Control of thermodynamics and kinetics through anion substitution in metal borohydrides

High thermal stability of metal borohydrides is one of the bottlenecks in adopting them for practical hydrogen storage materials. For this reason, much effort has been put toward lowering their thermal stability. One of the common routes taken to achieve this aim is to mix with other borohydrides or alantes of less thermal stability hoping to make a compound or an alloy of intermediate stability. Recent studies have proposed a possibility where F$^{-}$ or Cl$^{-}$ anions could incorporate into the lattice of alanates or borohydrides replacing H$^{-}$ or BH$_{4}^{-}$ anions, thus modifying the thermal stability of these materials. We present here a combined experimental and theoretical study on the anion substitution in Ca(BH$_{4})_{2}$ and LiBH$_{4}$. Both thermodynamic and kinetic aspect will be discussed.