Exploring the Effect of V₂O₅ and Nb₂O₅ Content on the Structural, Thermal, and Electrical Characteristics of Sodium Phosphate Glasses and Glass-Ceramics.

ABSTRACT: Na-V-P-Nb-based materials have gained substantial recognition as cathode materials in high-rate sodium-ion batteries due to their unique properties and compositions, comprising both alkali and transition metal ions, which allow them to exhibit a mixed ionic-polaronic conduction mechanism. In this study, the impact of introducing two transition metal oxides, V₂O₅ and Nb₂O₅, on the thermal, (micro)structural, and electrical properties of the 35Na₂O-25V₂O₅-(40 - x)P₂O₅ - xNb₂O₅ system is examined. The starting glass shows the highest values of DC conductivity, σ_DC, reaching 1.45 × 10^-8 Ω^-1 cm^-1 at 303 K, along with a glass transition temperature, T_g, of 371 °C. The incorporation of Nb₂O₅ influences both σ_DC and T_g, resulting in non-linear trends, with the lowest values observed for the glass with x = 20 mol%. Electron paramagnetic resonance measurements and vibrational spectroscopy results suggest that the observed non-monotonic trend in σ_DC arises from a diminishing contribution of polaronic conductivity due to the decrease in the relative number of V⁴⁺ ions and the introduction of Nb₂O₅, which disrupts the predominantly mixed vanadate-phosphate network within the starting glasses, consequently impeding polaronic transport. The mechanism of electrical transport is investigated using the model-free Summerfield scaling procedure, revealing the presence of mixed ionic-polaronic conductivity in glasses where x < 10 mol%, whereas for x ≥ 10 mol%, the ionic conductivity mechanism becomes prominent. To assess the impact of the V₂O₅ content on the electrical transport mechanism, a comparative analysis of two analogue series with varying V₂O₅ content (10 and 25 mol%) is conducted to evaluate the extent of its polaronic contribution.

SUBMITTER: Marijan S 

PROVIDER: S-EPMC10932346 | biostudies-literature | 2024 Mar

REPOSITORIES: biostudies-literature