Characteristics of a Li₃BS₃ Thioborate Glass Electrolyte Obtained via a Mechanochemical Process

Abstract

To improve the ionic conductivity of solid electrolytes, it is generally thought that anions with high polarizability should be used. However, the relationship between polarization and conductivity is not clear because conductivity largely depends on the crystal structure. In this study, we focus on amorphous materials with no long-range ordered structure. The conductivity and ductility properties of lithium boron oxide (Li3BO3), lithium boron nitride (Li3BN2), and lithium boron sulfide (Li3BS3) are compared. Li3BS3 glass is prepared from Li2S, B, and S using heat treatment and a mechanochemical process. It has high ductility and a higher ionic conductivity (3.6 × 10–4 S cm–1 at 25 °C) than that of Li3BO3 and Li3BN2 glass with a low activation energy of 32 kJ mol–1. Li3BS3 glass is therefore suitable as an ionic conductor with high conductivity. The electronegativity of anions and glass properties such as ionic conductivity and ductility are correlated, and it is proposed that this relationship can be used as a basis for investigating fast ionic conductors.

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“…4d). Kimura et al demonstrated that extended ball milling of Li 3 BS 3 causes amorphization and improves ionic conductivity, likely due to introduction of defects 60,67 . Extended ball milling is attempted on the 5%-substituted Li 3 BS 3 to assess whether both defect engineering strategies are compatible.…”

“…The 11 B NMR measurements are shown in Figure 4g. The 11 B NMR for Li 3 BS 3 and Li 2.95 B 0.95 Si 0.05 S 3 show a single, quadrupolar environment that can be assigned to the [BS 3 ] 3-moieties67,72 . The signal from the a-Li 2.95 B 0.95 Si 0.05 S 3 shows a similar signal to that of the crystalline phases but the shape changes, similarly to the previous measurement for amorphous Li 3 BS 367 .…”

“…The 11 B NMR for Li 3 BS 3 and Li 2.95 B 0.95 Si 0.05 S 3 show a single, quadrupolar environment that can be assigned to the [BS 3 ] 3-moieties67,72 . The signal from the a-Li 2.95 B 0.95 Si 0.05 S 3 shows a similar signal to that of the crystalline phases but the shape changes, similarly to the previous measurement for amorphous Li 3 BS 367 . Li 3 BS 3 , Li 2.95 B 0.95 Si 0.05 S 3 , and a-Li 2.95 B 0.95 Si 0.05 S 3 all exhibit a major peak at ~60 ppm and a relatively minor peak ~0 ppm.…”