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 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. 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.

Halide‐Based Materials and Chemistry for Rechargeable Batteries

“…A further excellent study by Agiorgousis et al. demonstrated similar reaction mechanisms with regard to the fast intercalation and diffusion of AlCl 4 − and the high operating voltage of the Al‐graphite cell using the AlCl 3 /[EMIM]Cl electrolyte, according to the results of first‐principles calculations and molecular dynamics simulation . Similar reaction mechanisms for the graphite cathodes have also been proposed when the AlCl 3 /organic solvent eutectic electrolyte or inorganic AlCl 3 /alkali chloride eutectic electrolyte was used .…”

“…[283] Them inimum energy barrier of the AlCl 4 À cluster is about one order of magnitude lower than that of Li migration in graphite.I n addition, the tetrahedral AlCl 4 À cluster will distort and prefers to be in the form of ap lanar quadrangle when it is intercalated in bulk graphite, [284] in which the interlayer spacing was expanded from 3.35 to 6.02 .T his finding is consistent with the work of Dai et al [25] Af urther excellent study by Agiorgousis et al demonstrated similar reaction mechanisms with regard to the fast intercalation and diffusion of AlCl 4 À and the high operating voltage of the Al-graphite cell using the AlCl 3 /[EMIM]Cl electrolyte,a ccording to the results of first-principles calculations and molecular dynamics simulation. [285] Similar reaction mechanisms for the graphite cathodes have also been proposed when the AlCl 3 /organic solvent eutectic electrolyte or inorganic AlCl 3 /alkali chloride eutectic electrolyte was used. [213,238] Kravchyk et al used 27 Al NMR spectroscopy to directly reveal the AlCl 4 À intercalation in graphite.…”

Identification of Non‐Carbonaceous Cathodes in Al Batteries: Potential Applicability of Black and Blue Phosphorene Monolayers

“…[4][5][6][7][8][9][10] Now,w hen we talk about cathodes, numerous cathode materials have been examined for Al batteries, which can reversibly intercalate and deintercalate AlCl 4 À during charging and discharging reactions, respectively. [11][12][13][14][15][16][17][18][19] Experimentally,different studies have been executed for Al batteriesc athode by diversifying the graphite at structural level, such as naturalg raphite, [1,9] graphite foam, [20] graphitic carbon paper, [8] few layered graphene sheets, [21,22] polypyren [23] etc. These structural variations have definitely improved the overall performance of Al batteries in terms of increased voltage, higherc yclel ife and better storage.…”

Halogenid‐basierte Materialien und Chemie für wiederaufladbare Batterien

“…Eine weitere exzellente Arbeit von Agiorgousis et al. zeigte ähnliche Reaktionsmechanismen in Bezug auf die schnelle Interkalation und Diffusion von AlCl 4 − und die hohe Arbeitsspannung der Al‐Graphit‐Zelle mit dem AlCl 3 /[EMIM]Cl‐Elektrolyten, wie First‐Principles‐Rechnungen und Molekulardynamik‐Simluation ergaben . Vergleichbare Reaktionsmechanismen für die Graphitkathoden wurden auch vorgeschlagen, als AlCl 3 /organisches Lösungsmittel oder anorganisches AlCl 3 /Alkalimetallchlorid als eutektische Elektrolyte verwendet wurden .…”

“…Außerdem wird sich der vierflächige AlCl 4 À -Cluster verformen und ist in der Form eines flachen Vierecks,w enn es in Graphit interkaliert ist, [284] in welchem der Abstand der Zwischenschichten von 3.35 zu 6.02 expandiert wurde.D iese Feststellung ist konsistent zur Arbeit von Dai et al [25] Eine weitere exzellente Arbeit von Agiorgousis et al zeigte ähnliche Reaktionsmechanismen in Bezug auf die schnelle Interkalation und Diffusion von AlCl 4 À und die hohe Arbeitsspannung der Al-Graphit-Zelle mit dem AlCl 3 /[EMIM]Cl-Elektrolyten, wie First-Principles-Rechnungen und Molekulardynamik-Simluation ergaben. [285] Vergleichbare Reaktionsmechanismen fürd ie Graphitkathoden wurden auch vorgeschlagen, als AlCl 3 /organisches Lçsungsmittel oder anorganisches AlCl 3 /Alkalimetallchlorid als eutektische Elektrolyte verwendet wurden. [213,238] Kravchyk et al zeigten direkt die AlCl 4 À -Interkalation in Graphit mittels 27 Al-NMR-Spektroskopie.…”