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

K P Abhilash; P Christopher Selvin; B Nalini; Hui Xia; Stefan Adams; M V Reddy

doi:10.1021/acsomega.8b00527

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

ACS Omega. 2018 Jun 15;3(6):6446-6455. doi: 10.1021/acsomega.8b00527. eCollection 2018 Jun 30.

Authors

K P Abhilash^{1

2

2}, P Christopher Selvin³, B Nalini⁴, Hui Xia^{2

2}, Stefan Adams¹, M V Reddy^{1

1}

Affiliations

¹ Department of Physics and Department of Materials Science and Engineering, National University of Singapore, 117542, Singapore.
² School of Materials Science and Engineering and Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing 210094, China.
³ Department of Physics, Bharathiar University, Coimbatore 642046, Tamilnadu, India.
⁴ Department of Physics, Avinashilingam University for Women, Coimbatore 642043, Tamilnadu, India.

Abstract

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.