Efficient energy storage is crucial for a widespread use of energy from renewable sources such as wind and solar. Lithium and sodium based complex metal hydrides such as LiBH4 and NaBH4 are very promising materials for energy storage. Due to their high hydrogen content and high ionic conductivity, they are attractive for reversible hydrogen storage in fuel-cell vehicles, and as electrolytes or electrodes for new generation high energy density batteries. They are however, limited by unfavorable thermodynamic and slow kinetics, which results in hydrogen release above 400 °C and poor reversibility. In addition, they only exhibit sufficient ionic conductivity above 110 °C, which is too high for battery applications. I will show that nanoconfinement is an effective method to overcome these limitations. Confinement of LiBH4 and NaBH4 in carbon nanoscaffolds leads to a remarkable decrease in hydrogen release temperatures as well as faster hydrogen release and uptake kinetics [1-4]. Nanoconfinement of LiBH4 in mesoporous silica leads to more than three order of magnitude increase in its room-temperature Li-ion conductivity, combined with good electrochemical stability [5-6]. This makes LiBH4/silica nanocomposites a suitable electrolyte for all-solid-state battery. I will discuss the origin of these confinement effects and the impacts of the scaffolds on the performance of nanoconfined complex hydrides in energy storage applications.
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