higher, more preferably 800 ° C. or higher, further preferably 1000 ° C. or higher, even more preferably 1200 ° C. or higher, 1400 ° C. or lower, preferably 1300 ° C. Below, more preferably 1200 ° C. or less
  • the heating time is preferably 1 hour or more and 2 hours or less.
  • the carbonization step may be performed after the flame resistance step of the precursor of the carbonaceous fiber (method 1 below), or the carbon after the flame resistance step of the precursor of the carbonaceous fiber (A) structure.
  • the conversion step may be omitted (method 2 below).
  • the carbonic fiber (A) structure is attached.
  • the precursor of the carbonaceous fiber (A) structure is attached.
  • Method 1 Flame resistance of the precursor of the carbon fiber structure ⁇ Carbonization step ⁇ Adhesion step ⁇ Carbonization step ⁇ Primary oxidation step ⁇ Graphitization step ⁇ Secondary oxidation step
  • Method 2 Carbon fiber (A) structure Flame resistance step of precursor ⁇ Adhesion step ⁇ Carbonization step ⁇ Primary oxidation step ⁇ Graphitization step ⁇ Secondary oxidation step
  • the above method 1 is costly because the carbonization step is performed twice, but the difference in volume shrinkage ratio. Is small and is advantageous for suppressing deformation of the carbon electrode material such as warpage.
  • the above method 2 is low in cost because the carbonization step is performed once, but the difference in volume shrinkage ratio is larger than that of the above method 1, and it is inferior in terms of deformation suppression.
  • the primary oxidation step is a step of oxidizing a carbonized product to obtain a primary oxide. Oxidation of the carbonized material activates the carbonaceous fibers (A) and removes the carbonaceous material (C) to expose at least a portion of the surface of the carbon particles (B). As a result, the mesopore specific surface area of the carbon electrode material can be remarkably increased, so that the reactivity is improved and the resistance is reduced.
  • the primary oxidation treatment of the carbonized product is performed under a dry method.
  • the atmosphere of the primary oxidation treatment is an oxidizing atmosphere, preferably an air atmosphere.
  • the heating temperature of the primary oxidation treatment is 500 ° C. or higher, preferably 550 ° C. or higher, 900 ° C. or lower, preferably 800 ° C. or lower, and more preferably 750 ° C. or lower.
  • the heating time is preferably 5 minutes or more and 1 hour or less.
  • the specific surface area of the carbon electrode material can be increased, and the reduction or maintenance of mechanical strength can be suppressed or maintained.
  • the yield of the primary oxidation step (the ratio of the carbonized product after the primary oxidation treatment liquid, that is, the mass of the primary oxide to the mass of the carbonized material before the primary oxidation treatment) is preferably 85% or more, more preferably 95% or more. It is desirable to control the processing conditions so as to be.
  • the carbonized product to be subjected to the primary oxidation treatment has low crystallinity and a high oxidation rate, it is preferable to treat it at a lower heating temperature than the secondary oxidation treatment.
  • the graphitization step is a step of further heating the primary oxide to obtain a graphitized product.
  • the graphitization step is preferably carried out by further heating after the primary oxidation step.
  • the preferred conditions for the graphitization treatment are as follows. Appropriate control of the graphitization process can improve the affinity of the electrolyte.
  • Atmosphere Inactive atmosphere, preferably nitrogen atmosphere
  • Heating temperature Higher than the heating temperature of the carbonization step, preferably 1300 ° C. or higher, more preferably 1500 ° C. or higher, preferably 2000 ° C. or lower.
  • the secondary oxidation step is a step of oxidizing graphite to obtain a carbon electrode material.
  • Oxidation treatment of the graphitized product gives a carbon electrode material having an oxygen functional group such as a hydroxyl group, a carbonyl group, a quinone group, a lactone group, and a free radical oxide introduced on the surface.
  • an oxygen functional group such as a hydroxyl group, a carbonyl group, a quinone group, a lactone group, and a free radical oxide introduced on the surface.
  • Roc (O / C) 1.0% or more between the number of bonded oxygen atoms O and the total number of carbon atoms C on the surface of the carbon electrode material specified in (6) above.
  • the Roc ratio is 1.0% or more, the electrode reaction can be improved, the resistance can be reduced, and the water flow rate can be improved.
  • the secondary oxidation treatment is performed under a dry method.
  • the atmosphere of the secondary oxidation treatment is an oxidizing atmosphere, preferably an air atmosphere.
  • the heating temperature of the secondary oxidation treatment is 500 ° C. or higher, preferably 600 ° C. or higher, more preferably 650 ° C. or higher, 900 ° C. or lower, preferably 800 ° C. or lower, and more preferably 750 ° C. or lower.
  • Oxidation treatment in this temperature range can introduce oxygen functional groups on the surface of the carbon electrode material.
  • the heating time is preferably 5 minutes or more and 1 hour or less.
  • the yield of the secondary oxidation step (the ratio of the amount of the secondary oxide after the secondary oxidation treatment solution, that is, the amount of carbon electrode material to the amount of graphitized product before the secondary oxidation treatment) is preferably 90% or more, 96%. It is desirable to control the processing conditions so as to be as follows.
