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Title: The role of ionic liquid electrolyte in an aluminum–graphite electrochemical cell

Abstract

Using first-principles calculations and molecular dynamics simulation, we study the working mechanism in an aluminum–graphite electrochemical cell, which was recently reported to exhibit attractive performance. We exclude the possibility of Al 3+ cation intercalation into graphite as in standard Li-ion batteries. Instead, we show that the AlCl 4 anion intercalation mechanism is thermodynamically feasible. By including the ionic liquid electrolyte in the overall redox reaction, we are able to reproduce the high voltage observed in experiment. The active involvement of electrolyte in the reaction suggests that the evaluation of energy density needs to take the electrolyte into consideration. Here, our proposed structural model is consistent with the new peaks appearing in X-ray diffraction from the intercalation compound. The high rate capability is explained by the ultralow diffusion barriers of the AlCl 4 intercalant. With the clarified working mechanism, it becomes clear that the high voltage of the Al–graphite cell is a result of the thermodynamic instability of the AlCl 4-intercalated graphite.

Authors:
 [1]; ORCiD logo [1];  [1]
  1. Rensselaer Polytechnic Institute, Troy, NY (United States)
Publication Date:
Research Org.:
Rensselaer Polytechnic Inst., Troy, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1344584
Alternate Identifier(s):
OSTI ID: 1347359
Grant/Contract Number:
SC0002623
Resource Type:
Journal Article: Published Article
Journal Name:
ACS Energy Letters
Additional Journal Information:
Journal Volume: 2; Journal Issue: 3; Journal ID: ISSN 2380-8195
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; 36 MATERIALS SCIENCE

Citation Formats

Agiorgousis, Michael L., Sun, Yi -Yang, and Zhang, Shengbai. The role of ionic liquid electrolyte in an aluminum–graphite electrochemical cell. United States: N. p., 2017. Web. doi:10.1021/acsenergylett.7b00110.
Agiorgousis, Michael L., Sun, Yi -Yang, & Zhang, Shengbai. The role of ionic liquid electrolyte in an aluminum–graphite electrochemical cell. United States. doi:10.1021/acsenergylett.7b00110.
Agiorgousis, Michael L., Sun, Yi -Yang, and Zhang, Shengbai. Fri . "The role of ionic liquid electrolyte in an aluminum–graphite electrochemical cell". United States. doi:10.1021/acsenergylett.7b00110.
@article{osti_1344584,
title = {The role of ionic liquid electrolyte in an aluminum–graphite electrochemical cell},
author = {Agiorgousis, Michael L. and Sun, Yi -Yang and Zhang, Shengbai},
abstractNote = {Using first-principles calculations and molecular dynamics simulation, we study the working mechanism in an aluminum–graphite electrochemical cell, which was recently reported to exhibit attractive performance. We exclude the possibility of Al3+ cation intercalation into graphite as in standard Li-ion batteries. Instead, we show that the AlCl4– anion intercalation mechanism is thermodynamically feasible. By including the ionic liquid electrolyte in the overall redox reaction, we are able to reproduce the high voltage observed in experiment. The active involvement of electrolyte in the reaction suggests that the evaluation of energy density needs to take the electrolyte into consideration. Here, our proposed structural model is consistent with the new peaks appearing in X-ray diffraction from the intercalation compound. The high rate capability is explained by the ultralow diffusion barriers of the AlCl4 intercalant. With the clarified working mechanism, it becomes clear that the high voltage of the Al–graphite cell is a result of the thermodynamic instability of the AlCl4-intercalated graphite.},
doi = {10.1021/acsenergylett.7b00110},
journal = {ACS Energy Letters},
number = 3,
volume = 2,
place = {United States},
year = {Fri Feb 17 00:00:00 EST 2017},
month = {Fri Feb 17 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1021/acsenergylett.7b00110

Citation Metrics:
Cited by: 3works
Citation information provided by
Web of Science

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  • Using first-principles calculations and molecular dynamics simulation, we study the working mechanism in an aluminum–graphite electrochemical cell, which was recently reported to exhibit attractive performance. We exclude the possibility of Al 3+ cation intercalation into graphite as in standard Li-ion batteries. Instead, we show that the AlCl 4 anion intercalation mechanism is thermodynamically feasible. By including the ionic liquid electrolyte in the overall redox reaction, we are able to reproduce the high voltage observed in experiment. The active involvement of electrolyte in the reaction suggests that the evaluation of energy density needs to take the electrolyte into consideration. Here,more » our proposed structural model is consistent with the new peaks appearing in X-ray diffraction from the intercalation compound. The high rate capability is explained by the ultralow diffusion barriers of the AlCl 4 intercalant. With the clarified working mechanism, it becomes clear that the high voltage of the Al–graphite cell is a result of the thermodynamic instability of the AlCl 4-intercalated graphite.« less
  • 2D titanium carbide (Ti 3C 2T x MXene) showed good capacitance in both organic and neat ionic liquid electrolytes, but its charge storage mechanism is still not fully understood. Here, electrochemical characteristics of Ti 3C 2T x electrode were studied in neat EMI-TFSI electrolyte. A capacitive behavior was observed within a large electrochemical potential range (from – 1.5 to 1.5 V vs. Ag). Intercalation and de-intercalation of EMI + cations and/or TFSI– anions were investigated by in-situ X-ray diffraction. Interlayer spacing of Ti 3C 2T x flakes decreases during positive polarization, which can be ascribed to either electrostatic attraction effectmore » between intercalated TFSI– anions and positively charged Ti 3C 2T x nanosheets or steric effect caused by de-intercalation of EMI + cations. In conclusion, the expansion of interlayer spacing when polarized to negative potentials is explained by steric effect of cation intercalation.« less
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  • We study a new ionic liquid (IL) based on a neutral ligand, 4-propylpyridine, is obtained via complexation with AlCl 3. It is found that the asymmetric cleavage of AlCl 3 generates AlCl 2+ and AlCl 4 , and the former is coordinated by 4-Pr-Py to produce the Al-containing cations ([AlCl 2(4-Pr-Py) 2] +). The AlCl 3/4-propylpyridine IL with a molar ratio of 1.3/1 is highly fluidic with a viscosity of 42.8 mPa s and an ionic conductivity of 5.0 x 10 -4 S/cm at room temperature. In contrast to conventional ILs for electroplating aluminum in which the electrochemically active speciesmore » are Al-containing anions (for example Al 2Cl 7 - ), this new IL has an Al-containing cation as the electroactive species, which is beneficial to electrodeposition of aluminum.« less