Synthesis of iron phosphate powders by chemical precipitation route for high-power lithium iron phosphate cathodes

Carbon-coated lithium iron phosphate (C/LFP) composite has been synthesized at 650 degrees C in an N-2 atmosphere by calcination/pyrolysis method using amorphous FePO4 center dot xH(2)O nanopowders as the precursor. The key factor for preparing the C/LFP composites is to start with the co-precipitation synthesis of FePO4 center dot xH(2)O spheres at pH 3. The C/LFP composite exhibits good crystallinity, well-dispersed particles of 250 nm, and in situ carbon coating (thickness: 3-4 nm) over the surface of LFP crystallites. The as-prepared C/LFP composite delivers a high discharge capacity of 162.1 and 119.7 mAh g(-1) at rates of 0.1 and 5 C, respectively. This enhanced rate capability is ascribed to the synergetic effect on the C/LFP cathode that combines (i) quasi-spherical nanoparticles and (ii) a thin carbon layer. Additionally, the C/LFP composite presents a high tap density (1.34 g cm(-3)), inducing high performance without sacrificing the volume energy density. Accordingly, the result reveals an efficient approach for synthesizing the C/LFP materials with excellent performance, which is beneficial for large-scale applications such as hybrid electric vehicles. (c) 2012 Elsevier Ltd. All rights reserved.