Kinetic analysis of one-step solid-state reaction for Li_4Ti _5O_(12)/C

摘要

The kinetics of one-step solid-state reaction of Li_4Ti _5O_(12) in a dynamic nitrogen atmosphere was first studied by means of thermogravimetric-differential thermal analysis technique at five different heating rates. According to the double equal-double steps method, the Li_4Ti _5O_(12) solid-state reaction mechanism could be properly described as the Jander equation, which was a three-dimensional diffusion with spherical symmetry, and the reaction mechanism functions were listed as follows: f(α) ≥ 3/2(1 - α)~(2/3)[1 - (1 - α)~(1/3)]~(-1), G(α) ≥ [1 - (1 - α)~(1/3)]~2. In FWO method, average activation energy, frequency factor, and reaction order were 284.40 kJ mol ~(-1), 2.51×10~(18) min~(-1), and 1.01, respectively. However, the corresponding values in FRL method were 271.70 kJ mol~(-1), 1.00×10~(17) min~(-1), and 0.96, respectively. Moreover, the values of enthalpy of activation, Gibbs free energy of activation, and entropy of activation at the peak temperature were 272.06 kJ mol~(-1), 240.16 kJ mol~(-1), and 44.24 J mol~(-1) K~(-1), respectively.