Classifications

• • 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
  • H01M10/04—Construction or manufacture in general
  • H01M10/0413—Large-sized flat cells or batteries for motive or stationary systems with plate-like electrodes
• • 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
  • H01M10/04—Construction or manufacture in general
  • H01M10/0463—Cells or batteries with horizontal or inclined electrodes
• • 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
  • H01M10/06—Lead-acid accumulators
• • 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
  • H01M4/14—Electrodes for lead-acid accumulators
  • H01M4/16—Processes of manufacture
  • H01M4/22—Forming of electrodes
• • 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
  • H01M6/42—Grouping of primary cells into batteries
  • H01M6/46—Grouping of primary cells into batteries of flat cells
  • H01M6/48—Grouping of primary cells into batteries of flat cells with bipolar 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

• the present invention relates to the field of electrical storage devices. More specifically, the present invention relates to a system and method for increasing the utilization efficiency of a lead - acid storage battery with the use of high sulfate pastes.
• the energy stored is proportional to the discharge voltage, which is about 2.08 volts per cell, and to the amount of lead species.
• Lead has a high atomic weight and is an inherently inefficient chemical for battery energy storage. Lead is also used for carrying current within the cell. As a result, the amount of lead required per kilowatt hour of storage may be 50 to 100 pounds, which unfavorably impacts both weight and cost of the storage system. This translates to an energy density of about 10 to 15 watt hours per pound, depending upon battery design, operation, and desired life.
• pastes applied to the electrodes has been practiced to increase the availability of the reacting materials.
• the vertical positive and negative plates of lead based alloy grids have been coated with layers of electrochemically active pastes.
• the paste on the positive electrode contains lead dioxide which is the positive active material, and the negative electrodes contain a sponge lead.
• batteries are formed where both electrodes are lead and act only as conductors, but where the paste alone acts as the electrode material which undergoes chemical change.
• Pb/Pb0 2 battery One conceivable way to form the Pb/Pb0 2 battery is to start with the components which would be present in a discharged battery, and apply a charge to form the Pb/Pb0 2 starting structures. With respect to the negative electrode, and the use of metallic lead, the sponge lead forms fairly easily. However, the Pb0 2 does not form as readily. In some cases PbO, lead monoxide, interspersed with some free lead can help begin to build the starting structure during the charging reaction. The PbO will form the first Pb0 2f to be followed by further Pb0 2 formation. The theory behind the formation of the battery in this manner is that the formed Pb/Pb0 2 starting structures will have an expanded structure, and therefore be more amenable to reaction during discharge.
• pastes as a starting material is particularly useful for the bipolar battery which may be formed by a series of stacked lead plates, typically with one side having the positive paste and the other side having the negative paste.
• An ion permeable separator typically separates the plates, and the plates themselves form the electrical interconnection between the cells.
• the use of pastes although increasing the active species and the overall surface area and availability of the active species, has had no significant effect in minimizing the mechanism described above which limits utilization of the electrodes.
• the pastes which have been used today have typically been a "leady” oxide paste, such as PbO interspersed with some elemental free lead.
• This paste is typically applied to the grids of conventional lead- acid batteries, the grids containing the active ingredients, namely Pb0 2 are pasted with a "leady oxide” which is primarily PbO containing a small amount of free lead. This is for the purpose of assisting in the charging reaction, as was previously discussed. This contrasts with other battery formulations, such as where two differing pastes are utilized as the beginning of formation of the reactive elements themselves during the charging reaction.
• the power output of the battery is significantly influenced by its state of discharge.
• the lead sulfate, especially near the positive electrode can grow into large, hard, angular crystals, which can dislodge active material from the electrodes, and can further impede the reduction to lead at the negative electrode.
• the addition of the tin dioxide can be accomplished as a pre-dispersed paste, or as a powder or coating onto a particulate or fibrous substrate, such as glass powder or glass wool. Further, the conductivity of the tin dioxide is greater than that of graphite. Stannic oxide additive is commercially available from Crystal Research of Olympia Washington.
• the battery composition should be such that the reactive materials are stable, and that the battery is re-chargeable without a serious reduction in the utilization.
• the system and process of the present invention is therefore to increase the specific energy of the lead- acid battery by using new starting pastes which will allow significantly higher utilization efficiencies of the positive and negative pastes.
• the invention enables the increased utilization efficiency of both electrodes, to thereby increase the specific energy of the battery.
