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
  • H01M4/14—Electrodes for lead-acid accumulators
  • H01M4/16—Processes of manufacture
  • H01M4/20—Processes of manufacture of pasted 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
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/56—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of lead
• • 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
  • H01M4/68—Selection of materials for use in lead-acid accumulators
  • H01M4/685—Lead alloys
• • 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
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49002—Electrical device making
  • Y10T29/49108—Electric battery cell making
  • Y10T29/4911—Electric battery cell making including sealing
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49002—Electrical device making
  • Y10T29/49108—Electric battery cell making
  • Y10T29/49115—Electric battery cell making including coating or impregnating

Definitions

• the present invention relates to the field of lead-acid electrochemical cells, and more particularly to a lead- acid cell paste formulation including tin compounds and methods of manufacturing and using the same in an electrochemical cell.
• each positive electrode in known valve-regulated lead-acid (VRLA) batteries, each positive electrode, sometimes called a positive "plate,” includes a grid or foil sandwiched between an electrochemically active paste. A number of positive electrodes are alternately interleafed with a number of negative electrodes, sometimes called the negative "plate,” with each electrode of one polarity separated from the adjacent electrode of opposite polarity by a porous separator material, typically a glass microfiber mat.
• the cell is completed by adding electrolyte and subjecting it to a formation charging process that activates it.
• the entire apparatus is typically contained within a suitable plastic case or other container.
• the interface between the grid or foil and the paste is known as the corrosion layer. While all of the chemistry/electrochemistry that takes place here is not well understood, the establishment of a strong, well- defined corrosion layer is felt to be necessary for long cycle life in lead-acid batteries. With some grid/foil alloys, in particular pure lead, lead/calcium and lead/low tin compositions, there is not sufficient corrosion to establish a strong layer and in place of this a so-called "passivation" layer is created by alkaline oxidation of the grid/foil surface. This corrosion/passivation layer is composed primarily of PbO which is protected from neutralization by the sulfuric acid electrolyte by a layer of mixed lead compounds, but primarily lead sulfate.
• This corrosion/passivation layer acts as a perm-selective membrane that allows the underlying PbO to exist in an alkaline environment.
• This corrosion/passivation layer can act as an electrical insulator or at least reduce the conductivity between the grid/foil and the active material paste and thus can have a dramatic impact on the electrochemical properties of the cell.
• the corrosion/passivation layer appears to play an integral role in at least two important characteristics of cell performance: self-discharge and cycle life.
• self discharge refers to a series of different chemical reactions within the cell that can reduce the storage time, or shelf life, due to consumption of electrolyte.
• the open-circuit voltage directly reflects the specific gravity, or concentration of electrolyte within the cell, and it is also linearly proportional to discharge capacity. Any self-discharge reaction that consumes electrolyte reduces both storage time and discharge capacity. Corrosion of the positive grid/foil on open-circuit stand is one mode of self discharge and does consume electrolyte.
• cycle life refers to the number of usable cycles of discharge and recharge available from the cell. The cycle life figure is dependent upon a number of conditions under which it is determined, as well as the basic cell construction.
• a cell which achieves 80% of its initial amp-hour rating after 500 cycles and reaches 50% after 1,000 cycles will have two different "cycle life" values, depending upon the criterion used for termination (80 or 50% of initial capacity) .
• Another measure, related to cycle life, is total usable capacity. This term refers to the sum of the cycles over the life of the cell multiplied by the amp-hours at each cycle. It can also be expressed as the area under the curve produced by a plot of data showing discharge capacity (in amp-hours) versus cycle number.
• both the grid/foil and the active material include lead in various compositions along with smaller quantities of other materials.
