Yonghyun Lim

Single-chamber fabrication of high-performance low-temperature solid oxide fuel cells with grain-controlled functional layers

A one-step process has been developed for the fabrication of thin film membrane–electrode assemblies with multi-layer electrolytes for use in high-performance, low-temperature solid oxide fuel cells (LT-SOFCs). By controlling the sputter processing conditions, a dense yttria-stabilized zirconia (YSZ) electrolyte film was fabricated onto a porous aluminum oxide (AAO) anodic substrate. Thin, grain-controlled layers (GCLs) were subsequently formed at the cathodic interface to provide a homogeneous functional layer, which significantly enhanced the kinetics of the oxygen reduction reaction (ORR). This is attributed to the fine grains and increased grain boundary density of this layer, which were achieved without thermal annealing. Using this new device architecture, the fuel cell was able to reach a peak power density of 343 mW cm−2 at 450 °C.

A homogeneous grain-controlled ScSZ functional layer for high performance low-temperature solid oxide fuel cells

Scandia-stabilized zirconia (ScSZ) is employed as a cathodic functional layer onto yttria-stabilized zirconia based fuel cell systems for low-temperature solid oxide fuel cells. In order to overcome the relatively poor material properties in terms of surface reaction rate, the grain structure and the degree of crystallinity of ScSZ thin films were modified by controlling the RF power during the thin-film fabrication process via sputtering. The concept of grain-controlled layers (GCLs) was applied at the cathode-electrolyte interface to enhance the surface reaction rate by catalyzing the oxygen reduction reaction. By adopting this novel concept, the thin-film fuel cell fabricated with ScSZ GCLs could achieve a peak power density of 479 mW cm−2 at 450 °C.

Rapid, cool sintering of wet processed yttria-stabilized zirconia ceramic electrolyte thin films

Here we report a photonic annealing process for yttria-stabilized zirconia films, which are one of the most well-known solid-state electrolytes for solid oxide fuel cells (SOFCs). Precursor films were coated using a wet-chemical method with a simple metal-organic precursor solution and directly annealed at standard pressure and temperature by two cycles of xenon flash lamp irradiation. The residual organics were almost completely decomposed in the first pre-annealing step, and the fluorite crystalline phases and good ionic conductivity were developed during the second annealing step. These films showed properties comparable to those of thermally annealed films. This process is much faster than conventional annealing processes (e.g. halogen furnaces); a few seconds compared to tens of hours, respectively. The significance of this work includes the treatment of solid-state electrolyte oxides for SOFCs and the demonstration of the feasibility of other oxide components for solid-state energy devices.