Cathode material chemical stability

To develop an alternative MIEC cathode not only the ex situ properties, e.g., cr, TEC, /), and k, but also the electrocatalytic activity, structural and chemical stability, and Cr-tolerance must be considered. Beyond testing in small SOFC button cells, the viability of new cathode materials must ultimately be proven in large-scale stack cells under practical current and temperature gradients. The issues involved in the development of cathode materials for large-scale stacks are significantly more complex than those in the small button cells briefly reviewed in this chapter. However, this does provide serious challenges as well as opportunities for materials scientists and engineers in the development of commercially viable ITSOFCs. 

Research on cathode materials focuses on reduction of the high chemical activity of the lower WF metals (e.g., Ca/Al), the increase of the chemical stability, and improvement of the sticking coefficient of the interlayer materials (e.g., LiF/Al). 

After the description of chemical structure and control of meso-architecture and surface area, selected applications of such carbon materials as battery electrodes, supercapacitors, and in the design of controlled hybrid heterojunctions were presented. In the Li battery, coating or hybridization with hydrothermal carbon brought excellent capacities at simultaneous excellent stabilities and rate performances. This was exemplified by hybridization with Si, Sn02 (both anode materials) as well as LiFeP04 (a cathode material). In the design of supercapacitors, porous HTC carbons could easily reach the benchmark of optimized activated traditional carbons, with better stability and rate performance. 

Preliminary work on alternate LiFe02 cathodes showed better chemical stability under the cathode environment and a lower dissolution rate. However, because of slower kinetics, the catalytic activity of this material for oxygen reduction is very poor when compared to the state-of-the-art NiO cathode. Because LiFe02 shows better performance than NiO under pressurized operation it is still under consideration to be used as a cathode material. ... 

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