Carbon nanotube and graphene nanosheet co-modified LiFePO4nanoplate composite cathode material by a facile polyol process

Abstract

LiFePO4 nanoplate based composite cathode materials with 5 wt% multi-walled carbon nanotubes and 1 wt% graphene nanosheets have been prepared via a single-step polyol process under low temperature, without using any inert gas input and post heat treatments. The carbon nanotubes have been embedded into the inside of LiFePO4 nanoplates, whilst graphene nanosheets have been coated on the surface, and both carbon additives have interlaced to form a crosslinked three-dimensional mixed conducting net-work, to assist the charge transfer throughout the inside and outside of cathode materials. The structural and morphological properties of the nanocomposites have been investigated by X-ray diffraction, Ramanspectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The electrochemical properties have been studied by charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. Both pristine LiFePO4 nanoplate and the nanocomposites display an orthorhombic olivine-type structure. The nanocomposites present excellent electrochemical performance with a reversible specific capacity of 166 mAh g-1at the current rate of 10 mA g-1, and a capacity retention ratio close to 100% after 100 cycles.