Patent GB-1456736-A (GB)
Title: Hydraulically refuelable metal-gas depolarized battery system
IPC: H01M10/44
Filed: 1974-04-09
Abstract: 1456736 Refuelable metal-gas batteries ELECTROMEDIA Inc 9 April 1974 [13 April 1973] 15587/74 Heading H1B [Also in Division C7] A refuelable battery comprises metal-gas cells 38, a port 22 for supplying a slurry of electrolyte and metal powder to each cell and a port 16 for removing electrolyte and solid discharge products from each cell. Each cell includes a pair of gas electrodes 39 situated on either side of an anode current collector grid 42 and spaced therefrom by separators 41. The space occupied by the grid is supplied with the active metal powder/electrolyte slurry. The electrolyte is KOH or NaOH and the metal powder is preferably zinc but Li, Mg, Al, Cd and Fe may be used. The oxidant gas is supplied to the spaces 73 around the cells and is preferably air but oxygen-enriched air, oxygen, hydrogen peroxide, chlorine or bromine may be used. In addition to the input port 22 for the slurry mixture and the output port 16 for the spent mixture, each cell has an output port 18 for extracting electrolyte beneath a perforated plate 19. For discharging spent fuel and electrolyte and for recharging with new fuel obtained from electrolytically processing the spent fuel, the battery is connected by disconnectible couplings 31 to a holding tank 43 for the spent fuel and a slurry tank 48, Fig. 4, for the processed fuel. The ports 22 are connected through a manifold 26 and valve 75 to the tank 48 and the ports 16 are connected through valves 32 and a manifold 24 to the tank 43. Ports 18 are connected through valves 33 and a manifold 23 to the tank 48 and ports 22 are additionally connected through the manifold 26 and a valve 77 to the tank 43. An electrolytic processing tank 58 is interposed between the tanks 43, 48 and serves to reduce the zinc oxide from the battery to zinc. An electric switch (Fig. 6, not shown) is operated to disconnect the individual cells before recharging the battery; also, to prevent circulating currents between the cells the manifolds and sections of the interconnecting pipes are made of insulating material, e.g. rubber. New slurry from tank 58 is transferred to the ports 22 by a pump 52 and to enable sufficient zinc powder to be supplied to the cells, valves 33 are opened and vacuum pump 53 is operated to return electrolyte to tank 48. The tank 48 contains an agitator 49 to bring the zinc powder into suspension. The spent slurry is returned to tank 43 by opening valves 32 and this emptying action is augmented to washout residual particulate matter by opening valve 77 and operating pump 44 to circulate the electrolyte, a filter 46 preventing circulation of solid matter. The tank 58 includes a cylindrical cathode 54 rotated by a motor 55 and surrounding anodes 56. A wiper blade 57 removes active zinc deposit from the cathode and an agitator 59 maintains the zinc powder in suspension. A pump 72 supplies the spent slurry to the tank 58. The anode current collector 42, is of corrugated shape and may be of copper or silver-plated copper. The air electrodes 39 may comprise a mesh having a platinum or palladium catalyst; alternatively, the electrodes may comprise gas-permeable carbon-PTFE. Fig. 7 shows another embodiment of the battery cells in which each cell comprises two porous negative current collectors 79 defining a conduit 81, two compartments 84 for receiving the active metal powder and electrolyte slurry mixture, separator 82 and gas cathodes 83. When the battery is emptied by opening valves 87 the collectors 79 are back washed by pumping filtered electrolyte from tank 43 through valve 86 into conduit 81. The tank 58 may be replaced by another construction of electrolytic processing apparatus described with reference to Fig. 5 (not shown).