Solution combustion synthesis of high-rate performance carbon-coated lithium iron phosphate from inexpensive iron (iii) raw material

Abstract

A facile way for the synthesis of LiFePO₄ composite using a solution combustion technique based on the glycine–nitrate process with inexpensive iron (III) as the raw material is introduced. Pure phase LiFePO₄ was obtained at an optimal glycine to LiFePO₄ ratio of 4:1. To further increase the electrode performance, sucrose is applied as an organic carbon source. The introduction of sucrose after the auto-combustion is found to be the most effective way in improving electrode performance. The as-synthesized LiFePO₄/C sample contained about 2.86 wt.% carbon shows an attractive discharge capacity of about 160 mA h g⁻¹ at a 0.1 C rate and retains a capacity of 110 mA h g⁻¹ at a 5 C rate. In addition, the electrodes show excellent cycling performance during the 90 cycles at various rates. The rate limiting step for the electrode reaction is explored with the chronoamperometry technique and it demonstrates the surface kinetics is effectively improved for the LiFePO₄ electrode modified with a proper amount of carbon.