Classifications

• • 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
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/24—Electrodes for alkaline accumulators
  • H01M4/32—Nickel oxide or hydroxide electrodes
• • 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
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/24—Alkaline accumulators
  • H01M10/30—Nickel accumulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/34—Gastight accumulators
  • H01M10/345—Gastight metal hydride accumulators
• • 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 present invention relates to an active material for a nickel positive electrode, a nickel positive electrode using the active material, and to an alkaline electrochemical cell using the nickel positive electrode.
• Nickel hydroxide has been used for years as an active material for the positive electrode of alkaline batteries.
• Examples of such nickel-based alkaline batteries include nickel cadmium (Ni-Cd) batteries and nickel-metal hydride (NiMH) batteries.
• NiCd cells In a NiCd cell, cadmium metal is the active material in the negative electrode.
• NiCd cells use a positive electrode of nickel hydroxide material. The negative and positive electrodes are spaced apart in the alkaline electrolyte. The charge/discharge reactions at the negative electrode are controlled by the following reaction: charge Cd(OH) 2 + 2e ⁇ ⁇ > Cd + 20H " (1) discharge
• the reactions that take place at the positive electrode of a Ni-Cd cell are also reversible.
• the reactions at a nickel hydroxide positive electrode in a nickel cadmium cell are:
• Ni-MH cells utilize a negative electrode that is capable of the reversible electrochemical storage of hydrogen, and a positive electrode of nickel hydroxide material. The negative and positive electrodes are spaced apart in the alkaline electrolyte. Upon application of an electrical potential across a
• Ni-MH cell the Ni-MH material of the negative electrode is charged by the electrochemical absorption of hydrogen and the electrochemical generation of hydroxyl ions : charge M + H 2 0 + e " ⁇ > MH + OH " (3) discharge
• the negative electrode reactions are reversible. Upon discharge, the stored hydrogen is released to form a water molecule and evolve an electron.
• the charging efficiency of the positive electrode and the utilization of the positive electrode material is effected by the oxygen evolution process which is controlled by the reaction :
• the oxygen evolution reaction (7) During the charging process, a portion of the current applied to the battery for the purpose of charging, is instead consumed by the oxygen evolution reaction (7).
• the oxygen evolution of equation (7) is not desirable and contributes to lower utilization rates of the positive active material upon charging.
• One reason both reactions occur is that their electrochemical potential values are very close. Anything that can be done to widen the gap between them, lowering the nickel electrochemical potential in reaction (6) or raising the electrochemical potential of the oxygen evolution reaction (7) , will contribute to higher utilization rates.
• the electrochemical potential of the oxygen evolution reaction (7) is also referred to as the oxygen evolution potential .
• the electrochemical potential of reaction (7) is more temperature dependent than that of reaction (6) .
• oxygen evolution is low and the charging efficiency is high.
• the electrochemical potential of reaction (7) decreases and the rate of the oxygen evolution reaction (7) increases so that the charging efficiency of the nickel hydroxide positive electrode drops.
• High temperatures at the positive electrodes may be due to the external environment at which the battery is operated. They may also be due to the heat generated within the battery by oxygen gas recombination at the negative electrodes .
• One way to increase the electrochemical potential of equation (7) is by mixing certain additives with the nickel hydroxide active material when forming the positive electrode paste.
• U.S. Patent No. 5,466,543 to Ikoma, and U.S. Patent Nos. 5,571,636 and 5,451,475 to Ohta et al discloses certain additives which improve the rate of utilization of the nickel hydroxide in a wide temperature range.
• the present invention discloses new additives which improve the high temperature utilization of nickel-based positive electrodes.
• An objective of the present invention is an positive electrode active material mixture, a nickel positive electrode, and an alkaline electrochemical cell having high- temperature capacity and utilization.
• a positive electrode active material mixture for use in a paste for fabricating positive electrodes comprising: a nickel hydroxide material; and an additive material comprising at least one element selected from the group consisting of calcium cobalt oxide, calcium titanium oxide, calcium molybdenum oxide, lithium cobalt oxide, and mixtures thereof.
• a nickel positive electrode for use in an alkaline electrochemical cell comprising: an active material mixture comprising: a nickel hydroxide material; and an additive material comprising at least one element selected from the group consisting of calcium cobalt oxide, calcium titanium oxide, calcium molybdenum oxide, lithium cobalt oxide, and mixtures thereof
• an alkaline electrochemical cell comprising: at least one positive electrode; at least one negative electrode; and electrolyte; where the positive electrode comprises an active material mixture comprising: a nickel hydroxide material; and an additive material comprising at least one element selected from the group consisting of calcium cobalt oxide, calcium titanium oxide, calcium molybdenum oxide, lithium cobalt oxide, and mixtures thereof .
• the active material mixture comprises a nickel hydroxide material and an additive material.
• the additive material is one or more materials selected from the group consisting of calcium cobalt oxide, calcium titanium oxide, calcium molybdenum oxide, and lithium cobalt oxide. Mixtures of calcium cobalt oxide, calcium titanium oxide, calcium molybdenum oxide, and lithium cobalt oxide may also be used.
• the additive is calcium cobalt oxide.
• the additive is calcium titanium oxide.
• the additive is calcium molybdenum oxide.
• the additive is lithium cobalt oxide.
• the additive is calcium molybdenum oxide .
