Process for the preparation of an alkaline-zinc slurry for use in batteries

• US 5,378,329 A
• Filed: 07/06/1993
• Issued: 01/03/1995
• Est. Priority Date: 12/31/1990
• Status: Expired due to Fees

• Current Assignee: Electric Fuel Ltd.
• Original Assignee: Electric Fuel Ltd.
• Inventors: Givon, Menachem, Goldstein, Jonathan R., Gektin, Inna
• Primary Examiner(s): GORGOS, KATHRYN L
• Application Number:
  US08/088,543
• Time in Patent Office: 546 Days
• Field of Search: 204/115, 204/114, 204/116, 204/130, 429/17, 429/19, 429/21, 429/49
• US Class Current: 205/602
• CPC Class Codes: C25C 1/16 of zinc, cadmium or mercury
• CPC Class Codes: C25C 7/08 Separating of deposited metals from the cathode
• CPC Class Codes: H01M 8/06 Combination of fuel cells with means for production of reactants or for treatment of residues regenerative fuel cells H01M8/18
• CPC Class Codes: H01M 8/184 Regeneration by electrochemical means
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A process for the preparation of an alkaline-zinc slurry for use in batteries, the slurry comprising an admixture of (a) at least partly oxidized zinc; (b) an aqueous solution of at least one Group Ia metal; and (c) an inorganic or organic inhibitor. The process includes the steps of electrolyzing the admixture in a cell with a corrosion-resistant anode and a non-zinc-adherent cathode such that the zinc deposits on the cathode self-detach or are removed until no more than a preselected amount of zinc remains in the solution, provided that the current density at the cathode is preselected so that the electrowon zinc will have, after homogenizing into particles, a density within the range 0.2-2.0 g/cc and a surface area within the range 0.5-6.0 m² /g; removing zinc from the cathode and homogenizing it into particles; and combining the homogenized zinc particles with additional aqueous Group Ia metal hydroxide and optionally with other makeup components selected from the group consisting of water and inhibitor to form a charged slurry.

Claims

1. A process for the preparation of an alkaline-zinc slurry for use in batteries, said slurry comprising an admixture of:

(a) zinc which has been at least partly oxidized to an oxidation product selected from the group consisting of zinc oxide, zinc hydroxide and zincates;

(b) an aqueous solution of at least one Group Ia metal comprising anions selected from the group consisting of hydroxide and zincate; and

(c) an inorganic or organic inhibitor, effective to inhibit the interaction of zinc and at least one Group Ia metal hydroxide in aqueous solution, which would otherwise result in the evolution of hydrogen gas;

said process comprising the steps of;

electrolyzing said admixture in a cell with a corrosion-resistant anode and a non-zinc-adherent cathode such that the zinc which deposits on said cathode self-detaches or is removable by a method selected from the group consisting of brushing, scraping, vibrating and the use of liquid jets, until no more than a preselected amount of zinc remains in the solution, provided that the current density at the cathode is preselected so that in conjunction with the non-zinc-adherent characteristic of the cathode, the electrowon zinc will have, after homogenizing into particles, a density within the range 0.2-2.0 g/cc and a surface area within the range 0.5-6.0 m² /g;

removing zinc from the cathode and homogenizing it into particles;

combining said homogenized zinc particles with additional aqueous Group Ia metal hydroxide and optionally with other makeup components selected from the group consisting of water and inhibitor to form a charged slurry;

optionally analyzing said charged slurry in order to ascertain whether at least the values of zinc, the Group Ia metal hydroxide and the inhibitor lie within preset limits; and

optionally adjusting the values of at least one of said aforementioned zinc, Group Ia metal hydroxide or inhibitor to within preset limits for said charged slurry.

2. The process according to claim 1, wherein said inhibitor constitutes about 0.001-4.0 percent by weight, based on the weight of the zinc.

3. The process according to claim 1, wherein said zinc particles are homogenized to a density within the range of about 0.25-1.7 g/cc.