• tin and tin compounds have been used in lead-acid electrochemical cells.
• U.S. Pat. No. 5,368,961 discloses a cell having a grid alloy of about 2.5% tin. The use of tin in previous cells has generally been confined to having it in the grid/foil metallic alloy, as opposed to including some form of tin in the paste.
• This tin acts as a conductor to ameliorate the insulative effects of the passivation layer and to thereby enhance the conductivity, and thus the current flow, between the grid/foil and the positive active material.
• tin percentages at or below about 1.1-1.3%, true alloys are formed and the tin distribution is relatively uniform. Above about 1.3%, the solubility of tin in lead is exceeded and the grain boundaries and the grains contain relatively high concentrations of tin. In the former case, passivation layers tend to form and dominate cell performance due to the low amount of corrosion of the grid/foil and, hence, low levels of tin compounds in the passivatio ⁇ layer.
• grids/foils having 2-3% tin levels have certain desirable performance characteristics, in comparison with grids/foils such as pure lead or those having about 0.5% tin or less.
• a cell with a positive grid/foil with 2-3% tin provides very good cycling performance, i.e., the cell is able to produce many discharge/recharge cycles with good capacity and a high total usable amp-hours.
• such a cell has an undesirably high self-discharge rate such that the storage time is unacceptable for most commercial applications. It is believed that this high self- discharge rate is due to corrosion of the high tin areas and the grain boundaries, thus consuming significant quantities of the sulfuric acid electrolyte and thereby increasing the rate of decrease of the open-circuit voltage.
• Cells with grids/foils having about 1% tin or less exhibit much improved self-discharge characteristics, but do not provide the excellent cycle life of cells having grids/foils with 2-3% tin. Because they are true alloys, it is believed that the foils with 1% tin or less have a much reduced corrosion rate compared to the foils with 2- 3% tin. It is believed that this is due to the tin distribution being more or less homogeneous in the true alloys, with no areas of high tin concentrations in the bodies of the grains and a low level of tin enrichment in the grain boundaries (relative to 2-3% tin foils) . The 1% tin (or less) foils thus reduce the self-discharge levels of the cells due to limited tin corrosion, but because of this they do not release sufficient tin into the corrosion/passivation layer to improve markedly the cycling performance.
• the experimental results in the Japanese publication were also less than dramatic for tests conducted after a 10 month storage period.
• the prior art test cell showed an initial voltage on high-current load of 1.23V and a self-sustaining period until l.OOV of 3 min. 25 sec, while the cells in accordance with the asserted invention showed an initial load voltage of 1.27 to 1.50V and a self-sustaining period until l.OOV of 3 min. 35 sec. to 3 min. 47 sec.
• the Japanese publication teaches that the addition of
• SnS0 4 or SnO is to occur prior to the addition of sulfuric acid:
• SnS0 4 of varied particle sizes 200-400 meshes and under 400 meshes was added to the lead powder in the ratio of 0.5-3% and was fully mixed before adding sulfuric acid.
• tin in the form of SnS0 4 or SnO or metallic powdered tin, is introduced into the positive paste material. Different concentrations of tin may be used. It has been observed that paste having 0.3 weight percent soluble tin sulfate combined with plate foils having 1% tin produces good results. It is expected that adding tin to the paste will produce good results with foils having lower tin contents, or even with foils having no tin whatsoever such as substantially pure lead.
• foils have very low corrosion rates, and thus result in cells with low self-discharge rates. However, they also tend to form a passivation layer between the foil and positive active material, resulting in very short cycle life.
• the invention may also utilize elements other than tin such as compounds containing antimony, arsenic, germanium, indium, selenium, gallium, tellurium or other semiconductors or combinations thereof.
• tin to the active material is believed to serve two purposes that dramatically increase cycle life while having no detrimental effect on self discharge.
• tin will be incorporated within the passivation layer and by its semiconductor action will allow electronic conduction through the normally poorly- conducting PbO passivation layers.
