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

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:
Grant/Contract Number:
SC0002623
Type:
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)
Research Org:
Rensselaer Polytechnic Inst., Troy, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; 36 MATERIALS SCIENCE
OSTI Identifier:
1344584
Alternate Identifier(s):
OSTI ID: 1347359