Ionic Conductivity of K-ion Glassy Solid Electrolytes of K<sub>2</sub>S-P<sub>2</sub>S<sub>5</sub>-KOTf System
Ternary glassy electrolytes containing K<sub>2</sub>S as a glass modifier and P<sub>2</sub>S<sub>5</sub> as a network former are synthesized by introducing a new type of complex and asymmetric salt, potassium triflate (KOTf), to obtain unprecedented K<sup>+&...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2023-11-01
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| Series: | International Journal of Molecular Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1422-0067/24/23/16855 |
| Summary: | Ternary glassy electrolytes containing K<sub>2</sub>S as a glass modifier and P<sub>2</sub>S<sub>5</sub> as a network former are synthesized by introducing a new type of complex and asymmetric salt, potassium triflate (KOTf), to obtain unprecedented K<sup>+</sup> ion conductivity at ambient temperature. The glasses are synthesized using a conventional quenching technique at a low temperature. In general, alkali ionic glassy electrolytes of ternary systems, specifically for Li<sup>+</sup> and Na<sup>+</sup> ion conductivity, have been studied with the addition of halide salts or oxysalts such as M<sub>2</sub>SO<sub>4</sub>, M<sub>2</sub>SiO<sub>4</sub>, M<sub>3</sub>PO<sub>4</sub> (M = Li or Na), etc. We introduce a distinct and complex salt, potassium triflate (KOTf) with asymmetric anion, to the conventional glass modifier and former to synthesize K<sup>+</sup>-ion-conducting glassy electrolytes. Two series of glassy electrolytes with a ternary system of (0.9–x)K<sub>2</sub>S-xP<sub>2</sub>S<sub>5</sub>-0.1KOTf (x = 0.15, 0.30, 0.45, 0.60, and 0.75) and z(K<sub>2</sub>S-2P<sub>2</sub>S<sub>5</sub>)-yKOTf (y = 0.05, 0.10, 0.15, 0.20, and 0.25) on a straight line of z(K<sub>2</sub>S-2P<sub>2</sub>S<sub>5</sub>) are studied for their K<sup>+</sup> ionic conductivities by using electrochemical impedance spectroscopy (EIS). The composition 0.3K<sub>2</sub>S-0.6P<sub>2</sub>S<sub>5</sub>-0.1KOTf is found to have the highest conductivity among the studied glassy electrolytes at ambient temperature with the value of 1.06 × 10<sup>−7</sup> S cm<sup>−1</sup>, which is the highest of all pure K<sup>+</sup>-ion-conducting glasses reported to date. Since the glass transition temperatures of the glasses are near 100 °C, as demonstrated by DSC, temperature-dependent conductivities are studied within the range of 25 to 100 °C to determine the activation energies. A Raman spectroscopic study shows the variation in the structural units <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi>P</mi><mi>S</mi></mrow><mrow><mn>4</mn></mrow><mrow><mn>3</mn><mo>−</mo></mrow></msubsup><msubsup><mrow><mo>,</mo><mo> </mo><msub><mrow><mi>P</mi></mrow><mrow><mn>2</mn></mrow></msub><mi mathvariant="normal">S</mi></mrow><mrow><mn>7</mn></mrow><mrow><mn>4</mn><mo>−</mo></mrow></msubsup><mo>,</mo><mo> </mo><msubsup><mrow><mi mathvariant="normal">a</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">d</mi><mo> </mo><msub><mrow><mi>P</mi></mrow><mrow><mn>2</mn></mrow></msub><mi mathvariant="normal">S</mi></mrow><mrow><mn>6</mn></mrow><mrow><mn>4</mn><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula> of the network former for different glassy electrolytes. It seems that there is a role of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><msub><mrow><mi>P</mi></mrow><mrow><mn>2</mn></mrow></msub><mi mathvariant="normal">S</mi></mrow><mrow><mn>7</mn></mrow><mrow><mn>4</mn><mo>−</mo></mrow></msubsup><msubsup><mrow><mo> </mo><mi mathvariant="normal">a</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">d</mi><mo> </mo><msub><mrow><mi>P</mi></mrow><mrow><mn>2</mn></mrow></msub><mi mathvariant="normal">S</mi></mrow><mrow><mn>6</mn></mrow><mrow><mn>4</mn><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula> in K<sup>+</sup>-ion conductivity in the glassy electrolytes because the spectroscopic results are compatible with the composition-dependent, room-temperature conductivity trend. |
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| ISSN: | 1661-6596 1422-0067 |