TY  - THES
T1  - Thermodynamic and kinetic instability of inorganic solid electrolytes at lithium and sodium metal electrodes
A1  - Wenzel,Sebastian
Y1  - 2016/11/18
N2  - In this thesis the question will be discussed and evaluated, whether the application of solid electrolytes will enable the use of alkali metal electrodes in all-solid-state batteries. Different lithium or sodium ion conducting materials were synthesized, bought or delivered by corporation partners. Using these materials, the stability in contact with the respective alkali metals was investigated by a combined approach, using common electrochemical analysis methods like impedance spectroscopy and a during this project developed in situ photoelectron spectroscopy technique. The results led to a classification of stable, mixed conducting and solid electrolyte interphases. Interphases of promising materials like the garnet type Li7La3Zr2O12, Na-beta”-alumina (stable), Li0.35La0.55TiO3 (MCI), Li7P3S11 and Li10GeP2S12 (SEI) were studied. The SEI formation process was found to show a parabolic behavior and was thus treated like a classical solid state reaction, leading to a long time assessment of the interphase behavior and growth. Thus, insight into interphase formation and the instability of solid electrolytes were gained.
In the second part, the interface between sodium metal electrodes and the solid electrolyte beta”-alumina was investigated under current load, resulting in a strongly increasing voltage for current densities in the range of a few mA/cm2 due to contact loss (caused by metal dissolution). Thus, the pressure dependence of galvanostatic experiments was investigated.
As a result the proper cycling of large amounts of alkali metal and the complete dissolution of a macroscopic metal electrode was realized. Transferring the same techniques and experiments to SEI forming materials led either to short circuits (for Li7P3S11) or an electrochemical enhanced interphase growth (e. g. for Li10GeP2S12). At the end, the results will be discussed in the context of the initially raised question.
CY  - Gießen
PB  - Universitätsbibliothek
AD  - Otto-Behaghel-Str. 8, 35394 Gießen
UR  - http://geb.uni-giessen.de/geb/volltexte/2016/12147
ER  -