Zinc electrode and rechargeable zinc-air battery

An improved zinc electrode for a rechargeable zinc-air battery comprising:

• (a) an outer frame consisting essentially of a plastic material exhibiting chemical inertness to the alkaline electrolyte as well as the electrochemical reactions taking place in a rechargeable zinc-air battery;
• (b) a central opening within said frame;
• (c) a porous foam electrode support within said central opening in said frame selected from the class consisting of carbon foam and a metal foam and having a mean pore size of from about 5 to about 300 microns and a surface area of at least about 25 cm.sup.2 /cm.sup.3 ;
• (d) a 1-5 micron layer of an electrically insulating and electrochemically inert material on the external surface of said porous foam electrode support to render the treated surface inactive for zinc deposition to inhibit the formation of zinc dendrites on the surface thereof;
• (e) a layer of zinc electrolytically deposited on said treated porous foam electrode support;
• and
• (f) means within said outer frame for circulating an alkaline electrolyte through the interior of said zinc-coated foam comprising a first horizontal bore beneath said central opening and a second horizontal bore above said central opening and a plurality of vertical bores respectively communicating between said lower horizontal bore and said central opening, and said upper horizontal bore and said central opening;
• whereby electrolyte may be circulated through said electrode through an inlet to one of said horizontal bores and removed from said electrode through an outlet connected to the other of said horizontal bores.

A method of forming an improved zinc electrode for a rechargeable zinc-air battery which comprises:

• (a) forming an outer electrode frame from a plastic material exhibiting chemical inertness to the alkaline electrolyte as well as the electrochemical reactions taking place in a rechargeable zinc-air battery;
• (b) forming a central opening within said frame;
• (c) mounting a porous foam electrode support within said central opening in said frame selected from the class consisting of carbon foam and a metal foam, said foam having a mean pore size of from about 5 to about 300 microns and a surface area of at least about 25 cm.sup.2 /cm.sup.3 ;
• (d) treating the external surface of said porous foam electrode support with a 1-5 micron layer of an electrically insulating and electrochemically inert material to render the treated surface inactive for zinc deposition to inhibit the formation of zinc dendrites on the surface thereof;
• (e) electrolytically depositing a layer of zinc on said treated porous foam electrode support;
• and
• (f) forming means within said outer frame for circulating an alkaline electrolyte through said zinc-coated foam comprising a first horizontal bore beneath said central opening and a second horizontal bore above said central opening and a plurality of vertical bores respectively communicating between said lower horizontal bore and said central opening, and said upper horizontal bore and said central opening;
• whereby electrolyte may be circulated through said electrode through an inlet to one of said horizontal bores and removed from said electrode through an outlet connected to the other of said horizontal bores.

An improved rechargeable zinc-air battery comprising:

• (a) a battery case;
• (b) zinc electrode means within said case comprising outer frame means, a porous foam electrode support within said frame means having zinc deposited thereon and treated to inhibit the formation of zinc dendrites on the surface thereof, and internal electrolyte circulation means within said outer frame means for circulating an alkaline electrolyte through said zinc-coated foam;
• (c) at least one air electrode means within said case;
• (d) porous separator means located between said zinc electrode means and said air electrode means;
• (e) an alkaline electrolyte within said battery circulating through said zinc electrode means via said internal electrolyte circulations means;
• and
• (f) external electrolyte circulation means for circulating said alkaline electrolyte to said internal circulation means.

An improved rechargeable zinc-air battery system comprising:

• (a) a battery case having one or more air inlet ports and electrolyte inlet and outlet ports formed therein;
• (b) air scrubber means connected to said one or more air inlet ports external to said battery case to remove carbon dioxide from said incoming air;
• (c) zinc electrode means within said case comprising:
• (1) zinc electrode outer frame means;
• (2) a porous foam electrode support within said frame means having zinc deposited thereon and treated to inhibit the formation of zinc dendrites on the external surface thereof;
• and
• (3) internal electrolyte circulation means comprising passageways within said outer frame means for circulating an alkaline electrolyte through said zinc-coated foam;
• (d) at least one air electrode means within said case having a surface facing said zinc electrode means;
• (e) one or more air passages within said battery case between said one or more air inlets and said air electrode means;
• (f) porous separator means located between said zinc electrode means and said air electrode means;
• (g) at least one air electrode backing plate abutting the surface of said air electrode means opposite to the surface facing said zinc electrode means;
• (h) air passage means on a surface of said air electrode backing plate abutting said air electrode means and extending to the side surface of said backing plate to facilitate the passage of air to said air electrode means;
• (i) an alkaline electrolyte within said battery circulating through said zinc electrode means via said internal electrolyte circulations means;
• and
• (j) external electrolyte circulation means for circulating said alkaline electrolyte to said internal circulation means comprising:
• (1) an electrolyte reservoir external to said battery case;
• (2) means for connecting said external electrolyte circulation means to said internal electrolyte circulation means in said zinc electrode outer frame means through said electrolyte inlet and outlet ports in said battery case;
• (3) filter means to filter solids out of said electrolyte as it circulates from said zinc electrode within said battery case to said external reservoir;
• (4) pump means for recirculating electrolyte from said external reservoir to said zinc electrode within said battery case via said connecting means;
• (5) means for optionally adding water to said electrolyte;
• and
• (6) means for optionally replacing at least a portion of said electrolyte with fresh electrolyte.