An in situ neutron time-of-flight diffraction study of LaMM(NiCoAlMn)5-x battery electrode materials and their deuterides, for x=0 and x=0.2

The structural properties of two mechanically activated commercial LaNi, type battery materials and their deuterides have been investigated by means of in situ neutron powder diffraction analysis. A discussion of the hysteresis between the absorption and desorption isotherms is given. Using standard Rietveld refinement procedures, information on the variation of the deuterium site occupancy, the lattice symmetry and the cell volume are also presented. In particular, we report on the variation of line-broadening with concentration as well as on the complex time-dependent changes in the lattice parameters and the line-broadening following a step change in the deuterium pressure. We then show that these relatively novel data provide valuable information on the rather different phase transition processes observed for the two materials and offer an explanation for the superior kinetics of the AB(4.8) alloy. (C) 2002 Elsevier Science B.V. All rights reserved.