Multi-dimensional Construction And Electrochemical Performance Of MoS₂ And Carbon Composite Materials

Two-dimensional?2D? nanomaterial molybdenum disulfide?MoS₂? has been attracted tremendous interests due to its electron energy state structure and excellent physical and chemical properties.Meanwhile,it has good mechanical performance and high packing densities.Moreover,the volume changes of MoS₂ can be restrained during the absorption and desorption of ion in the electrolyte.Besides,it is suitable for 2D layered MoS₂ to develop thin,flexible microsupercapacitors.However,there are two main challenging issues on MoS₂ materials for supercapacitors.One is that the poor electrical conductivity of MoS₂ limits its further application in energy storage.The other is that 2D layered MoS₂ nanosheets are tend to restack and pulverize during ion absorption and desorption process,thus leading to fast capacity fading and poor cycling stability.To overcome these obstacles,various methods have been applied for MoS₂ to improve the electrochemical performance of MoS₂-based electrode materials,including copounding with good conductive materials and altering the electronic structure of 2D MoS₂ nanosheets.In this paper,MoS₂ nanosheet was grown vertically on carbon materials with different dimensionals to improve the electrochemical properties of MoS₂ composite and benefit to apply on supercapacitor.A MoS₂/CNT composite has been successfully synthesized by using MoO₃ and KSCN as reactants through a facile one-step hydrothermal method.The composite contains three-dimensional?3D?flower-like MoS₂ with 300 nm diameter and interconnected carbon nanotubes?CNTs?.The 3D MoS₂ composite was assembled by MoS₂ nanosheets and was interconnected by 1D CNT.The special capacity of the MoS₂/CNT composite can reach 74.05F/g at a high current density of 2A/g,which is higher than those of the flower-like MoS₂ and MoS₂ nanosheets at the same current density.Furthermore,the specific capacitance of the MoS₂/CNT composite still maintains 80.8% of initial capacitance over 1000 cycles at the current density of 2A/g.The excellent electrochemical performance and long cycle life of the MoS₂/CNT composite are attributed to the synergetic effect between CNTs and ultrathin MoS₂ nanosheets grown vertically on the flower-like MoS₂.A nanocomposite containing three-dimensional?3D? flower-like MoS₂ nanosheets and two-dimensional?2D?interconnected surface functional carbon nanosheets is prepared by a facile hydrothermal method.The hierarchical porous carbon nanosheets were prepared with potassium citrates using high temperature solide state method and were treated by HNO₃ with oxygen-containing functional group increasing wettability.The results indicated that the carbon nanosheet can restrain the growth of ?002? plane and it can also provide more active sites on the surface of carbon nanosheet.The ion diffusion and transmission enhance the power density of materials.The MoS₂/C composite ?MC-2? exhibits the highest specific capacitance of 381 F/g at the current density of 1A/g,as well as superior cyclic stability with 92% capacitance retention over 3000 cycles.The nanocomposite with 6wt% carbon nanosheets are beneficial to inhabit the restacking of MoS₂ nanosheets and form curved MoS₂ nanosheets,which are grown along the vertical orientation on carbon nanosheets.The curved MoS₂ nanosheets could provide more suitable ion transport channels.The carbon nanosheets can enhance the electronic conductivity and keep the integrity of the nanocomposites.The excellent electrochemical performance of MC-2 as supercapacitor electrode is attributed to the 3D/2D structure and the heterojunction between MoS₂ nanosheets and carbon nanosheets.Yolk-shell structure with internal void space in materials for long-cycle life energy storage devices has been attracted wide attention.Carbon-MoS₂?yolk-shell? hierarchical microspheres were successfully prepared by glucose and bulk MoO₃ without any hard template and surfactant using one-step hydrothermal method.The carbon-MoS₂?yolk-shell? microsphere was obviously constructed with carbon yolk and MoS₂ shell,which are 2.1?m in diameter and 0.26?m in thickness,respectively.The results demonstrated that the bulk MoO₃ as precursor is beneficial to synthesize MoS₂ microspheres with the higher crystallinity than MoO₃ microbelt.When evaluated as electrode materials for supercapacitor,the as-prepared carbon-MoS₂ yolk-shell hierarchical microspheres displayed charge capacity of 120 F/g after 3000charge and discharge cycles at the current density of 1 A/g.The superior electrochemical performance of the as-prepared materials can be attributed to the yolk-shell structure and smart combination between carbon and MoS₂.The yolk-shell structure has sufficient void space for volume expansion without causing the MoS₂ shells to be destroyed,thus leading to stable structure and cycling.At last,the possible formation mechanism of the carbon-MoS₂ yolk-shell microsphere was discussed according to the molecular imbalanced diffusion.The MoS₂ composites?3D flower-like and 2D nanosheet? with different phase,shapes,size and good interface on the different carbon materials?2D carbon nanosheet and 1D carbon nanotube? have been prepared using simple hydrothermal methods.The electrochemical performance of MoS₂ was strongly enhanced by smart combination with carbon forming multi-dimensional structure composites.Furthermore,the heterojunction between carbon and MoS₂ nanosheets validly restrict the volume change during charge and discharge,maintaining the structure stability of the materials.