Oxygen-deficient spinel (LiMn)(3)O4-z was successfully synthesized by melt-impregnation method. The chemical composition of each spinet sample was carefully analyzed and the value of z was correlated with its discharge capacity at about 3.2 V (C-3,C-2v). The linear relationship between C-3,C-2v and z was theoretically deduced from the structural consideration of (LiMn)(3)O4-z. (c) 2005 Elsevier B.V. All rights reserved.