Surface Treatment of LiFePo4Cathode Material for Lithium Secondary Battery

Abstract

In this study, nano-crystallized <TEX>$Al_2O_3$</TEX> was coated on the surface of <TEX>$LiFePO_4$</TEX> powders via a novel dry coating method. The influence of coated <TEX>$LiFePO_4$</TEX> upon electrochemical behavior was discussed. Surface morphology characterization was achieved by transmission electron microscopy (TEM), clearly showing nano-crystallized <TEX>$Al_2O_3$</TEX> on <TEX>$LiFePO_4$</TEX> surfaces. Furthermore, it revealed that the <TEX>$Al_2O_3$</TEX>-coated <TEX>$LiFePO_4$</TEX> cathode exhibited a distinct surface morphology. It was also found that the <TEX>$Al_2O_3$</TEX> coating reduces capacity fading especially at high charge/discharge rates. Results from the cyclic voltammogram measurements (2.5-4.2 V) showed a significant decrease in both interfacial resistance and cathode polarization. This behavior implies that <TEX>$Al_2O_3$</TEX> can prevent structural change of <TEX>$LiFePO_4$</TEX> or reaction with the electrolyte on cycling. In addition, the <TEX>$Al_2O_3$</TEX> coated <TEX>$LiFePO_4$</TEX> compound showed highly improved area-specific impedance (ASI), an important measure of battery performance. From the correlation between these characteristics of bare and coated <TEX>$LiFePO_4$</TEX>, the role of <TEX>$Al_2O_3$</TEX> coating played on the electrochemical performance of <TEX>$LiFePO_4$</TEX> was probed.