A three-dimensional LiFePO4/carbon nanotubes/graphene composite as a cathode material for lithium-ion batteries with superior high-rate performance

A three-dimensional lithium iron phosphate (LiFePO4)/carbon nanotubes (CNTs)/graphene composite was successfully synthesized via solid-state reaction. The LiFePO4/carbon nanotubes/graphene (LFP-CNT-G) composite used as Li-ions battery cathode material exhibits superior high-rate capability and favorable charge-discharge cycle performance under relative high current density compared with that of LiFePO4/carbon nanotubes (LFP-CNT) composite and LiFePO4/graphene (LFP-G) composite. Graphene nanosheets and CNTs construct 3D conducting networks are favor for faster electron transfer, higher Li-ions diffusion coefficient and lower resistance during the Li-ions reversible reaction. The synergistic effect of graphene nanosheets and CNTs improves the rate capability and cycling stability of LiFePO4-based cathodes. The LFP-CNT-G electrode shows reversible capacity of 168.9 mA h g(-1) at 0.2 degrees C and 115.8 mA h g(-1) at 20 degrees C. The electrochemical impedance spectroscopy demonstrate that the LFP-CNT-G electrode has the smallest charge-transfer resistance, indicating that the fast electron transfer from the electrolyte to the LFP-CNT-G active materials in the Li-ions intercalation/deintercalation reactions owing to the three-dimensional networks of graphene and carbon nanotubes. (C) 2014 Elsevier B.V. All rights reserved.