4. The process according to claim 1, wherein said electrolysis step is carried out at a temperature within the range of about 20°

-75°

C.

5. The process according to claim 1, wherein said zinc is homogenized into particles by a method selected from the group consisting of brushing, stirring, and blending.

6. The process according to claim 1, wherein the preselected current density at the cathode lies within the range of 10-600 milliamp/cm².

7. The process according to claim 1, wherein said cathode is made of a metal selected from the group consisting of titanium, vitreous carbon, magnesium and stainless steel.

8. The process according to claim 1, wherein said anode is made of a metal selected from the group consisting of nickel, porous nickel, fibrous nickel and nickel mesh having a surface coating of a mixed oxide of cobalt and nickel.

9. The process according to claim 1, wherein said inhibitor is at least one cation species selected from the group consisting of antimony, bismuth, cadmium, gallium, indium, lead and tin.

10. A process according to claim 9, wherein said inhibitor constitutes about 0.001-4.0 percent by weight, based on the weight of the zinc.

11. The process according to claim 9, wherein said zinc particles are homogenized to a density within the range of about 0.25-1.7 g/cc.

12. The process according to claim 9, wherein said electrolysis step is carried out at a temperature within the range of about 20°

-75°

C.

13. The process according to claim 9, wherein said zinc is homogenized into particles by a method selected from th group consisting of brushing, stirring, and blending.

14. The process according to claim 1, wherein said inhibitor is tetramethylammonium hydroxide.

15. The process according to claim 1, wherein, in said charged slurry, the weight ratio of zinc to aqueous Group Ia metal hydroxide solution is 1:

0.05-12 and said inhibitor is present in a weight ratio of zinc to inhibitor of 1;

0.00001-0.04.

16. A process for the regeneration of an at least partially-spent alkaline-zinc slurry having a dissolved phase and an undissolved please for use in metal-air batteries, which slurry comprises an admixture of:

(a) zinc which has been at least partly oxidized to an oxidation product selected from the group consisting of zinc oxide, zinc hydroxide and zincates;

(b) an aqueous solution of at least one Group Ia metal comprising anions selected from the group consisting of hydroxide and zincate; and

(c) an inorganic or organic inhibitor, effective to inhibit the interaction of zinc and at least one Group Ia metal hydroxide in aqueous solution, which would otherwise result in the evolution of hydrogen gas;

said process comprising subjecting said at least partially-spent slurry, after optional dilution with aqueous Group Ia metal hydroxide and water and the optional addition of an inorganic or organic inhibitor, to the steps of;

optionally separating said dissolved and undissolved phases;

providing an electrolyte selected from the group consisting of said at least partially-spent slurry and said optionally-separated dissolved phase;

electrolyzing said electrolyte in a cell with a corrosion-resistant anode and a non-zinc-adherent cathode such that the zinc which deposits on said cathode self-detaches or is removable by a method selected from the group consisting of brushing, scraping, vibrating and the use of liquid jets, until no more than a preselected amount of zinc remains in the solution, provided that the current density at the cathode is preselected so that in conjunction with the non-zinc-adherent characteristic of the cathode, the electrowon zinc will have, after homogenizing into particles, a density within the range 0.2-2.0 g/cc and a surface area within the range 0.5-6.0 m² /g;

removing zinc from the cathode and homogenizing it into particles;

combining said homogenized zinc particles with additional aqueous Group Ia metal hydroxide and optionally with other makeup components selected from the group consisting of water and inhibitor, thereby regenerating reconstituted charged slurry;

optionally analyzing said reconstituted charged slurry in order to ascertain whether at least the values of zinc, the Group Ia metal hydroxide and the inhibitor lie within preset limits; and

optionally adjusting the values of at least one of said aforementioned zinc, Group Ia metal hydroxide or inhibitor lie within preset limits for said reconstituted charged slurry.