Preparation And Peformance Of Metal Selenides For Sodium Storage

Due to the advantages of safety,environmental friendliness and low cost,sodium-based electrochemical energy storage devices represented by sodium-ion batteries,sodium-double ion batteries and sodium-ion capacitors are becoming a new generation of energy storage systems,which have attracted extensive attention of researchers.However,because of larger radius of sodium-ions and slower ion diffusion kinetics,reversible charge/discharge capacity,cycle and rate performance of sodium-based electrochemical energy storage devices are still far from practical.In the research of sodium based electrochemical energy storage devices,anode materials become the focus of researchers.Because of abundant resources and high theoretical capacity,transition metal dichalcogenides?TMDCs?have great application potential in the anode of sodium-based electrochemical energy storage devices.It is found that MoSe₂ can exhibit good electrochemical performance as the anode electrode material.On the other hand,due to its unique structure and component effect,bimetallic selenides MnSnSe₂ exhibits good sodium storage performance.However,TMDCs materials usually have the disadvantages of large volume change and poor cyclic stability,which seriously affects their comprehensive energy storage performance as the anode materials of sodium-based electrochemical energy storage devices.In this paper,we intend to improve sodium storage performance of the MoSe₂ and MnSnSe₂as anode materials of sodium ion energy storage devices via morphology and structure regulation as well as carbon modification.The main results are as follows:?1?Yolk-shell spheres constructed of ultrathin MoSe₂ nanosheets?MoSe₂ YSs?were synthesized by the treatment of Mo–glycerate?Mo G?solid spheres via thermal annealing and selenide.Since MoSe₂ nanosheets have ultrathin characteristics and expanded interlayer spacing,as anode materials for sodium ion batteries,MoSe₂ YSs not only have good reaction kinetics and high pseudocapacitance-controlled sodium storage capacity,but also provide an effective buffer for the volume change during the process of Na⁺insertion/extraction.The sodium dual ion battery?S-DIBs?assembled with MoSe₂ YSs as the anode and expanded graphite as the cathode has a specific discharge capacity of 70.1 m A h g^-1after 120 cycles at the current density of 0.2 A g^-1.Even if the current density increases to 2.0 A g^-1,the S-DIBs still has good rate performance,with a discharge capacity of 42.9 m A h g^-1 and a coulomb efficiency of over 93.5%.The results show that the MoSe₂ YSs with unique structural characteristics have great application in the anode materials of sodium ion electrochemical energy storage devices.?2?MnSnSe₂ and carbon-coated MnSnSe₂?MnSnSe₂@C?were prepared by high temperature annealing using MnSn?OH?₆ nanocubes as the precursor.The MnSnSe₂@C material shows good sodium storage performance due to the unique nanocube heterostructure and carbon coating.The electrochemical performance tests showed that the MnSnSe₂@C material with a nominal carbon content of 20%has an initial discharge specific capacity of 641 m A h g^-1 at the current density of 0.1 A g^-1,and maintains a capacity of 230 m A h g^-1 after 100 cycles.The preliminary results show that the MnSnSe₂@C material is a potential anode material for sodium ion electrochemical energy storage device.