Phase transition of lithiated-spinel Li 2Mn 2O 4 at high temperature

Abstract

The phase transition of Li 2Mn 2O 4 spinel at high temperature was investigated by XRD, TG/DTA, average oxidation state of Mn and cyclic voltammeric techniques. The results reveal that the Li 2Mn 2O 4 spinel is unstable. At high temperature, it is easy to transform into [Li 2−2 x ] tet[Mn 2− x Li x ] octO 4, which accompanies the formation of Li 2MnO 3 impurities. The phase transition is associated with the transfer of Li + from tetrahedral 8a sites to octahedral 16d sites. With the increasing sintering temperature from 450 °C to 850 °C, the phase structure varies from lithiated-spinel Li 2Mn 2O 4 to Li 4Mn 5O 12-like to LiMn 2O 4-like and finally to rock-salt LiMnO 2-like. In addition, a way of determining x with average oxidation state of Mn and the content of Li 2MnO 3 was also demonstrated.