Boron Hydrogen Compounds: Hydrogen Storage and Battery Applications.

About 25 years ago, Bogdanovic and Schwickardi (B. Bogdanovic, M. Schwickardi: 1-9, 253 (1997) discovered the catalyzed release of hydrogen from NaAlH. This discovery stimulated a vast research effort on light hydrides as hydrogen storage materials, in particular boron hydrogen compounds. Mg(BH), with a hydrogen content of 14.9 wt %, has been extensively studied, and recent results shed new light on intermediate species formed during dehydrogenation. The chemistry of BH, which is an important intermediate between BH and BH, is presented in detail. The discovery of high ionic conductivity in the high-temperature phases of LiBH and NaBH opened a new research direction. The high chemical and electrochemical stability of -hydroborates has stimulated new research for their applications in batteries. Very recently, an all-solid-state 4 V Na battery prototype using a Na(CBH)(BH) solid electrolyte has been demonstrated. In this review, we present the current knowledge of possible reaction pathways involved in the successive hydrogen release reactions from BH to BH, and a discussion of relevant necessary properties for high-ionic-conduction materials.