Study On Preparation Of Sulfur/Carbon Film For Lithium/Sulfur Battery

Due to the highest theoretical specific capacities and energy, low cost and toxicity, elemental sulfur has caused wildly attention and be considered the most competitive cathode material for the next generation lithium batteries. However, for the insulating nature of sulfur and the loss of polysulfides in the liquid organic electrolyte, lithium-sulfur batteries exhibited low active material utilization and poor cycle performance. In order to overcome these problems, researchers have done a lot of work. Recent research shows that to fabricate sulfur/carbon composites is one of the most effective ways. The carbon material has high specific surface and absorbability. This structure can prevent polysulfides of the reaction products from dissolving in the liquid organic electrolyte and increase the conductivity of the electrode, which can much improve the cycle performance of the cathode.In this work, two types of cathode respectively prepared by Hot-filament chemical vapor deposition and heating treatment method. The composites were characterized by X-ray diffraction, scanning electron microscope (SEM), EDAX-Falcon energy spectrometer (EDAX). The electrochemical properties of the electrodes were evaluated by charge -discharge tests, circulating tests and cyclic voltammetry(CV).The element sulfur in the composite material prepared by heating treatment is highly dispersed in the micro-holes of the active carbon. It is found that the composite with sulfur content of 53wt% has the best electrochemical performance. The initial discharge capacity of this composite electrode is up to 953mAh/g, and after 20 cycles it is still retained at about 615mAh/g, the capacity retention is 64%, which shows a good cycle performance.On this basis, amorphous carbon film prepared by HFCVD has a complicated microstructure with nano-sized fibrous network. By heating treatment the element sulfur in melting state enter into the network structure, finally the cathode material is prepared. Electrochemical test indicated that the polarization, reversibility, active material utilization of the cathode material and the cycle performance of the battery prepared by HFCVD was better then the heating treatment method.