The Effects of Nickel Oxide Cathode Dissolution on Molten Carbonate Fuel Cell Life

Abstract

The dissolution of lithiated nickel oxide cathodes results in a transport of nickel into the fuel cell matrix and can result in an electronic short circuit between the electrodes. A theoretical analysis was developed for this process, accounting for the dissolution, diffusion, transference, and convection of nickel. Experimental data obtained on post-test nickel content in matrices and shorting time were found to be correlated by this theory, except for a current density effect that was underpredicted. This poor prediction of the current density effect is postulated to be caused by cation segregation during cell operation. These results enable the estimation of matrix nickel content and shorting time as a function of cell design and operating conditions.

Corrosion phenomena of alloys and electrode materials in Molten Carbonate Fuel Cells

“…This is typical for a cross-flow system, because most of the electrochemical current is produced in this corner, where the highest H 2 pressure in the fuel gas is directly connected with the highest CO 2 and O 2 partial pressures in the cathode gas. The amount of precipitated Ni in the FI/OI-corner was in the range of 15 ± 16 mg Ni /cm 2 , which is very close to the expected amount of Ni to short the cell (20 ± 25 mg Ni /cm 2 ) [45,46]. This ªoldº matrix type A embodies the Ni support, which is slightly oxidized during the start up procedure of the fuel cell, because the matrix is not seal in the start-up.…”

Research, Development, and Demonstration of Molten Carbonate Fuel Cell Systems

“…This is in agreement with model predictions based on a more extensive analysis of the shorting phenomenon, in part based on empirical correlations. 92 Several aspects of cathode dissolution nevertheless remain poorly understood. NiO dissolution can be suppressed to a considerable degree by additives which increase the basicity of the electrolyte within the cathode.…”

Theoretical predictions vs. experimental measurements of the electrical conductivity of molten Li2CO3–K2CO3 modified by additives

“…Among the solutions to overcome the degradation problem and to maintain the cell performance is the control of the electrolyte oxoacidity by adding a few percent of cations favouring the basicity, such as alkali earth, Mg, Ca, Sr and Ba [5e11]. Other elements such as Fe, La and W have also been added to the Li 2 CO 3 eK 2 CO 3 eutectic [12e15]; they inhibit the NiO dissolution but problems of cation segregation were observed at long-term cell operation [16]. Ota et al [17] have also analysed the effect of the addition of Ho, Yb and Nd oxides in different carbonate eutectics.…”