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標題: | 錳氧化物超高電容器之製備與分析 Synthesis and Characterization of Manganese Oxide Supercapacitors |
作者: | Kuang-Tsin Lee 李光正 |
指導教授: | 吳乃立 |
關鍵字: | 超高電容器,氧化錳,錳鐵氧化物,膠態電解質,X-ray 吸收光譜,超吸水性高分子, supercapacitor,manganese oxide,manganese ferrite,gel electrolyte,X-ray absorption spectrum,superabsorbent polymer, |
出版年 : | 2011 |
學位: | 博士 |
摘要: | 在本研究中,水系膠態電解質首次且成功地應用於氧化錳及錳鐵氧化物超高電容器。膠態電解質是由高分子、鹽類、及去離子水所組成。Potassium polyacrylic acid (PAAK)、共聚物potassium polyacrylic acid-co-polyacrylamide (PAAK-co-
PAAM)及polyacrylamide (PAAM)分別為膠態電解質中的高分子。這三種高分子電解質均未表現任何流動性,但其離子導電度均可維持在10-1 S cm-1。相較於使用一般液態電質,氧化錳及錳鐵化物超高電容器若使用這三種高分子電解質,其電容量均可獲得明顯的提昇。原位X-ray近場吸收光譜 (In-situ X-ray absorption near-edge structure, XANES)被用來觀察錳系氧化物超高電容器與膠態高分子的反應。從光譜分析中可發現在充放電過程中,相較於使用一般液態電解質;在高分子電解質中錳原子出現較明顯的化學變化。另一方面,對於超高電容器而言,由於電極的活性物(active material)無法全部接觸到電解液,使得電極單位面積提供的電容量,並不會因其單位面積重量增加而明顯提高。此問題嚴重限制了超高電容器能實際應用的發展。為了解決此一問題,超吸水性高分子polyacrylic acid (PAA)首先被嘗試應用於氧化錳超高電容器中。運用噴霧乾燥的技術,氧化錳、碳黑,PAA可形成全新之複合粒子。此複合粒子所組成之超高電容器,相較於由氧化錳、碳黑所組成的電極;除了表現出高電容量的特性,即使在高電流密度(5-40 A g-1 – MnO2)下充放電,仍能表現出高單位面積電容量的特性(1.8-1.4 F cm-2)。 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). |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/48203 |
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顯示於系所單位: | 化學工程學系 |
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