Preparation Of Sulfur Cathode Material Of Carbon Aerogel Modified With Metal Compound And Electrochemical Performance For Lithium Sulfur Batteries

Lithium-sulfur battery?Li-S?attracts more and more attention with its high energy density(2600 wh kg^-1)and sulfur electrode rich,cheap,non-toxic and high theoretical capacity(1675 mAh g^-1).It is expected to become the development direction of the next generation lithium battery.However,there are still several inherent issues to be overcome:the insulating properties of sulfur and lower-order polysulfides?Li₂S and Li₂S₂?,large volumetric expansion during the reaction process and the“shuttle effect”caused by diffusion back and forth of these soluble polysufides.These problems have seriously hindered the commercial development of lithium-sulfur batteries.In this paper,nitrogen doped carbon aerogel?NCA?,Cr₂O₃ modified carbon aerogel?Cr-CA?and WO₃ modified N-doped aerogel?WNCA?composite materials were successfully prepared by in situ sol-gel method and hydrothermal method,respectively.These materials were used as the carbon-based carrier of sulfur element to prepare composite sulfur electrode materials for lithium-sulfur batteries.The elemental composition and morphology of the materials were analyzed by means of XRD,SEM,TEM,XPS and TG.A series of electrochemical tests were used to study the effects of N-doping and metal oxide modification on the electrochemical performance of sulfur electrodes.The results show,the Cr₂O₃ doping remarkably controls structure,decreases carbonsphere size and promotes network interconnect.The nano Cr-CA composites with large pore volume and high specific surface present stronger adsorption ability and effectively immobilize polysulfides.The Cr-CA/S composite cathodes display excellent electrochemical performance with high specific capacity and long cycling stability.Especially,the Cr2-CA/S cathode delivers initial specific capacity of 1343and 987 mAh g^-1 at the rate of 0.2 C and 2 C,respectively.It exhibits the outstanding long-term cyclic stability with the discharge capacity of 873 mAh g^-1 at 0.5 C for the300th cycle.The excellent performance is mainly attributed to special anchoring role of Cr₂O₃ to polysulfides and its catalytic effect for redox reaction process.The N-doped carbon spheres are more uniform in size and form a 3D internet-like structure.Moreover,in situ nitrogen doping introduces abundant defects and active sites for polysulfide adsorption.The synergistic effect of the WO₃ and the doped N atom significantly enhances the chemical affinity with the polysulfide and effectively anchors the polysulfide.Therefore,the composite exhibits excellent electrochemical performance with high specific capacity and cycle stability.The WNCA/S composite cathode can achieve a high discharge capacity of 1204 mAh g^-11 at 0.2 C.The capacity decay rate per cycle was only 0.094%after a cycle of 300 cycles at 0.5 C.