In situ X-ray absorption spectroscopy studies of nanosized LiAl0.15Mn1.85O4 cathode material in an aqueous solution

We have performed in situ Mn K-edge X-ray absorption spectroscopy (XAS) studies on nanosized LiAl0.15Mn1.85O4 cathode material at various charging and discharging potentials in an aqueous solution (9.0 M LiNO3). The associated changes in the electronic and local atomic structures were investigated during the course of charging and discharging. The B1 and B2 peaks appeared in the Mn K-edge X-ray absorption near-edge structure spectra of LiAl0.15Mn1.85O4 were due to pronounced multiple scattering effect. Two types of Mn-O bonds, namely Mn-O(4) and Mn-O(2), were observed in the first coordination shell. It was found that the Mn-O(4) and the second shell Mn-Mn/Al bond distances as well as the Debye-Waller factors decrease on charging and increase on discharging. In contrast, the Mn-O(2) bonds show an elongation on charging and contraction on discharging. The Debye-Waller factor of Mn-O(2) does not change significantly during both charging and discharging. Thus, we infer that the ordering of Mn-O-6 octahedra is mainly due to the contribution from Mn-O(4) bonds. (C) 2003 The Electrochemical Society.