Interface Properties of LLZO/PEO Hybrid Electrolytes

Composite or hybrid organic-inorganic electrolytes have attracted significant interest as promising candidates for next-generation solid-state batteries. By combining the advantages of polymers and ceramics, these electrolytes provide enhanced mechanical properties and effectively address the contact issues typically encountered in fully ceramic solid-state batteries.<br/>In hybrid electrolytes, it was initially assumed that the ion conductivities of the individual ceramic and polymer components were the primary factors influencing overall conductivity. However, it has been found that modifications in the polymer material near ceramic particles and the transition area between the polymer and ceramic components within the hybrid structure play the significant role.<br/>We conducted a systematic investigation of ceramic-polymer electrolytes to thoroughly explore the properties of the interface layer and the overall conductivity of the hybrid electrolyte as influenced by the parameters of this interface layer, specifically ionic conductivity and layer thickness. This analysis included examining various particle size distributions enabling the comparison and agreement with experimental data.<br/>Moreover, the interfacial resistance between the filler and polymer matrix is crucial in determining the overall conductivity of solid-state batteries. High resistance values at this interface, exceeding 100 Ω.cm², can impede ion transport and potentially negate the contribution of filler content to ionic conductivity, so this value was considered in our calculations.<br/>Our investigation has shown a strong correlation between the ionic conductivity values predicted by our model and those obtained from experimental results. This alignment is particularly evident at specific conductivities and thicknesses of the LLZO/PEO interface. Notably, the ionic conductivity values of the interface layer are approximately ten times greater than the one of the bulk polymers, and the thickness of this layer is 10% of the uncoiled chain length of PEO. Under these conditions, the maximum conductivity matches the same content percentage of the filler material as indicated by experimental ionic conductivity measurements.