GB2090696A

GB2090696A - Battery plate manufacture

Info

Publication number: GB2090696A
Application number: GB8138485A
Authority: GB
Original assignee: Gould Inc
Current assignee: Gould Inc
Priority date: 1980-12-29
Filing date: 1981-12-22
Publication date: 1982-07-14
Also published as: AU7901181A

Abstract

A battery plate manufacture wherein a separator sheet of e.g. glass- fibre is secured to the paste material defining the surface layer of the positive electrode by embedment of projecting elements of the separator sheet in the surface portion of the paste layer. The projecting portions are preferably urged into the surface portion while the paste material is in an unset condition. Subsequent setting of the paste material locks the embedded projecting elements therein to secure the sheet to the surface.

Description

SPECIFICATION Battery plate manufacture BACKGROUND OF THE INVENTION Field of the invention This invention relates to battery plate manufacture and in particular to the manufacture of battery plates having a permeable separator cover sheet on the active surface material.

Description of the prior art In U.S. Letters Patent 3,253,954 of Henry J. Banas, which patent is owned by the assignee hereof, a method of applying a protective sheet to a plate-like positive battery electrode is disclosed wherein the sheet comprises a sheet of woven synthetic fiber, such as Dynel. The Dynel material is heat-shrinkable and the sheet is provided in the form of a loosely fitting envelope which is shrunk onto the plate by subjecting the envelope to heat, thereby to cause a tight fit with the plate.

In U.S. Letters Patent 2,934,585 of Harold E. Zahn, which patent also is owned by the assignee hereof, insulative envelopes are provided to function as separators between adjacent electrodes of opposite polarity. The envelope includes a pair of insulative panels having portions extending beyond the plate heat sealed together to form imperforate reinforcing flanges around the plate. The flanges are interrupted at intervals to permit passage of electrolyte therethrough.

Kenneth A. Anderson discloses, in U.S. Letters Patent 4,026,000, an apparatus for enveloping battery plates within porous separators wherein the plates are engaged with a fold in the separator sheet.

Rollers are provided for compressing the sides of the separator against the opposite sides of the battery plate and the edges of the envelope are ultrasonically sealed to form the desired envelope around the battery plate.

In U.S. Letters Patent 4,080,727, William H. Stolle et al show a method and apparatus for assembling sheets of battery plate separator material over the battery plates in envelope fashion, with the side edges thereof sealed to form the desired envelope.

William J. Eberle discloses, in U.S. Letters Patent 4,080,732, an enveloperforwrapping the battery plates to define envelopes having sealed edges.

Camillo M. Vecchiotti et al, in U.S. Letters Patent 4,125,424, show an apparatus for fabricating battery plate sleeves of microporous plastic sheet material bonded to intermediately dispose sealing strips by solvent welding or solvent adhesive bonding. The envelope is formed in continuous lengths and is cut to the appropriate length for each battery plate.

Additional means for packaging objects from thermoplastic sheet material are illustrated in U.S.

Letters Patent 3,303,629 of C. J. Tobin and 3,989,579 of Gary L. Sheldon.

Summary of the invention The present invention comprehends an improved battery plate manufacture wherein a porous separator sheet is secured to the active paste layer of the battery plate by embedment of projecting portions of the sheet in the outer surface of the paste layer.

In one embodiment, the invention comprehends applying the sheet of the outer surface of the active paste material while the active paste material is in freshly pasted condition so as to readily receive the projecting elements.

In another embodiment, the sheets are applied to dried pasted plates, the sheets are compressed against the pasted plates during the plate formation process and the fibers become embedded in the paste during the formation process.

In the illustrated embodiment, the separator sheet is made of an oxidation resistant, fibrous material, such as fibrous borosilicate glass, forming a paperlike webb wherein at least one surface is provided with projecting fibers. Such glass materials, having preferable characteristics for use in an acid environment, are well known to those skilled in the art.

The sheet material may be urged against the freshly pasted active material as by urging a roller thereagainst. The assembly may then be delivered to an apparatus for setting the paste material which, in the illustrated embodiment, comprises an oven which flash-dries the paste material; however, other methods may also be used.

The covering sheet material of the completed electrode plate construction is firmly bonded to the active paste material serving to retain the paste material on the supporting member while yet permitting free flow of the electrolyte therethrough.

In the illustrated embodiment, the separator sheet material comprises a thin, highly porous material having very small pore size.

