LiMn2O4 cathode materials, having various particle sizes and using different preparation techniques, have been prepared. Surface areas of these materials measured by two alternative methods of Brunauer, Emmett, and Teller (BET) and methylene blue (MB) adsorption methods did not agree with each other in both absolute and relative values. The electrochemical performance such as capacity fading on 55 degreesC cycling and irreversible capacity correlate well with the surface area measured by the MB method but not with that by the BET method. The electrochemical performance improved as the surface area (by MB) decreased. (C) 2001 Elsevier Science B.V. All rights reserved.