Preparation And Study Of Porous Electrode Materials For Lithium-and Sodium-ion Secondary Batteries

Compared with traditional secondary batteries such as lead-acid,nickel-cadmium,nickel-metal hydride batteries,Lithium ion batteries(LIBs)have many advantages of high energy density,long lifespan,high efficiency and low self-discharge rate,no memory effect,environmental benignity.So it has been widely applied in eneygy storge and conversion field.On the basis of abundant resources and cheap prices,sodium ion batteries have gradually received attention from researchers and enterprises.As a very important component part in Li/Na-ion batteries,electrode materials largely determine the electrochemical performance of the batteries.Generally,capacity degradation and poor cycling life result from the large volume shrinkage/expansion of electrode materials,especially for sodium batteries.In order to overcome this barrel,many efforts have been made to fabricate special structure or novel composite,including constructing nanostructure or porous structure,doping and compositing with carbon materials etc.Among them,the porous structure can not only buffer the large volume expansion of electrode materials during repeated cycling process,but also increase the surface area between electrode and electrolyte as well as facile the ion migration.Therefore,in this work,various kinds of porous metal oxides or sulfides have been successfully synthesized by using Metal-organic frameworks as precursor.Hollow cupric oxide(CuO)spheres are successfully prepared via annealing HKUST-1;Carbon coated copper sulfides nanosheets,denoted as C@Cru1.96S,are successfully prepared via directly annealing Metal-Organic Framework(MOFs)and commercial sulfur powder;Graphene@nitrogen doped carbon@ultrafine TiO2 nanoparticles(G-NC@TiO2)with porous structure are obtained through annealing the precursor of graphene oxide/MOFs for the first time.The chemical component and microstructure of as-synthesized products were further characterised.The superior electrochemical performance of electrode materials in this paper has been verified through contrast experiments.The main research contents are listed as following:(1)MOF-derived hollow cupric oxide(MOF-CuO)spheres were synthesized by utilizing solvothermal synthetic HKUST-1 as a precursor,followed by temperature programmed pyrolysis.As novel anode materials for sodium ion batteries,the as-prepared CuO delivers high initial reversible capacity of 612 mAh g-1 and good capacity retention of 83%after 50 cycles with superior rate capability.Furthermore,The fitted results of EIS show that the sodium ion transfer of MOF-CuO are enhanced compared with commercial Nano-CuO.(2)Carbon coated copper sulfides nanosheets(C@Cui.96S)are successfully prepared via directly annealing Metal-Organic Framework(HKUST-1)and commercial sulfur powder in nitrogen atmosphere.Based on the N2 adsorption/desorption isotherms of C@Cu1.96S,the BET surface area value is calculated to be about 121 m2 g-1 As cathode materials for lithium batteries,the as-prepared C@Cu1.96S nanosheets deliver high reversible capacity,good capacity retention and superior rate capability.(3)Graphene@nitrogen doped carbon@ultrafine TiO2 nanoparticles(G-NC@TiO2)with porous structure are obtained through annealing the precursor of graphene oxide/MOFs,of which NC@TiO2 is in a special shuttle shape.On the one hand,the unique structure of electrode materials buffer the large volume expansion and facile the Na-ion diffusion.On the other hand,The wrapping of graphene and N-doped carbon coating could effectively improve the electronic conductivity.Electrochemical performance analysis indicates that the G-NC@TiO2 composite can deliver an excellent capacity retention of 93%even after 5000 cycles and a superior rate capability.