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Preparation Of Composite Materials Based On ZIF-67-derived Carbon And Its Application In Lithium-sulfur Batteries

Posted on:2024-02-15Degree:MasterType:Thesis
Country:ChinaCandidate:H Y ZhangFull Text:PDF
GTID:2531307139956939Subject:Physics
Abstract/Summary:PDF Full Text Request
Lithium-sulfur batteries stand out among energy storage systems due to their excellent theoretical specific capacity(1675 m Ah g-1)and theoretical energy density(2600 Wh kg-1).However,due to the low conductivity of sulfur itself and the volume change caused by the reaction,the“shuttle effect”of intermediate products and other problems,the actual performance of the battery is greatly affected.Therefore,in this paper,based on the metal-organic framework(ZIF-67)material,conductive polymer polyaniline(PANI),transition metal oxides(V2O3),carbon materials(MWCNTs)were introduced to design a new three-dimensional sulfur carrier,and its electrochemical performance was studied.The main research contents and results are as follows:1.The three-dimensional conductive network structure(3CPC),which was crosslinked by nitrogen-doped carbon skeleton(NC)and polyaniline fiber(PANI),was prepared by solvent method and in-situ polymerization method.The cathode electrode material(3CPC@S)was obtained by melting and penetrating sulfur into3CPC.The effect of the three-dimensional conductive network structure and interface bonding on the electrochemical performance of the positive cathode material was studied.The results show that the specific initial discharge capacity of 3CPC@S electrode is 1220.1 m Ah g-1,and the capacity retention rate is 83.5%after 100 cycles at 0.1C current density.The results show that the elastic space of the microporous/mesoporous structure of 3CPC three-dimensional porous network helps to localize sulfur and cushion the volume change of sulfur production.NC and PANI interface bonding crosslinking effectively improve the electron transport characteristics of 3CPC@S composite cathode electrode.2.Three-dimensional V2O3 Hollow spheres prepared by hydrothermal method,and Co-MOFs(ZIF-67)was grown in-situ on the surface of V2O3 spheres.After high temperature annealing,stable nitrogen doped carbon coated bound hollow sphere structure(NC-Co@V2O3)was formed as the sulfur storage carrier of lithium sulfur battery.The cathode electrode material(NC-Co@V2O3@S)is obtained by melting sulfur into NC-Co@V2O3.The results show that NC-Co@V2O3@S has an initial discharge capacity of 851.8 m Ah g-1 at 0.2C,reversible capacity of 584.5 m Ah g-1after 200 cycles.The results show that the three-dimensional spherical structure of NC-Co@V2O3 effectively binds lithium polysulfide and alleviates the volume expansion of sulfur.The NC-Co coating significantly improved the stability of the structure and the conductivity of the material,and significantly improved the electrochemical performance of the battery.3.ZIF-67 nanoparticles were grown on acid-treated multi-walled carbon nanotubes(MWCNTs)by in-situ growth method.After high temperature annealing,MWCNTs and NC-Co scaffolds were grafted to form a stable three-dimensional conductive network(NC-Co@MWCNTs).The positive electrode material(NC-Co@MWCNTs@S)is obtained by melting and penetrating sulfur.The results show that the average discharge specific capacity of NC-Co@MWCNTs@S cathode at 0.1,0.2,0.5and 1C was 1072.3,837.2,669.1 and 503.7 m Ah g-1,respectively.When the current density is switched back to 0.1C,the capacity is restored to 864.7 m Ah g-1.The results show that the three-dimensional conductive network can provide an effective space for the volume expansion of the electrode and provide an effective charge transfer pathway,Co nanoparticles promote the REDOX kinetics of active sulfur during the cycle.
Keywords/Search Tags:ZIF-67 derived carbon, PANI, V2O3, Lithium-sulfur battery, Cathode material
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