Effect of carbon coating on the crystal orientation and electrochemical performance of nanocrystalline LiFePO4.

Abstract Extensive efforts have been devoted to carbon coated LiFePO 4 to optimize its performance by increase conductivity, however, the coating effect on crystalline size and shape have never been touched. Herein, we reveal the influence of carbon content on the crystal orientation, particle size, and electrochemical performance of the nanocrystalline LiFePO 4 , which is synthesized by a hydrothermal method with predominantly (010) faces exposure. We found that an increase of the carbon content from 1.65 to 6 wt% modified the preferential orientation of the LiFePO 4 crystal from the (010) plane to the (100) plane. The solid electrolyte interface resistance R sf also increased, causing a decrease in the electrochemical performance of LiFePO 4 /C cathode materials. Among all the carbon coated samples, LiFePO 4 /C composites coated with 1.65 wt% carbon exhibited the best initial discharge capacity and efficiency of 162 mAh g−1 and 95.4% at 0.1C, respectively. This performance can be attributed to the low R sf value and preferential orientation of the (010) plane. Highlights • The effect of carbon coating on the crystalline orientation and electrochemical performance of LiFePO 4 was investigated. • Preferential orientation transformed from (010) to (100) with increase carbon content. • R sf reached the minimum at 1.65 wt% carbon content and increased with increase carbon content. • LiFePO 4 /C with 1.65 wt% carbon has the best performance because of preferential orientation of (010) plane and low R sf. [ABSTRACT FROM AUTHOR]