Defect-Mediated Conductivity Enhancements in Na3–xPn1–xWxS4 (Pn = P, Sb) Using Aliovalent Substitutions

By Till Fuchs, Sean P. Culver, Paul Till, W. Zeier. ACS Energy Letters, 2019

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<p>The sodium-ion conducting family of Na₃<i>Pn</i>S₄, with <i>Pn</i> = P, Sb, have gained interest for the use in solid-state batteries due to their high ionic conductivity. However, significant improvements to the conductivity have been hampered by the lack of aliovalent dopants that can introduce vacancies into the structure. Inspired by the need for vacancy introduction into Na₃<i>Pn</i>S₄, the solid solutions with WS₄^2- introduction are explored. The influence of the substitution with WS₄^2- for PS₄^3- and SbS₄^3-, respectively, is monitored using a combination of X-ray diffraction, Raman and impedance spectroscopy. With increasing vacancy concentration improvements resulting in a very high ionic conductivity of 13 ± 3 mS·cm^-1 for Na_2.9P_0.9W_0.1S₄ and 41 ± 8 mS·cm^-1 for Na_2.9Sb_0.9W_0.1S₄ can be observed. This work acts as a stepping-stone towards further engineering of ionic conductors using vacancy-injection via aliovalent substituents.</p>

Subfields: Materials Chemistry

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