Synthesis, thermodynamic and kinetic studies of the formation of LiMnPO4 from a new Mn(H2PO2)2·H2O precursor

Abstract

Mn(H2PO2)2·H2O was successfully synthesized by a simple precipitation method. The LiMnPO4 was further generated by the solid-state reaction between the new synthesized Mn(H2PO2)2·H2O precursor and LiCl at 700 °C in N2 atmosphere. The LiMnPO4 was generated via four decomposition steps. The samples were characterized by FTIR/FT-Raman, XRD, SEM, AAS/AES, and TG/DTG/DTA techniques. The kinetic parameters of the LiMnPO4 formation were determined from TG data at four heating rates. The exact activation energy (E) values were calculated by the iterative methods. The most probable mechanism functions g(α) were evaluated from 35 models by using the masterplots and nonlinear model-fitting methods. The most probable mechanism functions g(α) of the LiMnPO4 formation were found to be the P1/3 (first step), R1 (second step), R2 (third step), and D4 (final step), respectively. The thermodynamic functions of activation (ΔS≠, ΔH≠, and ΔG≠) were calculated by the activated complex theory of Eyring. The kinetic parameters and thermodynamic functions of the formation of LiMnPO4 from the a new Mn(H2PO2)2·H2O precursor are reported the first time.