Synthesis Of Sulfur/Carbon Composite Cathode Materials For Lithium Ion Battery

Lithium ion batteries are considered as the promising power sources of portable devices and electric vehicles for their high energy density and power density. As a high capacity positive material candidate for lithium ion batteries, sulfur-containing material has been researched for many years. However, sulfur is actually difficult to be applied directly as cathode materials for its low conductivity as well as irncompatibility with electrolyte, which results in the poor electrochemical cycling performance. The preparation of sulfur-containing compound or composite material is the main method to build an effective ion and electron transferring tube or to alleviate the solving problem of sulfur. The main research included in the dissertation is as follows:1)the synthesis of sulfur/porous carbon composite materials; 2) the exploration of sulfur/polyacrylonitril and sulfur/polyacrylonitril/carbon composite, including their synthesis process and the investigation of the electrochemical performance.Carbon matrix was synthesized by hydrothermal synthesis method. Phenol resin, sucrose, glucose were used as the carbon precursors, respectively. The preparation process of carbon matrix was investigation in detail. The morphology and particle size of the carbon matrix made from resin was modified by adjusting the process temperature and controlling the additives of the surfactant. The results showed that the carbon materials, which were prepared by adding PlurobicF-127 of 1.28g at temperature 130°C, possessed uniform particle size and regular spherical shape. The direct solution method and low-temperature melting diffusion method were executed to prepare the sulfur/carbon composite cathode materials. The sulfur/carbon composite prepared by low-temperature melting diffusion method presented excellent electrochemical performance. The results with sucrose and glucose as the carbon source precursors exhibited that sulfur content and the mode of the sulfur loading on the carbon matrix did affect the performance of the composite seriously.PAN-S and PAN-S/carbon composite cathode materials were synthesized by facile heat treatment method. The influence of the ratio of precursors, the electrode formula as well as the charging-discharging current on the electrochemical performance of the final electrode was investigated systematically. The cycling performance and specific capacity of the composite electrode could be improved generally with the increment of the conductive additives. The cyclability was affected by the charging-discharging constant current.