Thermal stress analysis at the interface of cathode and electrolyte in solid oxide fuel cells

A benign thermal stress in solid oxide fuel cell is of great importance for its stability and the interfaces between different components suffer from unexpected risks of instability such as electrode delamination and crack due to varying thermal expansion coefficients. Besides, chromium poisoning cathode materials leads to phase changes, which possibly induces thermal stresses at the interface of electrolyte and cathode. A three dimensional model at the microscale level is thus developed to unravel the effect of thermal stress on the interface. The model is constructed by governing equations including heat, species, momentum, ion and electronic transportation. The contact modes between the active cathode and electrolyte are studied to reveal the cell performance and thermal stresses, which are strongly related to the number of contact sites and the contact area. Moreover, chromium poisoning the contact causes the disordered distribution of thermal stresses with the increase of the contact sites, worsening the cell current density and durability. The resulting conclusions are expected to offer a solution to avoid possible fatal mechanical failure due to unfavorable interface design and chromium attack.