Investigating the Interface between Ceramic Particles and Polymer Matrix in Hybrid Electrolytes by Electrochemical Strain Microscopy.

Philipp M Veelken,Roland Schierholz,Hermann Tempel,Maike Wirtz,Hans Kungl,Florian Hausen,Rüdiger-A Eichel

doi:10.3390/nano12040654

Abstract

The interface between ceramic particles and a polymer matrix in a hybrid electrolyte is studied with high spatial resolution by means of Electrochemical Strain Microscopy (ESM), an Atomic Force Microscope (AFM)-based technique. The electrolyte consists of polyethylene oxide with lithium bis(trifluoromethanesulfonyl)imide (PEO6–LiTFSI) and Li6.5La3Zr1.5Ta0.5O12 (LLZO:Ta). The individual components are differentiated by their respective contact resonance, ESM amplitude and friction signals. The ESM signal shows increased amplitudes and higher contact resonance frequencies on the ceramic particles, while lower amplitudes and lower contact resonance frequencies are present on the bulk polymer phase. The amplitude distribution of the hybrid electrolyte shows a broader distribution in comparison to pure PEO6–LiTFSI. In the direct vicinity of the particles, an interfacial area with enhanced amplitude signals is found. These results are an important contribution to elucidate the influence of the ceramic–polymer interaction on the conductivity of hybrid electrolytes.

Highlights

Over the last few years, the interest in all-solid-state batteries (ASSBs) has increased due to their enhanced safety and theoretical capacity compared to conventional organic, liquid electrolyte batteries [1,2,3]
For Electrochemical Strain Microscopy (ESM) experiments, it is of the utmost importance to clearly distinguish between isolated ceramic particles and the surrounding polymer matrix to identify the interfacial region between both materials
A PEO6 −LiTFSI with 50 wt.% LLZO:Ta all-solid-state hybrid electrolyte film was examined by means of Electrochemical Strain Microscopy

Summary

Introduction

Over the last few years, the interest in all-solid-state batteries (ASSBs) has increased due to their enhanced safety and theoretical capacity compared to conventional organic, liquid electrolyte batteries [1,2,3]. Ceramics and polymer/ceramic hybrid materials are under development for application in ASSBs. Polymer electrolytes allow for improved electrolyte–electrode interfaces compared to ceramic-based electrolytes due to their higher mechanical flexibility [4,5,6]. Polymer electrolytes display comparably low ionic conductivities [5,7]. Ceramic electrolytes are brittle and inherently exhibit a high rigidity. Their interface towards electrodes is hindered due to their rough surface structure. Hybrid electrolytes exhibit important advantages of multiple solid-state electrolyte types, such as superior electrode–

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