• the soluble tin distributed throughout the positive active material will be converted to Sn0 2 during formation. This Sn0 2 will plate out on the electroactive lead dioxide active material and will provide a conductive "skeleton" that will result in slightly higher discharge capacity and longer cycle life. It has been determined unexpectedly that the process by which the tin is incorporated into the paste is critical to improving the performance of the cell along the lines described above.
• Tin in the form of SnS0 4 or other forms must be introduced after the sulfuric acid is added to the paste. It has been found that adding the tin prior to the introduction of sulfuric acid results in an unsuitable paste that performs poorly relative to pastes mixed by the introduction of tin after the addition of sulfuric acid. For paste mixes that do not require the addition of sulfuric acid (i.e., so-called "unsulfated" pastes) the tin form used can be introduced at any time during mixing.
• FIGS. 1-3 are test results of amp hours at various cycles for cells with tin-containing pastes according to the present invention.
• FIGS. 4-6 are comparative test results for cells similar to the cells of FIGS. 1-3, but with non-tin- containing pastes.
• FIG. 7 is a diagrammatic cross section of alternating electrode positive plates of an embodiment of the invention.
• FIGS. 8-11 are test results for several cells in accordance with the present invention having positive electrodes with various tin content.
• a lead-acid cell includes positive electrodes or "plates” 10, interleafed with negative electrodes or “plates” 22.
• the positive and negative plates are separated from one another by a separator 20.
• the electrodes may be arranged in any physical configuration with respect to one another. Commonly used configurations are to combine a series of stacked electrode plates, or to spirally wind a continuous positive electrode with a continuous negative electrode separated by a porous separator (known as the "spirally wound" configuration) .
• the positive electrodes are electrically connected to a common positive terminal, and the negative electrodes are electrically connected to a negative terminal. The combination is enclosed within a case containing electrolyte (not shown) .
• the cell is of the TMF brand thin metallic film type, as disclosed in U.S. Patent No. 5,368,961 by Juergens.
• the Juergens design utilizes very thin plates on the order of 0.01 inches or less in thickness, with film thickness on the order of 0.005 inches or less.
• the "plate” is used to refer to the metallic film in combination with the paste coated thereon.
• Juergens type lead acid cells are characterized by exceptionally high discharge and charge rates, and are well suited to the system of the present invention.
• the present invention is not limited to Juergens type thin plate cells, and is applicable in general to lead acid cells.
• the positive electrode 10 of the present invention includes a film 12 coated on each side by active paste material 14.
• the film 12 is preferably a lead-tin alloy, having about 1% tin.
• the amount of tin may be varied without departing from the scope of the invention. For example, films of up to 3% or more tin may be feasible, and films of less than 0.5% tin or even substantially pure lead may be feasible.
• the active paste material 14 preferably includes a mixture of dispersant, sodium sulfate, sulfuric acid. lead oxide, tin sulfate, tin oxide, tin(II) salts or tin (IV) salts or combinations thereof. A content of 0.3% tin sulfate by weight has been found to provide good results. Alternate embodiments of the invention substitute metallic tin for tin sulfate or tin oxide. It is possible that tin introduced via other compounds may also provide acceptable results. Further, similar compounds containing antimony, arsenic, germanium, indium, selenium or combinations thereof in place of or in addition to tin may produce acceptable results.
• Sulfuric acid is added into the bulk of the water.
• Lead oxide is added following the sulfuric acid addition which then reacts with the sulfuric acid to produce lead sulfate.
• lead oxide is added following the sulfuric acid addition which then reacts with the sulfuric acid to produce lead sulfate.
• 1/3 of the total lead oxide is introduced the sulfuric acid is nearly completely reacted.
• Tin sulfate is pre-dissolved in water.
• the tin ion and sulfate ion, now resident in the water, are added to the mix after 2/3 of the lead oxide has been introduced. The remainder of the lead oxide is added to complete the mix operation.
• Positive paste is " applied onto a 2" wide, 15.125" length foil covering an area 1.9" wide by 15.125" in length on both sides with a target applied active material weight of 11.1 grams, for .008" thickness.
