Preparation Of Carbon-Sulfur Electrode Modified With Amide-Containing Group And Electrochemical Performance Of Lithium-Sulfur Battery

Lithium-sulfur batteries have the energy density of up to 2600 Wh kg^-1 and the theoretical specific capacity of sulfur electrode can reach 1675 m Ah g^-1.At the same time,sulfur has the advantages of abundant reserves,low cost,environmental friendliness and non-toxicity,so researchers around the world have pay much attention to it.In this paper,amide-containing materials were used as templates to prepare carbon materials with specific structures.The prepared carbon materials would be able to load more elemental sulfur,effectively inhibit the"shuttle effect",and significantly improve the electrochemical performance of lithium sulfur battery.The novel net channel and N-doping carbon aerogel was successfully prepared by in situ and facile method via polyimide inducting for lithium sulfur battery.The polyimidedirecting carbon aerogel?PI-CA?presents a cross-linked framework,abundant porous and high specific surface area.PI-CA spheres present effective immobilizing polysulfides and high loading sulfur for BET surface area of 2039.4 m² g^-1 and N-doping via physical and chemical adsorption.The Li-S batteries with PI-CA as cathode matrix exhibit excel ent performance.Especially,the initial specific capacity of 2PI-CA/S with sulfur content of 73.8 wt%reaches 1338 m Ah g^-1,and remains 1102 m Ah g^-1 after 100cycles at 0.2 C.The enhanced electrochemical performance mainly benefit from the mesh structure of the composite and the interaction between nitrogen and lithium polysulfide.The theoretical calculation by density functional theory?DFT?further supports the template effect of polyimide and anchoring mechanism of polysulfides.By using the linear structure of polyimide and amide groups,and cobalt nitrate hexahydrate,isophthalic acid as raw material and the polyimide-cobalt metal ligand?PI-Co?was prepared by the hydrothermal reaction.Then the carbon-sulfur positive composites?PI-Co CA/S?were prepared by using PI-Co as template.This composite material inherits the structure of PI-Co perfectly,leaving a continuous pore channel in the carbonized carbon aerogel and forming cobalt metal doping in the carbon matrix,further improving the conductivity of the carbon-sulfur composite material and anchoring the polysulfides.The sulfur load of PI-Co CA/S composite reaches 76.5%.Especially,the initial specific capacity of 2PI-Co CA/S electrode delivers 1227 m Ah g^-1,and remains1059 m Ah g^-1 after 100 cycles at 0.2 C.