Genki Kobayashi and Ryoji Kanno at Tokyo Institute of Technology with colleagues from the Institute for Molecular Science, Japan Science and Technology Agency, Tokyo Institute of Technology, Kyoto University and High Energy Accelerator Research Organization (KEK) in Japan have postulated that hydride ions (H-) may be useful for high-energy-density storage devices. Using an oxyhydride solid state cell the researchers have demonstrated pure H- conduction in an oxide for the first time.
Metal hydrides tend to have an inflexible lattice, which makes H– transport difficult which is why the researchers turned to oxyhydrides where oxygen and hydrogen share the same lattice sites. Another challenge is the high electron-donating properties of H-, which means that the electrons will dissociate from the H- to produce protons and electrons, giving rise to electron rather than hydride-ion transport. As a result the research team sought a system containing cations that were more electron-donating than the H-.
Crystal structure of La2-x-ySrx+yLiH1-x+yO3-y (x = 0, y = 0, 1, 2)
The researchers, who examined how the structure of their oxyhydride compounds changed with composition and synthesis conditions, also studied characteristics of the electronic structure that suggested an ionic Li-H bond in the compound, namely the existence of H– in the oxides.