Research Of Cathode Materials And Gel Electrolytes For Novel Lithium Sulfur Battery

The dissolution of lithium polysulfides in liquid electrolyte(LE)is one of the biggest problems which could reduce the cycling performance and impede successful commercialization of lithium sulfur batteries.To solve this problem,in this paper,cathode materials and functional gel polymer electrolyte(GPE)were prepared and applied in the lithium sulfur battery to improve the electrochemical performance.(1)The highly uniformed hybrid carbon material has been prepared by in-situ growth carbon nanotubes(CNTs)from metal organic frameworks,with the cobalt species as the catalyst for CNTs growth and dicyandiamide(DICY)as a sacrificial agent for the formation of graphitic carbon.The CNTs with extraordinary conductivity supply more electron transport to the cathode and make much more sense in enhancing the rate performance of the sulfur cathode.In the matrix,cobalt nanoparticles and heteroatom nitrogen can help in immobilizing sulfur species,leading to the improvement of polysulfide shutting.Moreover,the increased specific surface area and mesoporous channel enhance the sulfur loading and facilitate electrolyte diffusion.On integrating these fascinating benefits into one electrode material,as a result,the hybrid composite cathode presents a high initial capacity of 1316.1mAh g~-11 at the current rate of 0.1 C.Even at high current rate of 5 C,a decent capacity of620.7 mAh g~-11 can still be achieved.The capacity of hybrids materials can be maintained at970 mAh g~-11 after 500 cycles at 0.2 C,and a capacity retention of 79.8%,revealing it great potential for energy storage application.(2)An effective,in-situ curing strategy was utilized for preparing functional gel polymer electrolyte in Li-S battery system.As functional monomers,pentaerythritol tetraacrylate(PETEA)and 2-hydroxyethyl acrylate(HEA)were copolymerized by an in-situ curing way with initiator 2,2-azobis(isobutyronitrile)to form a polymer matrix that growing in LE to take shape GPE.In the matrix,physical obstruction and chemical action between the hydroxyl of HEA and lithium polysulfides suppress the shuttle effect of polysulfides.As a result,sulfur cathode with functional GPE presents a high initial capacity of 1205.7 mAh g~-11 at the current rate of 0.1 C.And at high current rate of 2 C,a decent capacity of 429 mAh g~-11 can be achieved.The capacity can be maintained at 557.2 mAh g~-11 after 600 cycles at 0.5C,and capacity retention of 63.7%which is very promising for the use in rechargeable lithium sulfur batteries.