• FIGS. 1-6 comparatively illustrate the performance of Juergens-type thin metal film cells according to the present invention and Juergens-type thin metal film cells not having any tin additives in the paste.
• the capacity of the cells (in amp hours) are plotted as a function of the number of times that the cell is cycled (i.e., discharged and recharged) .
• the discharges were at the 8C rate and the depth of discharge was 100%.
• the number of cycles multiplied by the amp hours obtained for each cycle yields the total useable capacity of the cell. Cycling is not continued after the amp hours of a cell falls below a nominal percentage of the initial amp hours of the cell, typically 80% or 50%.
• FIGS. 1-3 illustrate cycle performance of Juergens-type thin metal film cells having positive films including 1% tin, and positive active paste including 0.3% tin sulfate.
• the batteries tested in FIGS. 1-3 all achieved over 440 cycles of at least 80% of initial amp hour values, and achieved over 740 cycles of at least 50% of initial amp hour values.
• FIGS. 4-6 illustrate cells similar to the cells of FIGS. 1-3, except that tin sulfate has not been added to the active paste.
• the cells of FIG. 6 all reached less than 170 cycles at 80% of initial amp hours, and less than 210 cycles at 50% of initial amp hours.
• the positive electrode may also contain tin as part of a lead/tin alloy. It is believed that the optimum amount of tin in the lead/tin alloy of the positive electrode is on the order of 1%. This figure is based on experiments conducted on cells not having any tin in the paste, which are described below, but it is believed that cells with tin in the paste will produce similar results in this regard.
• FIGS. 8-11 The self discharge performance of cells having varying amounts of tin in lead/tin alloy electrodes is shown in FIGS. 8-11. All data in these four graphs are from cells with paste material not having any tin compounds.
• the vertical axis on each graph shows open cell voltage in volts, and the horizontal axis shows the number of elapsed days since formation.
• FIG. 8 shows the self discharge of a set of 16 test samples having positive electrodes of a lead/tin alloy with approximately 1% tin by weight.
• the test samples are labeled "Series 1, Series 2. . . .”
• the cells for which the data of FIG. 8 was collected were stored at room temperature. It can be seen that there is no appreciable drop-off in open circuit voltage for any of the test samples over a storage period of 180 days.
• FIG. 9 shows the self discharge of 4 test samples stored at room temperature over a period of 180 days, where the test samples had positive electrodes of lead/tin alloys with approximately 3% tin.
• the pertinent distinction between the cells of FIG. 8 and the cells of FIG. 9 was the tin content of the positive electrodes; the cells of FIG.
• FIG. 11 shows that the self discharge performance is less favorable if the positive electrodes contain 3% rather than 1% tin.
• the three test samples of FIG. 11 are essentially the same as those of FIG. 10, except that the positive electrode of the FIG. 11 cells is approximately 3% tin. It can be seen that the open circuit voltage of the FIG. 11 cells drops off abruptly at 40 to 60 days under 50°C storage.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Battery Electrode And Active Subsutance (AREA)
• Cell Electrode Carriers And Collectors (AREA)
• Secondary Cells (AREA)
• Preparation Of Compounds By Using Micro-Organisms (AREA)

Priority Applications (5)

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Publications (1)

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Citations (2)

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• 1996
  • 1996-09-20 US US08/717,279 patent/US5820639A/en not_active Expired - Fee Related
• 1997
  • 1997-09-15 JP JP51478498A patent/JP4444373B2/ja not_active Expired - Fee Related
  • 1997-09-15 DE DE69737770T patent/DE69737770T2/de not_active Expired - Fee Related
  • 1997-09-15 AT AT97941073T patent/ATE363738T1/de not_active IP Right Cessation
  • 1997-09-15 CA CA002266595A patent/CA2266595A1/en not_active Abandoned
  • 1997-09-15 WO PCT/US1997/016278 patent/WO1998012760A1/en not_active Ceased
  • 1997-09-15 AU AU42706/97A patent/AU719061B2/en not_active Ceased
  • 1997-09-15 EP EP97941073A patent/EP0931360B1/en not_active Expired - Lifetime
  • 1997-12-24 US US08/998,421 patent/US6117196A/en not_active Expired - Lifetime
• 2001
  • 2001-05-16 US US09/859,963 patent/US20020068219A1/en not_active Abandoned
• 2003
  • 2003-04-11 US US10/412,926 patent/US6833216B2/en not_active Expired - Fee Related

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