| dc.description.abstract | 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.
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