Electric Double‐Layer Capacitors Based on Non‐Aqueous Electrolytes: A Comparative Study of Potassium and Quaternary Ammonium Salts
Electric Double‐Layer Capacitors Based on Non‐Aqueous Electrolytes: A Comparative Study of Potassium and Quaternary Ammonium Salts
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DOI：
10.1002/batt.201900226
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发表时间：
2020-05
期刊：
影响因子：
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通讯作者：
S. Uchida;T. Masese
中科院分区：
文献类型：
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作者：
S. Uchida;T. Masese
由于其超快的充放电速率和较长的循环寿命，双电层电容器(EDLC)作为一种可行的间歇储能方案已经引起了人们的极大关注。然而，传统的非质子有机电解液固有的较高的离子电导活化能大大阻碍了高性能EDLCs的可行性。在此，我们考察和比较了基于六氟磷酸钾(KPF6)和商用三乙基甲基四氟硼酸铵(TEMABF4)盐的电解液在EDLC中的物理化学性质和性能。与商用TEMABF4电解液相比，KPF6盐基电解液(在乙腈溶剂中)表现出优异的倍率性能。KPF6盐基电解液还表现出较低的活性炭孔内离子电阻以及电极和电解液之间的较低界面电阻，这不是对高离子电导率的肯定，而是对低活化能的突出。较低的活化能可以归因于K+离子的低有效核电荷，这使得阴离子在溶剂态下容易横向移动。这项研究不仅为钾离子(K+)作为快速电荷载体奠定了基础，也为基于单价碱性阳离子的下一代非水电力设备提供了一种可行的解决方案。
Immense attention has been drawn towards electric double layer capacitors (EDLCs) as a viable intermittent energy storage solution, owing to their ultra‐fast charge/discharge rates and long cycle life. However, the high activation energy of ionic conductivity innate in conventional aprotic organic electrolytes has greatly impeded the feasibility of high‐performance EDLCs. Herein, we investigate and compare the physicochemical properties and performance of electrolytes based on potassium hexafluorophosphate (KPF6) and commercial triethylmethy‐lammonium tetra‐fluoroborate (TEMABF4) salts in EDLCs. Compared to commercial TEMABF4‐based electrolytes, KPF6salt‐based electrolytes (in acetonitrile solvent) demonstrate outstanding rate performance. The KPF6salt‐based electrolyte further manifests lower ionic resistance within activated carbon pores as well as lower interfacial resistance between electrode and electrolyte; an affirmation of not the high ionic conductivity but rather the eminence of low activation energy. The low activation energy can be attributed to the low effective nuclear charge of the K+cations that allow anions to transverse easily in solvent state. This study not only underpins potassium‐ion (K+) as a fast charge carrier, but also a viable solution for the next‐generation non‐aqueous power devices relying on monovalent alkali cations.