Preparation Of Porous Carbon-based Materials By Al/Zn-MOF And Its Application In Lithium-sulfur Batteries

In recent years,in the research of secondary batteries,lithium-sulfur batteries are still receiving much attention.However,suitable porous materials remain the best solution in the selection of many sulfur positive carrier materials.In this thesis,the metal aluminum/zinc organic framework materials(Al/Zn-MOF)are used as research objects.Multi-walled carbon nanotubes@aluminum metal organic framework carbon-based,potassium hydroxide-activated carbon-based,reduced graphene oxide@metal-organic framework carbon-based composite materials with multrole and pore structure are prepared by in-situ recombination,high-temperature carbonization,KOH high-temperature activation,etc.Then,the composite carbon-based materials are melt-permeated with sublimed sulfur at 155? to prepare a composite sulfur cathode material.And systematically studied their structural characteristics and electrochemical properties.The main contents of this paper are as follows:1.Multi-walled carbon nanotubes@aluminum metal-organic framework carbon-based(MWCNT@Al-COF)composites with porous structure were prepared by hydrothermal synthesis and high-temperature carbonization,and then Multi-walled carbon nanotubes@aluminum metal organic framework carbon-based/sulfur(MWCNT@Al-COF/S)composite cathode material was prepared by liquid phase melt permeation.Tests have shown that when the porous composite is loaded with up to 50%of the elemental sulfur particles,the sulfur particles embedded in the porous material are present in a highly dispersed state.The specific discharge capacities after the first and first hundred cycles at 0.5 C are 698.7 mAh g-1 and 424 mAh g-1,and the coulombic efficiency of each cycle is 98%or more.2.The paper studied the above multi-walled carbon nanotubes@aluminum metal organic framework carbon-based(MVCNT@Al-COF)materials which were treated with sodium hydroxide solution(NaOH)and hydrochloric acid solution(HCl)respectively,and then activated with potassium hydroxide solids to prepare potassium hydroxide activated carbon-base(AMWCNT@COF-NaOH,AMWCNT@COF-HCl)comosite.It has been found that the KOH-treated AMWCNT@COF-NaOH composite exhibits more microporous and mesoporous structures with a specific surface area of up to 1608.74 m2 g-1.Under the load theoretical sulfur content of 70%,the first and first hundred discharge specific capacities of potassium hydroxide activated carbon/sulfur(AMWCNT@COF-NaOH/S)at 0.5 C are 797.8 mAh g-1 and 650.4 mAh g-1.It shows a good capacity retention rate(81.52%).3.The reduced graphene oxide@metal organic framework carbon-based(rGO@Zn-COF)composite was prepared by hydrothermal synthesis and high temperature carbonization.The specific surface area is 1562.84 m2 g-1,and the microporous and mesoporous structures are abundant.The prepared porous carbon-based composite material is capable of loading a theoretical sulfur content of up to 60%.The specific discharge capacities after the first and first hundred cycles at 0.5 C are 852.2 mAh g-1 and 650.2 mAh g-1.