Improving Electrodeposition of Mg through an Open Circuit Potential Hold

Abstract

We used in situ X-ray diffraction, XPS, SEM, and electrochemical methods to interrogate the mechanism of Mg electrodeposition from PhMgCl/AlCl3 (APC) and EtMgCl electrolytes. An open circuit potential (OCP) pause following Mg deposition led to retained enhancement of Mg deposition and stripping kinetics along with lowered overpotentials for both. In situ X-ray diffraction demonstrated that the OCP pause led to a more polycrystalline deposit relative to that without the pause, while SEM presented micrographs that showed smaller deposits with an OCP hold. The improvement is attributed to an “enhancement layer” that formed on the electrode during the OCP hold. Analysis of XPS data suggests that the “enhancement layer” consists of Mg and Cl retained on the electrode surface, possibly following electrode depassivation.

A Review of Magnesium Aluminum Chloride Complex Electrolytes for Mg Batteries

“…[ 30,39 ] In magnesium organohaloaluminate electrolytes, the “enhancement layer” containing Cl − on Mg electrode can promote polycrystalline deposition and electron transfer at the electrode/solution interphase, facilitating the Mg deposition and dissolution. [ 40 ] In addition, Cl − also can affect the deposition of magnesium by changing the equilibrium of magnesium species. [ 12a,28 ] It was reported that the addition of a small amount of chloride ion can enhance the Mg deposition dissolution current density and the conductivity of MgCl 2 –Al Lewis acid electrolytes.…”

Advancing Electrolyte Solution Chemistry and Interfacial Electrochemistry of Divalent Metal Batteries

“…In another study, in situ XRD, XPS, SEM (scanning electron microscope), and electrochemical methods were used to interrogate the mechanism of Mg electrodeposition from PhMgCl/ AlCl 3 and EtMgCl electrolytes. [98] An open circuit potential (OCP) pause, following Mg deposition, enhanced Mg plating/stripping kinetics along with lowered overpotentials for both plating and stripping. The improvement is attributed to an "enhancement layer" that is formed on the electrode during the OCP hold, which consists of Mg and Cl on the electrode surface, possibly following electrode de-passivation.…”

“…In another study, in situ XRD, XPS, SEM (scanning electron microscope), and electrochemical methods were used to interrogate the mechanism of Mg electrodeposition from PhMgCl/AlCl 3 and EtMgCl electrolytes [98] . An open circuit potential (OCP) pause, following Mg deposition, enhanced Mg plating/stripping kinetics along with lowered overpotentials for both plating and stripping.…”

Magnesium underpotential deposition from nitrate melts and alloy formation with platinum substrate

“…Alloys obtained by overpotential electrochemical deposition (OPD) and UPD can have different chemical and phase structures from the alloys of the same composition obtained by metallurgical (thermal) methods [8,[20][21][22][23][24][25]. Recently, magnesium/platinum alloys formation by electrochemical means has been the subject of interest because of their applications in chemical power sources, jewelry and prosthetic aids [3,4,5,6,[26][27][28][29][30].…”