Design And Electrochemical Performance Of Carbon-based Materials For Lithium Sulfur Batteries

Lithium–sulfur(Li–S)batteries are regarded as one of the most promising technologies for commercial applications in battery energy storage devices owing to their high energy density,naturally rich sulfur,high economic efficiency and environmental protection.However,some key issues still need to be solved during the commercialization of lithium–sulfur batteries:the shuttle effect of polysulfides(Li PSs)and slow conversion process between Li PSs and Li₂S₂/Li₂S.Physical and chemical limitations help anchor Li PSs to a certain extent,but these cannot fundamentally eliminate the shuttle effect.Hence,this paper uses high–conductivity biomass carbon as the base material,and then introduces polar materials that chemically interact with Li PSs intermediates to accelerate the conversion kinetics between Li PSs and the final product(Li₂S₂/Li₂S)to minimize the shuttle effect.The details are as follows:(1)Conductive and porous carbon as the growth matrix material of 1T MoS₂were obtained from plane tree fruit fluff.1T MoS₂@C composite were synthesized by solvothermal method.1T MoS₂nanosheets are uniformly oriented and anchored on the porous C substrate.1T MoS₂@C/S cathode was successfully prepared by melting method.The results of X–ray photoelectron spectroscopy show that the oxygen–containing functional groups in porous carbon can provide selective growth sites for 1T MoS₂.There is a C–O–Mo bond between porous C and molybdenum disulfide.Electrochemical tests and adsorption results show that1T MoS₂@C can effectively adsorb Li PSs.Therefore,the 1T MoS₂@C/S electrode showed an initial specific capacity of 1090 mAh g^-1at 0.2 C and a capacity of about 775 mAh g^-1after being cycled 300 times at 1 C.(2)C@Ti₃C₂T_xcomposites prepared by electrostatic self–assembly method as sulfur hosts for advanced lithium–sulfur batteries.The morphology test,transmission electron microscope and X–ray diffraction results show that porous C can effectively inhibit the aggregation of Ti₃C₂T_xnanosheets.X–ray photoelectron spectroscopy analysis shows that Ti–S bond is formed between C@Ti₃C₂T_xand S by chemical interaction.In summary,the constructed C@Ti₃C₂T_x/S electrode has a high initial reversible specific capacity of 1001mAh g^-1at 0.2 C.A reversible specific capacity of 589 mAh g^-1was obtained after the 400 cycles at 1 C.