GB2030759A

GB2030759A - Electric storage batteries

Info

Publication number: GB2030759A
Application number: GB7924793A
Authority: GB
Original assignee: Chloride Group Ltd
Current assignee: Chloride Group Ltd
Priority date: 1978-07-18
Filing date: 1979-07-17
Publication date: 1980-04-10
Also published as: GB2030759B

Abstract

An electric storage battery made up of a stack of intercell partitions 23 having at least one pair of opposed edges, juxtaposed to preformed sheets, the said opposed edges being a close fit with the said sheets 10, 11, 12, 13, but not sealed thereto, the electrodes being enclosed within compartments formed by the partitions 23, the preformed sheets 10, 11, 12, 13, and means 14 and 15 enclosing the opposed faces of the stack. The partitions are preferably of thin sheet form made of film-forming polymeric material resistant to the electrolyte involved. <IMAGE>

Description

SPECIFICATION Electric storage batteries The present invention relates to electric storage batteries and particularly but not exclusively to sea water activatable batteries and describes an improved form of container construction, and an improved form of separator arrangement.

British patent specification No. 1172517 shows a battery, which is activatable by sea water, having the cells spaced apart by barriers of flexible sheet material, the top, the bottom, and the two side walls of the battery being adhesively fastened to the opposing end walls and to the barriers. This is a difficult construction to assemble and does not lend itself readily to mass production.

An object of the present invention is to produce a simpler container construction than hitherto available, and a separator arrangement which simplifies assembly of the battery.

According to one aspect of the present invention an electric storage battery is made up of a stack of intercell partitions having at least one pair of opposed edges, referred to herein as the top and bottom edges, juxtaposed to preformed sheets, the said opposed edges being a close fit with the said sheets, but not sealed thereto, the electrodes being enclosed within compartments formed by the partitions, the preformed sheets and means enclosing the opposed faces of the stack and the other pair of opposed sides of the stack.

The partitions are preferably of thin sheet form e.g. 0.01 inches or less, e.g. 0.001 to 0.01 inches thick. They may be made of filmforming polymeric material resistant to the electrolyte involved. For sea water electrolyte, cellulose acetate is suitable.

The partitions preferably extend beyond the side edges of the electrodes sufficiently for them to be folded over so as to overlap the adjacent partition.

The battery preferably has also structural end walls e.g. of preformed sheet material within which the intercell partitions and electrodes are sandwiched.

In a preferred form of the invention the stack of intercell partitions and electrodes is enclosed within a close fitting preformed box, the top and bottom edges of the intercell partitions and the opposed side edges being located within a distance, A, of not more than 20 thou. (0.5 mm) and especially within 10 thou. (0.25 mm) from the inside face of the top and bottom walls of the box over substantially the full width of the box, and the length of the path around each of the top and bottom edges of each intercell partition from the end of an electrode on one side of the partition to the end of the electrode on the other side of the partition being at least 5 mms and preferably at least 5.5 mms. The top and bottom ends of the electrodes are preferably each spaced a distance, B, of at least 3 mms from the inside face of the top and bottom walls of the preformed box.

The opposed side edges must be made at least to fulfill the same requirements for a close fit, but are preferably made with the sides of the intercell partitions extending out beyond the dimensions required merely for a close fit so that in order for the stack to be fitted into the box they have to be folded over so that each portion overlaps at least the partition of the adjacent cell and preferably also the partition of the next cell as well. This reduces the need for accurate control of tolerances for these edges of the intercell partition and also assists in assembly of the stack in the box. Thus the box is preferably made with one side, which will be opposite a face of the stack, open, but in use closed by a wall member, and the stack is inserted sideways through this opening with the overlapped edges of the intercell partitions pointing back towards the said open side.Once the box is full the open side is closed by a wall member clipped, glued or welded or otherwise secured into place.

The compartments in the sea-water activatable embodiments of the invention are interconnected by inlet and outlet ducts. These may be formed in the top and bottom walls referred to above and may be formed either in the thickness of the top and bottom walls or preferably as protruberances extending outwardly thereform and disposed transverse to the walls and intermediate the ends of the walls e.g. adjacent or on the median line of the walls.

The ducts preferably have a width not in excess of 5B and preferably not more than 20% of the width of the top wall.

The electrodes in adjacent cells may be connected directly through the intercell partition e.g. by a mechanical metallic connection such as a staple or rivet engaging conducting portions of both electrodes.

Instead of the ducts being formed in the preformed bottom and top sheets they may be formed in the means enclosing the opposed faces of the stack or in the means enclosing the other pair of opposed sides of the stack.