  • the carbon particles (B) used for the electrode material are obtained by performing peak separation of the carbonaceous fibers (A), the carbon particles (B), and the carbonaceous material (C) from the chart obtained by the above wide-angle X-ray measurement.
  • the Lc value was calculated. Specifically, the peak where the apex is seen in the range of 26.4 ° to 26.6 °, which is twice the diffraction angle ⁇ (2 ⁇ ), is the carbon particle (B), and the range of 25.3 ° to 25.7 °.
  • the peak in which the apex is seen was defined as the carbonaceous material (C). From the peak top, the peak shape was determined as a sine wave.
  • Each Lc was calculated from each separated peak by the following method.
  • the following simple method was used without correcting the so-called Lorentz factor, polarization factor, absorption factor, atomic scattering factor, etc. That is, the real intensity from the baseline of the peak corresponding to the ⁇ 002> diffraction was re-plotted to obtain the ⁇ 002> corrected intensity curve. From the length of the line segment (half-value width ⁇ ) where the line parallel to the angle axis drawn to the height of 1/2 of the peak height intersects the correction intensity curve, the size of the crystallite in the c-axis direction is calculated by the following equation. I asked for Lc.
  • Metsuke amount (-1) Metsuke amount of electrode material
  • the electrode material was cut into 5.0 cm squares, the weight was measured with a weighing scale, and then the basis weight of the electrode material was calculated by the following formula.
  • the electrode material was crushed in a mortar. The crushed electrode material was placed on a sieve having a mesh size of 1.0 mm, shaken for 30 seconds, and then the sample remaining on the sieve was collected.
  • the mesopore specific surface area (m) with a pore diameter of 2 nm or more and less than 50 nm. 2 / g) and the specific surface area of all pores were determined.
  • BET BET Specific Surface Area
  • the total cell resistance (SOC 50% total cell resistance, ⁇ ⁇ cm 2 ) was calculated by the following formula.
  • SOC 50% total cell resistance, ⁇ ⁇ cm 2 the total cell resistance (SOC 50% total cell resistance, ⁇ ⁇ cm 2 ) was calculated by the following formula.
  • a 5.0 moL / L sulfuric acid aqueous solution in which titanium oxysulfate and manganese oxysulfate were dissolved at 1.0 moL / L was used.
  • the amount of electrolyte was too large for the cell and piping.
  • the liquid flow rate was 10 mL per minute, and the measurement was performed at 35 ° C.
  • VC50 is a value obtained from the electrode curve of the charging voltage with respect to the amount of electricity when the charging rate is 50%.
  • V D50 is a value obtained from the electrode curve of the discharge voltage with respect to the amount of electricity when the charge rate is 50%.
  • I is the current density (mA / cm 2 ).
  • Example 1 an electrode material made of a carbonaceous sheet was prepared and evaluated using the following materials.
  • the samples A, B, and D used as the carbonaceous particles (B) are all commercially available products.
  • the average particle size in Table 1 is the value described in the catalog.
  • Spunlace formed from flame-resistant polyacrylonitrile fiber as a precursor of a fiber structure formed from carbonaceous fiber (A) (manufactured by Shinwa Co., Ltd., mesh size 100 g / m 2 , mean curvature R40 mm -1 , average fiber diameter 20 ⁇ m , Average fiber length 80 mm, thickness 0.81 mm) was cut out from a roll and immersed in a dispersion liquid, and then passed through a nip roller to remove excess dispersion liquid.
  • the temperature is raised to 1000 ° C. at a heating rate of 5 ° C./min under a nitrogen atmosphere, and the temperature is maintained at this temperature for 1 hour for carbonization (firing).
  • the oxidation treatment was performed at 550 ° C. for 25 minutes in an air atmosphere (primary oxidation treatment).
  • the mixture is cooled, further heated to 1500 ° C. at a heating rate of 5 ° C./min under a nitrogen atmosphere, held at this temperature for 1 hour for graphite formation, and then at 650 ° C. under an air atmosphere.
  • Oxidation treatment (secondary oxidation treatment) was performed for 5 minutes, and No.
  • the electrode material of No. 1 was prepared.
  • No. 3 Felt made of flame-resistant polyacrylonitrile fiber (grain 160 g / m 2 , mean curvature 33R, mean fiber diameter 20 ⁇ m, average fiber length 80 mm, thickness 1. Except for the use of 3 mm), the above No. In the same manner as in No. 1. The electrode material of No. 3 (thickness 1.1 mm, basis weight 165 g / m 2 ) was prepared.
  • No. 5 As a precursor of a fiber structure formed of a carbonaceous fiber (A), a spunlace made of polyacrylonitrile fiber (manufactured by Shinwa Co., Ltd., with a grain size of 80 g / m 2 , an average curvature of 40 R, an average fiber diameter of 20 ⁇ m, and an average fiber length of 80 mm). , Thickness 0.81 mm), but the above No. In the same manner as in No. 4. The electrode material of No. 5 (thickness 0.49 mm, basis weight 112 g / m 2 ) was prepared.
