Kerun Yang

Study on the synthesis and properties of LiV3O8 rechargeable lithium batteries cathode

A new simple synthetic method was employed to produce LiV3O8 compound in which LiOH, V2O5 and NH4OH were used as the starting reactants. At first, V2O5 reacted with LiOH and NH4OH in liquid solutions to obtain a compound containing Li and V, which was then calcined at 370, 450 and 550 degreesC for 8 h, respectively. The electrochemical properties of the LiV3O8 compound were studied by galvanostatic charge-discharge, and the highest capacity of 274 mAh g(-1) was obtained for the LiV3O8 compound calcined at 370 C in the range of 1.8-4.0 V. In the fifteenth cycle, its capacity remained 257 mAh g(-1). The inspections by X-ray diffraction and SEM indicated that different calcining temperatures resulted in different structure, which resulted in different discharge capacity

Kinetic analysis of one-step solid-state reaction for Li4Ti5O12/C.

The kinetics of one-step solid-state reaction of Li(4)Ti(5)O(12)/C 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(4)Ti(5)O(12)/C 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.