Carbon nanotube and graphene nanosheet co-modified LiFePO4 nanoplate composite cathode material by a facile polyol process

Abstract

LiFePO4 nanoplate based composite cathode materials with 5wt% multi-walled carbon nanotubes and 1wt% 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 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 LiFePO4 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.