The Application Of Two-dimensional Transition Metal Sulfide And Selenide In Lithium-Sulfur Battery

Li-S batteries have been considered as promising next-generation storage devices due to their high energy density(2600 Wh Kg-1)and high specific capacity(1675 mA h g-1).As the cathode-active material of the batteries,sulfur has advantages of low cost,nontoxicity,and environmental friendliness.Because a series of formidable problems arise during the working process of sulfur electrode,the utilization rate of active sulfur is low,which seriously impedes the commercial application of lithium-sulfur battery.Transition metal dichalcogenides(TMDs)have a wide range of applications in energy storage and energy conversion due to their unique electrical properties and controllability of band gap and crystal phases.In this paper,the potential application of TMDs in lithium-sulfur system is studied.The effects of TMDs on the performance of lithium-sulfur batteries are studied by using MOS2 modified rGO as the sulfur host material and MoSe2 as the separator coatings.The detail contents and results are as follows:1.MoS2 nanosheets were decorated on the surface of rGO by hydrothermal method to obtain a three-dimensional sponge structure of MoS2/rGO serving as the sulfur host material,while the MoS2/rGO/S composite was prepared by melt diffusion method.MoS2/rGO has a high specific surface area and is rich in micropores and mesopores,which can physically limit the loss of sulfur and buffer the volume of sulfur.The polar MoS2 enhances the chemical adsorption of rGO on lithium polysulfide,accelerates the conversion of lithium polysulfide.The performance of the batteries was significantly improved.The cells constructed with the MoS2/rGO/S cathodes exhibit a high reversible capacity of 1100 mA h g-1 at 0,2 C,an outstanding cycling stability with a low capacity fading rate of 0.15%after 300 cycles at 1C,and an excellent rate performance up to 620 mA h g-1 at 2 C.2.A self-assembled MoSe2 nanotube containing 1T phase was prepared by solvothermal method,and MoSe2 was coated on a Celgard separator serving as a lithium-sulfur battery separator.The MOSe2 coating not only physically alleviates the shuttle of polysulfide,but promotes the conversion of sulfur element in the low voltage discharge platform and improves the discharge capacity of the sulfur electrode.After optimization,a MoSe2-AB/Celgard separator with a good conductivity was prepared.When a pure sulfur electrode was used as the positive electrode,the capacity of the battery with MoSe2-AB/Celgard separator retains at 510 mA h g-1 after 100 cycled at 0.2 C rate.