Role of Sodium-Ion Dynamics and Characteristic Length Scales in Ion Conductivity in Aluminophosphate Glasses Containing Na₂SO₄

Abstract

Achieving high ion conductivity in glass-based Na-ion conducting materials for their applications as solid electrolytes in batteries is still challenging owing to the vague knowledge on the factors governing Na-ion dynamics. In the present study, an attempt has been made to identify the factors affecting the sodium-ion dynamics through structure and conductivity property correlation for the 37.5Na2O–37.5P2O5–15Al2O3–10NaF (FS-0; mol %) glass system with varied concentrations of Na2SO4. 31P, 27Al, and 23Na MAS NMR (magic-angle spinning nuclear magnetic resonance) and Raman spectroscopy are employed to assess the structural modifications, and impedance spectroscopy is used to measure the variations in ionic conductivity on the addition of Na2SO4 in the FS-0 glass. Raman spectra and MAS NMR analysis indicate that the quantity of P–O–Na bonds and sulfate (SO4 2–) units surrounded by sodium increase with increasing Na2SO4 concentration. Impedance analysis reveals that the conductivity of FS-0 glass enhances by 1 order with the addition of 6 mol % Na2SO4. We identify from the ac-conductivity spectral analysis that the concentration of charge carriers and the critical hopping length of mobile cations increase with the addition of 6 mol % Na2SO4. Overall, we reveal that the structural modifications, Na-ion concentration, and the shallower potential well that is created for sodium due to its interaction with the nearest neighboring cations affect the Na-ion dynamics. The information obtained from the present study certainly helps to optimize the chemical composition of glasses demonstrating high ionic conductivity.

Machine Learning-Assisted Design of Na-Ion-Conducting Glasses

“…This clearly indicates that Na 2 SO 4 has a positive impact on conductivity for concentration >5 mol %. Several studies in the literature have reported that the addition of Na 2 SO 4 in phosphate glasses enhances the conductivity value. ,− Na 2 SO 4 decomposed in a glass structure and formed isolated SO 4 2– anions and Na + cations. Additionally, these large SO 4 2– anions accumulated in the channel regions surrounded by Na + cations.…”

“…However, it is also important to note that conductivity depends on both the concentration and mobility of sodium ions, as expressed by the formula σ = nc μ (where σ is the conductivity, n is the sodium-ion concentration, μ is the mobility of the sodium ion, and c is the charge of the Na ion). Furthermore, several studies show that in glass samples, the structure plays a significant role in governing the conductivity of Na-ions and not their concentration alone. ,, A similar study on Na 3 Al 2 P 3 O 12 glasses where the concentration of NaF was increasing with decreasing Al 2 O 3 content showed that conductivity follows a non-monotonic pattern with Na-ion concentrationit increases up to a particular concentration of NaF (<10 mol %), following which it decreases . Accordingly, it is nontrivial to conclude that the change in conductivity is only due to the concentration of sodium ions.…”

“…The conductivity of a material depends mainly on the charge carrier concentration and the mobility of cations. In general, electrolytes are divided into strong or weak depending on whether the conductivity is governed by ion mobility or concentration of charge carriers. , Studies claim that doping sodium halide components enhances Na-ion conductivity in glasses. ,− Structural modification can also improve the conductivity of glass materials by enhancing the mobility of cations. ,− Thus, ionic conductivity in glass materials can be improved by optimizing the Na-ion concentration or modifying the glass’s network structure. Due to the poor understanding of the composition–structure–ionic conductivity relationships in glasses, a trial-and-error method is widely adopted for developing promising Na-ion electrolyte candidates.…”

Amorphous Materials for Lithium‐Ion and Post‐Lithium‐Ion Batteries

“…Increasing the fraction of bridging oxygens can enhance the ionic conductivity from 3.7 × 10 −8 to 3.3 × 10 −7 S cm −1 at 100 °C. [ 113 ] Other tested glassy electrolytes for SIBs are Na 2 S‐P 2 S 5 , [ 114 ] Na 3 BS 3 , [ 115 ] Na 2 O‐P 2 O 5 ‐Al 2 O 3 ‐NaF‐Na 2 SO 4 , [ 116 ] Na 3 Al 2 P 3 O 12 ‐NaF, [ 117 ] sodium borophosphate, [ 118 ] sodium borosilicate, [ 119 ] NaCl‐Ga 2 S 3 ‐GeS 2 , [ 120 ] Na 3 PS 4 ‐Na 4 GeS 4 , [ 121 ] Na 2 O‐B 2 O 3 ‐SiO 2 ‐H 2 O, [ 122 ] etc. Further development of glass electrolytes with both high ionic conductivity and good machinability is required in the future.…”

Multi‐Functional Applications of H‐Glass Embedded with Stable Plasmonic Gold Nanoislands

“…Glass materials, known for their environmental friendliness, have been incorporated into a wide range of applications across the biological, optical, photonic, and energy sectors. [23][24][25][26][27] This versatility stems from their flexible thermal, optical, mechanical, and electrical properties, which can be precisely adjusted by altering their chemical composition. Glass substrates offer a number of benefits, including a smooth, transparent surface, simple handling, robustness, cost-effective, and chemical inertness.…”