Conductivity, microstructure and mechanical properties of tape-cast LATP with LiF and SiO2 additives

Jürgen Peter Gross,Enkhtsetseg Dashjav,Frank Tietz,Jürgen Malzbender,Ruth Schwaiger

doi:10.1007/s10853-021-06773-6

Abstract

LATP sheets with LiF and SiO2 addition prepared by tape cast as electrolytes for solid-state batteries were characterized regarding conductivity, microstructure and mechanical properties aiming toward an optimized composition. The use of additives permitted a reduction of the sintering temperature. Rietveld analyses of the samples with additives revealed a phase mixture of NaSICON modifications crystallizing with rhombohedral and orthorhombic symmetry as a superstructure with space group Pbca. It seems that LiF acts as a sintering additive but also as a mineralizer for the superstructure of LATP. As general trend, higher LiF to SiO2 ratios led to lower porosities and higher values of elastic modulus and hardness determined by indentation testing, but the presence of the orthorhombic LATP leads to a decrease in the ionic conductivity. Micro-pillar testing was used to assess the crack growth behavior revealing weak grain boundaries.

Highlights

Batteries are considered a key technology for the transportation sector and storage of renewable energy [1]
For the samples with additives, the onset points of shrinkage decreased toward 750 °C followed by a sharp increase in shrinkage rate to reach a maximum shrinkage at around 880 °C. This corresponded to an almost 130 °C reduction in the sintering temperature compared to pure LATP
The use of LiF and SiO2 additives allowed a reduction in the sintering temperature and a reduction in the porosity

Summary

Introduction

Batteries are considered a key technology for the transportation sector and storage of renewable energy [1]. Rietveld refinement shows that the amount of the minority phase LiTiOPO4 is around 3 wt.-% in the LATP:Pure sample and increases to around 10 wt.-% in the samples with SiO2 and LiF additives.

Results

Conclusion