Li+ ionic conduction properties on NaI doped with a small amount of LiBH4
In the present work, Li+ conductor is synthesized via small doping of LiBH4 into “Li-free” compound (or solid solvent), NaI. The formation of solid solution between NaI and LiBH4 is confirmed by XRD measurement, and the solubility limit of LiBH4 exists between 6 to 13 mol%. The value of σ for 15NaI·LiBH4 (6 mol% LiBH4) showed 1.7 × 10−6 S/cm at room temperature, which is comparable to that for LiI. From the plot of log σT vs. 1000/T, an activation energy for Li+ conduction in NaI is estimated to be 0.68 and 0.32 eV for heating and cooling cycle, respectively. The results of AC impedance measurement and DC polarization test indicate that Li+ plays a major role in ionic conduction in NaI regardless of the slight molar fraction of Li+. The present results suggest that the expansion in the material choice for solid solvent and other alkali halides can also work as a base material for Li+ ion conductors.
KeywordsSolid electrolyte Lithium-ion conductor Li-free compounds All-solid-state battery Solid solution Electrical conductivity LiBH4
This research was partially supported by the Ministry of Education, Culture, Sports, Science and Technology, through a Grant-in-Aid for Scientific Research (C), 2015, No. 15K06463.
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