| 摘要: | 本研究以化學還原法作為基礎，第一次成功的利用超臨界二氧化碳製程技術製備氧化錳之超高電容器電極材料，並藉由調變壓力、溫度、時間等參數及添加石墨烯與離子液體等方式進而提升其電容行為。 實驗結果指出，利用超臨界二氧化碳製程所合成出之氧化錳顆粒較一般常壓大氣製程來的小顆，並且因為與電解液接觸面積大，電容性質較佳，其不同速率下之維持率(C500/C50)(以CV法計算出500 mV/s比電容值(C500)與50 mV/s 比電容值(C50)之比值)為0.69，其值較常壓大氣方法(C500/C50=0.59)來的高。因為氧化錳自身導電性較低，本實驗以添加不同碳材(奈米碳管與石墨烯)降低氧化錳的團聚現象進而提升氧化錳的導電性。相較於傳統常壓製程，利用超臨界流體所合成之氧化錳/石墨烯複合材不僅可因此製程均勻地將氧化錳分散於石墨烯上，還可利用超臨界流體之高滲透特性撐開石墨層間距使石墨烯使用效率提升，故以超臨界流體於氧化錳中添加石墨烯之電容增益效果(120%)將會比傳統常壓下氧化錳添加石墨烯之電容增益(108%)來的高，其不同速率下之維持率C500/C50可達0.78。最後，將此氧化錳/石墨烯複合材與離子液體(EMI-NTf2)做結合，因離子液體可填補複合材間空隙位置而提升電流傳遞路徑，將更進一步的提升其電容行為，其電容維持率(C500/C50)甚至可達0.86，而若對此電極進行10,000次500 mV/s 之CV循環壽命測試後，仍可擁有98.3 % 之電容維持率。並且在進行壽命測試後其功率密度將可明顯提升。In this study, we successfully used supercritical carbon dioxide (ScCO2) method to synthesis manganese oxide as supercapacitor electrode material. Herein, pressure, temperature and reaction time were investigated to enhance capacitance as well as combination of graphene and ionic liquid aim to improve their performance.The result showed, synthesis manganese oxide by using supercritical carbon dioxide technique can get smaller manganese oxide powder than using ambient method, then will have higher interface between powder and electrolyte, the capacitance will be higher, and the different rate retention (C500/C50) (calculate by CV test using 500 mV/s capacitance divide 50 mV/s capacitance) exhibit at 0.69, is higher than ambient method (0.59). But manganese oxide has poor intrinsic conductivity, in this study, we also add different carbonaceous materials (CNT or graphene) to decrease MnO2 aggregation condition to improve manganese oxide conductivity. Compare with traditional ambient method, using ScCO2 method synthesis manganese oxide/graphene not only make MnO2 disperse well on graphene but also increase distance between graphene layers that enhance graphene accessible surface areas, so add graphene with MnO2 by using ScCO2 method will better than using Ambient method, and the different rate retention up to 0.78.Finally, we combined ionic liquid (EMI-NTf2) with this MnO2/graphene composite, because ionic liquid can be full filled interval between MnO2/graphene composite, then make electrons has more pathway to transfer, obtained capacitance higher again, and the different rate retention reached up to 0.86, Besides, the cycle life after 500 mV/s CV test 10,000 times still maintain at 98.3 % and have higher power in compare with initial behaviors. |
