Seminar
Date | 2016-11-15 |
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■ Topic : Understanding
the electrochemical storage mechanism in supercapacitors
■ Speaker : 11/14(Tue) Prof. Sangeun Chun (Dept. of MSE, Kyungpook National Univ.)
■ Invitation : Prof. Yoon Sung Nam
■ Date & Time : November 15 (Tue) 16:00
■ Venue : KAIST Applied Engineering B/D(W1), Multimedia Lecture Hall (1st Floor)
■ 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 cycles. Self-discharge is low, due to adsorption of the redox
couples in the charged state to the activated carbon, and comparable to cells
with inert electrolyte. An electrochemical model reproduces experiments and
predicts that 30–50 Wh
kg-1 is possible with optimization.