The Stability and Reversibility of TiCl3 Doped LiBH4
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1042-S05-05
The Stability and Reversibility of TiCl3 Doped LiBH4 Ming Au1, Arthur R Jurgensen1, William A Spenser1, Donald L Anton1, and Frederick E Pinkerton2 1 Savannah River National Laboratory, Aiken, SC, 29808 2 General Motor, Warren, MI, 48088 Abstract In an effort to develop reversible metal borohydrides with high hydrogen storage capacities and low dehydriding temperature, doping LiBH4 with TiCl3 was conducted. The TiCl3 effectively reduced the dehydriding temperature through a cation exchange interaction. The material LiBH4 + 0.1TiF3 desorbed 3.5wt% and 8.5wt% hydrogen at 150oC and 450oC respectively. Subsequent re-absorption of 6wt% hydrogen at 500oC and 70 bars was observed. The XRD analysis of the rehydrided samples confirmed the reformation of LiBH4. However, adding more TiCl3 made lithium borohydrides more volatile and irreversible. TGA-RGA measured diborane evolution during dehydrogenation that results in unrecoverable capacity loss and irreversibility. Although TiCl3 doping reduced the stability of LiBH4, it makes materials irreversible. Key words:
Borohydride, Hydrogen storage, Reversibility, Stability, Rehydrogenation
1. INTRODUCTION Lithium borohydride, LiBH4, has both high gravimetric (18.4 wt%) and volumetric (121 kg/m3) hydrogen contents making it an ideal candidate as a hydrogen storage material. The release of hydrogen from LiBH4 requires temperatures in excess of 400oC and rehydrogenation requires both high temperatures (>650oC) and pressure (>190 bar) [1]. Great interest has been generated in developing borohydride materials for reversible hydrogen storage. A number of recent papers have reported reduction of dehydrogenation temperatures (destabilization) by mixing LiBH4 with additives. Zuttel mixed LiBH4 with 75wt% of SiO2 and reduced the dehydriding temperature from 400oC to 200oC. He reported that the mixed material was partially reversible, but gave no data [2]. Orimo added Mg into the LiBH4 through ball milling and reduced the dehydriding temperature from 577oC to 547oC with no rehydrogenation data reported [3]. Pinkerton reported that ball milled the mixture of 2LiNH2 + LiBH4 desorbed 10.2wt% hydrogen from 250oC to 364oC. Unfortunately, the dehydrided material was not able to absorb hydrogen at 8MPa [4]. Vajo reported that the ball milled mixture of LiBH4 and LiOH desorbed 10wt% hydrogen from 50oC to 300oC, but the dehydrided mixed material was not reversible [5]. There are a few of reports providing the rehydrogenation information. Through XRD and Raman spectroscopic analysis, Orimo confirmed the reformation of LiBH4 at 350 bar and 600oC after LiBH4 decomposed at 1MPa and 600oC. Unfortunately, the quantitative data of rehydrogenation was not available [6]. Vajo reported that the ball milled mixture LiH+0.5 MgB2 + 0.03 TiCl3 absorbed 9 wt% hydrogen at 350oC and 100 bar and desorbed 8wt% hydrogen at 450oC [7]. In author’s previous work, the material LiBH475% + TiO225% desorbed 9 wt% hydrogen from 100oC to 600oC and absorbed 8
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