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
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
  • H01M50/491—Porosity
• • 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
• • 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
  • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
  • H01M10/52—Removing gases inside the secondary cell, e.g. by absorption
• • 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
  • H01M4/244—Zinc 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
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/362—Composites
  • H01M4/364—Composites as mixtures
• • 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
  • H01M4/621—Binders
• • 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
  • H01M4/624—Electric conductive fillers
  • H01M4/626—Metals
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/661—Metal or alloys, e.g. alloy coatings
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/70—Carriers or collectors characterised by shape or form
  • H01M4/72—Grids
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/30—Arrangements for facilitating escape of gases
  • H01M50/342—Non-re-sealable arrangements
  • H01M50/3425—Non-re-sealable arrangements in the form of rupturable membranes or weakened parts, e.g. pierced with the aid of a sharp member
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M6/00—Primary cells; Manufacture thereof
  • H01M6/04—Cells with aqueous electrolyte
  • H01M6/06—Dry cells, i.e. cells wherein the electrolyte is rendered non-fluid
  • H01M6/10—Dry cells, i.e. cells wherein the electrolyte is rendered non-fluid with wound or folded 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
• • 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
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• This invention relates to electrochemical cells and more particularly, to sealed, rechargeable nickel- zinc cells.
• nickel cadmium cells Despite the advantages provided by nickel cadmium cells, there is a continuing demand for many applications for a power source capable of achieving even higher energy densities and operating at higher working voltages. This situation has led to the investigation of nickel-zinc rechargeable cells for these applications.
• the nickel- zinc system is well known and, at least potentially, offers substantial advantages.
• nickel-zinc cells In comparison to nickel- cadmium cells, nickel-zinc cells have higher working or operating voltages (viz. about 1.65 volts) and poten ⁇ tially can provide significantly higher energy densities.
• U.S. Patents 3,951,687 and 4,037,033 disclose configura ⁇ tions for nickel-zinc cells.
• a sealed nickel-zinc cell must therefore possess the ability to compensate
• prior cells of this type appear to have less than an optimum tolerance to overcharge con ⁇ ditions. While not fully understood, it is believed that the less than optimum tolerance is due to the separator configurations previously utilized. Also, in this regard, it appears that the cycle life of nickel- zinc cells, particularly at high discharge rates, are less than optimum.
• OMPI A still further object of this invention lies in the provision of a cell of the foregoing type having the capability of operation at relatively high current levels.
• Yet another object of this invention is to provide a cell of the foregoing type capable of being allowed to stand for prolonged periods of time in a discharged condition without undue internal pressure build-up.
• Another object of the present invention is to provide a cell of the foregoing type which minimizes zinc passivation.
• a still further object is to provide a cell of the foregoing type which possesses improved tolerance to overcharge conditions.
• FIGURE 1 is a side elevation of a nickel-zinc cell embodying the present invention and partially cut-away to show the internal configuration
• FIG. 2 is a cross-sectional view taken generally . along lines 2-2 of FIGURE 1 and further illustrating the internal configuration of a cell according to the present invention
• FIG. 3 is a graph illustrating the cycle life performance of a cell of the present invention compared to prior art cells
• FIG. 4 is a graph illustrating the hydrogen pressure developed within a nickel-zinc cell with and without the hydrogen recombination catalyst utilized according to one aspect of the present invention.
• the present invention is predicated on the discovery that nickel-zinc cells having improved electrical performance characteristics can be provided by selection of the mixture utilized for the negative electrode, the particular binder employed for the nega ⁇ tive electrode, and the separator system utilized. Each of these parameters will individually impart im ⁇ proved performance to the cell. Optimum performance is provided by utilizing all of the features which will be described herein.