In the illustrated method of fabricating the plate construction, the separator sheet material extends around one edge of the plate so as to have opposite portions thereof facially engaged with the opposite surfaces of the pasted plate, whereby both surfaces of the plate are covered by the sheet material concurrently, thereby reducing the concentration of lead dust in the working environment.

The battery plate manufacture of the present invention is extremely simple and economical while yet providing the highly desirable features discussed above.

Brief description of the drawing Other features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawing wherein: Figure 1 is a schematic side elevation of an apparatus for carrying out the improved method of manufacture of a battery plate construction embodying the inventon; and Figure2 is a fragmentary vertical section through the completed battery plate construction illustrating the interlocking of the protective separator sheet portions to the active paste layers.

Description of the preferred embodiment In the exemplary embodiment of the invention as disclosed in the drawing, a battery plate construction generally designated 10 comprises an improved lead-acid battery positive electrode plate advantageously adapted for extended-life deep cycling use. In the conventional flat plate electrode, the active material tends to become separated from the electrode during normal use. A number of attempts have been made as discussed above to solve this problem by forming envelopes around the plate.

The envelope material of the prior art has included felted fibers of synthetic resin, synthetic resin sheeting, glass mats, etc. Where glass mats have been utilized, they have been bonded to the electrode with cement and have added not only substantial expense in the fabrication of the electrode, but have increased the bulk of the electrode substantially with an accompanying reduction in capacity of the battery.

As shown in Figure 2, the battery plate construction 10 of the present invention comprises a sheet 11 of porous separator material retained on the outer surface portion 12 of the active paste layer 13 carried on the electrode supporting member 14 of the battery plate.

As shown in Figure 2, the plate construction is preferably symmetrical about the central plane thereof so as to define an opposite active layer 13' and covering protector sheet 11' similar in construction and arrangement to that of layer 13 and sheet 11.

As illustrated in Figure 2, layer 11 preferably comprises a paper web or sheet formed of fibers, such as glass fibers 15. The sheet defines an inner, or plate contact, surface 16 having a distributed plurality of elongated elements, i.e. the distal ends 17 of fibers 15, which project into the outer surface portion 12 of active layer 13.

The invention comprehends urging the fiber portions 17 into active surface portion 12 while the active surface portion is readilyyieldable, permitting the fiber ends to be embedded as a result of simple urging of the sheet 11 against surface portion 12.

More specifically, the fiber ends 17 are urged into the surface portion 12 while the layer 13 comprises a freshly pasted layer on the electrode supporting plate or grid member 14.

Upon setting of the surface portion 12, fiber ends 17 are firmly bonded in the embedded relationship therewith so as to effectively positively retain sheet 11 in facial engagement with the surface portion 12.

The invention comprehends that separator sheet 11 be formed of a highly porous material having pores of extremely small size. In one example, a sheet having a mean pore size of 7 microns performed satisfactorily. In the illustrated embodiment, the fibrous glass web defines a sheet having a porosity in the range of approximately 75% to 90% with the pores thereof having a mean cross-sectional size in the range of 0.5 to 20 microns. It has been found that such a porous construction provides for free flow of the battery electrolyte to and from the active surface portion 12, while yet the active surface portion is effectively retained against separation from the layer 13 for extended, long trouble-free life of the battery notwithstanding deep cycling thereof and other rigorous use of the battery.

In the illustrated embodiment, the active layer 13 is comprised of a paste of lead oxide, sulfuric acid and water. The electrode supporting member 14 preferably comprises a conventional lead or lead alloy grid structure. The freshly pasted layer 13 defines a relatively yieldable surface portion 12 as a result of the softening action of the water therein.

The setting of the surface portion 12 is readily effected by drawing the water therefrom as by subjection thereof to an elevated temperature.

In the illustrated embodiment, the separator sheet is made to be relatively thin, such as in the range of approximately .008" to .040". Notwithstanding the extremely thin configuration of the separator sheet, the improved bonding thereof to the active layer has been found to provide an excellent long life, troublefree electrode plate construction. For example, a test cell, constructed with electrode plates in accordance with the present invention, delivered 275 cycles whereas an identical cell, containing electrode plates not embodying the construction of the present invention, delivered only 150 cycles. This represents an improvement of 83% in cycle life in a cell using the present invention as compared with cells using conventional electrode plates.

