Improvement of electrochemical and thermal stability of LiFePO4 cathode modified by CeO2

CeO2-modified LiFePO4 cathode was synthesized by using the triblock copolymer poly(ethylene oxide)block-poly(propylene oxide)-block-poly(ethane oxide) (P123) as a template. CeO2-modified (2 wt.%), 5 wt.% CeO2-modified and pristine LiFePO4 powders were characterized by XRD and SEM measurements. The electrochemical behaviors were investigated by cyclic voltammetry measurements in Li2SO4 aqueous electrolyte. It was shown that all compounds undergone lithium-ion deintercalation and intercalation upon oxidation and reduction at different scan rates. The electrochemical lithium-ion deintercalation-intercalation processes of the CeO2-modified LiFePO4 electrodes were improved compare to the pristine LiFePO4 electrode, especially at elevated temperature and larger scan rates. 2 wt.% CeO2-modified material showed better electrochemical performance than that of 5 wt.% and pristine materials. A linear relationship between the peak current and the square root of scan rate for all peak pairs indicated that the Li+ deintercalation/intercalation processes occurred in all compounds were diffusion-control led. The D-coproduct(+) values of the 2 wt.% CeO2-modified LiFePO4 electrode is much larger both at room temperature and 40 degrees C. The electrochemical impedance spectroscopy tests were carried out before and after CV measurements. It was found that the CeO2 modification produced a good electrical contact between oxides, which was in very good agreement with the electrochemical behaviors of electrodes. The treatment with CeO2 should improve the comprehensive properties of the cathode materials for lithium-ion batteries at elevated temperature and larger scan rates. (C) 2009 Elsevier B.V. All rights reserved.