Electrolytes for hybrid carbon–MnO2 electrochemical capacitors

✍ Scribed by H.A. Mosqueda; O. Crosnier; L. Athouël; Y. Dandeville; Y. Scudeller; Ph. Guillemet; D.M. Schleich; T. Brousse

• Book ID: 103828118
• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 307 KB
• Volume: 55
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/j.electacta.2010.01.022

✦ Synopsis

Different aqueous-based electrolytes have been tested in order to improve the electrochemical performance of hybrid (asymmetric) carbon/MnO 2 electrochemical capacitor (EC). Chloride and bromide aqueous solutions lead to the formation of Cl 2 and Br 2 respectively upon oxidation of the corresponding salt, thus limiting the useful electrochemical window of the MnO 2 electrode and producing gas evolution (in the case of chloride salts) detrimental to the cycling ability of an hybrid device. For sulfate and nitrate salts, MnO 2 electrode exhibits a 20% increase in capacitance when lithium is used as the cation compared to sodium or potassium salts, probably due to partial lithium intercalation in the tunnels of ␣-MnO 2 structure. The higher ionic conductivity and solubility of LiNO 3 has led to the investigation of this electrolyte in carbon/MnO 2 supercapacitor compared to standard hybrid cell using K 2 SO 4 . A lower resistance increase was evidenced when the temperature was decreased down to -10 • C. Long term cycling ability of carbon/MnO 2 supercapacitor was also evidenced with 5 M LiNO 3 electrolyte.