Carbon nanotube and graphene nanosheet co-modified LiFePO ₄ nanoplate composite cathode material by a facile polyol process

LiFePO ₄ 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 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 166 mAh g ^-1 at the current rate of 10 mA g ^-1 , and a capacity retention ratio close to 100% after 100 cycles.