Li2FeP2O7 powders are synthesized via solid state method by using different lithium sources (LiH2PO4, Li2CO3, LiOH and LiF). The solid state reaction mechanism of the Li2FeP2O7 is investigated by using TG-DSC and XRD analysis. The effects of different Li-sources on the structure, morphology and electrochemical performances of Li2FeP2O7 are investigated. The results indicate that the optimum synthesis temperature is about 650°C. LiH2PO4 is the most appropriate choice among them for synthesis of Li2FeP2O7. The Li2FeP2O7 synthesized by using LiH2PO4 as lithium source exhibits the best electrochemical properties, delivering an initial discharge capacity of 110.3, 98.2 and 80.0mAhg−1 at the rates of 0.025C, 0.1C and 1C, respectively. Furthermore, after various discharge rates, a discharge capacity of 101.6mAhg−1 at 0.025C can be still achieved, and the capacity retention is about 92.1% after 110 cycles.