Electrolyte Matrix by the Allis Chalmers Manufacturing Company

The fuel cells developed at the Allis-Chalmers Manufacturing Company used an "electrolyte vehicle," a porous matrix, to hold the alkaline electrolyte stationary (Wynveen and Kirkland, 1962). Fuel cell systems were made simpler with an immobilized electrolyte, which did away with the pumps and tubes of the circulation system. The matrix, made of sheet asbestos (as thin as 0.01 in or 254 |m), was filled with a controlled volume of the electrolyte before being sandwiched by the hydrogen and oxygen electrodes, both made of porous sintered nickel sheet (0.028 in thick) impregnated with a mixture of platinum and palladium. The pores of the electrodes were larger than those of the matrix, so because of the lower capillary potential associated with the larger pores, the electrolyte remained within the pores of the matrix. Also, making the electrodes wetproof was unnecessary because of the electrolyte vehicle. Therefore, this design used the electrolyte vehicle to contain the liquid instead of using the electrode as was done in Bacon's double-porosity electrodes and Justi and Winsel's double-skeleton and double-layer electrodes. The three layers together could have measured as thin as 0.066 in (0.17 cm), but the battery also included plates for gas distribution, support, and water transport membranes.

The pores of the asbestos sheet had a "high capillary potential," which means they required a high pressure to force a gas bubble through the largest pore in the matrix. With the matrix separating the hydrogen and oxygen electrodes, it required a pressure difference of 100 psi to force the gases through the pores of the asbestos to the opposite electrode. In simulations for space applications, the cells were tested with accelerations over ten times that of gravity, in zero gravity, and with shocks, tolerating these conditions and maintaining a constant performance because of the immobilized electrolyte. Water was removed from the cell by the hydrogen stream, and the removal rate could be adjusted by changing the gas flow; the oxygen was fed into a nearly dead-ended compartment. A battery of four cells, with total electrode area of 217 cm2 (33.6 in2) could give an average of 0.8 V per cell at a current density of 108 mA/cm2 (100 A/ft2) at 65 ± 3°C and 0 to 5 psig.

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