Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M12/00—Hybrid cells; Manufacture thereof
  • H01M12/08—Hybrid cells; Manufacture thereof composed of a half-cell of a fuel-cell type and a half-cell of the secondary-cell type
• • 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
• • 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
  • Y02E60/10—Energy storage using batteries

Definitions

• the positive electrode active material is oxygen
• the positive electrode has the function of absorbing and releasing oxygen from the air as the battery is charged and discharged.
• the carbon structure used in the positive electrode is required to have a structure that can capture a large amount of oxygen from the air.
• the carbon structure for the positive electrode is required to have high air or oxygen permeability.
• Patent Document 1 describes a method for forming a positive electrode layer, for example, by applying a paint prepared by dispersing a composition containing a conductive porous body and a binder in a solvent onto a positive electrode current collector using a doctor blade method or the like, or by molding the composition using a pressure press.
• examples of the current collector include stainless steel, nickel, aluminum, and carbon
• examples of the shape of the collector include foil, plate, and mesh, with the mesh shape being particularly preferred.
• the reinforcing carbon fiber helps maintain the shape of the carbon structure, but the carbon fiber itself does not contribute at all as a site for the reaction of lithium ions, oxygen, and electrons to produce lithium peroxide during the discharge process. Therefore, the inclusion of carbon fiber reduces the discharge capacity of the air battery in proportion to its content.
• the carbon structure of the present invention can be made to maintain its shape and be self-supporting, using only carbon material and binding polymer carbonized.
• the carbon structure of the present invention does not require a current collector or reinforcing material such as carbon fiber to maintain its shape, so it is possible to reduce areas that do not contribute to the charge/discharge reaction, i.e., do not contribute to the discharge capacity. This makes it possible to increase the discharge capacity per carbon structure, making it possible to provide a small, lightweight air battery with a large discharge capacity.
• the average diameter, average length, and aspect ratio of the carbon nanotubes that form the carbon material are within the above ranges, it is possible to obtain a carbon structure that maintains its shape and is self-supporting, even without adding reinforcing materials such as carbon fiber, and that can realize an air battery that exhibits high discharge capacity, in the manufacturing method of the carbon structure described below.
• the average diameter of the carbon nanotubes used as the raw material for the carbon structure of the present invention is 1 nm or more and 10 nm or less. If the average diameter of the carbon nanotubes exceeds 10 nm, the number of carbon nanotubes in the carbon structure decreases, and the production site of lithium peroxide generated in the discharge reaction decreases, resulting in a small discharge capacity of the resulting air battery. Carbon nanotubes with a diameter of less than 1 nm are difficult to manufacture and difficult to obtain.
• the aspect ratio of the carbon nanotubes used as the raw material of the carbon structure of the present invention is from 1000 to 10000.
• the aspect ratio of the carbon nanotubes is less than 1000, the carbon nanotubes are relatively short in length, and so the carbon nanotubes turn into powder, and when they are mixed with a binder polymer and a solvent to prepare a mixture slurry, and then coated and dried to mold the mixture slurry, the bonding strength between the carbon nanotubes is weak, and the coating film collapses.
• the aspect ratio of carbon nanotubes exceeds 10,000, the carbon nanotubes are relatively long, so they are poorly dispersed when mixed with a binder polymer and a solvent to make a mixture slurry. Even if the mixture slurry is coated to be molded, it becomes clumpy, making it difficult to mold it into a molded body.
• the pore volume occupied by pores having a diameter of 1 nm or more and 1000 nm or less as measured by the nitrogen adsorption method is preferably 1.0 cm3 /g or more and 3.0 cm3 /g or less. Note that (a) the pore volume occupied by pores having a diameter of 1 nm or more and 1000 nm or less as measured by the nitrogen adsorption method is rounded off to one decimal place.
• the pore volume of the carbon structure which is occupied by the pores having a diameter of 1 nm or more and 1000 nm or less as measured by the nitrogen adsorption method, is within the above range, when the carbon structure is used as the positive electrode of an air battery, it is possible to store more lithium peroxide generated by discharge, and to provide a battery with high discharge capacity characteristics.
• the large pore volume of this pore region makes it easier for air or oxygen to permeate and diffuse within the carbon structure. Therefore, it is possible for air or oxygen introduced from outside the battery into the positive electrode to permeate every corner of the carbon nanotubes that form the carbon skeleton at high speed.
• the large pore volume of this pore region allows lithium (Li) ions to move smoothly, and combined with the high permeability and diffusibility of air and oxygen, it is possible to provide an air battery with excellent high-speed discharge characteristics, i.e., high-load characteristics.
• the pore volume of the carbon structure occupied by pores having a diameter of 1 nm or more and 1000 nm or less as measured by the nitrogen adsorption method (a) may be more preferably 1.2 cm 3 /g or more, 1.4 cm 3 /g or more, 1.6 cm 3 /g or more, or 2.0 cm 3 /g or more, in order to provide a battery having better charge/discharge characteristics.