These ducts permit access of electrolyte to the cells and escape of gas. In a multi-cell battery the ducts must have access to all parts of the cell. This can be achieved directly or by each intercell partition having apertures in their free ends clear of the electrodes.

In one form of cell the electrodes have recesses or chamfers in each of their top and bottom ends and the apertures are located opposite and preferably at least partially within or within these chamfers or recesses spaced from the electrodes. The apertures in adjacent partitions may be located in in-line or staggered relationship.

The electrodes in the sea-water activatable embodiment of the invention may consist of a magnesium anode and a lead chloride or silver chloride cathode spaced by suitable separator means e.g. P.V.C. rods or by the preferred separator arrangement described below.

The lead chloride cathode active material composition may consist of 1% to 5% by weight organic polymer fibre e.g. polyester fibre, 1% to 5% by weight polymeric, preferably elastomeric, binder e.g. neoprene rubber, optionally up to 0.2% by weight e.g. 0.01% to 0.1% of a wetting agent, the balance of at least 90% being lead chloride.

The lead chloride is preferably present in an amount of 92% to 97%, the fibres in an amount of 1% to 3% and the binder in an amount of 2% to 5%.

The fibre preferably has an average fibre length of 1.0 mms and a denier of not thicker than 5.

The anodes may consist of a metal anode, e.g. a magnesium anode, and preferably consist of 0.05 to 3.5% by weight manganese preferably 0.2 to 2.0% manganese, e.g.

1.3-1.7% manganese, at least 96.3% by weight magnesium, and preferably not more than 0.2% impurities.

A preferred form of separator means comprises separate deposits of electrically nonconducting resin material adhered to discrete localized regions of the metal anode. The resin may be a hot melt adhesive e.g. a polyamide hot melt adhesive. The deposits are preferably discrete drops having a maximum transverse dimension parallel to the plane of the anode of not more than 10 times their thickness and preferably in the range 2 to 5 times their thickness. The deposits are preferably substantially circular in plan and have a contact angle, C, of not less than 90 , C being the angle between a tangent to the surface of the deposit at its point of contact with the plane on which it rests, and the plane.

The deposits are preferably made by depositing the hot resin composition on the anode when it is itself heated so as to prevent chilling of the deposit and to ensure the desired profile and good adhesion.

The invention may be put into practice in various ways and two specific embodiments will be described to illustrate the invention with reference to the accompanying diagrammatic drawings of a battery in accordance with the invention, in which: Figure 1 is an exploded perspective view just prior to assembly showing a first embodiment in accordance with the invention; Figure 2 is a cross-section after assembly prior to fitting the side wall on the line ll of Fig. 1; Figure 3 is a cross-section after assembly without the side wall on the line Ill of Fig. 1; Figure 4 is an exploded perspective view just prior to assembly showing a second embodiment in accordance with the invention; Figure 5 is a cross-section after assembly prior to fitting the side wall on the line V of Fig. 4;; Figure 6 is a cross section after assembly without the side wall on the line Vl of Fig. 4; Figure 7 is a perspective view in partial cross-section and shows about half the battery, the thickness of the electrodes being exaggerated for easier representation; and Figure 8 is a side view of part of the anode showing the pimple spacer.

The battery shown in Figs. 1, 2 and 3 has an injection moulded thermoplastic box as its container having top and bottom walls 10 and 11, side walls 12 and 13 and a back wall 14 all moulded in one piece and a separate front wall 15 adapted to be welded or glued to the open edges of the walls 10, 11, 12 and 13.

The top and bottom walls are typically 4.4 cms by 8 cms, the side walls 8.5 cms by 4.4 cms and the front and back walls 8.5 cms by 8 cms. The wall thickness is 1-1.5 mm. The front wall 15 has inlet and outlet ducts 17 and 18 providing for ingress of sea water at the bottom of the battery and egress of sea water and gas at the top of the battery.

The active component of the battery comprises a stack of positive and negative electrodes, 20, 21 connected to each other by a staple 22 (see Fig. 7) through the centre of an intercell partition 23, disposed between the two electrodes. A positive electrode is against the back wall 14 and a positive terminal 26 is lead out through a hole 25 in the wall 10 and a negative terminal 27 is lead out through a hole 28 in the same wall, (see Fig. 7). These holes are sealed with resin e.g. epoxy resin after the cell is assembled. The positive anc' negative electrodes in a cell are separated from each other by P.V.C. rods or preferably by pimples 30 of generally hemispherical shape formed of hot melt adhesive adhered to the metallic anode (see Figs. 7 and 8).

