New interconnector design optimization to balance electrical and mechanical performance of solid oxide fuel cell stack

Abstract

Mechanical stability and integrity are the pre-requisites for the long-term stable high power output of solid oxide fuel cell (SOFC) stacks. However, most of the previous research concentrated on improving the electrochemical performance of SOFC stacks, while the mechanical stability is rarely studied. In this study, a three-dimensional electro-thermo-mechanical coupled model is established to study the impact of interconnector (IC) structure on electrical performance and mechanical stability of SOFC simultaneously. It reveals that IC design with discrete ribs can enhance the maximum power density by up to 12.96%. The maximum principal stress value of positive electrode-electrolyte-negative electrode (PEN) is slightly influenced by IC design, while the stress distribution characteristic is obviously dominated by geometrical structure of IC. Compared with symmetrically arranged ICs at anode and cathode side, the unsymmetrical IC design with regularly discrete cubic, staggered discrete cubic, and discrete cylindrical ribs at cathode side and traditional IC design at anode side can respectively decrease the thermal stress of IC by 19.31%, 6.39%, and 12.09%, while the thermal stress of IC can be further released by 29.44% and 16.44% by rounding the corners of regularly arranged, and staggered distributed cubic ribs. By using new IC design, the failure probability of PEN is reduced by up to 28.97%, while increased by 8.37% only for the case with traditional IC at anode side and staggered cubic ribs at cathode side. To balance the electrical power output and mechanical stability, the discrete cylindrical ribs and discrete cubic ribs with rounded corners are better choices.