Construction Of Lithium-sulfur Battery Composite Cathode System Based On Mxene And Electrospinning And Its Electrochemical Performance

Lithium-sulfur?Li-S?batteries are based on the redox reaction of elemental sulfur with lithium metal.Because of their high energy density,environmental friendliness,and low cost,they have attracted widespread attention from researchers.However,apart from these advantages,the commercialization process of Li-S batteries is still limited by some of its shortcomings,such as rapid capacity decay,low utilization of sulfur,and low full-cell energy density.In order to solve these above issues,based on the inherent problems of poor conductivity of elemental sulfur and lithium sulfide,volume expansion effects during cycling process,and the shuttle effect of lithium polysulfide.Through the chemical regulation and the rationalized electrode structure design,the cathode system suitable for Li-S batteries was constructed,and the electrochemical performance of Li-S batteries was successfully improved.The main research contents of this article are summarized as follows:1.The various proportion of MXene-PAN composite fibers?M-PAN?were prepared by electrostatic spinning,and then Ti O₂-MXene heterojunction composite fibers?TM-CNFs?were prepared by utilizing the characteristics of MXene self-oxidation at high temperature.In addition,TM-CNFs composite fibers have a strong affinity for polar species,which can effectively restrict the shuttle effect,and the unique fibers interweaving structure can preferably alleviate the effects of volume expansion effects.Thus,the Li-S cells with flexible TM-CNFs host demonstrate cycle stability(870.2 m Ah g^-1 at 0.5 C after 200 cycles)and excellent rate performance(807.3 m Ah g^-1at 5 C),and high areal capacity and energy density(initial specific capacity10.85m Ah cm^-2 with 10.5 mg cm^-2).2.We propose a“Three regions”strategy to fabricate an integration cathode for Li-S batteries,and through different structural designs,the integration methods that can provide the best performance are screened out.The elemental sulfur is combined with graphene?GS?and used as a sulfur source region;Ti N nanocrystalline composite carbon fibers?TN-CNFs?were preparation by electrospinning as the Li PS adsorption and Li₂S precipitate region;subsequently,MXene was self-assembled on the surface of TN-CNFs to form a barrier layer for Li PS shuttling effect,and finally an integrated structure of MXene/TN-CNFs/GS was formed.The Ti N nanocrystalline endows the carbon-based composite nanofibers robust affinity with polar species,and the Li PS permeation measurements show the M/TN-CNFs possessing excellent blocking effect for the diffusion of Li PS.Therefore,the“Three regions”integration cathode can perform the excellent electrochemical performance(717.7 m Ah g^-1 at 1 C after 500cycles),and under high loading conditions(10 mg cm^-2),still maintain high cycle stability(7.3 m Ah cm^-2 at 0.05 C after 100 cycles).