Exploring solid-state batteries on the nanoscale by utilizing electrochemical strain microscopy

  • Lokal hoch aufgelöste Untersuchung der elektrochemischen Eigenschaften von Materialien für Festkörperbatterien mittels "electrochemical strain microscopy"

Schön-Blume, Nino; Hausen, Florian (Thesis advisor); Mayer, Joachim (Thesis advisor)

Aachen : RWTH Aachen University (2021, 2022)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2021

Abstract

Energy storage devices act as a catalyst for technological advancement and are poised to solve critical questions with regards to the energy supply and storage of the future. For target-oriented research, it is fundamental to understand the processes and mechanisms that determine the performance of electrochemical materials on a sufficiently small scale. This is especially critical, when developing advanced materials for novel technologies like solid state batteries. In solid state batteries the aim is to substitute conventional liquid electrolytes with solid state electrolytes for improved safety and electrochemical properties. In this work, electrochemical strain microscopy was used to probe solid-state battery materials and gain insights into the local properties on an unprecedented scale. Electrochemical strain microscopy (ESM) is a novel technique based on atomic force microscopy (AFM), that so far has not been extensively used on solid state batteries. Subsequently, the underlying signal formation mechanisms were extensively probed and determined to be based on electrostatic interaction between AFM-tip and sample rather than deformation based on Vegard’s Law. It is found that the AC bias induced cantilever reflection also called ESM amplitude, shows distinctive local variations that are linked to the lithium-ion concentration and phase composition. Additionally, it is demonstrated on the solidstate electrolyte Li1.3Al0.3Ti1.7(PO4)3 (LATP), that the grain boundary composition is not homogeneous, is influenced by the sintering temperature and strongly impacts global ion conductivity. Furthermore, it is found that additional interfaces are formed by twinning occurring inside the LATP grains influencing ion migration through the material. This work shows that electrochemical strain microscopy allows enhanced characterization of the origins of electrochemical performance on a relevant scale and is a suitable tool for advanced research of solid-state battery materials.

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