Carbon nanotube and graphene nanosheet co-modified LiFePO_4 nanoplate composite cathode material by a facile polyol process

摘要

LiFePO_4 nanoplate based composite cathode materials with 5wt% 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 LiFePO_4 nanoplates, whilst graphene nanosheets have been coated on the surface, and both carbon additives have interlaced to form a crosslinked three-dimensional mixed conducting network, 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, Raman spectroscopy, 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 LiFePO_4 nanoplate and the nanocomposites display an orthorhombic olivine-type structure. The nanocomposites present excellent electrochemical performance with a reversible specific capacity of 166mAhg~(-1) at the current rate of 10mAg~(-1), and a capacity retention ratio close to 100％ after 100 cycles.