Design of aqueous redox-enhanced electrochemical capacitors with high specific energies and slow self-discharge.

ABSTRACT: Electrochemical double-layer capacitors exhibit high power and long cycle life but have low specific energy compared with batteries, limiting applications. Redox-enhanced capacitors increase specific energy by using redox-active electrolytes that are oxidized at the positive electrode and reduced at the negative electrode during charging. Here we report characteristics of several redox electrolytes to illustrate operational/self-discharge mechanisms and the design rules for high performance. We discover a methyl viologen (MV)/bromide electrolyte that delivers a high specific energy of ∼14 Wh kg(-1) based on the mass of electrodes and electrolyte, without the use of an ion-selective membrane separator. Substituting heptyl viologen for MV increases stability, with no degradation over 20,000

SUBMITTER: Chun SE 

PROVIDER: S-EPMC4532795 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature