GB1601118A

GB1601118A - Sea-water activatable electric storage batteries

Info

Publication number: GB1601118A
Application number: GB882280A
Authority: GB
Original assignee: Chloride Group Ltd
Current assignee: Chloride Group Ltd
Priority date: 1978-05-12
Filing date: 1978-05-12
Publication date: 1981-10-28

Description

(72) Inventors: SUZANNE WARRELL, NORMAN ERNEST BAGSHAW (54) SEA WATER ACTIVATABLE ELECTRIC STORAGE BATTERIES (71) We, CHLORIDE GROUP LIM1TED, a company registered under the laws of England, of 52 Grosvenor Gardens, London SWI W OAU, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to sea water activatable batteries and is a divisional application from our co-pending British Patent Application No. 32563/77, cognate with No.

8342/78 (Serial No. 1 601117) which describes an improved positive active material composition.

This present invention relates to an improved anode composition for sea water activatable batteries.

An object of the present invention is to provide an anode composition having a reduced tendency to form sludge.

The invention is concerned particularly 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.

The present invention comprises the use of an alloy of magnesium and 0.05 to 3.5% by weight, preferably 0.2 to 2.0% by weight manganese as the anode for a sea water activatable electric storage battery.

The present invention also extends to an electric storage battery adapted to be activated by introduction of sea water to the cells which is made up of cathodes comprising lead chloride, silver chloride or cuprous chloride and anodes consisting 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.

The battery has a housing and intercell partitions provided with means for permitting access of sea water to the interiors of the cells when the battery is immersed in sea water.

In one preferred form of the invention the battery is made up of intercell partitions having their ends embedded in a polymer compound and their sides enclosed in a heat shrunk sleeve of polymer, the electrodes being enclosed within the compartment formed by the partitions, the sleeve and the end wall of polymer compound.

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 of film forming polymeric material resistant to the electrolyte involved. For sea water electrolyte, cellulose acetate is suitable.

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

The battery may also have structural end walls within which the intercell partitions and electrodes are sandwiched, the structural end walls being located within the heat shrunk sleeve.

The end walls of polymer compound may be a potting compound but are preferably a hot melt adhesive especially soft waxy types which are resistant to shock and have good low temperature crack resistance.

The heat shrunk sleeve can be made from any heat shrinkable sheet or film material which is resistant to the electrolyte. For sea water electrolytes, polyvinyl chloride is suitable.

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.

The sleeve, top and bottom end walls or structural end walls, if present, may have apertures in one or more of them so as to permit access of electrolyte to the cells and escape of gas. In a multi-cell battery the intercell partitions should also have apertures in their free ends clear of the electrodes to permit electrolyte access to all parts of each cell.

In a preferred 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.

In a preferred arrangement the ports are located in the top ends of the partitions within recesses or chamfers formed in the electrodes and the ports at least at these top ends are arranged in staggered relationship from cell to cell.

The electrodes may consist ofthe magnesium anode and a lead chloride or silver chloride cathode spaced by suitable separators e.g. P.V.C - rods.

The lead chloride cathode active material composition used with the magnesium anode preferably consists 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 0.10/o 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 fibre 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 invention may be put into practice in various ways and two specific embodiments and certain comparative examples 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 a perspective view in partial cross section and shows about half the battery, Figures 2,3,4, and 5 are views of modified forms of intercell partition.

The battery has two side walls 10 and 11 of polystyrene sheeting spaced apart at each end by a block of hot melt adhesive 12 and 13 (not shown). The outside faces and open sides of the side walls 10 and 11 between the blocks 12 and 13 are closed by a heat shrunk sleeve 14, e.g. of polyvinyl chloride. The sleeve has a twofold advantage. It forms the outer case of the battery but contributes very little extra weight or volume to the construction, while at the same time it acts as a neat finish to the battery.

It also facilitates the construction of batteries varying in size and shape. The container thus formed contains three cells divided from each other by two sheets of cellulose acetate 15 and 16 which have their top and bottom ends embedded in the blocks 12 and 13 respectively.

