Search

Based on the method of in situ polymerization synthesis combined with two-step sintering process, LiFe1−xVx(PO4)(3−y)/3Fy/C was prepared. The effects of V and F co-doping on the structure, morphology, and electrochemical performances of LiFePO4/C were investigated by X-ray diffraction, Fourier transform infrared spectra, scanning electron microscope, charge/discharge tests, and electrochemical impedance spectroscopy, respectively. The results indicated that the V and F co-doping did not destroy the olivine structure of LiFePO4/C, but it can stabilize the crystal structure, decrease charge transfer resistance, enhance Li ion diffusion velocity, further improve its cycling and high-rate capabilities of LiFePO4/C.

The lithium-ion battery cathode materials spinel LiMn2O4, LiAl0.1Mn1.9O4 and Li0.94Na0.06Al0.1Mn1.9O4 materials are synthesised by sol–gel method. The structure, morphology and electrochemical performances of the aluminium and sodium co-doped materials are studied by X-ray diffraction measurement, scanning electron microscopy, and Electron diffraction spectroscopy, respectively. The results reveal that appropriate amount doping of aluminium and sodium does not change the spinel structure of LiMn2O4. Those materials have a good crystallinity and the sizes are approximately 150 nm. The initial discharge capacity of Li0.94Na0.06Al0.1Mn1.9O4 is 113.8 mAh/g at 0.5 C. Compared with the rate capability of LiMn2O4, the discharge capacity of 107.5 mAh/g at 5 C for Li0.94Na0.06Al0.1Mn1.9O4 has 46.8% improvement. Obviously, aluminium and sodium co-doping is a very effective way to improve LiMn2O4 rate capability.