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The Design?Preparation And Lithium Storage Properties Of Carbon Composites Based On MOFs

Posted on:2018-10-18Degree:MasterType:Thesis
Country:ChinaCandidate:M HuangFull Text:PDF
GTID:2321330536477513Subject:Applied Chemistry
Abstract/Summary:PDF Full Text Request
With energy and environment problems becoming more and more serious,the exploitation of energy storage electronics with high energy density,long cycle life,high safety coefficient have attracted much interest for scholars in all over the world.Compared with traditional graphite,carbon nanomaterials have been becoming more and more popular in the field of energy storage battery because of their excellent conductivity,good mechanical properties,unique morphology and structure characteristics.Based on the above advantages,metal organic framework?MOF?was used as template to prepare porous carbon composite materials and explored their lithium storage performance as electrode materials for lithium ion batteries and lithium sulfur batteries.The related works are shown as follows:1.ZIF8@ZIF67 core-shell structures have been synthesized by solvothermal method.After annealing the ZIF8@ZIF67 precursor at 800 ?,bi-metal embedded N-doped carbon polyhedral nanocages have been acquired.The results clearly displayed that Co and Zn particles are uniformly dispersed in the carbon matrix.When it was used as anodes for LIBs,the corresponding initial discharge capacity was 809 mA h g-1and after 400 cycles,the final capacity could still remain at 702 mA h g-1 at a current density of 0.2 A g-1.Furthermore,a reversible capacity of 444 mA h g-1 was obtained at a much higher current density of 2 A g-1.The improved electrochemical performance could be attributed to the synergistic effect of Zn ? Co and the unique porous hollow structure as well as N doping,which relieved the impact of volume changes,maintained perfect electrical conductivity throughout the electrode and enhanced the electrochemical activities of lithium storage.2.A flexible method was used to synthesize carbon materials with suitable N content,good conductivity and high surface area and used them as sulfur host.Based on the above advantages,the electrochemical performance of Li-S battery has been improved signally.It is initially inferred that the related excellent electrochemical performance was not only attributed to the suitable N-doped level,but also was related with the high surface are of carbon matrix.When sulfur loading is 55 wt%,the discharge capacity could still remain at 600 mA h g-1 for over 400 cycles with nearly 100% coulombic efficiency at the current density of 800 mA g-1.It was proved that the N-doped carbon materials can be a promising host for Li-S batteries.3.ZIF8@ZIF67 composites were used as the precursor and then mixed with ammonium dihydrogen phosphate under the different mass ratio.After heating,carbon materials with yolk-shell structure were obtained.When it was used as sulfur host for Li-S battery.The final discharge capacity could remain at 600 mA h g-1 after 400 cycles at the current density of 800 mA h g-1.
Keywords/Search Tags:ZIF-8, ZIF8@ZIF67, N-doped carbon composite, Lithium ion battery, Lithium-sulfur battery
PDF Full Text Request
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