Methods for production of zinc oxide electrodes for alkaline batteries
View Patent ↗A zinc electrode for use in alkaline batteries comprises a mixture of 0.425 to 1.55 volume parts of zinc oxide with a volume part of a metallic oxide chosen from the group consisting of: calcium oxide, barium oxide, and mixtures thereof, together with hydroxy-ethyl cellulose, an oxide dispersant chosen from the group consisting of: soap derivatives, anionic polyelectrolytes, anionic surfactants, and mixtures thereof, and a binder. The electrode is prepared by mixing zinc oxide with the chosen metallic oxide in an aqueous medium such as water or potassium hydroxide, stirring overnight, filtering and drying the mixture, optionally adding a further small amount of zinc oxide, optionally adding other metallic oxides, and adding hydroxy-ethyl cellulose, an oxide dispersant, and a binder. The aqueous paste os slurry thus formed is placed on a conductive substrate, drawn through a sizing gap, cut and dried, to form low cost pasted zinc oxide electrodes.
1. A method for production of zinc oxide electrodes for use in alkaline batteries characterized by the steps of:
a) preparing an aqueous suspension of a metallic oxide chosen from the group consisting of: calcium oxide by placing the chosen metallic oxide in an aqueous medium to form the aqueous suspension;
b) adding zinc oxide to the aqueous medium of the chosen metallic oxide;
c) stirring the aqueous suspension to promote formation of calcium zincate;
d) drying the stirred mixture;
e) preparing an aqueous paste or slurry comprising the dried mixture from d), an oxide dispersant, and a liquid binder and
f) coating or pasting the aqueous paste or slurry onto a conductive substrate.
2. The method of claim 1 , wherein when said aqueous medium is water, step (c) is carried out at room temperature; and when said aqueous medium is potassium hydroxide solution, step (c) is carried at 50° C. to 75° C.
3. The method of claim 1 , wherein said liquid binder is dispersed PTFE.
4. The method of claim 1 , wherein the aqueous medium employed in a) comprises water or a potassium hydroxide solution.
5. The method of claim 1 , wherein a) comprises placing 0.1 to 2.0 volume parts of the chosen metallic oxide in 20 volume parts of the aqueous medium.
6. The method of claim 1 , wherein b) comprises adding zinc oxide to the aqueous suspension in an amount of 0.4 to 1.5 times the volume of the chosen metallic oxide in the suspension.
7. The method of claim 1 , wherein c) comprises stirring the aqueous suspension for a period of 1 to 12 hours.
8. The method of claim 1 , wherein d) comprises:
filtering the stirred mixture;
drying the filtered mixture at a temperature of 45° C. to 75° C. to form a powdered mixture.
9. The method of claim 1 , further comprising adding an additional 0.025 to 0.05 volume parts of zinc oxide to the dried mixture.
10. The method of claim 1 , further comprising adding a further metallic oxide chosen from the group consisting of: bismuth oxide, indium oxide, tin oxide, and mixtures thereof, to the dried mixture.
11. The method of claim 1 , wherein the oxide dispersant is selected from the group consisting of: anionic polyelectrolytes, anionic surfactants, and mixtures thereof.
12. The method of claim 1 , wherein the aqueous paste or slurry further comprises a cellulose compound.
13. The method of claim 12 , wherein the cellulose compound is hydroxyl-ethyl cellulose.
14. The method of claim 1 , further comprising:
g) drawing the coated or pasted conductive substrate through a gap having a predetermined dimension so as to fix the thickness of the electrode being manufactured; and
h) drying and cutting the electrode to size.