High electrochemical performance of LiFePO₄ cathode material via in-situ microwave exfoliated graphene oxide

Compared with thermally exfoliated graphene oxide (TEGO) prepared at high temperature of 800 °C and a long time of 12 h, microwave exfoliated graphene oxide (MEGO) is successfully synthesized at 800 W for 2 min benefiting from "inert and instant heating" of microwave irradiation and employed to optimize electrochemical performance of LiFePO₄. The as-obtained LiFePO₄/MEGO exhibits overwhelming superiorities to LiFePO₄/TEGO, particularly in high-rate performance. Although LiFePO₄/MEGO delivers the similar specific capacity of 158.1 mAh · g^-1 as well as the LiFePO₄/TEGO at the rate of 0.1 C, the LiFePO₄/MEGO performs smaller polarization of 53.3 mV resulting in better specific energy of 518.1 Wh · kg^-1 and energy efficiency of 89.8%. Even at the high rate of 10 C and 20 C, the LiFePO₄/MEGO delivers excellent specific energy of 300.3 Wh · kg^-1 and 229.7 Wh · kg^-1 (with corresponding specific capacity of 104.3 mAh · g^-1 and 87.3 mAh · g^-1 respectively), much better than those of the LiFePO₄/TEGO. After 2000 cycles, the LiFePO₄/MEGO still performs excellent rate capabilities with 91.2% and 83.8% retention respectively.