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

Olivine LiMPO 4 (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 X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy studies confirmed the phase and structural co-ordination of bare and carbon-coated LiMPO 4 (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 ( t e ) for carbon-coated LiMPO 4 (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 LiCoPO 4 /C and LiNiPO 4 /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.