The intercell partitions 23 are made of sheets of cellulose acetate the top ends 32 and the bottom ends of which are a flush fit to the inside faces of the top and bottom walls 10 and 11 of the box. Each of the top and bottom ends of the partitions are carefully cut to size and superposed in register so that when the stack is placed in the box the maximum spacing is no more than 10 thou.

(0.25 mm). This distance B from the ends of each of the positive and negative electrodes from the inside faces of the walls 10 and 1 is also carefully controlled so as not to be less than 3 mms so that the leakage pathway from the end of a positive electrode 20 around the end of its partition 23 to the negative electrode is always at least 5.5 mms.

The sides of the partitions 23 extend out s- that in order for the stack to be fitted into the box they have to be bent over as shown in Fig. 2 and Fig. 7 and Fig. 6 and Fig. 7. The bent over portions 33 preferably overlap bent over portions of at least the cell above and preferably two cells above.

The electrodes have opposite corners cut away in the embodiment shown in Figs. 1 to 3. A small hole 34 is formed in the triangular portion 35 of each corner of each partition 23 which is thus left open. These holes 34 register with the inlet and outlet ducts 17 and 18 in the front face 15 of the box. This is the sole means of electrolyte access to the cells and from one cell to another.

Depending on the orientation in which the battery enters the water either the hole 17 or 18 will be the inlet for the sea water while air will escape from the other hole.

The arrangement shown in Figs. 4 to 8 is closely similar except that in order to save space electrolyte access to the cells is achieved in a different way. Instead of each electrode having a triangular portion removed from opposed corners and holes 34 being formed therein, electrolyte access is from the walls 10 and 11. The holes 17 and 18 in the front wall 15 are dispensed with.

The top and bottom walls have transverse channels 17 and 18 protruding outwardly but with an inwardly opening face providing slots 19, 40, 6 mms e.g. 3-9 mms wide opening into the battery and extending across the ends of the intercell partitions. The ends of the channels 19 and 40 are closed at the rear face and open at the front face of the battery.

The channels are 3 e.g. 1-6 mms deep.

The cell next to the wall 14, which optionally (see Fig. 7) may be spaced therefrom by a sheet of cellulose acetate, consists of a cathode 20, 7.6 cms square and then a sheet 7.6 cms square, of magnesium 0.025 inches thick as the anode 21, separated by four rows of five pimples of hot melt adhesive 30, each 1.5 mms thick, and 6 mms across, from the lead chloride cathode 20, which is 1.4 mm thick. This cathode is separated from the next anode 21 by the cellulose acetate sheet 23 which is 0.004 inches thick.

Each cathode consists of an expanded copper mesh current collector 37 to which is adhered the active material composition which can be any suitable lead chloride composition.

A series connection between each cathode 20, except the first one, and each anode 21 is made by removing a patch of active material from the centre of the cathode 20 and stapling the mesh 37 through the sheet 23 to the anode 21. Stapling without removing the patch of active material is also effective. This is done for each pair of cathodes and anodes.

The anode terminal 27 is welded to one corner of the anode 21 nearest the wall 15 and passes out of the box through the hole 28 and the cathode terminal 26 is welded to the mesh 37 bared at one corner of the cathode 20 nearest the back wall 14 at the same or opposite corner, and passes out of the box through the hole 25.

Example 1 below illustrates a suitable lead chloride cathode active material.

Example I The active material consists of 96% by weight lead chloride (99.9% pure), 1.5% polyester fibre and 2.5% neoprene rubber.

The lead chloride powder, polyester fibre and neoprene rubber, added as an aqueous latex, are then mixed together. The dry crumbly composition is spread in a mould and has the mesh 37 pressed into it. The assembly is then dried at 40 C.

Example 2 The anodes are preferably made of a magnesium alloy containing 1.52% manganese, remainder magnesium and impurities of less than 0.055%.

The battery is assembled as follows: The spacers 30 are formed on each anode 21 by heating the anode of 80-90 C and then depositing molten drops of hot melt adhesive e.g. at 360to, 150-160 C on the anode whereby circular pimples about 1 mm thick are formed which adhere well to the anode having a large surface of contact but which interfere very little with electrolyte flow through the cell as compared with conventional P.V.C. rods. Preheating the anode is thought to assist in achieving a good shape for the spacer 30 and good contact. The cellulose acetate intercell partitions are cut to size, each cathode stapled through a partition 23 to an anode having its spacers 30 facing outwardly, care being taken to ensure that the components are correctly positioned as discussed above.

The cathode terminal is welded onto the first cathode which is placed in the cell against the inside face of the back wall 14.

