Extrusion processing of PEO/LATP composite electrolytes for solid-state batteries

Lithium metal has been seen for long as the key to develop next generation of high energy batteries but suffers from the formation of lithium dendrites during cycling which is hardly hindered by liquid electrolytes. Polymer electrolytes based on poly (ethylene oxide) doped by lithium salts provide good interfaces but suffer from poor ionic conductivity at room temperature and lack of mechanical properties above the melting temperature. Composite electrolytes are considered as a possible way to overcome these issues. This study experimented melt-extrusion without added solvent as a way to elaborate such an electrolyte using a model NaSICON type Li1.3Al0.3Ti1.7(PO4)3 lithium-ion conductive filler, dispersed in a doped polymer matrix. Morphological, physical and resulting electrochemical properties of various compositions were investigated. 55 vol% of filler was shown to be the maximum that can be incorporated due to excessive viscosity and jamming. Below this limit, the extruded electrolytes display homogeneously dispersed particles and reduced tuneable porosity that enable to get soft elastic membranes at room temperature. Limitation of the ionic conductivity was observed and attributed to tortuosity and transport resistance at interfaces.