Non-proprietary stack research

Abstract

Ohmic resistance loss in a state-of-the-art carbonate fuel cell contributes about 65 mV loss at BOL (beginning-of-life). It may increase to about as much as 145 mV after 40,000 hours. Its reduction will offer further improvement in fuel cell power plant efficiency. The important resistance contributing elements/interfaces are illustrated in Figure 1. The majority of the ohmic loss is attributed to electrolyte matrix (ionic) and cathode-side hardware (electronic). The ohmic loss due to electrodes and anode-side hardware can generally be neglected. The matrix ionic resistance is influenced by many factors: electrolyte conductivity, matrix porosity, tortuosity, electrolyte fill level and matrix thickness. At present, matrix contributes to > 300 m[Omega]cm[sup 2] (>70% of the total cell ohmic resistance) and is the major resistance contributor. The oxide formed at the cathode-CCC (cathode current collector) interface is the major cause of the cathode-side hardware resistance (contributing about 60 m[Omega]cm[sup 2]). For carbonate fuel cell to be economically viable, a 40,000h life is needed. Therefore, resistance stability for such a long-term operation is very important. Based on the above discussion, more understanding on ohmic resistance, particularly its increase, is needed for better recommending approaches to further reduce the ohmic resistance.