Synthesis and electrochemical performance of LiV3O8/carbon nanosheet composite as cathode material for lithium-ion batteries
To improve the rate capability and cyclability of LiV3O8 cathode for Li-ion batteries, LiV3O8 was modified by forming LiV3O8/carbon nanosheet composite. The LiV3O8/carbon nanosheet composite was successfully achieved via a hydrothermal route followed by a carbon coating process. The morphology and structural properties of the samples were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). TEM observations demonstrated that LiV3O8/carbon composite has a very flat sheet-like morphology, with each nanosheet having a smooth surface and a typical length of 400–700 nm, width of 200–350 nm, and thickness of 10–50 nm. Each sheet was surrounded by a thick layer of amorphous carbon. Electrochemical tests showed that the LiV3O8/carbon composite cathode features long-term cycling stability (194 mAh g−1 at 0.2 C after 100 cycles) and excellent rate capability (110 mAh g−1 at 5 C, 104 mAh g−1 at 10 C, and 82 mAh g−1 at 20 C after 250 cycles). Electrochemical impedance spectra (EIS) indicated that the LiV3O8/carbon composite electrode has very low charge-transfer resistance compared with pristine LiV3O8, indicating the enhanced ionic conductivity of the LiV3O8/carbon composite. The enhanced cycling stability is attributed to the fact that the LiV3O8/carbon composite can prevent the aggregation of active materials, accommodate the large volume variation, and maintain good electronic contact.