Synthesis, non-isothermal kinetic and thermodynamic studies of the formation of LiMnPO4 from NH4MnPO4·H2O precursor

Abstract

NH4MnPO4·H2O was successfully synthesized by precipitating method. The LiMnPO4 was successfully generated through solid state reaction between synthesized NH4MnPO4·H2O precursor and Li2CO3. The morphologies were observed to depend on the reaction temperatures. The thermal decomposition of NH4MnPO4·H2O and the formation process of LiMnPO4 were confirmed by TG/DTG/DTA, FTIR, AAS/AES, XRD and SEM methods. The average crystallite size of NH4MnPO4·H2O, Mn2P2O7 and LiMnPO4 were found to be around 51.2, 44.9 and 48.1 nm, respectively. The non–isothermal kinetic parameters (kinetic triplet: Eα, A, g(α)) of the formation process of LiMnPO4 were evaluated from TG data by using Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose methods. The iterative methods of both equations were carried out to determine the exact values of Eα. The Coats–Redfern equation and kinetic compensation effects were successfully applied to confirm the activation energy and the most probable mechanism functions of the formation of LiMnPO4. The thermodynamic functions (ΔH≠, ΔS≠, ΔG≠) of the transition state complexes of the formation of LiMnPO4 were calculated from the kinetic parameters for the first time.