| The Li-S battery has a theoretical capacity of1675mAh/g and theoretical energy densities of2500Wh/Kg. Beyond that, sulfur has the advantages of being rich, environmental friendly, inexpensive andso on. In consideration of the above advantages, the Li-S battery has been under great attention and wasthe best Lithium-ion battery system now. Yet, the Li-S battery shows lots of deficiencies, includingelectrical insulation of the elemental sulfur, its electrical conductivity is5×10-30S/cm at room temperature.In the process of discharge, a solution of polysulfides in the electrolyte and transfer between the cathodeand anode (namely shuttle effect) and the volume expansion of sulfur in the process of electrochemicalreduction are the key factor for the capacity reduce. And, the dendritic crystal being generated in anodebecomes the serious and potential safety hazard in Li-S battery. It is these shortcomings that limit theextensive use of the Li-S battery in the market.This paper simply introduces the working principle of Lithium-ion battery and Li-S battery, andsummarizes several cathode composite materials in Li-S battery, simply analyzes a variety of differentcarbon material served as a loading of sulfur. On the basis of comprehensive analyzing the advantages anddisadvantages of sulfur electrode, we adopt different carbon source and different template agents to preparecarbon materials with different and abundant pore structure. Specific conditions as follows:1.We prepare microporous carbon using water-soluble phenolic resin as carbon source which issynthesized by ourselves and amphiphilic surfactant as soft template. The results show that pore sizedistributions of as-prepared carbon materials is focused on nearly2nm. When the quality of F127is1.0gand maximum carbonization temperature is900oC, the special surface area and pore volume of theobtained carbon material are638m2/g and0.321cm3/g. With50%sulfur loading, this C/S compositedelivers superior perfouance at0.2C than0.1C: a general initial specific capacity795.6mAh/g, a stablecapacity of470mAh/g and447.6mAh/g after50and70cycles respectively. At the same time, thecoulombic efficiency is97.2%.When the quality of F127is0.5g and maximum carbonization temperatureis900oC, the special surface area and pore volume of the obtained carbon material ain incease to838m2/gand0.415cm3/g. With50%sulfur loading, the C/S composite delivers a general initial specific capacity 848.5mAh/g and a stable capacity of540mAh/g after50cycles at0.1C. At the same time, the coulombicefficiency is99.7%.2. Ordered mesoporous carbon is prepared using water-soluble phenolic resin as carbon sourceand amphiphilic surfactant as soft template. In the process of preparing FDU-15, curing temperature of theprecursor is adjust to160oC, the ordered structure has better electrochemical performance. Also, we addPVP to adjust the pore size distributions at a curing temperature of100oC. The electrochemicalperformance of C/S composite with different sulfur loading is tested. The results show that the bestelectrochemical is received with the mass ratio being1:0.5. The specific capacity is stable at506mAh/gafter80cycles at0.2C and sulfur loading of40%. At the same time, the coulombic efficiency is98.8%.When sulfur loading increase to50%, the specific capacity is stable at560mAh/g after80cycles at0.1C.3.Finally, we prepare hierarchy porous carbon material using PAN as carbon source, PMMAand nano ZnO particles as sacrifice temple. After the exchange of DMF and water by phase inversion, lotsof micropores are formed in the PAN-PMMA mixture. The micropore carbon is got after carbonization. Thequality of hard template and maximum carbonization temperature is tested. The structure parameter andelectrochemical performance is characterized. The results show that the best additive amount of hardtemplate is2g. With sulfur loading of40%, the cycle performance of battery is best. This C/S compositedelivers a general initial specific capacity1596.2mAh/g and a stable capacity of701mAh/g after50cyclesat0.1C. |
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