A high-performance LiFePO4/C composite was synthesized by improved solid-state method using starch and PEG6000 as a complex carbon source. The raw materials were mixed by wet-mixing method using de-ionized water as medium. For comparison, a LiFePO4/C composite was prepared using PEG6000 as single carbon source. XRD results show that the sample prepared by improved solid-state method has ordered olivine structure and high purity due to the perfect mixing of the raw materials by wet-mixing method. Fine particles with an average particle size about 400 nm are examined by scanning electron microscopy (SEM). TEM observation illustrates that the complex carbon source leads to the homogeneous and complete carbon coating on LiFePO4 particle surface, resulting in its uniform particle size distribution and enhanced electronic conductivity. All the above factors lead to the better room-temperature and low-temperature electrochemical performances of LiFePO4/C composite synthesized by improved solid-state method in both LiFePO4/Li half-cell and 18650 cylindrical full-cell. (C) The Author(s) 2017. Published by ECS. All rights reserved.