• Two paste combinations, which are used to start the battery from its discharged condition, have been found to be advantageous.
• a battery has at its positive terminal, a lead sulfate (PbSO paste and at its negative terminal, a tribasic lead sulfate (3PbO ' PbS0 4 'H 2 0) .
• a paste of lead sulfate (PbSO is used at the positive electrode and while a monobasic lead sulfate (PbO-PbS0 4 ), applied to the negative electrodes.
• the material used is able.to form the proper amount of sulfuric acid during the charging cycle, which is set based upon expected utilization. Further, monobasic lead sulfate yields the least amount of resistance to reformation during the charging step.
• Figure 1 is a sectional view of a single cell structure which was utilized to construct single cell realizations of the present invention.
• This invention replaces, either partially or completely, the commonly used leady oxide with one, or possibly two, compounds of high sulfate content.
• the high sulfate content means that the starting material is already expanded and porosity is created when the lead compound is reduced to Pb at the negative electrode or oxidized to Pb0 2 at the positive electrode.
• Inventors in the past e.g., Pinsky, Cattley
• PbSO lead sulfate
• the chemical reactions for the positive and negative electrode reactions are:
• the sulfuric acid concentration of the electrolyte is increasing as the cell or battery is being formed.
• the initial electrolyte specific gravity needs to be at least 1.050 to 1.100 and with conventional pastes much higher than that since almost no sulfuric acid is produced on formation. Regardless of the starting pastes the specific gravity at the end of a full discharge should be in that range.
• pure PbS0 4 is the staring paste for both electrodes it is impossible to return to that initial specific gravity range without achieving 100% utilization efficiency at both electrodes. Nowhere near 100% efficiency has ever been achieved at either electrode. The effect will be that at full charge the acid concentration will be much too high and the electrolyte weight, and therefore the battery weight will be too high.
• both electrodes may be pasted with monobasic lead sulfate (PbO'PbS0 4 ), hereafter referred to as monobase.
• monobase monobasic lead sulfate
• Equation 6 illustrates again the formation of the components of a conventional lead - acid battery after the charging reaction.
• Table 1 shows a noteworthy comparison of molar volumes between the various lead species in a lead-acid battery.
• the molar volumes given here are cm 3 /raole of lead.
• Test cell 11 has an upper structure 13 jointed to a lower structure 15, typical with four bolts 17, although only a pair of bolts 17 secured with nuts 19.
• Each bolt 17 has an insulator 21 which extends substantially its length and insulates the bolts 17 from electrical contact with the electrodes.
• Electrode 23 is in electrical contact with the upper structure 13 while the electrode 25 is in electrical contact with the lower structure 15.
• electrode 25 has a greater tendency to separate from its electrode than does the negative electrode 23 paste.
• the electrodes 25 and 23 are kept horizontal, with the positive electrode 25 having an upwardly directed active surface.
• a space 27 is formed between the electrodes 23 and 25 which accommodates a positive paste 31, a negative paste 33 and a separator 35 which separates the pastes 31 and 33. It is understood that the separator 35 will be amenable to the transfer of the ionic species across its boundary in order to permit the chemical reaction to take place.
• the electrodes 23 and 25 may be made of metallic lead.
• the cell shown in the Figure 1, consisting of the electrode 23, the electrode 25 and the materials and structures therebetween may be stacked on other cells to form a multi-celled battery. Since the stacking of one lead electrode 25 atop another lead electrode 23 involves nothing more than electrical contact, adjacent cells in a multi-celled structure may share the same lead electrode.
• electrode 23 rather than abutting the upper structure 13 would have a positive paste 31 on its upper surface, followed by a separator 35, and then followed by another electrode having a negative paste 33 on its underside and a positive paste 31 on its upper side.
• positive paste 31 will be pure PbS0 4
• negative paste will be tribase (3Pb0'PbS0 4 'H 2 0)
• the remainder of the space will be occupied by the electrolyte, sulfuric acid (H 2 S0 4 ) and water.
• the starting components for the discharged battery, which will be charged to make the expanded density battery structures are as follows.
• Lead sulfate may be prepared by reacting litharge (PbO) with H 2 S0 4 . Litharge is added to a large excess of H 2 S0 4 at 50 to 70 ⁇ C and stirred vigorously for about three days, or until it becomes completely white. It is then filtered and washed.
