Preparation Of Sulfur Cathode Material Of Carbon Aerogel Controlled Via Perylene Derivative And Electrochemical Performance For Lithium Sulfur Batteries

Lithium sulfur?Li-S?battery has attracted more and more attention because of its high energy density(2600 Wh kg^-1),high theoretical capacity(1675 mAh g^-1)of sulfur electrode and the remarkable advantages of low cost,naturally rich and non-toxic for sulfur elements.Li-S battery is expected to become one of the most promising candidates.However,there are still some difficulties,such as the shuttle effect caused by polysulfide dissolved in the electrolyte during the electrochemical cycling,which leads to poor cycling performance and serious capacity degradation;the low conductivity of sulfur and low-order polysulfide leads to low utilization of active materials.All of these obstacles seriously limit the practical application of lithium sulfur battery.In this paper,we develop a new strategy.The cadmium-doped carbon aerogel was successfully prepared via microtemplate inducing strategy and subsequent high temperature carbonization.Forming the spherical carbon aerogel with uniform and interconnected porous structure.The as-prepared materials display the large specific surface area and excellent conductivity.The loaded sulfur composites as cathode materials exhibit high discharge capacity and excellent cycling performance.Particularly,the designed P2-Cd-CA/S electrode with sulfur of 78.9 wt%presents an initial discharge capacity of 1318 mAh g^-1 at 0.2 C.And it delivers an initial discharge capacity of 1189 mAh g^-1 at 0.5 C and still maintains 871 mAh g^-1 after 300 cycles.The enhanced performance is mainly attributed to the synergistic effect of microtemplate and CdO that the inductive graphitization of microtemplate?3,4,9,10-perylenetetracarboxylic dianhydride?and the stronger anchoring to polysulfides of evenly distributed cadmium.Furthermore,the first-principles theoretical calculations further support the strong adsorption role between CdO and polysulfides and affirmatively verify the immobilizing mechanism.Zinc-doped carbon aerogels?Zn-CA?were successfully prepared by sol-gel reaction and carbonization process via using Zn-PTCA as a template.The addition of Zn-PTCA can effectively control the structure of carbon aerogels and realize the strong anchoring effect of ZnO to polysulfide.In addition,the Zn-PEG-CA composites were obtained by using polyethylene glycol?PEG?to modify the Zn-CA.Zn-PEG-CA composites have abundant crosslinking channels and can accommodate more active materials.Zn-CA/S and Zn-PEG-CA/S electrodes display excellent electrochemical performance.Particularly,the initial specific capacity of Zn-PEG-CA/S with 79.6 wt%sulfur loading reaches 1209 mAh g^-1 at 0.2 C.The cathode shows the initial capacity of 1075mAh g^-1 at 0.5 C and remains 72.2%after 300 cycles.The crosslinking channels in carbon aerogels are increased and the adsorption capacity to polysulfide are improved.These improvements were mainly attributed to the regulation effect of PEG and the double action of Zn-PTCA that template inducing strategy and strong adsorption of ZnO to polysulfide.