Naslov
Enhanced mobility of lithium and sodium ions in phosphate glasses obtained by WO3 and MoO3 addition

Autori
Renka, Sanja ; Pavić, Luka ; Tricot, Grégory ; Hostinský, Tomáš ; Kalenda, Petr ; Mošner, Petr ; Koudelka, Ladislav ; Moguš-Milanković, Andrea ; Šantić, Ana

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
23rd International Conference on Solid State Ionics (SSI-23) : Abstract Book / - , 2022, 14-14

Skup
23rd International Conference on Solid State Ionics (SSI-23)

Mjesto i datum
Boston (MA), Sjedinjene Američke Države, 17.07.2022. - 22.07.2022

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
Lithium phosphate glasses ; Sodium phosphate glasses ; Ionic conductivtiy ; Glass structure

Sažetak
Increased demand for stable and efficient electrolytes in batteries puts the focus of recent studies on the improvement of relatively low ionic conductivity in various families of oxide glasses containing alkali ions. A popular approach in achieving this goal is to add the second glass- forming oxide to the glass in order to induce structural changes which have a facilitating effect on the ionic transport. This phenomenon is well-known as the mixed glass-former effect. In this study, we show that a significant increase in ionic conductivity can be achieved by the replacement of glass-forming oxide P2O5 with WO3 and MoO3 which are not conventional glass-formers but conditional ones. For that purpose, four series of glasses 40Na2O–xMoO3–(60-x)P2O5, 40Na2O– xWO3–(60-x)P2O5, 40Li2O–xMoO3–(60-x)P2O5 and 40Li2O–xWO3–(60-x)P2O5 ; x=0-50 mol% were prepared by melt-quenching. The electrical characterization was performed by impedance spectroscopy in a wide frequency (0.01 Hz – 1 MHz) and temperature (-90 °C – 250 °C) range while the structural changes were followed by the 31P MAS-NMR and Raman spectroscopy. Comparing the phosphate glasses with different conducting ions, it was found that an increase in DC conductivity with the addition of transition metal oxides was more pronounced in lithium series, being five and four orders of magnitude for WO3 and MoO3, respectively. On the other hand, the enhancement of sodium ion conductivity was four orders of magnitude in the case of WO3 and three in the case of MoO3. Such difference is related to a smaller ionic radius and therefore higher mobility of lithium ions which can be more easily facilitated by the incorporation of tungsten and molybdenum units in the glass network. The trend in conductivity of sodium phosphate glasses was found to be non-linear, which is typical for the mixed glass former effect, exhibiting the maximal value at 30 mol% of MoO3 and 40 mol% of WO3. Similar compositional dependence was also found in the fraction of mixed molybdate/tungstate-phosphate units and the number of P-O-Mo/W linkages. These findings indicate that the fastest transport of sodium ions occurs at the maximally interconnected phosphate and molybdenum/tungsten units. On the other hand, lithium containing phosphate glasses did not show the typical effect of mixed glass formers on the electrical conductivity, even though the addition of WO3 and MoO3 produced similar network modification as in sodium containing glasses. In both series, the enhancement of ionic conductivity was found to be continuous for glasses containing up to 40 mol% of WO3 and MoO3 but retained for a higher fraction of these oxides. Here, similarly as in the sodium phosphate series, the formation of mixed molybdenum/tungsten-phosphate units strongly facilitates the transport of ions. However, at the highest amounts of WO3 and MoO3, smaller Li+ ions are less affected by the hindering nature of the glass network composed predominantly of molybdate and tungstate units, so the characteristic maximum in conductivity was not observed rather high values were retained.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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