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In Operando Calorimetric Measurements for Activated Carbon Electrodes in Ionic Liquid Electrolytes under Large Potential Windows
Author(s) -
Munteshari Obaidallah,
Borenstein Arie,
DeBlock Ryan H.,
Lau Jonathan,
Whang Grace,
Zhou Yucheng,
Likitchatchawankun Ampol,
Kaner Richard B.,
Dunn Bruce,
Pilon Laurent
Publication year - 2020
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201903011
Subject(s) - electrolyte , endothermic process , ionic liquid , electrode , propylene carbonate , chemistry , activated carbon , inorganic chemistry , analytical chemistry (journal) , electrochemical window , heat generation , materials science , chemical engineering , ionic conductivity , thermodynamics , organic chemistry , physics , adsorption , engineering , catalysis
This study aims to investigate the effect of the potential window on heat generation in carbon‐based electrical double layer capacitors (EDLCs) with ionic‐liquid (IL)‐based electrolytes using in operando calorimetry. The EDLCs consisted of two identical activated‐carbon electrodes with either neat 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethane‐sulfonyl)imide ([Pyr 14 ][TFSI]) electrolyte or 1.0 m [Pyr 14 ][TFSI] in propylene carbonate (PC) as electrolyte. The instantaneous heat generation rate at each electrode was measured under galvanostatic cycling for different potential windows ranging from 1 to 4 V. First, the heat generation rates at the positive and negative electrodes differed significantly in neat IL owing to the differences in the ion sizes and diffusion coefficients. However, these differences were minimized when the IL was diluted in PC. Second, for EDLC in neat [Pyr 14 ][TFSI] at high potential window (4 V), a pronounced endothermic peak was observed at the beginning of the charging step at the positive electrode owing to TFSI − intercalation in the activated carbon. On the other hand, for EDLC in 1.0 m [Pyr 14 ][TFSI] in PC at potential window above 3 V, an endothermic peak was observed only at the negative electrode owing to the decomposition of PC. Third, for both neat and diluted [Pyr 14 ][TFSI] electrolytes, the irreversible heat generation rate increased with increasing potential window and exceeded Joule heating. This was attributed to the effect of potential‐dependent charge redistribution resistance. A further increase in the irreversible heat generation rate was observed for the largest potential windows owing to the degradation of the PC solvent. Finally, for both types of electrolyte, the reversible heat generation rate increased with increasing potential window because of the increase in the amount of ion adsorbed/desorbed at the electrode/electrolyte interface.