| Fast Ionic Conduction in Complex Hydrides Complex hydrides has been attracting great interest because of its various energy-related functions such as microwave absorption and lithium fast-ionic conduction as well as hydrogen storage. By microwave irradiation, LiBH4 consisting of Li+ and [BH4]− complex anions, which is one of representative complex hydrides, is heated rapidly above 380 K due to a large conductive loss, at which almost all hydrogen is desorbed [1]. As a result of clarifying the mechanism of the microwave absorption, we discovered lithium fast-ionic conduction in LiBH4 accompanied by the structural transiton (more than 1×10−3 S/cm over 390 K), which opened up research on lithium ionic conduction in complex hydrides [2]. Then, we have worked on the design of lithium fast ionic conductors in LiBH4-based, LiNH2-based, and LiAlH4-based complex hydrides [3]. It has been recently reported that the complex hydrides can be used as electrolytes in all-solid-state lithium rechargeable batteries [4]. These findings suggest that ionic conductions of the other cation such as Na+, K+ and Mg2+ may also occur in complex hydrides because they are composed of various combinations of the above-described metal cations and complex anions. In fact, Na2(BH4)(NH2) obtained in the NaBH4–NaNH2 system exhibits the sodium fast ionic conductivity of 2×10−6 S/cm at RT because of the specific antiperovskite-type structure with vacancies on the Na+ site [5]. Just recently, Na2B10H10 and Na2B12H12 were found to exhibit high ionic conductivity on the order of 0.1 S/cm above its order-disorder phase-transition at about 360 K and 530 K, respectively [6, 7]. References - M. Matsuo et al., Appl.Phys. Lett., 90 (2007) 232907.
- M. Matsuo et al., Appl.Phys. Lett., 91 (2007) 224103.
- M. Matsuo and S. Orimo, Adv. Energy Mater., 1 (2011) 161.
- A. Unemoto et al., Adv. Func. Mater., 24 (2014) 2267.
- M. Matsuo et al., Appl.Phys. Lett., 100 (2012) 203904.
- T.J. Udovic et al., Chem. Comm., 50 (2014) 3750.
- T.J. Udovic et al., Adv. Mater., in press.
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