Synthesis And Electrochemical Performance Of LiV₃O₈ Cathode Material

with a layered structure has attracted significant interest as cathode material for Li-ion batteries because it is proposed to be a low cost material with large specific capacity and also has the potential of providing a long cycle life. It is also well known that the preparation methods and post-treatments have significant influence on the electrochemical properties of LiV3O8. So the preparation and improving methods of this material were studied in this dissertation. Electrochemical performance of the gained LiV3O8 cathode materials was also studied in this paper.LiV3O8 cathode materials are post-treated by a special emulsion method (EM) and then calcinated at different temperatures. The experimental results show that structure of these oxides is different from LiV3O8 prepared by the solid-state reaction (STATE) route, although the starting materials are identical in these cases, and the EM product prepared at 500℃exhibits a better electrochemical behavior than its counterpart prepared by traditional methods (STATE) or by EM at other temperatures. Its initial discharge capacity is 305 mAh/g, and still maintains 250.2 mAh/g after 100 cycles at 0.2 C at the voltage range of 1.8～4.0 V.We report on the synthesis, characterization, and electrochemical lithium intercalation of LiV3O8 nanorods, which was prepared through a very facile hydrothermal route. The diameters of the as-synthesized LiV3O8 nanorods was about 150 nm. It was found that by simply controlling the reaction parameters, such as the dwell time and the reaction temperature, the transformation of microrods to particles was readily achieved. Electrochemical measurements revealed that the as-prepared LiV3O8 nanorods at 400℃displayed high initial discharge capacities (292.5 mAh/g at 60 mA/g and at room temperature) and excellent high-rate capability. This result indicates that the LiV3O8 nanorods are promising cathode candidates for primary lithium batteries used in long term.This paper describes systematic studies on the effect of polyethylene glycol (PEG) molecular weight on the crystal structure and particularly the electrochemical performance of LiV3O8. Scanning electron microscopy (SEM) results indicate that after the decomposition of PEG, the structure of resultant products exhibits differences in morphology (shape, particle size and specific surface area). The electrochemical results show that LiV3O8 cathode material treated by PEG (mean molecular weight of 10,000) has greater initial discharge capacity and better cyclic stability than other materials treated with PEG of different molecular weight. Its initial discharge capacity is 282.1 mAh/g and maintains 222.2 mAh/g after 50 cycles in 0.5 C rates (150 mA/g).We report here the preparation of Ag-doped LiV3O8 for use as a cathode material in rechargeable lithium ion batteries. Synthesis was carried out by sol-gel methods and low temperature calcination using V2O5 wet gel, LiOH.H2O, and AgNO3 as raw materials. The product was characterized by X-ray diffraction (XRD), and its electrochemical behavior as a cathode material was studied by galvanostatic charge-discharge, cyclic voltammetry, and AC impedance techniques. The experimental results show that a cathode of Ag-doped LiV3O8 has greater initial discharge capacity than one made with undoped materials, and that Ag-doped LiV3O8 electrodes, especially Ago.o4Lio.96V3O8, show the best long-life cycling performance. All of the doped powders show better stability at the 2.6 V plateau efficiency, due to their more stable cell impedance.Layered LiTiyV3-0.8yO8 cathode materials with y=0,0.04,0.06,0.08 were prepared by a sol-gel process following a calcination at 350℃in air for 16 h, and show differences in morphological properties (shape, particle size and specific surface area) and electrochemical properties (first charge profile, reversible capacity and rate capability). The LiTiyV3-0.8yO8 powders were characterized by means of X-ray diffraction (XRD), charge/discharge cycling, cyclic voltammetry (CV), and scanning electron microscopy (SEM). LiTiyV3-0.8yO8 was crystallized to a well layered structure. Its initial specific discharge capacity was higher than that of pristine material. When y=0.04, the sample showed the highest initial discharge capacity of 348.9 mAh/g at a current density of 60 mA/g in the voltage range 1.8-4.0 V, and also higher discharge capacity and better cycle ability.