Real-time synchrotron powder X-ray diffraction study of the antisite defect formation during sub- and supercritical synthesis of LiFePO₄and LiFe_1−xMn_xPO₄nanoparticles

Abstract

In situ synchrotron powder X‐ray diffraction (PXRD) is used to study the formation of LiFePO4 nanoparticles during hydrothermal synthesis from LiOH, H3PO4, and two different iron precursors, FeSO4 and (NH4)2Fe(SO4)2. Furthermore, the synthesis of Li(Fe1−xMnx)PO4 (x = 0.25, 0.50 and 0.75) from LiOH, H3PO4 and FeSO4/MnSO4 is studied. The reactions involve an unknown intermediate phase, which is not the previously observed intermediate NH4FePO4·H2O. The intermediate phase quickly transforms into LiFePO4 and Li(Fe1−xMnx)PO4 even at rather low temperatures. The presence of ammonium enhances the formation of LiFePO4, and it also leads to a significant reduction in the concentration of Li–Fe antisite defects. The in situ PXRD technique allows one to follow the influence of time, temperature and manganese doping on the antisite defect concentration, and it is shown that even under supercritical conditions a reaction time of several minutes is required to suppress the defects. This makes flow synthesis of defect‐free LiFePO4 and Li(Fe1−xMnx)PO4 nanoparticles challenging.

High performance nano-sized LiMn1−xFexPO4cathode materials for advanced lithium-ion batteries

“…1e and Table S2 †). 28,30,31 Fe substituting usually happens in 4c-site which is occupied by Mn ion. However, the cation antisite defects could be arisen, so that a slight amount of Fe/Mn ions (<1%) could occupy 4a site, while Li ions occupy 4c site.…”

“…So the synthesized route should be strictly controlled to limit the antisite defect. 29,31 The chemical compositions of LiMn…”

Singular Structural and Electrochemical Properties in Highly Defective LiFePO4 Powders

“…Their nature is most likely similar to the intermediate species described by Jensen et al 22 . The presence of crystalline Li2SO4H2O detected by X-ray diffraction even after several washings of the precipitate with H2O accounts for its large excess in solution.…”

Supercritical Fluid Synthesis of LiCoPO4 Nanoparticles and Their Application to Lithium Ion Battery

“…Supercritical fluid method possess unique properties, such as gas like diffusivity, low viscosity, and the density of the reactants closer to that of liquid, these properties leads to the preparation of high quality materials. In recent days, varieties of electrode materials have been successfully synthesized via supercritical fluid process [32][33][34][35][36][37][38]. Recently, our group has reported supercritical fluid synthesis of nanosize lithium metal phosphates [30,38,39], lithium metal silicates [40][41][42][43][44], and flurophosphates [45].…”