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Layered Li1+xV3O8become one of the most potential cathode materials for lithium ionbatteries for over three decades because of its advantages of high capacity, compatible operationvoltage, facile preparation，excellent stability in air and low cost. However, its shortcomingssuch as structural changes and slow rate of Li+diffusion during charge/discharge processes lendto poor cycle performance, which is unfavorable for its development and practical applications.In order to solve the above-mentioned disadvantages, the structural stability and rate of Li+diffusion of Li1+xV3O8have been improved by doping Na+and coating LaF3in this paper, andhence to enhance the electrochemical performance of Li1+xV3O8. The prepared cathodematerials were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）,energy dispersive spectrometer （EDS）, transmission electron microscopy （TEM）, cyclicvoltammetry （CV）, galvanostatic intermittent titration technique （GITT）, electrochemicalimpedance spectroscopy （EIS）and galvanostatic charge/discharge measurements. The effects ofcontents of lithium, Na+dopant and LaF3coating on the physical and electrochemicalperformances of Li1+xV3O8were investigated and the preparation conditions were optimized.Li1+xV3O8（x=0,0.1,0.2,0.3） cathode materials were prepared by a sol-gel method usingNH4VO3, LiC2H3O2·2H2O and citric acid as raw materials and the effects of Li contents on theelectrochemical performance of Li1+xV3O8were investigated. The results show that Li1.2V3O8exhibits best electrochemical performance among all Li1+xV3O8（x=0,0.1,0.2,0.3） samples. Inthe voltage range of2.04.0V, Li1.2V3O8displays initial discharge capacities of305, and173mAh g-1at0.1C and2C, respectively. It remains discharge capacities of266，and113.2mAh g-1at0.1C and2C, respectively, and the corresponding capacity retentions are80%and49.6%,respectively. Additionally, Li+diffusion coefficients of Li1.2V3O8and LiV3O8were determinedby GITT measurement, and the value for Li1.2V3O8is higher than that of LiV3O8, which furtherelucidates that the higher Li+diffusion coefficient favors improving the electrochemicalperformance of LiV3O8.LaF3coated Li1.2V3O8cathode materials were synthesized by a co-deposition methodusing NH4F and La（NO3）3and the prepared Li1.2V3O8samples as raw materials, and thecontents of LaF3coating on the electrochemical performance were explored. Theelectrochemical tests indicate that the optimal LaF3coating is3wt%. This optimal LaF3coatedLi1.2V3O8shows initial discharge capacities of298and169.8mAh g-1at0.1C and2C in thevoltage range of2.04.0V, respectively, and the corresponding capacity retentions are as high as93%and81%, respectively, after50cycles.Li1.2-xNaxV3O8（x=0,0.03,0.05,0.07） cathode materials were prepared by a sol-gel methodusing NH4VO3,LiC2H3O2·2H2O,NaNO3and citric acid as raw materials, and the effects of Nacontents on the electrochemical performance of the Na-doped cathode materials were studied.The results indicate that the Na doping is favorable to improve the electrochemical performanceof Li1.2V3O8and Li1.15Na0.05V3O8is of best electrochemical performance among all theNa-doped samples. The results showed that compared with other samples, Li1.15Na0.05V3O8hasthe best electrochemical performance. In the voltage range of2.0-4.0, the initial dischargecapacity of Li1.15Na0.05V3O8was as high as312,182mAh g-1at0.1C and2C, respectively. After50cycles its discharge capacities still remain280.8and136.5mAh g-1,corresponding to thecapacity retentions are90%and75%, respectively.
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