Fabrication Of 3D Nanostructures Based On Two Dimensional Nanoshakes As Advanced Electrode For High-efficient Energy Storage

Since the 21st century,the problem of energy and environmental have become increasingly prominent,and the development of clean energy has attracted more and more attention.New energy storage method is an urgent problem to be addressed.As new energy storage devices,lithium ion battery and supercapacitor are considered to be promising due to their high energy density,large reversible specific capacity,long cycle life,no memory effect,security,environment protection and so on.Electrode materials are the most critical parts of the lithium ion battery and supercapacitor,and they are the pivotal factors to determine the performance of the devices.Therefore,the preparation of high performance electrode materials has become a hot research object.Two dimensional nanosheets not only shows great potential applications in catalysis,sensing,energy storage and other fields,but also is the basic unit for assembling and constructing new three-dimensional materials.Through the reasonable design and controllable preparation of these two-dimensional nanosheets,three-dimensional nanomaterials with specific structures can be constructed.The main purpose of this thesis is to assemble two-dimensional nanoscale into three dimensional structure and apply it in the field of energy storage.The main contents of this article are as follows:（1）CoS₂ nanodots trapped within the graphitic structured N-doped carbon spheres with efficient performances for lithium storage.Cobalt sulfide（CoS₂）-based nanomaterials are promising electrode materials for various energy storage and conversion due to their large specific capacities and catalytic activity.However,the CoS₂-based nanomaterials are still suffering from their volume expansion,agglomeration and poor cycling stability.Here,we demonstrated an intriguing and effective strategy to confine CoS₂ nanodots（（27）10 nm）within the graphitic carbon walls of the porous N-doping carbon spheres（CoS₂-in-wall-NCSs）,which both avoid the volume change and facilitate the promotion of reaction kinetics in lithium ion batteries（LIBs）.Moreover,the N-doping carbon spheres（NCSs）with nest-like architectures and graphitic carbon nanoribbons offer ideal diffusion highway for electrolyte ions and high rapid for electrons transfer pathway.As a results,the CoS₂-in-wall-NCSs still exhibits an excellent LIBs’performance with a high specific capacity of 1080.6 mAh g^-1 at a current density of 200 mA g^-1 even after 500 cycles,which is much better than that of CoS₂ nanoparticles in the pores of N-doping carbon spheres,metallic Co NPs embedded in N-doping carbon spheres,and NCSs.Even at a current density as high as 1000 mA g^-1,a reversible capacity of 735.5 mAh g^-1 is obtained in CoS₂-in-wall-NCSs.It is believed that the intriguing structure can be further extended to the preparation of many other kinds of metal/metal sulfides containing N-doping carbon spheres for wide applications including energy storage and catalysis.（2）2D MOF nanoflake-assembled spherical microstructures for enhanced supercapacitor performances.Herein,we demonstrate an intriguing solvothermal method to realize nanostructure engineering to achieving the structures of MOFs with an interesting 2D MOFs nanoflakes assembled hollow structure with Ni/Co-and Ni-MOF for their electrochemical performances optimization in supercapacitor and oxygen reduction reactions（ORR）.As a result,the Ni/Co-MOF nanoflakes exhibit remarkably enhanced performances with a specific capacitance of 530.4 F g^-1 at 0.5 A g^-1 in 1 M LiOH aqueous solution,much higher than that of Ni-MOF(306.8 F g^-1)and ZIF-67(168.3 F g^-1),a good rate capability and a robust cycling performance with no capacity fading even after 2000 cycles.Besides,Ni/Co-MOF nanoflakes also show promoted electrocatalytic performance for ORR when compared with Ni-MOF and ZIF-67.The present work highlighted the significant role of tuning 2D nanosheets ensembles of Ni/Co-MOF in accelerating electron and charge transportation for optimizing energy storage and conversion devices.（3）1D Cu（OH）₂ nanorod/2D SnO₂ nanosheets core/shell structured array:covering with graphene layer leads to excellent performances on lithium-ion battery.In this work,we fabrication of three-dimensional（3D）nanoarchitecture of graphene（G）/tin oxide（SnO₂）nanosheets/Cu（OH）₂ nanorods arrays directly grown on Copper（Cu）foil（G/SnO₂/Cu（OH）₂/Cu foil）.Benefiting from this design of nanoarchitecture,the G/SnO₂/Cu（OH）₂/Cu foil electrode displays high discharge capacity of 1057.1 mAh g^-1 was achieved after 50 cycles at a current density of 200 mA g^-1,much better than the samples without graphene(512.6 mAh g^-1)cover and Cu（OH）₂ nanorod(117.4 mAh g^-1),even after 500 cycles at 200 mA g^-1,the G/SnO₂/Cu（OH）₂/Cu foil electrode can still maintain 1057.1 mAh g^-1.Furthermore,the G/SnO₂/Cu（OH）₂/Cu foil electrode demonstrated superior rate performance with a discharge capacity of 600.8 mAh g^-1 at a high rate of 1000 mA g^-1.This work highlights that increasing surface and interface effects with desirable three dimensional nanoarchitecture can open a new avenue to electrochemical performance improvement in lithium-ion battery for SnO₂-base anode.