• the additive is between about 1% and 10% by weight of the positive electrode material. More preferably, the additive is between about 2% and 6% by weight of the positive electrode material. Most preferably, the additive is about 3% by weight of the positive electrode material.
• the nickel hydroxide material may be any nickel hydroxide material known in the art. It is within the spirit and intent of this invention that any and all kinds of nickel hyroxide materials may be used. Examples of possible nickel hydroxide materials are provided in U.S. Patent Nos. 5,348,822 and 5,637,423, the contents of which are incorporated by reference herein.
• the nickel positive electrode for use in an alkaline electrochemical cell.
• the nickel positive electrode comprises the active material mixture described above.
• An electrically conductive substrate is used as a support for the active material.
• the additive materials are mixed with the nickel hydroxide material.
• a binder such as polyvinyl alcohol, is also added to the mixture to form a paste.
• the paste is affixed to the electrically conductive substrate to form an electrode.
• the electrically conductive substrate may be any electrically conductive support, known in the art, capable of holding the positive electrode material . It is within the spirit and intent of this invention that any and all kinds of electrically conductive subtrates may be used. Examples of substrates include foam, perforated metal, expanded metal, screen, and matte.
• the substrate is a metal foam.
• any metal may be used as long as it is immune from corrosion at the pH and potential of the positive electrode.
• examples include a metal foam comprising nickel, nickel alloy, nickel plated steel, and nickel plated copper.
• the metal foam comprises nickel or a nickel alloy.
• the additive material serves to increase the electrochemical potential of the oxygen evolution reaction (7) at high temperatures. As a result, the charging reaction of nickel hydroxide to nickel oxyhydroxide expressed as reaction formula (6) sufficiently proceeds to improve the utilization of the nickel positive electrode in the high-temperature atmosphere .
• the nickel positive electrode of the present invention may be used in any nickel-based, alkaline electrochemical cell.
• an electrochemical cell comprises at least one nickel positive electrode, at least one negative electrode, and an electrolyte surrounding the positive and negative electrodes.
• the electrolyte is an alkaline electrolyte which may comprise a potassium hydroxide solution.
• nickel-based electrochemical cells examples include nickel-metal hydride, nickel-cadmium, nickel-zinc, and nickel- hydrogen electrochemical cells.
• the nickel-cadmium electrochemical cell uses cadmium negative electrodes comprising a cadmium active material.
• the nickel-metal hydride electrochemical cell uses a metal hydride negative electrode comprising a metal hydride active material.
• the metal hydride negative electrode comprises metal hydride material affixed to an electrically conductive substrate. It is within the spirit and intent of this invention that any and all kinds of metal hydride materials may be used. Examples of metal hydride materials are the Ti- V-Zr-Ni type active materials such as disclosed in U.S. Patent No. 4,551,400 ("the '400 Patent") to Sapru, Hong, Fetcenko, and Venkatesan, the disclosure of which is incorporated by reference. These materials reversibly form hydrides in order to store hydrogen. Further metal hydride materials are described in U.S.
• Patent No. 4,728,586 (“the '586 Patent”) to Venkatesan, Reichman, and Fetcenko, the disclosure of which is incorporated by reference.
• the '586 Patent describes a specific sub-class of Ti-V-Ni-Zr alloys comprising Ti , V, Zr, Ni, and a fifth component, Cr .
• the '586 Patent mentions the possibility of additives and modifiers beyond the Ti , V, Zr, Ni , and Cr components of the alloys, and generally discusses specific additives and modifiers, the amounts and interactions of these modifiers, and the particular benefits that could be expected from them.
• Other examples of metal hydride materials are provided in U.S. Patent No. 5,536,591, the disclosure of which is incorporated by reference herein.
• Example A "standard” positive electrode paste was formed from about 88.6% active nickel hydroxide material, about 5% by weight of cobalt, about 6% by weight of cobalt oxide, and about 0.4% by weight of polyvinyl alcohol binder. The paste was affixed to a nickel foam substrate to form a "standard" positive electrode.
• the standard positive electrode as well as the four additional electrodes made from the new active materials were all tested using the tri-electrode test technique.
• a small tri-electrode cell for testing electrodes was designed. The cell was fabricated by positioning a positive electrode between two negatives in the presence of excess electrolyte. The three electrode system was held in place by two plexiglass plates. The negative electrode used for the test was a nickel-metal hydride electrode. After initial formation, charges were done at C/10 to 120% charge. The discharges are done at C/10 until cutoff voltage of 0.9 volts. The capacity of each electrode was measured at 22°C and at 45°C. The percentage decrease in capacity is shown in the Table.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Battery Electrode And Active Subsutance (AREA)
• Secondary Cells (AREA)

Priority Applications (6)

Applications Claiming Priority (2)

Publications (1)

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Cited By (2)

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Citations (3)

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• 1998
  • 1998-08-18 US US09/136,129 patent/US6017655A/en not_active Expired - Lifetime
• 1999
  • 1999-08-13 AU AU54861/99A patent/AU5486199A/en not_active Abandoned
  • 1999-08-13 JP JP2000566908A patent/JP2003523043A/ja active Pending
  • 1999-08-13 MX MXPA01001377A patent/MXPA01001377A/es unknown
  • 1999-08-13 DE DE69940119T patent/DE69940119D1/de not_active Expired - Lifetime
  • 1999-08-13 WO PCT/US1999/018527 patent/WO2000011738A1/en not_active Ceased
  • 1999-08-13 CA CA002339129A patent/CA2339129A1/en not_active Abandoned
  • 1999-08-13 EP EP99941152A patent/EP1110259B1/en not_active Expired - Lifetime

Patent Citations (3)

Non-Patent Citations (1)

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