Pressure Induced Changes in Grain Boundary Conditions of Lithium Conducting Ceramics Characterized by Impedance Spectroscopy

Abstract

Solid state batteries, particularly for lithium ion based architecture have been the focus of development for over 20 years and are receiving even more attention today. Utilizing impedance spectroscopy (IS) measurements we investigate the response of conductivity versus incremental pressure increase by a piston-cylinder-type high pressure cell up to 1 GPa for some lithium conducting ceramics: LATP (Li1.3Al0.3Ti1.7(PO4)3), LLTO (Li5La3Ta2O12), LLT (Li0.33La0.55TiO3), LAGP (Li1.5Al0.5Ge1.5P3O12) and LLZO (Li7La3Zr2O12) for non-annealed and annealed samples.Isothermal, incremental pressure increase of powders allows for an in situ observation of the transition state conditions of poorly consolidated ceramic powders and the effects on grain boundary conditions prior to sintering. Specific conductance (σb) increased by several orders of magnitude in some samples, approaching 10-3 S∙cm-1, yet decreased in other samples. The affect of grain boundaries and affects of bulk capacitance as the sample dimensions are altered due to pressure, are attributed to some of this behavior and will be discussed. The understanding of some of these fundamental processes may be valuable in facilitating these and similar ceramics for use in commercial solid state battery systems.