Low-temperature processing technique of Ruddlesden-Popper cathode for high-performance solid oxide fuel cells

Highlights: • High-performance lanthanum nickelate-based cathode is fabricated. • The sinterability of cathode is enhance by compositional modification. • Harmful chemical reactions are suppressed by lowering processing temperatures. • The cell with lanthanum nickelate cathode outperforms state-of-the-art cells. -- Abstract: The Ruddlesden-Popper phase lanthanum nickelate, La₂NiO_4+δ (LNO), offers excellent material properties as a cathode for solid oxide fuel cells (SOFCs). However, taking full advantage of its intrinsic properties is difficult in realistic cells because of its high chemical reactivity with the electrolyte at elevated temperatures. Herein, we demonstrate high-performance SOFCs with an LNO-based cathode fabricated by a low-temperature processing route that suppresses harmful chemical reactions. The sintering capability of the composite cathode composed of LNO and gadolinia-doped ceria (GDC) was enhanced by mixing Fe-based sintering additive with GDC, which formed reliable interfacial bonding with the electrolyte at a temperature ~200 °C below the typical processing temperature. Because no interdiffusion between cathode and electrolyte occurs at such low temperatures, the cell is successfully fabricated without diffusion blocking layer, which simplifies the cell structure and manufacturing process. The cell with the LNO-based cathode outperformed state-of-the-art cells, particularly at lower operating temperatures. These results highlight that the processing parameters strongly affect the electrochemical performance of this LNO-based cathode and must be carefully engineered to fully exploit its superior intrinsic properties.