Preparation And Properties Of Metal Sulfide@Graphene Sodium Ion Battery Anode Material

With the depletion of fossil fuels and the growing demand for energy,the importance of developing new energy storage technology has increased dramatically.Sodium ion battery is regarded as an ideal supporting power source for major applications such as smart phones and electric vehicles in the future due to a series of advantages such as rich and widely distributed sodium,low price.It is also an important direction for the development of new energy storage technology.At present,the focus of the development of sodium ion battery is to develop suitable sodium storage materials.Among them,the anode material is the main factor to promote the commercialization of sodium ion battery.Metal sulfide has good thermal stability,physical stability and suitable redox potential,so it is a good anode material for sodium storage.However,due to its poor electrical conductivity and serious volume changes during sodium storage,metallic sulfides exhibit poor performance of sodium storage rate and circulation,so it is necessary to be modified.In this paper,metal sulfide was modified by means of nanostructure design and reduction of graphene oxide modification.Three kinds of composite materials,E-1T-MoS2@rGO-6,SnS2@MoS2@rGO and Sb@InSbS3@rGO were prepared,and their sodium storage properties and mechanism were discussed in detail.The main contents were as follows:1T phase reinforced MoS2@rGO nano-spherical composites(E-1T-MoS2@rGO-6)were prepared via adding urea and reducing the reaction time(6 h).When the current density was 0.1 A g-1,the composite still had a reversible capacity of 450 mAh g-1 after 60 constant current charging cycles.When the current density was increased to 1 A g-1,it showed a reversible capacity of 280 mAh g-1 after 100 cycles.The high sodium storage capacity,good rate performance and cycling performance of E-1T-MoS2@rGO-6 were not only attributed to the existence of rGO,but also closely related to the increase of 1T metallic phase content in MoS2.These two modification methods can effectively alleviate the huge volume change phenomenon of the material in the process of charging and discharging,and can also provide a wealth of active sites,so as to improve the electrochemical performance of MoS2.SnS2 nanoparticles were loaded on the surface of MoS2@rGO to construct the SnS2@MoS2@rGO sodium ion anode material with heterojunction.The modification of SnS2 nanoparticles can effectively improve the specific surface area of the composites,which was conducive to the occurrence of sodium storage behavior by pseudocapacitance and improve the kinetics of sodium storage.When the current densities were 3.2 and 6.4 A g-1,the reversible specific capacities after 140 cycles were 167 and 237 mAh g-1,respectively.In addition,SnS2@MoS2@rGO anode and Na3V2(PO4)3@C cathode material were assembled into a complete battery for testing.When the current density was 20 C(1 C=117 mA g-1),the capacity was maintained at 33 mAh g-1.The ideal specific capacity showed the potential application prospect of SnS2@MoS2@rGO sodium ion anode material.The lamellar Sb@InSbS3 composite was successfully loaded on the surface of rGO(Sb@InSbS3@rGO)by pyridine coordination and ion exchange method.Using Sb@InSbS3@rGO as the anode material of sodium ion battery,it showed high reversible capacity,excellent cycling performance and magnification performance.When the current density was 0.1 A g-1,the reversible capacity remained 445 mAh g-1 after 200 cycles.When the current density was increased to 2 A g-1,the reversible capacity remained 212 mAh g-1 after 1200 cycles.When the current density was increased to 6.4 A g-1,the reversible capacity was still 210 mAh g'1.The excellent electrochemical performance of Sb@InSbS3@rGO anode material was closely related to its unique lamellar structure,which can not only effectively shorten the transport path of sodium ions and electrons,but also provide a larger specific surface area,improve the contribution rate of pseudocapacity,and improve the kinetics of sodium storage.In summary,three kinds of composite metal sulfide materials were prepared by hydrothermal method and applied to the anode of sodium ion battery.Through the electrochemical test,the three kinds of composites showed good electrochemical properties.In addition,the influence of the crystal type,structure and composite mode of the material on the electrochemical performance of sodium ion battery was summarized,and the mechanism of sodium storage of metal sulfide was deeply explored,which provided a certain reference for the development of metal sulfide into the anode of sodium ion battery.