Structural, gaseous phase hydrogen storage, and electrochemical properties of a series of the Ti
50Zr
1Ni
44X5 (
X = Ni, Cr, Mn, Fe, Co, or Cu) metal hydride alloys were studied. X-ray diffraction (XRD) and scanning electron microscopy
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Structural, gaseous phase hydrogen storage, and electrochemical properties of a series of the Ti
50Zr
1Ni
44X5 (
X = Ni, Cr, Mn, Fe, Co, or Cu) metal hydride alloys were studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed the multi-phase nature of all alloys, which were composed of a stoichiometric TiNi matrix, a hyperstoichiometric TiNi minor phase, and a Ti
2Ni secondary phase. Improvement in synergetic effects between the main TiNi and secondary Ti
2Ni phases, determined by the amount of distorted lattice region in TiNi near Ti
2Ni, was accomplished by the substitution of an element with a higher work function, which consequently causes a dramatic increase in gaseous phase hydrogen storage capacity compared to the Ti
50Zr
1Ni
49 base alloy. Capacity performance is further enhanced in the electrochemical environment, especially in the cases of the Ti
50Zr
1Ni
49 base alloy and Ti
50Zr
1Ni
44Co
5 alloy. Although the TiNi-based alloys in the current study show poorer high-rate performances compared to the commonly used AB
5, AB
2, and A
2B
7 alloys, they have adequate capacity performances and also excel in terms of cost and cycle stability. Among the alloys investigated, the Ti
50Zr
1Ni
44Fe
5 alloy demonstrated the best balance among capacity (394 mAh·g
−1), high-rate performance, activation, and cycle stability and is recommended for follow-up full-cell testing and as the base composition for future formula optimization. A review of previous research works regarding the TiNi metal hydride alloys is also included.
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