Titanium-doped Li2FeSiO4/C composite as the cathode material for lithium-ion batteries with excellent rate capability and long cycle life

Abstract

Li2Fe1-xTixSiO4/C cathode materials are designed and realized by a facile sol-gel method. The effects of various Ti doping amounts on the microstructure and electrochemical performance of Li2FeSiO4/C are investigated comprehensively. X-ray powder diffraction result confirms the crystal structure of Li2Fe1-xTixSiO4/C to be monoclinic Li2FeSiO4 with minor decrease in the unit cell volume. X-ray photoelectron spectroscopy shows that Ti does successfully dope into the crystal structure of Li2FeSiO4. Galvonostatic charge-discharge experiments are used to study the electrochemical performance of Ti-doped Li2FeSiO4/C as a lithium-ion batteries cathode material. As results, Li2Fe0.98Ti0.02SiO4/C exhibits the best electrochemical performance with the discharge capacity of 102.8 and 91.1 mAh g−1 even at 5 and 10 C (1 C = 165 mA g−1) high rate after 1000 cycles. Additionally, the electrochemical kinetic performance of Li2Fe1-xTixSiO4/C is further determined by electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic intermittent titration technique. The results indicate that the enhanced electrochemical performance can be attributed to the effect of Ti doping, which not only enhances the structural stability, but also improves the kinetic properties of Li2FeSiO4/C.