Improved Electrochemical Performance of Spherical Li2FeSiO4/C Cathode Materials via Mn Doping for Lithium-Ion Batteries

Abstract

The Mn doped spherical Li2FeSiO4/C cathode materials are successfully synthesized through a citric acid-assisted sol-gel method. The effects of Mn doping on the chemical composition, structure characteristics, morphology and elemental distribution of the as-prepared polyanionic cathode materials are investigated by the inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM) and energy-dispersive X-ray spectroscope (EDX). The results indicate that the alien atom Mn can effectively and equably dope into the samples as well as maintain the original spherical morphology. Besides, the electrochemical measurements reveal that the sample doped with 5% Mn delivers the highest initial discharge capacity of 248.5mAhg−1 at 0.1C under ambient temperature in a voltage range of 1.5–4.8V, the retention of the capacity is as high as 91.9% after 200 cycles. Additionally, the sample doped with 5% Mn also exhibits a good rate capability with a discharge capacity of 105.6mAhg−1 even at a high rate of 10C. The excellent electrochemical performances can be ascribed to the appropriate Mn doping, which can effectively optimize the crystal structure of Li2FeSiO4/C and facilitate the diffusion coefficient of lithium-ion during cycling process.