Investigation of plasma sprayed Sr0·7La0·3TiO3 / La0·2Sr0·8MnO3 Bi-layer interconnector performance and its application in high power tubular solid oxide fuel cells

Abstract

Atmospheric plasma spraying (APS) has been demonstrated as an efficient and rapid method for manufacturing high-performance solid oxide fuel cells (SOFCs), with interconnects serving as the “wires” for large-scale integration of SOFCs. However, the challenge of producing highly conductive and stable interconnects through plasma spraying remains unresolved. This study developed a Bi-layer perovskite interconnect for segmented-in-series solid oxide fuel cell (SIS–SOFCs). It involved APS-prepared dense N-type interconnects of Sr0·7La0·3TiO3 (LST), achieving low porosity, low leakage rate, and high conductivity LST coatings. The element of Ti valence state changes and conductivity of LST powders, hydrogen-treated powders, LST coatings, and hydrogen-treated coatings were quantitatively analyzed through phase detection and elemental valence state analysis under different oxygen partial pressure conditions to explore the variation of LST coating conductivity. Simultaneously, bi-layer interconnector model using La0·2Sr0·8MnO3(LSM)as the P-type interconnect was established to elucidate the electron transport mechanism within the Bi-layer interconnect under operating conditions and propose optimization schemes for the structural design of tubular serial-connected cell interconnects. The tubular dual-cell combination using LST/LSM Bi-layer interconnectors exhibited a maximum power density of 360 mW/cm2 at 800 °C, with only 33% interconnector loss compared to the maximum power density of 540 mW/cm2 achieved by a single cell at 800 °C. Additionally, it attained the highest open circuit voltage (1.9 V) at 650 °C. This Bi-layer interconnectors has been successfully applied in serial-connected tubular cells with more than 5 cells. Furthermore, the dual-cell combination showed almost no performance loss under 100 h of constant current discharge (0.3 A/cm2) testing. These research findings indicate that the LST/LSM Bi-layer interconnectors prepared using atmospheric plasma spraying is an ideal material system for the functional layer of interconnects in high-power tubular segmented-in-series solid oxide fuel cell structures.