The Li+/Co3+-codoped LiMn2O4 spinel was prepared using two-step synthesis method consisting of solid-state reaction method and citrate modified sol-gel method, in order to investigate the changes of the electrochemical properties of the spinel LiMn2O4 on the amount of Li+/Co3+ ions. The FT-infrared spectra, chemical analysis, and Rietveld refinements of their XRD data revealed that the manganese ions in the 16d sites were replaced by both lithium and cobalt ions. Thus, the composition of obtained powders could be expressed as the new spinel formula (Li)[Mn2-xLix/4Co3x/4]O-4, that is, (Li)[Mn1-3x/23+Mn1+x/24+Lix/4Co3x/43+]O-4. The inclusion of lithium and cobalt ions in 16d sites enhanced the electrochemical cyclability of LiMn2O4 at the expense of a reduction in the initial charge capacity. The improvement in cycling performance was mainly attributed to the suppression of Jahn-Teller distortion as shown in (Li)[Mn2-xLix]O-4 and (Li)[Mn2-xCox]O-4. (C) 2001 Elsevier Science B.V. All rights reserved.