MAINTENANCE-FREE TYPE LEAD ACID

• US 3,862,861 A
• Filed: 05/30/1972
• Issued: 01/28/1975
• Est. Priority Date: 08/03/1970
• Status: Expired due to Term

• Current Assignee: Gates Energy Products, Inc. (Schneider Electric SE)
• Original Assignee: Donald H. Mcclelland, John L. Devitt
• Inventors: McClelland, Donald H., Devitt, John L.
• Primary Examiner(s): Skapars, Anthony
• Application Number:
  US05/257,719
• Time in Patent Office: 973 Days
• Field of Search: 136/26-27,178-179,176,36,13,65,67,6,3,163,6R
• US Class Current: 429/57
• CPC Class Codes: H01M 10/342 Gastight lead accumulators H01M10/121 takes precedence
• CPC Class Codes: H01M 2300/0005 Acid electrolytes
• CPC Class Codes: H01M 4/68 for use in lead-acid accumulators
• CPC Class Codes: H01M 4/685 Lead alloys
• CPC Class Codes: H01M 50/437 Glass
• CPC Class Codes: H01M 50/44 Fibrous material
• CPC Class Codes: H01M 50/489 Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
• CPC Class Codes: H01M 50/491 Porosity
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

This invention concerns a maintenance-free type lead acid cell which is in a normally sealed condition. The cell is characterized by structurally free, non-self-supporting plates separated from one another with highly absorbent flexible separators containing electrolyte and constrained within a container such that mechanical integrity is imparted to obtain a unitary self-supporting structure. Means are provided for maximum recombination of evolved gases and for discharge of excessively high pressure gas. A centroid element allows for operation in any indiscriminate attitude.

Claims

1. A MAINTENANCE-FREE TYPE LEAD ACID CELL WHICH SUSTAINS SUBSTANTIAL OVERCHARGE IN ANY INDISCRIMATE ATTITUDE OF THE CELL, SAID CELL OPERATING IN A NORMALLY SEALED CONFIGURATION UTILIZING AN "OXYGEN" CYCLE, COMPRISING:

NON-SELF-SUPPORTING LEAD BASED GRIDS HAVING A HIGH HYDDROGEN OVERVOLTAGE, SAID GRIDS PASTED WITH ACTIVE MATERIAL TO FORM POROUS POSITIVE AND NEGATIVE PLATES;

AN ELECTROLYTE ABSORBING AND RETAINING SEPARATOR MATERIAL CHARACTERIZED BY HAVING A HIGH HEAT OF WETTING AND INTIMATELY CONTACTING ADJACENT, OPPOSITE POLARITY PLATES AN ELECRROLYTE ABSORBED AND RETAINED BY SAID SEPARATOR AND BY SAID PLATES TO THE DEGREE THT NO FREE UNABSORBED ELECTROLYTE IID PRESENT IN THE CELL, SAID PLATES AND THIN LAYER OF ELECTROLYTE ON SAID ACTIVE MATERIAL SUFFICIENT TO SUSTAIN ELECTROCHEMICAL REACTIONS AT THE PLATES AND PERMITTING OXYGEN TRANSFER TO AND FROM THE ACTIVE MATERIAL THROUGH A VOID VOLUME FORMED IN SUBSTANTIALLY ALL OF THE PORES OF SAID PLATES, SAID TIN LAYER OF ELECTROLYTE UNIFORMLY DISTRIBUTED THROUGHOUT SAID PLATES AND SAID VOID VOLUME FORMED BY VIRTUE OF THE PRESENCE OF ONLY THE THIN LAYER OF A ELECTROLYTE ON THE ACTIVE MATERIAL, AND A CONTAINER TIGHTLY CONTRASTING SAID PLATES, SEPARATOR AND ABSORBED ELECTROLYTE UNDER FIRM STACKING PRESSURE TO FORM S SELF-SUPPORTING INTEGRAL CELL.

