Improving Na-beta”-alumina interface and grain boundary as solid-state electrolyte for large scale Room Temperature applications
Effect of particle size and liquid addition on capacity, conductivity and cyclability
L.P.M. Leclercq (TU Delft - Electrical Engineering, Mathematics and Computer Science)
M. Wagemaker – Mentor (TU Delft - RST/Storage of Electrochemical Energy)
E.L. van der Maas – Graduation committee member (TU Delft - RST/Storage of Electrochemical Energy)
Niek De Klerk – Mentor
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Abstract
The aim of my project at the Storage of Electrochemical Energy section of the TU Delft is to improve the performance and uncover the electrolytic hurdles of the widely used Na-beta”-alumina solid electrolyte within Sodium semi solid-state batteries at Room Temperature. Na-beta”-alumina could be an interesting candidate to replace volatile and flammable organic electrolytes, seeing as it is not flammable and made of abundant elements. It would be a safer, with potential for mass-production due to the abundancy and low costs of the required materials. However, to make working electrolyte pellets, high sintering temperatures are needed for a high density. The material would be a lot more interesting if it could be used without such high sintering temperatures and reasonable conductivity at room temperature. The aim of this thesis is to investigate whether the point-contact problem is solid-state electrolytes can be circumvented by varying the solid electrolyte particle size in combination with liquid addition and various potential concepts. Regarding our conclusions, we can affirm that the mechanically pressed BASE electrolyte pellet concept performs worse than the slurry electrolyte concept. This is related to the improved slurry contact, as well as the increased point contacts for the pellet in combination with a suspected lower ionic liquid coverage. We can also conclude that the electrolyte resistance is lowered with organic electrolyte or ionic liquid addition. The evidence space-charge of has yet to be demonstrated for our components, as smaller particles resulted in lower conductivity and capacitance, regardless of the various series and concepts experimented with. Finally, the Na+ diffusion was better for bigger particles for all three liquid additions.