Spinel LiMn2-y-zLiyZnzO4-eta F eta (0 <= y <= 0.1, 0 <= z <= 0.1, and 0 <= eta <= 0.18) cathodes have been synthesized by solid-state reactions at 800 degrees C, employing ZnF2 to prepare the oxyfluorides and ZnO to prepare the oxides. Although the LiMn2-y-zLiyZnzO4 samples show a significant improvement in electrochemical performance compared to LiMn2O4, the oxyfluoride cathodes LiMn2-y-zLiyZnzO4-eta F eta exhibit better capacity retention with an increase in capacity of up to 10 mAh/g compared to the corresponding oxide analogs LiMn2-y-zLiyZnzO4. The superior electrochemical performances of the LiMn2-y-zLiyZnzO4-eta F eta oxyfluoride cathodes are found to be due to a suppression in manganese dissolution, smaller lattice parameter difference Delta a between the two cubic phases formed during the charge-discharge process, lower microstrain, and maintenance of good crystallinity during cycling. (C) 2007 The Electrochemical Society.