The use of solid-state electrolytes represents a promising technology for the next generation of Li-ion batteries, offering improved safety, stability and energy density. Research in this field focuses on the development of materials that provide high ionic conductivity and stability across a wide temperature and potential range. In this master thesis we have analysed polymer electrolytes based on PEO-LiTFSI, composite electrolytes based on PEO-LiTFSI and Ta-LLZO and ceramic electrolytes based on Ta-LLZO ceramics. Based on LSV measurements, we found that composite electrolytes based on PEO-LiTFSI and Ta-LLZO demonstrate improved voltage stability (5.5 V vs. Li/ Li$^+$), which enables the integration of composite electrolytes with high-voltage cathode materials. Measurements of ionic conductivity using EIS revealed lower ionic conductivities of the composite electrolytes compared to the polymer PEO-LiTFSI electrolyte (3×10$^{-4}$ S cm$^{-1}$ and 2×10$^{-3}$ S cm$^{-1}$). Polymer and composite electrolytes were analyzed in configurations with LFP and LTO using galvanostatic measurements, and we found that composite electrolytes provide more stable performance than the polymer electrolyte. Furthermore, as part of the thesis, we fabricated a ceramic electrolyte and optimised the composition for the tape casting and sintering process. The resulting ceramic membrane was analysed with XRD and SEM.
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