四氧化三鐵/碳材超高電容器之特性與機制探討

Characterization and Mechanism of Fe3O4/Carbon Supercapacitors

王世育(Shi-Yu Wang)

指導教授 ： 吳乃立

國立臺灣大學/工學院/化學工程學研究所/博士(2004年)

https://doi.org/10.6342/NTU.2004.00388

摘要

包含一非導電性之高比表面積(1436 m2/g)活性碳和一導電性之低比表面積(220 m2/g)碳黑(CB)所形成的複合電極，觀察此複合電極在KOH和Na2SO4電解液的電容行為，無論是那種電解液，最大的電容值均發生於導電的CB組成在所對應的穿透門檻上，在CB含量小於這門檻時，其電容值主要受限於電極本身的電阻；當CB含量大於此門檻後，其比表面積將是影響電容值的最大因素。在1 M KOH(aq)且掃瞄速率為20 mV/s下，有最大的電容值(108 F/g)發生，而此CB的含量在25 wt.%(或體積分率~ 14 vol.%)。
探討Fe3O4超高電容器於不同電解液中的操作特性，其中包含了Na2SO3、KOH與Na2SO4三種電解液之電容值、漏電流、操作電壓的範圍、循環次數的穩定性及自放電的行為。從實驗中可知，氧化鐵的電容量與電解液的成分有很大的關係，尤其在Na2SO3(aq)有最高的電容表現30 F/g-Fe3O4或表面積下之80

關鍵字

氧化鐵 ； 超高電容器 ； 碳 ； 電化學石英晶體微量天平 ； 機制

並列摘要

Composite electrodes which comprise a non-conductive activated carbon of large surface area (1436 m2/g) and a conductive carbon black (CB) of small surface area (220 m2/g) have been prepared and studied for their capacitive properties in aqueous KOH and Na2SO4 electrolytes. For either electrolyte, maximum capacitance exists at the composition believed to correspond to the percolation threshold for CB, the conductive phase. At a CB content less than the threshold, the capacitance is limited mainly by the electronic resistance on the electrode side. The interfacial surface area becomes the limiting factor as the threshold is exceeded. A maximum capacitance of 108 F/g at a voltage sweep rate of 20 mV/s is obtained in 1 M KOH aqueous electrolyte with a CB content of 25 wt.% (or ~ 14 vol.%).
Magnetite (Fe3O4) supercapacitor contained 10 wt.% CB as conductive additive (≧ percolation threshold), operating characteristics in aqueous electrolytes of Na2SO3, KOH and Na2SO4 were investigated. While the capacitance of the oxide was found to depend heavily on electrolyte composition, the self-discharge mechanism in these electrolytes appeared to be the same. Reduction in dissolved oxygen content (DOC) of electrolyte reduced leakage current and profoundly improved the cycling stability. In particular, Na2SO3(aq) gives the highest capacitance, nearly 30 F/g-Fe3O4 or 80

並列關鍵字

Carbon ； Mechanism ； Fe3O4, EQCM ； Supercapacitor

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