Morphology control of lithium iron phosphate nanoparticles by soluble starch-assisted hydrothermal synthesis

Lithium iron phosphate (LiFePO4) is a potentially high efficiency cathode material for lithium ion batteries, but the low electronic conductivity and one-dimensional diffusion channel for lithium ions require small particle size and shape control during the synthesis. In this paper, well-crystallized and morphology-controlled LiFePO4 cathode material for lithium-ion batteries is successfully synthesized via a soluble starch-assisted hydrothermal method at 180 degrees C for 5 h, followed by calcining with phenolic resin at 750 degrees C for 6 h. In this study, we investigate the effect of five different concentrations of starch solution on controlling morphology of LiFePO4. Interestingly, the nano-sized LiFePO4 particles obtained in 0.075 mol L-1 starch solution exhibit a spheroidal microstructure, while the platelet shape LiFePO4 particles are synthesized in lower or higher concentration of starch solution. The mechanism and process of forming such spheroidal microstructure is discussed. These unique structural and morphological properties of LiFePO4 lead to high specific capacity and stable cycling performance. Analysis of the electrochemical impedance spectroscopy reveals that nano-sized carbon/polyacene coated LiFePO4 cathode materials play an critical role in achieving excellent electrochemical performance. (C) 2014 Elsevier B.V. All rights reserved.