• Tribase is made by stirring PbO in a large excess of water while adding a stoichiometric amount of 36% H 2 S0 4 dropwise for about two hours. The stirring must be continued until the material becomes all white, which is usually about 24 hours. This material is then filtered but need not be washed. The reaction for the tribase is carried out at room temperature.
• the preparation of monobase is quick and easy.
• the process is exactly like that for the tribase except that the acid is added dropwise for three hours, at which time the reaction is finished.
• the stoichiometric amount of acid is, of course, twice the required about for the tribase.
• the preferred orientation of the battery is for the plates to be horizontal.
• the pastes 31 and 33 may be water based with a water content of 20 to 25% water.
• the positive paste should have a conductive additive, such as conductive stannic oxide as was described for U.S. Patent No. 4,507,372, above, in order to provide optimum performance.
• the stannic oxide was combined with a glass fiber to enhance its structural stability and support. Typically such a stannic oxide preparation is made using about twenty five weight percent glass fibers and about seventy five weight percent stannic oxide.
• the battery paste 31 should contain an amount of the stannic oxide preparation added to their mass in a proportion of about twenty percent by weight of stannic oxide preparation to about eighty percent by weight of battery paste to make up the final paste 31.
• the final paste 31 will have a composition of about 80% by weight of paste mixture, 5% by weight of glass fibers and 15% by weight of stannic oxide.
• the paste mixture may or may not contain amounts of PbO, lead monoxide. It is contemplated that PbO may be used, even though the preferred starting materials will be pure. Varying amounts of PbO may be added to the paste mixture to adjust performance characteristics, such as the rate at which constituents are added to the electrolyte during the battery reaction.
• the negative paste may also have a sufficient amount of graphite fiber necessary to provide adequate conductivity at the desired discharge rate. Conductivity is important to avoid unwanted overvoltage type reactions occurring at the electrodes. In the overvoltage condition, oxygen may be produced at the positive electrode and hydrogen at the negative electrode.
• the negative paste 33 can accept a mix of graphite and expander to favorably affect its conductivity.
• the expander is usually composed of approximately equal weights of powdered graphite, barium sulfate, and lignosulfonates, each to the extent of about one percent by weight, as added to the negative battery paste.
• Graphite fibers are intermixed with the expander to the extent of about three percent by weight, with regard to the other constituents of the battery paste. These graphite fibers are usually about one to two microns in diameter and have a length ranging from about one hundred fifty microns to about one and a half millimeters in length.
• the graphite fibers and expander may be initially mixed to form a mixture of fifty percent by weight fiber and fifty percent by weight expander, before being added to the battery paste.
• the battery paste comprises a six percent mixture content with the remaining ninety four percent of the battery paste and additive comprising the pure battery paste before addition of the mixture.
• the expander used in the examples herein is grade 4640 commercially available from Anzon, Inc., Philadelphia, Pennsylvania.
• the graphite fibers are commercially available from Fortafil Fibers located in Rockwood, Tennessee. The graphite is never added to the positive electrode paste since it would be oxidized.
• Pasting frames which may or may not remain with the biplates, are used to both apply the pastes 31 and 33, as well as to determine the thickness of each electrode's paste. Once the frames are pasted and joined with the appropriate separator 35, and the electrolyte is added, the step of charging to form the charged battery can begin.
• Table 2 shows the performance of three typical cells which were formed by the method outlined above, by beginning with pastes and then charging.
• the figures represent real measurements except for the specific energies, which were based upon calculations which ignore the non-active component weight.
• These cells were made with pure PbS0 4 positive paste and pure tribase negative paste before being formed by charging.
• the electrodes were very thick; about 0.080" positives and 0.065" negatives. These thicknesses correspond to grids in conventional batteries of 0.080" plus 0.065".
• each of the identified cell numbers had an area of 47.7 cm 2 .
• the performance of the cells of Table 2 reflect five individual data runs.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Battery Electrode And Active Subsutance (AREA)

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• 1993
  • 1993-07-23 US US08/096,676 patent/US5368960A/en not_active Expired - Fee Related
• 1994
  • 1994-07-15 WO PCT/US1994/007975 patent/WO1995003636A1/en not_active Ceased
  • 1994-07-15 AU AU73356/94A patent/AU7335694A/en not_active Abandoned
  • 1994-08-05 TW TW083107181A patent/TW266333B/zh active

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