Protective Al 2 O 3 Thin Film Coating by ALD to Enhance the Anodic Stability of Metallic Current Collectors in Ethereal Mg Electrolyte Solutions

Rechargeable magnesium batteries (RMBs) have the potential to contribute towards alternative energy storage due to their low cost, high abundance, dendrites free deposition of Mg and high volumetric energy density. Organometallic complex-based electrolytes in ethereal solutions have been extensively studied in the context of RMBs due to their ability to facilitate highly reversible magnesium deposition in rechargeable magnesium batteries, while demonstrating wide enough electrochemical stability windows. However, these solutions containing unique mixture of organo-halo aluminate complexes have detrimental effect on the anodic stability of metallic current collectors for cathodes, like Ni and Al foils. In this work, we were able to synthesize and isolate Mg 2 Cl 3 (THF) 6 Ph 2 AlCl 2 /THF electrolyte as the sole electroactive species using simple precursors: Ph 2 AlCl and MgCl 2 in THF, via atom efficient mono-chloro abstraction Schlenk technique. We characterized the anodic stability of Ni, Ni@C, Al, and Al@C current collectors by monitoring their electrochemical behavior. In addition, we investigated the anodic stability enhancement of various current collectors by Al 2 O 3 thin films coating using Atomic Layer Deposition (ALD). Linear sweep voltametric studies showed that coating current collectors enhanced the oxidative stability of Al and Ni foils by 0.1–0.3 V vs Mg/Mg 2+ compared to the uncoated foils. In particular, Al 2 O 3 coated Al@C showed an improved oxidative stability of 2.8 V vs Mg/Mg 2+ . Our findings show that current collectors protection by ALD coating can help in long-term stability and improving RMBs’ energy density by using high voltage cathode materials, a crucial step in developing practical rechargeable Mg batteries. We succeeded in synthesis and isolation of complex APC type electrolyte solutions. Mg 2 Cl 3 (THF) 6 Ph 2 AlCl 2 /THF—electrolyte (1) as the sole electroactive species. Investigation of anodic stability of various metallic current collectors foils. Atomic layer deposition of thin layer Al 2 O 3 for current collector protection in RMBs.