Al2O3 Thin Films on Magnesium: Assessing the Impact of an Artificial Solid Electrolyte Interphase

Abstract

Among the many emerging technologies under investigation as alternatives to the successful Lithium-ion battery, the magnesium battery is promising due to the wide availability of magnesium, its high volumetric capacity, and the possibility for safety improvements. One of the largest challenges facing rechargeable magnesium batteries is the formation of a passivation layer at the Mg metal anode interface when reactive species in the electrolyte are reduced at the electrode-electrolyte interface. To control the solid electrolyte interphase in Lithium batteries, protective layers called artificial solid electrolyte interphase (ASEI) layers have been successful in improving Li metal anode performance. The approach of protecting Mg metal anodes from electrolyte degradation has been demonstrated by fewer studies in the literature than Li systems. In this work, we discuss the properties of Al2O3 thin films deposited using atomic layer deposition as an artificial solid electrolyte interphase at the Mg anode. Our results demonstrate that Al2O3 does prevent electrolyte degradation due to the reductive nature of Mg. However, undesirable properties such as defects and layer breakdown lead to Mg growth that causes soft-shorting. The soft-shorting occurs with and without the protection layer, indicating the ALD layer does not prevent it and hinders Al2O3 from being an ideal candidate for a protection layer. Crucial effects of this layer on Mg electrochemistry at the interface were observed, including growth of Mg deposits leading to soft-shorting of the cell whose morphology showed a dependence on the Al2O3 layer. These results may provide guidelines for the future design and development of protective ASEI layers for Mg anodes.

A Moisture‐Assisted Rechargeable Mg−CO2 Battery

“…[18] The XPS spectra of Mg 2p at 51.5 eV can be fit into the MgCO 3 part in MgCO 3 •3 H 2 O (Figure S11a). [19] These peaks decrease significantly after the charge process, indicating the disappearance of MgCO 3 •3 H 2 O. As shown in Figure 3c, there is a sharp peak at 1120 cm À 1 and a broad peak at about 3500 cm À 1 , which S2).…”

“…In O 1s spectra, the C−O bond at 532.6 eV as well as O−H band at 533.6 eV belongs to MgCO 3 ⋅3 H 2 O (Figure 3b) [18] . The XPS spectra of Mg 2p at 51.5 eV can be fit into the MgCO 3 part in MgCO 3 ⋅3 H 2 O (Figure S11a) [19] . These peaks decrease significantly after the charge process, indicating the disappearance of MgCO 3 ⋅3 H 2 O.…”

“…[17,18] Peaks at 51.5 eV in Mg 2p spectra are also remarkable at the discharged state (Figure S11b). [19] All the signals barely change after the charge process, which means the discharge product is difficult to decompose. Raman is conducted on the discharged CNT cathode in MCB-dry to confirm the presence of MgCO 3 with the appearance of CO 3…”

A Moisture‐Assisted Rechargeable Mg−CO2 Battery

“…The XPS results of the discharged products in MCB‐dry is obtained with a CO 3 2− peak at 290 eV in C 1s spectra (Figure 4a) and the appearance of a C−O band at 532.6 eV in O 1s spectra (Figure 4b), which associates with MgCO 3 [17, 18] . Peaks at 51.5 eV in Mg 2p spectra are also remarkable at the discharged state (Figure S11b) [19] . All the signals barely change after the charge process, which means the discharge product is difficult to decompose.…”

An Electrochemically Polymerized Protective Layer for a Magnesium Metal Anode

“…While much effort in the field of Mg batteries to battle these issues has been made to synthesize more complex Mg salts and create electrolytes that do not passivate the surface or reduce passivation, ,− in the last several years, even though still few in number, more studies have shown that Mg metal anodes can be successfully protected with artificial SEI (ASEI) layers or shed light on the prospective approaches that can greatly mitigate the passivation of the Mg surface but still allow the transport of Mg 2+ ions. − A few approaches to the formation of an ASEI have been investigated, such as utilizing electrolyte additives and preforming layers using controlled chemical reactions. For example, Li et al formed an MgI 2 protective layer by adding I 2 to the electrolyte .…”