Electrochemical Analysis of the Carbon-Encapsulated Lithium Iron Phosphate Nanochains and Their High-Temperature Conductivity Profiles

Carbon-encapsulated LiFePO 4 (LFP) nanochains were prepared as a cathode material for lithium batteries by sol-gel method using citric acid as the carbon source. The prepared LFP/C material is characterized by structural, morphological, and electrochemical characterization. LFP/C shows an orthorhombic olivine structure with " Pnma " space group having an average particle size of 50 nm. The uniform distribution of LFP particles coated by the carbon matrix as a nanochain array has been analyzed by scanning electron microscopy and transmission electron microscopy analysis of the sample. The electrochemical performance of the LFP/C nanochain has been analyzed using galvanostatic cycling, cyclic voltammetry, and impedance analysis of the assembled batteries. The sol-gel-derived LFP/C nanochain exhibits better capacity and electrochemical reversibility in line with the literature results. The high-temperature conductivity profile of the sample has been recorded from room temperature to 473 K using impedance analysis of the sample. The transport dynamics have been analyzed using the dielectric and modulus spectra of the sample. A maximum conductivity up to 6.74 × 10 -4 S cm -1 has been obtained for the samples at higher temperature (448 K). The nucleation and growth at higher temperature act as factors to facilitate the intermediate phase existence in the LiFePO 4 sample in which the phase change that occurs above 400 K gives irreversible electrochemical changes in the LFP/C samples.