Sodium gluconate-assisted hydrothermal synthesis, characterization and electrochemical performance of LiFePO4 powders

摘要

Nano- and micro-sized LiFePO4 powders were synthesized by a sodium gluconate (C6H_(11)NaO7)-assisted hydrothermal synthesis method at 220 °C for 10 h with pH = 2-7. The resulting powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray spectrometer (EDS). The obtained data showed that the pH of synthesis solution played a key role in the formation of the LiFePO4 powders with different morphologies, such as ball-like microspheres, irregular microspheres with the agglomerated rods and particles, sphere-like nanoparticles and nano-ellipsoids. The results from electrochemical performance measurements revealed that the charge-discharge cycling characteristics of the samples were strongly dependent on their morphologies. In particular, the ellipsoidal LiFePO4 nanoparticles with the average size of 70-90 nm showed the highest initial discharge capacity of 150 mA h g~(-1) at 0.1 C rate, and cycling stability of the ellipsoidal LiFePO4 nanoparticles was optimum among all the samples prepared due to their dual advantages of high tap density and good diffusion property. The present study offers a simple morphology-controllable route, without carbon coating or doping with supervalent cations, to synthesize and to design high performance cathode materials for lithium-ion batteries.