High temperature galvanic fuel cells with fused carbonate paste electrolytes—I. General considerations and experimental results

Abstract

Completely gas-tight high-temperature cells can be constructed by using electrolytes in so-called paste form. The paste is a blend of 70−50 weight per cent of an inert finely powdered material such as MgO, and 30−50 per cent of a lithium-sodium-potassium carbonate melt. It behave as a deformable solid with very low specific resistance.

In combination with nickel powder (or sieve) fuel electrodes and silver powder (or screen) air electrodes H₂ + CO₂ mixtures, as well as hydrocarbons, with added steam, can be utilized in such cells at 600–700°C. The cell life appears to be related to the current density drawn. At 25 mA/cm², practically constant voltages (0·85−0·90 V) can be maintained for periods of more than three months. Until recently, however, current densities of 100–150 mA/cm² caused severe deterioration of the fuel electrode within one or two weeks, at 700°C.

By improvement of the paste-electrolyte properties, the authors recently succeeded in avoiding the mentioned instability to a great extent. With essentially unmodified silver and nickel electrodes, continuous currents of 100 mA/cm² at about 700 mV, may be drawn for at least 3100 hr. †

The corresponding specific power output of 0·70 kW/m² reaches the level at which at least the cost price of the electrodes and the electrolyte remains below $75/kW.

At this power level the construction of a 5–10 kW battery becomes attractive, since it is felt that only experimental study on such a unit may reveal a realistic estimate of the true costs.

The recent discoveries of huge quantities of natural gas in the Dutch province of Groningen—at least gas—are a great impetus for studies of this kind.