In recent years, considerable research has been carried out exploring the potential of oxide glasses as cathode materials for solid-state batteries [1-3]. Among these materials, alkali-transition metal oxide (TMO)-phosphate-based glasses garnered significant interest due to their, stable frameworks, minimal volume changes, thermodynamic stability, and excellent alkali storage capacity. Furthermore, as consist of both alkali and TM ions, which can exist in various oxidation states, these systems can exhibit the mixed ionic-polaronic conduction mechanism. Such feature has proven to be highly effective in facilitating the intercalation and deintercalation of alkali ions. It is also crucial that cathode materials have high thermal stability, which can be improved by incorporating metal oxides, for instance Nb₂O₅, into their composition [4].

This talk will focus on the electrical properties of glasses from Na₂O-V₂O₅-Nb₂O₅-P₂O₅ system. By varying the concentration of V₂O₅ (10 and 25 mol%) in two series, we aim to examine how its content influences the electrical transport mechanism, permitting us to evaluate its possible polaronic contribution by utilizing Solid-state impedance spectroscopy (SS-IS). Obtained conductivity spectra are studied in detail using two model-free scaling procedures, namely Summerfield and Sidebottom scaling. The results reveal that glasses with lower V2O5 content (10 mol%) exhibit a purely ionic conduction mechanism, indicating that V₂O₅ does not contribute to electrical conductivity via a polaronic mechanism. On the other hand, for glasses with higher V₂O₅ (25 mol%) and low Nb₂O₅ (0 and 5 mol%) content, a mixed ionic-polaronic conductivity is observed with dominant polaronic contribution. Interestingly, with further increase in Nb₂O₅ above 10 mol%, there is a switch in conduction mechanism and ionic one prevails. These findings provide valuable insights into the mixed-conductive glass system and shed light on the roles of V₂O₅ and/or Nb₂O₅, showcasing the ability to fine-tune the mechanism of electrical conductivity by adjusting the content of oxide glass and its ratio. Lastly, obtained results will be compared with our recent studies of conductivity mechanism in glasses with various TMO and alkali ions [5] and pure polaronic glasses [6].