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

Abstract

Extensive efforts have been devoted to carbon coated LiFePO4 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 LiFePO4, 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 LiFePO4 crystal from the (010) plane to the (100) plane. The solid electrolyte interface resistance Rsf also increased, causing a decrease in the electrochemical performance of LiFePO4/C cathode materials. Among all the carbon coated samples, LiFePO4/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 Rsf value and preferential orientation of the (010) plane.