• an auxiliary feature of this invention provides a specific means for dealing with the internal pressure build-up due to the evolution of hydrogen.
• the cell 10 comprises an outer housing 12 defining a cell 14.
• the cup-shaped housing 12 has an open end 16 which is closed by closure 18 sealingly mounted upon open end 16 by an annular insu ⁇ lator 20.
• a perforator disc 22 is secured to the open
• OMPI IPO end 16 of the outer housing 12 by an annular retainer 24 and is provided with a piercing tab 26 adapted to pierce closure 18 in the event the closure is urged outwardly, as by internal pressure buildup within the sealed battery.
• a resealable vent could be employed; and many such vent constructions are known.
• a cell element shown gen ⁇ erally at 28 is contained in cell 14 in the form of a wound roll comprising a negative electrode layer 30, a positive electrode layer 32, and a separator shown generally at 34 , intermediate the electrode layers.
• a wicking layer for absorbing electrolyte is preferably provided. It has thus been found that the inclusion of a wicking layer on the side of the separator adjacent the positive electrode layer serves to impart to the cell longer cycle life, particularly when the service regime involves relatively high discharge rates (e.g. - about 2C or higher).
• any alkali-resistant'material capable of absorbing electrolyte can be utilized.
• a non-woven fabric of a synthetic resin, such as polypropylene, nay be employed.
• a suitable polypropylene wicking sheet is "Webril 1488" non-woven fabric (Kendall Company) having a thickness of about 3 mils.
• a wicking layer 36 for absorbing electrolyte is provided on the side of the separator 34 adjacent the positive electrode layer 32.
• a wicking layer could be likewise provided adjacent the negative electrode layer 30, if desired.
• the use of a wicking layer adjacent the negative electrode may offer advantage in relation to the inclusion of no wicking layer adjacent either
• perforator disc 22 co ⁇ operates with closure 18 in defining the negative ter ⁇ minal of the housing. More specifically, a first con ⁇ necting means tab 38 is electrically connected to the negative electrode layer 30, extending outwardly from the roll into electrically connected association with closure 18.
• Outer housing 12 suitably comprises a metal can which defines the positive terminal of the battery.
• a second con ⁇ necting tab means 40 is electrically connected with positive electrode layer 32 and housing 12.
• the positive and nega ⁇ tive electrode layers and the separator When utilized in a cylindrical cell, as is shown in the illustrative embodiment, the positive and nega ⁇ tive electrode layers and the separator should be suf ⁇ ficiently flexible so that a wound element can be pro ⁇ vided.
• the manufacturing techniques to provide suitable positive and negative electrode layers of adequate flexibility are well known. Suitable techniques are described in the copending Menard et al. application identified herein.
• the negative zinc electrodes may thus be made by conventional techniques.
• a powdered mixture of the desired materials and a binder can be rolled onto a suitable current collector, such as, for example, a copper screen.
• binder materials for fabricating zinc electrodes are known.
• the binder material used is inert in the cell environment and is incorporated in an amount just sufficient to hold the mixture together, providing a positive bond as well to the current collector.
• binder materials such as polytetrafluoroethylene
• binder materials require relatively large amounts to be employed in order to achieve the desired coherent structure for the negative electrode, amounts on the order of 10% by weight based upon the weight of the mixture often being used.
• Such relatively large amounts of binder result in the cell having relatively high impedance values. This restricts the current level which the cell can utilize in service.
• a further principal aspect of the present invention comprises utilizing an elastomeric, self-cured carboxylated styrene-butadiene latex as the binder material . It has been found satisfactory to utilize this binder in an amount preferably in the range of about 3.8% to about 5%, based upon the total weight of the negative electrode mixture. Amounts in this level have been found to achieve an adequate co ⁇ herent structure for the negative electrodes. Moreover, and importantly, this results in cells characterized by relatively low impedance in comparison to prior cells and may thus allow significantly higher current levels in service. Amounts in excess of 5% by weight may certainly be utilized, but such amounts offer little advantage and tend to provide increased impedance. Specific illustrative examples of suitable binders are AMSCO RES 4150 and 4816, manufactured by the AMSCO Division of Union Oil Company.
• the negative electrode may contain other ingredients, some of which are known.
