Multifactor theoretical analysis of current leakage in proton-conducting solid oxide fuel cells

In proton-conducting solid oxide fuel cells (H-SOFCs), current leakage, caused by the non-negligible electronhole conductivity of electrolytes, is an important concern for cell performances and efficiency. Understanding the influencing factors of current leakage and the interaction effects of different factors are critical. In this study, an electrochemical model, with considering the inhomogeneous distribution of electron-hole conductivity within the electrolyte layer and the thermodynamics of defect formation, is built for multifactor investigation of the current leakage and the cell performances. An analytical solution of leakage current is derived, in which the influencing factors of current leakage are explicitly illustrated. Comprehensive conclusions are clearly achieved with the simulation results: (a) the positive effect of increasing electrolyte thickness on suppressing current leakage becomes pronounced in the situation of high electron-hole conductivities and poor electrode performances; (b) as the electron-hole conductivity is increased, the Faraday efficiency, energy efficiency, and power density decline monotonously and linearly, and the decline rate grows with the thinning the electrolyte layer; (c) boosting the electrode performance can mitigate the voltage and current loss caused by current leakage. The results of this study can provide new insight and valuable guidelines for the rational design and optimization of H-SOFCs.