Optimized electrochemical performance of three-dimensional porous LiFePO4/C microspheres via microwave irradiation assisted synthesis

Abstract Microwave irradiation assisted synthesis (MIAS) is successfully employed to prepare three-dimensional (3D) porous microspherical aggregation of LiFePO 4 /C nanoparticles as the cathode material of lithium ion battery. XRD, SEM, and TEM studies confirm that highly crystalline LiFePO 4 without any impurity phase can be synthesized under microwave irradiation of 700 W for 5 min. The as-obtained LiFePO 4 /C sample is prepared via MIAS consisting of nanopores (20–30 nm) and nanoparticles (20–30 nm) which are coated with uniform, complete carbon layers (about ∼3 nm). These superior physical characters provide LiFePO 4 /C (MIAS) excellent electrochemical performance at 0.1C including the high discharge capacity of 156.9 mAh g −1 and the low polarization of 51.5 mV. At the discharge rate of 1C, LiFePO 4 /C (MIAS) exhibits the low polarization of 202.3 mV, high capacity of 126.7 mAh g −1 , high discharge voltage of 3.33 V, and specific energy of 398.5 kWh kg −1 , all of which are much better than those measured for the sample prepared via conventional heat treatment (CHT). At even high rate of 5C, LiFePO 4 /C (CHT) fails to discharge whereas LiFePO 4 /C (MIAS) is able to deliver the discharge capacity of 95.5 mAh g −1 . The low polarization of LiFePO 4 /C (MIAS) results in the good discharge voltage of 3.06 V, high specific energy of 278.8 Wh kg −1 , and excellent energy efficiency of 72.0% at 5C.