Quantitative analysis for fracture behavior of fuel cells

Abstract

Fuel cell has received attention for eco-friendly and sustainable energy system. The fuel cells, which convert the chemical energy of fuel into the electrical energy, are classified with the type of electrolyte. PEMFC uses a proton-conducting polymer and SOFC uses an oxide ion-conducting ceramic material as the electrolyte. However, the reliability issues, such as mechanical degradation, has impeded the commercialization of fuel cell systems. To achieve the reliability and durability of the fuel cell, the fracture behavior of fuel cells was investigated. Cracks of PEMFC and interfacial robustness of SOFC were examined to analyze fracture behavior of the fuel cells. Cracks of PEMFC were quantified by crack area density and electrical resistance with electromechanical tests. Crack growth behavior showed difference with respect to the thickness of electrode. Thicker anode had larger and fewer cracks. For SOFCs, interfacial fracture energy was measured by double cantilever beam and subcritical crack growth tests were performed in humid environments. Threshold values of strain energy release rate were 0.04 and $0.03 J m^{-2}$ when relative humidity was 60 and 90 %. SEM observations were also conducted to inspect the surface and the interface precisely. The results have potential in the reliability improvement of fuel cells.