Progress on direct assembly approach for in situ fabrication of electrodes of reversible solid oxide cells

Reversible solid oxide cells (SOCs) are very efficient and clean for storage and regeneration of renewable electrical energy by switching between electrolysis and fuel cell modes. One of the most critical factors governing the efficiency and durability of SOCs technology is the stability of the interface between oxygen electrode and electrolyte, which is conventionally formed by sintering at a high temperature of ~1000–1250 ​°C, and which suffers from delamination problem, particularly for reversibly operated SOCs. On the other hand, our recent studies have shown that the electrode/electrolyte interface can be in situ formed by a direct assembly approach under the electrochemical polarization conditions at 800 ​°C and lower. The direct assembly approach provides opportunities for significantly simplifying the cell fabrication procedures without the doped ceria barrier layer, enabling the utilization of a variety of high-performance oxygen electrode materials on barrier layer–free yttria-stabilized zirconia (YSZ) electrolyte. Most importantly, the in situ polarization induced interface shows a promising potential as highly active and durable interface for reversible SOCs. The objective of this progress report is to take an overview of the origin and research progress of in situ fabrication of oxygen electrodes based on the direct assembly approach. The prospect of direct assembly approach in the development of effective SOCs and in the fundamental studies of electrode/electrolyte interface reactions is discussed.