Preparation And Properties Of MoS_xSe_2-x

In the context of China’s energy transformation and the"dual carbon"strategy,the proportion of new energy power generation,such as photovoltaic,wind power,is increasing.However,the sun sets in the morning,and the wind is sometimes absent.The force of nature has natural volatility and intermittence,and it is unpredictable how much power can be converted into.Therefore,it will cause the imbalance of power supply and demand and the unstable operation of the power grid,so it is more and more urgent to develop a feasible energy storage device.Electrochemical energy storage is considered as an efficient energy storage technology because of its high energy conversion efficiency,relatively compact volume and fast response speed.In recent years,since sodium ion batteries（SIBs）have the same reaction mechanism and treatment procedure as the corresponding lithium ion batteries,they are considered to be very promising energy storage systems.Their high energy density and low cost are the advantages of energy storage power supply.In addition,the content of sodium in the crust is higher than that of lithium,which is a key factor in developing new battery systems.However,due to the large radius of sodium ions,it is still a great challenge to select materials suitable for sodium ion storage.MoS₂has proper layer spacing and high theoretical specific capacity,which attracts people’s attention in the negative electrode of sodium ion battery.However,due to its low conductivity,and the huge expansion during the insertion and removal of sodium ions,which leads to capacity attenuation,its large-scale application is limited.In this thesis,the electrochemical study of selenium doped MoS₂ was carried out,and on this basis,CNT/MoS_xSe_2-x composites were prepared,the properties of the composites were explored,and the effect of in situ carbon content on the properties of CNT/MoSSe composites was studied.（1）In this thesis,flower like MoS_xSe_2-x was prepared by solvothermal method.Selenium ion doping into molybdenum disulfide can improve conductivity,expand interlayer spacing,provide good support and buffer,and obtain high-performance sodium ion storage materials.Based on the advantages of the above structure,the prepared MoSSe electrode material has a specific discharge capacity of 605.9 m Ah g^-1in the first cycle at a current density of 0.1 A g^-1,and a capacity retention value of383.6 m Ah g^-1after 40 cycles,which shows good cycle performance.（2）CNT/MoS_xSe_2-x composites were prepared by compounding carbon nanotubes with MoS_xSe_2-x using carbon nanotubes as the carbon source.The carbon nanotube MoS_xSe_2-x composites showed better electrochemical performance due to their synergistic effect.Among them,the specific discharge capacity of CNT/MoSSe is 721.4 m Ah g^-1 at the current density of 0.1 A g^-1 in the first cycle,and it still maintains 565.2 m Ah g^-1 after 40 cycles,and has good magnification performance.The introduction of sodium into carbon nanotubes provides an excellent insertion channel and location.（3）The effect of in-situ carbon content on the performance of CNT/MoSSe composites was investigated.The carbon derived from glucose can ensure good contact between the main chain of carbon nanotubes and MoSSe,and form a good conductive network.As the carbon content increases to 10 wt%,the electrochemical performance increases.When the carbon content is 10 wt%,the specific discharge capacity of CNT/MoSSe/C at the current density of 0.1 A g^-1 in the first cycle is 810.2m Ah g^-1,and the capacity remains 603.9 m Ah g^-1 after 40 cycles.