Multi-Physical and Electrochemical Coupling Model for the Protonic Ceramic Fuel Cells with H+/e−/O2− Mixed Conducting Cathodes

Improving the electrochemical energy conversion of solid oxide fuel cells through the interface effect in La0.6Sr0.4Co0.2Fe0.8O3-δ-BaTiO3-δ electrolyte

Herein, we present a heterostructure electrolyte with considerable potential for application in low-temperature solid oxide fuel cells (LT-SOFCs). Heterostructure electrolytes are advantageous because the multiphase interfaces in their heterostructures are superior for ion conduction than for bulk conduction. Most previous studies on heterostructure electrolytes explained the influence of interfacial parameters on ion conduction in terms of the space charge zones and lattice mismatch, neglecting the characterization of the interface. In this study, a series of heterostructure electrolytes comprising La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) and BaTiO_3-δ (BTO) with different composition ratios was developed. Further, the lattice mismatch due to thermal stress in this system was evaluated by thermal expansion and electron energy loss spectroscopy (EELS) analyses. Results indicated that 7LSCF-3BTO produced the narrowest interface and the most surface oxygen vacancies, suggesting that the stress generated by thermal expansion increased the density of the interface. The cell with the optimal 7LSCF-3BTO composition delivered a peak power density of 910mW cm^-2 and an open circuit voltage of 1.07 V at 550 °C. The heterojunction effect was studied to elucidate the prevention of short circuiting in the LSCF-BTO cell, considering the Femi level and barrier energy height. This study provides novel ideas for the design of electrolytes for LT-SOFCs from the interface perspective.

Spectral Element-Based Multi-Physical Modeling Framework for Axisymmetric Wireless Power Transfer Systems

This paper concerns a multi-physical modeling framework based on the spectral element method (SEM) for axisymmetric wireless power transfer systems. The modeling framework consists of an electromagnetic and a thermal model. The electromagnetic model allows for eddy currents in source- and non-source regions to be included in the analysis. The SEM is a numerical method, which is particularly advantageous in 2D problems for which the skin-depth is several orders of magnitude smaller compared to the object dimensions and complex geometrical shapes are absent. The SEM applies high-order trial functions to obtain the approximate solution to a boundary-value problem. To that end, the approximation is expressed as an interpolation at a set of nodal points, i.e., the nodal representation. The trial functions are Legendre polynomials, which reduces the complexity of the formulation. Furthermore, numerical integration is performed through Gaussian quadratures. In order to verify the SEM, a benchmark system is modeled using both the SEM and a finite element-based commercial software. The differences in the SEM solutions, i.e., magnetic vector potential and temperature distribution, and the discrepancies in essential post-processing quantities are assessed with respect to the finite element solutions. Additionally, the computational efforts of both methods are evaluated in terms of the sparsity, number of degrees of freedom, and non-zero elements.