• the amount of cadmium utilized should be such as to provide 20% of the ampere-hour capacity of the posi ⁇ tive active material . Amounts above this minimum level may certainly be utilized, the upper limit likely being constrained by economic considerations. Based upon the total weight of the negative electrode mixture, the amount of cadmium in the range of about 5 to 6% or so should be suitable to provide such minimum.
• the cadmium component may be utilized in the mixture as cadmium oxide. However, as has been noted in the copending Gibbard application, it is perferred to utilize cadmium metal. The use of cadmium oxide may accordingly result in some loss in capacity.
• Bi_0 bismuth oxide
• the zinc specie(s) formed during discharge is soluble in the electrolyte to a signficant extent.
• Some of the active zinc material thus tends to enter the electrolyte while the system is being discharged, as well as while the system stands in a discharged condition.
• the zinc specie(s) in the electrolyte Upon recharging of the battery system, the zinc specie(s) in the electrolyte returns to the zinc electrode but can alter the electrode struc ⁇ ture.
• the active zinc material can thus migrate from the edges or periphery of the electrode structure and collect in the central regions of electrode, resulting in an irreversible loss of capacity. This phenomenon has been often termed "shape change".
• the cell element uti ⁇ lized in the present invention should be positioned in the cell in a fashion which will at least minimize shape change. It has been found satisfactory, when a cylindrical cell is involved, simply to wind the element such that the element is under compression while in position within the cell. This assists in minimizing shape change as a problem.
• the material used for the separator should be a membrane having a relatively fine, uniformly sized pore structure which allows electrolyte permeation therethrough while preventing dendrite penetration. Still further, the material employed should possess chemical stability in the cell environment. Additionally, suitable materials should possess sufficient flexibility and strength characteristics to endure adequately any shape change and/or electrode expansion that might take place during service. A large number of materials have been proposed for use and are well known, as are their methods of manufacture.
• the separator may comprise a commercially available "Celgard" polypropylene film (Celanese Fiber Company) . It has been found par ⁇ ticularly desirable to utilize two layers of such material (each layer about one mil thick being adequate) to form the separator layer 34, the individual layers being shown generally at 42 and 44 (FIG. 2). The use of two layers allows the large pores or holes, due to imperfections produced during manufacture or subsequently, in each layer to be non-aligned with respect to each other to minimize problems with dendrites. Of course, a single layer or more than two layers may likewise be employed if desired.
• any conventional alkaline electrolyte used with a nickel-zinc system may be employed.
• the amount of electrolyte used should be restricted sufficiently so that an effective oxygen recombination reaction will be provided.
• the necessary electrolyte can be added to the open space in the core of the wound cell element 28 prior to the sealing of the cell.
• first connecting tab 38 this should be made of a conductive material having an over- voltage for hydrogen evolution at least approximately as high as that of zinc.
• An illustrative example is a nickel element, plated with copper and then overplated with silver.
• the closure 18 may suitably comprise a steel sheet plated with nickel which is, in turn, covered with copper plating, and then covered with silver plating.
• the second connecting tab 40 may comprise, for example, a nickel element which is electrically connected to the nickel plating 46 of outer housing 12.
• OMPI cell of the present invention The particular materials of construction may accordingly vary rather widely.
• a water sealant coating may be applied to the metal or other surfaces in the cell.
• a suitable sealant is the styrene-butadiene material described herein as the binder for the negative electrode mixture.
• a coating 48 has been applied to the exposed surfaces of the closure 18 and the first connecting tab 38. This may be applied by brushing on to a thickness, for example, of about 1 nil .
• insulators 50, 50' may be included, if desired. While shown as spatially removed from the cell element 28 for simplicity of illustration, insulator 50 may suitably rest upon separator layers 42, 44 which desirably terminate somev.'hat above the upper end of the electrodes.
• the nickel-zinc cell of the present invention may be utilized in either a prismatic or cylindrical design, as is desired for the particular application.
• the capacity of the cell may vary within wide limits, the size being dictated by the requirements of the particular end use application.
