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Study On The Preparation And Properties Of MnO2 And Its Composites For Supercapacitors

Posted on:2013-12-31Degree:MasterType:Thesis
Country:ChinaCandidate:F Q ZhouFull Text:PDF
GTID:2232330362960614Subject:Materials science
Abstract/Summary:PDF Full Text Request
Supercapacitors have great potential in electric vehicles and renewable energy production fields for its high power density. Manganese oxide is an ideal supercapacitor electrode material, which is rich in natural resources, cheap and high theoretical capacity. In this paper, hydrothermal methord was used to fabricate–MnO2 with high specific capacity. Nano-carbon materials and metal oxides were introduced in situ to improve the conductivity ofδ–MnO2.KMnO4 and MnSO4 were used as raw materials to fabricateδ–MnO2 by hydrothemal methord at 160°C. Different crystal structures and morphologies of MnO2 were prepared by adjusting the molar ratio of two raw materials, such as–MnO2 flower-like particles formed at the ratio of 6:1, and the–MnO2 nanofibers andγ–MnO2 fiber bundles formed at the ratio of 2:3 and 1:3 respectively.–MnO2 pocessed the better electrochemical performance with the specific capacity of 162 F/g at 1 A/g by galvanostatic charge–discharge measurement, much higher than that of–MnO2 (62 F/g)andβ–MnO2 (8 F/g). The high specific capacity of–MnO2 may be attributed to its layered crystal structure not only make the electrolyte ion adsorption and desorption on the electrode surface to store electric charge, but also make prolapse cation embed in the crystal layer which greatly increased the electrode charge storage.δ–MnO2 and nano-carbon composites were synthesized by in situ hydrothermal method. The morphology ofδ–MnO2 was changed because of inducing nano-carbon materials. For example, treated multi-walled carbon nanotubes changed the flower-likeδ–MnO2 particals to solid particals with the specific capacity of 156 F/g at 1 A/g, multi-walled carbon nanotubes increased the size of flower-like particals with the specific capacity of 163 F/g at 1 A/g, graphite oxide addition produced a sheet-like–MnO2 with the specific capacity of 170 F/g at 1 A/g.δ–MnO2-based binary metal oxides were synthesized by in situ hydrothermal method, such as K0.27MnFe0.17O1.9, K0.24MnCo0.05O1.1, K0.16MnLa0.14O1.4 and K0.27MnSn0.15O1.55. The specific capacity of these binary metal oxides were 163 F/g、146 F/g、139 F/g and 154 F/g at 1 A/g, respectively. The impedance ofδ–MnO2 was reduced from 1.7Ωto 1.3Ωby inducing a second metal oxide.
Keywords/Search Tags:Supercapacitor, MnO2, Nano-carbon materials, Binary metal oxide
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