Na2EDTA-assisted hydrothermal synthesis and electrochemical performance of LiFePO4 powders with rod-like and block-like morphologies

Nano and micro-sized LiFePO4 were synthesized by disodium ethylenediamine tetraacetate (Na(2)EDTA) assisted hydrothermal synthesis method with the pH of synthesizing solution in the range from 2 to 8. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and electrochemical performance experiments. The obtained results showed that the pH of synthesizing solution played a key role in the formation of the final products with different morphologies, including rod-like and block-like structures and so on. The formation mechanism and the influence of Na2EDTA on the morphology of LiFePO4 micro- and nanocrystals were investigated as a function of pH value. The results of electrochemical performance measurement revealed that the charge/discharge cycling characteristics of the samples were varied by tailoring their morphologies. Particularly, the block-like LiFePO4 particles with the average size of 200-600 nm present the highest initial discharge capacity of 141 mAh/ g at 0.1C rate, and cycling stability of this sample is optimal among all the obtained products owing to its good diffusion properties. It also exhibits an excellent rate capability with high discharge capacities of more than 93.2 mAh/g at 5C after 80 cycles. The present study offers a simple way to synthesize and design high performance cathode materials for lithium-ion batteries by the methods of morphology control without carbon coating or doping with supervalent cations. (C) 2015 Elsevier B.V. All rights reserved.