Structure Design And Electrochemical Performance Of Mo S₂-based Cathode Material For Magnesium-ion Battery

In recent years,with the rapid development of global electronic information and new energy vehicle industry,LIBs will be more and more difficult to meet the increasing energy density requirements in practical applications.MIBs have attracted worldwide attention due to high energy density,low cost,high safety and environmental protection.However,due to its bivalent nature and strong solvation of Mg²⁺,the diffusion of Mg²⁺in cathode materials is difficult and the kinetic is poor,which leads to low reversible capacity and output power of MIBs.Therefore,the lack of suitable cathode materials restricts the further development of MIBs.In this paper,aiming at the problems of poor conductivity,limited interlayer spacing and poor structural stability of MoS₂,the composite materials with different microstructures were designed by using different surfactants to improve its electrochemical performance as the cathode material of MIBs.The main contents of this paper are as follows:1.We prepared a layered nanotube MoS₂@C by solvothermal intercalation of octylamine,which structure was composed of overlapping MoS₂layers and octylamine layers.In the solvothermal reaction process,the octylamine molecules were successfully intercalated into the MoS₂layers,and the overlapping between the MoS₂layers and the octylamine layers forms a layered nanotube structure.This structure builds an ideal interface contact,and makes the MoS₂@C layer distance expand to 1.02 nm,thus improving the conductivity of the material In addition,the hollow structure and layered structure of the nanotubes decreases the diffusion distance of Mg²⁺.The APC electrolyte system was selected and MoS₂@C was used as MIBs cathode material to test the performance of electrochemical magnesium storage.The MoS₂@C cathode exhibits an initial discharge specific capacity of 154.1 m Ah g^-1（69%of the theoretical specific capacity of MoS₂）at current densities of 20 m A g^-1,which is 36 times higher than MoS₂(4.3 m Ah g^-1).2.MoS₂@PEG with three-dimensional porous nano spherical structure was synthesized by hydrothermal method.Through the phase analysis of MoS₂@PEG,it is found that the introduction of PEG makes the composite have a three-dimensional porous nanosphere structure assembled by ultra-thin nanosheets.This structure not only enhances the structural stability of the material but also provides abundant defects,active sites and improved conductivity.In addition,the intercalation of PEG into MoS₂layers enlarges the interlayer spacing to 0.98 nm.The APC electrolyte system was selected and MoS₂@PEG was used as MIBs cathode material to test the performance of electrochemical magnesium storage.The MoS₂@PEG cathode shows that the initial discharge specific capacity is low at current densities of 20 m A g^-1.But the reversible specific capacity is increased from 42.8 m Ah g^-1to 68.9 m Ah g^-1after a period of activation,and it can still maintain 91.7%of the maximum specific capacity at the end of the 80th cycle.At high current densities of 500 m A g^-1,the specific capacity is 22.1 m Ah g^-1.Compared with ordinary MoS₂,it has excellent cycle stability and rate performance.