| With the rapid growth of the world economy,the society is increasingly worried about energy shortage and climate change.Therefore,the development of efficient and renewable clean energy is becoming more and more important.However,at present,the performance of lithium ion battery?LIBs?,which can be used as a device for converting chemical energy and electric energy,is far from meeting the actual needs.Therefore,it is urgent to develop high-performance electrode materials for LIBs.Transition metal oxides have attracted extensive attention due to their advantages of high specific capacity and easy mass production.However,the low electronic conductivity and large volume variations of transition metal oxides hinder their applications.Metal organic framework?MOFs?is a new kind of porous material,which is composed of metal ions and organic ligands.The derivatives of MOFs can well solve the drawbacks of the transition metal oxide as the cathode material of lithium ion battery.Therefore,this paper takes MOFs as the research object and focuses on the following three parts:how to design it as a one-dimensional nano-material and apply it to the cathode of lithium ion battery.?1?FeMnOx/CNT with one-dimensional structure was prepared by solvothermal method using carbon nanotubes as template and ferromanganese bimetallic MOF as the precursor.The effects of carbon nanotubes on the morphology and structure of the composites were discussed.The morphology and electrochemical properties of FeMnOx/CNT with different carbon nanotubes contents were tested.It was found that when the carbon nanotubes were added at 80 mg,the composite had a good one-dimensional morphology.Ferromanganese oxide had a uniform coating on the surface of carbon nanotubes,and had the best electrochemical properties.When the current density is 0.1A g-1,the first discharge capacity of the composite is 1313.8 mAh g-1.After 100 cycles of charging and discharging,the capacity of the composite can still maintain 1107.5 mAh g-1.The stability and capacity of the composite material are greatly improved compared with that of the single material before the composite.?2?To avoid the loss of lithium storage capacity caused by the addition of polymer binder and carbon black,we prepared self-supporting nitrogen-doped carbon-coated CoO nanowire array?CoO@N-C/NF?composites.The one-dimensional CoO nanowire array grown on a nickel foam substrate was used as a self-sacrificial template to grow the CoO@ZIF-67 nanowire arrays.Finally,the target material was obtained by pyrolysis.The electrochemical properties of CoO powder,CoO/NF and CoO@N-C/NF were compared,and it was found that CoO@N-C/NF had excellent electrochemical properties.The initial discharge specific capacity of the material under the current density of 1 A g-1 was 2015.2mAh g-1.After 100 cycles,the discharge specific capacity remained at 1884.1 mAh g-1.At the same time,the electrode material has excellent rate performance,when the current density is 5A g-1,its discharge specific capacity is up to 1169.2 mAh g-1.The results show that the nanowire arrays structure and carbon coated can improve the performance of self-supporting oxide electrode materials.?3?In this work,Ni-Co hydroxide of bimetal was prepared on the basis of growing ZIF-67 by displacement method,and the target product of NiO/NiCo2O4 composite nanoarrays was obtained through further pyrolysis.When the time for 30 min with nickel nitrate replacement of ZIF-67 to get the target product reached our expected results and has excellent electrochemical performance,under the current density of 1 A g-1 after 100 cycles,the discharge specific capacity remains in 983.5 mAh g-1,at the same time,when the current density of 0.5 A g-1,1 A g-1,2 A g-11 and 5 A g-1,average discharge specific capacity,in turn,968.7,862.7,805.1,715 mAh g-1.This indicates that the unique hierarchical structure of the target material and the synergy between polymetallic oxides play an important role in the capacity improvement. |
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