Electrochemical cells having a gelled anode-electrolyte mixture

• US 4,455,358 A
• Filed: 12/26/1979
• Issued: 06/19/1984
• Est. Priority Date: 12/26/1979
• Status: Expired due to Term

• Current Assignee: Duracell Incorporated (Berkshire Hathaway Incorporated)
• Original Assignee: Duracell Incorporated (Berkshire Hathaway Incorporated)
• Inventors: Graham, Teresita O., Goodman, John T.
• Primary Examiner(s): LeFevour, Charles F.
• Application Number:
  US06/106,996
• Time in Patent Office: 1,637 Days
• Field of Search: 429/212, 429/214, 429/215, 429/216, 429/217, 429/190, 252/315-317, 260/17.4 R, 260/17.4 GC, 260/17.4 ST, 260/17.4 CL
• US Class Current: 429/301
• CPC Class Codes: H01M 4/06 Electrodes for primary cells
• CPC Class Codes: H01M 4/621 Binders
• CPC Class Codes: H01M 6/22 Immobilising of electrolyte

Abstract

An electrochemical cell having an anode, a cathode and an aqueous alkaline electrolyte solution. The anode is an intimate gelled mixture of a powdered metal, an aqueous electrolyte solution and an agent capable of gelling the mixture. The agent is a material capable of absorbing water and having a carbohydrate backbone which has a water soluble side chain grafted thereon. A preferred agent is a water insoluble salt of an aqueous alkali saponified gelatinized starch having a water soluble side chain grafted thereon. The gelling of the intimate mixture of the powdered metal anode and electrolyte solution with the agent is a method of improving the discharge characteristics of the cell.

Claims

1. An electrochemical cell comprising an anode, an aqueous alkaline electrolyte solution, a separator and a cathode, said anode comprising an intimate gelled mixture of a powdered metal, aqueous alkaline electrolyte solution and an agent capable of gelling said mixture, said agent comprising a material capable of absorbing water, said agent comprising a carbohydrate backbone having water soluble side chains grafted thereon.

2. The cell of claim 1 wherein said side chains are ionized.

3. The cell of claim 1 wherein said anode metal comprises zinc.

4. The cell of claim 1 wherein the carbohydrate comprises starch.

5. The cell of claim 1 wherein said side chain is selected from the group consisting of acrylonitrile, acrylamide, acrylic acid, methyl methacrylate, acrylic acid ester, vinylacetate, N-vinyl-2 pyrrolidone, salts of alginic acid, gluconic acid, and mixtures of these.

6. The cell of claim 1 wherein the side chain has been chemically grafted to said carbohydrate.

7. An electrochemical cell comprising an anode, an aqueous alkaline electrolyte solution, a separator, and a cathode, said anode comprising an intimate gelled mixture of powdered metal, aqueous electrolyte solution, and an agent capable of gelling said mixture, said agent comprising a water insoluble salt of an aqueous alkali saponified material comprising a gelatinized starch backbone having water soluble side chains grafted thereon, and containing gelatinized starch and saponified side chain in molar ratios of from about 1:

1 to 1;

9.

8. The cell of claim 7 wherein said side chain is selected from the group consisting of acrylonitrile, acrylamide, acrylic acid, methyl methacrylate, acrylic acid ester, vinylacetate, N-vinyl-2 pyrrolidone, salts of alginic acid, gluconic acid, and mixtures of these.

9. The cell of claim 8 wherein said side chain comprises acrylonitrile.

10. The cell of claim 7 wherein said electrolyte solution comprises an aqueous solution of a hydroxide having a cation selected from the group consisting of alkali and alkaline earth metals.

11. The cell of claim 7 wherein the water insoluble salt comprises an alkaline salt.

12. A powder-gel anode comprising a major portion of a consumable zinc anodic material, a minor amount of a starch-graft copolymer in which the copolymer contains carboxylate units, and an aqueous alkaline electrolyte solution.

13. The powder-gel anode of claim 12 wherein the consumable zinc anodic material is a powder.

14. The powder-gel anode of claim 13 wherein the starch graft copolymer is present in an amount between about 0.6 and about 11% by weight of the anodic material.

15. The powder-gel anode of claim 14 wherein the starch graft copolymer is present in an amount between about 0.6 and about 4% by weight of the anodic material.

16. The powder-gel anode of claim 12, 13, 14, or 15 wherein the electrolyte solution is aqueous potassium hydroxide.

17. An alkaline-MnO₂ cell employing an aqueous alkaline electrolyte solution and a powder-gel anode comprising a major portion of a consumable zinc anodic material, a minor amount of a starch graft copolymer in which the copolymer contains carboxylate units, and an aqueous electrolyte solution.

18. The alkaline-MnO₂ cell of claim 17 wherein the electrolyte solution is aqueous potassium hydroxide.

19. The alkaline-MnO₂ cell of claim 17 or 18 wherein the starch graft copolymer is present in an amount between about 0.6 and about 11% by weight of the anodic material in the cell.

20. The alkaline-MnO₂ cell of claim 17 or 18 wherein the starch graft copolymer is present in an amount between about 0.4 and about 6.4% by weight of the total electrolyte solution.