The electrochemical performance of substituted Li1.05M0.05Mn1.90O4 spinel electrodes (M = Li, Mg, Zn, Al) in lithium cells has been studied as a function of the oxidation states of the M and Mn ions in the parent electrode, and the occupancy of the tetrahedral A sites by the Li and the M ions. At 5% substitution of manganese, neutron diffraction analyses show that the M ions reside at the A sites of the A[B-2]O-4 spinel structure. The electrochemical data showed that at 50 degreesC the rate of capacity fade can be correlated with the M-ion occupancy of the A sites. A possible explanation for this phenomenon is provided. (C) 2003 The Electrochemical Society.