• a cylindrical sub-C size cell for use in cordless or portable power tools may suitably have a capacity of, for example, 1.2 Ampere-Kours.
• the cells of the present invention must likewise incorporate a means for oxidizing the hydrogen evolved in service to maintain a satisfactorily low internal pressure within the cell.
• a variety of catalytic means are known and may be enployed.
• an auxiliary aspect of the present invention provides as the hydrogen oxidation source a
• OMPI WIPO hydrogen recombination catalyst located in the cell which is free of electrical connection to the cell elements.
• Any fuel cell cathode may suitably be employed.
• the recombi ⁇ nation catalyst may suitably comprise carbon cloth having about 1% by weight platinum catalyst on carbon particles bonded to the cloth by a hydrophobic binder, such as polytetrafluoroethylene.
• Suitable recombination catalysts such as the illustrative embodiment are com ⁇ flashally available.
• a hydrogen recombination catalyst 52 is positioned in the axial core space of the wound role cell element and is free of electrical connection to the cell electrodes. In this fashion, the assembly of the cell is facilitated.
• Utilization of the hydrogen recombination catalyst has been found to substantially reduce the internal pressure developed under typical cycling conditions. However, the performance upon prolonged stand and high rate charge/discharge conditions can certainly be improved. Under either of these conditions, internal pressure can develop to the point where the cells may well vent.
• FIG. 3 demonstrates the extended cycle life of cells pursuant to the present invention at high dis ⁇ charge rates. Curves A and C of FIG. 3 represent dis ⁇ charge curves of cells according to the present inven ⁇ tion at two hour and one-half hour rates, respectively.
• Curves B and D are discharge curves for previous state- of-the-art nickel-zinc cells at 2.5-hour and I-hour discharge rates, respectively. These latter rates should be substantially less stressful than the cor ⁇ responding rates used for the cells of this invention. As may be seen in FIG. 3, the discharge capacity of the cells of this invention is maintained substantially higher than the discharge capacity of a conventional nickel-zinc cell up- to two hundred cycles or more.
• FIG. 4 illustrates the performance of a cell which is achieved using the hydrogen recombination catalyst 52.
• Curve E illustrates the hydrogen pressure developed in the absence of the recombination catalyst 52
• Curve F illustrates the hydrogen pressure developed in the cell where the recombination electrode 52 is provided. The substantial decrease in the developed pressure due to the inclusion of the recombination catalyst is apparent.
• the negative electrode layer comprises a first mixture of zinc, zinc oxide, cadmium oxide, bismuth oxide and a styrene-butadiene binder rolled onto a copper screen. Based upon the weight of the mixture, zinc was present in an amount of 4.5%, cadmium oxide in an amount of 5.8%, bismuth oxide in an amount of 7.5% and binder in an amount of about 4%, the balance being zinc oxide.
• the hydrogen recom ⁇ bination catalyst comprised a 0.1 inch x 1 inch carbon cloth strip containing 1% by weight platinum.
• the negative electrode dimensions were 0.016 inch x 1.31 inch x 9 inch and the positive electrode dimensions were 0.028 inch x 1.2 inch x 7 inch.
• the negative electrode may initially contain a charged zinc mass in the amount of about 35% of the total theoretical A pere-Hour capacity; however, this should be converted to zinc oxide by the reaction of the zinc with the added cadmium oxide and bismuth oxide.
• the resulting cadmium should represent about 25% of the 1.2 Ampere-Hour battery capacity.
• the amount of zinc oxide initially present is roughly 425% of the Ampere- Hour capacity of the cell, the actual capacity being limited by the positive electrode.

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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)
• Composite Materials (AREA)
• Secondary Cells (AREA)
• Battery Electrode And Active Subsutance (AREA)

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Publications (1)

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Cited By (9)

Citations (9)

Family Cites Families (5)

• 1983
  • 1983-07-21 EP EP19830902660 patent/EP0114884A4/en not_active Withdrawn
  • 1983-07-21 WO PCT/US1983/001132 patent/WO1984000642A1/en not_active Application Discontinuation
  • 1983-07-21 JP JP58502757A patent/JPS59501521A/ja active Granted
  • 1983-07-21 AU AU18878/83A patent/AU549585B2/en not_active Ceased
  • 1983-07-27 CA CA000433359A patent/CA1209200A/en not_active Expired
  • 1983-07-27 PH PH29307A patent/PH18838A/en unknown
  • 1983-07-27 MX MX198175A patent/MX154785A/es unknown
  • 1983-11-21 IN IN1431/CAL/83A patent/IN162152B/en unknown

Patent Citations (9)

Non-Patent Citations (1)

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