What question did this study set out to answer?

To investigate the stability and properties of LiFeH4 and LiCoH4 as potential hydrogen storage materials using density functional theory.

March 3, 2026Open Access

Computational discovery of Li-based tetragonal LiFeH4 and LiCoH4 complex hydrides as efficient solid-state hydrogen storage materials for practical applications

Key Points

To investigate the stability and properties of LiFeH4 and LiCoH4 as potential hydrogen storage materials using density functional theory.
Performed density functional theory (DFT) calculations to assess structural stability.
Analyzed electronic band structure and charge density for bonding characteristics.
Evaluated gravimetric and volumetric hydrogen capacities relative to DOE targets.
Conducted thermodynamic and mechanical assessments to explore performance attributes.
LiFeH4 and LiCoH4 show gravimetric hydrogen capacities of 6.03 wt% and 5.77 wt%, respectively, exceeding DOE targets.
Both hydrides display low hydrogen desorption temperatures, enhancing their practicality for storage applications.
DFT results indicate metallic, non-magnetic behavior with significant ionic-covalent bonding characteristics.
Transition metal substitution (Fe/Co) is shown to effectively enhance hydrogen storage performance.

Abstract

• DFT predicts stable tetragonal LiFeH 4 and LiCoH 4 complex hydrides with favorable structural and mechanical properties. • Both materials exhibit metallic, non-magnetic behavior with mixed ionic–covalent bonding. • Gravimetric and volumetric hydrogen capacities exceed U.S. DOE 2025 targets. • Low desorption temperatures suggest favorable hydrogen release characteristics. • Fe/Co substitution effectively tunes hydrogen storage and thermomechanical performance. The development of efficient, safe, and high-capacity solid-state hydrogen storage materials remains a major challenge for the realization of a sustainable hydrogen-based energy economy. This work reports a comprehensive first-principles DFT investigation of previously unexplored Li-based tetragonal complex hydrides, LiFeH 4 and LiCoH 4 , aimed at assessing their stability and multifunctional properties relevant to next-generation hydrogen storage technologies. Structural optimization and energetic analyses confirm the dynamical and mechanical stability of both hydrides. Electronic band structure and density of states calculations reveal a metallic character with finite electronic states at the Fermi level and non-magnetic ground states. Detailed charge density analysis indicates mixed ionic–covalent bonding, with strong metal–hydrogen interactions playing a key role in lattice stabilization. LiFeH 4 exhibits a high gravimetric hydrogen storage capacity of 6.03 wt% and a volumetric density of 194.91 kg/m 3 , while LiCoH 4 delivers 5.77 wt% and 186.77 kg/m 3 , respectively, both exceeding the U.S. Department of Energy 2025 targets. Notably, the hydrides show low hydrogen desorption temperatures, with LiCoH 4 desorbing at 203 K and LiFeH 4 at 285 K, indicating favorable hydrogen release behavior. Thermodynamic analysis, including zero-point energy corrections (0.9692 eV for LiFeH 4 and 0.8771 eV for LiCoH 4 ), Debye temperature, free energy, entropy, and heat capacity, further supports their stability over a wide temperature range. Mechanical and thermal assessments reveal higher hardness (19.27 GPa) and lattice thermal conductivity at 300 K (40.83 Wm −1 K −1 ) for anisotropic LiFeH 4 , whereas anisotropic LiCoH 4 exhibits improved ductility and lower thermal conductivity (17.74 Wm −1 K −1 ). These results demonstrate that LiFeH 4 and LiCoH 4 possess complementary hydrogen storage characteristics and highlights transition-metal substitution as an effective strategy for tuning material performance, providing valuable guidance for future experimental synthesis and practical application of Li-based complex hydrides.

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