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In recent years, multi-phase materials capable of multi-ion transport have emerged as attractive candidates for a variety of electrochemical devices. Here, we provide experimental results for fabricating a composite electrolyte made up of a one-dimensional fast sodium-ion conductor, sodium zirconogallate, and an oxygen-ion conductor, yttria-stabilized zirconia. The composite is synthesized through a vapor phase conversion mechanism, and the kinetics of this process are discussed in detail. The samples are characterized using diffraction, electron microscopy, and electrochemical impedance spectroscopy techniques. Samples with a finer grain structure exhibit higher kinetic rates due to larger three-phase boundaries (TPBs) per unit area. The total conductivity is fitted to an Arrhenius type equation with activation energies ranging from 0.23 eV at temperatures below 550 ° C to 1.07 eV above 550 ° C . The electrochemical performance of multi-phase multi-species, mixed Na + and O 2 − conductor, is tested under both oxygen chemical potential gradient as well as sodium chemical potential gradient are discussed using the Goldman-Hodgkin-Kats (GHK) and the Nernst equation.

One and two pseudo-reference electrode proton exchange membrane fuel cell devices were fabricated using composite thin film composed of Nafion and Ag paste as the reference electrode. Three and four-electrode electrochemical studies were performed isolating different parts of the cell. Summing the scans utilizing the reference electrode(s) resulted in good agreement with the two-electrode scan across the entire cell. A DC current was passed through the cell under constant resistive load conditions. The equations necessary to determine the cell and the anode/cathode-reference impedance under constant resistive load are presented. A high frequency depressed arc present in the spectra of the entire cell had contributions from both the anode-reference and the cathode-reference scans. Reactance present in the four-electrode measurements isolating a section of the membrane further suggests that the high frequency depressed semicircle in the cell scan can, at least in part, be attributed to the membrane. The present work shows that by using embedded pseudo-reference electrodes, the polarization behavior of cathode and anode can be investigated independently and unambiguously without the need for de-convolution of spectra across the entire cell.

The formation of the metallic dendrite in the electrolyte under electrolytic mode can contribute to the failure of the battery, which may result in dramatic fires. Under electrolytic conditions often degradation occurs which manifests as electrode delamination and formation of cracks. In this work, both solid and liquid electrolytes were used to investigate the in-situ metallic dendrite growth. Sodium sulfur batteries have been widely used for energy storage. Also, sodium ion batteries operating at room temperature are under development. One of the modes of failure of these devices is the formation of metallic sodium dendrites. In this work, a two-phase material Na-β”-alumina+3YSZ has been used to investigate the sodium dendrite growth under electrolytic conditions. The mixed Na+ ion and O2- ion electrolyte was fabricated by the vapor phase process. The sample was sintered and converted with an embedded hole, which was achieved by a wax coated copper wire during the initial uniaxial pressing stage. Subsequently, a small plastic tube with 1M NaNO3 solution was put on the surface of the obtained disc. Silver wires were put into the NaNO3 solution and the embedded hole, they were connected with an amperemeter, a resistor, and a voltage generator. The disc was put under the microscope, and a voltage of 3.5V was applied. In-situ formation of sodium dendrites was observed. The current response and the voltage between the sample were recorded, and EIS was measured every 20 min. Furthermore, the silver nitrate solution was used to investigate the formation of sharp silver dendrites. Several drops of silver nitrate solution were placed onto the surface of the glass slide, and a cover glass was used for protection. Two silver wires were immerged inside of the solution. By applying the voltage, the silver dendrites shoot out from the tip of the silver wire and also grow along the silver wire. The current response and voltage between the sample were recorded. EIS was measured every 10 min to get the Nyquist plots.