SITE OCCUPANCIES IN THE BATTERY ELECTRODE MATERIAL LANI3.55MN0.4AL0.3CO0.75 AS DETERMINED BY MULTIWAVELENGTH SYNCHROTRON POWDER DIFFRACTION

The battery electrode material LaNi3.55Mn0.4Al0.3Co0.75 is a substitut ional derivative of LaNi5 in which La occupies site 1(a), and Ni, Mn, Al and Co sites 2(c) and 3(g) of space group P6/mmm. The distribution of the substituting elements Mn, Al and Co on the two latter sites was determined from synchrotron powder diffraction experiments by using t he diffraction contrast produced by anomalous dispersion effects. The results of joint Rietveld refinement on three patterns collected close to the K edges of Ni, Co and Mn and on one pattern collected away fro m these edges showed that Al and Mn occupy almost exclusively site 3(g ), while Co is distributed over sites 2(c) and 3(g) with a slight pref erence for site 3(g).