Construction Of Binary Metal Selenides/Carbon Composites Based On MOFs And The Investigation Of Lithium Storage Properties

The tremendous growth of fossil fuel consumption and energy demand leading to environmental pollution and other problems,as well as the vigorous development of the electric vehicle industry in recent years,renewable clean energy storage devices represented by rechargeable lithium-ion batteries have been widely studied.Among many anode materials,transition metal selenides(TMSs)possess immense potential to be a kind of energy storage materials due to their higher conductivity and higher theoretical capacity than the corresponding transition metal oxides/sulfides.However,the TMSs anodes based on conversion reaction suffer from the outstanding problem of volume expansion during the repeating charge/discharge process,resulting in terrible cycling stability and rate performance.Current research suggests that the introduction of carbon materials and the development of new metal selenides/carbon nanomaterials composites can effectively overcome this problem.Metal-organic frameworks(MOFs)are a kind of crystalline porous materials constructed by inorganic metal ion centers and organic ligands.What's more,the organic ligands can derive porous carbon materials with high conductivity by high temperature calcination.In this paper,the bimetallic organic frameworks was prepared by simple hydrothermal synthesis and precipitation method,which was used as the precursor to construct binary metal selenide/carbon anode materials.Lithium storage performance has been obviously improved by increasing the electronic conductivity as well as mitigating the volume expansion attracted by the intercalation and deintercalation of lithium ion at the same time.The primary research contents are as follows:(1)Dodecahedron Zn-Co-MOF was prepared by hydrothermal synthesis method,on which dopamine hydrochloride(DPH)was further introduced as an additional carbon source.The Zn Se/Co Se and carbon composites were successfully fabricated by using ZIF-8@ZIF-67 and ZIF-8@ZIF-67@DPH as precursor through reacting with seleniumpowder in high temperature Ar atmosphere,respectively.The results show that Zn Se/Co Se/NC with DPH has better electrochemical performance.Zn Se/Co Se/NC electrodes deliver an initial discharge capacity as high as 1616.6 m Ah g-1 at the current density of 0.1 A g-1,and the reversible capacity maintains at 1214.2 m Ah g-1after 100cycles;the reversible capacity maintains at 404.5 m Ah g-1 after 1000 cycles at 1 A g-1;and also achieve the specific capacity of 503.7 m Ah g-1 even at a big current density of2.5 A g-1.(2)Tetrahedral Ni-Co PBA was obtained by simple precipitation method.Ni Se2/Co Se2/C composites were successfully synthesized by using Ni-Co PBA as precursor through reacting with selenium powder in high temperature Ar atmosphere.The electrochemical performance of the as-prepared materials at different calcination temperatures were investigated.The results reveal that the Ni Co Se-350 prepared at 350 oC shows preferable cycle performance and rate performance.Ni Co Se-350 electrodes display the reversible capacities of 695.3 m Ah g-1 and 425.3 m Ah g-1 after 200 and 800 cycles at 0.1 A g-1 and 1 A g-1,respectively.