Non-aqueous electrochemical capacitor utilizing electrolytic redox reactions of bromide species in ionic liquid

• Published in: Electrochimica acta Vol. 86; pp. 294 - 297
• Main Authors: Yamazaki, Shigeaki, Ito, Tatsuya, Yamagata, Masaki, Ishikawa, Masashi
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier Ltd 30-12-2012; Elsevier
• Subjects: Activated carbon; Applied sciences; Bromides; Capacitance; Capacitors; Capacitors. Resistors. Filters; Chemistry; Cloth; Diffusion; Electrical engineering. Electrical power engineering; Electrochemical capacitor; Electrochemistry; Electrodes; Electrolytes; Electrolytic cells; Exact sciences and technology; General and physical chemistry; Hybrid capacitor; Non-aqueous electrolyte; Redox capacitor; Various equipment and components; Redox capacitor; Non-aqueous electrolyte; Hybrid capacitor; Electrochemical capacitor; Activated carbon; Oxidation reduction; Inorganic anion; Bromides; Electrolytic capacitor; Electrochemical reaction; Non aqueous solvent; Ionic liquid
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2012.01.031

We propose a novel electrochemical capacitor (EC) utilizing an “electrolytic” charge-storage system of bromide species. The present EC cell is fabricated with 1.0moldm−3 1-ethyl-3-methylimidazolium bromide dissolved in 1-ethyl-3-methylimidazolium tetrafluoroborate as an electrolyte and activated carbon fiber cloths (ACFCs) as electrodes. Although such a charge-storage concept would usually be useless due to inevitable, undesirable reactions, e.g. shuttle reaction or migration of active redox species between electrodes, we attain much-enhanced capacitance with an excellent reversibility by suppressing an undesirable diffusion process. In fact, the coulombic efficiency of the present cell is over 99.7% at 100mAg−1. The oxidation species such as Br2 or Br3− as charge accumulators do not diffuse from a positive electrode into the electrolyte. Moreover, the present EC cell has an excellent cycleability of at least 10,000 cycles.