In Situ Synthesis and Properties of Carbon-Coated LiFePO[sub 4] as Li-Ion Battery Cathodes

Abstract

An in situ synthesis method for carbon-coated LiFePO 4 powders has been investigated in detail using inexpensive FePO 4 as an iron source and polypropylene as a reductive agent and carbon source. Thermogravimetric and differential thermal analysis of the precursor mixture indicated that the pyrolysis of polypropylene and the combination reaction of LiFePO 4 could be processed synchronously at a synthesis temperature between 500 and 800°C. X-ray diffraction analyses and scanning electron microscopy observations showed that LiFePO 4 /C composites with fine particle sizes and homogeneous carbon coating could be directly synthesized by the in situ method. The electrochemical performances of the carbon-coated LiFePO 4 powder synthesized at 700°C were evaluated using an electrochemical model cell by galvanostatic charge/discharge and cyclic voltammetry measurements. The in situ synthesized LiFePO 4 /C composite had a high electrochemical capacity of 164 mA h g Ϫ1 at the 0.1C rate, and possessed a favorable capacity cycling maintenance at the 0.3 and 0.5C rates. The good electrochemical properties of the LiFePO 4 /C composite are suggested to originate from the good crystallinity, the fine particle sizes, and the efficient electronic conductive coating layer of the material.

Electrospinning of Highly Electroactive Carbon‐Coated Single‐Crystalline LiFePO4 Nanowires

“…[50] ) Together with the well-ordered single-crystalline structure of the nanowires, this situation promotes fast Li insertion and extraction. [51] Each nanowire is coated with an amorphous carbon layer of 2-5 nm thickness (Figure 2 b), which suppresses aggregation [52][53][54] and is thin enough not to block Li transport. Individual SCNW-LFP nanowires are loosely connected with each other to form a three-dimensional network.…”

The Origin of the Residual Carbon in LiFePO4Synthesized by Wet Milling

“…1 shows XRD patterns obtained from the LiFePO 4 particles after the heat treatment at 600 o C. Both patterns showed typical diffraction peaks corresponding to LiFe-PO 4 . 15 The lattice parameters calculated from the XRD patterns were same regardless of the milling condition ( Table 1). The particle sizes of both specimens were calculated from the fullwidth at half maximum (FWHM) of the diffraction peaks in Fig.…”

The Science of Electrode Materials for Lithium Batteries

“…Although the material is sufficiently conductive to be useful, it has many characteristics of an oxide insulator. Good success has been achieved by coating small particles of LiFePO 4 with a conductive carbon, and practical electrodes are made with this approach [85][86][87][88][89][90][91][92][93][94][95][96][97][98][99][100][101]. Nevertheless, the rate capabilities are less than optimal, and the coating step requires careful process control.…”