Design Of Hierarchical Porous Two-Dimension Carbon Materials And Their Application In Li-S Battery

To pursue the clear and sustainable energy resource instead of the nonrenewable energy resource for people,such as fuel oil,electrochemical storage energy system has attracted widely.But,Li ion battery has not satisfy the need of developed rapidly market,due to the lower energy density.However,lithium-sulfur battery owning the ultrahigh theoretical special capacity?1675 mAh/g?and theoretical energy density?2600 Wh/kg?is thought to the most promising next-generation storage energy system.However,lithium-sulfur battery is not still commercialized,facing to fast capacity decay.For that,researchers explore many programs to trap the polysulfides within cathode.In our paper,we design the two-dimension carbon owning hierarchical pores to improve the electrochemical performance of lithium-sulfur battery.First,we adopt the low-cost sodium polyacrylate as raw material and then prepared hierarchical porous carbon nanosheets?HPCNS?owning high specific surface area.The porous structure can relieved the diffusion of polysulfides through physical trap,and reduced graphene oxide was utilized to coat carbon-sulfur composite.The oxygen-containing functional groups on the surface of reduced graphene oxide adsorbed chemically polysulfides,and further hindered the shuttle effect and reduced the capacity decay.Thus,HPCNS/S@RGO had the discharge capacity of 1074 mAh/g at first cycle at 1CSecond,we used the glucose and tripolycyanamide as carbon source and nitrogen source,sodium chloride as template and ferric nitrate as catalyst,and then prepared N-doped porous carbon nanosheet?N-CNS?.The LiS_xLi⁺---N bond can be formed between N-doped and polysulfides,restricting the diffusion of polysulfides from cathode toward electrolyte by chemical adsorption.Thus,compared with the CNS,N-CNS enhances effectively the electrochemical performance of lithium-sulfur battery.Finally,we prepared the porous carbon?PC?containing metallic oxide through one-step method of high temperature calcination.The metallic oxide,Mn₂O,is unstable extremely.But,it can exist steadily after coated by carbon.Adopting the Mn₂O-PC as the load sulfur host can utilize the polarity of metallic oxide to adsorb the polar polysulfides,and thus hinders shuttle effect,at the same time,the hierarchical porous can relieve the diffusion of polysulfides toward electrolyte and further reduce the loss of active material and improve its utilization rate.The prepared Mn₂O-PC laid the foundation for the commercialization of lithium-sulfur battery.