The Application Of Electrospun CNFs@MoSe₂ And FeSe@CNFs Electrocatalysts In Lithium-Sulfur Batteries

With the progress of society,the demand for energy is increasingly urgent,and the current energy storage system has gradually been unable to meet the needs of electronic devices in daily life.Lithium-sulfur batteries（LSBs）are considered as next-generation energy storage devices to replace Li-ion batteries due to their high theoretical energy density(2600 Wh kg^-1),abundant resource reserves,low cost-effectiveness,and environmental friendliness.However,the commercialization of lithium-sulfur batteries also faces many challenges,such as the dramatic volume change of cathode sulfur before and after the reaction,the insulating properties of reactants and products,and the shuttle effect caused by soluble polysulfides.Therefore,in this project,a highly conductive long-range carbon nanofiber network is used to couple the transition metal selenide with strong adsorption catalysis.An efficient electrocatalytic carrier is constructed for the cathode of the lithium-sulfur battery by adjusting the phase structure of the transition metal selenide,thereby eliminating the existing problems of sulfur electrodes and improving their electrochemical performance.The main research contents of this paper are as follows:1.Sophisticated efficient electrocatalysts are essential to remedy the shuttle effect and realize high-performance flexible lithium-sulfur（Li-S）batteries.Herein,an efficient 1T-Mo Se₂ electrocatalyst was reported to be constructed on carbon nanofibers（CNFs）via in situ transition of 2H-Mo Se₂ nanosheets into 1T-Mo Se₂.In the transition process,lithium ions act as a bridge to accurately grasp the association between the discharge cut-off voltage and the phase structure of 1T-Mo Se₂ and 2H-Mo Se₂ by integrating theoretical calculations and functional relationships.The functionalized sulfur host（CNFs/1T-Mo Se₂）presents high charge density,adsorption energy,and catalytic kinetics,and its based Li-S cells display remarkable capacity retention of 875.3 m Ah g^-1 after 500 cycles at 1 C,and a rate capability of 923.2 m Ah g^-1at 2 C.A predominate areal capacity of 8.71 m Ah cm^-2 can be obtained even at a high sulfur loading of 7.52 mg cm^-2.Moreover,the flexible pouch cell exhibits a decent performance.These findings will endow a promising potential for CNFs/1T-Mo Se₂and similar materials in energy storage field.2.The construction of inexpensive,abundant and efficient electrocatalysts by phase engineering is necessary to realize the commercialization of high-performance lithium-sulfur batteries.Herein,an efficient biphasic h/t-Fe Se electrocatalyst coupled with carbon nanofibers（h/t-Fe Se@CNFs）was used as the sulfur host for Li-S batteries.Specifically,h-Fe Se and t-Fe Se are stably combined to construct a heterophase junction electrocatalysts through phase engineering,which not only exerts the comprehensive advantages of highly adsorptive h-Fe Se with conducting t-Fe Se,but also realizes accelerated charge transfer,thereby catalyzing the capture/conversion of sulfur species and inhibiting the shuttle effect of polysulfides.Thus,the h/t-Fe Se@CNFs cells delivers remarkable capacity retention of 619.4 m Ah g^-1 with an average capacity decay per lap of only 0.043%after 500 cycles at 2 C.Moreover,h/t-Fe Se@CNFs mats exhibit the marvel flexibility and assembled soft pouch cell shows a decent performance.The heterophase junction engineering idea in this work will offer new inspiration for developing efficient electrocatalysts for lithium-sulfur batteries.