In situ XAFS study of the electrochemical deintercalation of Li from Li1-xMn2-yCryO4 (y=1/9, 1/6, 1/3)

Chemical states and structural changes accompanying the electrochemical Li deintercalation of Li1-xMn2-yCryO4 (y = 1/9, 1/6, 1/3) were studied by the in situ X-ray absorption fine structure (XAFS) technique. The X-ray absorpt ion near-edge structures (XANES) of Mn and Cr as a function of x showed tha t the 4 V plateau of the material can be ascribed to the oxidation of Mn3to Mn4+, and Cr does not contribute to the charging, but to the stabilizati on of the spinel structure against the delithiation. The extended EXAFS ana lysis of Li1-x(Mn, Cr)(2)O-4 revealed that the Jahn-Teller distorted Mn3+-O octahedra become uniform when the cell is fully charged. (C) 2001 Elsevier Science B.V. All rights reserved.