SEM/EDX, XPS, and impedance spectroscopy of LiFePO₄ and LiFePO₄/C ceramics

Abstract

The powders of LiFePO 4 compounds have been synthesized by the solid state reaction, and LiFePO 4 /C composites were sintered in argon gas. The ceramics of LiFePO 4 were sintered in air. The surfaces of the ceramics were investigated by a scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDX). The binding energies of the Fe 2p, P 2p, and O 1s core level of LiFePO 4 ceramic and LiFePO 4 /C composite surfaces were determined by X-ray photoelectron spectroscopy (XPS). The deconvolutions of Fe 2p core level XPS are associated with Fe 2+ and Fe 3+ valence states of the ceramics. Impedance spectroscopy of the ceramics has been performed in the frequency range of 10 Hz to 3 GHz by low frequency and microwave impedance spectrometers. Two-and four-probe methods were used for measurements at low frequencies. The LiFePO 4 /C composite was investigated in nitrogen gas, and the measurements of LiFePO 4 were conducted in air. The measurements of the electrical properties of the ceramics were carried out in the temperature interval of 300-500 K.

Citric Acid-Assisted Inexpensive Semi-Wet Combustion Synthesis and Characterization of Ultrafine LiFe0.95Ti0.05PO4 and LiFePO4 Polycrystalline Materials

“…The O 1 s [Figs. 9 (e) and 10 (e)] of the LFP and LFTP materials were similar at 531.4 eV with respect to the corresponding spectra for oxygen in LiFePO 4[18]. For the dopant as Ti in LiFePO 4 inFig.…”

In Situ Electrospinning Synthesis of N‐Doped C Nanofibers with Uniform Embedding of Mn Doped MFe1−xMnxPO4 (M = Li, Na) as a High Performance Cathode for Lithium/Sodium‐Ion Batteries

“…( Figure 3e). [45,46] Furthermore, the N element which is mainly originated from PAN can be divided into three circumstances: pyridinic N (N-6), pyrrolic N (N-5), and quaternary N (N-Q), and the location of their spectrum are 398.4, 400.9, and 401.4 eV (Figure 3f), respectively. According to the previous reports, the NQ in the carbon fibers are helpful to improve the conductivity of whole materials via importing extra free electrons, N-5 and N-6 can absorb exotic atoms and act as storage sites for lithium ions.…”

The use of Raman and XPS spectroscopy to study the cathode material of LiFePO4/C

“…4, B), synthesized at 700 °C for 1 h, have been examined. The spectra of 709.6 -711.3 еV relate to the Fe 2+ states of iron, and those formed by components in a range of 712.6 -714.5 еV relate to the Fe 3+ states of iron in LiFePO4; these data correlate with [15][16][17] . The peaks with energies of 716.1 and 718 eV are satellites, which correspond to the Fe 2+ and Fe 3+ states respectively (Table II).…”