Functionally Graded Infiltration Triggering Ultrahigh Electrolytic Current in Robust Reversible Solid Oxide Cells

The reversible solid oxide cell (ReSOC) offers the dual capability to store electricity as chemical fuels and convert fuels to electricity, thereby enabling carbon neutral cycling. The nickel‐cermet fuel electrode exhibits high electrocatalytic activity for redox reactions while being particularly vulnerable to carbon deposition and nickel coarsening, especially at high current densities. Herein, a novel approach involving a graded infiltration onto a dendritic Ni–YSZ (yttria‐stabilized zirconia) skeleton with Pr₆O₁₁ nanoparticles/films is presented, demonstrating remarkable electrolytic current and coke tolerance in CO–CO₂ conversion. At 800 °C, the current densities achieve approximately −2.0 and +2.0 A cm⁻² under 1.3 and 0.6 V, respectively, showcasing robust cycling stability switching between two operational modes within 20 cycles. Notably, the attained electrolytic current density reaches an unprecedented −3.06 A cm⁻² under 1.6 V. Furthermore, the button cell runs smoothly at ultrahigh electrolytic current densities ranging from −0.5 to −3.0 A cm⁻² for nearly 270 h. The mechanism of high‐performance CO₂ reduction is elucidated by in/ex situ experimental characterizations and theoretical calculations. These results indicate the viability of employing Ni–YSZ‐supported ReSOC for stable renewable electricity storage at previously unattainable reaction rates, and have implications for fundamental understanding of designing robust ReSOC based on the nickel‐cermet fuel electrode.