Synthesis and Characterization of Manganese Oxide Supercapacitors
| Autor: | Kuang-Tsin Lee, 李光正 |
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| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 For the first time, aqueous gel electrolytes have been successfully applied to the MnO2‧nH2O and MnFe2O4‧nH2O supercapacitors. Each gel polymer electrolyte consists of polymer, salt, and water. Potassium polyacrylic acid (PAAK), potassium polyacrylic acid-co-polyacrylamide (PAAK-co-PAAM), and polyacrylamide (PAAM) were used as polymers in the gel electrolytes. These gel electrolytes all show no fluidity, but they still main high ionic conductivities in the order of 10-1 Scm-1. The capacitances of two Mn-based oxides were all enhanced remarkably in gel polymer electrolytes compared to these in the liquid electrolytes. In-situ X-ray absorption near-edge structure (XANES) analysis indicates that the oxide electrodes of gel electrolyte cells possess higher Mn valances and are subjected to greater extent of valance variation than that of liquid electrolyte cell upon charging/discharging over the same potential range. On the other hand, for the MnO2 supercapacitor, the problem of capacitance reduction with increasing oxide loading can be solved to a great extent by introducing superabsorbent polymer, namely polyacrylic acid (PAA), to form new composite powders composed of MnO2, carbon black, and PAA. Besides, the capacitance of oxide in the composite electrode is also much higher than that of the original electrode. The success in combining both high capacitance and high active-material loading results in geometric capacitance density (GCD) of ca. 1.8-1.4 F cm-2 even under very high current densities (ca. 35-260 mA cm-2 or 5-40 A g-1 – MnO2). |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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