As illustrated in Figure 1, the battery plate construction 10 may be constructed in an extremely simple and economical manner by feeding the supporting grid member 14 sequentially to a pasting apparatus 19 applying the paste layers 13 and 13' to the opposite surfaces of the grid 14. The freshly pasted plate is urged into the mid portion 20 of a cut sheet 21 separated from a supply web 22 of the fibrous glass paper material. As shown in Figure 1, the leading edge of the freshly pasted plate engages the inner surface 16 of the cut sheet. As the plate advances from left to right, as depicted by arrow 27, it causes the cut sheet 21 to fold and wrap about the pasted plate as a result of engagement of the sheet with suitable guide members 23.

The sheet-wrapped plate is conveyed to a roller means generally designated 24 which urges the folded sheet into facial engagement with the opposite surfaces of the pasted plate so as to effect the desired embedment of the projecting fiber ends 17 to the yieldable surface portions 12 and 12' of the active layers 13 and 13', respectively.

The wrapped and pressed electrode structure 25 is then delivered to a suitable setting apparatus illustratively comprising a flash-drying oven 26, which, as discussed above, rapidly removes sufficient water from the surface portion 12 to effect a setting thereof effectively bonding the projecting fiber portions 17 to the active layer 13 to define the desired completed battery plate construction 10.

As is conventional, the battery plate construction 10 may be further cured prior to installation in the desired battery structures. Such curing may further set the active layers so as to further assure positive bonded retention of the separator sheets thereto.

An alternative method for embedding the glass mat fibers in the active paste of the electrode plates is by wrapping dried pasted plates with glass webs or mats; the glass web is compressed against the pasted plate while the active material of the plate is being charged or formed. During the formation of the active material, the fibers will be embedded in the electrode plate structure by the normal changes which occur in the particle structure of the electrode plate during formation. As an example, a test cell incorporating electrode plates of the present invention had a cycle life of 57 cycles whereas an identical cell not incorporating the features of the present invention had a cycle life of only 35 cycles, thus the cell incorporating the present invention showed an improvement in cycle life of 62% over the conventional or control cell.

Elimination of the relatively expensive bonding materials and heat sealing operations heretofore utilized in the art provides a substantial improvement in the economy of manufacture of the battery plate construction. Further, the improved, positive embedment of the fibrous surface portion of the separator sheet material permits the sheet material to be extremely thin and highly porous while yet positively retained in association with the active layer. Thus, the invention permits the improved positive retention of the active layer material with effectively minimum weight and bulk.

The foregoing disclosure of specific embodiments is illustrative of the broad inventive concepts comprehended by the invention.

Claims

1. The method of making a battery plate comprising the steps of: providing a layer of active paste material to an electrode supporting member to define a pasted plate; providing a sheet of porous separator material having a plate contact surface provided with a plurality of distributed elongated elements projecting therefrom; urging said sheet surface against said pasted plate to embed said elements in said paste layer; and treating the sheet covered pasted plate to cause the embedded elements to be effectively permanently retained in said paste layer.

2. The method of making a battery plate of Claim 1 wherein said step of urging said sheet surface comprises a step wherein said separator sheet is urged against said pasted plate substantially individually upon the provision of the paste to said supporting member.

3. The method of making a battery plate of Claim 1 wherein said step of treating the sheet comprises a step of flash-drying the assembly.

4. The method of making a battery plate of Claim 1 wherein said step of urging the sheet comprises a step of pressing a rollerthereagainst.

5. The method of making a battery plate of Claim 1 wherein said paste layer is disposed on each of opposite faces of said electrode supporting member and said sheet is uged concurrently against the layer on each of said faces to effect concurrent embedment of said projecting elements therein.

6. A battery plate construction comprising: an electrode supporting member; a layer of active paste material on said electrode supporting member; and a sheet of porous separator material having a plate contact surface provided with a plurality of distributed elongated elements projecting therefrom embedded in said paste layer comprising means for causing said sheet to be effectively permanently retained in facial engagement with said paste layer.

7. The battery plate construction of Claim 6 wherein said sheet is made of glass fibers.

8. The battery plate construction of Claim 6 wherein said sheet comprises a fibrous sheet.

9. The battery plate construction of Claim 6 wherein said element comprises fibers having distal ends thereof embedded in said paste layer.

10. The battery plate construction of Claim 6 wherein said separator sheet material has a thickness in the range of approximately .008" to .040".

11. The battery plate construction of Claim 6 wherein said separator sheet material has a porosity in the range of approximately 75% to 90%.

12. The battery plate construction of Claim 6 wherein said separator sheet material has a mean pore size range of .5 to 20 microns.

13. A battery plate construction made in accordance with the method of Claim 1.

14. Our invention as substantially shown and described.