  • No. 6 Except for changing the carbonization temperature from 1000 ° C to 1300 ° C, the above No. In the same manner as in No. 1.
  • the electrode material of No. 6 (thickness 0.47 mm, basis weight 132 g / m 2 ) was prepared.
  • No. 7 Carbon paper formed from polyacrylonitrile fiber as a precursor of a fiber structure formed from carbon fiber (A) (CFP-030-PE manufactured by Nippon Polymer Sangyo Co., Ltd., grain size 30 g / m 2 , mean curvature 0, thickness Except for 0.51 mm), the above No. In the same manner as in No. 1. No. 7 electrode material (thickness 0.39 mm, basis weight 74 g / m 2 ) was produced.
  • Carbon paper made of polyacrylonitrile fiber as a precursor of a fiber structure formed from carbon fiber (A) manufactured by Olivest Co., Ltd., grain 60 g / m 2 , mean curvature R0 mm -1 , mean fiber diameter 7 ⁇ m, average fiber length 6 mm , Thickness 0.84 mm
  • Ten electrode materials were prepared.
  • No. 11 is an example in which neither the carbon particles (B) nor the carbonaceous material (C) are used, and only the fiber structure formed from the carbonaceous fibers (A) is used. In detail, No. 1 except that the spunlace non-woven fabric was not attached. No. 1 in the same manner as in 1. Eleven electrode materials (thickness 0.46 mm, basis weight 55 g / m 2 ) were prepared.
  • Kao's Leodor TW-L120 nonionic surfactant
  • polyvinyl alcohol temporary adhesive
  • carbonaceous material C
  • a dispersion was prepared by adding 14.0% of a and 9.8% of the symbol D (graphite particles) in Table 1.
  • Kao's Leodor TW-L120 nonionic surfactant
  • polyvinyl alcohol temporary adhesive
  • carbonaceous material C
  • a dispersion was prepared by adding b (solid content 40%) to 3.8% and carbon particles (B) to 1.5% with the symbol A in Table 1.
  • No. 1 to 6 are electrode materials satisfying the requirements of the present invention.
  • No. In Nos. 1 to 6 the BET specific surface area of the mesopores was very large, and low resistance electrode materials were obtained. From these results, it is considered that the reaction surface area is increased and the electrode activity is improved by the surface exposure of the carbon particles (B) if both the material and the production conditions satisfy the suitable conditions of the present invention. In the example of the present invention, no creases or partial breaks occurred, and the electrode quality was also good.
  • No. in 7 to 10 (comparative example), in detail, No. It is an example manufactured under the same conditions as 1 to 6.
  • No. 8 is also No. This is an example using the same fiber structure as in 7. No. In No. 8, the dispersion liquid was impregnated a plurality of times to increase the supported amount, but the total cell resistance deteriorated. From this result, it is considered that if the supported amount is too large with respect to the fiber amount, the space through which the electrolytic solution flows is reduced and the resistance is increased.
  • No. Nos. 9 to 10 are examples in which the basis weight of the carbon fiber structure having a curvature R0 is increased.
  • the resistance of 9 to 10 could be reduced because the amount of support per sheet increased, but creases and partial breakage starting from the creases occurred frequently.
  • carbon particles (B), carbonaceous material (C), short fibers, etc. were severely dropped from the fractured portion. Therefore, it is difficult to handle when scaled up, and it is considered that the pressure loss increases due to clogging when the electrolytic solution is passed.
  • No. No. 11 is an example in which neither the carbon particles (B) nor the carbonaceous material (C) are used. No. In No. 11, the reaction surface area was insufficient and the resistance was significantly increased.
  • Reference numeral 12 denotes an example using carbon particles (B) that do not satisfy the present invention, and the total cell resistance increased. From this result, it is considered that since it is difficult to impart an oxygen functional group when carbon particles having high carbon crystallinity are used, the affinity of the vicinity of the carbon particles with respect to the aqueous electrolyte is lowered and the reaction activity is not improved. It is also considered that the small reaction surface area due to the large particle size of the carbon particles also had an effect.
  • No. No. 13 is an example in which the ratio of Lc (C) / Lc (A) is small, and the resistance is increased. From this result, when the carbon crystallinity of the carbon material (C) is low, the electron conduction resistance between the carbon particles (B) and the carbon fibers (A) becomes high, and the reaction activity of the carbon particles (B) is efficiently performed. Probably because it was not available.
  • No. No. 14 is an example in which the O / C ratio is small, the resistance is increased, and water does not pass through. From this result, it is considered that since the amount of oxygen functional groups is small, the affinity with the electrolytic solution is lowered and the reaction activity is lowered.
  • the carbon electrode material of the present invention is useful for the negative electrode of a Mn—Ti-based redox flow battery.
  • the carbon electrode material of the present invention is suitably used for flow type and non-flow type redox flow batteries, redox flow batteries combined with lithium, capacitor, and fuel cell systems.

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