A Sobering Examination of the Feasibility of Aqueous Aluminum Batteries

Schematic of the solvation environment of 3.6m Al(OTf)3-H2O and parasitic mechanisms, including: (a) proton activity, (b) octahedral coordination of H2O and transient OH- to Al3+, (c) hydrogen evolution, (d) corrosion, and (e) a lack of solid electrolyte interphase formation.

Scientific Achievement

We revealed the first compelling evidence for a dynamic octahedral solvation structure around Al3+ dominated by labile water and OH-, without Al-OTf contact ion pairs, at high salt concentrations. High proton activity is observed in transport and electrochemical measurements which relates well with the proposed solvation environment.


We also exposed practical concerns related to (i) the corrosiveness of the acidic aqueous solutions, (ii) the degree of hydration of Al(OTf)3 salt, and (iii) the grossly insufficient reductive stability (>1 V between HER onset and Al3+/Al). Collectively, these factors constitute multiple fundamental barriers to the feasibility of rechargeable aqueous Al batteries.


  • Glenn Pastel (ARL): Electrochemistry/Physicochemical
  • Ying Chen (PNNL): Liquid & solid-state NMR
  • Travis Pollard (ARL): Born-Oppenheimer molecular dynamics simulations
  • Allen Zheng (Hunter College): PFG-NMR (diffusivity)
  • Nathan Hahn (Sandia): Dielectric Relaxation Spectroscopy

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DOI: 10.1039/D2EE00134A

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