TY - JOUR
T1 - High energy density aqueous electrochemical capacitors with a KI-KOH electrolyte
AU - Wang, Xingfeng
AU - Chandrabose, Raghu S.
AU - Chun, Sang Eun
AU - Zhang, Tianqi
AU - Evanko, Brian
AU - Jian, Zelang
AU - Boettcher, Shannon W.
AU - Stucky, Galen D.
AU - Ji, Xiulei
N1 - Publisher Copyright:
© 2015 American Chemical Society.
PY - 2015/9/16
Y1 - 2015/9/16
N2 - We report a new electrochemical capacitor with an aqueous KI-KOH electrolyte that exhibits a higher specific energy and power than the state-of-the-art nonaqueous electrochemical capacitors. In addition to electrical double layer capacitance, redox reactions in this device contribute to charge storage at both positive and negative electrodes via a catholyte of IOx-/I- couple and a redox couple of H2O/Had, respectively. Here, we, for the first time, report utilizing IOx-/I- redox couple for the positive electrode, which pins the positive electrode potential to be 0.4-0.5 V vs Ag/AgCl. With the positive electrode potential pinned, we can polarize the cell to 1.6 V without breaking down the aqueous electrolyte so that the negative electrode potential could reach -1.1 V vs Ag/AgCl in the basic electrolyte, greatly enhancing energy storage. Both mass spectroscopy and Raman spectrometry confirm the formation of IO3- ions (+5) from I- (-1) after charging. Based on the total mass of electrodes and electrolyte in a practically relevant cell configuration, the device exhibits a maximum specific energy of 7.1 Wh/kg, operates between -20 and 50 °C, provides a maximum specific power of 6222 W/kg, and has a stable cycling life with 93% retention of the peak specific energy after 14 000 cycles.
AB - We report a new electrochemical capacitor with an aqueous KI-KOH electrolyte that exhibits a higher specific energy and power than the state-of-the-art nonaqueous electrochemical capacitors. In addition to electrical double layer capacitance, redox reactions in this device contribute to charge storage at both positive and negative electrodes via a catholyte of IOx-/I- couple and a redox couple of H2O/Had, respectively. Here, we, for the first time, report utilizing IOx-/I- redox couple for the positive electrode, which pins the positive electrode potential to be 0.4-0.5 V vs Ag/AgCl. With the positive electrode potential pinned, we can polarize the cell to 1.6 V without breaking down the aqueous electrolyte so that the negative electrode potential could reach -1.1 V vs Ag/AgCl in the basic electrolyte, greatly enhancing energy storage. Both mass spectroscopy and Raman spectrometry confirm the formation of IO3- ions (+5) from I- (-1) after charging. Based on the total mass of electrodes and electrolyte in a practically relevant cell configuration, the device exhibits a maximum specific energy of 7.1 Wh/kg, operates between -20 and 50 °C, provides a maximum specific power of 6222 W/kg, and has a stable cycling life with 93% retention of the peak specific energy after 14 000 cycles.
KW - KI and KOH mixture
KW - aqueous electrochemical capacitor
KW - high energy
KW - high power
KW - iodate
KW - redox electrolyte
UR - http://www.scopus.com/inward/record.url?scp=84941769646&partnerID=8YFLogxK
U2 - 10.1021/acsami.5b04677
DO - 10.1021/acsami.5b04677
M3 - Article
AN - SCOPUS:84941769646
SN - 1944-8244
VL - 7
SP - 19978
EP - 19985
JO - ACS applied materials & interfaces
JF - ACS applied materials & interfaces
IS - 36
ER -