Preparation And Electrochemical Properties Of Cathode Materials For Lithium Sulfur Battery

Energy and environmental problems caused by the rapid development of industrial civilization has attracted more and more attention from all countries and regions of the world. The demand of energy is more and more urgently. In order to find the alternative energy of oil and coal, various attempts have been made. Among them, lithium ion battery has many advantages including high capacity, high output voltage, high energy density, environmental friendly, no memory effect, long life cycle. Lithium sulfur battery with higher specific capacity and higher energy density is a new system among many kinds of lithium batteries. The cathode material of lithium sulfur battery is elemental sulfur, which is abundant, environmental friendly, making lithium sulfur battery to be noticed widely. We prepared three kinds composites through different methods, which aim to modify the cathode material. These three composites are NanoS@G, Sulfur@hollow polypyrrole sphere and Sulfu@active carbon/polypyrrol respectively.1. Preparation of NanoS@G and the electrochemical properties for lithium sulfur batteryThe graphene oxide was obtained via a modified hummers method with the raw materials of crystalline flake graphite, P2O5, NaS2O4, H2SO4, KMnO4, H2O2. The graphene oxide and nano-S powder were mixed with the existence of sodium dodecylsulphate (SDS) through solvothermal method and the NanoS@G was obtained. The phase, morphology and structure of the sample were characterized by XRD, TG, SEM, TEM and XPS and the electrochemical properties were tested on the cell tester. We compared the NanoS@G and the S-GMixture and found that the electrochemical properties of NanoS@G was much better than the S-GMixture. The dischange capacity under0.2C of NanoS@G kept at720mAh/g after100cycles but the S-G Mixture kept at300mAh/g.2. Preparation of Sulfur@hollow polypyrrole sphere and its electrochemical properties as cathode material for lithium sulfur battery systemHollow polypyrrole sphere is obtained through template method with SiO2sphere, then, hollow polypyrrole spheres and nano-S powder are combined via a heat treatment. The phase, morphology and structure of the sample were characterized by XRD, TG, SEM, and TEM and the electrochemical properties were tested on the cell tester. We Analysis the influence of the special structure of hollow polypyrrole spheres. The discharge capacity under0.5C of Sulfur@hollow polypyrrole kept at620mAh/g after100cycles.3. Preparation of sulfur@active carbon/polypyrrol and the electrochemical properties of cathode materials for lithium sulfur battery systemWe prepared sulfur@active carbon/polypyrrol through a in-situ deposition method with the raw materials of pyrrol, active carbon, FeCl3, NaS2O3, HC1. The phase, morphology and structure of the sample were characterized by XRD, TG, SEM, and TEM and the electrochemical properties were tested on the cell tester. The electrochemical properties of cathode materials has a great improvement. The dischange capacity under0.5C of Sulfur@active carbon/polypyrrol kept at about1000mAh/g after100cycles.