Ionic Liquid Encapsulated Poly (Methyl Methacrylate) Electrolyte Film in Electrical Double Layer Capacitor

Abstract

One of the main components of electrical double layer capacitor (EDLC) is the electrolyte. Gel-type electrolyte has shown good performance in EDLC. However, not much information is available on film-type electrolytes, which are known to provide better mechanical stability than the gel-type electrolyte. In present study, we have reported the performance of film-type poly(methyl methacrylate (PMMA) as electrolyte in electrical double layer capacitor (EDLC) systems and compared with the gel-type PMMA electrolytes. This film-type PMMA electrolyte is modified by encapsulating 1-methyl-3-pentamethyldisiloxymethylimidazolium bis (trifluoromethylsulfonyl)imide, [(SiOSi)C1C1 im][NTf2 ], an ionic liquid (IL), into the PMMA matrix, PMMAIL. Doping this PMMAIL film with 30% lithium triflate salt (LiTf), LiTfPMMAIL, provides an EDLC cell with higher breakdown voltage (3.2 V) and higher specific discharge capacity (Csp) (6.59 Fg-1 ) and energy density (0.92 Whkg-1 ) than the selected PMMA-based gel electrolyte systems. These values exceed the minimum requirements for a working supercapacitor. However, this LiTF-PMMAIL cell exhibited lower power density (23.04 Wkg-1 ) than the selected EDLC cells due to the more congested system of LiTF-PMMAIL. Thus, the performance of this LiTF-PMMAIL cell could be improved by adjusting the amount of doping salt and using different types of carbon electrodes. Keywords—capacitors, charging/discharging, polymer electrolyte films, poly (methyl methacrylate) electrolytes, solid electrolytes.