Kinetic analysis of the second stage of the solid-phase synthesis of Li4Ti5O12 from a mechanically activated mixture of rutile and lithium carbonate

The effect of mechanical activation of a mixture of micron-sized rutile and lithium carbonate in a Pulverisette-5 ball mill on the kinetics of the second stage of Li4Ti5O12 synthesis was investigated. The values of the energy of activation of the second stage of lithium pentatitanate synthesis from starting mixtures that were mechanically activated for 1 and 60 min were determined to be 463 ± 23 kJ·mol−1 and 393 ± 20 kJ·mol−1, respectively. It was shown that mechanical activation of the starting mixture leads to the destruction of lithium carbonate with the release of CO2 and an increase in the reactivity of TiO2, which strongly influences the synthesis of lithium pentatitanate. The results of our study demonstrate that mechanical activation promotes a reduction in the temperature of the first stage of lithium pentatitanate synthesis, that is, the formation of Li2TiO3, by approximately 230°С and a reduction in the temperature of the second stage, i.e., the the formation of Li4Ti5O12, by 50 °C. We show that single-phase Li4Ti5O12 with a particle size of ca. 200 nm can be successfully synthesized from a mechanically activated starting mixture at 750 °C with a 3 h holding time or at 800 °C with a 0.5 h holding time.