Interfacial behavior of water-in-salt electrolytes at porous electrodes and its effect on supercapacitor performance
Interfacial behavior of water-in-salt electrolytes at porous electrodes and its effect on supercapacitor performance
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DOI：
10.1016/j.electacta.2019.134989
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发表时间：
2019-12-05
影响因子：
6.6
通讯作者：
Arava, Leela Mohana Reddy
中科院分区：
文献类型：
--
作者：
Mahankali, Kiran;Thangavel, Naresh Kumar;Arava, Leela Mohana Reddy
虽然盐包水（WIS）电解质为能量存储装置在水性条件下的操作提供了宽的潜在窗口，其可以提供高能量密度，但其高粘度和低离子电导率肯定限制了装置的速率性能。本文采用原位拉曼光谱和电化学阻抗谱（EIS）研究了WIS离子在不同多孔电极界面上的双电层行为和输运性质。原位拉曼分析表明，在活性炭电极（孔径> 30 nm）中，WIS电解质离子扩散到孔网络中，充电/放电电位决定了界面处的离子动力学。然而，这些离子在石墨烯电极（孔径< 3 nm）上经历吸附现象，从而促进在充放电期间离子的快速吸附。本文提出的EIS研究，详细的波特图分析阐明了超级电容器的电容，倍率性能对电极的性质和它们的孔径的依赖性。在典型的超级电容器电池中，具有WIS电解质的石墨烯电极在2.4 kW/kg的比功率下提供了55.3 Wh/kg的非常高的比能量，这是任何现有的WIS电解质报告所无法比拟的。目前的研究提供了实验见解离子存储和它们的动力学机制在界面形成的WIS电解质，这将有助于设计合适的电极材料。(C)2019爱思唯尔有限公司版权所有。
Though Water-in-salt (WIS) electrolytes offer a wide potential window for energy storage device operation in aqueous conditions that can deliver high energy density, their high viscosity and low ionic conductivity certainly limits the rate performance of the devices. Herein, we present electrical double layer behavior and nature of transportation of WIS ions at different porous electrode interfaces using in situ Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The in situ Raman analysis shows that, in activated carbon electrodes (pore size > 30 nm), the WIS electrolyte ions diffuse into the pore network and charge/discharge potential dictates the ion dynamics at the interface. Whereas, these ions undergo adsorption phenomena on graphene electrodes (pore size < 3 nm), thus facilitating rapid sorption of ions during charge-discharge. EIS study presented herein, with detailed bode plot analysis elucidates the dependence of capacitance, rate capability of the supercapacitor on the nature of electrodes and their pore size. In a typical supercapacitor cell, graphene electrodes with WIS electrolyte delivered a very high specific energy of 55.3 Wh/kg at a specific power of 2.4 kW/kg, unparalleled to any of the existing WIS electrolyte reports. The current studies provide experimental insights into ion storage and their dynamic mechanism at the interface formed by WIS electrolytes that will assist in designing of suitable electrode materials. (C) 2019 Elsevier Ltd. All rights reserved.