On the Formation and the Structure of the First Bimetallic Borohydride Borate, LiCa3(BH4)(BO3)2

Abstract

We present the first report on the formation and the crystal structure of a bimetallic borohydride borate, LiCa3(BH4)(BO3)2. It is discovered during decomposition of LiBH4–Ca(BH4)2–carbon composite studied for hydrogen storage. A small amount of oxygen impurity in the starting material or introduced during sample preparation gives rise to the formation of [BO3]3-. Its crystal structure was solved from synchrotron powder diffraction data as space group Fd3̅m and a = 14.5911(2) Å at 387 °C. The experimental structural parameters are closely reproduced and the orientational disorder in [BH4]− is confirmed by first-principles calculations.