Oxide-ceramic electrolyte layers for all-solid-state lithium batteries

In the past decade, electricity generated from renewable energy sources, as well as electro mobility have gained much importance in our society. With this readiness to change the current system, an increase of requirements for electric grid and safety aspects of energy storage systems appear. All-solid-state lithium batteries (ASB) have better safety properties due to the non-flammable solid electrolyte than common lithium ion batteries (LIB), which use flammable organic liquid as electrolyte. Additionally, a higher energy density is possible because of their compatibility with using high voltage cathode materials. Oxide-ceramic lithium ion conductors such as Li7La3Zr2O12 (LLZ) [1] have the advantage of inertness in oxygen atmosphere, which simplifies their handling during the material processing. LLZ’s stability when contacting lithium metal and its wide electrochemical window (usable up to 8V vs. Li/Li+) would provide higher energy densities than LIB. In combination with its good total ion conductivity of about 10-4 S cm-1 at room temperature [2], it is one of the most promising candidates for all-solid-state battery application. LLZ was synthesized and by substitution of Al [2], Ta [3] and Y [4] into the LLZ structure, the structural stability and its total ion conductivity were improved. Ta substituted LLZ indicated a highest total ion conductivity of about 10-3 S cm-1 and almost no dependence on its lithium concentration. After investigation of bulk electrolyte materials, an ASB prototype cell using bulk LLZ as solid electrolyte was fabricated at IEK-1 and proved to run a LED. To bridge lab works and real applications, large size LLZ functional layers need to be fabricated by different established technologies. Therefore, the investigated LLZ has been processed by tape casting and was used for sintering studies, in order to obtain highly dense solid electrolyte layers and also mixed electrode films for prospective all-solid-state lithium battery application.References:[1] Murugan et al., Angew. Chem. Int. Ed. 46 (2007) 7778.[2] Hubaud et al., J. Mater. Chem. A. 1 (2013) 8813. [3] Buschmann et al., Phys. Chem. Chem. Phys. 13 (2011) 19378.[4] Murugan et. al., Electrochem. Commun. 13 (2011) 1373