The stack of electrode pairs are then placed in the box with the side portions 33 of the partitions 23 folded up against the inside face of the side walls 12 and 13 of the box. The remaining electrode pairs are then pushed down into the box so that each pair is overlapped at its edges by the folded over portion 33 of the partition of the previous pair. If desired they can be preassembled into a pack with the overlapped portions welded together e.g. by application of a solvent such as acetone.

The anode terminal is then formed. Finally the front face 15 is secured in place e.g. by welding or adhesive and the terminal holes 25 and 28 sealed.

The invention is particularly but not exclusively applicable to electric storage batteries activatable by sea-water and with small cells which are used at current drains of up to 30 mA/sq.cm or even 100 mA/sq. cm. for such uses as life jackets where they are stored in a dry condition and are activated by immersion in sea-water.

Claims

1. An electric storage battery which is made up of a stack of intercell partitions having at least one pair of opposed edges, referred to herein as the top and bottom edges, juxtaposed to preformed sheets, the said opposed edges being a close fit with the said sheets, but not sealed thereto, the electrodes being enclosed within compartments formed by the partitions, the preformed sheets and means enclosing the opposed faces of the stack and the other pair of opposed sides of the stack.

2. An electric storage battery as claimed in Claim 1 in which the partitions are of thin sheet form and are made of film-forming polymeric material resistant to the electrolyte involved.

3. An electric storage battery as claimed in Claim 1 or Claim 2 in which the partitions extend beyond the side edges of the electrodes sufficiently for them to be folded over so as to overlap the adjacent partition.

4. An electric storage battery as claimed in Claim 1, 2 or 3 which has structural end walls of preformed sheet material within which the intercell partitions and electrodes are sandwiched.

5. An electric storage battery as claimed in Claim 1, 2, 3 or 4 in which the stack of intercell partitions and electrodes is enclosed within a close fitting preformed box, the top and bottom edges of the intercell partitions and the opposed side edges being located within a distance, A, or not more than 20 thou. (0.5 mm) from the inside face of the top and bottom walls of the box over substantially the full width of the box, the length of the path around each of the top and bottom edges of each intercell partition from the end of an electrode on one side of the partition to the end of the electrode on the other side of the partition being at least 5 mms, the top and bottom ends of the electrodes each being spaced a distance, B, of at least 3 mms from the inside face of the top and bottom walls of the preformed box.

6. An electric storage battery as claimed in Claim 5 in which the opposed side edges of the intercell partitions extend out beyond the dimensions required merely for a close fit so that in order for the stack to be fitted into the box they have to be folded over so that each portion overlaps at least the partition of the adjacent cell.

7. An electric storage battery as claimed in Claim 5 or Claim 6 in which the box is made with one side, which will be oposite a face of the stack, open, but in use closed by a wall member and the stack is inserted sideways through this opening with the overlapped edges of the intercell partitions pointing back towards the said open side, the open sides being closed by a wall member clipped, glued or welded or otherwise secured into place.

8. An electric storage battery as claimed in any one of Claims 1 to 7 in which inlet and outlet ducts are formed in the top and bottom walls as protruberances extending outwardly therefrom and disposed transverse to the walls and intermediate the ends of the walls.

9. An electric storage battery as claimed in Claim 8 in which the ducts have a width not in excess of 5B and not more than 20% of the width of the top wall.

10. An electric storage battery as claimed in any one of Claims 1 to 9 in the form of a sea-water activatable battery having electrodes consisting of a magnesium anode and a lead chloride or silver chloride cathode spaced by separator means.

11. An electric storage battery as claimed in Claim 10 in which the separator means comprise separate deposits of electrically nonconducting resin material adhered to discrete localized regions of the metal anode.

12. An electric storage battery as claimed in Claim 11 in which the deposits are discrete drops having a maximum transverse dimension parallel to the plane of the anode of not more than 10 times their thickness.

13. An electric storage battery as claimed in Claim 12 in which the deposits are substantially circular in plan and have a contact angle, C, of not less than 90 , C being the angle between a tangent to the surface of the deposit at its point of contact with the plane on which it rests, and the plane.

14. An electric storage battery as claimed in Claim 12 or Claim 13 in which the deposits are made by depositing the hot resin composition on the anode when it is itself heated so as to prevent chilling of the deposit and to ensure the desired profile and good adhesion.

15. An electric storage battery as claimed in any one of Claims 11 to 14 in which the resin is a polyamide hot melt adhesive.

16. An electric storage battery as claimed in Claim 1 substantially as specifically described herein with reference to Figs. 1 to 3 or Figs. 4 to 8.