The effect of divalent metal-dopants, Mg, Ca, and Zn, on the stability of LiBH4 is studied by using the first-principles calculations and CALPHAD (CALculation of PHAse Diagram) modeling. The ground states of Mg 1/2BH4, Ca1/2BH4, and Zn 1/2BH4 are shown to be I4m2, F2dd, and I4m2, respectively, through first-principles calculations. Positive enthalpy of mixing between Li and the alloying element is predicted, indicating unfavorable solubility of alloying elements in LiBH4 and thus offering possibility to decrease the stability of LiBH4. The ionic sublattice model of (Li +, M2+, Va)1(BH4-) 1 is adopted for the metal substituted LiBH4 phase. It is observed that the addition of Mg or Zn has limited effect as the decomposition temperature is between those of LiBH4 and M1/2BH 4 for Mg and Zn substitutions. LiBH4 is destabilized with magnesium borides or LiZn4 formation but its decomposition temperature is higher than that of M1/2BH4. On the other hand, the addition of Ca significantly reduces the H2 releasing temperature due to the formation of highly stable CaB6.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Fuel Technology
- Condensed Matter Physics
- Energy Engineering and Power Technology