Investigation on LiBH₄-CaH₂ composite and its potential for thermal energy storage

The LiBH₄/CaH₂ composite are firstly studied as Concentrating Solar Power Thermal Storage Material. The LiBH₄/CaH₂ composite according to the stoichiometric ratio are synthesized by high-energy ball milling method. The kinetics, thermodynamics and cycling stability of LiBH₄/CaH₂ composite are investigated by XRD (X-ray diffraction), DSC (Differential scanning calorimeter) and TEM (Transmission electron microscope). The reaction enthalpy of LiBH₄/CaH₂ composite is almost 60 kJ/mol H₂ and equilibrium pressure is 0.482 MPa at 450 °C. The thermal storage density of LiBH₄/CaH₂ composite is 3504.6 kJ/kg. XRD results show that the main phase after dehydrogenation is LiH and CaB₆. The existence of TiCl₃ and NbF₅ can effectively enhance the cycling perfomance of LiBH₄/CaH₂ composite, with 6-7 wt% hydrogen capacity after 10 cycles. The high thermal storage density, high working temperature and low equilibrium pressure make LiBH₄/CaH₂ composite a potential thermal storage material.