These two sheets also co-operate with a further sheet of cellulose acetate 17 which is located at the inside face of the wall 11. The width of the sheets 15, 16 and 17 is such that they can be folded over at the sides of the cell so that the sheet 17 overlaps the sheet 15 which overlaps the sheet 16 which in turn overlaps the edge of the wall 10. This is best seen at the bottom end of the drawing, where the sleeve 14 is cut away.

The top and bottom ends of the overlapped side edges of the sheets 17, 15 and 16 are also em- bedded in the edges of the blocks 12 and 13.

The arrangement is the same at each side of the battery and thus the cells are separated from each other.

The only electrolyte connection between the cells is a small hole in each free end of the sheets 15 and 16.

These holes 18 and 19 (not shown) are positioned so that the electrolyte has to follow a long pathway through the cell, passing in zigzag fashion from cell to cell, the zig-zag at the top of the battery being in the opposite sense to that at the bottom.

The electrolyte, which may be sea water, enters through one of a pair of holes 20 and 21 (not shown) which pass through the side wall 11 at opposite corners. The hole 18 is then at the opposite side to the hole 20 and the hole 19 at the same side as the hole 20.

Depending on the orientation in which the battery enters the water either the hole 20 or 21 will be the inlet for the sea water while air will escape from the other hole.

The cell next to the wall 11, but spaced therefrom by the sheet 17, consists of a sheet of magnesium 0.025 inches thick as the anode 25, separated by four vertical polyvinyl chloride ribs 26 each 1.0 mms thick, from a lead chloride cathode 27,0.60 inches thick, which is separated from the next anode 28 by the cellulose acetate sheet 15 which is 0.002 inches thick.

Each cathode consists of an expanded copper mesh current collector 30 to which is adhered the active material composition which can be any suitable lead chloride composition. An example is given below.

A series connection between the cathode 27 and the anode 28 is made by removing a patch of active material from the centre of the cathode 27 and stapling the mesh 30 through the sheet 15 to the anode 28. This is also done for the cathode 40 in the next cell and the anode 41 in the last cell. The anode terminal 42 is welded to one corner of the anode 25 and embedded in the block 12 and the cathode terminal 43 is welded to the mesh 30 bared at one corner of the cathode 45 and is also embedded in the block 12 at the opposite corner. This helps secure the leads to the battery.

The battery is assembled by stapling each cathode through the cellulose acetate sheet to each anode, perforating the free ends of the sheets making the terminal connections, laying the sub assemblies on top of each other spaced apart by the P.V.C. rods, placing the end cellulose acetate sheet in place and then placing the polystyrene end walls in place. The edges of the cellulose acetate sheets are then wrapped round the sides of the battery and the bottom end dipped in a potting compound e.g. a hot melt adhesive effective to adhere to polystyrene and to cellulose acetate. The battery is then inverted, the terminal wires are held out of the way up the sides of the cell and the top end dipped in hot melt adhesive so as to encapsulate the other ends of the cellulose acetate sheets.

The wires are then quickly brought round and forced into the hot adhesive before it sets.

Alternatively pin terminals could be used instead of wires. When the assembly has set, a sleeve of heat shrinkable polymer e.g. P.V.C. is slipped over the battery and heat applied to heat shrink the sleeve around the sides and over the ends of the battery.

Figures 2,3, 4 and 5 are views of modified forms of intercell partition which have been devised to minimize the problems of intercell leakage currents whilst also minimizing battery volume; the electrolyte ports, 18 and 19 are located in the partitions 15 and 16 at least partially within the plan area of the electrodes 27 (etc.). This enables the height of the battery to be reduced or alternatively enables one to have electrodes of greater area within a stipulated height while at the same time the intercell port is as far removed as possible from the electrodes so as to minimize leakage currents.

The ports 18 and 19 may be at opposite corners as in Figures 2 and 4 or at the same corners as in Figures 3 and 5. Ports in adjacent intercell partitions may be in line or may be staggered as in the Figure 1 arrangement.

EXAMPLES 1 TO 4 Four separate batteries were assembled as described above with reference to Figure 1.

