Synthesis and Electrochemical Characteristics of Li[Co[sub x]Li[sub (1/3−x/3)]Mn[sub (2/3−2x/3)]]O[sub 2] Compounds

Abstract

0.17, 0.20, 0.25, 0.33, and 0.5) compounds were prepared using a simple combustion method and studied by the X-ray diffraction method, electrochemical techniques, and X-ray absorption near-edge structure (XANES) analysis. The Rietveld analysis showed that these compounds could be classified as the structure type. Both a and c parameters decreased linearly, while increased with the increase of Co content. The oxidation states of Mn and Co ion in the compounds were refined as 4+ and 3+, respectively, by XANES analysis. Irreversible voltage plateaus were observed in the initial charge profile of these compounds, as in the case of -based oxides. The plateaus shifted to the higher voltage range, with the Co content decreased. The delivered discharge capacity gradually decreased from about 265 to 150 mAh/g as the Co content decreased from to 0.1. On cycling, the smooth discharge profile was converted to two subplateaus. The high Co content in the compounds suppressed the phase conversion during cycling, which led to a relatively stable cyclic performance. © 2004 The Electrochemical Society. All rights reserved.