Study On Controlled Synthesis And Electrochemical Sodium-ion Charge Storage Of Anode Materials For Sodium Ion Capacitors With High Energy And Power Density

The increasingly severe environment pollution and energy crisis promote the rapid development of renewable new energy systems,but renewable energy is generally limited by intermittent,regional,and unstable problems.Therefore,it is very important to develop energy storage technology that can effectively store the electricity generated by these renewable energy sources.Sodium ion capacitors(SICs),as a new type of low-cost energy storage device,combine the dual characteristics of high energy density of batteries and high power density of supercapacitors.SICs have great potential in the field of large-scale energy storage and have attracted much attention from researchers.However,the mismatch between the electrochemical reaction kinetics of positive and negative electrodes in SICs severely restricts the process of commercial application.In order to alleviate the mismatch between positive and negative kinetics,this paper developed anode materials with high reaction kinetics.The research contents are as follows:(1)In view of the scientific problems of MoS2 such as poor conductivity,huge expansion of volume and destruction of structure during the cycling process,the design concept of porous structure and the interlayer regulation is introduced to improve the rate performance and cycle stability of MoS2.Porous MoS2 and amorphous carbon hybrid material(MoS2@PDAC)is successfully synthesized by a thermal decomposition method with a template of home-made SiO2 spheres.The hybrid material shows a hierarchically porous structure,with pore size of around 200 nm and 10-100 nm,and the obtained 2H-MoS2 exhibits an enlarged d-spacing of 1.02 A.MoS2@PDAC delivers a high specific capacity of 484.3 mAh g-1 at 0.05 A g-1,and maintains a specific capacity of 222.6 mAh g-1 at 10 A g-1,showing a high retention of 46.0%.MoS2@PDAC exhibits no decay in specific capacity after 1000 cycles at 1 A g-1.MoS2@PDAC shows obvious pseudocapacitive characteristics from the analysis of the electrochemical measurements.Furthermore,based on these great properties of MoS2@PDAC,the SIC constructed with MoS2@PDAC as anode.PDPC as cathode and 1.0 M NaClO4 organic solution as electrolyte delivers an energy density as high as 115 Wh kg-1 and a power density up to 29.9 kW kg-1,as well as a capacity retention of 87.9%after 10000 cycles at 2 A g-1.proving the great cycling performance.(2)Considering the instability of structure and electrochemical properties resulted from the severe expansion during cycling process for Sb,this paper puts forward a facile thermal decomposition method to synthesize Sb@N-doped carbon hybrid material(Sb@NC).In order to improve the rate capability and cycling stability of Sb,Sb nanoparticles are homogeneously distributed in N-doped amorphous carbon matrix.According to the structural characterization,Sb@NC exhibits a specific nanoflower morphology,which is composed of wrinkles of continuous sheets.From the electrochemical measurements,Sb@NC electrode delivers a specific capacity of 331.5 mAh g-1 at 0.05 A g-1,and maintains a specific capacity of 96.4 mAh g-1 at 10 A g-1,showing a retention of 29.1%.After 1000 cycles at 1.0 A g-1,Sb@NC exhibits a capacity retention of 99.8%.The SIC assembled with Sb@NC as negative electrode,PDPC as positive electrode and 1.0 M NaClO4 organic solution as electrolyte exhibits a max energy density of 157 Wh kg-1 and power density of 25 kW kg-1.Moreover,the Sb@NC//PDPC SIC maintain 79.2%of the initial capacity after 4000 cycles at 2 A g-1.(3)High-crystallized In2S3 nanorods are obtained by innovatively vulcanizing the In-based MOF precursor.Structural characterizations indicate that these nanorods are piled up of well-crystallized In2S3 grains,exhibiting extraordinary sodium storage properties.In2S3 exhibits a high specific capacity of 556.0 mAh g-1 at 0.05 A g-1,and maintains a specific capacity of 375.8 mAh g-1 at 10 A g-1,showing a rate capability of 67.6%.In2S3 also exhibits a great cycling stability of a higher capacity than the initial value after 200 cycles at 0.2 A g-1,maintaining a nearly 100%coulombic efficiency at the same time.In2S3 electrode is further employed in SIC,the obtained SIC delivers a maximum energy density of 119.8 Wh kg-1 and a maximum power density of 13.0 kW kg-1,and also exhibits no obvious capacity decay after 2000 cycles.