Voltage and reduced polarization within mercury free zinc air cells
The present disclosure is directed to a zinc air cell with improved voltage and reduced polarization. The combination of an anode corrosion inhibitor with a surfactant system yields enhanced cell voltage and capacity for the cell that are above the individual contributions of the corrosion inhibitor and the surfactant system.
1. An anode mix for an alkaline electrochemical cell, the anode mix comprising a polyaniline corrosion inhibitor and an electrolyte comprising a gelling agent and a surfactant system, wherein the surfactant system comprises a hexyl diphenyl oxide disulfonic acid surfactant and at least one amphoteric surfactant; wherein:
the alkaline electrochemical cell is a zinc-air cell;
the hexyl diphenyl oxide disulfonic acid surfactant is present in an amount of from about 500 ppm to about 5,000 ppm, by weight of the electrolyte;
the at least one amphoteric surfactant is present in an amount of from about 500 ppm to about 5,000 ppm, by weight of the electrolyte; and
the polyaniline is present in an amount of from about 100 ppm to about 500 ppm, by weight of the anode mix.
2. The anode mix of claim 1 , wherein the at least one amphoteric surfactant has a formula
wherein:
R 1 is an alkyl group having between 8 and 30 unbranched carbon atoms;
R 2 is an alkyl group having between 1 to about 6 unbranched carbon atoms, optionally substituted with 1 or more hydroxyl substituents;
R 3 is selected from a polyethylene oxide group having between 3 and 40 ethylene oxide units and a polypropylene oxide group having between 1 to 10 propylene oxide units; and
X is an anionic acid group, an anionic acid ester, or an alkali metal salt of an anionic acid or acid ester.
3. The anode mix of claim 1 , wherein the at least one amphoteric surfactant has a formula
wherein
R 4 is an unbranched alkyl group having between 8 and 30 unbranched carbon atoms that form an aliphatic fatty amine when bound to the nitrogen atom;
R 5 is selected from a polyethylene oxide group having between 3 and 40 ethylene oxide units and a polypropylene oxide group having between 1 and 10 propylene oxide units; and,
R 6 is selected from hydrogen, a polyethylene oxide group having between 3 and 40 ethylene oxide units and a polypropylene oxide group having between 1 and 10 polypropylene oxide units.
4. The anode mix of claim 1 , wherein the surfactant system comprises a mixture of amphoteric surfactants, wherein the first amphoteric surfactant has a formula
wherein:
R 1 is an alkyl group having between 8 and 30 unbranched carbon atoms;
R 2 is an alkyl group having between 1 to about 6 unbranched carbon atoms, optionally substituted with 1 or more hydroxyl substituents;
R 3 is selected from a polyethylene oxide group having between 3 and 40 ethylene oxide units and a polypropylene oxide group having between 1 to 10 propylene oxide units; and
X is an anionic acid group, an anionic acid ester, or an alkali metal salt of an anionic acid or acid ester; and the second amphoteric surfactant has a formula
wherein
R 4 is an unbranched alkyl group having between 8 and 30 unbranched carbon atoms that form an aliphatic fatty amine when bound to the nitrogen atom;
R 5 is selected from a polyethylene oxide group having between 3 and 40 ethylene oxide units and a polypropylene oxide group having between 1 and 10 propylene oxide units; and,
R 6 is selected from hydrogen, a polyethylene oxide group having between 3 and 40 ethylene oxide units and a polypropylene oxide group having between 1 and 10 polypropylene oxide units.
5. The anode mix of claim 1 , wherein the surfactant system comprises a mixture of amphoteric surfactants, wherein the mixture comprises one or more polyethoxylated fatty amino carboxylates and one or more polyethoxylated fatty amines.
6. The anode mix of claim 1 , wherein the polyaniline is a polyaniline emeraldine base.
7. The anode mixt of claim 1 , wherein the gelling agent comprises a polyacrylic acid polymer.