Bismuth oxide coated amorphous manganese dioxide for electrochemical capacitors |
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| Institution: | 1. College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, 333 Longteng Road, Shanghai 201620, PR China;2. Department of Chemistry, University of Science and Technology of China, Hefei 230026, PR China;3. Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221-0172, USA;1. CLASSE, Cornell University, Ithaca, NY, USA;2. Department of Physics, Harvard University, Cambridge, MA, USA;3. Tech-X Corporation, Boulder, CO, USA;1. Department of Physics, College of Science, Taibah University, Medina, 41411, Saudi Arabia;2. Department of Physics and Mathematical Engineering, Higher Institute of Engineering and Technology, 5th Settlement, 11835, Cairo, Egypt;1. CLASSE, Cornell University, Ithaca, NY 14853, United States;2. Carnegie Mellon University, Pittsburgh, PA 15213, United States;3. Gordon College, Wenham, MA 01984, United States;4. Columbia University, New York, NY 10027, United States;5. LBNL, Berkeley, CA 94720, United States;6. Idaho State University, Pocatello, ID 83209, United States |
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| Abstract: | With MnSO4, NaOH and K2S2O8 as the raw materials, the amorphous and δ-type manganese dioxide (MnO2) is separately prepared by using different chemical precipitation-oxidation methods. The results of charge–discharge and electrochemical impedance spectroscopy (EIS) tests show that (i) the specific capacitance of the amorphous MnO2 reaches to 301.2 F g−1 at a current density of 200 mA g−1 and its capacitance retention rate after 2000 cycles is 97%, which is obviously higher than 250.8 F g−1 and 71% of the δ-type one, respectively; (ii) good electrochemical capacitance properties of the amorphous MnO2 should be contributed to easy insertion/extraction of ions within the material; (iii) when 5 wt% Bi2O3 is coated on the amorphous MnO2, its specific capacitance increases to 352.8 F g−1 and the capacitance retention rate is 90% after 2000 cycles. |
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| Keywords: | Amorphous manganese dioxide Bismuth oxide Coating Electrochemical capacitance |
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