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Synthesis And Electrochemical Performance Study Of Net-work Sulfur-Carbon Composite

Posted on:2016-10-29Degree:MasterType:Thesis
Country:ChinaCandidate:X T LingFull Text:PDF
GTID:2191330479995484Subject:Applied Chemistry
Abstract/Summary:PDF Full Text Request
With the rapid development of electronic products and electric tools, the next generation of rechargeable battery need higher discharge capacity and energy density. Lithium-Sulfur battery as a source of high energy density storage(2600 Wh·Kg-1) and duration of the electric vehicle electric equipment are attracting more and more attention. Sulfur have the advantages of low cost, environment friendly, and high reserve capacity on earth. However, sulfur is different with other conventional intercalation cathode material, non-conducting, and suffer composition and structure changed through circulation process, which including soluble polysulfides, insoluble sulfides and volume expansion. These problems would cause losing of active materials, and eventually leading to severe attenuation of cyclic capacity.This paper reviews the progress of research and new characteristics of cathode materials for lithium/sulfur battery, improving the cathode materials current defects as the purpose of this study, prepare new sulfur/carbon composites materials, and research the microstructure and electrochemical performance. The details summarized as follows:(1) We use a one-step hydrothermal method successful synthesis of three-dimensional porous graphene aerogels/sulfur nanocrystals, and studied the hydrothermal reaction condition to graphene/sulfur composite electrochemical performance. We take XRD, SEM, TEM and XPS techniques to research the composite materials characterization, use battery testing system and electrochemical workstation to study the electrochemical performace of cathode materials, and discussed the relationship of oxygen-containing functional groups of graphene with sulfur nanoparticles and microstructure of composite materials to electrochemical performance. As a result, the oxygen-containing functional groups on graphene surface play the role of good electrochemical performance, the GA-S-180 sample exhibit outstanding performance of 716.2 m Ah·g-1 after 50 cycles at a current density of 100 m Ah·g-1 and even at high current density still have excellent discharge specific capacity.(2) We prepared a double-shelled structure of sulfur@PANI@GO materials by in situ polymerization and electrostatic attraction. First, PANI would growing on sulfur particles surface by in situ polymerization, and S@PANI, graphene oxide form a coating structure through electrostatic attraction, get S@PANI@GO composite material with double-shelled structure. Through the characterization and analysis of composites microstructure, sulfur contenting and electrochemical performance to investigate the effect of double-shelled structure to electrochemical performance. The results show that the S@PANI@GO composites with good coating structure, PANI could improve the conductivity of the inner layer, graphene have excellent chemical stability. As the cathode material for Li-S battery, a retain capacity of 842.7 m Ah·g-1 over 50 cycles have been achieved, and delivered a discharge capacity of 694.7 and 380.4 m Ah·g-1 at large discharge currents of 500 and 1000 m A·g-1 respectively.(3) We use the functionalization carbon fiber cloth(CFC) as skeleton, wet-chemical method obtained CFC-OS composite material. Through FTIR, SEM, XPS and electrochemical performance analysis, we studied the electrochemical performance of cathode material of CFC-S and CFC-OS. The results showed that a large number of oxygen-containing functional groups on the carbon fiber colth sheet after chemical modification, sulfur with the oxygen-containing functional groups formed covalent bond at hydrothermal process, effectively inhibit the polysulfide transport to electrolyte which would cause the loss of active materials, a retain capacity of 968.1 m Ah·g-1 over 50 cycles have been achieved, which have good cyclic performance and potential application prospect.
Keywords/Search Tags:lithium-sulfur battery, carbon/sulfur composites, graphene, doubled-shelled structure, carbon fiber cloth
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