Thickness-gradient electrolytes for homogenizing the current distribution in solid oxide fuel cells

Abstract

In planar solid oxide fuel cells (SOFCs), operation at high fuel utilization inevitably induces strong fuel concentration gradients along the flow direction, leading to pronounced non-uniformity in current density distribution. Here, a thickness-gradient electrolyte strategy is proposed to homogenize the current distribution by deliberately modulating the local ohmic resistance, suppressing current density in fuel-rich inlet regions while enhancing it in fuel-depleted outlet regions. A gradient YSZ electrolyte with a thickness ranging from 5 to 13 μm was successfully fabricated on a 10 cm × 10 cm single cell via a wet-spraying process, together with a dense 1.8 μm gadolinia-doped ceria (GDC) barrier layer formed by in situ hydrothermal self-crystallization. Compared with conventional uniform-thickness electrolytes, the gradient electrolyte effectively reduces current density gradients and achieves improved current distribution uniformity under comparable fuel utilization conditions. Combined experimental characterization and multiphysics simulations demonstrate that the proposed gradient-electrolyte design significantly alleviates both current density non-uniformity and the associated thermal gradients in SOFCs operating at high fuel utilization. Overall, this work establishes a simple and scalable design strategy for regulating internal physical fields in SOFCs, offering a promising pathway toward improved conversion efficiency and enhanced durability under practically relevant operating conditions.

Graphical abstract

Keywords

solid oxide fuel cell (SOFC) / electrolyte thickness gradient / current density distribution / temperature distribution

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