Particle size effects of carbon sources on electrochemical properties of LiFePO 4/C composites

George Ting Kuo Fey, Hui Jyuan Tu, Kai Pin Huang, Yi Chuan Lin, Hsien Ming Kao, Shih Hung Chan

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Abstract Carbon-coated LiFePO 4 cathode materials were prepared by a solid-state method incorporating different sizes of polystyrene (PS) spheres as carbon sources. In scanning electron microscope images, small PS spheres appear more effective at preventing aggregation of LiFePO 4 particles. From transmission electron microscopy images, it was found that the LiFePO 4 particles were completely uniformly coated with 5-nm carbon layer when the carbon source was 0.22 μm PS spheres. When the size of PS sphere was increased to 2.75 μm, a network of carbon was formed and wrapped around the LiFePO 4 to create a conductive web. Raman spectroscopy and four-point probe conductivity measurement showed that using larger sizes of PS spheres as carbon sources leads to greater conductivity of LiFePO 4/C. The LiFePO 4 precursor sintered with 0.22 μm PS spheres delivered an initial discharge capacity of 145 mAh g -1 at a 0.2 C rate, but it only sustained 289 cycles at 80% capacity. When the diameter of PS spheres was increased to 2.75 μm, the discharge capacity of LiFePO 4/C decreased, but the cycle life reached 755 cycles, the highest number in this work probably due to the network formation of carbon wrapping around LiFePO 4 particles.

Original languageEnglish
Pages (from-to)1857-1862
Number of pages6
JournalJournal of Solid State Electrochemistry
Volume16
Issue number5
DOIs
StatePublished - May 2012

Keywords

  • Carbon structure
  • Cathode material
  • Li-ion batteries
  • LiFePO /C
  • Morphology
  • PS sphere

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