Praparation And Sodium Storage Performance Of Molybdenum Disulfide Based Nanomaterials

Due to the increasing demand for energy storage in electronic products and new energy vehicles in daily life,researchers are working to develop efficient,cheap and sustainable energy storage technologies.In the past few years,sodium-ion batteries have received great attention due to their low cost,abundant sodium resources,and similar electrochemical mechanism with lithium-ion batteries.However,since the radius of sodium ions is larger than that of lithium ions,the migration of ions and electrons inside the battery is slow.The lack of suitable anode materials is one of the main obstacles hindering the large-scale application of sodium ion batteries.Molybdenum disulfide(MoS₂)has attracted widespread attention due to its unique two-dimensional layered structure,high theoretical specific capacity,and two reaction mechanisms to store sodium ions together.However,due to poor electrical conductivity and structural stability,the capacity decays rapidly during cycling,and the development of molybdenum disulfide as an anode electrode material is limited.For these reasons,the thesis focuses on the preparation and modification of molybdenum disulfide nanomaterials,and analyzes the influence of its nanostructure,composite system and other factors on the electrochemical performance of sodium storage.The main work content and research results are as follows:1.The interconnected network structure of MoS₂ nanospheres and carbon nanotubes wovenwith each other is fabricated by one-step hydrothermal method.In this new type of composite material,the interconnected network structure helps to improve the contact between the active sites of the MoS₂ nanospheres,promote the rapid transfer of electrons,and improve the overall conductivity of the electrode;and the carbon-coated MoS₂ anospheres The tight bonding with carbon nanotubes and the porous nanostructure ffectively avoid aggregation,allowing the electrolyte to quickly penetrate the entire lectrode and slowing down the volume expansion during the cycle.In addition,MoS₂ anospheres composed of ultra-thin nanosheets with enlarged interlayer distance ccelerate the diffusion rate of sodium ions,which is conducive to rapid electrochemical inetics.When the composite material is used in the negative electrode of a sodium ion attery,it exhibits excellent rate performance and cycle performance.For example,at a urrent density of 1 A g^-1,the sodium storage specific capacity reaches 468 m A h g^-1;at current density of 5 A g^-1,the specific capacity of sodium storage reaches 340 m A h g^-1 after 1000 cycles,and the capacity retention rate reaches 100%.2.The MoS₂ hierarchical hollow nanotubes were prepared by the self-sacrificial template-olvothermal method.The tubular hierarchical structure composed of loosely packed anosheets provides a high specific surface area and a large number of active sites,which an effectively shorten the ion migration path and provide enough space to alleviate the impact of volume changes during charge and discharge.In addition,when this composite material is used in the anode electrode of a sodium ion battery,at different current densities of 0.1,0.2,0.5,1,2 and 5 A g^-1,it exhibits specific discharge capacity of 544,503,392,298,222 and 130 m A h g^-1,respectively.Through pseudocapacitance calculations,MoS₂ hierarchical hollow nanotubes have a high capacitance contribution when used as the anode electrode of sodium-ion batteries.At a scan rate of 1.0 m V s^-1,the capacitance contribution rate is as high as 98.1%.