Na4+x[Sn1-xYxSi3.8P0.2O12]glass-ceramic electrolyte: Structure correlation with Interfacial resistance and electrochemical performance

Abstract

This investigation focuses on preparing glass and glass-ceramic Na_4+x[Sn_1-xY_xSi_3.8 P_0.2O₁₂; labeled as GC-NSY_x] electrolytes with different molar percentages (x = 0, 0.2, 0.5, 0.7, and 1.0 mol%). The preparation done using melt quenching and subsequent heat treatments designed to enhance conductivity. The Rhombohedral Na₅YSi₄O₁₂ (ICSD-20271) phase, within the space group R3̅c, emerged as the most stable and effective ion-conducting phase. In particular, the best ion conducting G-NSY_1.0 glass electrolyte (σ_b = 2.88 × 10^–5 S/cm) composition,further improved after heat treating it for 9 hours at its crystallization temperature (T_c) (GC-NSY_1.0-9h; ΔT = 156 °C; σ_b = 4.89 × 10^–4 S/cm) with superior thermal stability. Interestingly, the similarity between E_aτ and E_aσvalues indicates that both conductivity and relaxation mechanisms involve only ionic hopping. A full cell configuration using a NaMnO₂: GC-NSY_1.0-9h electrolyte with a Na–Sn alloy anode in a 7:3 ratio (GC-NSY_1.0-9h electrolyte/anode) exhibited the lowest interfacial resistance of 145 ohms and achieved a specific capacity of 97 mAhg^–1at 0.1C rate. This full cell also displayed excellent stability, irreversible capacity, and Coulombic efficiency (96 %) over 500 cycles which can be attributed to underlying oxidation and reduction reactions occurring during longer term cycling.