  The Lithium-Boron Reactive Hydride Composite System (Li-RHC) (2 LiH +
MgB$_{2}$ / 2 LiBH$_{4}$ + MgH$_{2}$) is a high-temperature hydrogen storage
material suitable for energy storage applications. Herein, a comprehensive
gas-solid kinetic model for hydrogenation is developed. Based on thermodynamic
measurements under absorption conditions, the system's enthalpy $\Delta$H and
entropy $\Delta$S are determined to amount to -34 $\pm$ 2 kJ $\cdot$ mol
H$_{2}^{-1}$ and -70 $\pm$ 3 J $\cdot$ K$^{-1}$ $\cdot$ mol H$_{2}^{-1}$,
respectively. Based on the thermodynamic behavior assessment, the kinetic
measurements' conditions are set in the range between 325 {\deg}C and 412
{\deg}C, as well as between 15 bar and 50 bar. The kinetic analysis shows that
the hydrogenation rate-limiting-step is related to a one-dimensional
interface-controlled reaction with a driving-force-corrected apparent
activation energy of 146 $\pm$ 3 kJ $\cdot$ mol H$_{2}^{-1}$. Applying the
kinetic model, the dependence of the reaction rate constant as a function of
pressure and temperature is calculated, allowing the design of optimized
hydrogen/energy storage vessels via finite element method (FEM) simulations.
