Enhanced electrochemical performance of carbon-coated LiMPO4 (M = Co and Ni) nanoparticles as cathodes for high-voltage lithium-ion battery

Olivine LiMPO4 (M = Co and Ni) nanoparticles
have been synthesized by the polyvinylpyrrolidone (PVP)
assisted polyol method and adopted the resin coating process
for carbon coating on the surface of the nanoparticles. The Xray diffraction (XRD) and Fourier transform infrared (FTIR)
spectroscopy studies confirmed the phase and structural coordination of bare and carbon-coated LiMPO4 (M = Co and
Ni) nanoparticles, respectively. The formation of uniform carbon layer of nanometer-measured thickness over nanoparticles is confirmed by the high-resolution transmission electron
microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDS). Wagner’s polarization study explains an improved electronic transport number (te) for carbon-coated
LiMPO4 (M = Co and Ni) cathodes as compared to bare samples. The electrochemical study of the Li-ion cells shows the
first cycle discharge capacities of 180 and 97 mAh/g at 0.1 C
for the cathodes LiCoPO4/C and LiNiPO4/C, respectively,
which is an improvement of 21.2 and 25.8 % as compared
to bare samples. The enhancement of electrochemical performance of the cells is attributed to the improved electronic
properties of cathode materials due to the presence of carbon
on the surface of nanoparticles