High Rate Performance of Nano-Structured LiFePO4/C Cathode Material Prepared by a Polymer-Assisted Method from Inexpensive Iron(III) Raw Material

 Wenjing Pu Wenjing Pu , Wei Lu Wei Lu , Zhipeng Chen Zhipeng Chen , Kai Xie Kai Xie , Chunman Zheng Chunman Zheng
Российский электрохимический журнал
Abstract / Full Text

A spherical carbon coated nano-structured LiFePO4 composite is synthesized by a polymer-assisted method from inexpensive iron(III) raw material. The synthesis process includes two steps: (1) nano-FePO4/polyaniline composites with core–shell structure are synthesized through the in-situ polymerization of aniline; (2) LiFePO4/C composites are prepared through carbothermal reduction with the nano-FePO4/polyaniline and sucrose as raw materials. The structure, surface morphology of the materials and the properties of the coated carbon are investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The obtained nano-structured LiFePO4/carbon composite has a spherical morphology compose of ordered olivine structure, which is coated with 2 nm thick amorphous layer of carbon. At the same time, the materials are linked together by amorphous carbon from sucrose decomposition. The aniline plays an important role during the synthesis process. The electrochemical properties of the materials are tested by charge–discharge measurements. The obtained nano-structured LiFePO4/carbon composite shows excellent electrochemical properties, especially its high rate performance. It exhibits initial discharge capacities of 138, 136, 118, 103, and 92 mA h g–1 at 0.2, 1, 10, 20, and 30 C rate between 3.65 and 2.0 V, respectively. That makes it a promising cathode material for advanced power Li-ion batteries. The excellent electrochemical properties of the materials can be ascribed to the two different amorphous carbons. The carbon coated on the surface of LiFePO4 effectively reduces inter-particle agglomeration of the LiFePO4 particles. The carbon interlinked between the composite improve the electronic conductivity. Those shorten the lithium ions diffusion length and improve the electric contact between LiFePO4 particles.

Author information
  • Institutes of Physical Scicence and Information Technology, Anhui University, 230601, Hefei, China

    Wenjing Pu, Wei Lu & Zhipeng Chen

  • Institute of Applied Physics, PLA Army Academy of Artillery and Air Defense, 230031, Hefei, China

    Wenjing Pu

  • Department of Material Science and Engineering, School of Aerospace Science and Engineering, National University of Defense Technology, 410073, Changsha, China

    Kai Xie & Chunman Zheng

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