Preparation Of Cathode Of Sulfur/Carbon Aerogel With Samarium Yttrium And Its Electrochemical Performance For Lithium Sulfur Batteries

Lithium sulfur batteries have attracted increasing attention as one of the most promising candidates of rechargeable batteries for the high theoretical capacity(1675 mAh g-1)and high energy density(2600 Wh kg-1)of sulfur cathode.However,there are still a number of obstacles to overcome in practical applications,such as the insulating nature of sulfur,the large volume expansion of sulfur cathode and "shuttle effect" from polysulfide dissolution,diffusion.The carbon aerogel with porous structure and carbon aerogel with Sm2O3 and Y2O3 modified as sulfur cathode matrix were successfully synthesized by using catalyst of organic acids,in-situ method and sulfur melt-diffusion methods,respectively.We systematically investigated the surface morphology,structure and the surface area of composites,the adsorption abilities of samples on polysulfides and the electrochemical performance of the above materials based sulfur cathodes.The results show that the prepared CAs with in-situ method present crosslinking and porous structure,effectively increasing the surface area of materials.And this feature is beneficial to store sulfur and restrain polysulfides,resulting in high rate capability and cycling stability.It can be found from SEM and TEM that the CA with Sm2O3 and Y2O3 modif-ication exhibits distinctive porous structure and uniform dispersion of metal oxide.It can help absorb soluble polysulfides and further improve the electrochemical performance.In particular,the cathode of Sm2-CA/S achieved a high initial discharge capacity of 1347 mAh g-1 and retains 1090 mAh g-1 after 100 cycles at 0.2 C.The electrode still delivers high initial discharge capacity of 976 mAh g-1 even at high current rate of 2 C.The Sm2-CANS cathode exhibited a nice long-term cycling stability with a high initial discharge capacity of 1175 mAh g-1 and maintained 861 mAh g-1 after 300 cycles at 0.5C.Furthermore,the Y2O3 modified CA can enhance electronic conductivity and effectively trap soluble polysulfides.The designed Y2-CA/S cathode exhibits a high initial discharge capacity of 1369 mAh g-1 and still retained 1108 mAh g-1 after 100 cycles at 0.2 C.The Y2-CA/S electrode presents high nitial discharge capacity of 1246 mAh g-1 and remains a reversible capacity of 892 mAh g-1 after 300 cycles at 0.5 C.