Lithium deintercalation in the spinel LiMn2O4

Using a new electrolyte composition stable against oxidation up to 5V vs. Li, the full electrochemical deintercalation of lithium from the spinel LiMn2O4 has been studied. The origin of two new reversible oxidation-reduction peaks centered around 4.5 V and 4.9 V vs. Li is examined. The capacity associated with these peaks is shown to depend on both the nominal composition x in LixMn2O4 and the synthesis conditions, namely annealing temperatures and cooling rates. We discuss the evidence that these peaks are related to local structural defects and propose a reasonable explanation for their origin.