Neutron Pair Distribution Function Study of FePO₄ and LiFePO₄

Abstract

Neutron powder diffraction studies of the compounds FePO 4 and LiFePO 4 are reported. Rietveld refinement of the diffraction data provides averaged structures for both materials that are in good agreement with the published structures. In addition, detailed investigations of the short-range ion−ion correlations within each compound have been performed using the reverse Monte Carlo (RMC) modeling of the total scattering (Bragg plus diffuse) data. Although the short-range structural information for LiFePO 4 is consistent with the long-range (averaged) picture, a small, but statistically significant, proportion of the anions is displaced away from their ideal sites within the RMC configurations of FePO 4 . These anion displacements are discussed in terms of a small concentration of Li + /Fe 2+ occupying the empty octahedral sites, probably arising from incomplete delithiation of the LiFePO 4 and/or antisite (Li + −Fe 2+ ) defects introduced during the delithiation process.

Local Structure of Mott Insulating Iron Oxychalcogenides La$_{2}$O$_{2}$Fe$_{2}$O$M$$_{2}$ ($M$ = S, Se)

“…139) which is consistent with the previous studies [14,15]. Our findings show that the lattice parameters of La Having obtained a confirmation of the global lattice symmetry for our samples, we then investigated the local symmetry [28,32,[42][43][44][45] where a mid = a+b 2 and δ = | a−b a+b |. All refinements were performed on the Nyquist grid.…”

Local structure of Mott insulating iron oxychalcogenides La2O2Fe2OM2(M=Karki1, Alfailakawi2, Frandsen3 et al. 2021Phys. Rev. B

“…Having obtained a confirmation of the global lattice symmetry for our samples, we then investigated the local symmetry [30,34,[44][45][46][47]. The local structure data of La 2 O 2 Fe 2 OM 2 (M = S, Se) were analyzed by using the PDF refinement program PDFGUI [37] to determine the lattice parameters, scale factor, atomic positions, and the thermal parameters.…”

One-Pot Synthesis of LiFePO4/N-Doped C Composite Cathodes for Li-ion Batteries

“…However, the discontinuous FeO 6 co-edge octahedral network in LiFePO 4 crystals and the PO 4 tetrahedrons between them affect the electron transfer and the intercalation/deintercalation of Li + [11,12]. Moreover, the path of Li + diffusion is easily blocked by Fe-Li antisite defects, resulting in the diffusion coefficient of Li + being much lower than the theoretical value [13]. The intrinsically low Li + diffusion coefficient (~10 −14 cm 2 •s −1 ) and electronic conductivity (~10 −10 S•cm −1 ) cause serious capacity attenuation in the LiFePO 4 battery in high-speed (≥5 C) charging and discharging [14,15].…”