A zinc/air depolarized cell wherein the anode comprises zinc particles, aqueous alkaline electrolyte, and pyrophosphate based (P 2 O 7 ) 4− additive. The cell may be in the form of a button cell. The addition of a pyrophosphate containing additive to the zinc anode improves the cell's service life regardless of whether the zinc is amalgamated with mercury or contains zero added mercury. The pyrophosphate based on (P 2 O 7 ) content preferably comprises between about 0.001 and 2 percent by weight of the anode.
1. A primary (non-rechargeable) zinc/air button cell comprising an anode can and a cathode can; an anode material comprising zinc particles, pyrophosphate (P 2 O 7 ) 4− based additive comprising potassium pyrophosphate (K 4 P 2 O 7 ), and aqueous alkaline electrolyte within said anode can; and a cathode within said cathode can; wherein said aqueous alkaline electrolyte comprises potassium hydroxide having a concentration of between 30 and 40 percent by weight therein; wherein the cathode can comprises an open end and opposing closed end and integral side wall therebetween; said cathode can closed end having at least one air hole therethrough and said cathode is in proximity to said air hole; wherein said anode can comprises an open end and opposing closed end and integral side wall therebetween; wherein the open end of the anode can resides within the open end of the cathode can with at least a portion of the cathode can side wall overlapping at least a portion of the anode can side wall with electrically insulating material between said overlapping wall portions.
2. The cell of claim 1 wherein the anode material comprises between about 0.001 and 2 percent by weight of pyrophosphate based additive calculated based on (P 2 O 7 ) content.
3. The cell of claim 1 wherein the anode material comprises between about 0.003 and 1 percent by weight pyrophosphate based additive calculated based on (P 2 O 7 ) content.
4. The cell of claim 2 wherein said anode comprises between about 77 and 83 percent by weight zinc and between about 17 and 23 percent by weight of said alkaline electrolyte.
5. The cell of claim 4 wherein said alkaline electrolyte comprises potassium hydroxide having a concentration therein of between about 33 and 40 percent by weight.
6. The cell of claim 2 wherein the zinc/electrolyte weight ratio in said anode is between about 3.3 and 4.9.
7. The cell of claim 2 wherein the zinc/electrolyte weight ratio in said anode is between about 4.0 and 4.9.
8. The cell of claim 6 wherein said alkaline electrolyte comprises potassium hydroxide having a concentration therein of between about 33 and 40 percent by weight.
9. The cell of claim 7 wherein said alkaline electrolyte comprises potassium hydroxide having a concentration therein of between about 33 and 40 percent by weight.
10. The cell of claim 1 wherein said cell has an overall diameter of between about 4 and 20 mm and an overall height of between about 2 and 9 mm.
11. The cell of claim 1 wherein said cell comprises less than 100 parts by weight mercury per million parts by weight zinc.