2. A cell according to claim 1 in which the lead utilized in the grids is of greater than about 99.9 percent by weight purity and contains no material to increase rigidity with accompanying degrees of reduction of hydrogen or oxygen overvoltage.

3. A cell according to claim 1 in which each of said positive and negative plates comprises a continuous, unitary, pliable, structurally free lead sheet, forming a grid for said plates.

4. A cell according to claim 1 in which a gas venting means having a vent exit is inserted into the cell to a point such that the venting exit is disposed at substantially the centroid of the cell. is further a valving means disposed over said vent normally biased in a closed position to retain generated gas at a positive pressure within said cell.

5. A cell according to claim 3 in which separator material is disposed between each of said positive and negative plates prior to insertion within said container;

said plates and separator material separating said plates tightly and spirally wound into a spiral configuration.

6. A cell according to claim 1 having additionally edge surfaces of active material on said plates to aid in the recombination of gas.

7. A cell according to claim 1 in which there is disposed between the container and the stacked plates, separator and electrolyte subassembly, an electrically insulated liner material electrically separating said plates, separator and electrolyte subassembly from said container.

8. A cell according to claim 1 in which a hydrophobic paste is incorporated within the negative plate to minimize the degree of wetting of the plate by the electrolyte.

9. A cell according to claim 6 in which separator material extends beyond the edge surface of the lead plates, said extended portion of the separator treated to be rendered hydrophobic thereby minimizing the degree of wetting of said extended to to allow for maximum portion to allow for maximum availability of generated gases to recombine with the edge surfaces of the plates.

10. A maintenance-free type lead acid cell operating under superatmospheric internal pressure and in a normally sealed configuration utilizing an '"'"''"'"''"'"''"'"'oxygen'"'"''"'"''"'"''"'"' cycle comprising:

lead based grids having a high hydrogen overvoltage and in which the lead utilized in the grids is of greater than about 99.9 percent by weight purity, said grids pasted with active material to form porous positive and negative plates;

an electrolyte absorbing and retaining separator material having a high heat of wetting, high surface area and porosity of about 85 to 95 percent, intimately contacting adjacent opposite polarity plates;

a liquid electrolyte absorbed and retained by said separator and by said plates to the degree that no free unabsorbed electrolyte is present in the cell;

said plates containing a thin layer of electrolyte on said active material sufficient to sustain electrochemical reactions at the plates and permitting oxygen transfer to and from the active material through a void volume formed in substantially all of the pores of said plates, said thin layer of electrolyte uniformly distributed throughout said plates and said void volume formed by virtue of the presence of only the thin layer of electrolyte on the active material; and

a container encapsulating and tightly constraining said plates, separator and absorbed electrolyte under firm stacking pressure to form a self-supporting integral cell capable of use under any attitude.

11. A cell according to claim 10 in which the electrolyte is present in a relatively starved amount.

12. A maintenance-free type lead-acid cell operating in a normally sealed configuration utilizing an '"'"''"'"''"'"''"'"'oxygen <

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cycle including at least one porous positive plate, aT least one porous negative plate, a liquid electrolyte in a starved amount, and a separator material, in firm pressure contact with the plates, which separator absorbs and retains all the electrolyte except for the presence of a thin layer of electrolyte distributed on the walls of substantially all of the pores uniformly throughout the active material of the cell plates, said pores which carry said thin film of electrolyte being free of electrolyte except for said thin film, allowing the cell to be utilized in any position without leakage of electrolyte and permitting the cell to sustain substantial overcharge rates by improved avenues for oxygen transport and recombination within the cell.

13. A cell according to claim 12 in which the separator is a non-woven, fiber glass matting having a high degree of wettability.

14. A cell according to claim 13 in which the fibers of the fiber glass have a diameter in the range of from about 0.2 to about 10 microns.

15. A cell according to claim 13 in which the fibers of the fiber glass have a surface area between about 0.1 to 20 square meters per gram of silica.

