On the nature of the electrochemical cycling stability of non-stoichiometric LaNi5-based hydride-forming compounds Part II. In situ x-ray diffractometry

A Structural Study of the Homogeneity Domain of LaNi5

“…It is possible, however, to check the consistency of the diffraction data against structure models that involve double defects on one or both nickel sites. All of them (e.g., LaNi 2 (Ni 0.982(2) La 0.0045(4) & 0.0135(20) ) 3 , S = 1.82, R F 2 = 2.2%, constrained to the composition LaNi 4.88 , calculated density 8.24) lead to the same agreement factors as those obtained for the vacancy model while explaining both the measured composition and the experimental density.…”

“…A most important parameter is the compositional ratio B/A in as much as it controls properties such as plateau pressure and cycle life (2,3). For binary LaNi 5+x past investigations have suggested (4) that the phase extends over the compositional range À0.15rxr0.40 at a temperature of 12001C.…”

Electrochemical modeling of hydrogen storage in hydride-forming electrodes

“…The phase diagram is in the good agreement with previous results (see [8,[21][22][23][24]). The phase boundaries x˛and xč onverge smoothly towards a single phase-transition point which we denote, on the analogy of the critical temperature and critical composition [36] as the critical layer thickness. The critical layer thickness of this Pd-system where the miscibility gap has completely vanished is at about 10 nm and can, very likely, be related to clamping of the thin films onto the substrate, similarly as concluded before [24].…”

Structural, thermodynamic and electrochemical properties of over-stoichiometric La1−y(Ni1−zSnz)5+2y hydride forming compounds

“…Cobalt substitution was found to be very efficient concerning cycle life [1] but this element remains very costly and lot of efforts have been made to reduce its amount in commercial batteries. It was also shown by Notten et al [2][3][4][5] that further improvements can be achieved by adjusting the overall stoichiometry, making it possible to design electrochemically stable electrode materials without making use of any cobalt substitution. Indeed, the La-Ni phase diagram shows a domain of existence, ranging from LaNi 4.85 to LaNi 5.4 at about 1543 K [6,7].…”