Thermal Properties of Phosphate Based Solid Electrolytes for Sodium-Ion Cells

摘要

Solid electrolytes made of ion conducting glass-ceramic for sodium-ion cells are not inflammable, do not tend to decompose and offer high mechanical strengths to stop dendrite growth. The cells are much safer and are able to operate at higher temperatures if the solid electrolytes can replace the liquid electrolyte and the separator. For the simulation and design of all-solid-state batteries, the thermal properties of the used electrolytes need to be known accurately. As promising solid electrolyte for sodium-ion cells, Na3Zr2(SiO4)2PO4-Powder was synthesized by Sol-Gel-method using Sodium nitrate, Nitric acid, Ammonium dihydrogen phosphate, Tetraethyl orthosilicate and Zirconium (Ⅳ) oxynitrate hydrate as precursor materials. Subsequently, this powder material was pressed into pellets and sintered using spark plasma sintering (SPS) with a heating rate of 100 K/min up to 1000 °C with isothermal holding of 7 minutes. The pressure at sintering temperature was kept at 15 kN. The sintered pellets were investigated with a focus on thermal properties such as heat capacity and phase transitions using differential scanning calorimetry, thermogravimetric analysis and thermal conductivity using laser flash analysis. The temperature dependent ionic conductivity was measured by impedance spectroscopy. Stoichiometry of the samples was studied by ICP-OES. The relationship between the process parameters, the structure and the ionic conductivity of the prepared solid electrolyte was revealed for the suitability in Na-ion based cells. Further, the test cells will be assembled using standard electrode materials.