Preparation Of Li₂Mn₄O₉and/or F Doped Li₂Mn₄O₉Powders Via Sol-gel Method, Hydrothermal Method, And Their Electrochemical Properties

Because that there are resistance to overcharge, good security, abundant manganeseresources, cheap, non-toxic and pollution-free, and so on. Li2Mn4O9is considered one ofthe most promising cathode materials for lithium ion batteries. In this paper, sol-gelmethod has been used to synthesize spinel Li2Mn4O9and F doped Li2Mn4O9powders useovalbumin as chelating agent and pH value adjust agent. Moreover, Li2Mn4O9nanorodhas been prepared by through hydrothermal precursor method.In the preparation of the Li2Mn4O9powder by sol-gel method, the influences of thesintering temperature and the dosage of ovalbumin on the crystal structure, morphologyand electrochemical properties were discussed in detail. In the synthesis of the F dopedLi2Mn4O9via sol-gel method, it is focused on the study of the impact of the addition of Fon the crystal structure, morphology and electrochemical performance of theas-synthesized Li2Mn4O9powder. In the preparation of Li2Mn4O9nanorod byhydrothermal precursor method,the influences of the sintering temperature on themicrostryctures and electrochemical properties have been investigated emphatically. Theobtained samples were characterized by through TG-DTA, FI-IR, XRD, SEM,Charge-discharge, CV and EIS, and the obtained main results as follows:1. In the synthesis of Li2Mn4O9powders via sol-gel method,the sintering temperatureand the dosage of ovalbumin have both influence on the crystal structure, morphologyand electrochemical properties of the as-synthesized Li2Mn4O9powders. The feasiblesintering temperature is400℃and the feasible dosage of ovalbumin is about0.1ml.Under the optimal sintering temperature and dosage of ovalbumin, the obtainedLi2Mn4O9powders possess the pure spinel structure and capacity is125.9mAh/g, itcan keep83.3%of the initial capacity after20cycles. 2. The various addition F doped Li2Mn4O9powders (Li2Mn4O9-xFx,x=0,0.05,0.10,0.30,0.50,0.70,1.00) have been prepared by sol-gel method,and the results showthat:①The doping amount of F has influence on the structure and morphology of theproduct.②The doping amount of F has influence on the electrochemical performance of theproduct. A small amount of the doping F can enhance the electrochemical performance,but an excessive F can weaken it. The proper doping amount of F is x=0.30.3. MnO2nanorod has been synthesized by hydrothermal precursor method, and thenusing the obtained MnO2nanorod as precursor, the Li2Mn4O9nanorods with spinelsturctures were prepared by the conventional solid creramics under diffirent sinteringtemperature(300℃-600℃). The test results show that:The sintering temperatures have influence on the crystal structure, morphology andof the Li2Mn4O9nanorod. The optimal calcining temperature is500℃. The as-preparedLi2Mn4O9powders sintered at the optimal sintering temperature exhibit a perfect spinelstructure, a good morphology and a excellent electrochemical properties. The firstdischarge capacity is102.9mAh/g, it can maintain85%of the initial capacity after20cycles.