Mg deposition is reversible

6 On solutions with a wide electrochemical window ( 2V) in which magnesium (Mg) deposition is reversible 

Over the years, some group have succeeded in developing electrolyte systems of wider electrochemical windows, based on Mg boranes [33] or magnesium silicon complexes in ethers [34]. For instance, solutions of Mg(BPh2Bu2)2 in THF (Ph and Bu are phenyl and butyl groups) could provide an electrochemical window close to 1.8V, whereas Mg electrodes may behave reversibly in them [33]. There were attempts to study and develop Mg insertion materials [33,35] in a similar manner to that of the intensive and successful R D efforts related to positive electrodes for Li batteries. 

9 Comparison of typical steady state voltammograms of THF solutions with Pt electrodes, from which magnesium can be reversibly deposited. Note the reversible response of Mg deposition and dissolution and the difference in the anodic stability of the four solutions. The composition of the four solutions measured is indicated herein (near the V curves). 

The Lewis acid/Lewis base ratio determines the type of Mg crystallites that are deposited. At low and high acid/base ratios (e.g. 0.5, 3), Mg deposition is a submicronic-nanonic phenomenon at a wide distribution of crystal size, while at moderate A/B ratios (1, and 2), Mg is deposited in micrometer-size crystallites. Another important factor that determines the morphology of Mg deposition is the current density. The higher current density, the smaller is the crystallite size. Thus, while at moderate current densities (1-2 mA/ cm ). Mg deposition is a micrometric phenomenon, while at higher current densities (e.g. 4mA/cm ), Mg is deposited in nanometer-size crystallites. 

70 The effect of the MgR2/AICl2R ratio in the complex ether (THF) solutions on the anodic stability of the solutions. The main species formed and the oxidation potentials of the various anions that can be formed in these solutions, are indicated herein. 

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