The cathodes were all the same and consisted of 96% by weight lead chloride (99.9% pure), 1.5% polyester fibre and 2.5% neoprene rubber.

The lead chloride powder and polyester fibre were dry tumble mixed. The neoprene rubber was then added as an aqueous latex together with a small amount of wetting agent such as 'Teepol'. The dry crumbly composition was spread in a mould and the mesh 30 was pressed into it. The assembly was then dried at 40 OC.

The anodes were all different.

The anode of Example 1 consisted of 0.59% zinc, 6.1% aluminium, 0.22% manganese, balance magnesium and impurities of less than 0.06%. The anode of Example 2 consisted of 1.0% zinc, 3.0% aluminium, 0.2% manganese balance of magnesium and impurities of less than 0.1%. The anode of Example 3 consisted of 1.52% manganese remainder magnesium and impurities of less than 0.55%.

The anode of Example 4 consisted of 6.0% aluminium, 5.0% lead, 1.5% zinc, 0.3% manga nese remainder magnesium and impurities of less than 1.0%.

Example 3 is in accordance with the invention, the other examples are for comparison.

Four cells made up as described were operated under identical conditions at 25 OC. Table 1 gives the results.

When equivalent ten cell batteries were made up the voltage operating level using cells of Example 1 was 10.5 volts, that when using cells of Example 3 was 11.1 volts. The efficiency of the two batteries was about 55% based on the cathodic coulombic yield.

Thus cells using anodes in accordance with this aspect of the present invention give higher voltages and suffer from less sludge formation.

WHAT WE CLAIM IS: 1. A sea water activatable electric storage battery having anodes made of an alloy consisting of magnesium and 0.05 to 3.5% by weight manganese.

2. An electric storage battery adapted to be activated by introduction of sea water to the cells which has cathodes comprising lead chloride, silver chloride or cuprous chloride and anodes consisting of 0.05 to 3.5% by weight manganese and at least 96.3% by weight magnesium and not more than 1.0% by weight impurities.

3. An electric storage battery as claimed in claim 1 or claim 2, in which the anodes contain 1.3 to 1.7% manganese.

4. An electric storage battery as claimed in claim 1, 2 or 3 made up of intercell partitions having their ends embedded in a polymer compound and their sides enclosed in a heat shrunk sleeve of polymer, the electrodes being enclosed within the compartment formed by the partitions, the sleeve and the end walls of polymer compound.

5. An electric storage battery as claimed in claim 4 in which the partitions are of thin sheet form 0.001 to 0.01 inches thick.

6. An electric storage battery as claimed in claim 4 or claim 5 in which the partitions extend beyond the edges of the electrodes sufficiently for them to be folded over so as to overlap the adjacent partition.

7. An electric storage battery as claimed in any one of claims 4 to 6 which also has structural end walls within which the intercell partitions and electrodes are sandwiched, the structural end walls being located within the heat shrunk sleeve.

8. An electric storage battery as claimed in any one of claims 4 to 7 in which the end walls of polymer compound are of hot melt adhesive resistant to shock and having good low temperature crack resistance.

9. An electric storage battery as claimed in any one of claims 4 to 8 in which the heat shrunk sleeve is made from polyvinyl chloride.

10. An electric storage battery as claimed in any one of claims 4 to 9 in which the sleeve, top and bottom walls or structural end walls, if present, have apertures in one or more of them

