Electrical storage cell resistant to freezing

DETAILED DESCRIPTION The present invention provides a modified electrical storage cell construction for nickel-hydrogen and similar types of cells.
The invention permits the use of the optimum electrolyte and yet avoids the freezing of the electrolyte during discharge, in ambient operating temperatures a few degrees above the freezing temperature of the electrolyte.
That is, the electrolyte that is optimized for electrical performance is not changed in order to attain the improved low-temperature resistance to freezing of the cell.
The operating performance of the cell is not adversely affected.
The performance to weight ratio is thereby maintained, while the temperature range for operation is increased.
In accordance with the invention, an electrical storage cell that is resistant to freezing comprises storage means including a plurality of active plate sets, each plate set including a positive electrode, a porous hydrogen negative electrode, and a separator between the positive electrode and the negative electrode, the hydrogen negative electrode having a thickness of at least about 0.
007 inches; and a pressure vessel that contains the plate sets.
The prior negative electrode of a nickel-hydrogen storage cell typically is an etched or mesh nickel substrate having a layer bonded thereto.
The bonded layer is formed of platinum powder in a binder material such as polytetrafluoroethylene, trademark of E.
I.
Dupont deNemours Co.
The total thickness of the negative electrode is made very thin to save weight.
The substrate is about 0.
003 inches thick and the layer of platinum in a binder is about 0.
003 inches thick, for a total thickness of about 0.
006 inches.
When the cell discharges during the discharge portion of its cycle, a chemical reaction occurs at the negative electrode.
The half cell reaction at the negative electrode is represented by the expression: H.
sub.
2 +2OH-=2H.
sub.
2 O+2e- Water is produced at the negative electrode.
The present inventors have discovered that the water so produced tends to dilute the electrolyte in and immediately adjacent to the negative electrode