16. A cell according to claim 12 in which the separator material has a porosity in the range of 85 to 95 percent.

17. A cell according to claim 12 in which the separator is a non-woven, fiber glass matting having a porosity between about 85 and 95 percent and wherein the fiber diameter of the fibers of the fiber glass is in the range of about 0.2 to 10 microns and has a surface area in the range of about 0.1 to 20 square meters per gram of silica.

18. A cell according to claim 12 in which said positive and negative plates comprise non-self-supporting lead based grids having a high hydrogen overvoltage.

19. A cell according to claim 18 wherein said plates, separator and absorbed electrolyte are constrained tightly under firm stacking pressure to form a self-supporting integral cell.

20. A cell according to claim 18 in which the lead utilized in the grids is of greater than about 99.9 percent by weight purity and contains no materials to increase rigidity with accompanying degrees of reduction of hydrogen or oxygen overvoltage.

21. In a maintenance-free normally sealed lead-acid electrochemical cell operative without significant hydrogen evolution comprising at least one porous pasted negative plate, at least one porous pasted positive plate, both plates utilizing non-self supporting high purity lead grids, liquid acid electrolye, electrolyte absorbing and retaining separator, and a container encapsulating the plates, separator and included electrolyte under firm stacking pressure, the improvement comprising the following features:

a. electrolyte present in a starved amount so that there is no free electrolyte in the cell, substantially all of the electrolyte being absorbed within the interstices of the separator except for a small amount of electrolyte present as a thin layer on the surface of a substantial portion of the pores uniformly distributed throughout the plates producing an electrolyte-free void volume in said pores; and

b. porous separator material having a high heat of wetting and high surface area and in intimate contact with the plates, said properties of the separator together with the presence of only the starved amount of electrolyte and firm stacking pressure causing the separator to wick electrolyte from the plates whereby the thin layer of electrolyte in the plates is obtained, said substantial portion of the pores having said thin layer of electrolyte on the walls of the pores being sufficient in amount to enable improved oxygen access to the negative plate for recombination therewith at significant rates of overcharge.

22. A maintenance-free type lead-acid cell operating under the oxygen cycle capable of withstanding substantial rates of overcharge comprising:

lead based grids having a high hydrogen overvolTage and in which the lead utilized in the grids is of greater than about 99.9 percent by weight purity, said grids pasted with active material to form porous positive and negative plates;

a porous electrolyte absorbing and retaining separator composed of a matting of fiber glass in which the fibers have a diameter in the range of from about 0.2 to about 10 microns;

acid liquid electrolyte absorbed and retained by said separator and by said plates to the degree that no free unabsorbed electrolyte is present in the cell, said plates containing a thin layer of electrolyte on said active materials permitting oxygen transfer to the negative material from the positive active material through a void volume formed in substantially all of the pores of said plates, said thin layer of electrolyte uniformly distributed throughout said plates and said void volume formed by virtue of the presence of only the thin layer of electrolyte on the active material; and

a container encapsulating and tightly constraining said plates separator and absorbed electrolyte under firm stacking pressure to form a self-supporting integral cell capable of use under any attitude.

23. A maintenance-free normally sealed lead-acid electrochemical cell operative without significant hydrogen evolution comprising at least one porous pasted negative plate, at least one porous pasted positive plate, both plates utlizing non-self-supporting high purity grids, liquid acid electrolyte, electrolyte absorbing and retaining separator, and a container encapsulating the plates, separator and included electrolyte under firm stacking pressure, in combination therewith the improvement comprising:

a. electrolyte present in a starved amount so that there is no free electrolyte in the cell, substantially all of the electrolyte being absorbed within the pores of the separator except for a small amount of electrolyte present as a thin layer on the surface of the pores of the plate; and

b. separator material having a high heat of wetting and high surface area and in intimate contact with the plates.