Optimizing LiNiZnO single component fuel cell performance by changing pellet composition

Abstract

Fuel cells are electrochemical devices that convert hydrogen and oxygen into electricity and water. They enable sustainable energy production and are a topic of immense research. Single component fuel cells are an emerging type of fuel cells that have many advantages over traditional three-layered cells but their working mechanisms are not yet fully understood. Single component fuel cells are easy to manufacture. Furthermore, they are expected to have better thermal stability than conventional three-layered cells, which might suffer from a mismatch in the thermal coefficients between the different layers, which results in cracking during high temperature operation.

This work focuses on screening different ionic conductor – semiconductor compositions for single component fuel cells to optimize the cell performance. LiNiZn-oxide– Gd doped Ce2O (LNZ-GDC) cells are fabricated in different compositions ranging from pure LNZ to pure GDC in 20% increments. X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS) and current-voltage (IV) measurement techniques are used for characterizing the cell crystal structure, impedance behavior and performance. In addition, the optimal cell composition, which yields the highest power density, is studied for temperature and gas atmosphere effects as well as cell porosity effects.

The most commonly used composition of 40wt% LNZ, 60wt% GDC is proven to be the most efficient, yielding a power density of 30 mW/cm2at 550◦C. Increasing operating temperature reduces cell resistance and increases ionic conduction. Gas atmosphere is observed to have several complicated effects on the cell performance. Recommendations for standardized stabilization times and active area requirements are given. In the future, single component fuel cells should be systematically studied for long-term stability to identify the degradation mechanisms in the cells, since only a stable and high performance cell can be commercialized.