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. cellulose acetate sheet in place and then placing the polystyrene end walls in place. The edges of the cellulose acetate sheets are then wrapped round the sides of the battery and the bottom end dipped in a potting compound e.g. a hot melt adhesive effective to adhere to polystyrene and to cellulose acetate. The battery is then inverted, the terminal wires are held out of the way up the sides of the cell and the top end dipped in hot melt adhesive so as to encapsulate the other ends of the cellulose acetate sheets. The wires are then quickly brought round and forced into the hot adhesive before it sets. Alternatively pin terminals could be used instead of wires. When the assembly has set, a sleeve of heat shrinkable polymer e.g. P.V.C. is slipped over the battery and heat applied to heat shrink the sleeve around the sides and over the ends of the battery. Figures 2,3, 4 and 5 are views of modified forms of intercell partition which have been devised to minimize the problems of intercell leakage currents whilst also minimizing battery volume; the electrolyte ports, 18 and 19 are located in the partitions 15 and 16 at least partially within the plan area of the electrodes 27 (etc.). This enables the height of the battery to be reduced or alternatively enables one to have electrodes of greater area within a stipulated height while at the same time the intercell port is as far removed as possible from the electrodes so as to minimize leakage currents. The ports 18 and 19 may be at opposite corners as in Figures 2 and 4 or at the same corners as in Figures 3 and 5. Ports in adjacent intercell partitions may be in line or may be staggered as in the Figure 1 arrangement. EXAMPLES 1 TO 4 Four separate batteries were assembled as described above with reference to Figure 1. The cathodes were all the same and consisted of 96% by weight lead chloride (99.9% pure), 1.5% polyester fibre and 2.5% neoprene rubber. The lead chloride powder and polyester fibre were dry tumble mixed. The neoprene rubber was then added as an aqueous latex together with a small amount of wetting agent such as 'Teepol'. The dry crumbly composition was spread in a mould and the mesh 30 was pressed into it. The assembly was then dried at 40 OC. The anodes were all different. The anode of Example 1 consisted of 0.59% zinc, 6.1% aluminium, 0.22% manganese, balance magnesium and impurities of less than 0.06%. The anode of Example 2 consisted of 1.0% zinc, 3.0% aluminium, 0.2% manganese balance of magnesium and impurities of less than 0.1%. The anode of Example 3 consisted of 1.52% manganese remainder magnesium and impurities of less than 0.55%. The anode of Example 4 consisted of 6.0% aluminium, 5.0% lead, 1.5% zinc, 0.3% manga nese remainder magnesium and impurities of less than 1.0%. Example 3 is in accordance with the invention, the other examples are for comparison. Four cells made up as described were operated under identical conditions at 25 OC. Table 1 gives the results. When equivalent ten cell batteries were made up the voltage operating level using cells of Example 1 was 10.5 volts, that when using cells of Example 3 was 11.1 volts. The efficiency of the two batteries was about 55% based on the cathodic coulombic yield. Thus cells using anodes in accordance with this aspect of the present invention give higher voltages and suffer from less sludge formation. WHAT WE CLAIM IS:

1. A sea water activatable electric storage battery having anodes made of an alloy consisting of magnesium and 0.05 to 3.5% by weight manganese.

TABLE 1 Example Average voltage Cell efficiency Sludge operating level based on cathode formation 1 1.02 96% moderate 2 1.01 84% moderate 3 1.08 94% least 4 1.11 85% more so as to permit access of electrolyte to the cells and escape of gas, and the intercell partitions have apertures in their free ends clear of the electrodes to permit electrolyte access to all parts of each cell.

11. An electric storage battery as claimed in claim 10 in which the electrodes have recesses or chamfers in each of their top and bottom ends and the apertures in the intercell partitions are located opposite and at least partially within these chamfers or recesses spaced from the electrodes.

12. An electric storage battery as claimed in any one of claims 1 to 11 in which the cathode active material composition is a lead chloride composition consisting of 1% to 5% by weight organic polymer fibre, 1% to 5% by weight polymeric binder, 0% to 0.2% by weight of a wetting agent, the balance of at least 90% by weight being lead chloride.

13. An alectric storage battery as claimed in claim 12 in which the lead chloride is present in an amount of 92% to 97% by weight, the fibre in an amount of 1% to 3% by weight and the binder in an amount of 2% to 5% by weight.

14. An electric storage battery as claimed in claim 1 substantially as specifically described herein with reference to Figure 1 and Figures 2, 3,4 or 5 of the accompanying drawings and Example 3.

15. A method of generating electric current which comprises discharging abattery as claimed in any one of claims 1 to 14 through a load in such a way that the current density related to the cathode is not more than 1.0 mA/cm.