Sophia Brauksiepe


Sol-Gel Synthesis of Garnet-Type Tantalum Substituted Li7La3Zr2O12

Schematic Representation of a Sol-Gel Synthesis Copyright: Sophia Brauksiepe Schematic Representation of a Sol-Gel Synthesis

The use of solid electrolytes can improve the safety of lithium-ion batteries compared to currently applied liquid electrolytes regarding flammability and toxicity. Solid electrolytes can be operated at high temperatures and high voltages. However, solid electrolytes have lower lithium-ion conductivities at room temperature than liquid electrolytes.

In comparison to other lithium-ion conducting ceramics, the cubic modification of Li7La3Zr2O12 (LLZ) has a wide electrochemical window and is stable against lithium-metal. The cubic phase is stabilized by substitution of metal cations like tantalum and has a lithium-ion conductivity of 10-4 S cm-1.

An all-solid-state route of tantalum substituted LLZ (TaLLZ) requires calcination temperatures of 1150 °C. In contrast, a sol-gel synthesis is more energy-efficient because temperatures of 900 °C are sufficient. The aim of this master thesis is to analyze and optimize the parameters of the sol-gel synthesis. Crystal structure and the morphology of TaLLZ are characterized via X-ray powder diffraction and electron microscopy.

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