Variation of carbon coatings on the electrochemical performance of LiFePO4 cathodes for lithium ionic batteries

Abstract

The applications of LiFePO₄ (LFP) in high-power lithium ion batteries (LIBs) are limited due to its two major drawbacks: poor electronic conductivity and low lithium ion diffusivity, which could be greatly improved chiefly by reducing the size of LFP crystallites to nanoscale and introducing a conductive carbon-coating layer. In this study, asphalt-derived and glucose-derived carbon proved to be soft carbon-coating (SCC) and hard carbon-coating (HCC), respectively. Asphalt and glucose were therefore used as carbon precursors to prepare varied carbon-coated LFP nanoparticles. The electrochemical properties of the LFP/carbon composites were studied using cyclic voltammetry, electrochemical impedance spectroscopy and charge/discharge cycling. The effects of variation of carbon coatings on the electrochemical performance of LiFePO₄ cathodes was investigated in detail, and it was found that LFP/SCC showed a superior performance in capacity and rate capability than that of LFP/HCC. It was therefore concluded that soft carbon coating on LFP exhibits better electrochemical performance than hard carbon coating, demonstrating that asphalt could be used as a cheap and efficient carbon source material of LiFePO₄ cathodes for LIBs.