The Preparation Of Three Dimensional Porous Carbon Materials As Cathode Of Lithuim-sulfur Batteries

Lithium-sulfur?Li-S?batteries are deemed to be the next generation second batteries for its high theoretical specific capacity(sulfur cathode 1675 mAh·g^-1)and the energy density(2600 Wh·kg^-1).However,the electrical insulation of sulfur,the“shuttle effect”,and the volume expansion problem of cathode result in unsatisfied performance of Li-S batteries.To improve the performance of Li-S batteries,three dimensional?3D?porous carbon materials were synthesized using sucrose and sodium citrate,two type of cheap and abundant carbon sources.Electrical performance of Li-S batteries was studied.The main results and conclusions are followed:1.This paper used sucrose as carbon sources,SiO₂ as templates and FeCl₃ as pore former to prepare 3D porous carbon materials PCCF.The effect of SiO₂ and FeCl₃ on the 3D porous carbon structure and the effect of carbon structure on the electrochemical performance of Li-S batteries were studied.We found that SiO₂ templates could facilitate the formation of cellular structure,FeCl₃ could facilitate the formation of micropores.Synergistic action of SiO₂ and FeCl₃ induced the formation of 3D porous carbon with hierarchical structure,which contributed to an excellent cathode performance.PCCF/S cathode showed high initial discharge capacity of 1108.5 mAh·g^-1,and maintain a capacity of 917.2 mAh·g^-1 after 100 cycles?17%capacity decay?.When the sulfur loading was 6.4 mg·cm^-2,PCCF/S showed high initial capacity of 1162.3mAh·g^-1 and good cycle stability.2.This paper used sodium citrate as carbon sources,melamine as nitrogen sources to prepare N-doped 3D porous carbon materials.The effect of carbonized temperature and the ratio of melamine on the carbon structure were studied,as well as the influence of carbon structure on the performance of Li-S batteries.The results showed that the addition of melamine could changing the structure and morphology of carbon materials by influencing the formation of the intermediate product,Na₂CO₃.An appropriate amount of melamine could result in the formation of 3D porous carbon with high surface specific area and hierarchical pore structure.With the carbonized temperature increased,the surface specific area increased and the nitrogen content decreased.When the carbonized temperature is 800 ^oC,N-doped 3D porous carbon materials,with a high specific surface area of 2224.04 m²·g^-1 and nitrogen content being 4.67%showed the best electrochemical performance.When sulfur loading was 4.5 mg·cm^-2 a 0.1 C rate.Capacity of 916.5 mAh·g^-1 was maintained after 50 cycles.