• the pore volume of the pores having a diameter of 1 nm or more and 200 nm or less as measured by the nitrogen adsorption method (b) may be more preferably 2.2 cm 3 /g or less, 1.8 cm 3 /g or less, 1.5 cm 3 /g or less, or 1.2 cm 3 /g or less, in terms of enabling the carbon structure to maintain its self-supporting property while maintaining sufficient strength.
• the pore volume occupied by pores having a diameter of 200 nm to 10,000 nm measured by mercury intrusion porosimetry is preferably 1.0 cm3 /g to 3.3 cm3 /g. Note that (c) the pore volume occupied by pores having a diameter of 200 nm to 10,000 nm measured by mercury intrusion porosimetry is rounded off to one decimal place.
• pores with a diameter of 200 nm to 10,000 nm measured by mercury intrusion porosimetry mainly function to allow oxygen from outside the battery to penetrate into the carbon structure, which is the positive electrode. For this reason, a large pore volume in the above range suggests that a sufficient amount of oxygen can penetrate and can penetrate at a high speed when lithium ions react with oxygen to generate lithium peroxide.
• an air battery using the carbon structure of the present invention as the positive electrode has a large discharge capacity at a high current density, that is, a battery with excellent high-load characteristics.
• lithium peroxide transfers electrons to the electrode to become Li ions and oxygen, and when the pore volume occupied by pores with a diameter of 200 nm to 10,000 nm is in the above range, oxygen generated from the carbon structure is easily released, enabling high-speed charging.
• the t-plot external specific surface area measured by the nitrogen adsorption method is in the range of 100 m 2 /g or more and 300 m 2 /g or less, which is derived from the t-plot external specific surface area of the raw material carbon nanotubes.
• the carbon derived from the polymer binder is bonded to the carbon nanotubes, so the value is smaller than that of the raw material carbon nanotubes.
• Solvents used to prepare the mixture slurry include, for example, dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMA), etc.
• DMSO dimethyl sulfoxide
• NMP N-methylpyrrolidone
• DMF dimethylformamide
• DMA dimethylacetamide
• FIG. 4 is a schematic view showing a stacked-type air battery (stacked-type metal battery).
• the composite molded sheet was placed in a tray, 220 g of methanol was added, and the sheet was left to stand. After 2 hours, the methanol in the tray was drained, and 220 g of new methanol was added and left to stand for 17 hours. After that, the methanol in the tray was drained, and a porous membrane-formed phase-separated sheet (porous structure) was obtained.
• the obtained dried sheet (carbon structure precursor) was subjected to an infusible heat treatment at 320°C for 3 hours in an air circulating atmosphere using a Yamato Inert Oven DN411, and the polyacrylonitrile (PAN) of the dried sheet (carbon structure precursor) was oxidized and cross-linked to form a cyclized infusible resin, thereby obtaining an infusible sheet (infusible carbon structure) having a length of 90 mm and a width of 80 mm.
• PAN polyacrylonitrile
• Ketjen Black EC600JD (Lion Specialty Chemicals) (KB) was used.
• Ketjen Black EC600JD (KB) is a carbon particle with a primary particle diameter of about 34 nm that is bonded in the shape of a bunch of grapes to form secondary particles, and the particle diameter was 4.2 ⁇ m at 50% particle diameter.
• Other properties of Ketjen Black EC600JD are also shown in Table 1.
• the 50% particle diameter was measured using a laser type particle size distribution meter LA950V2 (Horiba) with ethanol as the dispersion medium, at a circulation speed of 3 and ultrasonic intensity of 7 after dispersion for 3 minutes, and the particle diameter value of 50% accumulated on a volume basis was used.
• Carbon materials As the carbon material, carbon nanotubes "Cnano-CNT FT6120" (Cnano Corporation) (CNT4) were used. As shown in Table 1, Cnano-CNT FT6120 has an average diameter of 8 nm, an average length of 150 ⁇ m, and an aspect ratio of 19,000.
• Carbon materials As the carbon material, the same carbon nanotube "Cnano-CNT FT6120" (Cnano Corporation) (CNT4) as in Comparative Example 4 was used.
• the carbon structure of the present invention makes it possible to realize a small, lightweight air battery with a large discharge capacity.
• the carbon structure of the present invention is manufactured without undergoing a carbonization process in an oxidizing gas atmosphere, it is easier to produce and the manufacturing costs can be reduced when realizing an air battery with a high discharge capacity, compared to carbon structures that undergo a carbonization process in an oxidizing gas atmosphere.
• Negative electrode structure 620, 621 Positive electrode structure 630 Restraint 635 Current collector 640 Metal layer 650 Spacer 660 Separator 670 Space 680 Metal mesh 500 Air battery 100 Negative electrode laminate 510 Positive electrode laminate 520 Negative electrode current collector 525 Positive electrode current collector 540 Separator 800 Coin cell 810 Positive electrode can 815 Negative electrode can 840 Positive electrode 850 Separator 860 Negative electrode 870 Disk 875 Belleville spring 880 Gasket

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Inert Electrodes (AREA)
• Hybrid Cells (AREA)
• Carbon And Carbon Compounds (AREA)

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Citations (5)

• 2022
  • 2022-12-26 JP JP2022207774A patent/JP2024092093A/ja active Pending
• 2023
  • 2023-12-04 WO PCT/JP2023/043302 patent/WO2024142776A1/ja not_active Ceased
  • 2023-12-04 CN CN202380077934.2A patent/CN120226170A/zh active Pending

Patent Citations (5)

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