A kinetic two-phase and equilibrium solid solution in spinel Li4+xTi5O12

The zero strain Li4+xTi5O12 material as a two-phase system is, in contrast to common knowledge, unstable at room temperature (see figure), and it is fast Li insertion that leads to a kinetically induced effective two-phase reaction. The solid-solution-induced disorder, resulting from the mixed 8a/16c occupation, is most likely responsible for the high rate capabilities in Li4+xTi5O12.