High Energy Density Aqueous Electrochemical Capacitors with a KI-KOH Electrolyte

详细信息    查看全文

• 作者：Xingfeng Wang ; Raghu S. Chandrabose ; Sang-Eun Chun ; Tianqi Zhang ; Brian Evanko ; Zelang Jian ; Shannon W. Boettcher ; Galen D. Stucky ; Xiulei Ji
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：September 16, 2015
• 年：2015
• 卷：7
• 期：36
• 页码：19978-19985
• 全文大小：499K
• ISSN：1944-8252

文摘

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 IO_x^{鈥?/sup>/I鈥?/sup> couple and a redox couple of H₂O/H_ad, respectively. Here, we, for the first time, report utilizing IO_x鈥?/sup>/I鈥?/sup> redox couple for the positive electrode, which pins the positive electrode potential to be 0.4鈥?.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 鈭?.1 V vs Ag/AgCl in the basic electrolyte, greatly enhancing energy storage. Both mass spectroscopy and Raman spectrometry confirm the formation of IO₃鈥?/sup> ions (+5) from I鈥?/sup> (鈭?) 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 鈭?0 and 50 掳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鈥?00 cycles.}