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Electric Double‐Layer Capacitors Based on Non‐Aqueous Electrolytes: A Comparative Study of Potassium and Quaternary Ammonium Salts
Author(s) -
Uchida Satoshi,
Masese Titus
Publication year - 2020
Publication title -
batteries and supercaps
Language(s) - English
Resource type - Journals
ISSN - 2566-6223
DOI - 10.1002/batt.201900226
Subject(s) - electrolyte , inorganic chemistry , propylene carbonate , ionic conductivity , chemistry , supercapacitor , salt (chemistry) , conductivity , chemical engineering , aqueous solution , materials science , electrochemistry , electrode , organic chemistry , engineering
Abstract 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 (KPF 6 ) and commercial triethylmethy‐lammonium tetra‐fluoroborate (TEMABF 4 ) salts in EDLCs. Compared to commercial TEMABF 4 ‐based electrolytes, KPF 6 salt‐based electrolytes (in acetonitrile solvent) demonstrate outstanding rate performance. The KPF 6 salt‐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.