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

Carbon-encapsulated LiFePO4 (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 LiFePO4 sample in which the phase change that occurs above 400 K gives irreversible electrochemical changes in the LFP/C samples.