Synthesis and Characterization of LiFePO₄-C/ PANI Composite for Cathode Material of Lithium Ion Battery

Abstract:

In-situ polymer coated LiFePO₄-C composite material has been synthesized using different oxidizing agents viz. (NH₄)₂S₂O₈, KMnO₄ and K₂Cr₂O₇. Polyaniline (PANI) with chains having diameter ≤ 200 nm have been grown separately by self oxidation process of aniline monomers using the above oxidizing agents. For the synthesis of LiFePO₄-C active material, initially raw material FePO₄/PANI has been synthesized by chemical precipitation method and added with LiCOOCH₃ followed by heat treatment at 700°C under reducing (Ar/H₂=90/10) atmosphere for 16 hrs. The synthesized LiFePO₄-C material has particle size of about 100 nm. The polymer coated LiFePO₄-C composite was synthesized by undergoing in-situ polymerization of aniline monomers added with fixed quantity of LiFePO₄-C. XRD analysis reveals formation of single phase pure active material LiFePO₄-C and mixed phase containing LiFePO₄ to FePO₄ for polymer coated LiFePO₄-C composite. The carbon content in the LiFePO₄-C was estimated to be 5 wt%, however, the PANI content in the composites was different with different oxidizing agent. These PANI contents in the composites synthesized with (NH₄)₂S₂O₈, KMnO₄ and K₂Cr₂O₇ are 14, 15 and 17 wt% respectively which have been estimated by thermal gravimetric analysis (TGA) of the materials. Electrical conductivities of the composite materials were determined by Impedance spectroscopy method. The composite material synthesized with (NH₄)₂S₂O₈ has higher conductivity compared to those synthesized with KMnO₄ and K₂Cr₂O₇. The higher conductivity of the composite synthesized with (NH₄)₂S₂O₈ may be attributed to the presence of partial chain structure in polymer coating as seen by microstructural observations on the composite.

• Periodical: Advanced Materials Research (Volume 585)
• Pages: 240-244
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.585.240
• Online since: November 2012
• Authors: Rajeev Sehrawat, Anjan Sil
• Keywords: In Situ Polymerization, LiFePO₄/C Composite, Polymer

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