Reversible Deposition and Dissolution of Mg Negative in Non-Ethereal Electrolyte
In this study, we propose a new electrolyte system for reversible deposition and dissolution of Mg. The electrolyte we use here is composed of Mg2+ and I- electrolytic ions and non-ethereal solvent. Nevertheless, it is quite difficult to prepare that electrolyte due to the lack of solubility of Magnesium iodide in the non-ethereal solvent. To overcome this difficulty, we take an alternative method; the electrolyte was synthesized in the solvent. Several electrochemical properties of this electrolyte are evaluated. The obtained result exhibited that the reversible magnesium deposition and dissolution was successfully achieved. We expect that this electrolyte could be a candidate for rechargeable Mg battery as non-ethereal electrolyte.
The electrochemical measurements were carried out on two-electrode type cell (HS cell, Hohsen Corp.); this cell is a basically coin-type cell with minimum volume of electrolyte and can be used repeatedly. Ni disk with 13 mmφ and disc-shaped Mg metal with 13 mmφ were used as a working electrode and counter electrode respectively.
Fig. 1 shows cyclic voltammogram at first cycle of Mg deposition and dissolution on Ni plate in the Mg-ion electrolyte. It is clearly observed that the typical anodic and cathodic current peaks of metal deposition-dissolution which related to the electrodeposition of Mg on Ni plate. The value of anodic and cathodic peaks over 1.5 A cm-2. This large current peaks must be derived from using HS cell; distance between the working electrode and the counter electrode is very short compared to beaker cell, thus, it helps to maintain adequate amount of Mg ion near the working electrode. Although the separator made of polyolefin exist between the working and counter electrodes, it do not hinder the reversible deposition and dissolution of Mg. Note that linear response in the anodic sweep was clearly observed even at room temperature, indicating that no overvoltage is necessary for dissolution of Mg on Ni plate. This results suggest that the Mg-ion electrolyte could be a promising candidate for rechargeable Mg battery.
Fig. 1 Cyclic voltammogram of Mg deposition and dissolution on Ni substrate in Mg-ion electrolyte at scan rate of 20 mV s-1.
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